Nobiletin and its derivatives overcome multidrug resistance(MDR) in cancer:total synthesis and discovery of potent MDR reversal agents

Our recent studies demonstrated that the natural product nobiletin(NOB)served as a promising multidrug resistance(MDR)reversal agent and improved the effectiveness of cancer chemotherapy in vitro.However,low aqueous solubility and difficulty in total synthesis limited its application as a therapeutic agent.To tackle these challenges,NOB was synthesized in a high yield by a concise route of six steps and fourteen derivatives were synthesized with remarkable solubility and efficacy.All the compounds showed improved sensitivity to paclitaxel(PTX)in P-glycoprotein(P-gp)overexpressing MDR cancer cells.Among them,compound 29 d exhibited water solubility 280-fold higher than NOB.A drug-resistance A549/T xenograft model showed that 29 d,at a dose of 50 mg/kg co-administered with PTX(15 mg/kg),inhibited tumor growth more effective than NOB and remarkably increased PTX concentration in the tumors via P-gp inhibition.Moreover,Western blot experiments revealed that 29 d inhibited expression of NRF2,phosphorylated ERK and AKT in MDR cancer cells,thus implying 29 d of multiple mechanisms to reverse MDR in lung cancer.