Increased CCL2/CCR2 axis promotes tumor progression by increasing M2 macrophages in MYC/BCL2 double-expressor DLBCL

The pathogenesis of MYC and BCL2 double expressor diffuse large B-cell lymphoma (DE-DLBCL) remains unclear. To investigate how MYC and BCL2 contribute to tumor aggressiveness, we analyzed tumors from 14 patients each with DE- and non-DE-DLBCL patients by whole transcriptome sequencing. Validation was performed using publicly available datasets, tumor tissues from 126 patients, DLBCL cell lines, and a syngeneic mouse lymphoma model. Our transcriptome analysis revealed significantly elevated mRNA levels of C-C motif chemokine ligand 2 (CCL2) and C-C chemokine receptor type 2 (CCR2) in DE-DLBCLs compared to non-DE-DLBCLs (Padj < 0.05). Transcriptomic analysis with public datasets and immunohistochemistry corroborated these findings, indicating heightened M2 macrophage presence but diminished T-cell infiltration in DE-DLBCLs compared to non-DE-DLBCLs (all, P < 0.05). CCR2 expression was observed mainly in tumor-infiltrating macrophages rather than DLBCL cells. Increased CCL2 and CCR2 expression were significantly associated with the poor prognosis of patients with DLBCL. In vitro analyses, MYChigh/BCL2high DLBCL cells showed higher CCL2 expression and secretion than MYClow/BCL2low cells. MYC and BCL2 increased CCL2 expression and secretion by upregulation of nuclear factor-κB p65 in DLBCL cells and the CCL2 promoted M2 polarization of macrophages. In a mouse lymphoma model, CCL2 contributed to the immunosuppressive microenvironment and tumor growth of MYChigh/BCL2high tumor. We demonstrated that the increased CCL2/CCR2 axis confers aggressiveness to DE-DLBCL by increasing M2 polarization and can be a potential therapeutic target.