METTL3 facilitates the progression of hepatocellular carcinoma by modulating the m6A level of USP7

Objective: To explore whether METTL3 was involved in the pathogenesis of hepatocellular carcinoma (HCC) by modulating the m6A level of USP7. Methods: We performed qRT-PCR and western blot assays to detect the expression level of METTL3 in HCC tissues and paired adjacent normal tissues, as well as HCC cell lines. The level of m6A in HCC tissues and cells was quantitatively analyzed by m6A RNA Methylation Quantitative Kit. We examined the effect of METTL3 on cell proliferation ability by CCK-8 and EdU assays, and examined cell migration and cell invasion ability by Transwell assay. It was predicted via bioinformatics tool that USP7 may undergo methylation in HCC. Subsequently, we performed qRT-PCR assay to detect the expression level of USP7 in HCC tissues and analyzed its correlation with the expression level of METTL3. We verified the regulatory relationship between METTL3/USP7 and transfected USP7 siRNA in cells to detect its effects on cell invasion, migration and proliferation. The regulatory effect of METTL3 on USP7 in HCC was analyzed by corresponding experiments. Results: The qRT-PCR results indicated that METTL3 was highly expressed in HCC tissues and cell lines. The level of m6A was remarkably increased in HCC tissues and cell lines. Besides, the elevated METTL3 expression was related to worse overall survival. The abilities of cell invasion, migration and proliferation were remarkably attenuated by down-regulation of METTL3 expression. Through bioinformatics analysis, it was found that USP7 might be regulated by METTL3 to undergo methylation modification. The qRT-PCR results showed that the USP7 was highly expressed in HCC tissues, and was positively correlated with the level of METTL3. Further experiments showed that down-regulation of USP7 could reduce cell proliferation, migration, and invasion. METTL3 could positively regulate the malignant phenotype of USP7 in HCC. Conclusion: METTL3 might regulate the expression of USP7 through m6A methylation and facilitate the invasion, migration and proliferation of HCC cells.