Prognostic significance of RASSF1A promoter methylation on survival of non-small cell lung cancer patients treated with gemcitabine

Abstract

The epigenetic inactivation of genes plays an important role in lung cancer. We have investigated the methylation status of the promoter region of seven genes (APC1A, DAPK, FHIT, p14ARF, p16INK4a, RARβ, RASSF1A) in serum DNA of NSCLC patients. The objective of our study was to reveal the influence of such alterations on overall survival. Blood samples were drawn pretherapeutically. Genomic DNA was purified from serum, treated with sodium bisulfite and hypermethylation was detected by a nested methylation-specific PCR in a group of 92 patients with histologically confirmed stage IIIB and IV NSCLC. All patients received gemcitabine first-line alone or in combination with other drugs. The vast majority (n=87) showed at least one epigenetic alteration. The methylation frequencies of individual genes varied between 25.9 and 47.3%. The hypermethylation status of none of the genes had a significant influence on median overall survival of the total population. In contrast, patients with a methylated RASSF1A gene who showed a partial response survived significantly longer (33.6±10.4month) compared to those with a wild-type allele (12.9±4.7month, P=0.0045). This effect became even more pronounced in combination with p14ARF (P=0.0004). This difference was not seen in patients with stable or progressive disease. A multivariate analysis confirmed that RASSF1A methylation was an independent prognostic factor. Our results show that the hypermethylation frequency of single genes and the accumulation of epigenetic alterations in individual samples of NSCLC patients may vary considerably. Molecular parameters such as hypermethylation of RASSF1A or p14ARF may be useful prognostic markers in subpopulations.