Abstract 2270: Recruitment of CD103+DCs via tumor-targeted chemokine delivery enhances efficacy of checkpoint inhibitor immunotherapy
Authors: Williford John-Michael , Ishihara Jun , Ishihara Ako , Mansurov Aslan , Swartz Melody A. , Hubbell Jeffrey A. 
Published: August 2019

Abstract
Checkpoint inhibitor antibody (CPI) therapy has demonstrated significant clinical benefit in a number of tumor types. Unfortunately, certain tumor characteristics, such as the lack of immune cell infiltration, often correlate with poor responses to CPI therapy. Studies have identified C-C Motif Chemokine Ligand 4 (CCL4) as a key molecule necessary for the recruitment of cross-presenting, CD103+dendritic cells (DCs) to the tumor; tumors lacking CCL4 expression exhibit a “cold tumor” phenotype and respond poorly to immunotherapy (Spranger and Gajewski, Nat. Rev. Cancer, 2018). Based on these results, we hypothesized that tumor-targeted CCL4 could enhance immune cell infiltration into the tumor and synergize with CPI therapy. We generated a fusion protein comprised of CCL4 and a collagen binding domain (CBD) derived from von Willebrand factor. Utilizing exposure of collagen in leaky tumor vasculature due to its disordered structure, we observed that that i.v. infusion of CBD-CCL4 fusion proteins, but not native CCL4, can enhance infiltration of CD103+DCs, CD8+T cells, and natural killer cells and slow B16F10 tumor growth when combined with CPI therapy consisting of anti-cytotoxic T-lymphocyte antigen 4 antibody (αCTLA4) + anti-programmed death-ligand 1 antibody (αPD-L1). Further analysis showed strong correlations between the presence of CD103+DCs and CD8+ T cells and tumor regression. Similarly, in the EMT6 breast cancer model, tumor-targeted CCL4 in combination with CPI, but not native form CCL4, enhanced recruitment of CD103+ DCs, CD8+ T cells, and led to a reduction in tumor growth. To confirm the importance of CD103+DCs in mediating anti-tumor responses, we utilized Batf3 knockout mice bearing B16F10 tumors; in this instance, anti-tumor efficacy of CPI + CBD-CCL4 was completely lost. Preliminary results also showed that CBD-CCL4 can synergize with αPD-1 antibody therapy, slowing tumor growth in CT26 and MC38 colon cancer models compared to αPD-1 therapy alone. Importantly, CBD-CCL4 treatment did not lead to any detectable levels of systemic cytokine elevation or serum liver damage markers, suggesting that this therapy was well-tolerated following systemic administration. These results highlight the utility of recruiting CD103+DCs to the tumor to improve the efficacy of CPI therapy. This engineered chemokine delivery strategy demonstrates significant translational potential by targeting the tumor stroma following systemic administration.
Citation Format: John-Michael Williford, Jun Ishihara, Ako Ishihara, Aslan Mansurov, Melody A. Swartz, Jeffrey A. Hubbell. Recruitment of CD103+DCs via tumor-targeted chemokine delivery enhances efficacy of checkpoint inhibitor immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2270.