Methylation of PCDH19 predicts poor prognosis of hepatocellular carcinoma.

OBJECTIVE: Several members of protocadherins (PCDHs) have been identified as tumor suppressor genes in human carcinogenesis, but little is known about PCDH19. The aim of the present study was to assess the expression and methylation of PCDH19 in hepatocellular carcinoma (HCC).

METHODS: The RNA-seq data from The Cancer Genome Atlas Database were downloaded and used for analyzing PCDH19 expression in HCC patients and normal liver tissues. We collected 63 paired tumor and nontumor liver tissues from hepatitis B virus-related HCC patients. The expression of PCDH19 was detected by real-time quantitative RT-PCR assay. The methylation of PCDH19 gene was analyzed by DNA methylation-sensitive endonuclease digestion and the sequential quantitative PCR. The prognostic value of PCDH19 gene methylation was evaluated by Kaplan-Meier analyses.

RESULTS: PCDH19 expression was downregulated in HCC tissues and seven HCC cell lines compared to nontumor tissues. PCHD19 promoter was frequently hypermethylated in three (SMMC7721, Hep3B and SNU387) of seven HCC cell lines and 5-aza-dC treatment could significantly increased the PCDH19 expression in these methylated cells. In addition, HCC tumor tissues exhibited significantly increased PCDH19 hypermethylation both in frequency (30.15% vs 9.52%, P = 0.003) and in intensity (P = 0.002) compared to that in nontumor tissues. Kaplan-Meier survival analysis revealed that PCDH19 hypermethylation was correlated with the poor overall survival of HCC patients.

CONCLUSION: PCDH19 expression was downregulated in HCC, which was mediated at least in part by promoter hypermethylation. PCDH19 hypermethylation might present a potential prognostic marker in HCC patients.