Abstract

Abstract BCL6B is a potential tumor suppressor in human gastric cancer, but the regulation and mechanism of BCL6B in human hepatocellular carcinogenesis remain unclear. This study is to explore the epigenetic change and mechanism of BCL6B in human hepatocellular carcinoma (HCC). 14 hepatic cancer cell lines, 8 cases of normal hepatic tissue and 149 cases of HCC were employed. Semi-quantitative RT-PCR, methylation specific PCR (MSP), gene expression array, flow cytometry assay, colony formation, western blot and immunohistochemistry were used. BCL6B is methylated in 100% (14/14) of human HCC cell lines and 86.6% (129/149) of primary cancer samples. Methylation of BCL6B is associated with HBV positive (p<0.05). But no association was found with age, sex, tumor size, differentiation, TNM stage, recurrence and survival. Loss of BCL6B expression was found in 14 of completely methylated HCC cell lines. BCL6B was re-expressed after 5-aza-2′-deoxycytidine (5-AZA) treatment. Restoration of BCL6B expression suppressed cell proliferation, induced apoptosis and G1/S arrest in HCC cells. The expression of EGR1, a key component of p53 signaling, was increased after re-expression BCL6B in HCC cells. Re-expression of BCL6B activated P53 signaling and sensitized HepG2 and SNU449cells to 5-fluorouracil (5-FU). BCL6B is frequently methylated in human HCC and the expression of BCL6B is regulated by promoter region hypermethylation. BCL6B suppresses cell proliferation and induces apoptosis in HCC cells. BCL6B activates P53 signaling by increasing EGR1 expression in HCC. BCL6B sensitizes HCC cells to 5-FU by activating P53 signaling. Note: This abstract was not presented at the meeting. Citation Format: Xin Li, Jie Yu, Malcolm Brock, Qian Tao, James Herman, Ping Liang, Mingzhou Guo. Epigenetic silencing BCL6B inactivates p53 signaling and causes human hepatocellular carcinoma cell resist to 5-FU. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2950. doi:10.1158/1538-7445.AM2015-2950

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