Frequent Hypermethylation of RASSF1A, TSLC1, High Viral Load of Epstein-Barr Virus DNA in Nasopharyngeal Carcinoma, Matched Tumor-Adjacent Tissues

We examined the promoter hypermethylation of tumorsuppressor genes RASSF1A, TSLC1, quantitated EBV DNA load in nasopharyngeal carcinoma (NPC) tissues (T tissues), matched tumor-adjacent tissues outside 0.5 cm (P tissues), outside 1.0 cm (Z tissues) to evaluate the role of promoter hypermethylation of RASSF1A, TSLC1 as well as viral load in the pathogenesis of NPC. Methylation-specific polymerase chain reaction (PCR) for RASSF1A, TSLC1, quantitative real-time PCR analysis of EBV DNA were performed on matched T, P, Z tissues (n = 28) as well as chronic nasopharyngitis tissues (n = 8). Hypermethylated RASSF1A was frequently detected in the T (82%), P tissues (75%), but less frequently in Z tissues (46%). The average quantities of EBV DNA (copies/μg DNA) in matched T, P, Z tissues were 673,000, 90,000, 7000. The differences of promoter hypermethylation of RASSF1A, EBV viral load among T, P, Z tissues were statistically significant, with more frequent methylation, higher viral load detected when tissues examined were nearer to the NPC tissues. Our results suggest that aberrant hypermethylation of RASSF1A, high EBV load might be important events in NPC pathogenesis, they may be useful molecular diagnostic markers for this cancer.