SH003 overcomes drug resistance and immune checkpoints by inhibiting JAK-STAT3 signaling in MCF7/ADR cells

Abstract Background Breast cancer has the most commonly diagnosed malignancy cancer worldwide in women and has a high mortality. Various anticancer drugs to treat breast cancer have been developed and tested but have failed because of drug resistance. Objectives The efficacy of SH003 against doxorubicin-resistant MCF/ADR cells has not been evaluated. In this study, we aimed to examine whether SH003 could efficiently prevent the proliferation of MCF7/ADR cells. Methods Cell viability was measured by an MTT assay. Analysis of cell cycle arrest was performed by flow cytometry. Induction of apoptosis by SH003 was measured by an annexin V-FITC/PI assay. Levels of p-STAT3, p-PD-L1, MDR and caspases were measured by western blot analysis. mRNA expression levels of MDR1, MRP1, -2, -3, -4, -5, -6, -9, BCRP and PD-L1 were measured by RT-PCR. Nuclear staining of STAT3 was measured by immunocytochemistry. The expression levels of VEGF, MMP-2 and MMP-9 were measured by ELISA. Results SH003 inhibited the proliferation of MCF7/ADR cells and induced their sub-G1 cell cycle arrest. SH003 also induced apoptosis, regulated apoptotic molecules, caused morphological changes and inhibited colony formation in MCF7/ADR cells. Furthermore, SH003 suppressed STAT3 transcriptional activity and, more importantly, reduced the cytokine levels of VEGF, MMP-2 and MMP-9 in MCF7/ADR cells. SH003 decreased the protein expression of PD-L1 and MDR1. Additionally, SH003 reduced the mRNA expression of PD-L1; MDR1; MRP1, -2, -3, -4, -5, -6, and -9; and BCRP. Conclusion Our results clearly demonstrate that SH003 inhibits cell growth and induces apoptosis by inhibiting STAT3 signaling. Additionally, SH003 decreased the levels of MDR1 and PD-L1 by inhibiting STAT3 signaling in MCF7/ADR breast cancer cells. These results support the possibility that SH003 could be useful as an herbal medicine to treat doxorubicin-resistant breast cancer.