Nitration of CCL2 disrupts the tumor-protective function of CCL2 in bladder cancer

Abstract

Abstract The chemokine CCL2 (C-C motif ligand 2) is best known for its ability to induce trafficking of immune cells by binding its primary receptor, CCR2. The recruitment of immunosuppressive monocytes by CCL2 promotes cancer in several tumor types. Surprisingly, we previously found an unanticipated protective role for CCL2 signaling in bladder cancer (BC). To determine if CCL2’s effect to suppress bladder tumor growth is dependent on T cells, we examined the effects of α-CCL2 antibody in wild-type versus T cell-deficient mice. The protective effect of CCL2 was lost in T cell-deficient mice and on T cell depletion in wild-type mice. Mixed bone marrow chimera experiments also showed that CCR2+ T cells were preferentially recruited by CCL2 to the bladder compared with CCR2− T cells suggesting that the protective effect of CCL2 in BC is through CCR2+ T cells. Most studies researching chemokines, including CCL2, in cancer assume the chemokine to be completely active and do not consider their different modified states which may be one of the critical reasons behind the failure of chemokines in clinical trials. We show for the first time that bladder tumors induce post-translational nitration of CCL2 and block T cell recruitment to the bladder which is restored by exogenous recombinant (r) CCL2 treatment. However, the chemical nitration of rCCL2 abolished this therapeutic efficacy of rCCL2 and was associated with decreased bladder T cell infiltration and more monocytes infiltration in BC. Our study analyzed the role of nitrated CCL2 in BC which explained certain paradoxes between CCL2 levels and patient outcomes in cancer. We also developed a novel BC treatment strategy using rCCL2 which should lead to effective combinations with existing BC immunotherapies. Supported by (1) the Mays Family Cancer Center at University of Texas Health San Antonio (P30 CA054174), (2) the Roger L. And Laura D. Zeller Charitable Foundation Chair in Urologic Cancer, (3) the Glenda and Gary Woods Distinguished Chair in GU Oncology, (4) the Max & Minnie Tomerlin Voelcker Fund, (5) CDMRP CA170270/P1P2, (6) Bladder Cancer Advocacy Network (BCAN), (7) Research Training Award (RP170345) from the Cancer Prevention & Research Institute of Texas (8) MSTP Program (NIH T32GM113896)