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mTOR activation is controlled by the TSC1/TSC2 complex and Rheb. Abbreviations: Rheb GTP, ras homolog enriched in brain Guanosine-5′-triphosphate; LKB1, liver kinase B1; AMPK, adenosine monophosphate kinase; Akt, also known as protein kinase B (PKB); Rheb GTP, ras homolog enriched in brain guanosine diphosphate.
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Pancreatic neuroendocrine tumors (PanNETs) are frequently diagnosed at unresectable stage and remain a medical challenge. Everolimus (RAD001, Afinitor(®), Novartis, Basel, Switzerland), an orally administered inhibitor of mammalian target of rapamycin (mTOR), was recently approved by the Food and Drug Administration to treat patients with advanced...
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It is well established that the PI3K/Akt/mTOR pathway plays a central role in cell growth and proliferation. It has also been suggested that its deregulation is associated with cancer. Genetic alterations, involving components of this pathway, are often encountered in endometrial cancers. Understanding and identifying the rate-limiting steps of thi...
Citations
... For instance, heterodimerization of two components of the tuberous sclerosis complex (TSC, comprised of TSC1 and TSC2) inhibits mTOR, leading to longer phosphorylate downstream substrates [32]. The activation of AMPK causes phosphorylation and activates TSC2, promoting its association with TSC1, thereby inactivating Rheb and inhibiting mTOR [33]. In this study, shrimp previously injected simultaneously with dsAMPK plus dsTOR or dsAMPK plus dsRheb increased the mortality rate compared to shrimp injected with dsAMPK only. ...
Shrimp immunology is vital in establishing prophylactic and therapeutic strategies for controlling pathological problems that threaten shrimp production. Apart from dietary treatments, the adenosine 5'-monophosphate-activated protein kinase (AMPK), an important regulatory enzyme that restores cellular energy balance during metabolic and physiological stress, is known to have therapeutic potential to improve shrimp's defense mechanism. Despite this, studies targeting the AMPK pathway in shrimp exposed to stressful conditions are vastly limited. In this study, AMPK was knocked down to assess the immunological changes and white shrimp, Penaeus vannamei resistance to Vibrio alginolyticus infection. Shrimps were injected individually and simultaneously with dsRNA targeting specific genes such as AMPK, Rheb, and TOR, after which the hepatopancreas was analysed for the different gene expressions. The gene expressions of AMPK, Rheb, and TOR were effectively suppressed after being treated with dsRNAs. The Western blot analysis further confirmed a reduction in the protein concentration of AMPK and Rheb in the hepatopancreas. The suppression of AMPK gene led to a robust increase in the shrimp's resistance to V. alginolyticus, whereas the activation of AMPK by metformin decreased the shrimp's disease resistance. Among the mTOR downstream targets, the HIF-1α expression in shrimp treated with dsAMPK significantly increased at 48 h but returned to normal levels when shrimp were treated with dsAMPK and either dsRheb or dsTOR. Immune responses such as RBs, LYS, and PA activities increased, while SOD decreased following the knockdown of the AMPK gene compared to the control group. However, co-injection with dsAMPK and dsTOR or dsRheb restored immune responses to normal levels. Collectively, these results demonstrate that the inactivation of AMPK may ameliorate shrimp's innate immune response to recognize and defend against pathogens via the AMPK/mTOR1 pathway.
... endothelial growth factor (VEGF) and the mammalian target of rapamycin (mTOR) are implicated in the pathogenesis of this tumor [7][8][9][10][11]. Targeted antivascular therapies which inhibit these pathways are attractive potential therapeutic agents in this tumor. ...
Objective:
To assess the effects of bevacizumab and everolimus, individually and combined, on CT perfusion (CTp) parameters in liver metastases from neuroendocrine tumors (mNET) and normal liver.
Methods:
This retrospective study comprised 27 evaluable patients with mNETs who had participated in a two-arm randomized clinical trial of mono-therapy with bevacizumab (Arm B) or everolimus (Arm E) for 3 weeks, followed by combination of both targeted agents. CTp was undertaken at baseline, 3 and 9 weeks, to evaluate blood flow (BF), blood volume (BV), mean transit time (MTT), permeability surface area product (PS), and hepatic arterial fraction (HAF) of mNET and normal liver, using a dual-input distributed parameter physiological model. Linear mixed models were used to estimate and compare CTp parameter values between time-points.
Results:
In tumor, mono-therapy with bevacizumab significantly reduced BV (p = 0.05); everolimus had no effects on CTp parameters. Following dual-therapy, BV and BF were significantly lower than baseline in both arms (p ≤ 0.04), and PS was significantly lower in Arm E (p < 0.0001). In normal liver, mono-therapy with either agent had no significant effects on CTp parameters: dual-therapy significantly reduced BV, MTT, and PS, and increased HAF, relative to baseline in Arm E (p ≤ 0.04); in Arm B, only PS reduced (p = 0.04).
Conclusions:
Bevacizumab and everolimus, individually and when combined, have significant and differential effects on CTp parameters in mNETs and normal liver, which is evident soon after starting therapy. CTp may offer an early non-invasive means to investigate the effects of drugs in tumor and normal tissue.
... EVE has gained wide interest also in other fields, for example, for the treatment of cancer, switching to less invasive phenotype of tumoral cells and inhibiting angiogenesis [5,6]. Then, due to this activity it has been proposed in de novo and maintenance liver transplant immunosuppressive protocols to prevent or treat hepatocarcinoma (HCC) recurrence, with survival benefits [7,8]. From the cellular point of view, interestingly, mTOR signaling is also involved in the mechanism of quiescent hepatic stellate cells (HSC) activation [9]. ...
... In fact, antineoplastic properties of mTOR-I seem to be limited and might be enhanced by the contemporary inhibition of the crosstalk among mTORC1, mTORC2 and Phosphatidylinositol-3 kinase (PI3K)/AKT [8,38]. ...
Everolimus (EVE), a mammalian target of rapamycin inhibitor, has been proposed as liver transplant immunosuppressive drug, gaining wide interest also for the treatment of cancer. Although an appropriate tolerance, it may induce several adverse effects, such as fibro-interstitial pneumonitis due to the acquisition of activated myofibroblasts. The exact molecular mechanism associated with epithelial to mesenchymal transition (EMT) may be crucial also in the liver context. This work examines the role and the molecular mediators of EMT in hepatic stellate cell (HSC) and human liver cancer cells (HepG2) and the potential role of EVE to maintain the epithelial phenotype rather than to act as a potential initiators of EMT.
Real time-PCR and western blot have been used to assess the capability of EVE at low-therapeutic (10 nM) and high (100 nM) dose to induce an in vitro EMT in HSC and HepG2.
Biomolecular experiments demonstrated that low concentration of EVE (10 nM) did not modify the gene expression of alpha-smooth muscle actin (α-SMA), Vimentin (VIM), Fibronectin (FN) in both HSC and HepG2 cells, whereas EVE at 100 nM induced a significant over-expression of all the three above-mentioned genes and an increment of α-SMA and FN protein levels. Additionally, 100 nM of EVE induced a significant phosphorylation of AKT and an up-regulation of TGF-β expression in HSC and HepG2 cells.
Our data, although obtained in an in vitro model, revealed, for the first time, that high concentration of EVE may induce EMT in liver cells confirming previous published evidences obtained in renal cells. Additionally, they suggested that mTOR-I should be administered at the lowest dose able to maximize their important and specific therapeutic properties minimizing or avoiding fibrosis-related adverse effects.
In summary, if confirmed by additional studies, our results could be useful for researchers to standardize new therapeutic immunosuppressive and anticancer drugs protocols.
... The anticancer efficacy is also correlated to the upregulation of adhesion molecules, a switch to less invasive phenotype of tumoral cells and the inhibition of angiogenesis is due to the reduction of vascular endothelial growth factor production and the decrease of endothelial sensitivity to such growth factor [4][5][6]. Additionally, antineoplastic properties are enhanced by the inhibition of the crosstalk among mTORC1, mTORC2 and Phosphatidylinositol-3 kinase (PI3K) [7][8][9]. ...
Everolimus (EVE) is a drug widely used in several renal transplant protocols. Although characterized by a relatively low nephrotoxicity, it may induce several adverse effects including severe fibro-interstitial pneumonitis. The exact molecular/biological mechanism associated to these pro-fibrotic effects is unknown, but epithelial to mesenchymal transition (EMT) may have a central role. Additionally, heparanase, an enzyme recently associated with the progression of chronic allograft nephropathy, could contribute to activate this machinery in renal cells.
Several biomolecular strategies (RT-PCR, immunofluorescence, zymography and migration assay) have been used to assess the capability of EVE (10, 100, 200 and 500 nM) to induce an in vitro heparanase-mediated EMT in wild-type (WT) and Heparanase (HPSE)-silenced immortalized human renal epithelial proximal tubular cells (HK-2). Additionally, microarray technology was used to find additional biological elements involved in EVE-induced EMT.
Biomolecular experiments demonstrated a significant up-regulation (more than 1.5 fold increase) of several genes encoding for well known EMT markers [(alpha-smooth muscle actin (alpha-SMA), Vimentin (VIM), Fibronectin (FN) and matrix metalloproteinase-9 (MMP9)], enhancement of MMP9 protein level and increment of cells motility in WT HK2 cells treated with high concentrations of EVE (higher than 100 nM). Similarly, immunofluorescence analysis showed that 100 nM of EVE increased alpha-SMA, VIM and FN protein expression in WT HK2 cells. All these effects were absent in both HPSE- and AKT-silenced cell lines. AKT is a protein having a central role in EMT. Additionally, microarray analysis identified other 2 genes significantly up-regulated in 100 nM EVE-treated cells (p < 0.005 and FDR < 5%): transforming growth factor beta-2 (TGFbeta2) and epidermal growth factor receptor (EGFR). Real-time PCR analysis validated microarray.
Our in vitro study reveals new biological/cellular aspects of the pro-fibrotic activity of EVE and it demonstrates, for the first time, that an heparanase-mediated EMT of renal tubular cells may be activated by high doses of this drug. Additionally, our results suggest that clinicians should administer the adequate dosage of EVE in order to increase efficacy and reduce adverse effects. Finally heparanase could be a new potential therapeutic target useful to prevent/minimize drug-related systemic fibrotic adverse effects.
... Additionally, the inhibition of the crosstalk among mTORC1, mTORC2, and phosphatidylinositol-3 kinase (PI3K) confers the antineoplastic activities of these drugs [9]. EVR received Food and Drug Administration (FDA) approval in 2009 for renal cancer carcinoma (RCC) and [6,46,47,56,57,70,72,117,118,121,135,147] successively for tuberous sclerosis and pancreatic neuroendocrine tumors [10,11]. The anticancer efficacy of mTOR-I seems to be limited to their cytostatic and no cytotoxic activities, so the clinical effect is stabilization rather than regression. ...
The mammalian target of rapamycin inhibitors (mTOR-I), sirolimus and everolimus, are immunosuppressive drugs largely used in renal transplantation. The main mechanism of action of these drugs is the inhibition of the mammalian target of rapamycin (mTOR), a regulatory protein kinase involved in lymphocyte proliferation. Additionally, the inhibition of the crosstalk among mTORC1, mTORC2, and PI3K confers the antineoplastic activities of these drugs. Because of their specific pharmacological characteristics and their relative lack of nephrotoxicity, these inhibitors are valid option to calcineurine inhibitors (CNIs) for maintenance immunosuppression in renal transplant recipients with chronic allograft nephropathy. However, as other immunosuppressive drugs, mTOR-I may induce the development of several adverse effects that need to be early recognized and treated to avoid severe illness in renal transplant patients. In particular, mTOR-I may induce systemic nonnephrological side effects including pulmonary toxicity, hematological disorders, dysmetabolism, lymphedema, stomatitis, cutaneous adverse effects, and fertility/gonadic toxicity. Although most of the adverse effects are dose related, it is extremely important for clinicians to early recognize them in order to reduce dosage or discontinue mTOR-I treatment avoiding the onset and development of severe clinical complications.
Pancreatic neuroendocrine tumors (pNETs) are rare neoplasms arising from the pancreatic islet of Langerhans and can be functioning or non-functioning based on the clinical symptoms caused by hormonal secretions. PNETs are the second most common tumor of the pancreas and represent 1-2% of all pancreatic neoplasms. The incidence of pNETs appears to be rising and the prognosis seems to be improving, likely due to the improved treatment options. Recent updates of the World Health Organization classification and grading separate pNETs into 2 broad categories according to the histopathologic criteria, including the Ki-67 proliferative index and mitotic counts: well-differentiated NET and poorly-differentiated neuroendocrine carcinoma (NEC). The classification also incorporates a new subcategory of well-differentiated high-grade NEC (grade 3) to the well-differentiated NET category. This new classification algorithm aims to improve the prediction of the clinical outcomes and survival and help clinicians select better therapeutic strategies for patient care and management. The treatment of advanced or metastatic pNETs may include surgical resection, liver-directed therapies, and/or systemic treatments. In unresectable patients, the goals of these therapies are to palliate the tumor-related symptoms and prolong the lifespan. Systemic therapy consists of the following broad modalities: somatostatin analogues, molecular targeted therapy, systemic chemotherapy, and peptide receptor radionuclide therapy. In conclusion, pNETs are diagnosed increasingly throughout the world, usually with metastatic disease and requiring systemic therapy. Each patient should be evaluated thoroughly and discussed individually by a multidisciplinary and dedicated NET-expert team, which might consider all treatment options, including ongoing clinical trials before selecting the appropriate treatment sequence.
