P-gp inhibitor 30 is a potent P-gp inhibitor that can reverse multidrug resistance in breast cancer, rendering resistant cells sensitive to Doxorubicin (ADM). When used in combination with ADM, P-gp inhibitor 30 facilitates apoptosis and induces autophagy in resistant breast cancer cells, while also inhibiting cell proliferation, migration, and invasion. This inhibitor effectively suppresses tumor growth both in vitro and in vivo, making it valuable for research on drug-resistant breast cancer.

P-gp inhibitor 30 (compound A38) at a concentration of 0.1 μM can reverse resistance to ADM in MDA-MB-231/ADM cells, significantly lowering the ADM IC50 value from 785.46 μM to 2.05 μM. In a concentration-dependent manner (0.125-4 μM), it significantly inhibits P-gp ATPase activity at various concentrations. This inhibitor interacts with P-gp, suppressing its function without reducing its expression and stabilizes the protein to decrease degradation in MCF7/ADM cells under elevated temperatures. After 6 hours of treatment, P-gp inhibitor 30 markedly increases Rh123 expression in MCF7/ADM cells and ADM accumulation in MDA-MB-231/ADM cells while inhibiting Rh123 efflux. At concentrations of 0.1-1 μM for 24 hours to 15 days, when combined with ADM, it promotes apoptosis, and inhibits proliferation, migration, and invasion in resistant breast cancer cells (MCF7/ADM and MDA-MB-231/ADM), enhancing ADM sensitivity. Additionally, at 0.1 μM with ADM, it results in the accumulation of autophagosomes and significantly raises the expression of autophagy-related proteins, inducing cell death in MCF7/ADM and MDA-MB-231/ADM cells. In a 3D tumor spheroid model, P-gp inhibitor 30 applied for 1-10 days with ADM significantly reduces tumor volumes in MCF7/ADM and MDA-MB-231/ADM cell models.

When combined with ADM, the P-gp inhibitor 30 (2 mg/kg, intraperitoneal injection, administered every other day for 14 days) demonstrates antitumor effects in the MCF-7/ADM mouse model.