AIMS: To assess differences in methylation profiles, and thus pathogenesis, between Epstein-Barr virus (EBV)-positive and negative nasopharyngeal carcinomas (NPCs). Also, promoter hypermethylation is a common phenomenon in early carcinogenesis to inactivate tumour suppressor genes. Since epigenetic changes are reversible, the therapeutic application of methylation inhibitors could provide treatment options.METHODS: We evaluated promoter hypermethylation profiles of 22 common tumour suppressor genes in 108 NPCs using methylation-specific multiplex ligation-dependent probe amplification. Correlation between methylation, clinicopathological features (including EBV) and survival was examined. Cluster analysis was also performed.RESULTS: Hypermethylation of RASSF1A and ESR1 was significantly more frequent in EBV-positive NPC, while hypermethylation of DAPK1 was more frequent in EBV-negative NPC. In logistic regression, age, with EBV-positive NPC occurring at earlier age, and RASSF1, with RASSF1 hypermethylation being more frequent in EBV-positive NPC, remained significant. In EBV-positive NPC, hypermethylation of RASSF1A predicted worse overall survival (OS) (HR 3.058,95% CI 1.027 to 9.107). In EBV-negative NPC, hypermethylated adenomatous polyposis coli (APC) was a predictor of poor disease-free survival (DFS) (HR 6.868, 95% CI 2.142 to 22.022).CONCLUSION: There are important epigenetic differences between EBV-negative and EBV-positive NPCs, with EBV-negative NPC having a more similar hypermethylation profile to other head and neck squamous cell carcinomas than EBV-positive NPC. Hypermethylation of RASSF1A might contribute to worse OS in EBV-positive NPC, and may be an important event in the pathogenesis of EBV-infected NPC. Hypermethylation of APC might contribute to worse DFS in EBV-negative NPC.

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Journal of clinical pathology
Department of Pathology

Ooft, M.L, van Ipenburg, J. (Jolique), van Loo, R. (Rob), de Jong, R. (Rick), Moelans, C.B, Braunius, W.W, … Willems, S.M. (2018). Molecular profile of nasopharyngeal carcinoma: analysing tumour suppressor gene promoter hypermethylation by multiplex ligation-dependent probe amplification. Journal of clinical pathology, 71(4), 351–359. doi:10.1136/jclinpath-2017-204661