No Association between p53 Immunohistochemical Staining and RASSF1 or DAPK1 Hypermethylation in Non-Small Cell Lung Cancer

p53 mutations have been linked with shortened survival rates in non-small cell lung cancer (NSCLC). Hypermethylation of RASSF1 and DAPK1 genes, which are downstream targets of p53, has also been linked to a poor prognosis in lung cancer patients. We investigated whether p53 mutations, assessed as p53 stabilization by immunohistochemistry (IHC), were independent of DAPK1 and RASSF1 promoter hypermethylation. We examined 103 resected NSCLC tumors for which we had p53 IHC and RASSF1 and DAPK1 methylation data. p53 protein expression was determined by IHC and graded using a semi-quantitative scoring method. DAPK1 and RASSF1 methylations were determined on tumor blocks by MethyLight real-time PCR assays represented as the percent of methylated reference DNA (PMR). Our primary results found no evidence for an association between the p53 IHC score and RASSF1 and DAPK1 PMR values, P = 0.46 and P = 0.68, respectively.