XPC and lung cancer: Friedberg et al. (2000) found that rats with homozygous XPC mutation after exposure to chemical carcinogens are susceptible to liver cancer. These studies showed that the XPC gene plays a very important role in DNA damage repair and tumorigenesis, and its abnormal expression was related to the susceptibility of tumors. It is speculated that XPC gene expression is also related to the occurrence of lung cancer. Viktorsson et al. (2005) and Wu et al. (2007) found that expression of XPC is low in lung cancer, and the occurrence of lung cancer is related to the low expression of XPC.