Abstract 2984: The chemokine CCL2/CCR2 signaling mediated fibroblasts-cancer cells crosstalk promotes basal like breast cancer progression

Cancer associated fibroblasts are the most abundant stromal cells in breast cancer, but their function in cancer progression has not been fully understood. We previously identified that the chemokine CCL2 was highly expressed in breast cancer associated fibroblasts, and high stromal CCl2 expression predicted poor outcome in basal like breast cancer. CCL2 is known to recruit monocyte/macrophage and promotes cancer progression. We previously found that recombinant CCL2 can directly signal to breast cancer cells and promote cell survival and invasion in vitro. In this study, we aimed to determine the functional importance of CCL2 signaling mediated fibroblast-cancer cell interactions in breast cancer progression. We used a fibroblast and cancer cell co-graft mouse model as the main functional assay. We generated primary fibroblasts from mouse mammary tumor and human breast cancer, and confirmed most of they expressed high level of CCL2. When co-grafted with the human basal breast cancer cell line MCF10A-CA1D into nude mice, fibroblasts enhanced xenograft growth. Stable knockdown of CCL2 expression from fibroblasts significantly reduced its ability in tumor growth promotion, while knockdown CCL2 from cancer cells did not. Decreased CCL2 production from fibroblasts resulted in increased apoptosis and autophagy in tumor samples. To determine the importance of direct CCL2 signaling to cancer cell, we generated the CCL2 receptor CCR2 mutant CA1D cancer cell lines by CRISPR-Cas9 targeting technology. Mutation of CCR2 in cancer cell significantly reduced tumor growth when co-grafted with CCL2 secreting fibroblasts. Lastly, we tested continuous delivery of CCL2 neutralizing antibody in the co-graft tumor model, but observed minimal therapeutic effect. Further examination of blood CCL2 level revealed an increased production of CCL2 from fibroblasts and mouse host after antibody treatment, which may contribute to the lack of therapeutic effect. In summary, our studies demonstrated the importance of CCL2/CCR2 signaling mediated fibroblasts-cancer cell interaction in basal like breast cancer progression. The CCL2 signaling pathway can be potentially served as therapeutic target, but requires development of efficient targeting strategy. Citation Format: Min Yao, Wei Bin Fang, Fang Fan, Nehemiah Alvarez, Patrick E. Fields, Nikki Cheng. The chemokine CCL2/CCR2 signaling mediated fibroblasts-cancer cells crosstalk promotes basal like breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2984. doi:10.1158/1538-7445.AM2017-2984