A major immune evasion strategy of tumor cells is the establishment of an immunosuppressive tumor microenvironment through the selective recruitment of pro-tumor immune cells and the exclusion of anti-tumor immune cells. However, the underlying cell trafficking mechanisms that govern this process are incompletely understood. Chemerin is a chemoattractant that, when expressed or presented in tumors, selectively recruits CMKLR1+ anti-tumor leukocytes in tumor tissues, resulting in decreased tumor growth rates. Our preliminary data show that B16 melanoma tumor growth is reduced in mice lacking the atypical (non-signaling) chemerin receptor CCRL2. I hypothesize that 1) CCRL2, by binding and sequestering chemerin away from tumor tissue, inhibits chemerin-dependent leukocyte recruitment into B16 tumor tissue and 2) therapeutic intervention with CCRL2-blocking antibodies should recapitulate CCRL2-deficiency and unleash chemerin-dependent anti-tumor immunity.
In Aim 1, the anti-tumor effects of CCRL2 deficiency will be evaluated in two in vivo tumorigenesis models: B16 melanoma and JC adenocarcinoma.
Aim 2 is to define the in vivo mechanisms of CCRL2- dependent enhancement of tumor growth. Specifically, I will determine whether CCRL2 on stromal or hematolymphoid cells is necessary or sufficient to facilitate tumor growth. Moreover, I will test the hypothesis that CCRL2 facilitates tumor growth by sequestering chemerin, preventing the attractant from reaching or establishing a functional attractant gradient within tumor tissues.
In Aim 3, I will evaluate the pre-clinical efficacy of antibody-mediated blockade of CCRL2 using in vivo tumor growth models. I will use the established B16 melanoma model and/or JC adenocarcinoma models to assess in vivo tumor growth. In order to address the mechanistic role of hematolymphoid versus stromal cells in the CCRL2 effect, bone marrow (BM) chimeric mice will be generated by reconstituting irradiated wild type or CCRL2 KO mice with wild type or CCRL2 KO bone marrow cells. To assess whether the effect of CCRL2 deficiency on tumor growth is dependent on chemerin-mediated recruitment of CMKLR1pos cells, double KO mice (CCRL2/chemerin-double KO and CCRL2/CMKLR1 double KO) will be compared to single KO mice for their ability to support tumor growth. Finally, I will evaluate the therapeutic efficacy of antagonistic antibodies against CCRL2 using in vivo tumor models. By targeting an endogenous host-cell expressed antigen to block inhibition of anti-tumor cell recruitment, anti-CCRL2 therapy will likely synergize with or at least complement existing cancer immunotherapies, which target mechanisms of activation of hematolymphoid cells. The proposed research will provide crucial mechanistic insights and proof-of-concept data for the potential clinical applications of anti- CCRL2 therapy.
Harnessing a patient's immune system to destroy tumor cells is an effective therapeutic strategy; however, increasing evidence shows that tumors establish an immunosuppressive microenvironment, which ultimately prevents anti-tumor immune cells from entering into tumor tissue. This project builds on a recent discovery from my Sponsor and Co-Sponsor's labs that the chemoattractant, chemerin, leads to the selective, intra- tumoral recruitment of anti-tumor leukocytes (e.g. NK cells) when injected or locally expressed in tumors. The goals of this project are to 1) develop a mechanistic understanding of the tumor growth-promoting effects of CCRL2 (a chemerin receptor which we recently discovered to be a negative regulator of anti-tumor leukocyte recruitment into tumor tissue) and 2) perform proof-of-concept studies to evaluate antibody-mediated blockade of CCRL2 as a therapeutic approach to unleash anti-tumor immunity, a strategy with potential to synergize with or at least complement existing immunotherapies.
