2475

MTOR

mechanistic target of rapamycin (serine/threonine kinase);MTOR;mechanistic target of rapamycin (serine/threonine kinase)

FK506 binding protein 12-rapamycin associated protein 2|FK506-binding protein 12-rapamycin complex-associated protein 1|FKBP-rapamycin associated protein|FKBP12-rapamycin complex-associated protein 1|mammalian target of rapamycin|rapamycin and FKBP12 targ

1p36.2

protein-coding

The need for effective targeted therapies for renal cell carcinomas (RCCs) has fueled the interest for understanding molecular pathways involved in the oncogenesis of kidney tumors. Aiming to analyze the expression status and prognostic significance of mTOR and hypoxia-induced pathway members in patients with clear cell RCC (ccRCC), tissue microarrays were constructed from 135 primary and 41 metastatic ccRCCs. Immunoexpression levels were compared and correlated with clinicopathologic parameters and outcome. PTEN levels were significantly lower in primary and metastatic ccRCCs compared with benign tissues (P<0.001). Levels of phos-AKT, phos-S6, and 4E-binding protein-1 (4EBP1) were higher in metastatic ccRCC (Pmetastatic ccRCC (P<0.0001), and incremental p27 levels were observed in benign, primary ccRCC, and metastatic ccRCC (P<0.0001). HIF-1alpha levels were significantly higher in primary and metastatic ccRCCs compared with benign tissues (P<0.0001). In primary ccRCC, levels of all mTOR and hypoxia-induced pathway members were significantly associated with pT stage (Ptumor size (Ptumor size, HIF-1alpha, and phos-S6 levels were associated with disease-specific survival (DSS) (Ptumor progression (Ppathways were activated in primary and metastatic ccRCC. PTEN loss seems to be an early event during tumorigenesis. tumor size, HIF-1alpha, and phos-S6 expression were found to be independent predictors of both DSS and tumor progression in primary ccRCC.

AIM: To investigate the significance of mammalian target of rapamycin (mTOR) and its active form, p-mTOR in colorectal carcinomas. METHODS: Immunohistochemistry was used to detect the expression of mTOR and p-mTOR proteins in 108, 40 and 40 tissue samples from colorectal carcinoma, normal colonic mucosa and adenomatous polyps samples, respectively. The correlation of mTOR and p-mTOR expression with clinicopathological characteristics of colorectal carcinoma was analyzed. RESULTS: The positive rates of mTOR and p-mTOR were significantly higher in colorectal carcinoma (61.1% and 61.1%, respectively, p<0.05) than in normal colonic mucosa (7.5% and 2.5%) and adenomatous polyps (27.5% and 20%). Overexpression of total mTOR protein was significantly associated with T1/T2 stage tumors, lymph node metastasis, distal metastasis) and degree of differentiation. p-mTOR overexpression was additionaly linked with degree of differentiation and TNM stage. CONCLUSION: The overexpression of mTOR and p-mTOR may play important roles in colorectal carcinogenesis with relations to the degree of differentiation, invasiveness and metastasis.

AIMS AND BACKGROUND: Mammalian target of rapamycin (mTOR) is one of the serine-threonine protein kinases and plays an important regulatory role in cell growth. Eukaryotic translation initiation factor 4E (eIF4E) and 4E binding protein (4EBP) are the downstream proteins of mTOR signaling pathway and are the most efficient speed regulator of eukaryotic mRNA translation. The aim of the study was to investigate the clinical significance of mTOR, eIF4E and 4EBPs expression in invasive ductal carcinoma. METHODS: Fresh biopsy specimens of invasive ductal carcinoma tissues and normal breast tissues were collected from 45 patients with breast cancer. The expressions of mTOR, eIF4E and 4EBPs in specimens were detected by an immunohistochemical SP method, and the relationship of mTOR, eIF4E and 4EBPS expressions and of their expressions with tumor metastasis were analyzed. RESULTS: expressions of mTOR, eIF4E and 4EBPs in invasive ductal carcinoma were significantly higher than in normal breast tissue (P <0.05). mTOR expression was positively correlated with eIF4E and 4EBP expression in invasive ductal carcinoma (P <0.05). The positive rates of mTOR, eIF4E and 4EBPs in patients with lymph node metastasis were significantly higher than in patients without lymph node metastasis (P <0.05). CONCLUSIONS: Increased expressions of mTOR and eIF4E in invasive ductal carcinoma may be correlated with the occurrence and metastasis of breast cancer.

PURPOSE: We determined the expression of mammalian target of rapamycin (mTOR) and its activated form, p-mTOR, in Chinese patients with gastric cancer and its clinical effects and underlying mechanisms. EXPERIMENTAL DESIGN: Tissue microarray blocks containing gastric cancer tissue and matched noncancer gastric tissue specimens obtained from 1,072 patients were constructed. expression of total mTOR and p-mTOR in these specimens was analyzed using immunohistochemical studies and confirmed by Western blotting. RESULTS: The overall rates of total mTOR and p-mTOR overexpression were 50.8% (545 of 1,072) and 46.5% (499 of 1,072), respectively. The p-mTOR overexpression was significantly correlated with total mTOR overexpression. Overexpression of total mTOR protein was significantly correlated with tumor differentiation, T1/T2 tumors, and stage I/II/III disease, whereas p-mTOR overexpression was significantly correlated with lymph node metastasis and all stage disease. The Cox proportional hazards model revealed that the overexpression of p-mTOR, but not total mTOR, was an independent prognostic factor for gastric cancer. The overexpression of p-mTOR also predicted the angiogenic phenotype of human gastric cancer and regulated angiogenesis of gastric cancer cells. CONCLUSIONS: Increased activation of mTOR is frequent in human gastric cancer and overexpression of p-mTOR is an independent prognostic factor, suggesting that mTOR pathway could be a potential target for therapy of this malignancy.

Despite the great interest in mammalian target of rapamycin (mTOR) as a potential anticancer therapy target, the prognostic role of mTOR in gastric cancer has not been elucidated. In this study, we investigated mTOR expression in gastric cancer tissues and in metastatic lymph nodes and examined its association with clinical outcome. A total of 290 patients with pT2b gastric cancer were enrolled in this study. Patients were divided into 3 groups according to metastatic lymph node status: Group 1 contained 96 patients without lymph node metastasis, Group 2 contained 102 patients with a few (1-2) metastatic lymph nodes and Group 3 contained 92 patients with extensive (>16) lymph node metastasis. Phosphorylated mTOR expression was determined immunohistochemically using tissue microarrays. p-mTOR expression was observed in 36.5% of the gastric cancer tissues in Group 1, 39.2% in Group 2 and 60.9% in Group 3. A significant correlation was found between p-mTOR expression in gastric cancer tissues and in metastatic lymph nodes. The Borrmann type in Group 1, perineural invasion and p-mTOR expression in metastatic lymph nodes in Group 2 and p-mTOR expression in metastatic lymph nodes in Group 3 were found to be independent prognostic factors of disease-free survival. The 5-year disease free survival rate of Group 2 patients was 84.4% in negative p-mTOR and 66.1% in positive p-mTOR expression in metastatic lymph nodes (p = 0.015). The 5-year disease free survival rate of Group 3 patients was 37.3% in negative p-mTOR and 14.9% in positive p-mTOR expression in metastatic lymph nodes (p = 0.037). There was a linear correlation between the rate of tumor recurrence and mTOR expression scores in metastatic lymph nodes. In pT2b gastric cancer, p-mTOR expression in gastric cancer is associated with the extent of lymph node metastasis, and p-mTOR expression in metastatic lymph nodes is correlated with poor disease-free survival. mTOR may harbor significant potential for a prognostic biomarker and therapeutic target for gastric cancer treatment.

Although evidence has shown that both the mammalian target of rapamycin and beta-catenin are involved in hepatocellular carcinoma, little is known about their relationship in pathogenesis of hepatocellular carcinoma. To investigate the expression of phosphorylated mammalian target of rapamycin and beta-catenin and their prognostic impacts, as well as their relationship in hepatocellular carcinoma, we analyzed 63 human hepatocellular carcinoma samples by immunohistochemistry. Phosphorylated mammalian target of rapamycin cytoplasmic and beta-catenin cytoplasmic/nuclear-positive immunoreactivities were observed in 63.5% (40/63) and 55.6% (35/63) of the hepatocellular carcinoma specimens, respectively. Significant associations were found between cytoplasmic beta-catenin and phosphorylated mammalian target of rapamycin expression and tumor size (both P < .01) and metastasis (P < .01 and P < .05, respectively). In addition, beta-catenin expression in the cytoplasm was closely associated with the expression of phosphorylated mammalian target of rapamycin. To further explore the relationship between mammalian target of rapamycin and beta-catenin, hepatocellular carcinoma HepG2 and Hep3B cells were treated with beta-catenin siRNA and mammalian target of rapamycin inhibitor, rapamycin; and the expression of phosphorylated mammalian target of rapamycin and beta-catenin in cells was then measured by Western blot. The activity of Wnt/beta-catenin signaling pathway was also assessed by luciferase reporter assay. The cell viability and proliferation were evaluated by thiazolyl blue tetrazolium bromide assay and [(3)H]-thymidine incorporation assay. The results showed that the level of beta-catenin protein expression was markedly decreased by rapamycin in HepG2 and Hep3B cells. The reduction of beta-catenin and mammalian target of rapamycin resulted in inhibition of cell viability proliferation, but the combination of reduction of beta-catenin and mammalian target of rapamycin did not show a synergistic effect on the inhibition of cell viability and proliferation in HepG2 and Hep3B cells. In conclusion, the present study showed that, for the first time, mammalian target of rapamycin regulated the expression level of beta-catenin in hepatocellular carcinoma. Both mammalian target of rapamycin and beta-catenin play important roles in the growth, metastasis, and prognosis of hepatocellular carcinoma.

Although the KAI1/CD82 protein has been reported to inhibit cell metastasis in many studies, its mechanism of action has not yet been fully elucidated. In the present study, we investigated the possible effects of KAI1/CD82 on the metastatic phenotype in H1299 lung carcinoma cells. These studies were based on the pivotal role that the acquisition of motile phenotype plays on the initial steps of metastasis. KAI1/CD82-mediated morphological changes were observed using phase contrast microscopy. We report here, that a KAI1/CD82-induced phenotypic change was involved in the decrease of Rac1 expression and GTPase activity. However, we found that KAI1/CD82 did not regulate Rac1 mRNA levels. This suggests the existence of another regulatory mechanism of Rac1 protein maturation or activation. To identify the signaling pathway of Rac1 regulation, we investigated the PI3K/Akt/mTOR pathway, since the PI3K/Akt pathway regulates Rac1 activation and mTOR is known to play a regulatory role in protein translation. H1299/CD82-transfectants showed lower mTOR expression and cell growth than the control group. The data obtained from this study suggested that KAI1/CD82 decreased the metastatic phenotype of H1299 lung carcinoma cells by down-regulating Rac1 expression through the PI3K/Akt/mTOR pathway.

In cancer progression, carcinoma cells gain invasive behavior through a loss of epithelial characteristics and acquisition of mesenchymal properties, a process that can lead to epithelial-mesenchymal transition (EMT). TGF-beta is a potent inducer of EMT, and increased TGF-beta signaling in cancer cells is thought to drive cancer-associated EMT. Here, we examine the physiological requirement for mTOR complex 2 (mTORC2) in cells undergoing EMT. TGF-beta rapidly induces mTORC2 kinase activity in cells undergoing EMT, and controls epithelial cell progression through EMT. By regulating EMT-associated cytoskeletal changes and gene expression, mTORC2 is required for cell migration and invasion. Furthermore, inactivation of mTORC2 prevents cancer cell dissemination in vivo. Our results suggest that the mTORC2 pathway is an essential downstream branch of TGF-beta signaling, and represents a responsive target to inhibit EMT and prevent cancer cell invasion and metastasis.

Clinical trials indicate efficacy of drugs inhibiting the mammalian target of rapamycin (mTOR) in the treatment of gastroenteropancreatic neuroendocrine tumours (GEP-NET); however, information on detailed expression and activity patterns of mTOR in these tumours is sparse. We investigated the expression of mTOR and expression as well as phosphorylation of its downstream targets 4EBP1, S6K and eIF4E in a cohort of 99 human GEP-NET by immunohistochemistry. We correlated our findings with clinicopathological variables and patient prognosis. We found that 61, 93, 80, 69, 57 and 79% of GEP-NET were positive for mTOR, 4EBP1, cytoplasmic phospho-4EBP1 (p-4EBP1), nuclear p-4EBP1, phospho-S6K (p-S6K) and phospho-eIF4E (p-eIF4E) respectively. mTOR expression and activity were higher in foregut than in midgut tumours. In foregut tumours, expression of mTOR was higher when distant metastases were present (P=0.035). Strong mTOR activity was associated with higher proliferative capacity. In patients with stage IV midgut tumours, strong p-S6K expression was associated with poor disease-specific survival (P=0.048). In conclusion, mTOR shows considerable variations in expression and activity patterns in GEP-NET in dependence of tumour location and metastatic status. We hypothesise that these differences in mTOR expression and activity might possibly influence response to mTOR inhibitors.

OBJECTIVES: Patients with advanced pancreatic neuroendocrine tumors have limited therapeutic options. Everolimus (RAD001), an inhibitor of the mammalian target of rapamycin (mTOR) pathway, has been shown to increase progression-free survival, but not overall survival, indicating a need to identify additional therapeutic targets. Inhibition of mTOR complex 1 by RAD001 may induce upstream AKT upregulation. We hypothesized that dual inhibition of AKT along with mTOR will overcome the limited activity of RAD001 alone. METHODS: The BON cell line has been used as a model to study pancreatic neuroendocrine tumor cell biology. Western blots and cell growth assays were performed with mTOR inhibitor RAD001 (50 nM), mitogen-activated protein kinase inhibitor PD0325901 (50 nM), PI3K (phosphatidylinositol 3-kinase) inhibitor LY294002 (25 muM), or vehicle control. Nude mice were treated daily for 6 weeks with RAD001 (oral gavage) and with LY29400 (subcutaneous) 1 week after intrasplenic injection of BON cells. RESULTS: Cellular proliferation was most attenuated with the combination therapy of LY29400 and RAD001. Similarly, the volume of liver metastasis was lowest in the group treated with both LY29400 (100 mg/kg per week, subcutaneous) and RAD001 (2.5 mg/kg per day) compared with that in the vehicle group (P = 0.04). CONCLUSION: The combination therapy of LY29400 and RAD001 decreased the cell growth in vitro and progression of liver metastasis in vivo compared with vehicle or with single-drug therapy.

BACKGROUND AND OBJECTIVE: It has been proved that mTOR was an important signal transduction molecular and protein kinase regulating cell growth and proliferation, and mTOR could activate the downstream protein effector. PTEN could negatively regulate mTOR signal pathway and inhibit its activity. The aim of this study is to detect the mRNA expression levels of mTOR and PTEN gene, which are the key genes of mTOR signaling pathway in human non-small cell lung cancer (NSCLC) tissue. The relationship between mTOR signaling pathway and NSCLC is also explored. METHODS: Lung cancer tissue specimens were obtained from 65 patients. Adjacent-tumor non-small cell lung cancer tissues from the 30 patients were served as control. The RT-PCR technique was used to detect the mTOR and PTEN gene expression levels. RESULTS: The average mRNA expression levels of mTOR gene were significantly higher (0.23 +/- 0.16) in lung cancer than in adjacent-tumor tissue (0.12 +/- 0.09)(P < 0.01). The average mRNA expression levels of PTEN gene were (0.19 +/- 0.28) in lung cancer, while the mRNA expression levels of PTEN gene were (0.53 +/- 0.28) in adjacent-tumor tissue (P < 0.01). The levels of PTEN gene expression in non-small cell lung cancer were significantly lower than that in adjacent-tumor lung tissue. There are not significant relationship between mTOR and PTEN gene expression levels and patients' age, gender, pathological type, differentiation, lymph node metastasis, except tumor size. CONCLUSIONS: The expression of mTOR is activated in NSCLC. The expression of PTEN is absent or decreased. The mTOR activated in NSCLC may be correlate with the absent or decreased of PTEN. The absent or decreased expression of PTEN and the actived mTOR may play important roles in carcinogenesis and metastasis of NSCLC.

The AKT signaling pathway is crucial for cancer cell survival. The objective of this study was to analyze the expression and clinical role of this pathway in serous ovarian carcinoma. Phospho-AKT and phospho-mammalian target of rapamycin protein expression was studied in 269 ovarian carcinomas (159 effusions, 38 primary carcinomas, 72 solid metastases) using immunohistochemistry. The association between AKT, mammalian target of rapamycin, and DJ-1 in effusions was quantitatively analyzed using flow cytometry. AKT phosphorylation status in effusions was further studied using Western blotting. Phospho-AKT and phospho-mammalian target of rapamycin were detected in the majority of tumors at all anatomical sites. Phospho-AKT expression in effusions was higher in grade 3 versus grades 1 and 2 tumors (P = .013). Flow cytometry analysis showed association between AKT, mammalian target of rapamycin, and DJ-1 expression (P < .001). Higher phospho-AKT Thr308/pan-AKT ratio by Western blotting was associated with more advanced International Federation of Gynecology and Obstetrics stage (P = .018) and a trend for poor response to chemotherapy at first disease recurrence (P = .051). Higher phospho-mammalian target of rapamycin protein expression in effusions by immunohistochemistry was associated with poor progression-free survival for patients with postchemotherapy effusions (P = .005). Phospho-mammalian target of rapamycin was an independent predictor of poor progression-free survival for patients with postchemotherapy effusions (P = .03). The association between activated AKT and mammalian target of rapamycin expression and clinicopathologic parameters of aggressive disease, including shorter patient survival, provides further evidence regarding the central role of this signaling pathway in ovarian carcinoma.