MTSS1, a novel target of DNA methyltransferase 3B, functions as a tumor suppressor in hepatocellular carcinoma

• Published in: Oncogene Vol. 31; no. 18; pp. 2298 - 2308
• Main Authors: Fan, H, Chen, L, Zhang, F, Quan, Y, Su, X, Qiu, X, Zhao, Z, Kong, K L, Dong, S, Song, Y, Chan, T H M, Guan, X-Y
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.05.2012; Nature Publishing Group
• Subjects: Apoptosis; Bisulfite; Carcinoma, Hepatocellular - metabolism; Carcinoma, Hepatocellular - pathology; Cell Biology; Cell cycle; Cell Cycle Checkpoints - genetics; Cell Line, Tumor; Chromatin; Data processing; DNA (Cytosine-5-)-Methyltransferases - metabolism; DNA Methylation; DNA methyltransferase; DNA Methyltransferase 3B; DNA, Neoplasm - metabolism; Epigenetics; Gene Expression Regulation, Neoplastic; Gene silencing; Genes, Tumor Suppressor; Genomes; Hepatocellular carcinoma; Human Genetics; Humans; Immunoprecipitation; Internal Medicine; Liver cancer; Liver Neoplasms - metabolism; Liver Neoplasms - pathology; Medicine; Medicine & Public Health; Metastases; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Oncology; original-article; Polymerase chain reaction; Promoter Regions, Genetic; Promoters; S phase; Transcription; Tumor suppressor genes; Tumorigenicity; Tumors; DNMT3B; TSG; HCC; cell cycle; methylation; MTSS1
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2011.411

DNA methyltransferase 3B ( DNMT3B ) mediates gene silencing via epigenetic mechanisms during hepatocellular carcinoma (HCC) progression. We aimed to identify novel targets of DNMT3B and their potential regulatory mechanisms in HCC. Metastasis suppressor 1 (MTSS1) was one of the DNMT3B targets and selected for further study. DNMT3B overexpression was detected in 81.25% of clinical HCC specimens and was negatively associated with MTSS1 in HCC cells and clinical samples. The underlying mechanism by which DNMT3B silences MTSS1 was studied using a combination of methylation-specific polymerase chain reaction (PCR) and bisulfite genome sequencing, chromatin immunoprecipitation-PCR and luciferase reporter assays. We found that the MTSS1 promoter region was sparsely methylated, and the methylation inhibitors failed to abolish DNMT3B-mediated MTSS1 silencing. DNMT3B protein bound directly to the 5′-flanking region (−865/−645) of the MTSS1 gene to inhibit its transcription. The functional role of MTSS1 was investigated using in vitro and in vivo tumorigenicity assays. As a result, MTSS1 exerted tumor suppressor effects and arrested cells in the G2/M phase, but not the G1/S phase of the cell cycle when it was depleted or overexpressed in HCC cells. Taken together, MTSS1 , a novel target of DNMT3B , is repressed by DNMT3B via a DNA methylation-independent mechanism. MTSS1 was further characterized as a novel tumor suppressor gene in HCC. These findings highlight how DNMT3B regulates MTSS1 , and such data may be useful for the development of new treatment options for HCC.