NVP-BEZ235, a dual PI3K/mTOR inhibitor, prevents PI3K signaling and inhibits the growth of cancer cells with activating PI3K mutations

Phosphatidylinositol-3-kinase (PI3K) pathway deregulation is a common event in human cancer, either through inactivation of the tumor suppressor phosphatase and tensin homologue deleted from chromosome 10 or activating mutations of p110-alpha. These hotspot mutations result in oncogenic activity of the enzyme and contribute to therapeutic resistance to the anti-HER2 antibody trastuzumab. The PI3K pathway is, therefore, an attractive target for cancer therapy. We have studied NVP-BEZ235, a dual inhibitor of the PI3K and the downstream mammalian target of rapamycin (mTOR). NVP-BEZ235 inhibited the activation of the downstream effectors Akt, S6 ribosomal protein, and 4EBP1 in breast cancer cells. The antiproliferative activity of NVP-BEZ235 was superior to the allosteric selective mTOR complex inhibitor everolimus in a panel of 21 cancer cell lines of different origin and mutation status. The described Akt activation due to mTOR inhibition was prevented by higher doses of NVP-BEZ235. NVP-BEZ235 reversed the hyperactivation of the PI3K/mTOR pathway caused by the oncogenic mutations of p110-alpha, E545K, and H1047R, and inhibited the proliferation of HER2-amplified BT474 cells exogenously expressing these mutations that render them resistant to trastuzumab. In trastuzumab-resistant BT474 H1047R breast cancer xenografts, NVP-BEZ235 inhibited PI3K signaling and had potent antitumor activity. In treated animals, there was complete inhibition of PI3K signaling in the skin at pharmacologically active doses, suggesting that skin may serve as surrogate tissue for pharmacodynamic studies. In summary, NVP-BEZ235 inhibits the PI3K/mTOR axis and results in antiproliferative and antitumoral activity in cancer cells with both wild-type and mutated p110-alpha.     

Growth inhibition by NVP-BEZ235, a dual PI3K/mTOR inhibitor, in hepatocellular carcinoma cell lines

Dysregulation of the phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway frequently occurs in human tumors, and is therefore considered to be a good molecular target for treatment. In hepatocellular carcinoma (HCC), overexpression of p-Akt and decrease of PTEN expression have been reported. NVP-BEZ235 is a novel dual inhibitor of PI3K and mTOR; however, its effect on HCC has not been documented. Consequently, we investigated the effects of NVP-BEZ235 on the PLC/PRF/5, HLE, JHH7 and HepG2 HCC cell lines in vitro and in vivo. NVP-BEZ235 decreased the levels of p-Akt and p-p70S6K and inhibited cell proliferation in all HCC cell lines in a dose-dependent manner. Flow cytometric analysis revealed that inhibition of cell proliferation by NVP-BEZ235 was accompanied by G1 arrest in all cell lines, and that NVP-BEZ235 induced apoptosis in PLC/PRF/5 and HLE cells. Tumor growth was suppressed without body weight loss when NVP-BEZ235 was orally administered to JHH-7 tumor-bearing mice for 11 days. These results suggest that NVP-BEZ235 is a potential new candidate for targeted HCC therapy.     

一种新型PI3K/mTOR双抑制剂GDC-0941的抗肝癌机制探讨

目的 探讨磷脂酰肌醇3磷酸激酶(PI3K)/雷帕霉素靶蛋白(mTOR)激酶双抑制剂GDC-0941抗肝癌活性及其作用机制.方法 分别采用MTT法和流式细胞术测定GDC-0941对HepG2肝癌细胞生长和细胞周期的影响;通过免疫印迹法检测信号通路蛋白、细胞周期抑制因子和凋亡相关蛋白的表达.结果 GDC-0941对HepG...     

Comparison of the effects of the PI3K/mTOR inhibitors NVP-BEZ235 and GSK2126458 on tamoxifen-resistant breast cancer cells

Background

Treatment with anti-estrogens or aromatase inhibitors is commonly used for patients with estrogen receptor-positive (ER⁺) breast cancers; however resistant disease develops almost inevitably, requiring a choice of secondary therapy. One possibility is to use inhibitors of the PI3K/mTOR pathway and several candidate drugs are in development. We examined the in vitro effects of two inhibitors of the PI3K/mTOR pathway on resistant MCF-7 cells.

Results

The derived sub-lines showed increased resistance to tamoxifen but none exhibited concomitantly increased sensitivity to the PI3K inhibitors. NVP-BEZ235 and GSK2126458 acted mainly by induction of cell cycle arrest, particularly in G₁-phase, rather than by induction of apoptosis. The lines varied considerably in their utilization of the AKT, p70S6K and ERK pathways. NVP-BEZ235 and GSK2126458 inhibited AKT signaling but NVP-BEZ235 showed greater effects than GSK2126458 on p70S6K and rpS6 signaling with effects resembling those of rapamycin.

Methods

We cultured MCF-7 cells for prolonged periods either in the presence of the anti-estrogen tamoxifen (three sub-lines) or in estrogen free medium (two sub-lines) to mimic the effects of clinical treatment. We then analyzed the effects of two dual PI3K/mTOR phosphoinositide-3-kinase inhibitors, NVP-BEZ235 and GSK2126458, on the growth and signaling pathways of these MCF-7 sub-lines. The functional status of the PI3K, mTOR and ERK pathways was analyzed by measuring phosphorylation of AKT, p70S6K, rpS6 and ERK.

Conclusion

Increased resistance to tamoxifen in these MCF-7 sub-lines is not associated with hypersensitivity to PI3K inhibitors. While both drugs inhibited AKT signaling, NVP-BEZ235 resembled rapamycin in inhibiting the mTOR pathway.Key words: breast cancer, PI3K, mTOR, BEZ235, GSK2126458, estrogen receptor, MCF-7     

Superior efficacy of co-treatment with dual PI3K/mTOR inhibitor NVP-BEZ235 and pan-histone deacetylase inhibitor against human pancreatic cancer

Genetic alterations activating K-RAS and PI3K/AKT signaling are also known to induce the activity of mTOR kinase through TORC1 and TORC2 complexes in human pancreatic ductal adenocarcinoma (PDAC). Here, we determined the effects of the dual PI3K and mTOR inhibitor, NVP-BEZ235 (BEZ235), and the pan-histone deacetylase inhibitor panobinostat (PS) against human PDAC cells. Treatment with BEZ235 or PS inhibited cell cycle progression with induction of the cell cycle inhibitory proteins, p21 waf1 and p27 kip1. BEZ235 and PS also dose dependently induced loss of cell viability of the cultured PDAC cells, associated with depletion of phosphorylated (p) AKT, as well as of the TORC1 substrates 4EBP1 and p70S6 kinase. While inhibiting p-AKT, treatment with PS induced the levels of the pro-apoptotic proteins BIM and BAK. Co-treatment with BEZ235 and PS synergistically induced apoptosis of the cultured PDAC cells. This was accompanied by marked attenuation of the levels of p-AKT and Bcl-x_L but induction of BIM. Although in vivo treatment with BEZ235 or PS reduced tumor growth, co-treatment with BEZ235 and PS was significantly more effective in controlling the xenograft growth of Panc1 PDAC cells in the nude mice. Furthermore, co-treatment with BEZ235 and PS more effectively blocked tumor growth of primary PDAC heterotransplants (possessing K-RAS mutation and AKT2 amplification) subcutaneously implanted in the nude mice than each agent alone. These findings demonstrate superior activity and support further in vivo evaluation of combined treatment with BEZ235 and PS against PDAC that possess heightened activity of RAS-RAF-ERK1/2 and PI3K-AKT-mTOR pathways.     

The PI3 kinase/mTOR blocker NVP-BEZ235 overrides resistance against irreversible ErbB inhibitors in breast cancer cells

Resistance against first and second generation (irreversible) ErbB inhibitors is an unsolved problem in clinical oncology. The purpose of this study was to examine the effects of the irreversible ErbB inhibitors pelitinib and canertinib on growth of breast and ovarian cancer cells. Although in vitro growth-inhibitory effects of both drugs exceeded by far the effects of all reversible ErbB blockers tested (lapatinib, erlotinib, and gefitinib), complete growth inhibition was usually not reached. To define the mechanism of resistance, we examined downstream signaling pathways in drug-exposed cells by Western blot analysis. Although ErbB phosphorylation was reduced by pelitinib and canertinib, activation of the AKT/mTOR pathway remained essentially unaltered in drug-resistant cells. Correspondingly, transfection of tumor cells with constitutively activated AKT was found to promote resistance against all ErbB inhibitors tested, whereas dominant negative AKT reinstalled sensitivity in drug-resistant cells. In a next step, we applied PI3K/AKT/mTOR blockers including the dual PI3K/mTOR kinase inhibitor NVP-BEZ235. These agents were found to cooperate with pelitinib and canertinib in producing in vitro growth inhibition in cancer cells resistant against ErbB-targeting drugs. In conclusion, our data show that ErbB drug-refractory activation of the PI3K/AKT/mTOR pathway plays a crucial role in resistance against classical and second-generation irreversible ErbB inhibitors, and NVP-BEZ235 can override this form of resistance against pelitinib and canertinib.     

The dual PI3K and mTOR inhibitor NVP-BEZ235 exhibits anti-proliferative activity and overcomes bortezomib resistance in mantle cell lymphoma cells

Mantle cell lymphoma (MCL) is one of the most difficult B-cell lymphomas to be treated. The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is constitutively activated in MCL and plays a critical role in tumor growth and survival. However, single targeted agent mTOR has limited efficacy in treating MCL. Here, we investigate for the first time potential efficacy of NVP-BEZ235 (BEZ235) in treating MCL by simultaneously targeting Akt and mTOR. In this study, phosphorylated Akt and mTOR level were elevated in tissue samples from MCL patients and in MCL cell lines. We also generated bortezomib-resistant MCL cell lines and found increased phosphorylation of Akt and mTOR. Individual inhibition of PI3K or mTOR had limited anti-proliferative effects, whereas dual inhibition with BEZ235 effectively inhibited cell growth. The effect of BEZ235 was synergistic and sensitized the cells to the cytotoxic effects of conventional agents. Furthermore, BEZ235 could overcome acquired resistance to bortezomib in MCL cells and suppress the activated Akt/mTOR pathway. Therefore, these data suggest that the Akt/mTOR pathway plays a key role in the growth and survival of MCL cells and that these proteins may need to be simultaneously targeted for effective treatment of the disease. Our findings suggest that BEZ235 may be an effective agent for the treatment of MCL.     

NVP-BEZ235, a dual PI3K/mTOR inhibitor,inhibits osteosarcoma cell proliferation and tumor development in vivo with an improved survival rate

Despite recent improvements in chemotherapy and surgery, the problem of non-response osteosarcoma to chemotherapy remains, and is a parameter that is critical for prognosis. The present work investigated the therapeutic value of NVP-BEZ235, a dual class I PI3K/mTOR inhibitor. NVP-BEZ235 inhibited osteosarcoma cell proliferation by inducing G0/G1 cell cycle arrest with no caspase activation. In murine pre-clinical models, NVP-BEZ235 significantly slowed down tumor progression and ectopic tumor bone formation with decreased numbers of Ki67⁺ cells and reduced tumor vasculature. Finally, NVP-BEZ235 considerably improved the survival rate of mice with osteosarcoma. Taken together, the results of the present work show that NVP-BEZ235 exhibits therapeutic interest in osteosarcoma and may be a promising adjuvant drug for bone sarcomas.     

A Phase Ib Study of the Dual PI3K/mTOR Inhibitor Dactolisib (BEZ235) Combined with Everolimus in Patients with Advanced Solid Malignancies

Background

The combination of everolimus and the imidazoquinoline derivative, BEZ235 (dactolisib), a dual PI3K/mTOR inhibitor, demonstrated synergy in a preclinical model.

Objective

To establish clinical feasibility, a phase Ib dose-escalation trial investigating safety and pharmacokinetics of this combination in patients with advanced tumors was performed.

Patients and Methods

BEZ235 was orally administered daily in escalating doses of 200, 400, and 800 mg along with everolimus at 2.5 mg daily in 28-day cycles. Nineteen patients were enrolled. Adverse events and tumor responses were evaluated using CTCAE v4.0 and RECIST 1.1, respectively. Pharmacokinetic analyses were performed.

Results

Common toxicities observed included fatigue, diarrhea, nausea, mucositis, and elevated liver enzymes. No confirmed responses were observed. BEZ235 pharmacokinetics exhibited dose-proportional increases in C_max and AUC_0-24 over the three doses, with high inter-individual variability. Non-compartmental and population pharmacokinetic-based simulations indicated significant increases in everolimus C_max and AUC_0-24 on day 28 and decreased clearance to 13.41 L/hr.

Conclusions

The combination of BEZ235 and everolimus demonstrated limited efficacy and tolerance. BEZ235 systemic exposure increased in a dose-proportional manner while oral bioavailability was quite low, which may be related to gastrointestinal-specific toxicity. The changes in steady-state pharmacokinetics of everolimus with BEZ235 highlight potential drug–drug interactions when these two drugs are administered together.

Clinicaltrials.gov: NCT01508104

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Targeting PI3K/mTOR signaling in cancer

The American Association for Cancer Research (AACR) Special Conference on Targeting PI3K/mTOR Signaling in Cancer was held in San Francisco, California from February 24 to 27, 2011. The meeting was cochaired by Drs. Lewis C. Cantley, David M. Sabatini, and Funda Meric-Bernstam. The main focus of this event was the therapeutic potential of drugs targeting the PI3K/mTOR signaling pathway for the treatment of cancer. This article summarizes the recent discoveries in the field, with particular emphasis on the major themes of the conference.     

PI3K/mTOR Signaling Pathways in Medulloblastoma

Medulloblastoma is the most common malignant brain tumor in children. Recent studies have implicated sonic hedgehog (SHH) and insulin growth factor (IGF) as important mediators in deregulated pathways, which directly inactivate tuberous sclerosis complex, leading to activation of the serine/threonine kinase, mammalian target of rapamycin (mTOR). mTOR consists of two catalytic subunits of biochemically distinct complexes called mTORC1 and mTORC2. This study aims to further elucidate the role of the mTOR pathway, in the development of medulloblastoma, and assess the use of mTOR inhibitors as novel therapeutic agents. Medulloblastoma cells treated with mTORC1 inhibitor, rapamycin, down-regulated pERK expression initially; however ERK activation was evident upon prolonged treatment. Phosphorylation of mTORC1 substrate, p70S6K at thr389 was reduced by rapamycin and pretreatment with rapamycin abrogated platelet-derived growth factor (PDGF)-induced activation of S6K, as well as that of mTORC2 substrate pAKT(Ser473). Activation of AKT was decreased at 1, 3, and 6 h of treatment, but extended treatment with rapamycin increased expression of pAKT(Ser473). Expression of cyclic dependent kinase inhibitor, P27, decreased following PDGF and increased following rapamycin treatment, suggesting their respective impact on cell proliferation via cell cycle control. Cell proliferation was increased by 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment of medulloblastoma cells, while it was suppressed following treatment with rapamycin or U0126 (MEK1/2 inhibitor). pp242, a novel combined mTORC1/2 inhibitor, and rapamycin limited proliferation by reducing the S-Phase entry as assessed by EdU incorporation, while PDGF increased EdU incorporation. pp242 reduced the number of cells entering the S-phase to a greater extent than did rapamycin. Migration of medulloblastoma cells towards fibronectin was suppressed in a time-dependent manner after rapamycin treatment. These results indicate that the mTOR pathway is involved in the pathogenesis of medulloblastoma, and that targeting this pathway may provide a strategy for therapy of medulloblastoma.     

Dual inhibition of the PI3K/mTOR pathway increases tumor radiosensitivity by normalizing tumor vasculature

The aberrant vascular architecture of solid tumors results in hypoxia that limits the efficacy of radiotherapy. Vascular normalization using antiangiogenic agents has been proposed as a means to improve radiation therapy by enhancing tumor oxygenation, but only short-lived effects for this strategy have been reported so far. Here, we show that NVP-BEZ235, a dual inhibitor of phosphoinositide-3-kinase (PI3K) and mTOR, can improve tumor oxygenation and vascular structure over a prolonged period that achieves the aim of effective vascular normalization. Because PI3K inhibition can radiosensitize tumor cells themselves, our experimental design explicitly distinguished effects on the blood vasculature versus tumor cells. Drug administration coincident with radiation enhanced the delay in tumor growth without changing tumor oxygenation, establishing that radiosensitization is a component of the response. However, the enhanced growth delay was substantially greater after induction of vascular normalization, meaning that this treatment enhanced the tumoral radioresponse. Importantly, changes in vascular morphology persisted throughout the entire course of the experiment. Our findings indicated that targeting the PI3K/mTOR pathway can modulate the tumor microenvironment to induce a prolonged normalization of blood vessels. The substantial therapeutic gain observed after combination of NVP-BEZ235 with irradiation has conceptual implications for cancer therapy and could be of broad translational importance.     

PI3K/Akt/mTOR inhibitors in breast cancer

Activation of the phosphoinositide 3 kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is common in breast cancer. There is preclinical data to support inhibition of the pathway, and phase I to III trials involving inhibitors of the pathway have been or are being conducted in solid tumors and breast cancer. Everolimus, an mTOR inhibitor, is currently approved for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. In this review, we summarise the efficacy and toxicity findings from the randomised clinical trials, with simplified guidelines on the management of potential adverse effects. Education of healthcare professionals and patients is critical for safety and compliance. While there is some clinical evidence of activity of mTOR inhibition in HR-positive and HER2-positive breast cancers, the benefits may be more pronounced in selected subsets rather than in the overall population. Further development of predictive biomarkers will be useful in the selection of patients who will benefit from inhibition of the PI3K/Akt/mTOR (PAM) pathway.KEYWORDS : Breast cancer, phosphoinositide 3 kinase (PI3K)/Akt/ mammalian target of rapamycin (mTOR), everolimus     

Targeting the PI3K/Akt/mTOR pathway--beyond rapalogs

It is well established that the PI3K pathway plays a central role in various cellular processes that can contribute to the malignant phenotype. Accordingly, pharmacological inhibition of key nodes in this signaling cascade has been a focus in developmental therapeutics. To date, agents targeting upstream receptor tyrosine kinases are best studied and have achieved greatest clinical success. Further downstream, despite efficacy in certain tumor types, the rapalogs have been somewhat disappointing in the clinic. Novel inhibitors of PI3K, Akt, and mTORC1 and 2 are now passing through early phase clinical trials. It is hoped that these agents will circumvent some of the shortcomings of the rapalogs and lead to meaningful benefits for cancer patients.     

Status of PI3K/Akt/mTOR Pathway Inhibitors in Lymphoma

The phosphatidylinositol-3-kinase (PI3K) pathway is well known to regulate a wide variety of essential cellular functions, including glucose metabolism, translational regulation of protein synthesis, cell proliferation, apoptosis, and survival. Aberrations in the PI3K pathway are among the most frequently observed in cancer, and include amplifications, rearrangements, mutations, and loss of regulators. As a net result of these anomalies, the PI3K pathway is activated in many malignancies, including in Hodgkin and non-Hodgkin lymphomas, and yields a competitive growth and survival advantage, increased metastatic ability, and resistance to conventional therapy. Numerous inhibitors targeting various nodes in the PI3K pathway are undergoing clinical development, and their current status in lymphoma will be the focus of this review.     

Multipoint targeting of the PI3K/mTOR pathway in mesothelioma

Background:

Mesothelioma is a notoriously chemotherapy-resistant neoplasm, as is evident in the dismal overall survival for patients with those of asbestos-associated disease. We previously demonstrated co-activation of multiple receptor tyrosine kinases (RTKs), including epidermal growth factor receptor (EGFR), MET, and AXL in mesothelioma cell lines, suggesting that these kinases could serve as novel therapeutic targets. Although clinical trials have not shown activity for EGFR inhibitors in mesothelioma, concurrent inhibition of various activated RTKs has pro-apoptotic and anti-proliferative effects in mesothelioma cell lines. Thus, we hypothesised that a coordinated network of multi-RTK activation contributes to mesothelioma tumorigenesis.

Methods:

Activation of PI3K/AKT/mTOR, Raf/MAPK, and co-activation of RTKs were evaluated in mesotheliomas. Effects of RTK and downstream inhibitors/shRNAs were assessed by measuring mesothelioma cell viability/growth, apoptosis, activation of signalling intermediates, expression of cell-cycle checkpoints, and cell-cycle alterations.

Results:

We demonstrate activation of the PI3K/AKT/p70S6K and RAF/MEK/MAPK pathways in mesothelioma, but not in non-neoplastic mesothelial cells. The AKT activation, but not MAPK activation, was dependent on coordinated activation of RTKs EGFR, MET, and AXL. In addition, PI3K/AKT/mTOR pathway inhibition recapitulated the anti-proliferative effects of concurrent inhibition of EGFR, MET, and AXL. Dual targeting of PI3K/mTOR by BEZ235 or a combination of RAD001 and AKT knockdown had a greater effect on mesothelioma proliferation and viability than inhibition of individual activated RTKs or downstream signalling intermediates. Inhibition of PI3K/AKT was also associated with MDM2-p53 cell-cycle regulation.

Conclusions:

These findings show that PI3K/AKT/mTOR is a crucial survival pathway downstream of multiple activated RTKs in mesothelioma, underscoring that PI3K/mTOR is a compelling target for therapeutic intervention.