In vivo, tumor cells need to migrate towards blood vessels in order to metastasize. Streaming, a specialized mode of migration involving chemotactic signaling between macrophages and tumor cells, allows linear streams of tumor cells to migrate directionally towards blood vessels on collagen I-containing ECM fibers in vivo. We have successfully reconstructed tumor cell streaming in vitro by co-plating tumors cells, macrophages, and endothelial cells on 2.5 um micro-patterned substrates. We found that tumor cells and macrophages do not demonstrate directional migration in only one direction but random walk. Directional streaming migration of tumor cells in only one direction was established when beads coated with human umbilical vein endothelial cells (HUVEC) were placed at one end of the micro-patterned “collagen fibers” within the assay. Using this in vitro reconstituted streaming system, we found that directional streaming can be blocked by inhibiting multiple signaling pathways - notably the HGF/C-Met signaling pathway between endothelial cells and tumor cells and the EGF/CSF-1 paracrine loop between macrophages and tumor cells. These pathways were blocked using gefitinib (EGFRi), DCC-3014 (CSFRi), and altiratinib (DCC-2701)(c-Meti), which led to a marked decrease in endothelium directed streaming of the tumor cells. The inhibitors showed different efficacies of inhibition of streaming at different distances from the endothelium indicating that HGF from the endothelium organized the random walk of paired macrophages and tumor cells into a directional migration. Key observations made with the in vitro reconstituted system were reproduced in mammary tumors using the in vivo invasion assay. These results highlight a promising role for combinations of these inhibitors in blocking tumor cell streaming and metastasis in vivo and for use in human trials.

Citation Format: Edison Leung, Yarong Wang, Bryan Smith, Daniel Flynn, John Condeelis. Inhibiting endothelium directed tumor cell streaming by targeting the HGF/C-Met and EGF/CSF-1 signaling pathways. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5091. doi:10.1158/1538-7445.AM2015-5091