ARHGAP9 inhibits colorectal cancer cell proliferation, invasion and EMT via targeting PI3K/AKT/mTOR signaling pathway

In digestive system, colorectal cancer (CRC) is a common malignant tumor. The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of the rapamycin (PI3K/AKT/mTOR) signaling pathway plays a central role in CRC, and the aberrant activation of this pathway is associated with tumorigenesis. We aimed to explore the role of Rho GTPase activating protein 9 (ARHGAP9) in the progression of CRC as well as its regulatory effects on the PI3K/AKT/mTOR pathway. The expression of ARHGAP9 in CRC tumor tissues and cell lines were detected using reverse transcription-quantitative PCR (qRT-PCR). 5-ethynyl-2′-deoxyuridine (EdU) assay was applied to test the cell proliferation. Cell migration and invasion were both assessed through transwell assay. Xenograft mouse models were constructed to explore the effects of ARHGAP9 on CRC in vivo. The expressions of PI3K/AKT/mTOR-activating factors and epithelial-mesenchymal transition (EMT)-related factors were all determined using western blot. LY294002 was employed to block PI3K/AKT/mTOR pathway in CRC cells. The expression of ARHGAP9 was down-regulated in CRC tumor tissues and cell lines when compared to normal tissues and cells. The over-expression of ARHGAP9 inhibited cell proliferation, invasion, migration and EMT in CRC cell lines while the knockdown of ARHGAP9 promoted them. In addition, ARHGAP9 up-regulation inhibited the activation of PI3K/AKT/mTOR signaling pathway in CRC cell lines while ARHGAP9 down-regulation led to an opposite effect. The over-expression of ARHGAP9 suppressed CRC tumor growth in vivo. When the PI3K/AKT/mTOR pathway was blocked in CRC cells, the effects of ARHGAP9 knockdown on cell proliferation, migration, invasion and EMT were all overturned. ARHGAP9 inhibited the malignant phenotypes of CRC cells via interdicting PI3K/AKT/mTOR signaling pathway.