IDDF2021-ABS-0177 RNF135 promoter methylation is associated with immune infiltration and prognosis in hepatocellular carcinoma

Background RING finger protein 135 (RNF135) has an important role in the occurrence of many cancers, however, the regulation and function of RNF135 in hepatocellular carcinoma (HCC) remains unknown. Methods The promoter methylation status and mRNA expression of RNF135 were evaluated by methylation-specific PCR and real-time PCR in HCC cell lines and tissues, and further analyzed from The Cancer Genome Atlas database. Transwell migration, wound healing assay, cell viability, and colony formation assay were performed to investigate the function of RNF135. GSEA analysis, TIMER database and ESTIMATE algorithm were used to decipher the associated pathway and immune infiltration. The survival analysis was applied to assess the prognostic value of RNF135. Results RNF135 expression was downregulated in 5 of 8 HCC cell lines and HCC tissues, and was negatively correlated with its promoter hypermethylation. Demethylating regent decitabine restored RNF135 expression on the cellular level. Knockdown of RNF135 expression enhanced the migration of HCC cells, while RNF135 overexpression repressed cell migration. Bioinformatics analysis revealed a positive relationship between RNF135 expression and six immune cell infiltrates (B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, and dendritic cells). Survival analysis disclosed that RNF135 hypermethylation is independently associated with poor clinical outcomes in HCC. Conclusions Decreased RNF135 expression driven by promoter hypermethylation is frequently occurred in HCC and associated with prognosis of HCC. RNF135 functions as a tumor suppressor and involves in tumor immune microenvironment in HCC.