Tumor-derived HMGB2 induces M2-like macrophage polarization via TRIM65-mediated NLRP3 degradation to promote DLBCL progression

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin's lymphoma. Although standard immunochemotherapy is available, 30%-40% of patients develop refractory or relapsed disease, underscoring the need to elucidate the underlying mechanisms of therapy resistance. High mobility group box 2 (HMGB2) is overexpressed in DLBCL; however, its role in the pathogenesis of DLBCL and in mediating therapy resistance remains unclear.

Methods: HMGB2 expression and prognostic value in DLBCL were analyzed using public databases, validated by quantitative reverse transcription-PCR and western blot analysis. In vivo and in vitro HMGB2 knockdown models were constructed to explore its role in DLBCL. Macrophage-DLBCL co-culture systems were established to investigate HMGB2-mediated macrophage polarization. Transcriptome Sequencing was performed to identify downstream targets of HMGB2, with molecular mechanisms confirmed by western blot analysis, co-immunoprecipitation, and immunofluorescence. Exosome isolation and protease protection assays were used to determine the HMGB2 secretion pathway.

Results: HMGB2 is overexpressed in DLBCL and correlates with poor prognosis. While HMGB2 knockdown showed no cell-intrinsic effects in vitro, it significantly suppressed tumor progression in vivo by remodeling the tumor microenvironment. We identified a novel mechanism whereby exosomal HMGB2 derived from DLBCL cells upregulates the E3 ubiquitin Ligase tripartite motif containing 65 (TRIM65) in macrophages, promoting ubiquitin-mediated degradation of the NOD-like Receptor protein 3 (NLRP3) inflammasome. This cascade drives M2-like macrophage polarization and impairs phagocytic function. Therapeutic targeting of this axis restored macrophage phagocytosis and synergized with CD20 immunotherapy to enhance its antitumor efficacy.

Conclusion: Our study defines the HMGB2-TRIM65-NLRP3 axis as a pivotal immunosuppressive pathway in DLBCL. Targeting this axis represents a promising combinatory strategy to reprogram the tumor microenvironment and overcome therapy resistance.