Abstract 2131: Paracrine cytokine pathways mediate metastasis of breast cancer to lymphatics

Abstract

Abstract Lymphatics, rather than blood vessels, are the primary route for breast cancer metastasis. The presence of breast cancer cells in regional lymphatics, i.e., lymphatic metastasis, is an important prognostic factor for patients. Delineating molecular mechanisms by which the breast cancer cells migrate toward and infiltrate into lymphatics is crucial to designing new therapies to prevent metastatic dissemination. To study tumor:lymphatic interactions, we are using a three-dimensional (3D) heterotypic co-culture model of human breast cancer cells (hBCCs) grown with human microvascular lymphatic endothelial cells (hLECs) in novel chambers that we designed and fabricated. These chambers support growth of the 3D co-cultures, live-cell confocal imaging in real time and noninvasive collection of conditioned media for secretomic analyses. We use live-cell assays developed in our laboratory for quantitative analysis of temporal and dynamic changes in BCC:LEC interactions in correspondence with changes in their malignant and proteolytic phenotypes. We cultured hLECs in the presence and absence of human MDA-MB-231 (231) triple-negative BCCs in 3D cultures for 4 days. In mono-cultures, the 231 cells grow in clusters that exhibit a stellate morphology and hLECs form branching networks with central nodes. We observed that the volumes of 3D structures formed by LECs and 231 cells were significantly greater in co-cultures than in mono-cultures of either cell type. In addition, 231 cells infiltrate into the LEC networks with the infiltration increasing over the 4-day period as assessed by the degree of overlap between 231 cells and hLECs in 3D reconstructions of the co-cultures. Moreover, soluble factors from LECs increase invasive outgrowths of 231 structures. This was demonstrated in 231 cells grown in media conditioned by LECs and in parallel co-cultures of 231 cells and LECs. The induction of invasiveness by LEC conditioned media is reduced by boiling and repeated freeze/thawing, suggesting that the active factor(s) is a protein. Our preliminary results suggest that LECs secrete soluble factors that may be therapeutic targets for reducing invasion of BCCs into lymphatic networks. Citation Format: Kyungmin Ji, Zhiguo Zhao, Kamiar Moin, Yong Xu, Robert J. Gillies, Raymond R. Mattingly, Bonnie F. Sloane. Paracrine cytokine pathways mediate metastasis of breast cancer to lymphatics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2131.