Synergistic effects of histone deacetylase inhibitor chidamide and BCL-2 inhibitor venetoclax in activating the p53 pathway in diffuse large B-cell lymphoma

This study aimed to evaluate synergistic effects and molecular mechanisms of the histone deacetylase inhibitor chidamide combined with the BCL-2 inhibitor venetoclax in diffuse large B-cell lymphoma (DLBCL) cell lines. Human DLBCL cell lines (U2932, SUDHL-4) were cultured in vitro and treated with chidamide and venetoclax. Cell proliferation inhibition rates were measured using the CCK-8 assay, and IC50 values were calculated. Cells were also treated with a 5:1 combination of chidamide and venetoclax, along with p53 or p21 siRNA. Cell viability, HDAC activity, apoptosis, cell cycle, the amount of p53 and p21 proteins, and BCL-2-BIM binding were analyzed via CCK-8, enzyme activity assays, the Caspase 3/7 Activity Apoptosis Assay Kit, flow cytometry, RT-qPCR, western blot, and co-IP. The binding of p53 and p21 was verified by dual-luciferase reporter assay and chromatin immunoprecipitation. Chidamide and venetoclax exhibited dose- and time-dependent anti-proliferative effects in U2932 and SUDHL-4 cells, with IC50 values of 3.54 μM (chidamide) and 0.67 μM (venetoclax) in the SUDHL-4 cell line and 5.6 μM (chidamide) and 0.91 μM (venetoclax) in the U2932 cell line. Combination treatment significantly enhanced HDAC inhibition, histone H3/H4 acetylation, and p53 expression, leading to increased cell apoptosis. p53 knockdown partially reversed these effects and increased BCL-2/BIM complex formation. The combination also upregulated p53 expression to increase p21 expression, inducing G1/S phase arrest, which was partially reversed by p21 knockdown. To conclude, the chidamide-venetoclax combination synergistically activates the p53-p21 signaling pathway, leading to cell cycle arrest and apoptosis, representing a potential therapeutic strategy for DLBCL.