Role of EHF in regulating B cell checkpoint molecule TIM-1 and development of CD11c+TIM-1+ Age-associated B cells 2301855

Abstract Introduction Aging is associated with an increased risk of cancer and immunosenescence, coinciding with the expansion of Age-associated B cells (ABCs). While T cell checkpoints are well-established targets, the landscape of inhibitory pathways in B cells, how they regulate anti-tumor immunity remain unclear. This study investigates the transcriptional regulation of the checkpoint molecule TIM-1 on ABCs and its impact on anti-tumor immunity. Methods We combined multi-tissue single-cell RNA-seq across aging, bulk RNA-seq, ATAC-seq, ChIP-qPCR, and a transcription factor CRISPR screen to identify regulators of TIM-1+ ABCs. We generated mice with B cell-specific deletion of the ETS-homologous factor (EHF) and assessed tumor growth, immune infiltration using B16-OVA melanoma and AOM/DSS colon adenocarcinoma models in both young and aged cohorts. Results We identified a progressive age-related expansion of TIM-1+ ABCs that co-express multiple inhibitory checkpoints, a phenotype mirrored by B cells in tumor-draining lymph nodes. We found that TLR9 signaling drives this phenotype and identified EHF as the pivotal transcriptional driver. EHF directly binds the Havcr1 (TIM-1) locus to induce expression. B cell-specific EHF deletion selectively eliminated TIM-1+ ABCs, unleashed Th1-skewed immunity, and enhanced CD8+ T cell activity. Consequently, EHF-deficient mice exhibited robust control of colorectal and melanoma tumors. Crucially, this heightened anti-tumor immunity persisted in aged mice, reversing age-associated immune suppression. Conclusion These findings define a previously unrecognized TLR9-EHF-TIM-1 checkpoint axis in B cells that emerges with age constraining anti-tumor immunity and age-associated inflammation. Targeting the regulatory function of EHF-driven ABCs provides a mechanistic rationale for novel therapeutic strategies to potentiate cancer immunotherapy, particularly in the elderly population where these cells accumulate. Funding Source This work was supported by the Gene Lay Institute of Immunology and Inflammation and grants from the National Institutes of Health (R01 AG080992, AI169075, AI185514, AI184980, P01 AI039671, P01 AI056299 to V.K.K; R01CA187975 to A.C.A.; R01CA282794 to V.K.K. and A.C.A.), GSK Award (“Role of B cells in regulating autoimmunity and anti-tumor immunity”) to V.K.K. and the Melanoma Research Alliance (926682, “Harnessing B cell checkpoints in melanoma” to V.K.K. and A.C.A). Y.-C.K. was supported by the postdoctoral fellowship from National Multiple Sclerosis Society (FG-2007-36929). Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)