Crosstalk between autophagy and apoptosis in initiating antitumor immune responses in human lymphoma cells

TL;DR

This study shows that ganoderic acid DM kills lymphoma cells and boosts immune responses by triggering cell death and autophagy while enhancing antigen presentation.

Contribution

The novel finding is that GA-DM synergistically activates apoptosis and autophagy while enhancing HLA class II antigen presentation in lymphoma cells.

Findings

GA-DM induces dose-dependent cytotoxicity in DLBCL cells with over 60% cell death at 30–40 μM.

GA-DM activates apoptosis via caspase-3 cleavage and induces autophagy via LC3-II upregulation.

GA-DM enhances HLA class II expression and CD4+ T cell activation, as shown by a 2.5-fold increase in IL-2 production.

Abstract

Despite advances in lymphoma treatment, resistance to conventional therapies and insufficient immune-mediated tumor clearance remain major challenges. This study investigates the dual antitumor mechanisms of the mushroom-derived triterpenoid, ganoderic acid DM (GA-DM), exploring its ability to induce programmed cell death while enhancing immune recognition in diffuse large B-cell lymphoma (DLBCL).

DLBCL cells (DB and Toledo) were treated with GA-DM (0–40 μM), and cell viability was assessed via MTS assay. Apoptosis was evaluated through caspase-3 activation and inhibition by ZVAD-FMK, while autophagy was measured via LC3 protein expression. Flow cytometry analyzed HLA class II surface expression and antigen presentation to CD4+ T cells (via IL-2 production), with autophagy’s role further confirmed using the inhibitor 3-MA.

GA-DM exhibited potent and dose-dependent cytotoxicity against DLBCL cells, with concentrations of 30–40 μM inducing over 60% cell death within 24 h. Mechanistic studies revealed that GA-DM activated the intrinsic apoptotic pathway, as evidenced by caspase-3 cleavage and the significant reduction in cell death upon ZVAD-FMK treatment. Concurrently, GA-DM treatment upregulated the autophagy marker LC3-II, indicating the induction of autophagy. Strikingly, GA-DM also enhanced the immunogenicity of lymphoma cells by increasing surface expression of HLA class II molecules. This led to improved antigen presentation and subsequent activation of CD4+ T cells, as demonstrated by a 2.5-fold increase in IL-2 production (amount of IL-2 in pg/mL) compared to untreated controls. The critical role of autophagy in this process was confirmed by the near-complete abrogation of HLA class II-mediated T-cell activation upon 3-MA treatment.

GA-DM synergistically induces apoptosis and autophagy while promoting immune-mediated tumor clearance through enhanced HLA class II antigen presentation. These findings highlight GA-DM as a promising multi-modal therapeutic candidate for lymphoma immunotherapy.

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