CDC20, A Hypermethylated Gene in Senescent Cells, is Associated with Hepatocellular Carcinoma Prognosis

Abstract BackgroundHepatocellular carcinoma (HCC) is a malignancy with poor outcome. As an anti-tumor mechanism, the methylation pattern of gene in senescent cells is different from that in malignant ones deriving from physically senescent cells. Therefore, it is possible that aberrantly methylated senescence-associated genes could predict the prognosis of HCC patients.MethodsDifferentially expressed genes with aberrant methylation were explored in two senescent cell datasets and were selected as senescence-associated genes (SAGs). And we used the proliferation, cell cycle, and senescence β-galactosidase assay to detect the effects of downregulated CDC20, a SAG, on cell cycle arrest and cellular senescence. Then, we investigated the relationship between the expression and methylation of CDC20 in senescent and proliferating HCC cells which was treated by 5-Azacytidine demethylation and in HCC patients from The Cancer Genome Atlas database. Also, we combined the methylation and expression levels of CDC20 to evaluate the prognosis of CDC20. Finally, pyrophosphate sequencing was performed to validate the different methylation of CDC20.ResultsWe found one of 49 SAGs, named cell division cycle 20 (CDC20), to be downregulated with hypermethylation in senescent HCC cells but upregulated with hypomethylation in proliferating HCC cells. Then, restoration of CDC20 expression was observed after demethylation treatment. Moreover, knockdown of CDC20 was found to induce cell cycle arrest and cellular senescence. Furthermore, the expression of CDC20 was found to be negatively correlated with its methylation, and hypomethylation of CDC20 was found to have a significantly shorter overall survival. Finally, pyrophosphate sequencing results showed that cg16147196 in CDC20 has a remarkably higher methylation level in senescent HCC cells than that in the proliferating HCC cells. ConclusionsIn conclusion, our study indicated that CDC20, a hypermethylated gene in senescent cells, could be considered as an alternative prognostic marker in HCC.