MPO and lung cancer: Candidate gene approach studies demonstrated that polymorphisms in genes encoding for xenobiotic metabolizing enzymes such as glutathione S-transferase M1 (GSTM), glutathione S-transferase theta 1 (GSTT1), myeloperoxidase (MPO), cytochrome P450 family 1 subfamily A member 1 (CYP1A1) and cytochrome P450 family 2 subfamily E member 1 (CYP2E1), and manganese superoxide dismutase (SOD2) are associated with asbestos-related lung cancer risk [9,15].