Targeting P‐glycoprotein and SORCIN: Dihydromyricetin strengthens anti‐proliferative efficiency of adriamycin via MAPK/ERK and Ca2+‐mediated apoptosis pathways in MCF‐7/ADR and K562/ADR

Recently, a new target Ca2+‐binding protein SORCIN was reported to participate in multidrug resistance (MDR) in cancer. Here we aim to investigate whether dihydromyricetin (DMY), a dihydroflavonol compound with anti‐inflamatory, anti‐oxidant, anti‐bacterial and anti‐tumor actions, reverses MDR in MCF‐7/ADR and K562/ADR and to elucidate its potential molecular mechanism. DMY enhanced cytotoxicity of adriamycin (ADR) by downregulating MDR1 mRNA and P‐gp expression through MAPK/ERK pathway and also inhibiting the function of P‐gp significantly. Meanwhile, DMY decreased mRNA and protein expression of SORCIN, which resulted in elevating intracellular free Ca2+. Finally, we investigated co‐administration ADR with DMY remarkably increased ADR‐induced apoptosis. Further study showed DMY elevated ROS levels and caspase‐12 protein expression, which signal apoptosis in endoplasmic reticulum. At the same time, proteins related to mitochondrial apoptosis were also changed such as Bcl‐2, Bax, caspase‐3, caspase‐9, and PARP. Finally, nude mice model also demonstrated that DMY strengthened anti‐tumor activity of ADR in vivo. In conclusion, DMY reverses MDR by downregulating P‐gp, SORCIN expression and increasing free Ca2+, as well as, inducing apoptosis in MCF‐7/ADR and K562/ADR. These fundamental findings provide evidence for further clinical research in application of DMY as an assistant agent in the treatment of cancer. When ADR co‐administrated with DMY P‐gp and SORCIN were reduced and then induced, respectively, in increasing of intracellular ADR and calcium. Finally apoptosis was triggered through mitochondria, endoplasmic reticulum pathway.