9788

MTSS1

MIM|MIMA|MIMB;metastasis suppressor 1;MTSS1;metastasis suppressor 1

metastasis suppressor YGL-1|metastasis suppressor protein 1|missing in metastasis protein

8p22

protein-coding

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.

BACKGROUND: Metastasis suppressor 1 (MTSS1) is proposed to function as a cytoskeletal-associated protein, which may play a role in the aggressiveness of cancer cells. Recent studies have demonstrated a clinical significance of MTSS1 in certain types of cancer, but its role in bladder cancer remains unknown. We investigated the expression of MTSS1 in normal and malignant human bladder tissues and its molecular interaction within bladder cancer cells. MATERIALS AND METHODS: The expression of MTSS1 in human bladder tissues and bladder cancer cell lines was assessed at both the mRNA and protein levels using reverse transcription-PCR (RT-PCR) and immunohistochemistry, respectively. Full-length MTSS1 cDNA was amplified from normal mammary tissues. The effect of MTSS1 overexpression on cellular functions was examined in bladder cancer cells using a variety of in vitro assays. RESULTS: Transitional cells of bladder tissues stained positively for MTSS1. However, cancer cells from tumour tissues did not stain for MTSS1. Similarly, in bladder cancer cell lines, MTSS1 was almost absent from T24 and RT112 cells, and the EJ138 cell line expressed a very low level of MTSS1. Overexpression of MTSS1 reduced the growth and adhesion of bladder cell lines in vitro. However, overexpression of MTSS1 had no bearing on the invasion and migration of bladder cell lines in vitro. CONCLUSION: MTSS1 is expressed at low levels or is absent from human bladder cancer cells. MTSS1 levels are inversely correlated with the growth and adhesion of bladder cancer cells in vitro. MTSS1 appears to be a potential tumour suppressor in human bladder cancer.