[Mechanism of polyphyllin Ⅰ targeting EGFR to affect proliferation and apoptosis of human breast cancer cells].

This study aims to investigate the molecular mechanism of polyphyllin Ⅰ(PPⅠ) inhibiting proliferation of human breast cancer cells. Human breast cancer BT474 and MDA-MB-436 cells were treated with different concentrations of PPⅠ, and then the effect of PPⅠ on cell proliferation was detected by MTT assay, trypan blue dye exclusion assay, real-time cell analysis, and clone forming assay, respectively. The apoptosis was detected by Annexin V-FITC/PI staining and then analyzed by flow cytometry. The change of mitochondrial membrane potential was detected by flow cytometry after fluorescent probe JC-1 staining. Western blot was used to detect protein expression and phosphorylation. Molecular docking was performed to detect the binding between PPⅠ and EGFR. The affinity between PPⅠ and EGFR was determined by drug affinity responsive target stability assay. The results indicated that PPⅠ inhibited the proliferation and colony formation of BT474 and MDA-MB-436 cells in a time-and concentration-dependent manner. The PPⅠ treatment group showed significantly increased apoptosis rate and significantly decreased mitochondrial membrane potential. PPⅠ down-regulated the expression of pro-caspase-3 protein, promoted the cleavage of PARP, and significantly reduced the phosphorylation levels of EGFR, Akt, and ERK. Molecular docking showed that PPⅠ bound to the extracellular domain of EGFR and formed hydrogen bond with Gln366 residue. Drug affinity responsive target stability assay confirmed that PPⅠ significantly prevented pronase from hydrolyzing EGFR, indicating that PPⅠ and EGFR have a direct binding effect. In conclusion, PPⅠ inhibited the proliferation and induced apoptosis of breast cancer cells by targeting EGFR to block its downstream signaling pathway. This study lays a foundation for the further development of PPⅠ-targeted drugs against breast cancer.