Although PKC-mediated phosphorylation of Nrf2 at Serine 40 has been linked to HO-1 induction in cancer cell lines, PKCδ seems to be the isoform involved.45 Moreover, at least in hepatoblastoma cells, PKCε may phosphorylate Keap1 (INrf2) and so target Nrf2 for degradation. This evidence concerns the gene PRKCD and cancer.