Abstract B010: The effects of tumor cell-secreted factors on endothelial cell junction phenotype

Abstract Triple negative breast cancer (TNBC) is subtype of breast cancer that has no expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). TNBC metastasizes to specific tissues such as brain and bone in a process termed organotropism. In this process, TNBC cells cross the vascular endothelium; transport across endothelial cells is, in part, regulated by cell-cell junctions. The TNBC cell secretome has been shown to contain factors such as vascular growth factor (VEGF) and matrix metalloproteinases (MMPs) that could play a role in altering endothelium permeability. Prior work by us has shown that VEGF in tumor conditioned media can alter endothelial cell junction phenotype in human brain microvascular endothelial cells. Given the various factors present in tumor conditioned media (TCM), we hypothesized that both VEGF and MMPs are present at distinct levels in conditioned media derived from brain- or bone-seeking TNBC cells and that these factors alter junction phenotype in human umbilical vein endothelial cells. We quantified levels of VEGF and MMPs 1 and 9 in tumor conditioned media from parental, brain-seeking, and bone-seeking MDA-MB-231 cells. Our results show that brain-seeking tumor cell conditioned media reduces VE-cadherin continuous junction coverage compared to conditioned media from parental or bone-seeking cells. VE-Cadherin junctions also have decreased junction widths in response to tumor conditioned treatment from brain-seeking MDAs. These results show that secreted factors from TNBC cells have a modest impact on endothelium junction integrity, and future work will quantify changes in endothelium permeability to test barrier function. This work will contribute to a further understanding of TNBC organotropic metastasis and more effective targeted therapeutics to prevent disease progression. Citation Format: Ariana Joy L. DeCastro, Lauren Griffith, Kimberly Stroka. The effects of tumor cell-secreted factors on endothelial cell junction phenotype [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B010.