Hypomethylation of long interspersed nuclear element-1 promoter is associated with poor outcomes for curative resected hepatocellular carcinoma

BACKGROUND: Epigenetic alterations are well documented in hepatocarcinogenesis. However, hypomethylation of long interspersed nuclear element 1(LINE-1) promoter and its relationship with clinicopathological features in hepatocellular carcinoma (HCC) remain unknown. METHODS: The bisulfite-specific PCR and DNA sequencing analysis was performed to assess the methylation status of LINE-1 promoter in a pilot cohort of 71 patients with HCC. Additionally, methylation levels of two hot CpG sites of LINE-1 promoter, site 7 and 18 were measured by real-time PCR and compared with clinicopathological parameters in a cohort of 172 HCC. All the patients included were in BCLC stage A or B. RESULTS: Most patients with HCC (87.3%) showed hypomethylation of LINE-1 promoter compared with HBV-related cirrhosis and normal controls (P < 0.001). The HCC patients with LINE-1 promoter hypomethylation had a median tumour-free survival (TFS) and overall survival (OS) post-resection of 22.0 (95% CI: 13.3–30.7) months and 35.0 (95% CI: 24.0–46.1) months, respectively, compared with 40 months and ∼60 months for those with LINE-1 promoter hypermethylation (P < 0.05). Multivariate analyses showed that the hypomethylation level at CpG site 7 and 18 of LINE-1 promoter, along with tumour size and tumour differentiation, was independently associated with both TFS and OS for patients with HCC after resection. CONCLUSION: Promoter hypomethylation of LINE-1, especially at the CpG site 7 and 18, was associated with a poor prognosis in HCC.