GSTM1 and prostate carcinoma: Blood samples were collected for genotyping and they found that the association between HCA intake and prostate cancer risk could be modified by polymorphisms of the genes that encode for HCA metabolizing enzymes such as GSTT1, GSTM1, and MnSOD. Patients with two or more deletions of GSTT1 and GSTM1 genes were found to have a higher risk of prostate cancer.