Growth arrest-specific gene 2 suppresses hepatocarcinogenesis by intervention of cell cycle and p53-dependent apoptosis

BACKGROUND Growth arrest-specific gene 2 (GAS2) plays a role in modulating in reversible growth arrest cell cycle, apoptosis, and cell survival. GAS2 protein is universally expressed in most normal tissues, particularly in the liver, but is depleted in some tumor tissues. However, the functional mechanisms of GAS2 in hepatocellular carcinoma (HCC) are not fully defined. AIM To investigate the function and mechanism of GAS2 in HCC. METHODS GAS2 expression in clinic liver and HCC specimens was analyzed by real-time PCR and western blotting. Cell proliferation was analyzed by counting, MTS, and colony formation assays. Cell cycle analysis was performed by flow cytometry. Cell apoptosis was investigated by Annexin V apoptosis assay and western blotting. RESULTS GAS2 protein expression was lower in HCC than in normal tissues. Overexpression of GAS2 inhibited the proliferation of HCC cells with wide-type p53, while knockdown of GAS2 promoted the proliferation of hepatocytes (P < 0.05). Furthermore, GAS2 overexpression impeded the G1-to-S cell cycle transition and arrested more G1 cells, particularly the elevation of sub G1 (P < 0.01). Apoptosis induced by GAS2 was dependent on p53, which was increased by etoposide addition. The expression of p53 and apoptosis markers was further enhanced when GAS2 was upregulated, but became diminished upon downregulation of GAS2. In the clinic specimen, GAS2 was downregulated in more than 60% of HCCs. The average fold changes of GAS2 expression in tumor tissues were significantly lower than those in paired non-tumor tissues (P < 0.05). CONCLUSION GAS2 plays a vital role in HCC cell proliferation and apoptosis, possibly by regulating the cell cycle and p53-dependent apoptosis pathway.