Aberrant methylation of 5' CpG islands is thought to play an important role in the inactivation of tumor suppressor genes in several types of cancers. In non-small cell lung cancer (NSCLC), several genes are known to be frequently methylated and the correlation of their methylation with clinical features has been studied. We determined the methylation of p16, CDH13 and RAR-β which were reported to be methylated frequently in NSCLCs and HPP-1 which was known to be methylated in other types of cancers. The correlation between methylation and clinicopathological features were examined. The frequencies of methylation in NSCLCs were 20% for p16, 37% for CDH13, 34% for RAR-β, and 13% for HPP1. The methylation of p16 is correlated with smoking history and methylation of HPP1 was significantly more frequent in adenocarcinomas than in squamous cell carcinomas. This is the first description of aberrant methylation of the HPP1 gene in lung cancers and our data support the previous reports on methylation in NSCLCs and association with smoking.

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