GSTM1 and nasopharyngeal carcinoma: The chr6 super loci containing the human leukocyte antigen (HLA) system has been linked to the pathogenesis of NPC [10], [11], [12], as have the cell cycle regulation genes cyclin D1 (CCND1) [13], p53[14], and carcinogen-metabolism gene glutathione S-transferase M1 (GSTM1) [15].