Abstract A30: Ron kinase inhibition to improve immunotherapy for breast cancer metastasis

Metastasis is the cause of death for nearly all types of cancer, including breast cancer. An exciting new area of research in metastatic breast cancer centers on immune therapy. Although new immune checkpoint blockade therapies have provided benefit for a fraction of patients tested so far, the majority of patients still do not respond to these drugs. A better understanding of how the immune system can be harnessed against metastatic breast cancer is required in order to improve patient outcomes in this area. We previously discovered that macrophage Ron receptor tyrosine kinase promotes breast cancer metastasis by inhibiting CD8+ cytotoxic T lymphocyte activity. We hypothesized that dual blockade of Ron activity and existing immune checkpoint molecules would unleash a more effective CD8+ T cell response to control or eliminate metastatic breast cancer. Our strategy would simultaneously disable tumor-mediated immune evasion mechanisms on both the innate and adaptive immune systems. To test the potential of combination therapy, the Ron inhibitor BMS-777607 and/or the immune checkpoint blocking agents anti-PD1 or anti-CTLA4, were administered in our mouse mammary tumor model to examine the effects on breast tumor progression. To examine Ron-specific effects of BMS-777607, we also examined the effect of genetic deletion of host Ron signaling activity in combination with immunotherapy. The anti-tumor immune response was comprehensively examined by multi-color flow cytometry and immunohistochemical staining for tumor-infiltrating lymphocytes (TILs). Our data suggest that the combination of Ron inhibition with immune checkpoint blockade may be an effective therapy in breast cancer. Citation Format: Shu Chin Alicia Lai, Atakan Ekiz, Alana Welm. Ron kinase inhibition to improve immunotherapy for breast cancer metastasis [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A30.