Mcl-1 is an important target protein for kaempferol from persimmon leaves in sensitizing ABT-199 to induce apoptosis in hepatoma cancer cells.

Overexpression of Mcl-1 causes hepatocellular carcinoma resistance to Bcl-2 inhibitors, but there are currently no direct Mcl-1 inhibitors available for clinical application. Our previous research demonstrated that kaempferol from persimmon leaves (KPL) can sensitize ABT-199 to inhibit liver cancer cell proliferation. This study further explored the effect of KPL sensitizing ABT-199 on liver cancer cell apoptosis and its potential mechanisms. The inhibitory effects of KPL and ABT-199, both individually and in combination, on the proliferation of HepG2, Huh7, and HCCLM3 cells were evaluated. Cell apoptosis and mitochondrial morphology were assessed with flow cytometry and confocal microscopy, respectively. Apoptosis and changes in Mcl-1 protein expression were evaluated after siMcl-1 knockdown. Molecular docking simulations were used to analyze the interactions of KPL and ABT-199, both individually and in combination, with Mcl-1 protein. The effect of KPL on Mcl-1 stability was investigated with proteasome inhibitor MG132. The results demonstrated that KPL showed a strong sensitizing effect on ABT-199 (CI value < 1), enhanced liver cancer cell proliferation inhibition and increased apoptosis rate. Combined treatment led to mitochondrial fragmentation and swelling, and significantly reduced Mcl-1 expression. siMcl-1 interference resulted in little difference in apoptosis rates and Mcl-1 expression between the combination treatment and untreated groups. Molecular docking revealed that KPL increased the affinity of ABT-199 for Mcl-1, whereas MG132 prevented KPL from downregulating Mcl-1 expression. These findings suggest that KPL enhances ABT-199-induced apoptosis in HCC cells by targeting Mcl-1 protein through increasing the affinity between ABT-199 and Mcl-1, while also promoting Mcl-1 degradation by affecting post-translational modifications.