TXNRD1 and neoplasm: In addition, calcitriol induced the expression of thioredoxin reductase 1 (TXNRD1), which reduces thioredoxin for its antioxidant function in prostate and breast cancer cells75,77 and glucose-6-phosphate dehydrogenase (G6PD), which produces NADPH for glutathione (GSH) regeneration in prostate and ovarian cancer cells78,79.