CYP2B6 and neoplasm: In contrast, genes encoding members of the cytochrome P450 superfamily of enzymes CYP2B6, CYP4F2, and CYP4F3 showed negative correlations with AGR2 expression, as did PLA2G12B, expression of which is frequently downregulated in tumors, suggesting that PLA2G12B is a negative regulator of tumor progression [71].