NQO1 and cancer: Rux blocks JAK signalling upstream of STAT3 and thus inhibits its phosphorylation and activation, and Napa is a cancer stem cell inhibitor that affects STAT3 activation and has been shown to be a substrate of NAD(P)H:quinone oxidoreductase‐1 (NQO1) and to a lesser extent P450 oxidoreductase (POR).15, 16, 17