Smoking-related increase of O6-methylguanine-DNA methyltransferase expression in human lung carcinomas

Eighty-three non-small cell lung carcinomas (NSCLC) of previously untreated patients were analysed for expression of O6-methylguanine-DNA methyltransferase (MGMT) by means of immunohistochemistry. Expression of MGMT was detected in 62 of 83 tumours (75%). There was a significant difference in MGMT staining between smokers and non-smokers (P = 0.001). Tumours of smokers expressed more frequently MGMT than tumours of non-smokers. There was a trend of MGMT expression to be higher in tumours of patients smoking >20 cigarettes/day than patients smoking <20 cigarettes/day. Abstinence from smoking resulted in a significant decrease in MGMT expression (lin reg r = -0.59, P < 0.05). These results demonstrate that MGMT expression in human lung carcinomas is influenced by smoking habits of the patients.