KEAP1 and cancer: In our previous work, we designed and synthesized PBQC which can sense glutathione (GSH) by PET process, discriminate GSH from cysteine and homocysteine, and specifically consume intracellular glutathione.32 The glutathione level is increased in many cancer cells,4 and interfering with intracellular glutathione of cancer cells can significantly promote the cell apoptosis.7 It was also reported that glutathione depletion induced the S-glutathionylation of Keap-1 protein and markedly increased Nrf2 activity.27 In this study, we found that PBQC could consume the intracellular glutathione.