Inherited variant alleles of the genes that encode glutathione-S-transferases (GSTM1 and GSTT1), proteins involved in metabolism of tobacco carcinogens (cytochrome P450-CYP1A1 gene), as well as other genes responsible for DNA damage repair (XPA, XPC, XPD, etc.)are associated with increased susceptibility to lung cancer [32,37]. Here, GSTM1 is linked to lung cancer.