Abstract PD15-02: Cx3cl1-cx3cr1 axis in liver metastasis of triple negative breast cancer

Abstract

Abstract Triple negative breast cancer (TNBC) is a breast cancer subtype with increased risk of distant metastasis, especially to visceral organs. However, the detailed molecular mechanism underlying the visceral metastasis of TNBC is unknown. We used three patient-derived xenograft models derived from TNBC tumors with different metastatic capacities. PDX1 and PDX2 model developed distant metastasis in only lung and liver, respectively. In contrast, PDX3 tumor metastasized to both lung and liver. RNA sequencing of the primary tumor and distant metastatic sites of these three PDX models was performed. The gene expression profiles of the primary tumors of the three models showed minimally overlapping genes. However, the microenvironment gene expression profiles, measured by using the sequencing reads aligned to mouse genome, showed distinct difference between the models. Among the differentially expressed genes, we identified Cx3cr1 as a significantly upregulated gene in the liver microenvironment of the PDX models that metastasized to liver. Next, we used 4T1 syngeneic mouse mammary carcinoma model to validate the Cx3cr1 in the mouse liver tissues. Interestingly, the Cx3cr1 up-regulation occurred during the pre-metastatic period, and Cx3cl1, the ligand of the Cx3cr1, was also up-regulated in the liver tissue prior to the development of metastasis suggesting the Cx3cr1 regulates the formation of pre-metastatic niche. Cx3cl1, the ligand of the Cx3cr1, was also up-regulated in the liver tissue prior to the development of metastasis. These data suggest that Cx3cl1 and Cx3cr1-mediated tumor-microenvironment interaction is critical in developing liver metastasis in TNBC. Cx3cl1 increased the invasion and migration of Raw264.7 monocyte/macrophage cells and this effect was abrogated by the Cx3cr1 silencing in Raw264.7 cells or treating Cx3cl1 neutralizing antibody. Pathway analysis of the RNA sequencing data showed that genes involved in extracellular matrix remodeling was significantly dysregulated in the liver tissues including Lysyl Oxidase (Lox). Cx3cl1 treatment in Raw264.7 cells resulted in increased expression of Lox and MMP9 mRNA in three-dimensional culture system. The Raw264.7 cells caused increased invasion of 4T1 cells in vitro. In conclusion, our data suggest that Cx3cl1-Cx3cr1 axis plays critical role during the liver metastasis of TNBC. Citation Format: Woohang Heo, Hye-Youn Son, Ju hee Kim, Kyu Jin Lee, Myeonghee Jeon, Songbin Li, Jeehee Jang, Dong-Young Noh, Wonsik Han, Hyeong-Gon Moon. Cx3cl1-cx3cr1 axis in liver metastasis of triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD15-02.