Abstract 63: Breast and colon cancer cells express L-selectin ligands that interact with L-selectin on white blood cells under flow conditions

Abstract

Abstract Evidence suggests circulating tumor cells (CTCs) can interact with white blood cells (WBCs) and promote metastasis under certain circumstances. However, the interaction between the L-selectin ligands expressed on CTCs and the L-selectin expressed on WBCs is less understood. We hypothesize that the L-selectin of WBCs will bind to the L-selectin ligands of cancer cells under hemodynamic flow conditions. BT-20, Hs-578T, MDA-MB-231 and SK-BR-3 breast cancer cells, and LS174T colon cancer cells were tested for expression of L-selectin ligands using L-selectin hFc (R&D Systems) in flow cytometry. Flow cytometry analysis revealed all five cancer cell lines expressed L-selectin ligands that were detected by L-selectin hFc. The L-selectin ligands on the surface of cancer cells were shown to be protease sensitive, as when the cells were treated with 0.1% bromelain (a broadly active protease), L-selectin hFc binding to all cancer lines was significantly reduced and exhibited binding levels similar to the negative isotype control (hIgG). The parallel plate flow chamber adhesion assay was used to examine the interaction between cancer cell lines (BT-20, Hs-578T, and LS174T) and WBCs isolated from normal healthy human donors in an IRB approved protocol. Two populations of WBCs, PMNs and PBMCs, were separated from whole blood and separately perfused at a wall shear stress of 0.7 dyn/cm2 over a cancer cell monolayer. Interacting cells, defined as PMNs or PBMCs tethered to or rolling on the monolayer, were visualized in real time using video microscopy. Both populations of WBCs interacted with BT-20, Hs-578T, and LS174T cells. Afterward, 5 mM EDTA was perfused across the monolayer, causing the release of WBCs consistent with Ca++ dependent binding. When the WBCs were incubated with an L-selectin antibody (anti-human CD62L, BD Pharmingen) for 30 minutes on ice before perfusion, total interactions were reduced compared to the negative isotype control (mIgG, BD Pharmingen) treated WBCs. These flow chamber results indicate that the L-selectin of PMNs and PBMCs specifically bind to the L-selectin ligands of the breast and colon cancer cell lines. Altogether, the five cell lines that were tested express L-selectin ligands that bind to L-selectin hFc. BT-20, Hs-578T, and LS174T cells interact with WBCs under flow conditions in an L-selectin and divalent cation dependent manner. Ultimately, elucidating the molecular mechanisms of adhesion between WBCs and cancer cells in vasculature may provide a rational basis for developing strategies against metastasis. Citation Format: Nicholas J. Cellars, Ariel L. Lanier, Monica M. Burdick. Breast and colon cancer cells express L-selectin ligands that interact with L-selectin on white blood cells under flow conditions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 63.