Oral mTOR inhibitor everolimus in patients with gemcitabine-refractory metastatic pancreatic cancer

Perifosine inhibits S6K1-Gli1 signaling and enhances gemcitabine-induced anti-pancreatic cancer efficiency

PURPOSE

The pancreatic cancer has extremely low overall 5-year survival, and gemcitabine is the only approved single agent for pancreatic cancer treatment.

METHODS

In the present study, we investigated the potential effect of perifosine, a novel Akt inhibitor on gemcitabine-induced anti-pancreatic cancer effect both in vivo and in vitro.

RESULTS

We showed that sub-cytotoxic low concentration of perifosine dramatically enhanced gemcitabine-induced cytotoxicity in cultured pancreatic cancer cells. Perifosine inhibited Akt-mammalian target of rapamycin and Erk-mitogen-activated protein kinase activation in pancreatic cancer cells. Meanwhile, perifosine suppressed the hedgehog signaling, as it inhibited glioma-associated oncogenes (Gli) 1 activation and decreased its target protein patched 1 (PTCH1) expression. Our data demonstrated that perifosine blocked p70S6K1 (S6K1) activation, thus disrupting S6K1-Gli1 association and subsequent Gli1 activation. The reduction of S6K1 or Gli1 expression by target siRNAs inhibited PTCH1 expression and enhanced gemcitabine-induced cytotoxicity in pancreatic cancer cells. Significantly, perifosine dramatically enhanced gemcitabine-mediated antitumor effect in a PANC-1 xenograft severe combined immunodeficiency mice model.

CONCLUSIONS

In summary, we conclude that perifosine sensitizes gemcitabine-mediated anti-pancreatic cancer efficiency through regulating multiple signaling pathways.

mTOR is a promising therapeutical target in a subpopulation of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal disease, unusually resistant against therapy. It is generally felt that stratification of patients for personalized medicine is the way forward. Here, we report that a subpopulation of PDACs shows strong activation of the mTOR signaling cassette. Moreover, we show that inhibition of mTOR in pancreatic cancer cell lines showing high levels of mTOR signaling is associated with cancer cell death. Finally, we show using fine needle biopsies the existence of a subpopulation of PDAC patients with high activation of the mTOR signaling cassette and provide evidence that inhibition of mTOR might be clinically useful for this group. Thus, our results define an unrecognized subpopulation of PDACs, characterized by high activation of mTOR and show that identification of this specific patient group in the early phase of diagnosis is feasible.

Hematologic toxicities associated with mTOR inhibitors temsirolimus and everolimus in cancer patients: a systematic review and meta-analysis

BACKGROUND

Mammalian target of rapamycin (mTOR) inhibitors, temsirolimus and everolimus, are currently approved for the treatment of several malignancies. Hematological toxicities have been reported with these drugs, but overall incidence and relative risk remains undefined. We perform an up-to-date meta-analysis to determine the incidence and risk of hematologic toxicities associated with mTOR inhibitors.

METHODS

Several databases were searched, including PubMed, Embase and Cochrane databases. Eligible studies included prospective phase II and III trials of temsirolimus and everolimus with adequate safety data profile reporting anemia, leucopenia, neutropenia or thrombocytopenia. Overall incidence rates, relative risk (RR), and 95% confidence intervals (CI) were calculated by using either random effects or fixed effects models according to the heterogeneity of included studies.

RESULTS

A total of 5436 patients with a variety of solid tumors from 26 clinical trials were included for the meta-analysis. The overall incidences of mTOR inhibitor associated all-grade and high-grade hematologic toxicities were, respectively: anemia--38.8% and 7.5%; leucopenia--19.6% and 1.8%; neutropenia--14.9% and 5.6%; thrombocytopenia--33.1% and 3.6%. Compared to placebo/control arms, mTOR inhibitors were associated with a significantly increased risk of all-grade (RR 2.05, 95% CI: 1.52-2.77; p < 0.001) and high-grade anemia (RR 1.57, 95% CI: 1.20-2.05; p = 0.001), all-grade (RR 6.03, 95% CI: 2.76-13.14; p < 0.001) and high-grade thrombocytopenia (RR 2.73, 95% CI: 1.87-3.99; p < 0.001). Additionally, a non-significantly increased risk of all-grade leucopenia (RR 1.46, 95% CI: 0.66-3.23; p = 0.34) and neutropenia (RR 1.77, 95% CI: 0.80-3.93; p = 0.16) was observed in the mTOR inhibitor group, while the risk of high-grade leucopenia (RR 0.53, 95% CI: 0.31-0.90, p = 0.019) and neutropenia (RR 0.96, 95% CI: 0.62-1.51; p = 0.87) did not increase. Similar results were also observed in sub-group analysis according to mTOR inhibitor based regimens.

CONCLUSIONS

The use of mTOR inhibitors is associated with a significant increase in the risk of developing all-grade and high-grade anemia and thrombocytopenia compared with placebo/control arms.

[Recent update of molecular targeted therapy in pancreatic cancer]

Pancreatic ductal adenocarcinoma is one of the most dreaded malignancies and the 5th leading cause of cancer-related death in Korea. Late diagnosis and unfavorable response to both chemotherapy and radiotherapy result in exceptionally poor prognosis. Recently, the rapid advances of molecular biology allowed an in-depth understanding of pancreatic carcinogenesis, and there are many attempts to modulate signal pathway using specific targeted agent. However, the most of them have so far failed to improve survival significantly except erlotinib. The real challenge is now how these impressive advances of molecular biology could be successfully integrated into better clinical implications. Herein, we summarize the latest insights into the carcinogenesis, and their repercussions for novel targeted agents for pancreatic cancer, and provide a review of recent clinical trials using molecular targeted therapy.

Everolimus for compassionate use in multiple Basal cell carcinomas

Everolimus is an inhibitor of the mammalian target of rapamycin (mTOR) and has been shown to have antineoplastic activity in addition to its use as an immunosuppressive agent for the prevention of organ transplant rejection. We report the use of everolimus for the compassionate treatment of four elderly, nontransplant patients presenting with multiple basal cell carcinomas (BCC). All patients had a long history of BCC, had refused surgery as a current treatment option, and did not respond to alternative treatments (including topical 5-fluorouracil and imiquimod). Patients were treated with oral everolimus (1.5-3.0 mg daily) for 12 months or longer: a complete and sustained response was seen in one case, and partial responses were seen in two other cases. Everolimus was well tolerated in these elderly patients. These promising preliminary data suggest that further dose-finding, controlled clinical studies are warranted to evaluate the antineoplastic effects of everolimus in patients affected by BCC who cannot or will not undergo surgery.

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.

Second-line treatment in advanced pancreatic cancer: a comprehensive analysis of published clinical trials

BACKGROUND

There is currently no standard of care for the second-line treatment of advanced pancreatic cancer. The aim of this analysis was to compare the different therapeutic approaches in this setting.

METHODS

We carried out a systematic analysis of second-line studies in advanced pancreatic cancer that have progressed on or following gemcitabine and published or presented from 2000 to 2012.

RESULTS

Forty-four clinical trials (t) were identified; of which 34 met the inclusion criteria treating an aggregate total of 1503 patients (n). Patients who received treatments (t: 33; n: 1269) had a median overall survival (OS) of 6 months compared with 2.8 months for patients who received best supportive care only (t: 2; n: 234) (P = 0.013). The gemcitabine and platinum-based combination (t: 5; n: 154) provided a median progression-free survival and OS of 4 and 6 months compared with 1.6 and 5.3 for the rest of the regimens (t: 29; n: 1349) (P = 0.059 and 0.10, respectively) and 2.9 and 5.7 for the combination of 5-fluorouracil and platinum agents (t: 12; n: 450) (P = 0.60 and 0.22, respectively).

CONCLUSION(S)

Although not conclusive, these data showed that the advantage of second-line chemotherapy in pancreatic cancer is very limited and there is a need for more studies.

Evidence for rapamycin toxicity in pancreatic β-cells and a review of the underlying molecular mechanisms

Rapamycin is used frequently in both transplantation and oncology. Although historically thought to have little diabetogenic effect, there is growing evidence of β-cell toxicity. This Review draws evidence for rapamycin toxicity from clinical studies of islet and renal transplantation, and of rapamycin as an anticancer agent, as well as from experimental studies. Together, these studies provide evidence that rapamycin has significant detrimental effects on β-cell function and survival and peripheral insulin resistance. The mechanism of action of rapamycin is via inhibition of mammalian target of rapamycin (mTOR). This Review describes the complex mTOR signaling pathways, which control vital cellular functions including mRNA translation, cell proliferation, cell growth, differentiation, angiogenesis, and apoptosis, and examines molecular mechanisms for rapamycin toxicity in β-cells. These mechanisms include reductions in β-cell size, mass, proliferation and insulin secretion alongside increases in apoptosis, autophagy, and peripheral insulin resistance. These data bring into question the use of rapamycin as an immunosuppressant in islet transplantation and as a second-line agent in other transplant recipients developing new-onset diabetes after transplantation with calcineurin inhibitors. It also highlights the importance of close monitoring of blood glucose levels in patients taking rapamycin as an anticancer treatment, particularly those with preexisting glucose intolerance.

Molecularly targeted therapies in metastatic pancreatic cancer: a systematic review

Pancreatic cancer is the fourth leading cause of cancer-related death. Most patients present with an advanced stage of disease that has a dismal outcome, with a median survival of approximately 6 months. Evidently, there is a clear need for the development of new agents with novel mechanisms of action in this disease. A number of biological agents modulating different signal transduction pathways are currently in clinical development, inhibiting angiogenesis and targeting epidermal growth factor receptor, cell cycle, matrix metalloproteinases, cyclooxygenase-2, mammalian target of rapamycin, or proteasome. This is the first systematic review of the literature to synthesize all available data coming from trials and evaluate the efficacy and safety of molecular targeted drugs in unresectable and metastatic pancreatic cancer. However, it should be stressed that although multiple agents have been tested, only 9 phase 3 trials have been conducted and one agent (erlotinib) has been approved by the Food and Drug Administration for use in clinical practice. As knowledge accumulates on the molecular mechanisms underlying carcinogenesis in the pancreas, the anticipated development and assessment of molecularly targeted agents may offer a promising perspective for a disease which, to date, remains incurable.

Gemcitabine triggers a pro-survival response in pancreatic cancer cells through activation of the MNK2/eIF4E pathway

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive neoplastic disease. Gemcitabine, the currently used chemotherapeutic drug for PDAC, elicits only minor benefits, because of the development of escape pathways leading to chemoresistance. Herein, we aimed at investigating the involvement of the mitogen activating protein kinase interacting kinase (MNK)/eIF4E pathway in the acquired drug resistance of PDAC cells. Screening of a cohort of PDAC patients by immunohistochemistry showed that eIF4E phosphorylation correlated with disease grade, early onset of disease and worse prognosis. In PDAC cell lines, chemotherapeutic drugs induced MNK-dependent phosphorylation of eIF4E. Importantly, pharmacological inhibition of MNK activity synergistically enhanced the cytostatic effect of gemcitabine, by promoting apoptosis. RNA interference (RNAi) experiments indicated that MNK2 is mainly responsible for eIF4E phosphorylation and gemcitabine resistance in PDAC cells. Furthermore, we found that gemcitabine induced the expression of the oncogenic splicing factor SRSF1 and splicing of MNK2b, a splice variant that overrides upstream regulatory pathways and confers increased resistance to the drug. Silencing of SRSF1 by RNAi abolished this splicing event and recapitulated the effects of MNK pharmacological or genetic inhibition on eIF4E phosphorylation and apoptosis in gemcitabine-treated cells. Our results highlight a novel pro-survival pathway triggered by gemcitabine in PDAC cells, which leads to MNK2-dependent phosphorylation of eIF4E, suggesting that the MNK/eIF4E pathway represents an escape route utilized by PDAC cells to withstand chemotherapeutic treatments.

Metabolic complications with the use of mTOR inhibitors for cancer therapy

BACKGROUND

mTOR inhibitors are now approved by regulatory agencies for the treatment of a variety of malignancies. The risk of metabolic complications with these agents is not well characterized.

METHODS

PubMed was searched for articles published from 2001 until 2011. Eligible studies included prospective randomized trials evaluating temsirolimus, everolimus, and ridaforolimus in patients with all solid tumor malignancies. Sixteen eligible phase II clinical trials and 8 randomized controlled clinical trials were included in a systematic review and meta-analysis and the number of metabolic related AEs (hyperglycemia, hypercholesterolemia, and hypertriglyceridemia) was extracted. Incidence rates and incident rate ratios were calculated.

FINDINGS

Twenty-four trials, including 4261 patients, were included in the calculation of the incidence rate. The average incidence rate of all grade metabolic related events was 0.70 (95% CI, 0.47, 0.93). The average incidence rate of serious (grade 3 and 4) metabolic related adverse events was 0.11 (95% CI, 0.08, 0.15). The incidence rate ratio (IRR) of a metabolic adverse event with mTOR inhibitor therapy compared with control was 2.93 (95% CI, 2.33, 3.70) and of serious grade 3 and 4 metabolic adverse events was 4.58 (95% CI, 2.86, 7.34). The IRR of all grade hyperglycemia was 2.95 (95% CI, 2.14, 4.05) and of grade 3-4 hyperglycemia was 5.25 (95% CI, 3.07, 9.00). The IRR of all grade hypertriglyceridemia was 2.49 (95% CI, 1.76, 3.52) and of grade 3-4 hypertriglyceridemia was 2.01 (95% CI, 0.65, 6.27). The IRR of all grade hypercholesterolemia was 3.35 (95% CI, 2.17, 5.18) and of grade 3-4 hypercholesterolemia was 6.51 (95% CI, 1.48, 28.59). These findings suggest a statistically significant increase in the risk of hyperglycemia, hypercholesterolemia (all grades and grade 3 and 4), and all grade hypertriglyceridemia associated with mTOR therapy when compared with control.

INTERPRETATION

The risk of all grade and grade 3-4, hyperglycemia, hypercholesterolemia, and hypertriglyceridemia, are increase in patients treated with mTOR inhibitors compared with control.

Pancreatic tumours escape from translational control through 4E-BP1 loss

The mRNA cap-binding protein eIF4E (eukaryotic translation initiation factor 4E) permits ribosome recruitment to capped mRNAs, and its phosphorylated form has an important role in cell transformation. The oncogenic function of eIF4E is, however, antagonised by the hypophosphorylated forms of the inhibitory eIF4E-binding proteins 1 and 2. eIF4E-binding protein 1 and 2 (4E-BP1 and 2) are two major targets of the protein kinase mTOR, and are essential for the antiproliferative effects of mTOR inhibitors. Herein, we report that pancreas expresses specifically and massively 4E-BP1 (4E-BP2 is nearly undetectable). However, 4E-BP1 expression is extinguished in more than half of the human pancreatic ductal adenocarcinomas (PDAC). 4E-BP1 shutoff is recapitulated in a mouse genetic model of PDAC, which is based on a pancreas-specific mutation of Kras, the more frequently mutated oncogene in human pancreatic tumours. 4E-BP1 downregulation enhances eIF4E phosphorylation and facilitates pancreatic cancer cell proliferation in vitro and tumour development in vivo. Furthermore, 4E-BP1 loss combined with the absence of 4E-BP2 renders eIF4E phosphorylation, protein synthesis and cell proliferation resistant to mTOR inhibition. However, proliferation can be better limited by a recently developed compound that mimics the function of 4E-BP1 and 2 independently of mTOR inhibition.

Involvement of phosphatidylinositol 3-kinase/Akt pathway in gemcitabine-induced apoptosis-like cell death in insulinoma cell line INS-1

This study demonstrated gemcitabine-induced cytotoxicity in the insulinoma cell line INS-1. Gemcitabine inhibited INS-1 cell proliferation and maintained consistent cell number for 24 h, and then caused apoptosis within 48 h of incubation. Since gemcitabine activates the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, which is involved in the resistance of pancreatic exocrine cancer to gemcitabine, we investigated the participation of this pathway in gemcitabine-induced cytotoxicity in INS-1 cells. LY294002 and wortmannin, two PI3-K inhibitors, significantly prevented gemcitabine-induced cytotoxicity in INS-1 cells, indicating that the PI3-K/Akt pathway is involved in gemcitabine-induced cytotoxicity. Gemcitabine-induced Akt phosphorylation in INS-1 cells was prevented by LY294002. Although gemcitabine induced cell cycle arrest at the G1 and early S phases, LY294002 did not inhibit the cell cycle. These data suggest that PI3-K activation does not influence gemcitabine-induced cell cycle arrest. In gemcitabine-treated cells, nuclear fragmentation and DNA ladder formation were observed. These findings suggest that gemcitabine induced apoptotic cell death in INS-1 cells through the activation of the PI3-K/Akt pathway.

Synergistic interactions between sorafenib and everolimus in pancreatic cancer xenografts in mice

PURPOSE

Molecular targeting of cellular signaling pathways is a promising approach in cancer therapy, but often fails to achieve sustained benefit because of the activation of collateral cancer cell survival and proliferation pathways. We tested the hypothesis that a combination of targeted agents that inhibit compensatory pathways would be more effective than single agents in controlling pancreatic cancer cell growth. We investigated whether everolimus, an mTOR inhibitor, and sorafenib, a multi-kinase inhibitor, would together inhibit growth of low-passage, patient-derived pancreatic cancer xenografts in mice more efficaciously than either agent alone.

METHODS

Tumor volume progression was measured following treatment with both drugs as single agents, in combination, and at multiple doses. Pharmacokinetics in tumors and other tissues was also assessed. Pharmacodynamic interactions were evaluated quantitatively.

RESULTS

A 5-week regimen of daily oral doses of 10 mg/kg sorafenib and 0.5 mg/kg everolimus, alone and in combination, did not achieve significant tumor growth inhibition. Higher doses (20 mg/kg of sorafenib and 1 mg/kg of everolimus) inhibited tumor growth significantly when given alone and caused complete inhibition of growth when given in combination. Tumor volume progression was described by a linear growth model, and drug effects were described by Hill-type inhibition. Using population modeling approaches, dual-interaction parameter estimates indicated a highly synergistic pharmacodynamic interaction between the two drugs.

CONCLUSIONS

The results indicate that combinations of mTOR and multi-kinase inhibitors may offer greater efficacy in pancreatic cancer than either drug alone. Drug effects upon tumor stromal elements may contribute to the enhanced anti-tumor efficacy.

Stromal cell-derived factor 1α mediates resistance to mTOR-directed therapy in pancreatic cancer

PURPOSE

The factors preventing the translation of preclinical findings supporting the clinical development mTOR-targeted therapy in pancreatic cancer therapy remain undetermined. Stromal cell.derived factor 1α (SDF-1α)-CXCR4 signaling was examined as a representative microenvironmental factor able to promote mTOR-targeted therapy resistance in pancreatic cancer.

EXPERIMENTAL DESIGN

Primary pancreas explant xenografts and in vitro experiments were used to perform pharmacodynamic analyses of SDF-1α-CXCR4 regulation of the mTOR pathway. Combinatorial effects of CXCR4, EGFR, and mTOR pharmacologic inhibition were evaluated in temsirolimus-resistant and -sensitive xenografts. Intratumoral gene and protein expressions of mTOR pathway effectors cyclin D1, c-Myc, and VEGF were evaluated.

RESULTS

Baseline intratumoral SDF-1α gene expression correlated with temsirolimus resistance in explant models. SDF-1α stimulation of pancreatic cells resulted in CXCR4-mediated PI3-kinase-dependent S6-RP phosphorylation (pS6-RP) on exposure to temsirolimus. Combinatorial therapy with AMD3465 (CXCR4 small-molecule inhibitor) and temsirolimus resulted in effective tumor growth inhibition to overcome temsirolimus resistance. In contrast, SDF-1α exposure induced a temsirolimus-resistant phenotype in temsirolimus-sensitive explants. AMD3465 inhibited CXCR4-mediated intratumoral S6-RP phosphorylation and cyclin D and c-myc gene expression. Next, CXCR4 promoted intratumoral EGFR expression in association with temsirolimus resistance. Treatment with AMD3465, temsirolimus- and erlotinib-mediated tumor growth inhibition to overcome temsirolimus resistance in the explant model. Lastly, SDF-1α-CXCR4 signaling increased intratumoral VEGF gene and protein expression.

CONCLUSIONS

SDF-1α-CXCR4 signaling represents a microenvironmental factor that can maintain mTOR pathway fidelity to promote resistance to mTOR-targeted therapy in pancreatic cancer by a variety of mechanisms such as recruitment of EGFR signaling and angiogenesis.

Different patterns of Akt and ERK feedback activation in response to rapamycin, active-site mTOR inhibitors and metformin in pancreatic cancer cells

The mTOR pathway is aberrantly stimulated in many cancer cells, including pancreatic ductal adenocarcinoma (PDAC), and thus it is a potential target for therapy. However, the mTORC1/S6K axis also mediates negative feedback loops that attenuate signaling via insulin/IGF receptor and other tyrosine kinase receptors. Suppression of these feed-back loops unleashes over-activation of upstream pathways that potentially counterbalance the antiproliferative effects of mTOR inhibitors. Here, we demonstrate that treatment of PANC-1 or MiaPaCa-2 pancreatic cancer cells with either rapamycin or active-site mTOR inhibitors suppressed S6K and S6 phosphorylation induced by insulin and the GPCR agonist neurotensin. Rapamycin caused a striking increase in Akt phosphorylation at Ser(473) while the active-site inhibitors of mTOR (KU63794 and PP242) completely abrogated Akt phosphorylation at this site. Conversely, active-site inhibitors of mTOR cause a marked increase in ERK activation whereas rapamycin did not have any stimulatory effect on ERK activation. The results imply that first and second generation of mTOR inhibitors promote over-activation of different pro-oncogenic pathways in PDAC cells, suggesting that suppression of feed-back loops should be a major consideration in the use of these inhibitors for PDAC therapy. In contrast, metformin abolished mTORC1 activation without over-stimulating Akt phosphorylation on Ser(473) and prevented mitogen-stimulated ERK activation in PDAC cells. Metformin induced a more pronounced inhibition of proliferation than either KU63794 or rapamycin while, the active-site mTOR inhibitor was more effective than rapamycin. Thus, the effects of metformin on Akt and ERK activation are strikingly different from allosteric or active-site mTOR inhibitors in PDAC cells, though all these agents potently inhibited the mTORC1/S6K axis.

Molecular guided therapy for advanced pancreatic cancer patients with PI3K activated mutation: vision or illusion?

Despite a modern validated regimen of chemotherapy, advanced pancreatic adenocarcinoma remains the fourth most common cause of cancer-related death worldwide. The phosphoinositide 3-kinase pathway (PI3K)/Akt/mammalian target of rapamycin (mTOR) is a major signaling pathway that may be activated in advanced pancreatic cancer. To highlight the potential interest of this targetable pathway in selected advanced pancreatic cancer patients, we report herein a patient with an activated PI3K mutation who was treated in a phase I trial evaluating a treatment combination including an mTOR inhibitor.

Phosphorylation of ribosomal protein S6 attenuates DNA damage and tumor suppression during development of pancreatic cancer

The signaling pathways that mediate the development of pancreatic ductal adenocarcinoma (PDAC) downstream of mutant Kras remain incompletely understood. Here, we focus on ribosomal protein S6 (rpS6), an mTOR effector not implicated previously in cancer. Phosphorylation of rpS6 was increased in pancreatic acinar cells upon implantation of the chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) or transgenic expression of mutant Kras. To examine the functional significance of rpS6 phosphorylation, we used knockin mice lacking all five phosphorylatable sites in rpS6 (termed rpS6(P-/-) mice). Strikingly, the development of pancreatic cancer precursor lesions induced by either DMBA or mutant Kras was greatly reduced in rpS6(P-/-) mice. The rpS6 mutants expressing oncogenic Kras showed increased p53 along with increased staining of γ-H2AX and 53bp1 (Trp53bp1) in areas of acinar ductal metaplasia, suggesting that rpS6 phosphorylation attenuates Kras-induced DNA damage and p53-mediated tumor suppression. These results reveal that rpS6 phosphorylation is important for the initiation of pancreatic cancer.

A review of oral toxicity associated with mTOR inhibitor therapy in cancer patients

Aphthous-like stomatitis has been identified as one of the most common dose-limiting toxicities associated with mTOR inhibitor therapy in cancer patients. The objective of this study was to summarize the cumulative oral toxicities associated with mTOR inhibitors in published oncology trials with respect to dose, schedule, and need for dose modifications. A review of all oncology-related clinical trials of mTOR inhibitors was conducted and standardized data was abstracted from each study. 44 studies were included in the analysis with a total of 2822 patients treated with temsirolimus (19 studies), everolimus (20 studies), and ridaforolimus (five studies) for a wide range of malignancies. At least one adverse event (AE) occurred in 74.4% of patients. Mucositis was the most frequent AE overall (73.4%), the third most frequent severe AE (20.7%), accounting for 27.3% dose reductions and 13.1% of discontinuations, and the most frequent dose limiting toxicity (52.5%). Mucositis typically occurred during the first cycle of therapy and was graded as mild to moderate in approximately 90% of the patients; severe mucositis generally occurred at higher doses. There were no clear differences in mucositis among the three agents and in most cases lesions resolved spontaneously. Oral mucositis is a frequent complication of mTOR inhibitor therapy and a significant cause of dose reductions and discontinuations in oncology trials. Prevention and management strategies should be investigated to improve tolerability and better permit effective long-term regimens.

Antitumor effects of rapamycin in pancreatic cancer cells by inducing apoptosis and autophagy

Rapamycin (Rapa), an inhibitor of mammalian target of Rapamycin (mTOR), is an immunosuppressive agent that has anti-proliferative effects on some tumors. This study aims to investigate the effects of Rapa suppressing proliferation of pancreatic carcinoma PC-2 cells in vitro and its molecular mechanism involved in antitumor activities. MTT assays showed that the inhibition of proliferation of PC-2 cells in vitro was in a time- and dose-dependent manner. By using transmission electron microscopy, apoptosis bodies and formation of abundant autophagic vacuoles were observed in PC-2 cells after Rapa treatment. Flow cytometry assays also showed Rapa had a positive effect on apoptosis. MDC staining showed that the fluorescent density was higher and the number of MDC-labeled particles in PC-2 cells was greater in the Rapa treatment group than in the control group. RT-PCR revealed that the expression levels of p53, Bax and Beclin 1 were up-regulated in a dose-dependent manner, indicating that Beclin 1 was involved in Rapa induced autophagy and Rapa induced apoptosis as well as p53 up-regulation in PC-2 cells. The results demonstrated that Rapa could effectively inhibit proliferation and induce apoptosis and autophagy in PC-2 cells.

Cancer Stem Cells, EMT, and Developmental Pathway Activation in Pancreatic Tumors

Pancreatic cancer is a disease with remarkably poor patient survival rates. The frequent presence of metastases and profound chemoresistance pose a severe problem for the treatment of these tumors. Moreover, cross-talk between the tumor and the local micro-environment contributes to tumorigenicity, metastasis and chemoresistance. Compared to bulk tumor cells, cancer stem cells (CSC) have reduced sensitivity to chemotherapy. CSC are tumor cells with stem-like features that possess the ability to self-renew, but can also give rise to more differentiated progeny. CSC can be identified based on increased in vitro spheroid- or colony formation, enhanced in vivo tumor initiating potential, or expression of cell surface markers. Since CSC are thought to be required for the maintenance of a tumor cell population, these cells could possibly serve as a therapeutic target. There appears to be a causal relationship between CSC and epithelial-to-mesenchymal transition (EMT) in pancreatic tumors. The occurrence of EMT in pancreatic cancer cells is often accompanied by re-activation of developmental pathways, such as the Hedgehog, WNT, NOTCH, and Nodal/Activin pathways. Therapeutics based on CSC markers, EMT, developmental pathways, or tumor micro-environment could potentially be used to target pancreatic CSC. This may lead to a reduction of tumor growth, metastatic events, and chemoresistance in pancreatic cancer.

The role of chemoradiation for patients with resectable or potentially resectable pancreatic cancer

Conflicting data and substantial controversy exist regarding optimal adjuvant treatment for those patients with resectable or potentially resectable adenocarcinoma of the pancreas. Despite improvements in short-term surgical outcomes, the use of newer chemotherapeutic agents, development of targeted agents and more precise delivery of radiation, the 5-year survival rates for early-stage patients remains less than 25%. This article critically reviews the existing data for various adjuvant treatment approaches for patients with surgically resectable pancreatic cancer. Our review confirms that despite several randomized clinical trials, the optimal adjuvant treatment approach for these patients remains unclear.

A case of pancreatic cancer after heart transplantation

Malignancy is not uncommon with immunosuppressive therapy, but pancreatic cancer is infrequently complicated in recipients of heart transplantation. Here we report a transplant case diagnosed with pancreatic cancer 4 years and 8 months after the heart transplantation. We changed the immunosuppressive regimen after the malignancy was detected, and administered everolimus along with chemotherapy using S-1, an oral fluoropyrimidine prodrug. The patient lived for 8 months after the diagnosis, and received metallic stenting for the biliary and duodenal obstruction. Also, to the best of our knowledge, this is the first report about chemotherapy and endoscopic intervention for pancreatic cancer in a heart transplantation patient.

Current clinical development of PI3K pathway inhibitors in glioblastoma

Glioblastoma (GBM) is the most common and lethal primary malignant tumor of the central nervous system, and effective therapeutic options are lacking. The phosphatidylinositol 3-kinase (PI3K) pathway is frequently dysregulated in many human cancers, including GBM. Agents inhibiting PI3K and its effectors have demonstrated preliminary activity in various tumor types and have the potential to change the clinical treatment landscape of patients with solid tumors. In this review, we describe the activation of the PI3K pathway in GBM, explore why inhibition of this pathway may be a compelling therapeutic target for this disease, and provide an update of the data on PI3K inhibitors in clinical trials and from earlier investigation.

Activated mTOR/P70S6K signaling pathway is involved in insulinoma tumorigenesis

BACKGROUND

Insulinoma was a rare tumor and its pathogenesis was poorly understood. There had no study that focused on the role of mTOR signaling pathway in insulinoma tumorigenesis.

MATERIALS AND METHODS

Expression of p-mTOR and its downstream p-P70S6K in insulinoma and normal pancreatic tissue was evaluated by immunohistochemical staining and Western blotting. In vitro study, an insulinoma cell line (INS-1) was treated with inhibitors of mTOR (rapamycin) or dual PI3K/mTOR inhibitor (NVP-BEZ235), RT-PCR, and Western blotting were applied to evaluate their influence on the expression of mTOR and P70S6K. Cell proliferation was evaluated by MTT test, cell cycle and apoptosis were analyzed by flow cytometry, insulin secretion level was evaluated by GSIS method.

RESULTS

Positive expression of p-mTOR and p-P70S6K was much higher in insulinoma tumor specimens than the normal pancreatic islet (P < 0.05). mTOR inhibitors can induce decreased expression of mTOR and P70S6K, which resulting in inhibiting INS-1 cell proliferation, insulin secretion and inducing apoptosis. NVP-BEZ235 had better influence on inhibiting the cell proliferation and inducing apoptosis than rapamycin.

CONCLUSION

mTOR/P70S6K signaling pathway is involved in tumorigenesis of insulinoma, NVP-BEZ235 and rapamycin offer a promising role as novel drugs in treatment of insulinoma.

Akt/mTOR signaling pathway is crucial for gemcitabine resistance induced by Annexin II in pancreatic cancer cells

BACKGROUND

Although gemcitabine has been widely used as a first-line chemo reagent for patients with pancreatic cancer, the response rate remains low. We previously identified Annexin II as a factor involved in gemcitabine resistance against pancreatic cancer. The aims of this study were to elucidate the signaling mechanism by which Annexin II induces gemcitabine resistance and to develop a new therapy that overcomes the resistance against gemcitabine.

METHODS

We compared the specific profiles of 12 targeted phosphorylated (p-) signaling proteins in gemcitabine-resistant (GEM-) and its wild-type pancreatic cancer cell lines (MIA PaCa-2) using the Bio-Plex assay system. We also evaluated the expression levels of Annexin II and two phosphoproteins, which showed different expressions in these two cell lines, by immunohistochemistry.

RESULTS

Annexin II overexpression was significantly associated with rapid recurrence after gemcitabine-adjuvant chemotherapy in patients with resected pancreatic cancer (P < 0.05). Bio-Plex analysis showed up-regulation of p-Akt in GEM-MIA PaCa-2 cells in which Annexin II is highly expressed. The expression level of p-Akt was significantly correlated with that of the downstream protein, p-mTOR, in pancreatic cancer tissues. Inhibition of mTOR phosphorylation canceled gemcitabine resistance in GEM-MIA PaCa-2 cells.

CONCLUSIONS

The Akt/mTOR pathway is involved in mechanisms of gemcitabine resistance induced by Annexin II in pancreatic cancer cells. This indicates that combination therapy with the mTOR inhibitor may overcome gemcitabine resistance. Annexin II as an indicator for selection of gemcitabine resistance could thus be applied to the development of novel tailor-made approaches for pancreatic cancer treatment.

Pancreatic cancer: medical management (novel chemotherapeutics)

Pancreatic adenocarcinoma is the fourth leading cause of cancer death and has an extremely poor prognosis: The 5-year survival probability is less than 5% for all stages. The only chance for cure or longer survival is surgical resection; however, only 10% to 20% of patients have resectable disease. Although surgical techniques have improved, most who undergo complete resection experience a recurrence. Adjuvant systemic therapy reduces the recurrence rate and improves outcomes. There is a potential role for radiation therapy as part of treatment for locally advanced disease, although its use in both the adjuvant and neoadjuvant settings remains controversial. Palliative systemic treatment is the only option for patients with metastatic disease. To date, however, only the gemcitabine plus erlotinib combination, and recently the FOLFIRINOX regimen, have been associated with relatively small but statistically significant improvements in OS when compared directly with gemcitabine alone. Although several meta-analyses have suggested a benefit associated with combination chemotherapy, whether this benefit is clinically meaningful remains unclear, particularly in light of the enhanced toxicity associated with combination regimens. There is growing evidence that the exceptionally poor prognosis in PC is caused by the tumor's characteristic abundant desmoplastic stroma that plays a critical role in tumor cell growth, invasion, metastasis, and chemoresistance. Carefully designed clinical trials that include translational analysis will provide a better understanding of the tumor biology and its relation to the host stromal cells. Future directions will involve testing of new targeted agents, understanding the pharmacodynamics of our current targeted agents, searching for predictive and prognostic biomarkers, and exploring the efficacy of different combinations strategies.

Therapy innovation for the treatment of pancreatic neuroendocrine tumors

INTRODUCTION

Traditional therapeutic approaches for patients with advanced neuroendocrine tumors (NETs) have included treatment with somatostatin analogs, hepatic-directed therapies, interferon and cytotoxic chemotherapy. Current knowledge about biological behavior of pancreatic neuroendocrine tumors (pNETs) has increased in the last decade, and some studies have been conducted to translate in the clinical setting. Among several molecular agents investigated in patients with progressive pNETs, everolimus and sunitinib have been studied in large Phase III trials. Both have produced significant benefit, with improvement in progression-free survival. These results were published last year by NEJM and were updated at the ASCO Annual Meeting in June 2011.

AREAS COVERED

This review focuses on the potential molecular targets in pancreatic NETs in the light of recent advances. Furthermore, it summarizes the available data for targeted agents from Phase II and III trials open to patients with this tumor.

EXPERT OPINION

These new agents are likely to play an increasingly important role in the future management of advanced pNETs. Their use in earlier phases of the disease could improve clinical outcome, avoiding side effects of the more toxic chemotherapy. The challenge in medical treatment of pNET is to define the patients who can benefit from this innovative therapy; future research should be directed to find predictive markers for response to the targeted agent.

A phase I/II, non-randomized, feasibility/safety and efficacy study of the combination of everolimus, cetuximab and capecitabine in patients with advanced pancreatic cancer

BACKGROUND

Improvements in knowledge of molecular mechanisms in cancer are the basis for new studies combining chemotherapy with targeted drugs. Inhibition of the epidermal growth factor receptor (EGFR) by erlotinib or cetuximab has limited or no activity, respectively, in pancreatic cancer. The crosstalk between EGFR and mammalian target of rapamycin (mTOR) pathways is a potential mechanism of resistance; therefore we conducted a study to explore safety and efficacy of multiple pathway inhibition by cetuximab and everolimus in combination with capecitabine.

METHODS

Safety and efficacy of fixed standard dose cetuximab in combination with various dose levels of everolimus (5-10 mg/day) and capecitabine (600-800 mg/m(2) bid, 2 weeks every 3 weeks) were investigated in a phase I/II study in patients with advanced pancreatic cancer. The primary endpoint was objective response.

RESULTS

Sixteen patients were treated in the phase I part at two dose levels. Mucositis, rash and hand-foot syndrome were dose-limiting toxicities. Dose level 1 (everolimus 5 mg/day, capecitabine 600 mg/m(2) bid for 2 weeks every 3 weeks and cetuximab 250 mg/m(2) weekly) was considered the maximum tolerated dose (MTD). Of 31 patients in the phase II part, partial response was documented in two patients (6.5%) and five (16.1%) had stable disease. Median overall survival was 5.0 months (CI 3.1-6.8).

CONCLUSION

The schedule of capecitabine, everolimus and cetuximab resulted in considerable epidermal and mucosal toxicities and prevented escalation to optimal dose levels. Because of toxicity and low efficacy this treatment combination cannot be recommended for treatment in pancreatic cancer patients.

Aberrant activation of the mTOR pathway and anti-tumour effect of everolimus on oesophageal squamous cell carcinoma

Background:

The mammalian target of rapamycin (mTOR) protein is important for cellular growth and homeostasis. The presence and prognostic significance of inappropriate mTOR activation have been reported for several cancers. Mammalian target of rapamycin inhibitors, such as everolimus (RAD001), are in development and show promise as anti-cancer drugs; however, the therapeutic effect of everolimus on oesophageal squamous cell carcinoma (OSCC) remains unknown.

Methods:

Phosphorylation of mTOR (p-mTOR) was evaluated in 167 resected OSCC tumours and 5 OSCC cell lines. The effects of everolimus on the OSCC cell lines TE4 and TE11 in vitro and alone or in combination with cisplatin on tumour growth in vivo were evaluated.

Results:

Mammalian target of rapamycin phosphorylation was detected in 116 tumours (69.5%) and all the 5 OSCC cell lines. Everolimus suppressed p-mTOR downstream pathways, inhibited proliferation and invasion, and induced apoptosis in both TE4 and TE11 cells. In a mouse xenograft model established with TE4 and TE11 cells, everolimus alone or in combination with cisplatin inhibited tumour growth.

Conclusion:

The mTOR pathway was aberrantly activated in most OSCC tumours. Everolimus had a therapeutic effect both as a single agent and in combination with cisplatin. Everolimus could be a useful anti-cancer drug for patients with OSCC.

K-Ras mutation-mediated IGF-1-induced feedback ERK activation contributes to the rapalog resistance in pancreatic ductal adenocarcinomas

Mammalian target of rapamycin complex 1 (mTORC1) is frequently activated in human cancers; however, clinical trials of rapalog (the mTORC1 inhibitors) have shown that pancreatic ductal adenocarcinomas (PDACs) resist to the treatment. Rapalog treatment activated the extracellular signal-regulated kinase (ERK) pathway in K-Ras mt PDAC cells. K-Ras knockdown abolished the insulin-like growth factor-1 (IGF-1)-induced ERK pathway in the K-Ras mt PDAC cells and enhanced the therapeutic efficacy of everolimus in treating K-Ras mt PDAC cells-derived mouse xenografts. The results indicate that targeting of K-Ras mutation may lead to the development of therapies that overcome rapalog resistance in PDAC.

The mTOR signalling pathway in human cancer

The conserved serine/threonine kinase mTOR (the mammalian target of rapamycin), a downstream effector of the PI3K/AKT pathway, forms two distinct multiprotein complexes: mTORC1 and mTORC2. mTORC1 is sensitive to rapamycin, activates S6K1 and 4EBP1, which are involved in mRNA translation. It is activated by diverse stimuli, such as growth factors, nutrients, energy and stress signals, and essential signalling pathways, such as PI3K, MAPK and AMPK, in order to control cell growth, proliferation and survival. mTORC2 is considered resistant to rapamycin and is generally insensitive to nutrients and energy signals. It activates PKC-α and AKT and regulates the actin cytoskeleton. Deregulation of multiple elements of the mTOR pathway (PI3K amplification/mutation, PTEN loss of function, AKT overexpression, and S6K1, 4EBP1 and eIF4E overexpression) has been reported in many types of cancers, particularly in melanoma, where alterations in major components of the mTOR pathway were reported to have significant effects on tumour progression. Therefore, mTOR is an appealing therapeutic target and mTOR inhibitors, including the rapamycin analogues deforolimus, everolimus and temsirolimus, are submitted to clinical trials for treating multiple cancers, alone or in combination with inhibitors of other pathways. Importantly, temsirolimus and everolimus were recently approved by the FDA for the treatment of renal cell carcinoma, PNET and giant cell astrocytoma. Small molecules that inhibit mTOR kinase activity and dual PI3K-mTOR inhibitors are also being developed. In this review, we aim to survey relevant research, the molecular mechanisms of signalling, including upstream activation and downstream effectors, and the role of mTOR in cancer, mainly in melanoma.

Current knowledge on pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer death with a median survival of 6 months and a dismal 5-year survival rate of 3-5%. The development and progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways. Therefore, the strategies targeting these molecules as well as their downstream signaling could be promising for the prevention and treatment of pancreatic cancer. However, although targeted therapies for pancreatic cancer have yielded encouraging results in vitro and in animal models, these findings have not been translated into improved outcomes in clinical trials. This failure is due to an incomplete understanding of the biology of pancreatic cancer and to the selection of poorly efficient or imperfectly targeted agents. In this review, we will critically present the current knowledge regarding the molecular, biochemical, clinical, and therapeutic aspects of pancreatic cancer.

Transient mTOR inhibition facilitates continuous growth of liver tumors by modulating the maintenance of CD133+ cell populations

The mammalian target of the rapamycin (mTOR) pathway, which drives cell proliferation, is frequently hyperactivated in a variety of malignancies. Therefore, the inhibition of the mTOR pathway has been considered as an appropriate approach for cancer therapy. In this study, we examined the roles of mTOR in the maintenance and differentiation of cancer stem-like cells (CSCs), the conversion of conventional cancer cells to CSCs and continuous tumor growth in vivo. In H-Ras-transformed mouse liver tumor cells, we found that pharmacological inhibition of mTOR with rapamycin greatly increased not only the CD133+ populations both in vitro and in vivo but also the expression of stem cell-like genes. Enhancing mTOR activity by over-expressing Rheb significantly decreased CD133 expression, whereas knockdown of the mTOR yielded an opposite effect. In addition, mTOR inhibition severely blocked the differentiation of CD133+ to CD133- liver tumor cells. Strikingly, single-cell culture experiments revealed that CD133- liver tumor cells were capable of converting to CD133+ cells and the inhibition of mTOR signaling substantially promoted this conversion. In serial implantation of tumor xenografts in nude BALB/c mice, the residual tumor cells that were exposed to rapamycin in vivo displayed higher CD133 expression and had increased secondary tumorigenicity compared with the control group. Moreover, rapamycin treatment also enhanced the level of stem cell-associated genes and CD133 expression in certain human liver tumor cell lines, such as Huh7, PLC/PRC/7 and Hep3B. The mTOR pathway is significantly involved in the generation and the differentiation of tumorigenic liver CSCs. These results may be valuable for the design of more rational strategies to control clinical malignant HCC using mTOR inhibitors.

Targeting notch pathway enhances rapamycin antitumor activity in pancreas cancers through PTEN phosphorylation

BACKGROUND

Pancreas cancer is one of most aggressive human cancers with the survival rate for patients with metastatic pancreas cancer at 5-6 months. The poor survival demonstrates a clear need for better target identification, drug development and new therapeutic strategies. Recent discoveries have shown that the role for Notch pathway is important in both development and cancer. Its contribution to oncogenesis also involves crosstalks with other growth factor pathways, such as Akt and its modulator, PTEN. The mounting evidence supporting a role for Notch in cancer promotion and survival suggests that targeting this pathway alone or in combination with other therapeutics represents a promising therapeutic strategy.

RESULTS

Using a pancreas cancer tissue microarray, we noted that Jagged1, Notch3 and Notch4 are overexpressed in pancreas tumors (26%, 84% and 31% respectively), whereas Notch1 is expressed in blood vessels. While there was no correlation between Notch receptor expression and survival, stage or tumor grade, Notch3 was associated with Jagged1 and EGFR expression, suggesting a unique relationship between Notch3 and Jagged1. Inhibition of the Notch pathway genetically and with gamma-secretase inhibitor (GSI) resulted in tumor suppression and enhanced cell death. The observed anti-tumor activity appeared to be through Akt and modulation of PTEN phosphorylation. We discovered that transcriptional regulation of RhoA by Notch is important for PTEN phosphorylation. Finally, the mTOR inhibitor Rapamycin enhanced the effect of GSI on RhoA expression, resulting in down regulation of phospho-Akt and increased in vitro tumor cytotoxity.

CONCLUSIONS

Notch pathway plays an important role in maintaining pancreas tumor phenotype. Targeting this pathway represents a reasonable strategy for the treatment of pancreas cancers. Notch modulates the Akt pathway through regulation of PTEN phosphorylation, an observation that has not been made previously. Furthermore, we discovered that this regulation is dependent on RhoA/Rock1 activation. Enhanced phospho-Akt suppression when GSI is combined with rapamycin suggests that targeting both pathways will lead to a greater efficacy in the treatment of patients with pancreas cancer.

Pharmacokinetic drug interaction between AEE788 and RAD001 causing thrombocytopenia in patients with glioblastoma

PURPOSE

Treating glioblastoma through the simultaneous inhibition of multiple transduction pathways may prove more effective than single-pathway inhibition. We evaluated the safety, biologic activity, and pharmacokinetic profile of oral AEE788, a selective inhibitor of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF), plus oral RAD001, a mammalian target of rapamycin inhibitor, in glioblastoma patients.

METHODS

This phase IB/II, open-label, multicenter, 2-arm, dose-escalation study enrolled adult glioblastoma patients at first or second recurrence/relapse. Primary objective was to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of AEE788 combined with RAD001. Secondary objectives included determining the safety/tolerability, pharmacokinetics, pharmacodynamics, and antitumor activity of the combination.

RESULTS

Sixteen patients were enrolled (AEE788 200 mg/day + RAD001 5 mg/day, 2 patients; AEE788 150 mg/day + RAD001 5 mg every other day [qod], 14); all patients discontinued the study most commonly because of disease progression. Four patients experienced DLT (AEE788 200 mg/day + RAD001 5 mg/day, 1 patient; AEE788 150 mg/day + RAD001 5 mg qod, 3). Both patients receiving AEE788 (200 mg/day) plus RAD001 (5 mg/day) experienced clinically significant thrombocytopenia requiring a dose reduction/interruption. AEE788 appeared to inhibit the metabolism of RAD001. The study was terminated prematurely before an MTD was determined because of safety findings in other studies evaluating AEE788 monotherapy.

CONCLUSIONS

The coadministration of AEE788 and RAD001 in glioblastoma patients caused a clinically significant thrombocytopenia and a higher-than-expected RAD001 area under the curve concentration when dosed at 200 and 5 mg/day, respectively. After a dose reduction to AEE788 (150 mg/day) and RAD001 (5 mg qod), the combination appeared to be better tolerated.

Defining new paradigms for the treatment of pancreatic cancer

Pancreatic cancer (PC) is the fourth leading cause of cancer death in the United States. Despite significant improvement in understanding disease biology, the 5-year survival rates remain less than 5%. Targeted agents failed to add any meaningful survival benefit in this patient population despite very promising pre-clinical data. The new paradigm for the treatment of PC must emphasize validation of targeted agents in the appropriate pre-clinical models, identification of predictive markers for disease response, and extending range of targets into cancer stem cells and tumor microenvironment. It is also necessary to perform studies that are designed to address the various stages of disease with respect to study endpoints and application of a multimodality approach in management. Phase III trials should only be considered when a strong efficacy signal is demonstrated in phase II studies that is based on a survival endpoint. This review will focus on the development of novel treatments in pancreas cancer and the proposed design of future clinical trials.

Phase I and pharmacokinetic study of capecitabine and the oral mTOR inhibitor everolimus in patients with advanced solid malignancies

Background Everolimus is an oral mTOR-inhibitor. Preclinical data show synergistic effects of mTOR inhibition in combination with 5-fluorouracil-based anticancer therapy. The combination of everolimus with capecitabine seems therefore an attractive new, orally available, treatment regimen. Patients and methods Safety, preliminary efficacy and pharmacokinetics of everolimus in combination with capecitabine were investigated in patients with advanced solid malignancies. Patients were treated with fixed dose everolimus 10 mg/day continuously, plus capecitabine bid for 14 days in three-weekly cycles. Dose escalation of capecitabine proceeded according to the standard 3 × 3 phase I design in four predefined dose levels (500–1,000 mg/m² bid). Results In total, 18 patients were enrolled. Median (range) treatment duration with everolimus was 70 days (21–414). Capecitabine 1,000 mg/m² bid combined with 10 mg/day everolimus was declared the maximum tolerated dose, at which level one patient developed dose-limiting toxicity (stomatitis grade 3). Drug-related adverse events were mostly grade ≤2 and included mainly fatigue (56%), stomatitis (50%), and hand-foot syndrome (33%). Partial response was documented in three patients, and four had stable disease. There was no pharmacokinetic interaction between everolimus and capecitabine. Conclusion Everolimus 10 mg/day continuously combined with capecitabine 1,000 mg/m² bid for 14 days every 3 weeks is a patient-convenient, safe and tolerable oral treatment regimen. This is the first study to demonstrate feasibility of this combination at doses with proven single agent efficacy in a number of tumors. Prolonged clinical benefit was observed in an encouraging 39% of patients with advanced solid malignancies.

Role of mTOR signaling in tumor cell motility, invasion and metastasis

Tumor cell migration and invasion play fundamental roles in cancer metastasis. The mammalian target of rapamycin (mTOR), a highly conserved and ubiquitously expressed serine/threonine (Ser/Thr) kinase, is a central regulator of cell growth, proliferation, differentiation and survival. Recent studies have shown that mTOR also plays a critical role in the regulation of tumor cell motility, invasion and cancer metastasis. Current knowledge indicates that mTOR functions as two distinct complexes, mTORC1 and mTORC2. mTORC1 phosphorylates p70 S6 kinase (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1), and regulates cell growth, proliferation, survival and motility. mTORC2 phosphorylates Akt, protein kinase C α (PKCα) and the focal adhesion proteins, and controls the activities of the small GTPases (RhoA, Cdc42 and Rac1), and regulates cell survival and the actin cytoskeleton. Here we briefly review recent knowledge of mTOR complexes and the role of mTOR signaling in tumor cell migration and invasion. We also discuss recent efforts about the mechanism by which rapamycin, a specific inhibitor of mTOR, inhibits cell migration, invasion and cancer metastasis.

Everolimus resolving hypoglycemia, producing hyperglycemia, and necessitating insulin use in a patient with diabetes and nonresectable malignant insulinoma

OBJECTIVE

To present a case of management of refractory hypoglycemia due to malignant insulinoma with use of everolimus, resulting in recurrent insulin-requiring diabetes.

METHODS

This report describes a case of a nonresectable malignant insulinoma in a 78-year-old patient with long-standing type 2 diabetes mellitus. Endogenous hyperinsulinism was confirmed by a fasting test, which revealed a glucose level of 35 mg/dL and an insulin value of 23.7 μIU/mL. Endoscopic ultrasonography, magnetic resonance imaging, and computed tomography identified a pancreatic mass, infiltration of the superior mesenteric vein, and metastatic lesions in the liver.

RESULTS

After chemoembolization of the metastatic lesions, hypoglycemia recurred, despite combined treatment with somatostatin analogues, dexamethasone, and diazoxide. Everolimus, an orally administered mammalian target of rapamycin, was used at a daily dose of 5 mg. After 6 months, the hypoglycemia was controlled, and the patient presented with a C-peptide level of 0.2 ng/mL and secondary hyperglycemia that necessitated insulin treatment.

CONCLUSION

The orally administered drug everolimus controlled hypoglycemia due to a malignant insulinoma in a patient with prior insulin-requiring diabetes. Secondary hyperglycemia was an acceptable drug effect (to the patient and managing physicians), in light of the complex and often poorly tolerated treatments available for this rare condition.

From cancer metabolism to new biomarkers and drug targets

Great interest is presently given to the analysis of metabolic changes that take place specifically in cancer cells. In this review we summarize the alterations in glycolysis, glutamine utilization, fatty acid synthesis and mitochondrial function that have been reported to occur in cancer cells and in human tumors. We then propose considering cancer as a system-level disease and argue how two hallmarks of cancer, enhanced cell proliferation and evasion from apoptosis, may be evaluated as system-level properties, and how this perspective is going to modify drug discovery. Given the relevance of the analysis of metabolism both for studies on the molecular basis of cancer cell phenotype and for clinical applications, the more relevant technologies for this purpose, from metabolome and metabolic flux analysis in cells by Nuclear Magnetic Resonance and Mass Spectrometry technologies to positron emission tomography on patients, are analyzed. The perspectives offered by specific changes in metabolism for a new drug discovery strategy for cancer are discussed and a survey of the industrial activity already going on in the field is reported.

Inhibition of mTOR by temsirolimus contributes to prolonged survival of mice with pleural dissemination of non-small-cell lung cancer cells

Temsirolimus (CCI-779), a recently synthesized analogue of rapamycin, specifically inhibits mTOR and has been approved for clinical use in renal cell carcinoma. Recent reports have indicated the growth inhibitory effect of temsirolimus in some cancers including non-small-cell lung carcinoma (NSCLC). In this study, we aimed to explore the potential therapeutic use of temsirolimus as a treatment for NSCLC. Using cultured NSCLC cells (A549, H1299, and H358), we determined the effect of temsirolimus on cell proliferation and its antitumor effects on subcutaneous tumors, as well as its contribution to the survival of mice having pleural dissemination of cancer cells, mimicking advanced NSCLC. Temsirolimus suppressed proliferation of NSCLC cells in a dose-dependent manner, with an IC(50) of <1 nM. Western blot analysis revealed that temsirolimus treatment specifically inhibited the phosphorylation of mTOR and its downstream effectors in 1 h, accompanied by an increased cell population in the G(0) /G(1) phase, but according to flow cytometry, the cell population did not increase in the sub-G(0) phase. When NSCLC subcutaneous tumor-bearing mice were treated with temsirolimus, tumor volume was significantly reduced (tumor volume on day 35: vehicle vs temsirolimus = 1239 vs 698 cm(3) ; P < 0.05). Furthermore, prolonged survival was observed in pleural disseminated tumor-bearing mice with temsirolimus treatment (median survival: vehicle vs temsirolimus = 53.5 vs 72.5 days; P < 0.05). These results suggest that temsirolimus could be useful for NSCLC treatment, due to its antiproliferative effect, and could be a potential treatment for advanced NSCLC, giving prolonged survival.

Clinical activity of mammalian target of rapamycin inhibitors in solid tumors

The phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway is vital for cell metabolism, growth, and proliferation. mTOR is frequently upregulated in many tumor types and hence has become an important target in cancer treatment. Sirolimus and its derivatives (rapalogs) interact with the intracellular receptor FK506 binding protein 12 (FKBP12), forming a complex with high affinity for mTOR and thus disrupting its activity. Rapalogs are being evaluated extensively in cancer patients with different formulations and schedules. Significant clinical activity has led to their approval for the treatment of kidney cancer, mantle cell lymphoma, and subependymal giant cell astrocytoma; however, despite increasing knowledge about cancer cell biology, their activity in other malignancies is unclear. Further research is needed to identify optimal dosage, administration and targeted combination as well as the subset of patients likely to respond to mTOR/PI3K inhibition. This review focuses on a discussion of the pathway, its implications in cancer biology and results of clinical trials of rapalogs alone or in combination, organizing them by common malignancy type.