mTOR Pathway Components Research Articles

The placental mTOR-pathway: correlation with early growth trajectories following intrauterine growth restriction?

Idiopathic intrauterine growth restriction (IUGR) is a result of impaired placental nutrient supply. Newborns with IUGR exhibiting postnatal catch-up growth are of higher risk for cardiovascular and metabolic co-morbidities in adult life. Mammalian target of rapamycin (mTOR) was recently shown to function as a placental nutrient sensor. Thus, we determined possible correlations of members of the placental mTOR signaling cascade with auxologic parameters of postnatal growth. The protein expression and activity of mTOR-pathway signaling components, Akt, AMP-activated protein kinase α, mTOR, p70S6kinase1 and insulin receptor substrate-1 were analysed via western blotting in IUGR v. matched appropriate-for-gestational age (AGA) placentas. Moreover, mTOR was immunohistochemically stained in placental sections. Data from western blot analyses were correlated with retrospective auxological follow-up data at 1 year of age. We found significant catch-up growth in the 1st year of life in the IUGR group. MTOR and its activated form are immunohistochemically detected in multiple placental compartments. We identified correlations of placental mTOR-pathway signaling components to auxological data at birth and at 1 year of life in IUGR. Analysis of the protein expression and phosphorylation level of mTOR-pathway components in IUGR and AGA placentas postpartum, however, did not reveal pathognomonic changes. Our findings suggest that the level of activated mTOR correlates with early catch-up growth following IUGR. However, the complexity of signals converging at the mTOR nexus and its cellular distribution pattern seem to limit its potential as biomarker in this setting.

Neuroendocrine differentiation: The mysterious fellow of colorectal cancer.

Neuroendocrine differentiation in sporadic colorectal cancer has been recognized since decades, but its clinical impact is still controversially discussed. Detailed parameter analyses hint at the possibility that probably not neuroendocrine differentiation itself, but its association with poor grade of tumor differentiation, lymph node metastases, distant metastases and other unfavorable features contribute to worse clinical outcome. However, other studies deny a relationship between neuroendocrine differentiation and prognosis of colorectal cancer. This review elucidates, whether new insights into the origin of neuroendocrine differentiation in the intestinal epithelium, its regulation by mTOR pathway components and its possible link to the intestinal stem cell compartment could determine a role of neuroendocrine cells as prognostic marker and putative therapeutic target in sporadic colorectal cancer.

Targeting the mTOR signaling pathway in neuroendocrine tumors.

Opinion statementNeuroendocrine tumors (NETs) are a heterogeneous group of malignancies characterized by variable but most often indolent biologic behavior. Well-differentiated NETs can be broadly classified as either carcinoid or pancreatic NET. Although they have similar characteristics on routine histologic evaluation, the 2 tumor subtypes have different biology and respond differently to treatment, with most therapeutic agents demonstrating higher response rates in pancreatic NETs compared with carcinoid. Until recently, systemic treatment options for patients with advanced NETs were limited. However, improvements in our understanding of signaling pathways involved in the pathogenesis, growth, and spread of NETs have translated into an expansion of treatment options. Aberrant signaling through the mechanistic pathway of rapamycin (mTOR) pathway has been implicated in neuroendocrine tumorigenesis. Additionally, altered expression of mTOR pathway components has been observed in NETs and has been associated with clinical outcomes. Targeting the mTOR pathway has emerged as an effective treatment strategy in the management of advanced NETs. In a randomized, placebo-controlled study of patients with advanced pancreatic NET, treatment with the mTOR inhibitor everolimus was associated with improved progression-free survival (PFS). Largely based upon these data, everolimus has been approved in the United States and Europe for the treatment of patients with advanced pancreatic NET. The activity of everolimus remains under investigation in patients with carcinoid tumors. In a randomized study of patients with advanced carcinoid tumors associated with carcinoid syndrome, the addition of everolimus to octreotide was associated with improved PFS compared with octreotide. However, the results did not meet the prespecified level of statistical significance based on central review of radiographic imaging. Results from a randomized study examining the efficacy of everolimus in patients with nonfunctional gastrointestinal and lung NETs are awaited. In addition, further investigation is needed to determine whether primary tumor site or other clinical and molecular factors can impact response to mTOR inhibition. Although everolimus can slow tumor progression, significant tumor reduction is rarely obtained. Targeting multiple signaling pathways is a treatment strategy that may provide better tumor control and overcome resistance mechanisms involved with targeting a single pathway. Results of ongoing and future studies will provide important information regarding the added benefit of combining mTOR inhibitors with other targeted agents, such as VEGF pathway inhibitors, and cytotoxic chemotherapy in the treatment of advanced NETs.

The combination of rapamycin and MAPK inhibitors enhances the growth inhibitory effect on Nara-H cells

The inhibition of the mammalian target of rapamycin (mTOR) signaling pathway promotes the initiation of autophagy, and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase (ERK) is well known to induce autophagy. Autophagy is a self-defense mechanism of cancer cells that are subjected to antitumor agents, and blocking autophagy can trigger apoptosis. In the present study, we demonstrate that an mTOR inhibitor, rapamycin, induces autophagy in the Nara-H malignant fibrous histiocytoma (MFH) cell line through the activation of ERK1/2. Rapamycin-induced apoptosis was enhanced following the inhibition of the MEK/ERK pathway. In the Nara-H cells, we examined the effects of rapamycin treatment on cell proliferation and on the phosphorylation of the mTOR pathway components and autophagy by western blot analysis. Furthermore, we examined the effects of rapamycin with or without the MEK inhibitor, U0126, on the induction of apoptosis by using fluorescence microscopy. Rapamycin inhibited Nara-H cell proliferation and decreased the phosphorylation of the mTOR pathway in the Nara-H cells. Rapamycin induced the apoptosis of Nara-H cells, and this apoptosis was enhanced by U0126. Simultaneously, phospho-ERK1/2 was activated by rapamycin. The present study demonstrates that rapamycin induces autophagy in Nara-H cells by activating the MEK/ERK signaling pathway, and the rapamycin-induced apoptosis can be enhanced by the MEK inhibitor, U0126. These results suggest that self-protective mechanisms involving mTOR inhibitors in Nara-H cells are prevented by the inhibition of the MEK/ERK pathway. The combination of an mTOR inhibitor (e.g., rapamycin) and an MEK inhibitor (e.g., U0126) may offer effective treatment for MFH, as this combination effectively activates apoptotic pathways.

Prognostic Significance of MTOR Pathway Component Expression in Neuroendocrine Tumors

Clinical studies have implicated the mechanistic target of rapamycin (serine/threonine kinase; MTOR) pathway in the regulation of neuroendocrine tumor (NET) growth. We explored whether expression of MTOR pathway components has prognostic significance in NET patients. We evaluated immunohistochemical expression of MTOR and phospho (p) -MTOR; its downstream targets RPS6KB1, RPS6, and EIF4EBP1; and its upstream regulators, in a cohort of 195 archival neuroendocrine tumors. We correlated expression levels with clinical outcomes, after adjusting for other prognostic variables. We observed anticipated correlations between expression of upstream components of the MTOR pathway and their downstream targets. Expression of PIK3CA, MTOR, or p-EIF4EBP1 was associated with high MKI67 (Ki-67) labeling index. We failed to identify clinical correlations associated with expression of the upstream regulators TSC1, TSC2, AKT, p-AKT, PDPK1, PTEN, PIK3R1, or PIK3CA. In contrast, high expression of MTOR or its activated downstream targets p-RPS6KB1, p-RPS6, or p-EIF4EBP1 was associated with adverse clinical outcomes. Our observations suggest that expression of MTOR or its downstream targets may be adverse prognostic factors in neuroendocrine tumors.

Novel stratification of the recurrence risk following surgical extirpation of clear cell renal cell carcinoma using tissue biomarkers in the mammalian target of rapamycin pathway.

4581 Background: Aberrant activation of the mammalian target of rapamycin (mTOR) pathway promotes invasiveness and metastatic potential in a variety of malignancies. The aim of the present study was to evaluate the association of altered expression of mTOR pathway components with recurrence outcome in non-metastatic clear cell renal cell carcinoma (ccRCC) patients. Methods: Immunohistochemistry for phos-S6, phos-mTOR, mTOR, phos-AKT, HIF-1α, RAPTOR, PTEN, PI3K, and phos-4EBP1 was performed on tissue microarrays of patients treated for non-metastatic kidney cancer between 1997-2010. Patients were defined as having a low (<) or high risk (≥) of nomogram predicted recurrence (2001 MSKCC RCC post-op) using an 8% cutoff. The relationship between individual marker expression, as well as combined marker score (low, intermediate and high defined as ≤ 3, 4-5, >5 altered biomarkers; respectively) with the actual and predicted relapse rates was assessed. Results: The study included 419 non- metastatic ccRCC patients (pT1-T2 79.5%, pT3-T4 20.5%, Fuhrman nuclear grade 1-2 in 69%, 3-4 in 31%). 219 and 200 patients had low (<8%) and high (≥8%) nomogram-predicted 5-year risk of recurrence respectively. With a median follow-up of 2.2 years, recurrences were detected in 5 (2.3%) of the predicted low risk and 30 (15%) of the predicted high risk patients. mTOR pathway biomarker profiles were not predictive for patients at low predicted risk of recurrences. For patients at high predicted risk of recurrence, low, intermediate and high combined marker scores were found in 84 (42%), 79 (39.5%), and 37 (18.5%), respectively. The actual rates of recurrence were noted for 8.3% of low, 13.9% of intermediate and 32.4% of high combined marker score in a statistically significant distribution (p=0.027). Conclusions: The cumulative number of aberrantly expressed mTOR biomarkers correlates with a higher rate of recurrence. The combined marker score may help further stratify patients with high nomogram predicted risk of recurrence. Our data supports prospective evaluation of these biomarkers to augment current clinico-pathologic predictors of outcomes in ccRCC.

A comprehensive immunohistochemical approach of AKT/mTOR pathway and p-STAT3 in mycosis fungoides

Although the expression pattern of phosphorylated (p)-mTOR pathway components has attracted scientific interest in several neoplasms, to our knowledge, there is no published information regarding its significance in mycosis fungoides (MF). We sought to perform a comprehensive simultaneous assessment of key members of AKT/mTOR pathway along with p-extracellular signal-regulated kinase (ERK), NOTCH1, and p-STAT3 in patients with MF. In all, 54 skin biopsy specimens (21 tumors, 30 plaques, and 3 folliculotropic MF) from 50 patients with MF were analyzed immunohistochemically for p-mTOR, its upstream p-AKT, its downstream effectors p-p70S6K and p-4E-BP1, and for p-ERK1/2, NOTCH1, and p-STAT3. p-mTOR was coexpressed with p-p70S6K in 67.3% of lesions, but coexpression with other molecules was less common. p-p70S6K and marginally NOTCH1 displayed higher H-scores in tumors than in plaques. Significant correlations were recorded between p-ERK and p-4E-BP1, as well as between NOTCH1 and p-p70S6K or p-4E-BP1. NOTCH1, p-4E-BP1, and p-p70S6K expression were associated with advanced stage. In survival analysis simultaneous overexpression of p-AKT and p-p70S6K, along with p-4E-BP1 positivity, adversely affected cancer-specific, disease-free, and progression-free survival in advanced-stage cases. A limitation may be the small number of cases included in our investigation, precluding multivariate survival analysis. Activation of AKT/mTOR pathway in MF appears to be correlated with NOTCH1, p-ERK, and p-STAT3 and is implicated in the acquisition of a more aggressive phenotype. The combination of p-AKT, p-p70S6K, and p-4E-BP1 emerges as a significant potential prognostic marker in patients with advanced stage.

Novel stratification of the recurrence risk following surgical extirpation of clear cell renal cell carcinoma using tissue biomarkers in the mammalian target of rapamycin pathway.

372 Background: Aberrant activation of the mammalian target of rapamycin (mTOR) pathway promotes invasiveness and metastatic potential in a variety of malignancies. The aim of the present study was to evaluate the association of altered expression of mTOR pathway components with recurrence outcome in non-metastatic clear cell renal cell carcinoma (ccRCC) patients. Methods: Immunohistochemistry for phos-S6, phos-mTOR, mTOR, phos-AKT, HIF-1α, RAPTOR, PTEN, PI3K, and phos-4EBP1 was performed on tissue microarrays of patients treated for non-metastatic kidney cancer between 1997-2010. Patients were defined as having a low (<) or high risk (≥) of nomogram predicted recurrence (2001 MSKCC RCC post-op) using an 8% cutoff. The relationship between individual marker expression, as well as combined marker score (low, intermediate and high defined as ≤ 3, 4-5, >5 altered biomarkers; respectively) with the actual and predicted relapse rates was assessed. Results: The study included 419 non-metastatic ccRCC patients (pT1-T2 79.5%, pT3-T4 20.5%, Fuhrman nuclear grade 1-2 in 69%, 3-4 in 31%). 219 and 200 patients had low (<8%) and high (≥8%) nomogram-predicted 5-year risk of recurrence respectively. With a median follow-up of 2.2 years, recurrences were detected in 5 (2.3%) of the predicted low risk and 30 (15%) of the predicted high risk patients. mTOR pathway biomarker profiles were not predictive for patients at low predicted risk of recurrences. For patients at high predicted risk of recurrence, low, intermediate and high combined marker scores were found in 84 (42%), 79 (39.5%), and 37 (18.5%), respectively. The actual rates of recurrence were noted for 8.3% of low, 13.9% of intermediate and 32.4% of high combined marker score in a statistically significant distribution (p=0.027). Conclusions: The cumulative number of aberrantly expressed mTOR biomarkers correlates with a higher rate of recurrence. The combined marker score may help further stratify patients with high nomogram predicted risk of recurrence. Our data supports prospective evaluation of these biomarkers to augment current clinico-pathologic predictors of outcomes in ccRCC.

Antitumor Effect of Everolimus in Preclinical Models of High-Grade Gastroenteropancreatic Neuroendocrine Carcinomas

Background/Aims: While the range of therapeutic options for well-differentiated gastroenteropancreatic neuroendocrine tumors has recently increased with the emergence of targeted therapies, such as mTOR inhibitors, there is no recent progress in the treatment of poorly differentiated neuroendocrine carcinomas (PDNECs). Since PDNECs have been shown to strongly express mTOR pathway components, the aim of the present study was to assess the antitumor effect of the mTOR inhibitor everolimus in preclinical models of PDNECs. Methods: The expression of mTOR pathway components and their response to everolimus were assessed in two neuroendocrine cell lines: STC-1 and GluTag. A xenograft model of intrahepatic dissemination in the nude mouse, based on the intrasplenic injection of either STC-1 and GluTag tumor cells, was used. Animals were started on everolimus treatment 3 days after injection. The effects of treatment on tumor growth, proliferative capacities, apoptosis and in situ expression of mTOR pathway components were assessed. Results: The expression of mTOR pathway components was comparable in STC-1 and GluTag cells and in human PDNECs and could be inhibited in vitro by everolimus. In vivo, the tumor volume of STC-1 and GluTag xenografts was significantly reduced in treated animals (6.05 ± 1.84% as compared to 21.76 ± 3.88% in controls). Everolimus treatment also induced a significant decrease in Ki67 index and in the phosphorylation levels of the two major effectors of mTOR, p70S6K and 4E-BP1. Conclusion: Our experimental data suggest that mTOR inhibition could be considered a therapeutic option for high-grade gastroenteropancreatic neuroendocrine tumors.

Cumulative Number of Altered Biomarkers in Mammalian Target of Rapamycin Pathway Is an Independent Predictor of Outcome in Patients With Clear Cell Renal Cell Carcinoma

To evaluate the association of the altered expression of the mammalian target of rapamycin (mTOR) pathway components with oncologic outcomes in patients with nonmetastatic clear cell renal cell carcinoma (ccRCC). Immunohistochemistry for phosphorylated-S6, phosphorylated-mTOR, mTOR, phosphorylated-AKT, hypoxia inducible factor-1α, Raptor, phosphatase and tensin homolog (PTEN), phosphoinositide 3-kinase (PI3K), and phosphorylated 4E-binding protein-1 was performed on tissue microarray constructs of patients treated for nonmetastatic kidney cancer from 1997 to 2010. The relationship between individual altered marker expression and a prognostic marker score (low, intermediate, and high, defined as ≤ 3, 4-5, >5 altered biomarkers, respectively) and oncologic outcome was assessed. The study included 419 patients with nonmetastatic ccRCC, with a median follow-up period of 26 months (range 6-150). The tumors were nonorgan confined (pT3-T4) in 86 (20.5%) and high Fuhrman nuclear grade (3-4) in 131 (31%). A low, intermediate, and high prognostic marker score was found in 214 (51%), 152 (36%), and 53 (13%) patients, respectively. Kaplan-Meier analysis demonstrated a statistically significant correlation between the risk groups and disease recurrence and cancer-specific survival. In a multivariate Cox regression analysis controlling for tumor stage and grade, a high marker score was an independent predictor of disease recurrence (hazard ratio 3.3, 95% confidence interval 1.33-8.39, P = .01), and a combination of a high and an intermediate score was an independent predictor of survival (hazard ratio 4.8, 95% confidence interval 1.27-4.78, P = .008). The cumulative number of aberrantly expressed biomarkers correlated with aggressive tumor biology and inferior oncologic outcomes in patients with ccRCC. Our data support prospective pathway-based exploration of the mTOR signaling cascade to augment current clinicopathologic predictors of oncologic outcomes in patients with ccRCC.

PI3K/AKT/mTOR signaling pathway inhibitors in proliferation of retinal pigment epithelial cells.

To determine whether the PI3K/AKT/mTOR pathway is activated in proliferative vitreoretinopathy (PVR) in homo-sapiens. The retina of controls and patients with PVR were collected and their levels of PI3K, phospho-AKT, phospho-mTOR, phospho-p70S6k and phospho-4EBP-1 were determined by Western blot. The cultured human retinal pigment epithelial cell line D407 was treated with a specific mTOR inhibitor, rapamycin (RAPA) or a PI3K inhibitor, LY294002, of various concentrations and durations. Cell morphology was observed by phase contrast microscopy and the proliferation and apoptosis of treated cells were determined by MTT assay and flow cytometry. Levels of PI3K, phospho-AKT, phospho-mTOR, phospho-P70S6K and phospho-4EBP1 was increased in the retina in PVR (P<0.05). In D407 cells, both RAPA and LY294002 significantly inhibited cell proliferation and cell cycle progression, and promoted apoptosis (P <0.05); morphologically, the cells became smaller. Both RAPA and LY294002 reduced levels of phospho-AKT, phospho-mTOR, phospho-p70S6k and phospho-4EBP1 expression (P <0.05). RAPA, but not LY294002, had no significant effect on PI3K expression. PI3K/AKT/mTOR signaling pathway is highly activated in the retinal pigment epithelial cells of PVR. The inhibitors of PI3K/AKT/mTOR signaling pathway, RAPA and LY294002, could inhibited the PI3K/AKT/mTOR signaling pathway by reducing the levels of phosphorylation of mTOR pathway components.

A Comprehensive Immunohistochemical Approach of AKT/mTOR Pathway and p-STAT3 in Mycosis Fungoides.

AbstractAbstract 2663 Background:Given the recent identification of the mTOR pathway as a possible target for cancer therapy, the expression pattern of phosphorylated mTOR (p-mTOR) pathway components has attracted vivid scientific interest in several neoplasms, including primary cutaneous T cell lymphomas. However, published information examining crosstalk between AKT/mTOR cascade and interconnected signaling pathways in mycosis fungoides (MF) is limited. Materials:We analysed immunohistochemically 54 skin biopsies (21 tumour and 33 plaque stage) from 50 patients with MF, for whom clinical information was available. Paraffin embedded tissue was stained for p-mTOR, its upstream p-AKT, its downstream effectors p-p70S6K and p-4E-BP1, as well as for p-ERK1/2 (extracellular signal-related kinase 1/2), the transcription factor Notch-1 and a member of the mammalian family of signal transducer activator of transcription, namely p-STAT-3. For statistical analysis only the predominant pattern i.e. cytoplasmic for p-mTOR, p-AKT, and NOTCH1 and nuclear for p-STAT3, p-p70S6K, p-4E-BP1 and p-ERK1/2 was taken into account. A Histo-score (H-score) based on the percentage of stained neoplastic cells (labelling index-LI) multiplied by staining intensity for each protein was calculated and was correlated with clinicopathological features and cancer-free (CSS), disease-free (DFS) and progression-free (PFS) survival. Results:p-p70S6K expression was recorded in all cases, whereas the rate of positivity for the remaining molecules ranged from 52.8% to 67.3%. p-mTOR was coexpressed with p-p70S6K in 67.3% of cases, but coexpression with other molecules was less common (27.4–38.5%). Notch-1 displayed higher H-scores in tumours than in plaques (p=0.0475), as previously demonstrated. The same applied to p-p70S6K, but this correlation was of borderline significance. Significant correlations were recorded between p-4E-BP1 and p-p70S6K (p=0.0019), p-ERK and p4E-BP1 (p=0.0588), as well as between Notch-1 and p-p70S6K (p=0.0001) and p-4E-BP1 (p=0.0003). The latter two correlations remained when plaques and tumours were analysed separately. Interestingly, p-STAT3 showed a weak positive correlation with p-AKT in the entire cohort, but when analysis was restricted to plaques this relationship became statistically significant (p=0.0419). Notch1, p-4E-BP1 and p-p70S6K expression were associated with advanced stage. In univariate survival analysis increased p-p70S6K (p=0.0174) and p-AKT (p=0.0198) H-scores as well as p-4E-BP-1 immunopositivity adversely affected CSS but not DFS in plaques, along with CD30 expression (p=0.0004). In particular, blood clonality affected both DFS and CSS, as well as time to disease progression (p=0.0009, p=0.0031 and p=0.0216 respectively). The CSS time was also substantially shortened for subjects with simultaneous overexpression of p-AKT and p-p70S6K along with p-4E-BP1 immunopositivity (p= 0.0001). On the contrary in the subgroup of tumours decreased p-STAT3 H-score was only parameter that adversely affected CSS in tumour stage (p=0.0394), with the presence of blood clonality attaining marginal significance in this regard. Conclusions:Activation of AKT-mTOR components appears to have an intimate liaison with NOTCH1, p-ERK and p-STAT-3 and seems to be implicated in disease progression and in the acquisition of a more aggressive phenotype. Phosphorylation of several key components of this pathway, namely AKT, p70S6K and 4E-BP1 in MF, single or in combinations emerge as potential markers of prognostic value in plaque stage, whereas in tumours p-STAT-3 is brought forward as a favourable prognostic marker. Disclosures:No relevant conflicts of interest to declare.

LKB1 mutations and their correlation with LKB1 and Rheb expression in bladder cancer

Although there are extensive studies on the genetics of bladder cancer, several questions remain unanswered. One of the pathways which are altered in bladder cancer is the mTOR signaling pathway. In the present study, we analyzed the expression of Rheb gene and genetic alterations in the LKB1 gene which are the key components of mTOR pathway. Nine exons of the LKB1 gene were analyzed by direct sequencing in 51 bladder cancer patients. To investigate the expression of Rheb and LKB1, real-time quantitative RT-PCR was performed in bladder tumor and normal bladder tissue samples. We did not observed a statistically significant difference in Rheb or LKB1 expression between the tumor and normal tissue samples. We detected a novel missense mutation creating stop codon in a high percent of the tumor samples. Five different single nucleotide substitutions were also observed in the introns. Our results indicate that LKB1 gene may play a role in the progression of bladder cancer.

Synergistic Effects of Erlotinib and Everolimus on Bronchial Carcinoids and Large-Cell Neuroendocrine Carcinomas with Activated EGFR/AKT/mTOR Pathway

Background: Epidermal growth factor receptor (EGFR) and mammalian target of rapamycin (mTOR) are crucial targets in cancer therapy. Combined inhibition of both targets yielded synergistic effects in vitro and in vivo in several cancer entities. However, the impact of EGFR and mTOR expression and combined inhibition in neuroendocrine lung tumors other than small-cell lung cancer remains unclear. Material and Methods: Expression and activation of EGFR/AKT/mTOR pathway constituents were investigated in typical and atypical bronchial carcinoid (AC) tumors and large-cell neuroendocrine lung carcinomas (LCNEC) by immunohistochemistry in 110 tumor samples, and correlated with clinicopathological parameters and patient survival. Cytotoxicity of mTOR inhibitor everolimus and EGFR inhibitor erlotinib alone and in combination was assessed using growth inhibition assay in NCI-H720 AC and SHP-77 LCNEC cells. Cell cycle phase distribution was determined by FACS. Apoptosis-associated activation of caspase-3/7 was measured by Caspase-Glo® assay. Activity status of EGFR and mTOR pathway components was analyzed by immunoblotting. Results: Activation of the EGFR/AKT/mTOR axis could be demonstrated in all entities and was significantly increased in higher grade tumors. Neoadjuvant chemotherapy correlated significantly with p-AKT expression and p-ERK loss. Erlotinib combined with everolimus exerted synergistic combination effects in AC and LCNEC cells by induction of apoptosis, while cell cycle phase distribution remained unaffected. These effects could be explained by synergistic downregulation of phospho-mTOR, phospho-p70S6 kinase and phospho-AKT expression by everolimus and erlotinib. Conclusions: Our study indicates that EGFR and mTOR are clinically important targets in bronchial neuroendocrine tumors, and further in vivo and clinical exploration of combined inhibition is warranted.

A phase II study to evaluate the safety and efficacy of RAD001 plus erlotinib in patients with well-differentiated neuroendocrine tumors (NET).

285 Background: Building on strong preclinical data, we hypothesized that concomitantly targeting mammalian target of rapamycin (mTOR) and epidermal growth factor receptor (EGFR) signaling pathways will inhibit neuroendocrine tumors (NET) more effectively than targeting either pathway alone (thus improving likelihood of shrinkage). We initiated a prospective, phase II study to assess the safety and efficacy of RAD001 plus erlotinib in patients (pts) with advanced NET. Methods: Pts with well-differentiated NET were enrolled using a Simon 2-stage design with 2 groups: pancreatic NET (PNET) and other low-grade NET/ carcinoid (CARC). Eligibility criteria included histological diagnosis of a well- to moderately-differentiated NET and no prior mTOR- or EGFR-inhibitor. Pts treated with RAD001 5 mg PO QD and erlotinib 100 mg PO QD without scheduled breaks (1 cycle = 28 d). Pts followed for toxicity and radiographic response, with first planned analysis after 8 evaluable pt/group. Results: Since 6/09, 17 pt enrolled: M/F 9/8; PNET/CARC 8/9. Pts on octreotide remained on drug. All pt had PD at enrollment. Median # cycles: 12 in CARC (range 2-20); 5.5 (to date) in PNET (range 0.5-18). Excessive toxicity in first 7 pts prompted reduction in starting erlotinib dose from 150 to 100 mg/d, resulting in improved tolerability: Gr 3 stomatitis in 3/7 initial pts (43%) vs 1/10 (10%) after new starting dose. Overall, the most common side effects include diarrhea, stomatitis, rash, anorexia, and fatigue. Enrollment to CARC cohort stopped after first stage due to insufficient efficacy (7/9 SD, 2/9 PD; 0 PR). Conclusions: RAD001 plus erlotinib appears to be associated with radiographic stability, but not shrinkage, in CARC. Combining the two agents has proven challenging; toxicity precludes administration of either agent at full dose. Interim efficacy analysis for PNET stratum pending. Correlation with expression of mTOR pathway components in archived tissue planned.

Expression of the Mammalian Target of Rapamycin Pathway Markers in Lung Adenocarcinoma and Squamous Cell Carcinoma

Objective: We investigated whether the expression of mammalian target of rapamycin (mTOR) pathway components is associated with clinicopathologic characteristics and patient outcome in lung adenocarcinoma (AC) and squamous cell carcinoma (SCC). Methods: We used immunohistochemistry to evaluate the expression of phosphorylated Akt (pAkt), mTOR, p70 ribosomal protein S6 kinase (p70S6K) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in 91 cases of AC and 154 cases of SCC. Results: pAkt expression was positively correlated with the expression of mTOR (p < 0.001) and p70S6K (p < 0.001), and mTOR expression was positively correlated with p70S6K expression (p < 0.001). PTEN expression was inversely correlated with the expression of pAkt (p = 0.001), mTOR (p < 0.001) and p70S6K (p = 0.012). In addition, loss of PTEN expression, observed in 37.4% (34/91) of AC patients, was significantly associated with a higher histologic grade (p = 0.013), pathologic T stage (p = 0.016) and N stage (p < 0.001) and advanced TNM stage (p = 0.001), as well as a shorter overall survival of AC patients (p = 0.015). Conclusion: The high prevalence of PTEN loss and its association with aggressive tumor behavior and poor patient outcome in AC suggest that loss of PTEN expression is involved in AC progression and serves as a prognostic marker for patients with AC.

Erufosine simultaneously induces apoptosis and autophagy by modulating the Akt–mTOR signaling pathway in oral squamous cell carcinoma

We investigated the anticancer activity of erufosine in oral squamous carcinoma cell lines in terms of cell proliferation, colony formation, induction of autophagy/apoptosis, cell cycle and mTOR signaling pathway. Erufosine showed dose-dependent cytotoxicity in all cell lines, it induced autophagy as well as apoptosis, G2 cell cycle arrest and modulation of cyclin D1 expression. Further erufosine downregulated the phosphorylation of major components of mTOR pathway, like p-Akt at Ser473 and Thr308 residues, p-Raptor, p-mTOR, p-PRAS40 and its downstream substrates p-p70S6K and p-4EBP1 in a dose-dependent manner. The pre-treatment of tumor cells with p-mTOR siRNA increased cytotoxic effects of erufosine comparable to cisplatin but higher than rapamycin.

Inhibition of induced autophagy increases apoptosis of Nara-H cells

Inhibition of the mTOR signaling pathway promotes initiation of autophagy. However, recent studies indicate that autophagy is a self-defense mechanism of cancer cells that are subjected to anti-tumor agents and that blocking autophagy can trigger apoptosis. Here, we examined the effects of an mTOR inhibitor, temsirolimus, on a malignant fibrous histiocytoma (MFH) cell line, Nara-H cells, and the effect of suppressing autophagy on the induction of apoptosis in these MFH cells. In Nara-H cells, we examined the effects of temsirolimus treatment on cell proliferation using the CellTiter 96® AQueous One Solution Cell Proliferation Assay and on phosphorylation of mTOR pathway components and autophagy using Western blot-based assays. Furthermore, we examined the effects of temsirolimus with or without 3-methyladenine (3-MA) on induction of apoptosis using fluorescent microscopic analysis. In Nara-H cells, temsirolimus treatment inhibited cell proliferation, suppressed phosphorylation of mTOR pathway components, and induced autophagy as assessed by LC-3 II expression. Moreover, treatment with a combination of temsirolimus and 3-MA induced apoptosis in Nara-H cells. Apparently, simultaneous inhibition of autophagy and mTOR induced apoptosis in Nara-H cells because inhibition of autophagy prevented the cells from protecting themselves from the effects of the inhibition of mTOR. Therefore, a combination therapy that includes an mTOR inhibitor and an autophagy inhibitor (temsirolimus and 3-MA, respectively) may effectively treat MFH by inducing apoptosis in tumor cells.

An emerging role for TOR signaling in mammalian tissue and stem cell physiology

The mammalian target of rapamycin (mTOR) is a kinase that responds to a myriad of signals, ranging from nutrient availability and energy status, to cellular stressors, oxygen sensors and growth factors. The finely tuned response of mTOR to these stimuli results in alterations to cell metabolism and cell growth. Recent studies of conditional knockouts of mTOR pathway components in mice have affirmed the role of mTOR signaling in energy balance, both at the cell and whole organism levels. Such studies have also highlighted a role for mTOR in stem cell homeostasis and lifespan determination. Here, we discuss the molecular mechanisms of TOR signaling and review recent in vitro and in vivo studies of mTOR tissue-specific activities in mammals.

Phosphoproteomic Profiling of In Vivo Signaling in Liver by the Mammalian Target of Rapamycin Complex 1 (mTORC1)

BackgroundOur understanding of signal transduction networks in the physiological context of an organism remains limited, partly due to the technical challenge of identifying serine/threonine phosphorylated peptides from complex tissue samples. In the present study, we focused on signaling through the mammalian target of rapamycin (mTOR) complex 1 (mTORC1), which is at the center of a nutrient- and growth factor-responsive cell signaling network. Though studied extensively, the mechanisms involved in many mTORC1 biological functions remain poorly understood.Methodology/Principal FindingsWe developed a phosphoproteomic strategy to purify, enrich and identify phosphopeptides from rat liver homogenates. Using the anticancer drug rapamycin, the only known target of which is mTORC1, we characterized signaling in liver from rats in which the complex was maximally activated by refeeding following 48 hr of starvation. Using protein and peptide fractionation methods, TiO2 affinity purification of phosphopeptides and mass spectrometry, we reproducibly identified and quantified over four thousand phosphopeptides. Along with 5 known rapamycin-sensitive phosphorylation events, we identified 62 new rapamycin-responsive candidate phosphorylation sites. Among these were PRAS40, gephyrin, and AMP kinase 2. We observed similar proportions of increased and reduced phosphorylation in response to rapamycin. Gene ontology analysis revealed over-representation of mTOR pathway components among rapamycin-sensitive phosphopeptide candidates.Conclusions/SignificanceIn addition to identifying potential new mTORC1-mediated phosphorylation events, and providing information relevant to the biology of this signaling network, our experimental and analytical approaches indicate the feasibility of large-scale phosphoproteomic profiling of tissue samples to study physiological signaling events in vivo.