Curculigoside mediates the STAT3/PD-L1 pathway to inhibit the proliferation, invasion, and immune escape of breast cancer cells.

Curculigoside (CUR) exhibits anti-inflammatory and anti-tumor effects in various cancers, but there are no research reports on the its effects and mechanisms on breast cancer. Our purpose was to detect the role of CUR in breast cancer and its underlying mechanism. The proliferation and invasion ability of MDA-MB-231 and BT549 cells were explored by CCK-8, EdU and Transwell assays. Protein levels were detected through immunofluorescence assay or western blot. The IFN-γ and IL-2 levels were analyzed via ELISA assay. The apoptosis level of cells was explored by flow cytometry. The roles of CUR in vivo were explored using the huPBMC-(M-NSG) mouse model. The specific experiments mainly included H&E staining, immunohistochemistry and western blot. CUR prominently suppressed the viability, proliferation rates and invasion abilities of MDA-MB-231 and BT549 cells, with IC values of 22.48 μM and 27.83 μM, respectively. CUR also decreased the level of Vimentin. CUR also reduced PD-L1 levels in MDA-MB-231 and BT549 cells. CUR increased the levels of IFN-γ and IL-2 in CD8 T cells and decreased the apoptosis level of CD8 T cells in the co-culture system with breast cancer cells. CUR decreased p-STAT3 and PD-L1 levels in breast cancer cells. The addition of Colivelin (STAT3 activator) reversed the various effects of CUR on MDA-MB-231 cells. Colivelin increased the nuclear level of STAT3. CUR significantly reduced the volume of subcutaneous tumors in vivo. The number of apoptosis cells within the tumor was increased after CUR treatment. CUR reduced the levels of Vimentin, p-STAT3 and PD-L1, but increased the IFN-γ level in the tumor tissues. CUR inhibited the proliferation, invasion and immune escape of breast cancer cells by suppressing the STAT3/PD-L1 pathway. CUR may be a potential drug for the treatment of breast cancer.