CAR T cell-driven induction of iNOS in tumor-associated macrophages promotes CAR T cell resistance in B cell lymphoma

Chimeric antigen receptor (CAR) T cell therapies have revolutionized B cell malignancy treatment, but subsets of patients with large B cell lymphoma (LBCL) experience primary resistance or relapse after CAR T cell treatment. To uncover tumor microenvironment (TME)-induced resistance mechanisms, we examined patients’ intratumoral immune infiltrates and observed that elevated levels of immunoregulatory macrophages in pre-infusion tumor biopsies are correlated with poor clinical responses. CAR T cell-produced interferon-gamma (IFN-γ) promotes the expression of inducible nitric oxide synthase (iNOS, NOS2) in immunoregulatory macrophages, impairing CAR T cell function. Mechanistically, iNOS-expressing macrophages upregulated the p53 pathway, mediating apoptosis and cell cycle arrest in CAR T cells, while downregulating the MYC pathway involved in ribosome biogenesis and protein synthesis. Furthermore, CAR T cell metabolism is compromised by depletion of glycolytic intermediates and rewiring of the TCA cycle. Pharmacological inhibition of iNOS enhances the CAR T cell treatment efficacy in B cell tumor-bearing mice. Notably, elevated levels of iNOS+CD14+ monocytes were observed in leukaphereses of patients with non-durable response to CAR T cell therapy. These findings suggest that mitigating iNOS in tumor-associated macrophages (TAMs) by blocking IFN-γ secretion from CAR T cells will improve outcomes for LBCL patients.