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SYK inhibitor R406 more potently downregulates Mcl-1 than BTK inhibitor ibrutinib or PI3Kd inhibitor idelalisib. (A) CLL cells were preincubated for 2 hours with 1 mM of the indicated BCR inhibitor and then stimulated with imm-aIgM for additional 20 hours. Cellular extracts were prepared and analyzed by immunoblotting with the indicated antibodies. Three representative experiments of the 15 performed are shown. Additional experiments are shown in supplemental Figure 3. (B) Changes in relative Mcl-1 levels in the 15 investigated samples are plotted on the chart. Analysis of differences between untreated and inhibitor-treated samples was done with the Wilcoxon signed-rank test.
Source publication
The Bcl-2 antagonist ABT-199 (venetoclax) has demonstrated promising clinical activity in patients with chronic lymphocytic leukemia (CLL). ABT-199 is strongly cytotoxic against unstimulated peripheral blood CLL cells in vitro but is much less effective against CLL cells that have received survival signals from the microenvironment. In particular,...
Contexts in source publication
Context 1
... hours prior to the addition of immobilized anti-IgM, and the samples were harvested 20 hours later. As shown in Figure 4 and supplemental Figure 3, all 3 inhibitors significantly reduced Mcl-1 expression in anti- IgM-stimulated CLL cells, but with considerable variability between different cases. In 3 of the 12 investigated cases, all 3 inhibitors were equally effective; in 2 cases, idelalisib appeared slightly more effective, whereas in the remaining 7 cases R406 reduced to a considerably greater extent Mcl-1 expression (P , .001 and P 5 .002 ...
Context 2
... ibrutinib and idelalisib, respectively). In addition, R406 reduced to a greater extent Mcl-1 also in unstimulated CLL cells with high basal Mcl-1 levels (sample CLL-G349 in Figure 4 and samples G319, G361, G216, and G372 in supplemental Figure 3). Altogether, these results suggest that R406 more potently downregulates Mcl-1 than ibrutinib or idelalisib. ...
Context 3
... guest www.bloodjournal.org From extent by R406 in 9 of the 12 investigated samples ( Figure 5A; supplemental Figure 4). A similar effect was observed with GS-9973 (entospletinib), another more selective SYK inhibitor that has also been recently evaluated in clinical trials of CLL ( Figure 5B, upper panel). ...
Context 4
... This compound displayed the same effects as R406 also in terms of Mcl-1 downregulation ( Figure 5B, lower panel). The greater capacity of SYK inhibitors to block GSK-3 phosphorylation was found to be independent of the type of BCR stimulus (soluble or immobilized anti- IgM) and was confirmed by analyzing the expression of b-catenin, another specific GSK-3 substrate (Figures 5C-D; supplemental Figure 4). ...
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ABT-199, a potent and selective small-molecule antagonist of BCL-2, is being clinically vetted as pharmacotherapy for the treatment of acute myeloid leukemia (AML). However, given that prolonged monotherapy tends to beget resistance, we sought to investigate the means by which resistance to ABT-199 might arise in AML and the extent to which those m...
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To the editor:
In chronic lymphocytic leukemia (CLL), the median age at diagnosis is 72 years, and most patients requiring therapy have coexisting medical conditions. Venetoclax is a potent BH3-mimetic compound that selectively antagonizes BCL-2 and has shown efficacy as monotherapy and with
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Citations
... In some studies, the down-regulation of MCL1 by BTKi was observed [61,62]. In line with that, the resistance to venetoclax in CLL cells in vitro, mediated by the up-regulation of MCL1, may be interrupted by the inhibition of the BCR signaling [64]. However, the increase in BIM levels as the driving force of the synergy may be a more possible hypothesis since not every CLL sample treated with both drugs ex vivo presented with altered anti-apoptotic BCL2 protein levels [62]. ...
Recent years have seen significant improvement in chronic lymphocytic leukemia (CLL) management. Targeting B-cell lymphoma (BCL-2) and Bruton’s kinase (BTK) have become the main strategies to restrain CLL activity. These agents are generally well tolerated, but the discontinuation of these therapies happens due to resistance, adverse effects, and Richter’s transformation. A growing population of patients who have previously used both BTK inhibitors and BCL2 suffer from the constriction of the following regimens. This review explores the resistance mechanisms for both ibrutinib and venetoclax. Moreover, we present innovative approaches evaluated for treating double-refractory CLL.
... Another study showed that sustained B-cell receptor stimulation in CLL cells results in significant ABT-199 resistance, which correlates with induction of the anti-apoptotic protein Mcl-1. A major role for Mcl-1 in conferring ABT-199 resistance supported by knockdown and enforced expression experiments with primary CLL cells [20]. In this study, we showed that inhibition of Mcl-1 mRNA expression by dihydroartemisinin enhances the apoptotic effect of ABT-199 in U937 and KG-1 cells. ...
... ABT-199 shows promising anticancer activity in AML patients, however, cancer cells can develop resistance to ABT-199, which can limit its efficacy as an anti-cancer agent [8]. ABT-199 resistance can arise through multiple mechanisms, including up-regulation of Mcl-1, activation of the AKT pathway, and dependence on other anti-apoptotic proteins [18,20,28]. Also, in AML cells resistant to ABT-199, it has been observed that the relationship between Bim and Mcl-1 is strengthened and the intrinsic pathway of apoptosis is not induced. ...
Introduction:
Change in the balance of Bcl-2 family proteins is one of the main reasons for resistance of tumor cells to ABT-199. In this study, the effect of dihydroartemisinin on cell growth, apoptosis and sensitivity of the AML cells to ABT-199 was investigated.
Methods:
Cell proliferation and survival were assessed by trypan blue staining and MTT assay, respectively. Cell apoptosis was measured by Hoechst 33342 staining and caspase-3 activity assay. The expression levels of Bcl-2, Mcl-1 and Bax mRNA were tested by qRT-PCR.
Results:
Our data showed that combination therapy significantly reduced the IC50 value and synergistically decreased the AML cell survival and growth compared with dihydroartemisinin or ABT-199 alone. Treatment with each of ABT-199 or dihydroartemisinin alone clearly enhanced the Bax mRNA expression and inhibited the expression of Mcl-1 and Bcl-2 mRNA. Inhibition of Mcl-1 mRNA by dihydroartemisinin was associated with enhancement of apoptosis induced by ABT-199 in AML cells.
Conclusion:
In conclusion, dihydroartemisinin not only triggers the intrinsic pathway of apoptosis, but also can increase the sensitivity of the AML cells to ABT-199 via suppression of Mcl-1 expression.
... There are few VTX-resistance mechanisms connected to the tumor microenvironment. The activation of the B-cell receptor (BCR) by a BCL-2 inhibitor [139], as well as initializing the extracellular-signal-regulated kinase (ERK) pathway via the activation of extracellular receptors by ABT-737 [140], leads to the upregulation of MCL-1 protein. Moreover, the CD40L/CD40-mediated stimulation of CLL blasts by activated T-cells in the lymph node microenvironment prompts increased antiapoptotic protein expression (MCL1, BCL-XL, and BFL-1) [106,141,142]. ...
Venetoclax is a strongly effective B-cell lymphoma-2 inhibitor (BCL-2) with an ability to selectively restore the apoptotic potential of cancerous cells. It has been proven that in combination with immunotherapy, targeted therapies, and lower-intensity therapies such as hypomethylating agents (HMAs) or low-dose cytarabine (LDAC), the drug can improve overall outcomes for adult patients with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and multiple myeloma (MM), amongst other hematological malignancies, but its benefit in pediatric hematology remains unclear. With a number of preclinical and clinical trials emerging, the newest findings suggest that in many cases of younger patients, venetoclax combination treatment can be well-tolerated, with a safety profile similar to that in adults, despite often leading to severe infections. Studies aim to determine the activity of BCL-2 inhibitor in the treatment of both primary and refractory acute leukemias in combination with standard and high-dose chemotherapy. Although more research is required to identify the optimal venetoclax-based regimen for the pediatric population and its long-term effects on patients’ outcomes, it can become a potential therapeutic agent for pediatric oncology.
... Using ex vivo co-culture systems, we and others have previously demonstrated that a variety of microenvironmental factors can induce overexpression of anti-apoptotic proteins in CLL cells (15,(31)(32)(33)(34)(35). Phenotypically similar population of CLL cells that overexpress Bcl-2, Mcl-1, or Bcl-xL have been recently detected in vivo (4,18,(36)(37)(38)(39). ...
Targeted therapies such as venetoclax (Bcl-2 inhibitor) have revolutionized the treatment of chronic lymphocytic leukemia (CLL). We previously reported that persister CLL cells in treated patients overexpress multiple anti-apoptotic proteins and display resistance to pro-apoptotic agents. Here, we demonstrated that multidrug resistant CLL cells in vivo exhibit apoptosis restriction at a premitochondrial level due to insufficient activation of the Bax and Bak proteins. Co-immunoprecipitation analyses with selective BH-domain antagonists revealed that the pleotropic pro-apoptotic protein (Bim) is prevented from activating Bax/Bak by "switching" interactions to other upregulated anti-apoptotic proteins (Mcl-1/Bcl-xL/Bcl-2). Hence, treatments that bypass Bax/Bak restriction are required to deplete these resistant cells in patients. Protein Phosphatase 2A (PP2A) contributes to oncogenesis and treatment resistance. We observed that a small molecule activator of PP2A (SMAP) induced cytotoxicity in multiple cancer cell lines and CLL samples, including multidrug resistant leukemia/lymphoma cells. The SMAP (DT-061) activated apoptosis in multidrug resistant CLL cells through induction of mitochondrial permeability transition pores (mPTP), independent of Bax/Bak. DT-061 inhibited the growth of wild type and Bax/Bak double knockout multidrug resistant CLL cells in a xenograft mouse model. Collectively, we discovered multidrug resistant CLL cells in patients, and validated a pharmacologically tractable pathway to deplete this reservoir.
... Multiple independent mechanisms contributed to venetoclax resistance, including the acquisition of various mutations in BCL-2 and/or the upregulation of other anti-apoptotic proteins which are not targeted by venetoclax, such as BCL-XL and MCL-1 (7,8). Different groups reported that malignant cells that recently interacted in vivo with the supportive microenvironment of lymphoid tissues (9, 10), or those that were cultured in vitro with different signals that mimic microenvironment stimuli (11)(12)(13)(14)(15), show an increased expression of BCL-XL and MCL-1 and are less sensitive to venetoclax compared to quiescent or unstimulated CLL cells. In line with this, we previously reported that when peripheral blood mononuclear cells (PBMC) from CLL patients were incubated on immobilized anti-CD3 monoclonal antibodies (aCD3) to induce T cell activation, autologous activated T lymphocytes induced the activation of CLL cells, and in vitro venetoclax resistance due to the upregulation of BCL-XL and MCL-1 (11,12). ...
The treatment of chronic lymphocytic leukemia (CLL) patients with venetoclax-based regimens has demonstrated efficacy and a safety profile, but the emergence of resistant cells and disease progression is a current complication. Therapeutic target of sphingosine kinases (SPHK) 1 and 2 has opened new opportunities in the treatment combinations of cancer patients. We previously reported that the dual SPHK1/2 inhibitor, SKI-II enhanced the in vitro cell death triggered by fludarabine, bendamustine or ibrutinib and reduced the activation and proliferation of chronic lymphocytic leukemia (CLL) cells. Since we previously showed that autologous activated T cells from CLL patients favor the activation of CLL cells and the generation of venetoclax resistance due to the upregulation of BCL-XL and MCL-1, we here aim to determine whether SPHK inhibitors affect this process. To this aim we employed the dual SPHK1/2 inhibitor SKI-II and opaganib, a SPHK2 inhibitor that is being studied in clinical trials. We found that SPHK inhibitors reduce the activation of CLL cells and the generation of venetoclax resistance induced by activated T cells mainly due to a reduced upregulation of BCL-XL. We also found that SPHK2 expression was enhanced in CLL cells by activated T cells of the same patient and the presence of venetoclax selects resistant cells with high levels of SPHK2. Of note, SPHK inhibitors were able to re-sensitize already resistant CLL cells to a second venetoclax treatment. Our results highlight the therapeutic potential of SPHK inhibitors in combination with venetoclax as a promising treatment option for the patients.
... Over the past few years, heterogeneous molecular mechanisms of resistance have been observed in vitro as well as under clinical circumstances. The spectrum of molecular changes reported to be associated with acquired resistance includes alterations in the pro-survival gene BCL2 diminishing venetoclax binding, overexpression of the anti-apoptotic BCL-XL, Bcl-2, MCL1, and XIAP, and the emergence of complex karyotypes [10][11][12][13][14][15][16][17]. Mitochondrial metabolic reprogramming has also been reported as a putative driver mechanism of venetoclax resistance through AMPK-regulated oxidative phosphorylation in patients with refractory CLL [16,18]. ...
The oral, highly selective Bcl2 inhibitor venetoclax has substantially improved the therapeutic landscape of chronic lymphocytic leukemia (CLL). Despite the remarkable response rates in patients with relapsed/refractory (R/R) disease, acquired resistance is the leading cause of treatment failure, with somatic BCL2 mutations being the predominant genetic drivers underpinning venetoclax resistance. To assess the correlation between disease progression and the most common BCL2 mutations G101V and D103Y, sensitive (10−4) screening for the most common BCL2 mutations G101V and D103Y was performed in 67 R/R CLL patients during venetoclax single-agent or venetoclax–rituximab combination therapy. With a median follow-up time of 23 months, BCL2 G101V and D103Y were detected in 10.4% (7/67) and 11.9% (8/67) of the cases, respectively, with four patients harboring both resistance mutations. Ten out of eleven patients carrying BCL2 G101V and/or D103Y experienced relapse during the follow-up period, representing 43.5% of the cases (10/23) showing clinical signs of disease progression. All BCL2 G101V or D103Y variants were detected in patients receiving venetoclax as a continuous single-agent treatment while these mutations were not observed during or after fixed-duration venetoclax therapy. Targeted ultra-deep sequencing of BCL2 uncovered three additional variants in four patient samples obtained at relapse, suggesting convergent evolution and implying a cooperating role of BCL2 mutations in driving venetoclax resistance. This cohort is the largest R/R CLL patient population reported to date in which BCL2 resistance mutations were investigated. Our study demonstrates the feasibility and clinical value of sensitive screening for BCL2 resistance mutations in R/R CLL.
... The development of chemotherapy resistance remains a problem confronting clinicians, especially in an era of a constantly changing therapeutic landscape. Accordingly, venetoclax resistance has been reported in both myeloid and lymphoid malignancies [7,12,14,[22][23][24][25][26], and understanding its underlying mechanisms may allow for the development of strategies to overcome it. In this study, we explored the molecular mechanisms of venetoclax resistance in MCL using two separate models: acquired resistance, using continuous exposure to venetoclax, and microenvironmentally induced resistance, using co-cultures with human and murine stromal cells. ...
... In fact, VR cells were less dependent on all the antiapoptotic BH3 proteins and, in addition, they exhibited an overall decrease in their apoptotic response. This finding strongly contrasts with previous studies that have shown that increased levels of MCL-1, as well as an increased apoptotic dependency to MCL-1, have been described as the main driver mechanisms of venetoclax resistance in CLL [25,27], diffuse large B-cell lymphoma [24,28], multiple myeloma [12,29], and acute myeloid leukemia [11,26]. Our data implies that patients with venetoclax resistance in MCL might not benefit from additional inhibition of MCL-1 or BCL-X L . ...
... This finding is in line with a recent study which also showed dysregulation of the PI3K/Akt pathway in venetoclax resistance in MCL [32]. A metabolic reprogramming with involvement of Akt has previously also been reported in VR cells in other hematological cancers, and pharmacological inhibition of Akt has been shown to restore venetoclax sensitivity [24][25][26]28]. On the other hand, RNA-seq analysis of the MS-5 co-cultured cells only revealed two upregulated genes: WNT10A and IGFBP2, thus not allowing a GSEA analysis. ...
Simple Summary
Targeting BCL-2 through venetoclax is an effective therapy for a series of hematological cancers, such as mantle cell lymphoma (MCL), but resistance to venetoclax is an increasing challenge that needs to be overcome. In order to elucidate the resistance mechanisms to venetoclax in MCL at a molecular level, we used an in vitro model of acquired resistance and performed genetic, epigenetic and transcriptomic analyses. We found that venetoclax-resistant (VR) cells acquired a TP53 mutation and consequently exhibited a reduced apoptotic response. In addition, transcriptomic analysis showed an upregulation of the PI3K/Akt pathway in the VR cells, and an extensive drug screen revealed that Akt and ERK inhibition with TIC10 could induce apoptosis in VR cells with both acquired and intrinsic venetoclax resistance. Thus, TIC-10 might be a possible treatment option for VR patients that requires further investigation.
Abstract
Venetoclax, a BCL-2 inhibitor, has proven to be effective in several hematological malignancies, including mantle cell lymphoma (MCL). However, development of venetoclax resistance is inevitable and understanding its underlying molecular mechanisms can optimize treatment response. We performed a thorough genetic, epigenetic and transcriptomic analysis of venetoclax-sensitive and resistant MCL cell lines, also evaluating the role of the stromal microenvironment using human and murine co-cultures. In our model, venetoclax resistance was associated with abrogated TP53 activity through an acquired mutation and transcriptional downregulation leading to a diminished apoptotic response. Venetoclax-resistant cells also exhibited an upregulation of the PI3K/Akt pathway, and pharmacological inhibition of Akt and ERK with TIC-10 led to cell death in all venetoclax-resistant cell lines. Overall, we highlight the importance of targeted therapies, such as TIC-10, against venetoclax resistance-related pathways, which might represent future therapeutic prospects.
... Alternatively, resistance to BCL-2 inhibition can be adaptive and while the mechanism varies across cancers, a key means has been the upregulation of the antiapoptotic protein MCL-1. Prior work in our lab has noted the upregulation of MCL-1 as a means of AML compensation against single agent venetoclax treatment [100] and has been noted across a variety of types of cancers as a means of response [74][75][76][77]. In addition, it has been observed that FLT3-ITD mutated models that the combination of activated pathways helps to mediate resistance towards venetoclax [101]. ...
The MCL-1 inhibitor S63845 synergizes with the FLT3 inhibitor midostaurin for potent anti-leukemic effect in preclinical human models of FLT3-ITD mutated acute myeloid leukemia (AML). Acute Myeloid leukemia (AML) is a neoplastic blood disorder defined by a characteristically rapid growth rate and altered behavior of myeloid cells in the bone marrow. The FLT3 receptor is responsible for the upstream regulation of many key processes in hematopoietic cells. FLT3 internal tandem duplication (ITD) mutations are common in leukemia and have been observed in up to a third of newly diagnosed AML patients. FLT3-ITD have been implicated as a driver mutation partly responsible for disease progression and associated with increased risk of relapse and lower probability of survival. This leads to the constitutive activation of the FLT3-ITD receptor and consequently the activation of downstream constituents central to regulating cellular functions. The ultimate outcome of FLT3-ITD mutations in AML is the loss of homeostasis in hematopoietic cells and progression of the leukemic disease state. Inhibitors of the FLT3 receptor inhibit activation and subsequent downstream phosphorylation in pathway which promote AML survival and progression. The FLT3 inhibitor midostaurin acts upon possessing the FLT3 receptor and displays therapeutic efficacy against the constituently active FLT3-ITD receptor. The addition of midostaurin is a significant advance in leukemic armamentarium, but there are still challenges for the treatment of FLT3-mutated AML through the development of therapy resistance. Among mechanisms of resistance to TKI that arise from non-FLT3 dependent pathways, most notable are the resistance mechanisms relating to the cell's systems which govern the apoptotic process. This has led to interest in the pro-survival BCL-2 family member MCL-1 due to the observation across cancers of therapy resistance and relapse associated with its amplification. Of relevance to our project is the selective MCL-1 inhibitor S63845. In preclinical studies, S63845 was found to exhibit dose-dependent anti-tumor activity in-vitro and was found to be well tolerated by mice in the in-vivo studies. Here we studied the pre-clinical efficacy of S63845 and midostaurin in AML cell lines expressing FLT3-WT or mutant FLT3-ITD receptor. S63845 in combination with midostaurin synergistically promoted anti-leukemic effect in-vitro. Midostaurin lead to the reduction of MCL-1 and sensitized cells to MCL-1 inhibition. Mechanistically, midostaurin lead to changes in MCL-1 phosphorylation and promotion of its proteasomal degradation. In addition, because resistance to the BCL-2 inhibitor venetoclax is characterized diminished by upregulation of MCL-1 we also studied the impact of the combination of venetoclax resistant FLT3-ITD AML cells. Overall, our results indicate sensitivity towards the combination of midostaurin and S63845 in venetoclax resistant AML cells. This supports the use of the combination of S63845 and midostaurin as a second line treatment in the event of treatment failure or relapse post-venetoclax therapy in FLT3- ITD AML.
... IFNγ protects CLL cells from spontaneous apoptosis and promotes CLL cell survival [11][12][13][14], and it can also induce proliferation and differentiation of CLL cells [15]. More importantly, IFNγ can rescue CLL cells from apoptosis triggered by targeted therapies, such as ibrutinib [16], and it is likely implicated in resistance to venetoclax through an Mcl-1-dependent mechanism [14,17,18]. IFNγ is a type II IFN and it binds to the IFNγ receptor (IFNγR), a heterodimer of IFNγRI and IFNγRII. ...
... We previously demonstrated that perturbation of the NFκB pathway can enhance the cytotoxicity of targeted therapies against CLL cells, including that of the Bcl-2 antagonist venetoclax [28]. What is more, the NFκB pathway is at the center of BCR- [18] and CD40L-mediated resistance of CLL cells to venetoclax [29,30]. CD40L can also trigger alternative NFκB signaling to mediate resistance to BCR inhibitors [31]. ...
... Compared to the vehicle control and the venetoclax-treated cells, the proportion of late apoptotic cells was lower for both the IFNγ-treated cells (8.5% vs 17.1% for vehicle control) and IFNγ co-treated cells (17.5% vs 26.3% for venetoclax-treated cells). Overall, these data indicate that IFNγ-mediated signaling might be an even more important mechanism of resistance of CLL cells to venetoclax than signaling through CD40 and BCR [18,31]. ...
Chronic lymphocytic leukemia (CLL) is a hematological neoplasm of CD19-positive mature-appearing B lymphocytes. Despite the clinical success of targeted therapies in CLL, the development of resistance diminishes their therapeutic activity. This is also true for the Bcl-2 antagonist venetoclax. We investigated the molecular mechanisms that drive venetoclax resistance in CLL, with a clear focus to provide new strategies to successfully combat it. Activation of CLL cells with IFNγ, PMA/ionomycin, and sCD40L diminished the cytotoxicity of venetoclax. We demonstrated that the metabolic activity of cells treated with 1 nM venetoclax alone was 48% of untreated cells, and was higher for cells co-treated with IFNγ (110%), PMA/ionomycin (78%), and sCD40L (62%). As of molecular mechanism, we showed that PMA/ionomycin and sCD40L triggered translocation of NFκB in primary CLL cells, while IFNγ activated p38 MAPK, suppressed spontaneous and venetoclax-induced apoptosis and induced formation of the immunoproteasome. Inhibition of immunoproteasome with ONX-0914 suppressed activity of immunoproteasome and synergized with venetoclax against primary CLL cells. On the other hand, inhibition of p38 MAPK abolished cytoprotective effects of IFNγ. We demonstrated that venetoclax-resistant (MEC-1 VER) cells overexpressed p38 MAPK and p-Bcl-2 (Ser70), and underexpressed Mcl-1, Bax, and Bak. Inhibition of p38 MAPK or immunoproteasome triggered apoptosis in CLL cells and overcame the resistance to venetoclax of MEC-1 VER cells and venetoclax-insensitive primary CLL cells. In conclusion, the p38 MAPK pathway and immunoproteasome represent novel targets to combat venetoclax resistance in CLL.
... ABT-199 is demonstrated high cytotoxicity against CLL cells in vitro but is much less effective against CLL cells that have expressed high levels of Mcl-1. Therefore, combination therapy of CLL cell with Mcl-1 inhibitors and ABT-199 have been suggested for improvement of apoptosis-based therapies in CLL resistance cells (12)(13)(14). ...
... It has been reported that genetic factors such as Bcl-2 and Bax mutations have been associated with ABT-199 resistance. Sustained activation of B-cell receptor and AKT as well as up-regulation of Mcl-1 and Bcl-xL levels is also related to this process (12)(13)(14). However, the exact mechanisms of resistance are not fully known. ...
Objective : Chronic lymphoid leukemia (CLL) is the most common type of leukemia among adults. Increased levels of Mcl-1 and Bcl-xL is linked to resistance to Bcl-2 inhibitors including ABT-199. In this study, we investigated the effect of miRNA-16-1 on apoptosis and sensitivity of the CLL cells to ABT-199.
Materials and Methods: In this experimental study, the Mcl-1 and Bcl-2 expression were measured using qualitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting. The effect of treatments on cell survival and growth were explored with MTT assay and Trypan blue assay, respectively. The drug interaction was evaluated using combination index analysis. Apoptosis was assessed by ELISA cell death and caspase-3 activity assays.
Results: MiRNA-16-1 markedly inhibited the expression of Mcl-1 and Bcl-2 in a time dependent manner (P<0.05, relative
to blank control). Pretreatment with miRNA-16-1 synergistically suppressed the cell growth and survival and reduced the half-maximal inhibitory concentration (IC50) value of ABT-199. Moreover, miRNA-16-1 markedly augmented the apoptotic effect of ABT-199 in CLL cells (P<0.05).
Conclusion: Our findings propose that miRNA-16-1 act in concert with ABT-199 to exert synergistic anticancer efficacy against CLL, which is attributed to the inhibition of Bcl-2 and Mcl-1. This may propose a promising strategy for CLL resistant patients.
