GSTM2 and meningioma: On average meningiomas expressed higher AOX1, GSTM and GSTP levels than astrocytomas (AOX1: t(39) = 2.2, p = 0.03, r = 0.33; GSTM: U = 74.5, p<0.001, r = 0.54; and GSTP1: U = 109, p = 0.009, r = -0.4) but lower CYP1A1 levels (t(39) = -2.7, p = 0.01, r = 0.39) (Figs 3 and 4).