StemRegenin-1 Reverses Drug Resistance of MCF-7/ADR Cells via AhR/ABC Transports and AhR/UGTs Pathways

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Objectives: Drug resistance reduces the antitumor efficacy of chemotherapy. Therefore, it is important to know how to reverse drug resistance. In this work, we investigated drug resistance reversal by StemRegenin-1(SR-1) in MCF-7/ADR cells and the mechanism by which it exerts its drug resistance effect. Methods: MTT test and protein blot were employed as the two main in vitro cell tests. The cells were treated with SR-1 and ADM to detect the changes in their proteomics, and then the effects of AhR downstream proteins, glucuronidase, and drug-resistant proteins were verified. The accumulation of ADM in the combined cells and its effect on the cell cycle were detected by flow cytometry. In vivo, a BALB/C mice xenograft test was conducted to observe the anti-tumor effect and side effects of the drug combination. Results: SR-1 combined with ADM inhibited cell proliferation and significantly decreased the expression of CYP1A1, UGT1A6, P-gP (ABCB1), and MRP1 (ABCC1). Furthermore, SR-1 caused apoptosis and cell cycle arrest. In vivo experiments showed that SR-1 significantly enhanced the antitumor effects of ADM and reduced the toxic effects of ADM. Conclusion: SR-1 inhibited AhR activity, decreased its downstream protein CYP1A1 and the expression of UGT1A6, P-gP, and MRP1 in MCF-7/ADR cells, and reversed drug resistance in MCF-7/ADR cells through AhR/ABC transports and AhR/UGTs pathways.