Pokemon enhances proliferation, cell cycle progression and antiapoptosis activity of colorectal cancer independently of p14ARF-MDM2-p53 pathway

Pokemon has been showed to directly suppress p14(ARF) expression and also to overexpress in multiple cancers. However, p14(ARF)-MDM2-p53 pathway is usually aberrant in colorectal cancer (CRC). The aim is to confirm whether Pokemon plays a role in CRC and explore whether Pokemon works through p14(ARF)-MDM2-p53 pathway in CRC. Immunohistochemistry for Pokemon, p14(ARF) and Mtp53 protein was applied to 45 colorectal epitheliums (CREs), 42 colorectal adenomas (CRAs) and 66 CRCs. Pokemon was knocked down with RNAi technique in CRC cell line Lovo to detect mRNA expression of p14(ARF) with qRT-PCR, cell proliferation with CCK8 assay, and cell cycle and apoptosis with flowcytometry analysis. The protein expression rates were significantly higher in CRC (75.8 %) than in CRE (22.2 %) or CRA (38.1 %) for Pokemon and higher in CRC (53.0 %) than in CRE (0) or CRA (4.8 %) for Mtp53, but not significantly different in CRC (86.4 %) versus CRE (93.3 %) or CRA (90.5 %) for p14(ARF). Higher expression rate of Pokemon was associated with lymph node metastasis and higher Duke's stage. After knockdown of Pokemon in Lovo cells, the mRNA level of p14(ARF) was not significantly changed, the cell proliferation ability was decreased by 20.6 %, cell cycle was arrested by 55.7 % in G0/G1 phase, and apoptosis rate was increased by 19.0 %. Pokemon enhanced the oncogenesis of CRC by promoting proliferation, cell cycle progression and antiapoptosis activity of CRC cells independently of p14(ARF) MDM2-p53 pathway. This finding provided a novel idea for understanding and further studying the molecular mechanism of Pokemon on carcinogenesis of CRC.