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Mutant Transcription Factors and Tyrosine Kinases as Therapeutic Targets for Leukemias: From Acute Promyelocytic Leukemia to Chronic Myeloid Leukemia and Beyond
Abstract
Mutations in transcription factors (TFs) and protein tyrosine kinases (PTKs), which result in inhibition of differentiation/apoptosis or enhanced proliferative/survival advantage of hematopoietic stem/progenitor cells, are two classes of the most frequently detected genetic abnormalities in leukemias. The critical roles for mutant TFs and/or PTKs to play in leukemogenesis, and the absence of mutant TFs/PTKs in normal hematopoietic cells, suggest that the two types of aberrant molecules may serve as ideal therapeutic targets. The great success of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) in treating acute promyelocytic leukemia through modulation of the causative PML-RARalpha oncoprotein represents the first two paradigms of mutant TFs-targeting therapeutic strategies for leukemia. More recently, tyrosine kinase inhibitor STI-571/Imatinib mesylate/Gleevec in the treatment of Breakpoint Cluster Region-Abelson (BCR-ABL) positive leukemia elicits paradigm of mutant PTKs as ideal antileukemia targets. Thus to further improve clinical outcome of leukemia patients, elucidation of pathogenesis of leukemia, screening for oncoprotein-targeting small molecules, as well as rationally designed combination of drugs with potential synergy are of importance.
... mutations in genes coding for proteins involved in signal transduction pathways and/or proteins which are important for human stem cell survival), Class II mutations (i.e. mutations in genes which code for transcription factors or mutations which inhibit differentiation and/or in apoptosis) (19,20) and Class III mutations (i.e. mutations in genes which are involved in epigenetic regulation e.g. ...
DNA methylation has been recognized as one of the most important epigenetic mechanisms regulating the expression and inhibition of genes giving rise to an organism's phenotype. It is hence of no surprise that when DNA methylation mechanisms are disrupted by intrinsic or extrinsic causes, the likelihood of tumourigenesis increases. Both hypermethylation and hypomethylation may predispose to cancer formation through aberrant inhibition or expression of particular genes and this is seen in different types of cancers, such as laryngeal squamous cell carcinoma and acute myeloid leukaemia. By increasing our knowledge and understanding of these epigenetic mechanisms, we will be able to develop diagnostic techniques such as methylation profiling, to screen for and detect aberrant methylation patterns which may predispose to cancer formation in our patients. This would enable early diagnosis and treatment which may also involve the use of drugs developed to provide directed epigenetic therapy, shifting away from the current trend which involves the use of radical anti-cancer therapy. These diagnostic and treatment options may be the future of cancer management.
... Combination chemotherapy is a useful approach to circumvent some of the problems of cancer treatment because the combination of two or more drugs with different mechanisms of action enable synergistic cancer cell death while maintaining a range of toxicity tolerated by the patient for each individual drug [18]. Combination therapies are used in treatment of all cancers, theoretically addressing the multiple gene mutations in cancers [19][20][21][22]. ...
There is an urgent need for novel effective drug regimens for the treatment of cancer. Current chemotherapy suffers from a slim therapeutic index, with significant toxicity from effective drug doses or tumor recurrence at low drug doses. Identifying synergistic interactions between drugs is a difficult process. To accelerate the discovery of potential drug combinations, I have developed a druggable genome siRNA synthetic lethal screen capable of rapidly identifying novel drug targets that would sensitize cancer cells to sublethal concentrations of microtubule destabilizing agents. I employed a high-throughput cell-based 16,560-siRNA screen to isolate a high-confidence list of genes that, when silenced, enhanced glioblastoma multiforme cancer cell chemosensitivity. Two gene products that were the major focus of my work were midline2 and the neurokinin receptor NK1R. Silencing of midline2, a PP2A-microtubule tether, sensitized cells to two microtubule destabilizing agents, vinblastine and disorazole C1, suggesting a mechanistic dependency of the phosphatidylinositol 3-kinase pathway on microtubule functionality. Combinations of phosphatidylinositol 3-kinase inhibitors with disorazole C1 and several vinca alkaloids confirmed this hypothesis. To verify microtubule destabilizing agent sensitization by NK1R silencing, I demonstrated a significant collaboration of neurokinin receptor NK1R antagonists with low concentrations of vinca alkaloids. These assay results and subsequent novel combination strategies demonstrate the tremendous ability of this synthetic lethal screen to predict potent collaborations between different classes of drugs, as well as identifying molecular constituents mediating those interactions.
... To illustrate the molecular mechanisms of leukemia at organism level, evidence has been accumulated in mouse models to suggest the following paradigm: for a full blown leukemia such as AML to occur, it is necessary to have a cooperation between class I mutations, which involve genes encoding proteins in the signal transduction pathways (such as tyrosine kinases) and confer proliferative and/or survival advantage to HSPCs, and class II mutations, which disrupt the transcription factors and lead to the inhibition of hematopoietic differentiation and subsequent apoptosis. 63,64 This classical model, while well supported by many studies in human leukemia settings, has recently been challenged by reports of a new category of gene mutations which are associated with epigenetic regulation, such as the mutations of DNMT3A, IDH1/IDH2, and TET2. The incidence of these newly found mutations is considerable in hematologic malignancies, resulting in alterations in DNA methylation and/or histone modulation profiles, with subsequent aberration of gene expressions patterns. ...
DNA methyltransferases (DNMTs) are the key enzymes for genome methylation, which plays an important role in epigenetically regulated gene expression and repression. Mouse models with conditional knockout of the DNA methyltransferase 1 (DNMT1) and DNA methyltransferase 3A (DNMT3A) genes have revealed a role of DNA methylation in mediating the self-renewal and differentiation of normal hematopoietic stem cells (HSCs) and the leukemia stem cells (LSCs). Recently, various mutations of DNMT3A and other DNA methylation regulators have been identified in hematologic malignancies. Functional analysis of these mutations may lead to a better understanding of the disease mechanisms, and even the discovery of new biomarkers and/or drug targets, as well as more rational design of therapeutic regimens. Moreover, DNMTs inhibitors as epigenetic drugs have already been approved by US Food and Drug Administration for clinical use and some clinical trials are currently underway in patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). This review focuses on the biology of DNMTs with regard to epigenetic regulation, HSC renewal/differentiation, and drug discovery for targeted therapy, and delineates the latest studies that have been conducted to unfold the relationship between aberrant DNMTs and hematologic malignancies.
... Elucidation of genomic events and the cascade of their effects in cell function is crucial for identifying distinct subsets of leukemia and for developing new therapeutic strategies [136] . Two paradigms come from the identification of the key roles that PML-RARα and BCR-ABL fusion proteins play in APL and CML leukemogenesis, and from the development of ATRA/ATO and Imatinib, which greatly improve the prognosis of patients with APL or CML, respectively [137] . Optimal use of antileukemic agents has also resulted in a steady improvement in the treatment outcome of ALL [24] . ...
Leukemia is a group of heterozygous diseases of hematopoietic stem/progenitor cells that involves dynamic change in the genome. Dissection of genetic abnormalities critical to leukemia initiation provides insights into the elusive leukemogenesis, identifies distinct subsets of leukemia and predicts prognosis individually, and can also provide rational therapeutic targets for curative approaches. The past three decades have seen tremendous advances in the analysis of genotype-phenotype connection of leukemia, and in the identification of molecular biomarkers for leukemia subtypes. Intriguingly, differentiation therapy, targeted therapy and chemotherapy have turned several subtypes of leukemia from highly fatal to highly curable. The use of all-trans retinoic acid and arsenic trioxide, which trigger degradation of PML-RARalpha, the causative fusion protein generated by t (15;17) translocation in acute promyelocytic leukemia (APL), has led to a dramatic improvement of APL clinical outcome. Imatinib mesylate/ Gleevec/STI571, which inhibits the tyrosine kinase activity of BCR-ABL oncoprotein, has now become the new gold standard for the treatment of chronic myeloid leukemia. Optimal use of chemotherapeutic agents together with a stringent application of prognostic factors for risk-directed therapy in clinical trials has resulted in a steady improvement in the treatment outcome of acute lymphoblastic leukemia. Hence, the pace of progress extrapolates to a prediction of leukemia control in the twenty-first century.
... We have learned from the intense study of human cancer, which in the last three decades have seen the thorough analysis of hundreds of cancer-related genes, that there is a tremendous gap between molecular discoveries and the establishment and approval of novel effective therapy. On the other hand, molecular studies and insight into cellular and molecular pathways underlying the spectrum of human tumorigenesis have generated multiple effective anticancer treatments, including Trastuzumab (Herceptin) in breast cancer [135] and Imatinib (Glivec) in chronic myelogenous leukemia [136] . Hopefully, the identification, establishment, and approval of PDneuroprotective therapy will be much shorter. ...
Parkinson's disease (PD) is a neurodegenerative disorder affecting a significant proportion of the ageing population. The etiology is unknown and it is likely due to a multifactorial interaction of genes and the environment on the background of ageing. Findings in the last decade suggest that the contribution of genetics to familial forms of PD is much greater than previously appreciated. Twelve loci are now associated with highly penetrant autosomal dominant or recessive PD, and causative mutations have been identified in eight genes with mutation carriers often characterized by a phenotype indistinguishable from idiopathic disease. To date, PD pharmacotherapy is symptomatic only and does not slow disease progression. Understanding how genetic mutations cause familial PD is likely to clarify molecular mechanisms underlying PD in general and will provide a guide for the development of novel therapies, both preventative and palliative, applicable to all forms of parkinsonism. This review outlines the advances in the study of the genetic background of PD and their possible clinical implications.
Background:
: Acute myeloid leukemia (AML) is a hematologic malignancy with genetic alterations. RUNX1, which is an essential transcription factor for hematopoiesis, is frequently mutated in AML. Loss of function mutation of RUNX1 is correlated to poor prognosis of AML patients. It is urgent to reveal the underlying mechanism.
Research design and methods:
TCGA AML, GSE106291, GSE142700 and GSE67609 datasets were used. R package was used for define the differential expressed miRNAs, miRNA target genes, RUNX1 related gene, RUNX directly regulating genes, and so on. The relationship of gene expression with overall survival was analyzed by cox regression. KEGG and GO analysis were applied to the above mentioned genesets and overlapped genes. Alteration and importance of MAPK pathway was validated in K562 cells by Western blotting and apoptosis assay in vitro.
Results:
RUNX1 regulated MAPK pathway indirectly and directly. MAPK pathway was altered in K562 cells induced mutated RUNX1, and these cells were more sensitive to AraC after p38 was inhibited.
Conclusions:
RUNX1 could modulate MAPK pathway, which may provide a potential therapeutic target for AML patients with RUNX1 mutations.
Neurotrophins (NTs) and their receptors play a key role in neurogenesis and survival. The TRK (tropomyosin-related kinase) receptor protein tyrosine kinases (TRKA, TRKB, TRKC) are high-affinity NT receptors that are expressed in a variety of human tissues. Their role in normal and malignant hematopoiesis is poorly understood. In a prospective study involving 94 adult patients we demonstrate for the first time cell-surface expression of the 3 TRKs and constitutive activation in blasts from patients with de novo or secondary acute leukemia. At least one TRK was expressed in 55% of the analyzed cases. We establish a clear correlation between the TRK expression pattern and FAB classification. Although only few point mutations were found in TRK sequences by reverse-transcriptase-polymerase chain reaction (RT-PCR), we observed coexpression of BDNF (ligand for TRKB) in more than 50% of TRKB(+) cases (16/30). Activation of TRKA or TRKB by NGF and BDNF, respectively, efficiently rescued murine myeloid cells from irradiation-induced apoptosis. Coexpression of TRKB/BDNF or TRKA/NGF in murine hematopoietic cells induced leukemia. Moreover, activation of TRKs was important for survival of both human and murine leukemic cells. Our findings suggest that TRKs play an important role in leukemogenesis and may serve as a new drug target.
High-throughput technologies are now used to generate more than one type of data from the same biological samples. To properly integrate such data, we propose using co-modules, which describe coherent patterns across paired data sets, and conceive several modular methods for their identification. We first test these methods using in silico data, demonstrating that the integrative scheme of our Ping-Pong Algorithm uncovers drug-gene associations more accurately when considering noisy or complex data. Second, we provide an extensive comparative study using the gene-expression and drug-response data from the NCI-60 cell lines. Using information from the DrugBank and the Connectivity Map databases we show that the Ping-Pong Algorithm predicts drug-gene associations significantly better than other methods. Co-modules provide insights into possible mechanisms of action for a wide range of drugs and suggest new targets for therapy.
FLT3 is a member of receptor tyrosine kinases expressed in leukemia cells, as well as in hematopoietic stem cells. Recently, a somatic alteration of the FLT3 gene was found in acute myeloid leukemia, as an internal tandem duplication (FLT3/ITD) which caused elongation of the juxtamembrane (JM) domain of FLT3. Here we characterized the FLT3/ITD and investigated its clinical significance in acute promyelocytic leukemia (APL). Seventy-four newly diagnosed patients with APL, who were treated with the same protocol in a multi-institutional study, were studied for the FLT3/ITD. Genomic and message sequences of the FLT3 gene were amplified by means of polymerase chain reaction (PCR), and elongated PCR products were sequenced. Fifteen patients (20.3%) had FLT3/ITD, all of which were transcribed in frame. Location of the duplicated fragments (six to 30 amino acids) varied from patient to patient. However, they always contained either Y591 or Y599, but the tyrosine kinase domain was not significantly affected. This finding implied that signal transduction of FLT3 is amplified by the duplication. Clinically, the presence of FLT3/ITD was related to high peripheral white blood cell counts as well as peripheral leukemia cell counts (P < 0.0001), high LDH level (P = 0.04), and low fibrinogen concentration (P = 0.04). These data suggest that FLT3/ITD plays a significant role in progression of APL.
CUTE PROMYELOCYTIC leukemia (APL) is charac- A terized by the morphology of blast cells (M3),'s2 by t( 15; 17) transl~cation,~ which fuses the PML gene to the retinoic acid receptor (RAR) a gene?' and by a coagulopa- thy combining disseminated intravascular coagulation (DIC), fibrinolysis, and proteolysis.637 Anthracycline-cyto- sine arabinoside (Ara C) intensive chemotherapy yields a complete remission (CR) in 50% to 80% of newly diagnosed APL patients.'-17 Failure to achieve CR generally results from fatal bleeding, due to worsening of coagulopathy by chemotherapy, or from fatal sepsis during the phase of apla- sia, rather than leukemic resistance, which seems to be less frequent in APL than in other acute myeloid leukemia (AML).'-17 Fifty percent to 65% of the patients who achieve CR subsequently relapse, two thirds of them within 1 year of CR. Thus, event-free survival (EFS) (where "events" are defined by failure to achieve CR, occurrence or relapse, or death in CR) is estimated at 25% to 55% 1 year after diagno- sis.'-" All transretinoic acid (ATRA) selectively differentiates abnormal promyelocytes into mature granulocytes in APL, both in and in vivo2o23 and induced CR in 80% to 90% of newly diagn~sed"*~~~~~ -~~ and first-relapsing APL cases.27 ATRA rapidly improved coagulopathy and induced no aplasia, suggesting that it could reduce the incidence of fatal bleeding and sepsis in APL. However, in 25% to 30% of the patients, treatment with ATRA was associated with a rapid increase in leukocytes and signs of "ATRA syn- dr~me,"'~.~~ which could have a fatal outcome unless rapid decrease in leukocyte (WBC) counts or reversal of symp- toms by intravenous dexamethasone was
Analyzing the pathways by which retinoic acid (RA) induces promyelocytic leukemia/retinoic acid receptor alpha (PML/RARalpha) catabolism in acute promyelocytic leukemia (APL), we found that, in addition to caspase-mediated PML/RARalpha cleavage, RA triggers degradation of both PML/RARalpha and RARalpha. Similarly, in non-APL cells, RA directly targeted RARalpha and RARalpha fusions to the proteasome degradation pathway. Activation of either RARalpha or RXRalpha by specific agonists induced degradation of both proteins. Conversely, a mutation in RARalpha that abolishes heterodimer formation and DNA binding, blocked both RARalpha and RXRalpha degradation. Mutations in the RARalpha DNA-binding domain or AF-2 transcriptional activation region also impaired RARalpha catabolism. Hence, our results link transcriptional activation to receptor catabolism and suggest that transcriptional up-regulation of nuclear receptors by their ligands may be a feedback mechanism allowing sustained target-gene activation.
Fibroblast growth factors (FGFs) make up a large family of polypeptide growth factors that are found in organisms ranging from nematodes to humans. In vertebrates, the 22 members of the FGF family range in molecular mass from 17 to 34 kDa and share 13-71% amino acid identity. Between vertebrate species, FGFs are highly conserved in both gene structure and amino-acid sequence. FGFs have a high affinity for heparan sulfate proteoglycans and require heparan sulfate to activate one of four cell-surface FGF receptors. During embryonic development, FGFs have diverse roles in regulating cell proliferation, migration and differentiation. In the adult organism, FGFs are homeostatic factors and function in tissue repair and response to injury. When inappropriately expressed, some FGFs can contribute to the pathogenesis of cancer. A subset of the FGF family, expressed in adult tissue, is important for neuronal signal transduction in the central and peripheral nervous systems.
We designed a multicenter randomized trial comparing chemotherapy with daunorubicin-Ara C (chemotherapy group) and all transretinoic acid (ATRA) combined to the same chemotherapy (ATRA group) in newly diagnosed APL patients aged 65 years or less. The major endpoint of the study was event-free survival (EFS) ("events" being defined as failure to achieve complete remission [CR], occurrence of relapse, or death in CR). Early termination of the trial was decided after the first interim analysis, as EFS was significantly higher in the ATRA group. At the time, 101 patients had been randomized (54 in the ATRA group and 47 in the chemotherapy group). In the ATRA group, 49 (91%) patients achieved CR, 5 (9%) had early death, and 0 had resistant leukemia, compared with 38 (81%), 4 (8%), and 5 (10%) patients, respectively, in the chemotherapy group. The difference in CR rate between the two groups was not significant. The duration of coagulopathy was significantly reduced in the ATRA group, compared with the chemotherapy group. In the ATRA group, six patients relapsed after 7 to 15.5 months. In the chemotherapy group, 12 patients relapsed after 1 to 16 months, and 2 died in CR. Kaplan-Meier EFS was estimated at 79% +/- 7% and 50% +/- 9% at 12 months, respectively, in the ATRA and the chemotherapy group (P = .001). Kaplan-Meier estimate of relapse was 19% +/- 8% and 40% +/- 12% at 12 months (P = .005). In conclusion, ATRA followed by chemotherapy increases EFS in newly diagnosed APL. These results strongly suggest that ATRA should be incorporated in the front line therapy of newly diagnosed APL.
All-trans-retinoic acid induces complete remission in acute promyelocytic leukemia. However, it is not clear whether induction therapy with all-trans-retinoic acid is superior to chemotherapy alone or whether maintenance treatment with all-trans-retinoic acid improves outcome.
Three hundred forty-six patients with previously untreated acute promyelocytic leukemia were randomly assigned to receive all-trans-retinoic acid or daunorubicin plus cytarabine as induction treatment. Patients who had a complete remission received consolidation therapy consisting of one cycle of treatment identical to the induction chemotherapy, then high-dose cytarabine plus daunorubicin. Patients still in complete remission after two cycles of consolidation therapy were then randomly assigned to maintenance treatment with all-trans-retinoic acid or to observation.
Of the 174 patients treated with chemotherapy, 120 (69 percent) had a complete remission, as did 124 of the 172 (72 percent) given all-trans-retinoic acid (P=0.56). When both induction and maintenance treatments were taken into account, the estimated rates of disease-free survival at one, two, and three years were 77, 61, and 55 percent, respectively, for patients assigned to chemotherapy then all-trans-retinoic acid; 86, 75, and 75 percent for all-trans-retinoic acid then all-trans-retinoic acid; 75, 60, and 60 percent for all-trans-retinoic acid then observation; and 29, 18, and 18 percent for chemotherapy then observation. By intention-to-treat analysis, the rates of overall survival at one, two, and three years after entry into the study were 75, 57, and 50 percent, respectively, among patients assigned to chemotherapy, and 82, 72, and 67 percent among those assigned to all-trans-retinoic acid (P= 0.003).
All-trans-retinoic acid as induction or maintenance treatment improves disease-free and overall survival as compared with chemotherapy alone and should be included in the treatment of acute promyelocytic leukemia.
Non-liganded retinoic acid receptors (RARs) repress transcription of target genes by recruiting the histone deacetylase complex through a class of silencing mediators termed SMRT or N-CoR. Mutant forms of RARalpha, created by chromosomal translocations with either the PML (for promyelocytic leukaemia) or the PLZF (for promyelocytic leukaemia zinc finger) locus, are oncogenic and result in human acute promyelocytic leukaemia (APL). PML-RARalpha APL patients achieve complete remission following treatments with pharmacological doses of retinoic acids (RA); in contrast, PLZF-RARalpha patients respond very poorly, if at all. Here we report that the association of these two chimaeric receptors with the histone deacetylase (HDAC) complex helps to determine both the development of APL and the ability of patients to respond to retinoids. Consistent with these observations, inhibitors of histone deacetylase dramatically potentiate retinoid-induced differentiation of RA-sensitive, and restore retinoid responses of RA-resistant, APL cell lines. Our findings suggest that oncogenic RARs mediate leukaemogenesis through aberrant chromatin acetylation, and that pharmacological manipulation of nuclear receptor co-factors may be a useful approach in the treatment of human disease.
The excessive proliferation of the myeloid marrow compartment in Philadelphia chromosome (Ph)-positive acute and chronic leukemias has been largely attributed to a hyperactive and autonomously acting hybrid tyrosine kinase BCR-ABL, a product of the fusion between the second exon of the c-ABL proto-oncogene and 5' portions of the BCR gene on chromosome 22. This specific molecular event, amenable to attack with specifically designed inhibitors, has recently been successfully influenced by the drug CGP-57148 in mammalian cells transfected with full-length BCR-ABL gene and expressing full-length p210Bcr-Abl protein, as well as in primary human leukemic cells expressing p210Bcr-Abl fusion protein. In view of the heterogeneity of BCR-ABL transcripts associated with various phenotypes, we investigated the effect of CGP-57148 on p190Bcr-Abl- and p210Bcr-Abl-expressing, patient-derived cell lines and primary intact blast cells. In particular, we were interested in whether the variations in molecular events and/or the phenotype of Ph-positive cells would affect their susceptibility to the specific tyrosine kinase inhibitor CGP-57148. We have demonstrated that the sensitivity of human cells with lymphoblastic immunophenotype expressing p190Bcr-Abl protein is comparable to that for leukemic myeloid cells expressing p210Bcr-Abl protein. After documenting profound and phenotype-independent suppression of both autophosphorylation and cell growth, we explored the importance of time and dose of exposure on the manifestation and stability of the induced events. Although there were variations between target cells, in vitro exposure for 24-48 h induced extensive and apparently irreversible apoptosis in BCR-ABL-expressing but not other normal or BCR-ABL-negative leukemic cells. These findings support the potential use of CGP-57148 to purge Ph-positive cells from autologous bone marrow in vitro. Another important finding was the comparable suppressive effect of temporary CGP-57148 exposure on both clonogenic KBM-5 cells and the whole cell population. Exposure time and dose appeared to be important variables among various cell types. Moreover, effective doses appeared uniformly harmless to cells lacking BCR-ABL protein functioning as tyrosine kinase. Thus, the continuous exposure of target cells, at least during the initial period of 24-48 h, may prove to be an important variable in the design of in vitro and in vivo therapy using tyrosine kinase inhibitors.
All-trans-retinoic acid (RA) treatment induces morphological remission in acute promyelocytic leukemia (APL) patients carrying the t(15;17) and expressing the PML/RARalpha product by inducing terminal differentiation of the leukemic clone. RA treatment induces downregulation of PML/RARalpha and reorganization of the PML-nuclear bodies. These events have been proposed to be essential for the induction of APL cell differentiation by RA. Here, we show that in the APL-derived NB4 cell line as well as in myeloid precursor U937 cells expressing the PML/RARalpha (U937/PR9) and in blasts from APL patients, the PML/RARalpha fusion protein is cleaved by a caspase 3-like activity induced by RA treatment. In fact, a caspase 3-like activity is detectable in PML/RARalpha expressing cells after RA treatment, and selective caspase inhibitor peptides are able to prevent the RA-induced degradation of the fusion protein in vivo and in vitro. Using recombinant caspases and PML/RARalpha deletion mutants we mapped a caspase 3 cleavage site (Asp 522) within the alpha-helix region of the PML component of the fusion protein. The extent of PML/RARalpha cleavage directly correlates with the ability of RA to restore the normal PML nuclear bodies (NBs) pattern. However, RA-induced differentiation is not prevented by the persistence of the fusion product and occurs in the absence of normally structured PML NBs. These results indicate that PML/RARalpha is directly involved in conferring RA sensitivity of APL cells and that the RA-induced reassembly of PML NBs is the consequence of the disappearance of PML/RARalpha.
Two reports from China have suggested that arsenic trioxide can induce complete remissions in patients with acute promyelocytic leukemia (APL). We evaluated this drug in patients with APL in an attempt to elucidate its mechanism of action.
Twelve patients with APL who had relapsed after extensive prior therapy were treated with arsenic trioxide at doses ranging from 0.06 to 0.2 mg per kilogram of body weight per day until visible leukemic cells were eliminated from the bone marrow. Bone marrow mononuclear cells were serially monitored by flow cytometry for immunophenotype, fluorescence in situ hybridization, reverse-transcription-polymerase-chain-reaction (RT-PCR) assay for PML-RAR-alpha fusion transcripts, and Western blot analysis for expression of the apoptosis-associated proteins caspases 1, 2, and 3.
Of the 12 patients studied, 11 achieved complete remission after treatment that lasted from 12 to 39 days (range of cumulative doses, 160 to 495 mg). Adverse effects were relatively mild and included rash, lightheadedness, fatigue, and musculoskeletal pain. Cells that expressed both CD11b and CD33 (antigens characteristic of mature and immature cells, respectively), and which were found by fluorescence in situ hybridization to carry the t(15;17) translocation, increased progressively in number during treatment and persisted in the early phase of complete remission. Eight of 11 patients who initially tested positive for the PML-RAR-alpha fusion transcript by the RT-PCR assay later tested negative; 3 other patients, who persistently tested positive, relapsed early. Arsenic trioxide induced the expression of the proenzymes of caspase 2 and caspase 3 and activation of both caspase 1 and caspase 3.
Low doses of arsenic trioxide can induce complete remissions in patients with APL who have relapsed. The clinical response is associated with incomplete cytodifferentiation and the induction of apoptosis with caspase activation in leukemic cells.
In acute promyelocytic leukemia (APL) patients, retinoic acid (RA) triggers differentiation while arsenic trioxide (arsenic)
induces both a partial differentiation and apoptosis. Although their mechanisms of action are believed to be distinct, these
two drugs both induce the catabolism of the oncogenic promyelocytic leukemia (PML)/RARα fusion protein. While APL cell lines
resistant to one agent are sensitive to the other, the benefit of combining RA and arsenic in cell culture is controversial,
and thus far, no data are available in patients. Using syngenic grafts of leukemic blasts from PML/RARα transgenic mice as
a model for APL, we demonstrate that arsenic induces apoptosis and modest differentiation, and prolongs mouse survival. Furthermore,
combining arsenic with RA accelerates tumor regression through enhanced differentiation and apoptosis. Although RA or arsenic
alone only prolongs survival two- to threefold, associating the two drugs leads to tumor clearance after a 9-mo relapse-free
period. These studies establishing RA/arsenic synergy in vivo prompt the use of combined arsenic/RA treatments in APL patients
and exemplify how mouse models of human leukemia can be used to design or optimize therapies.
All-trans retinoic acid (ATRA) is an essential component of the treatment of acute promyelocytic leukemia (APL), but the optimal timing and duration remain to be determined. Molecular characterization of this disease can refine the diagnosis and could be potentially useful in monitoring response to treatment. Patients defined morphologically to have APL were randomized to receive a 5-day course of ATRA before commencing chemotherapy or to receive daily ATRA commencing with chemotherapy and continuing until complete remission (CR). The chemotherapy was that used in current MRC Leukaemia Trials. Outcome comparisons were by intention to treat with additional analysis for relevant risk factors. Patients were characterized by molecular techniques for the fusion products of the t(15;17) and monitored by reverse transcriptase-polymerase chain reaction (RT-PCR) during and after treatment. Two hundred thirty-nine patients were randomized. Treatment with extended ATRA resulted in a superior remission rate (87% v 70%, P <.001), due to fewer early and induction deaths (12% v 23%, P =.02), and less resistant disease (2% v 7%, P =.03), which was associated with a significantly more rapid recovery of neutrophils and platelets. Extended ATRA reduced relapse risk (20% v 36% at 4 years, P =.04) and resulted in superior survival (71% v 52% at 4 years, P =.005). Presenting white blood cell count (WBC) was a key determinant of outcome. The 70% of patients who presented with a WBC less than 10 x 10(9)/L had a better CR (85% v 62%, P =.0001) and reduced relapse risk (22% v 42%, P =.002) and superior survival (69% v 43%, P <. 0001). Within the low count group, extended ATRA resulted in a better CR (94% v 76%, P =.001), reduced relapse risk (13% v 35%, P =. 04), and improved survival (80% v 57%, P =.0009). There was no evidence of benefit in patients presenting with a higher WBC (>10 x 10(9)/L). Molecular monitoring after the third chemotherapy course had a correlation with risk of relapse. The relapse risk was 57% if the RT-PCR was positive versus 27% if the RT-PCR was negative (P =. 006). APL patients who present with a low WBC derive substantial benefit from combining ATRA with induction chemotherapy until remission is achieved, whereas patients with a higher WBC did not benefit. Molecular characterization of disease can improve diagnostic precision and a positive RT-PCR after consolidation identifies patients at a higher risk of relapse.
Fusion proteins involving the retinoic acid receptor α (RARα) and PML or PLZF nuclear protein are the genetic markers of acute
promyelocytic leukemia (APL). APLs with PML-RARα or PLZF-RARα fusion protein differ only in their response to retinoic acid
(RA) treatment: the t(15;17) (PML-RARα-positive) APL blasts are sensitive to RA in vitro, and patients enter disease remission
after RA treatment, while those with t(11;17) (PLZF-RARα-positive) APLs do not. Recently it has been shown that complete remission
can be achieved upon treatment with arsenic trioxide (As2O3) in PML-RARα-positive APL, even when the patient has relapsed and the disease is RA resistant. This appears to be due to
apoptosis induced by As2O3 in the APL blasts by poorly defined mechanisms. Here we report that (i) As2O3induces apoptosis only in cells expressing the PML-RARα, not the PLZF-RARα, fusion protein; (ii) PML-RARα is partially modified
by covalent linkage with a PIC-1/SUMO-1-like protein prior to As2O3 treatment, whereas PLZF-RARα is not; (iii) As2O3 treatment induces a change in the modification pattern of PML-RARα toward highly modified forms; (iv) redistribution of PML
nuclear bodies (PML-NBs) upon As2O3 treatment is accompanied by recruitment of PIC-1/SUMO-1 into PML-NBs, probably due to hypermodification of both PML and PML-RARα;
(v) As2O3-induced apoptosis is independent of the DNA binding activity located in the RARα portion of the PML-RARα fusion protein;
and (vi) the apoptotic process is bcl-2 and caspase 3 independent and is blocked only partially by a global caspase inhibitor.
Taken together, these data provide novel insights into the mechanisms involved in As2O3-induced apoptosis in APL and predict that treatment of t(11;17) (PLZF-RARα-positive) APLs with As2O3 will not be successful.
All transretinoic acid (ATRA) followed by daunorubicin (DNR)-AraC chemotherapy (CT) has improved the outcome of acute promyelocytic leukemia (APL) by comparison to CT alone. In a randomized trial, (1) we compared 2 induction schedules (ATRA followed by CT [ATRA-->CT] and ATRA plus CT [ATRA+CT, with CT added on day 3 of ATRA treatment]) and (2) we assessed the role of maintenance treatment. Four hundred thirteen patients </=75 years of age and with newly diagnosed APL were included. Induction treatment was stratified on white blood cell (WBC) count and age: patients </=65 years of age and with an initial WBC count of </=5,000/microL (n = 208) were randomized between ATRA-->CT and ATRA+CT (initially randomized patients); patients with a WBC count greater than (high WBC count group, n = 163) and patients 66 to 75 years of age with a WBC count greater than 5,000/microL (elderly group, n = 42) were not initially randomized and received ATRA+CT from day 1 and ATRA -->CT, respectively. All patients achieving CR received 2 additional DNR-AraC courses (only 1 in patients 66 to 75 years of age) and were then randomized for maintenance between no treatment, intermittent ATRA (15 days every 3 months) for 2 years, continuous low-dose CT (6 mercaptopurine + methotrexate) for 2 years, or both, using a 2-by-2 factorial design. Overall, 381 (92%) of the patients achieved complete remission (CR), 31 (7%) suffered an early death, and only 1 patient had leukemic resistance. ATRA syndrome occurred in 64 patients (15%) and was fatal in 5 cases. The CR rate was similar in all induction treatment groups. Event-free survival (EFS) was significantly lower in the high WBC group (P =.0002) and close to significance in the elderly group (P =.086) as compared with initially randomized patients. Relapse at 2 years was estimated at 6% in the ATRA+CT group, versus 16% in the ATRA-->CT group (P =.04, relative risk [RR] =.41). EFS at 2 years was estimated at 84% in the ATRA+CT group, versus 77% in the ATRA-->CT group (P =.1, RR =.62). Two hundred eighty-nine patients were randomized for maintenance. The 2-year relapse rate was 11% in patients randomized to continuous maintenance CT and 27% in patients randomized to no CT (P =.0002) and 13% in patients randomized to intermittent ATRA and 25% in patients randomized to no ATRA (P =.02). An additive effect of continuous maintenance CT and intermittent ATRA was seen, and only 6 of the 74 patients who received both maintenance treatments had relapsed. Overall survival was improved in patients who received maintenance CT (P =.01), and there was a trend for better survival in patients who received maintenance ATRA (P =.22). Our findings strongly suggest that early addition of chemotherapy to ATRA and maintenance therapy combining continuous CT and intermittent ATRA can reduce the incidence of relapse in APL. This effect already translates into significantly better survival for maintenance treatment with continuous CT.
Gastrointestinal stromal tumors (GISTs) are mesenchymal gut tumors that differ dramatically from other histologically similar neoplasms, such as leimomyomas, leiomyosarcomas (LMS), and neural tumors. Complete surgical removal remains the best current therapy for GISTs, but even major resections are associated with recurrence in approximately 90% of cases. GISTs are remarkably resistant to irradiation and standard chemotherapy; there is no role for treatment with those modalities. Treatment of advanced GIST patients with STI571, a novel selective tyrosine kinase inhibitor, results in remission rates that approach 60% and overall tumor control rates of 85%. Selected groups of patients, as based on tumor mutational status, have response rates as high as 80%. To date, STI571 therapy remains the only systemic treatment for GISTs to have meaningful clinical activity. Though other molecularly targeted therapies exist in oncology (eg, trastuzumab), STI571 is one of the first that applies a drug specifically designed to inhibit the product of a constitutively-activating mutation that drives pathogenesis of a solid tumor. Its use can serve as a paradigm for designing molecularly targeted therapies for other malignancies.
Two hundred fifty-three patients with newly diagnosed acute promyelocytic leukemia (APL) were eligible to enter the multicentric GIMEMA- AIEOP 'AIDA' trial during the period July 1993 to February 1996. As a mandatory prerequisite for eligibility, all patients had genetic evidence of the specific t(15; 17) lesion in their leukemic cells confirmed by karyotyping or by reverse transcription-polymerase chain reaction (RT-PCR) of the PML/RARα fusion gene (the latter available in 247 cases). Median age was 37.8 years (range, 2.2 to 73.9). Induction treatment consisted of oral all- trans retinoic acid (ATRA), 45 mg/m2/d until complete remission (CR), given with intravenous Idarubicin, 12 mg/m2/d on days 2, 4, 6, and 8. Three polychemotherapy cycles were given as consolidation. Hematologic and molecular response by RT-PCR was assessed after induction and after consolidation. At the time of analysis, 240 of the 253 eligible patients were evaluable for induction. Of these, 11 (5%) died of early complications and 229 (95%) achieved hematologic remission. No cases of resistant leukemia were observed. Of 139 cases studied by RT-PCR after induction, 84 (60.5%) were PCR-negative and 55 (39.5%) PCR-positive. One hundred sixty-two patients were evaluable by RT-PCR at the end of consolidation. Of these, 159 (98%) tested PCR-negative and 3 (2%), PCR-positive. After a median follow up of 12 months (range, 0 to 33), the estimated actuarial event-free survival for the whole series of 253 eligible patients was 83% ± 2.6% and 79% ± 3.2% at 1 and 2 years, respectively. This study indicates that the AIDA protocol is a well- tolerated regimen that induces molecular remission in almost all patients with PML/RARα-positive APL. Preliminary survival data suggest that a remarkable cure rate can be obtained with this treatment.
Bcr-Abl constitutes a deregulated tyrosine kinase involved in the pathogenesis of chronic myeloid leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL). Although activation of the transcription factor NF-κB/Rel has been demonstrated, mechanisms of NF-κB/Rel activation by Bcr-Abl remain obscure. In this paper we demonstrate activation of NF-κB/Rel by Bcr-Abl and for the first time by v-Abl. Furthermore, we investigated mechanisms of NF-κB/Rel induction by Bcr-Abl and v-Abl. Both Bcr-Abl and v-Abl induced NF-κB/Rel DNA binding in Ba/F3 cells. DNA binding was a result of nuclear translocation of p65/RelA, whereas p65/RelA expression was unaffected. Nuclear translocation of p65/RelA is at least partially due to increased IκBα degradation, which is independent of IκB kinase (IKK) activity. IKK activity is not deregulated by Bcr-Abl and v-Abl. NF-κB/Rel transactivation was dependent on abl kinase activity but independent of Grb2 and Grb10 binding tobcr sequences. In addition, NF-κB/Rel activation was dependent on Ras activity. Primary CML blasts showed constitutive p65/RelA NF-κB/Rel DNA binding activity. Thus NF-κB/Rel represents a potential target for molecular therapies in CML.
A prospective multicenter study was performed to investigate the clinical and molecular results of intensified double induction therapy including high-dose cytarabine (ara-C) in combination with ATRA in newly diagnosed acute promyelocytic leukemia (APL), followed by consolidation and 3 years maintenance therapy. Fifty-one patients, diagnosed and monitored from December 1994 to June 1999, were evaluated. The median age was 43 (16–60) years. The morphologic diagnosis was M3 in 40 (78%) and M3v in 11 (22%) patients. In 15 (30%) patients the initial white blood cell counts were ⩾5 × 109/l. The cytogenetic or molecular proof of the translocation t(15;17) was a mandatory prerequisite for eligibility. The diagnosis was confirmed by karyotyping in 46 and by RT-PCR of the PML/RARα transcript in 45 cases. The rate of complete hematological remission was 92% and the early death rate 8%. Monitoring of minimal residual disease by RT-PCR of PML/RARα (sensitivity 10−4) showed negativity in 29 of 32 (91%) evaluable cases after induction, in 23 of 25 (92%) after consolidation, and in 27 of 30 (90%) during maintenance, after a median time of 2, 4 and of 18 months after diagnosis, respectively. After a median follow-up of 27 months, the estimated actuarial 2 years overall and event-free survival were both 88% (79, 97), and the 2 years relapse-free survival 96% (90, 100). The high antileukemic efficacy of this treatment strategy is demonstrated by a rapid and extensive reduction of the malignant clone and by a low relapse rate. The results suggest that the intensity of the induction chemotherapy combined with ATRA is one of the factors which may have a critical influence on the outcome of APL. A randomized trial should assess the value of an induction therapy including ATRA and high-dose ara-C in comparison to standard-dose ara-C.
First results of a randomized trial (APL91 trial) and other randomized or non-randomized studies have shown that ATRA followed by chemotherapy significantly increased event-free survival (EFS) and survival, and decreased the incidence of relapse by comparison to chemotherapy alone in newly diagnosed APL. We present here long-term follow-up of the APL91 trial. In this trial, 101 patients had been randomized between ATRA followed by three courses of daunorubicin-AraC chemotherapy (ATRA group) and the same chemotherapy alone (chemotherapy group). Results were reanalyzed 73 months after closing of patient entry. Updated results of APL 91 trial found a Kaplan–Meier estimate of EFS and relapse rate at 4 years of 63% and 31% in the ATRA group, as compared to 17% and 78% in the chemotherapy group (P = 10−4 and relative risk 2.95, P = 10−4 and relative risk 3.68, respectively). Kaplan–Meier survival at 4 years was 76% in the ATRA group and 49% in the chemotherapy group (P = 0.026, relative risk 2.7). In the chemotherapy group, seven of the 27 relapses occurred after 18 months, but no relapse was seen after 43 months. In the ATRA group, four of the 17 relapses occurred after 18 months, including two late relapses (at 58 and 74 months). In the chemotherapy group, 23 of the 25 patients who relapsed achieved a second CR with ATRA, and the Kaplan–Meier estimate of second relapse was 40% at 30 months. In the ATRA group, the 10 patients who relapsed and were retreated with ATRA achieved a second CR. In conclusion, long-term results of APL91 trial confirm the superiority of the combination of ATRA and chemotherapy over chemotherapy alone in newly diagnosed APL, and that ATRA should be incorporated in the front-line treatment of APL.
In the latter part of the nineteenth century arsenic, chiefly in the form of solution of potassium arsenite (Fowler's solution), was the standard remedy in diseases of the blood. It was used to increase the red blood cells and hemoglobin in certain anemias and to decrease the white blood cells in leukemia. Cutler and Bradford1 were among the first to study quantitatively and scientifically the effects of arsenic on the cells of the blood. In 1878 they published the results obtained in five cases studied at the Boston City Hospital; two of the cases showed a normal blood, two were cases of anemia, and one was a case of leukemia. They made careful total counts of the white and red blood cells and found that the administration of solution of potassium arsenite in health caused a progressive decrease in the number of red and white blood corpuscles. In simple
All-trans-retinoic acid (ATRA) has been incorporated in front-line therapy for newly diagnosed acute promyelocytic leukemia (APL). We conducted a multicenter study of differentiation therapy with ATRA alone or in combination with chemotherapy followed by intensive postremission chemotherapy in patients with APL (the JALSG APL92 study), and analyzed prognostic factors to increase the cure rate in our subsequent trial. From 1992 to 1997, adult patients with newly diagnosed APL received oral ATRA 45 mg/m2 daily alone until complete remission (CR) if initial leukocyte counts were 9/l, and ATRA daily plus daunorubicin (DNR) 40 mg/m2×3 days plus enocitabine (BHAC) 200 mg/m2×5 days if leukocyte counts were ≥3.0×109/l. If peripheral blasts exceeded 1.0×109/l during therapy, DNR×3 days plus BHAC×5 days was added. After CR was achieved, three courses of consolidation and six courses of maintenance/intensification chemotherapy were administered. Of 376 patients enrolled, 369 were evaluable (median age 46 years, range 15–86 years; median leukocyte counts 2.0×109/l), and 333 (90%) achieved CR (94% of patients treated with ATRA alone, 88% with ATRA plus later chemotherapy, 89% with ATRA plus initial chemotherapy, and 86% with ATRA plus initial and later chemotherapy). At a median follow-up of 45 months, the predicted 6-year overall and event-free survival (EFS) rates for all patients were 65% and 52%, respectively. Favorable prognostic factors for CR were younger age, no or mild purpura, high serum total protein level, low lactate dehydrogenase level, and no or mild disseminated intravascular coagulation (DIC). Favorable prognostic factors for EFS were leukocyte counts 9/l, mild DIC, and no sepsis during induction therapy. In the JALSG APL97 study, we intensified chemotherapy for patients with leukocyte counts ≥3.0×109/l, and are randomly testing whether further chemotherapy is required for APL patients with negative PCR for PML/retinoic acid receptor α in the maintenance phase.
Bcr-Abl is a chimeric oncoprotein that is strongly implicated in acute lymphoblastic (ALL) and chronic myelogenous leukemias (CML). This deregulated tyrosine kinase selectively causes hematopoietic disorders resembling human leukemias in animal models and transforms fibroblasts and hematopoietic cells in culture. Bcr-Abl also protects cells from death induced on cytokine deprivation or exposure to DNA damaging agents. In addition, the antiapoptotic function of Bcr-Abl is thought to play a necessary role in hematopoietic transformation and potentially in leukemogenesis. The transcription factor NF-kappaB has been identified recently as an inhibitor of apoptosis and as a potential regulator of cellular transformation. This study shows that expression of Bcr-Abl leads to activation of NF-kappaB-dependent transcription by causing nuclear translocation of NF-kappaB as well as by increasing the transactivation function of the RelA/p65 subunit of NF-kappaB. Importantly, this activation is dependent on the tyrosine kinase activity of Bcr-Abl and partially requires Ras. The ability of Bcr-Abl to protect cytokine-dependent 32D myeloid cells from death induced by cytokine deprivation or DNA damage does not, however, require functional NF-kappaB. However, using a super-repressor form of IkappaBalpha, we show that NF-kappaB is required for Bcr-Abl-mediated tumorigenicity in nude mice and for transformation of primary bone marrow cells. This study implicates NF-kappaB as an important component of Bcr-Abl signaling. NF-kappaB-regulated genes, therefore, likely play a role in transformation by Bcr-Abl and thus in Bcr-Abl-associated human leukemias.
A unique mRNA produced in leukemic cells from a t(15;17) acute promyelocytic leukemia (APL) patient encodes a fusion protein between the retinoic acid receptor alpha (RAR alpha) and a myeloid gene product called PML. PML contains a cysteine-rich region present in a new family of apparent DNA-binding proteins that includes a regulator of the interleukin-2 receptor gene (Rpt-1) and the recombination-activating gene product (RAG-1). Accordingly, PML may represent a novel transcription factor or recombinase. The aberrant PML-RAR fusion product, while typically retinoic acid responsive, displays both cell type- and promoter-specific differences from the wild-type RAR alpha. Because patients with APL can be induced into remission with high dose RA therapy, we propose that the nonliganded PML-RAR protein is a new class of dominant negative oncogene product. Treatment with RA would not only relieve this inhibition, but the activated PML-RAR protein may actually promote myelocyte differentiation.
Retinoic acid is a vitamin A derivative with striking effects on development and cell differentiation. Several nuclear retinoic acid receptors (RARs), acting as ligand-inducible transcription factors, have been characterized and indirect evidence suggests that they have distinct roles. One of the most intriguing properties of retinoic acid is its ability to induce in vivo differentiation of acute promyelocytic leukaemia (APL) cells into mature granulocytes, leading to morphological complete remissions. Because the RAR alpha gene maps to chromosome 17q21 (ref. 14), close to the t(15;17) (q21-q11-22) translocation specifically associated with APL, we analysed RAR alpha gene structure and expression in APL cells. We report here that, in one APL-derived cell line, the RAR alpha gene has been translocated to a locus, myl, on chromosome 15, resulting in the synthesis of a myl/RAR alpha fusion messenger RNA. Using two probes located on either side of the cloned breakpoint, we have found genomic rearrangements of one or other locus in six patients out of eight, demonstrating that the RAR alpha and/or myl genes are frequently rearranged in APL and the breakpoints are clustered. These findings strongly implicate retinoic acid receptor alpha in leukaemogenesis.
Oncogenic activation of the proto-oncogene c-abl in human leukemias occurs as a result of the addition of exons from the gene
bcr and truncation of the first abl exon. Analysis of tyrosine kinase activity and quantitative measurement of transformation
potency in a single-step assay indicate that variation in bcr exon contribution results in a functional difference between
p210bcr-abl and p185bcr-abl proteins. Thus, foreign upstream sequences are important in the deregulation of the kinase activity
of the abl product, and the extent of deregulation correlates with the pathological effects of the bcr-abl proteins.
Twenty-four patients with acute promyelocytic leukemia (APL) were treated with all-trans retinoic acid (45 to 100 mg/m2/day). Of these, eight cases had been either nonresponsive or resistant to previous chemotherapy; the other 16 cases were previously untreated. All patients attained complete remission without developing bone marrow hypoplasia. Bone marrow suspension cultures were studied in 15 of the 24 patients. Fourteen of these patients had morphological maturation in response to the retinoic acid (1 mumol/L). Chloroacetate esterase and alpha-naphthyl acetate esterase staining as well as electronmicroscopic examination confirmed that retinoic acid-induced cells differentiated to granulocytes with increased functional maturation (as measured by nitroblue tetrazolium reduction, NBT). The single nonresponder to retinoic acid in vitro was resistant to treatment with retinoic acid but attained complete remission after addition of low-dose cytosine arabinoside (ara-C). During the course of therapy, none of the patients showed any abnormalities in the coagulation parameters we measured, suggesting an absence of any subclinical disseminated intravascular coagulation. The only side effects consisted of mild dryness of the lips and skin, with occasional headaches and digestive symptoms. Eight patients have relapsed after 2 to 5 months of complete remission. The others remain in complete remission at 1+ to 11+ months and are still being followed up. We conclude that all-trans retinoic acid is an effective inducer for attaining complete remission in APL.
We conducted a multicenter trial of treatment with all-trans retinoic acid (ATRA) for newly diagnosed acute promyelocytic leukemia (APL) in the AML-92 study and compared it with our previous study with standard intensive chemotherapy, the AML-89 study, in the view of complete remission (CR) rate, incidence of early death, and event-free survival (EFS). Patients were scheduled to receive oral ATRA 45 mg/m2 daily until CR. If patients had leukocyte counts above 3 x 10(9)/L at the start of therapy, they received daunorubicine (DNR) 40 mg/m2 for 3 days and behenoyl cytosine arabinoside (BHAC) 200 mg/m2 for 5 days in addition to ATRA. During the ATRA therapy, if patients showed myeloblast plus promyelocyte counts higher than 1 x 10(9)/L in the peripheral blood, they received additional DNR and BHAC in the same schedule, as well. A total of 110 patients were entered into the study. Median age was 43 years (range, 16 to 74). Twenty-eight (26%) of 109 patients (one died before the start of therapy) received ATRA alone. Ninety-seven patients (89%) achieved CR; 48 of 49 (98%) aged less than 40 years, 44 of 52 (84%) aged between 40 and 69, and 5 of 8 (63%) aged above 70 achieved CR, respectively; 25 of 28 (89%) with ATRA alone, 46 of 51 (90%) with ATRA plus initial chemotherapy and 26 of 30 (87%) with ATRA plus later chemotherapy attained CR, respectively. Nine (8%) patients died within 28 days after the start of therapy. In contrast, 44 of 62 patients (71%) attained CR, and 13 (21%) died within 28 days in the AML-89 study with the combination of DNR, BHAC, 6-mercaptopurine and prednisolone. Seven developed retinoic acid syndrome and one died of it in the present study. Other toxicities associated with this drug included cheilitis, desquamation, muscle pain, and hypertriglyceridemia. Predicted 23 months EFS for all ATRA-treated patients and disease-free survival (DFS) in the CR cases were 75% and 81%, respectively, in a median follow-up period of 21 months. Compared to the AML-89 study, there was a highly significant difference in remission rate (P = .004), EFS (P = .0007), and also early mortality rate (P = .02). Present results demonstrated that ATRA with or without chemotherapy gives a statistical improvement in CR rate and early mortality rate, as well as superior survival in newly diagnosed APL.
From January 1986 to April 1991, 107 consecutive patients with acute promyelocytic leukemia (APL) were treated with retinoic acid (RA) at an oral dose of 45-60mg/m2/d, alone or in combination with chemotherapy. In 91 cases treated with RA alone, 74 (81.3%) achieved complete remission (CR). The CR rate was 75% in 16 cases treated with combined therapy. Among 50 patients closely followed for a median of 36 months (4-60), 10 received RA as continuation therapy (Group A), 10 received chemotherapy (Group B) and 30 were treated with RA and chemotherapy alternately in regular sequence (Group C). The mean survival time was 8.4, 9.7 and 21.6 months, respectively, for the 29 cases who died. The survival probability was higher in Group C than in Group A and B (P < 0.01). RA did not provoke or aggravate DIC, it did not cause marrow hypoplasia or aplasia. The side effects were relatively mild as compared with chemotherapy. CFU-GM markedly reduced before treatment was restored to normal level after CR, while the result for L-CFU was reversed. In 40 cases examined for in vitro induction of differentiation, 39 responders were culminating in CR. Aberrant karyotype t (15; 17) was positive in all 47 cases examined prior to the treatment. It disappeared in all of the 20 cases studied after achieving CR, and reappeared in 3 cases following relapse. The best regimen to maintain a longer CR duration and survival time in this study was to use RA and chemotherapy alternately as continuation therapy.
Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome characterized by abnormal clonal myeloid proliferation and by progression to acute myelogenous leukemia (AML). CMML thus offers an opportunity to study early genetic events in the transition to AML. A recently recognized subgroup of CMML has a t(5;12)(q33;p13) balanced translocation. We report that the consequence of the t(5;12) translocation is expression of a fusion transcript in which the tyrosine kinase domain of the platelet-derived growth factor receptor beta (PDGFR beta) on chromosome 5 is coupled to a novel ets-like gene, tel, on chromosome 12. The tel-PDGFR beta fusion demonstrates the oncogenic potential of PDGFR beta and may provide a paradigm for early events in the pathogenesis of AML.
In an ongoing study, we treated 79 patients with a molecular diagnosis of acute promyelocytic leukemia (APL) using all-trans retinoic acid (RA) for remission induction. Newly diagnosed patients received cytotoxic chemotherapy for consolidation, and previously treated patients received extended all-trans RA therapy, or a radionuclide-conjugated monoclonal antibody as post-remission treatment. Unlike studies in Europe, full-dose chemotherapy was not given during induction for patients who developed leukocytosis. Overall, 43 of 49 newly diagnosed patients (88%) and 25 of 30 previously treated patients (83%) achieved complete remission. We did not encounter de novo resistance to all-trans RA in any patient who was positive for PML/RAR-alpha rearrangements by reverse transcription polymerase chain reaction analysis. Ten patients died during induction from intracranial or pulmonary hemorrhage (six patients) or the 'retinoic acid syndrome' (four patients). The use of leukapheresis or low-dose chemotherapy (hydroxyurea or cytosine arabinoside) for drug-induced leukocytosis did not decrease early mortality. Compared to historical controls, early mortality was not affected by treatment with all-trans RA; however, both relapse-free and overall survival were significantly increased. Maintenance therapy with all-trans RA was associated with short remission duration, and relapses while taking the drug were universally associated with resistance to further retinoid treatment. We conclude that the use of all-trans RA for remission induction, with or without full-dose chemotherapy, has significantly increased the survival of patients with APL. While early mortality has not yet been reduced, the avoidance of full-dose chemotherapy during induction has significantly reduced early morbidity. The major outstanding clinical issue is the development of strategies that maximize safety in high-risk patients for whom intracranial hemorrhage remains the major cause of death.
The bcr-abl oncogene, present in 95% of patients with chronic myelogenous leukemia (CML), has been implicated as the cause of this disease. A compound, designed to inhibit the Abl protein tyrosine kinase, was evaluated for its effects on cells containing the Bcr-Abl fusion protein. Cellular proliferation and tumor formation by Bcr-Abl-expressing cells were specifically inhibited by this compound. In colony-forming assays of peripheral blood or bone marrow from patients with CML, there was a 92-98% decrease in the number of bcr-abl colonies formed but no inhibition of normal colony formation. This compound may be useful in the treatment of bcr-abl-positive leukemias.
Cell surface levels of the receptor tyrosine kinase P145(c-kit), the product of the c-kit proto-oncogens, in a panel of 80 primary adult acute myeloid leukaemia (AML) specimens collected at presentation were quantitated by immunofluorescence and flow cytometry, and compared with levels on CD34+ bone marrow cells from normal donors. Receptor levels on AML blast cells were extremely variable and were similar to, or less than, those on normal stem and progenitor cells. In general P145(c-kit) expression was higher on cells of immature phenotype (FAB M1 and M2). c-kit mRNA was quantitated by ribonuclease protection assay (RPA) and was shown to be correlated with cell surface protein expression (r=0.76; P<0.001). This indicates that ligand-mediated receptor internalisation or other mechanisms of increased protein turnover are not responsible for variations in the level of P145(c-kit) in AML specimens. Quantitative Southern blotting was used to examine c-kit gene copy number in 25 of these specimens and was found to be normal in all but one. Thus we have found little evidence of over-expression of c-kit in adult AML. mRNA for the c-kit ligand, Steel Factor (SLF) was also quantitated by RPA in these specimens. While SLF message was detectable (limit of detection approximately 10(4) copies per 10 microgram total RNA; equivalent to 1 copy per 100 cells) in 19% of cases, these specimens in general contained low levels of c-kit mRNA. Thus, an autocrine cycle involving c-kit and SLF does not appear to be a common feature of AML.
A clinical trial was conducted in order to evaluate the therapeutic effect and side-effects of low-dose ATRA in the treatment of acute promyelocytic leukemia (APL). We compared the pharmacokinetic features in normal individuals with single oral ATRA at 15 mg/m2 and 45 mg/m2, respectively. The results showed that maximal plasma concentration (Cpmax) with oral 15 mg/m2 ATRA was high enough (10(-6) M) to induce APL cell differentiation. Based on these results, 27 cases of de novo APL patients were treated with continuous oral ATRA at the dose of 15-20 mg/m2/day and 24/26 evaluable cases (92%) achieved clinical CR after 13 to 67 days of ATRA treatment. No patient experienced RAS and DIC. The Cpmax with a single dose of ATRA on day 1 of treatment and immediately at CR obtained with continuous ATRA in three cases demonstrated similar values in one patient and an approximately two-fold decrease in two patients. More importantly, compared with a relatively well-matched historic group of 20 APL patients treated with high-dose ATRA, our results suggest that low-dose ATRA is as effective as high-dose in treating APL patients and may provide advantages through decreased hyperleukocytosis and other side-effects.
The therapeutic effect of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL) was evaluated among 15 APL patients at relapse after all-trans retinoic acid (ATRA) induced and chemotherapy maintained complete remission (CR). As2O3 was administered intravenously at the dose of 10 mg/d. Clinical CR was achieved in nine of 10 (90%) patients treated with As2O3 alone and in the remaining five patients treated by the combination of As2O3 and low-dose chemotherapeutic drugs or ATRA. During the treatment with As2O3, there was no bone marrow depression and only limited side effects were encountered. Pharmacokinetic studies, which were performed in eight patients, showed that after a peak level of 5.54 micromol/L to 7.30 micromol/L, plasma arsenic was rapidly eliminated, and the continuous administration of As2O3 did not alter its pharmacokinetic behaviors. In addition, increased amounts of arsenic appeared in the urine, with a daily excretion accounting for approximately 1% to 8% of the total daily dose administered. Arsenic contents in hair and nail were increased, and the peak content of arsenic could reach 2.5 to 2.7 microg/g tissue at CR. On the other hand, a decline of the arsenic content in hair and nail was observed after withdrawal of the drug. We conclude that As2O3 treatment is an effective and relatively safe drug in APL patients refractory to ATRA and conventional chemotherapy.
Recent clinical studies in China showed that As2O3 is an effective and relatively safe drug in the treatment of acute promyelocytic leukemia (APL). We found previously that As2O3 can trigger apoptosis of APL cell line NB4 cells, which is associated with downregulation of bcl-2 gene expression and modulation of PML-RAR alpha chimeric protein. To further understand the mechanisms of this alternative therapy for APL, we investigated in this report the effects of a wide range of concentrations of As2O2 on cultured primary APL cells, all-trans retinoic acid (ATRA)-susceptible (NB4 cells) and ATRA-resistant (MR2 subclone) APL cell lines. The results indicated that As2O3 had dose-dependent dual effects on APL cells: inducing preferentially apoptosis at relatively high concentrations (0.5 to 2 micromol/L) and inducing partial differentiation at low concentrations (0.1 to 0.5 micromol/L). The rapid modulation and degradation of PML-RAR alpha proteins, which was induced by As2O3 at 0.1 to 2 micromol/L, could contribute to these two effects. Bone marrow and peripheral blood examination showed that myelocyte-like cells, probably as a result of partial in vivo differentiation, and degenerative cells increased after 2 to 3 weeks of continuous in vivo As2O3 treatment when leukemic promyelocytes decreased. In conclusion, combination of induction of apoptosis and partial differention could be the main cellular mechanisms of As2O3 in the treatment of APL, and PML-RAR alpha could play an important role in determining the specific effects of As2O3 on APL cells.
Two hundred fifty-three patients with newly diagnosed acute promyelocytic leukemia (APL) were eligible to enter the multicentric GIMEMA-AIEOP "AIDA" trial during the period July 1993 to February 1996. As a mandatory prerequisite for eligibility, all patients had genetic evidence of the specific t(15;17) lesion in their leukemic cells confirmed by karyotyping or by reverse transcription-polymerase chain reaction (RT-PCR) of the PML/RAR alpha fusion gene (the latter available in 247 cases). Median age was 37.8 years (range, 2.2 to 73.9). Induction treatment consisted of oral all-trans retinoic acid (ATRA), 45 mg/m2/d until complete remission (CR), given with intravenous Idarubicin, 12 mg/m2/d on days 2, 4, 6, and 8. Three polychemotherapy cycles were given as consolidation. Hematologic and molecular response by RT-PCR was assessed after induction and after consolidation. At the time of analysis, 240 of the 253 eligible patients were evaluable for induction. Of these, 11 (5%) died of early complications and 229 (95%) achieved hematologic remission. No cases of resistant leukemia were observed. Of 139 cases studied by RT-PCR after induction, 84 (60.5%) were PCR-negative and 55 (39.5%) PCR-positive. One hundred sixty-two patients were evaluable by RT-PCR at the end of consolidation. Of these, 159 (98%) tested PCR-negative and 3 (2%), PCR-positive. After a median follow up of 12 months (range, 0 to 33), the estimated actuarial event-free survival for the whole series of 253 eligible patients was 83% +/- 2.6% and 79% +/- 3.2% at 1 and 2 years, respectively. This study indicates that the AIDA protocol is a well-tolerated regimen that induces molecular remission in almost all patients with PML/RAR alpha-positive APL. Preliminary survival data suggest that a remarkable cure rate can be obtained with this treatment.
FLT3 is a member of receptor tyrosine kinases expressed in leukemia cells, as well as in hematopoietic stem cells. Recently, a somatic alteration of the FLT3 gene was found in acute myeloid leukemia, as an internal tandem duplication (FLT3/ITD) which caused elongation of the juxtamembrane (JM) domain of FLT3. Here we characterized the FLT3/ITD and investigated its clinical significance in acute promyelocytic leukemia (APL). Seventy-four newly diagnosed patients with APL, who were treated with the same protocol in a multi-institutional study, were studied for the FLT3/ITD. Genomic and message sequences of the FLT3 gene were amplified by means of polymerase chain reaction (PCR), and elongated PCR products were sequenced. Fifteen patients (20.3%) had FLT3/ITD, all of which were transcribed in frame. Location of the duplicated fragments (six to 30 amino acids) varied from patient to patient. However, they always contained either Y591 or Y599, but the tyrosine kinase domain was not significantly affected. This finding implied that signal transduction of FLT3 is amplified by the duplication. Clinically, the presence of FLT3/ITD was related to high peripheral white blood cell counts as well as peripheral leukemia cell counts (P < 0.0001), high LDH level (P = 0.04), and low fibrinogen concentration (P = 0.04). These data suggest that FLT3/ITD plays a significant role in progression of APL.
CGP 57148 is a compound of the 2-phenylaminopyrimidine class that selectively inhibits the tyrosine kinase activity of the ABL and the platelet-derived growth factor receptor (PDGFR) protein tyrosine kinases. We previously showed that CGP 57148 selectively kills p210BCR-ABL-expressing cells. To extend these observations, we evaluated the ability of CGP 57148 to inhibit other activated ABL tyrosine kinases, including p185BCR-ABL and TEL-ABL. In cell-based assays of ABL tyrosine phosphorylation, inhibition of ABL kinase activity was observed at concentrations similar to that reported for p210BCR-ABL. Consistent with the in vitro profile of this compound, the growth of cells expressing activated ABL protein tyrosine kinases was inhibited in the absence of exogenous growth factor. Growth inhibition was also observed with a p185BCR-ABL-positive acute lymphocytic leukemia (ALL) cell line generated from a Philadelphia chromosome-positive ALL patient. As CGP 57148 inhibits the PDGFR kinase, we also showed that cells expressing an activated PDGFR tyrosine kinase, TEL-PDGFR, are sensitive to this compound. Thus, this compound may be useful for the treatment of a variety of BCR-ABL-positive leukemias and for treatment of the subset of chronic myelomonocytic leukemia patients with a TEL-PDGFR fusion protein.
We report the fusion of the Huntingtin interactin protein 1 (HIP1) gene to the platelet-derived growth factor betareceptor (PDGFbetaR) gene in a patient with chronic myelomonocytic leukemia (CMML) with a t(5;7)(q33;q11.2) translocation. Southern blot analysis of patient bone marrow cells with a PDGFbetaR gene probe demonstrated rearrangement of the PDGFbetaR gene. Anchored polymerase chain reaction using PDGFbetaR primers identified a chimeric transcript containing the HIP1 gene located at 7q11.2 fused to the PDGFbetaR gene on 5q33. HIP1 is a 116-kD protein recently cloned by yeast two-hybrid screening for proteins that interact with Huntingtin, the mutated protein in Huntington's disease. The consequence of t(5;7)(q33;q11.2) is an HIP1/PDGFbetaR fusion gene that encodes amino acids 1 to 950 of HIP1 joined in-frame to the transmembrane and tyrosine kinase domains of the PDGFbetaR. The reciprocal PDGFbetaR/HIP1 transcript is not expressed. HIP1/PDGFbetaR is a 180-kD protein when expressed in the murine hematopoietic cell line, Ba/F3, and is constitutively tyrosine phosphorylated. Furthermore, HIP1/PDGFbetaR transforms the Ba/F3 cells to interleukin-3-independent growth. These data are consistent with an alternative mechanism for activation of PDGFbetaR tyrosine kinase activity by fusion with HIP1, leading to transformation of hematopoietic cells, and may implicate Huntingtin or HIP1 in the pathogenesis of hematopoietic malignancies.
Arsenic trioxide (As2O3) induces clinical remission in acute promyelocytic leukemia (APL) with minimal toxicity and apoptosis in APL-derived NB4 cells at low (1 to 2 micromol/L) concentration. We examined the basis for NB4 cell sensitivity to As2O3 to identify experimental conditions that would render other malignant cells responsive to low concentrations of As2O3. The intracellular glutathione (GSH) content had a decisive effect on As2O3-induced apoptosis. Highly sensitive NB4 cells had the lowest GSH and the sensitivity of other cell lines was inversely proportional to their GSH content. The t(14;18) B-cell lymphoma cell line had low GSH levels and sensitivity to As2O3 at levels slightly higher than in APL cells. Experimental upmodulation of GSH content decreased the sensitivity to As2O3. Ascorbic acid and buthionine sulfoxide (BSO) decreased GSH to a greater extent, and rendered malignant cells more sensitive to As2O3. As2O3-induced apoptosis was not enhanced by ascorbic acid in normal cells, suggesting that the combination of ascorbic acid and As2O3 may be selectively toxic to some malignant cells. Ascorbic acid enhanced the antilymphoma effect of As2O3 in vivo without additional toxicity. Thus, As2O3 alone or administered with ascorbic acid may provide a novel therapy for lymphoma.
In the past decade clinical and laboratory studies have led to important new insights into the biology of chronic myeloid leukemia (CML). Basic science has defined the molecular pathogenesis of CML as unregulated signal transduction by a tyrosine kinase. Clinical science has demonstrated that it is curable through immune-mediated elimination of leukemia cells by allogeneic T lymphocytes. Clinical Features CML is a malignant clonal disorder of hematopoietic stem cells that results in increases in not only myeloid cells but also erythroid cells and platelets in peripheral blood and marked myeloid hyperplasia in the bone marrow (Figure 1A, Figure 1B, andFigure 1C). . . .
Fifty-eight acute promyelocytic leukemia (APL) patients (11 newly diagnosed and 47 relapsed) were studied for arsenic trioxide (As2O3) treatment. Clinical complete remission (CR) was obtained in 8 of 11 (72.7%) newly diagnosed cases. However, As2O3 treatment resulted in hepatic toxicity in 7 cases including 2 deaths, in contrast to the mild liver dysfunction in one third of the relapsed patients. Forty of forty-seven (85.1%) relapsed patients achieved CR. Two of three nonresponders showed clonal evolution at relapse, with disappearance of t(15;17) and PML-RARalpha fusion gene in 1 and shift to a dominant AML-1-ETO population in another, suggesting a correlation between PML-RARalpha expression and therapeutic response. In a follow-up of 33 relapsed cases over 7 to 48 months, the estimated disease-free survival (DFS) rates for 1 and 2 years were 63.6% and 41.6%, respectively, and the actual median DFS was 17 months. Patients with white blood cell (WBC) count below 10 x 10(9)/L at relapse had better survival than those with WBC count over 10 x 10(9)/L (P =.038). The duration of As2O3-induced CR was related to postremission therapy, because there was only 2 of 11 relapses in patients treated with As2O3 combined with chemotherapy, compared with 12 of 18 relapses with As2O3 alone (P =.01). Reverse transcription polymerase chain reaction (RT-PCR) analysis in both newly diagnosed and relapsed groups showed long-term use of As2O3 could lead to a molecular remission in some patients. We thus recommend that ATRA be used as first choice for remission induction in newly diagnosed APL cases, whereas As2O3 can be either used as a rescue for relapsed cases or included into multidrug consolidation/maintenance clinical trials.
The Spanish PETHEMA group designed a protocol for newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia (APL) in which induction and consolidation followed the original AIDA regimen, except for the omission of cytarabine and etoposide from consolidation. Induction consisted of 45 mg/m(2) all-trans retinoic acid (ATRA) daily until complete remission (CR) and 12 mg/m(2) idarubicin on days 2, 4, 6, and 8. Patients in CR received 3 monthly chemotherapy courses: idarubicin 5 mg/m(2)/d x 4 (course no. 1), mitoxantrone 10 mg/m(2)/d x 5 (course no. 2), and idarubicin 12 mg/m(2)/d x 1 (course no. 3). Maintenance therapy consisted of 90 mg/m(2)/d mercaptopurine orally, 15 mg/m(2)/wk methotrexate intramuscularly, and, intermittently, 45 mg/m(2)/d ATRA for 15 days every 3 months. Between November 1996 and December 1998, 123 patients with newly diagnosed PML/RARalpha-positive APL from 39 centers were enrolled. A total of 109 patients achieved CR (89%; 95% confidence interval [CI], 83 to 95), 12 died of early complications, and the remaining 2 were resistant. Consolidation treatment was associated with very low toxicity and no deaths in remission were recorded. Molecular assessment of response by reverse transcriptase-polymerase chain reaction (RT-PCR) showed conversion to PCR-negative in 48 of 99 (51%) and 82 of 88 patients (93%) after induction and consolidation, respectively. The 2-year Kaplan-Meier estimates of overall survival and event-free survival were 82% +/- 4% and 79% +/- 4%, respectively. For patients who achieved CR, the 2-year disease-free survival (DFS) was 92% +/- 3%. These data indicate that a significant reduction in toxicity might be obtained in APL using a less intensive consolidation without apparently compromising the antileukemic effect. These results also suggest a minor role for cytarabine and etoposide in the treatment of newly diagnosed PML/RARalpha-positive APL patients.