Abstract: bstract: Objective To investigate the effect of methyltransferase SETDB2 on the invasion and metastasis of live cancer and explore its mechanism. Methods Western blot, immunohistochemistry and Real-time PCR assays were performed to detect the expressions of SETDB2 protein and mRNA in liver cancer and the adjacent tissue specimens of 37 cases. The short hair pair RNA targeting SETDB2 (sh-SETDB2) and the corresponding empty vector (sh-NC) were transfected into MHCC97H cells. The invasion and migration ability of the two groups of cells were detected by Tanswell invasion assay and wound-healing assay. The gene chip was used to detect the expression of the altered genes after knocking down SETDB2. The mRNA expression of PTEN was detected by Real-time PCR. Western blot assay was used to detect the protein expressions of PTEN and H3K9me3. CHIP was used to detect the change of H3K9me3 in the promoter region of PTEN. The expression of PTEN was knocked down in shSETDB2-MHCC97H cells, and the invasion ability of cells was detected by the Tanswell invasion assay. Results (1) The results of Western blot and Real-time PCR assays showed that the expression levels of SETDB2 protein and mRNA were higher in the liver cancer tissues than those in the adjacent normal tissues. The expression level of SETDB2 was related to the histological grade and TNM stage of liver cancer. (2) The invasion and migration abilities were significantly lower in MHCC97H cells transfected with sh-SETDB2 than those in sh-NC group. (3) Microarray experiment, Western blot and Real-time PCR assays showed that PTEN was up-regulated after knocking down SETDB2. (4) The expression of H3K9me3 was decreased after knocking down SETDB2, and the appearance of H3K9me3 in PTEN promoter region was decreased as well. (5) Compared with the knockdown SETDB1, the invasive ability of cells was restored after both SETDB2 and PTEN were knocked down. Conclusion SETDB2 promotes the invasion and migration of hepatoma cells by downregulating the expression of PTEN.

Key words: carcinoma, hepatocellular, histone-lysine N-methyltransferase, neoplasm invasiveness, cell migration assays, PTEN phosphohydrolase, SETDB2