Abstract 1920: Stem-like triple negative breast cancer cells exhibit a distinct response to selectin/selectin ligand interactions

Circulating tumor cells (CTCs) often over-express sialofucosylated glycans, which bind to E-selectin presented on vascular endothelial cells. This interaction facilitates the initial tethering and rolling adhesion events in CTC extravasation during cancer metastasis. Though selectins and their ligands are well-established cell adhesion molecules, relatively little is known about their roles as cell signaling molecules for regulating growth, migration, and apoptosis in breast cancer (BC). To investigate the effects of selectin/selectin ligand interactions on BC cell signaling and adhesion, Hs578T, and MDA-MB-231 stem-like triple negative cell lines and BT-20, MCF-7, and ZR-75-1 non-stem-like hormone-receptor-positive cell lines were grown on tissue culture plates pre-treated with recombinant E-selectin or perfused over E-selectin-presenting substrate at physiologically relevant laminar flow conditions. In culture, cell lines demonstrated a dose dependent response on substrates pre-treated with increasing concentrations (1-10 µg/ml) of recombinant E-selectin. More specifically, cell lines exhibited little change on substrate treated with low concentrations of recombinant E-selectin (1-5 µg/ml) relative to human Fc fragment and fibronectin controls, yet displayed varying degrees of membrane blebbing and, in some cases, aggregate formation and reduced proliferation on substrate treated with 10 µg/ml of recombinant E-selectin. Notably, the stem-like triple negative cell lines, specifically Hs578T cells, had the most pronounced response to culture on E-selectin substrate as defined by blebbing and formation of cell aggregates. Furthermore, when Hs578T cells were cultured on substrate with adjacent areas treated with either recombinant E-selectin (10 µg/ml) or fibronectin (molar equivalent), cells failed to attach and grow on E-selectin but successfully seeded and proliferated in culture on fibronectin. In the laminar flow assay, Hs578T and MDA-MB-231 stem-like triple negative cell lines had four fold fewer adhesions on E-selectin substrate relative to the adhesion of BT-20, MCF-7, and ZR-75-1 non-stem-like hormone-receptor-positive cell lines. Moreover, the average rolling velocity of the stem-like triple negative cell lines on E-selectin substrate was significantly greater than the average rolling velocities of the other cell lines, which illustrates that under dynamic flow conditions stem-like triple negative BC cell lines have relatively fewer and weaker interactions with E-selectin. These data show that BC cells, especially Hs578T stem-like triple negative BC cells, differ in response to selectin/selectin ligand interaction under static and dynamic conditions, and illustrate that threshold levels of selectin/selectin ligand interaction may regulate cell signaling in certain types of BC cell lines. Thus targeting these interactions may lead to novel BC therapeutics. Citation Format: Grady E. Carlson, Luis F. Delgadillo, Emily A. Blaha, Fabian Benencia, Monica M. Burdick. Stem-like triple negative breast cancer cells exhibit a distinct response to selectin/selectin ligand interactions. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1920. doi:10.1158/1538-7445.AM2014-1920