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ETV7 is an essential component of a rapamycin-insensitive mTOR complex in cancer.

ABSTRACT: The mechanistic target of rapamycin (mTOR) serine/threonine kinase, a critical regulator of cell proliferation, is frequently deregulated in human cancer. Although rapamycin inhibits the two canonical mTOR complexes, mTORC1 and mTORC2, it often shows minimal benefit as an anticancer drug. This is caused by rapamycin resistance of many different tumors, and we show that a third mTOR complex, mTORC3, contributes to this resistance. The ETS (E26 transformation-specific) transcription factor ETV7 interacts with mTOR in the cytoplasm and assembles mTORC3, which is independent of ETV7's transcriptional activity. This complex exhibits bimodal mTORC1/2 activity but is devoid of crucial mTORC1/2 components. Many human cancers activate mTORC3 at considerable frequency, and tumor cell lines that lose mTORC3 expression become rapamycin-sensitive. We show mTORC3's tumorigenicity in a rhabdomyosarcoma mouse model in which transgenic ETV7 expression accelerates tumor onset and promotes tumor penetrance. Discovery of mTORC3 represents an mTOR paradigm shift and identifies a novel target for anticancer drug development.

SUBMITTER: Harwood FC

PROVIDER: S-EPMC6156121 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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ETV7 is an essential component of a rapamycin-insensitive mTOR complex in cancer.

Harwood Franklin C FC Klein Geltink Ramon I RI O'Hara Brendan P BP Cardone Monica M Janke Laura L Finkelstein David D Entin Igor I Paul Leena L Houghton Peter J PJ Grosveld Gerard C GC

Science advances 20180912 9

The mechanistic target of rapamycin (mTOR) serine/threonine kinase, a critical regulator of cell proliferation, is frequently deregulated in human cancer. Although rapamycin inhibits the two canonical mTOR complexes, mTORC1 and mTORC2, it often shows minimal benefit as an anticancer drug. This is caused by rapamycin resistance of many different tumors, and we show that a third mTOR complex, mTORC3, contributes to this resistance. The ETS (E26 transformation-specific) transcription factor ETV7 in ...[more]

PMID: 30258985

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Project description:AimsThe mammalian target of rapamycin (mTOR) and phosphorylated mTOR (p-mTOR) occurring downstream in the PI3K/Akt/mTOR pathway, are regarded as potential prognostic markers for gastric cancer (GC). However, the prognostic value of mTOR/p-mTOR expression remains controversial. In this study, we determined the expression of mTOR, p-mTOR, p70S6k, and p-p70S6K in GC, and investigated the correlation between their overexpression, clinicopathological parameters, and overall survival (OS).MethodsThe expression of mTOR, p-mTOR, p70S6k, and p-p70S6K was examined in 120 GC patients by immunohistochemistry (IHC). The association of protein expression with clinicopathological features and OS was explored. The p-mTOR expression was detected in normal, adjacent, and GC tissues using Western blot. Eligible studies retrieved from PubMed, Ovid, Web of Science and Cochrane databases, were reviewed in this meta-analysis.ResultsIHC showed that the rates of expression of the signal transduction molecules mTOR, p-mTOR, p70S6k and p-p70S6K in GC were 60.8%, 54.2%, 53.3% and 53.3%, respectively. Overexpression of mTOR and p70S6K showed no significant association with clinical variables. Expression of p-mTOR was significantly associated with differentiation (P < 0.01), depth of invasion (P < 0.01), lymph node metastasis (P = 0.04) and TNM stage (P = 0.02). Expression of p-p70S6K was associated with differentiation (P = 0.006), depth of invasion (P < 0.001), and TNM stage (P = 0.02). In survival analysis, differentiation, depth of invasion, lymph node metastasis and TNM stage were not related to OS (all P > 0.05). Furthermore, p-mTOR and p-p70S6K expression, but not mTOR and p70S6K, were tightly associated with OS of GC patients (P = 0.006 and P < 0.001, respectively). In Western blot, p-mTOR was significantly higher in GC tissues than in normal and adjacent tissues. In the present meta-analysis, mTOR overexpression showed no relationship with any clinicopathological variables. However, p-mTOR was correlated with depth of invasion, and TNM stage (all P < 0.05), and its overexpression was associated with a shorter survival time (P < 0.001).ConclusionThe results suggest that p-mTOR is a more valuable prognostic factor than mTOR in GC.

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ETV7 is an essential component of a rapamycin-insensitive mTOR complex in cancer.

Publications

ETV7 is an essential component of a rapamycin-insensitive mTOR complex in cancer.

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