A novel redox cycle diverts cells from oncogene-induced senescence into cancer.

Igelmann et al. report a novel metabolic cycle, which they name HTC, that converts NADH into the key antioxidant factor NADPH. The HTC is repressed by the tumor suppressors p53 and RB, and this determines whether oncogene-expressing cells undergo senescence (HTCoff) or malignant transformation (HTCon).