Baicalein Reverses Hypoxia-induced Resistance To 5-fluorouracil In AGS Cells Via Down-regulating The Function Of Drug Efflux Pump By HIF-1? Signaling Pathway

Objective: Gastric cancer(GC) was one of the leading causes of cancer-related mortality in digestive system. Chemotherapy was an important treatment for patients with advanced gastric cancer. Resistance to chemotherapy was one of the important factors responsible for poor prognosis of GC. Hypoxia was a major obstacle in the development of effective cancer chemotherapy. Hypoxia-inducible factor-1(HIF-1?),the major transcriptional factor significantly activated by hypoxia,played an important role in MDR. ABC transporter was a group located in the cell membrane of unidirectional substrate transporter,the study found that some of the members,including ABCB1(P-gp,MDR1), ABCG2(BCRP) and ABCC1(MRP1),can enhance the ability of efflux drugs, leading to multidrug resistance(MDR). Baicalein, a flavonoid separated from the root of scutellaria baicalensis,has been reported to reverse hypoxia-induced resistance to 5-fluorouracil in gastric cancer by our research team, but the related molecule mechanisms are largely unclear. We evaluated the effect of baicalein on hypoxia-induced 5-FU resistance in AGS cells and the possible molecular mechanisms.Method: To establish a hypoxia model,cell viability by CCK8 assay was examined to determine the MDR characteristic of AGS cells and the reversal effect of baicalein.Rhodamine123 staining was used to evaluate the effect of Baicalin on the drug efflux function of AGS cells under hypoxia conditions. Q-PCR and Western-Blot were performed to examine the m RNA and protein expression of HIF-1?,ABCB1(P-gp,MDR1),ABCG2(BCRP),ABCC1(MRP1).Results: According to the dose-response curve,10 and 20 ?M baicalein were not cytotoxic to AGS cells in both 24 h and 48h(cell viability > 89%). We would choose 10 and 20?M as optimum concentrations for subsequent studies; Baicalein could reverse hypoxia-induced resistance to 5-fluorouracil in AGS cells; Hypoxia can reduce the accumulation of rhodamine123 in AGS cells, which could be reversed by baicalein; With Q-PCR and Western-Blot analysis,we found that baicalein profoundly attenuated the expression of HIF-1?,MDR1,ABCG2,MRP1 in a dose-dependent manner.Conclusions: Baicalein can down-regulate the expression of MDR related indicators(MDR1,ABCG2,MRP1) through HIF-? signaling pathway,which may be one of the mechanisms that baicalein reversed 5-FU resistance in AGS cells under hypoxia condition.