GSTM1 and cancer: Various polymorphic genes that code enzymes involved in carcinogen biotransformation have been associated with cancer development.13, 14, 15, 16, 17, 18, 19, 20, 21, 22 Two genes in particular - GSTT1 and GSTM1 - that code phase II enzymes belonging to the glutathione S-transferases (GSTs) family seem relevant for susceptibility to head and neck squamous cell carcinoma; they detoxify carcinogenic tobacco smoke reactive metabolites.11, 12, 13, 15, 18, 20, 23