The Correlation Between Lung Cancer Susceptibility, Drug Response and Genetic Polymorphism

Lung cancer is the leading cause of cancer deaths in Taiwan. The carcinogen in the environment is a key role in the development of lung cancer, and one of its main resource is tobacco. Activated carcinogens in the organism lead to mutations of crucial oncogenes resulting in tumor development. Genes such as Cytochrome P-450 family, GST (glutathione S-transferase) family, UGT (UDP-Glucuronosyltransferase) family, ERCC-1(excision repair cross-complementing rodent repair deficiency),ERCC-4 and ERCC-5,are encoding antioxidant enzymes or involving in the DNA repair process and the production of some transcription factors. In recent years, many studies have shown the correlation between these genes and the susceptibility of lung cancer. Each gene has a different role in the tumor development pathway. CYP, UGT, GST, NAT2 (N-acetyltransferase 2) and NQO1(NAD(P)H:quinono oxidoreductase 1) involve in the production of antioxidant enzymes. The antioxidant enzymes can detoxificate hydrogen peroxide or defense against oxidative stress. However, the genetic polymorphisms may influence the function of detoxification, which cause the increase in the susceptibility of lung cancer. P53 and MDM2 genes play important roles in the production of tumor-suppression proteins and the regulation of transcription factors, which may regulate the growth and the apoptosis of cell cycle and influence the susceptibility of lug cancer. The polymorphisms in ERCC genes may cause the damage in the DNA repair process which might also cause increase in lung cancer susceptibility. The overexpression of epidermal growth factor receptor is highly correlated with increasing risk of the non-small cell lung cancers. The overexpression may induce the proliferation of cancer cells and the inhibition of the apatosis. Therefore, in recent years, EGFR has been widely studied as the new target of the drugs and the susceptibility of the lung cancer. In addition,the genetic polymorphisms in drug metabolism channel proteins, like OCT2 (organic cation transporter), ATP7A, ATP7B and ABC (ATP-binding cassette) transporter may have influence on the metabolism, the efficacy and the toxicity of the drugs.