Resveratrol as a BCL6 natural inhibitor suppresses germinal center derived Non-Hodgkin lymphoma cells growth

Abstract

Non-Hodgkin lymphomas (NHL), including diffuse large B-cell lymphoma (DLBCL), Burkitt lymphoma (BL), and follicular lymphoma (FL), predominantly arise from B cells undergoing germinal center (GC) reactions. The transcriptional repressor B-cell lymphoma 6 (BCL6) is indispensable for GC formation and contributes to lymphomagenesis via its BTB domain-mediated suppression of target genes. Dysregulation of BCL6 underpins the pathogenesis of GC-derived NHL. While pharmacological targeting the BCL6-BTB domain has shown therapeutic promise, natural product-based inhibitors remain underexplored. In this study, resveratrol, a polyphenolic compound derived from grapes, was identified as a potent BCL6 inhibitor through a comprehensive screen of traditional Chinese medicine monomers using Homogeneous Time-Resolved Fluorescence (HTRF) assay. As a BCL6 natural inhibitor, resveratrol effectively disrupted the BCL6/SMRT interaction, reactivated suppressed gene expression, and inhibited the proliferation of GC-derived NHL cells. It also exhibited synergistic efficacy when combined with EZH2 and PRMT5 inhibitors. In vivo, resveratrol suppressed GC formation, reduced follicular helper T-cell frequencies, impaired class-switch recombination, and disrupted immunoglobulin affinity maturation. Furthermore, it markedly inhibited the progression of GC-derived NHL in animal models. Our findings demonstrate that resveratrol functions as a natural BCL6 inhibitor with significant therapeutic potential for the treatment of GC-derived NHL.

Keywords: BCL6; BTB domain; GC; NHL; Natural inhibitor.

Fig. 1

Resveratrol is identified as a BCL6^BTB natural inhibitor. A Schematic diagram of HTRF assay screening for BCL6 inhibitors. B Chemical structure of resveratrol. C Resveratrol and FX1 were tested in HTRF assay for inhibition of the BCL6-SMRT interaction. (D) Schematic diagram of dual-luciferase reporter assay. E Luciferase reporter assay was performed to test the activity of resveratrol against the repressor activity of BCL6^BTB. When plasmids (GAL₄)₅-TK-LUC combined with GAL₄-DBD-BCL6^BTB, the fluorescence expression was inhibited. After adding 100 μM of resveratrol, the fluorescence was restored. F K_D of resveratrol binding to BCL6 BTB protein determined by an SPR assay. G Molecular docking model predicted that resveratrol bound to the BCL6-BTB domain. H The binding affinities of resveratrol and BCL6 mutants

Fig. 2

Resveratrol induces de-repression of BCL6 target genes p53, ATR, CXCR4, CDKN1A, CD69 and CD80. (*, P < 0.05; **, P < 0.01; ***, P < 0.001 versus control)

Fig. 3

Resveratrol blocks GC formation in vivo. C57BL/6 mice were immunized with NP₁₈-CGG and treated with resveratrol at a dosage of 100 mg/kg/d. A Flow cytometry analysis revealed that the proportion of GC B cells in the resveratrol group decreased. B Percentage of Tfh cells was reduced in the resveratrol group by flow cytometry. C Resveratrol affected class-switch recombination in flow cytometry analysis. D Resveratrol decreased the titers of the NP-specific immunoglobulin G1 in serum measured by ELISA with NP₅-BSA and NP₂₃-BSA. (*, P < 0.05; **, P < 0.01 versus control)

Fig. 4

Resveratrol inhibits GC-derived NHL cells growth in vitro. A Anti-proliferative effects of resveratrol on GC-derived NHL cell lines and normal cell lines after 72 h of treatment. B IC₅₀ values of resveratrol in lymphoma cell lines and normal cell lines after 72 h of treatment. C–D Resveratrol synergized with EZH2 inhibitor GSK343 or PRMT5 inhibitor GSK591 to inhibit SUDHL4 cells growth. The combination indexes (CIs) are shown at the indicated concentrations

Fig. 5

Resveratrol suppresses BCL6-driven lymphoma growth in vivo. A SUDHL4 xenograft mouse model. B Antitumor effects of resveratrol on SUDHL4 xenograft mouse model. Tumor volumes evaluated once every 3 days for a total of 15 days. C Tumor burden was weighed. D The body weight of the mice was measured every 3 days. E mRNA expression of the BCL6 target genes p53, ATR, CXCR4, CDKN1A, CD69 and CD80 from tumors was measured by RT-qPCR assays. (*, P < 0.05; **, P < 0.01; ***, P < 0.001 versus control)