TMEM65 promotes gastric tumorigenesis by targeting YWHAZ to activate PI3K-Akt-mTOR pathway and is a therapeutic target
Copy number alterations are crucial for the development of gastric cancer (GC). Here, we identified Transmembrane Protein 65 (TMEM65) amplification by genomic hybridization microarray to profile copy-number variations in GC. TMEM65 mRNA level was significantly up-regulated in GC compared to adjacent normal tissues, and was positively associated with TMEM65 amplification. High TMEM65 expression or DNA copy number predicts poor prognosis in GC. Furtherly, GC patients with TMEM65 amplification or overexpression significantly associated with shortened survival. Ectopic expression of TMEM65 significantly promoted cell proliferation, cell cycle progression and cell migration/invasion ability, but inhibited apoptosis. Conversely, silencing of TMEM65 in GC cells showed opposite abilities on cell function in vitro and suppressed tumor growth and lung metastasis in vitro. Moreover, TMEM65 depletion by VNP-encapsulated TMEM65-siRNA significantly suppressed tumor growth in subcutaneous xenograft model. Mechanistically, TMEM65 exerted oncogenic effects through activating PI3K-Akt-mTOR signaling pathway, as evidenced of increased expression of key regulators (p-Akt, p-GSK-3ß, p-mTOR) by Western blot. YWHAZ (Tyrosine 3-Monooxygenase/Tryptophan 5-Monooxygenase) was identified as a direct downstream effector of TMEM65. Direct binding of TMEM65 with YWHAZ in the cytoplasm inhibited ubiquitin-mediated degradation of YWHAZ. Moreover, oncogenic effect of TMEM65 was partly dependent on YWHAZ. In conclusion, TMEM65 promotes gastric tumorigenesis by activating PI3K-Akt-mTOR signaling via cooperating with YWHAZ. TMEM65 overexpression may serve as an independent new biomarker and is a therapeutic target in GC. Overall design: To investigate the effect of TMEM65 on gastric cancer cells, we used a TMEM65-expressing lentivirus to construct AGS stable expressing TMEM65 cells. We then performed gene expression peofiling analysis of RNA-seq data for AGS overexpressed or vector.