GSTM1 and renal cell carcinoma: However, this refers only to GSTM1-null genotype as individual risk factor for RCC, while it has been suggested that when present together with polymorphisms in certain genes related to activation or detoxification of renal carcinogens (CYP1A1, GSTT1, GSTP1, NAT2), GSTM1-null genotype is associated with risk of RCC [30].