Promoter hypermethylation profile of tumor‐associated genes p16, p15, hMLH1, MGMT and E‐cadherin in oral squamous cell carcinoma

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Abstract
Aberrant promoter hypermethylation of tumor‐associated genes leading to their inactivation is a common event in many cancer types. Using a sensitive restriction‐multiplex PCR method, we studied the promoter hypermethylation profile of the p16, p15, hMLH1, MGMT and E‐cad genes in oral squamous cell carcinoma (OSCC) of Indians. We analyzed a total of 51 samples for the p15 tumor‐suppressor gene and 99 samples for each of the remaining genes. Our studies indicate an incidence of promoter hypermethylation of 23% each for p16 and p15, 8% for hMLH1, 41% for MGMT and 35% for E‐cad. We observed aberrant hypermethylation of the promoter region of at least 1 of these genes in 74.5% of cases (n = 51) for which all the 5 genes were studied. Abnormal methylation was detected in tumors irrespective of stage and location in the oral cavity, whereas no abnormal methylation was detectable in normal oral squamous tissues obtained from 25 OSCC patients. Detection of aberrant hypermethylation patterns of cancer‐associated genes listed above is therefore suitable for diagnosis of OSCC in individuals at high risk for this disease.