Abstract 3338: Capacity of breast cancer cell homing to distant organs is altered by acquisition of stem cell properties
Authors: Shirure Venktesh S. , Henson Karissa A. , Burdick Monica M. 
Published: June 2012

It is hypothesized that migration of tumor cells to distant organs is mediated by E-selectin expressed on vascular endothelium of a secondary tissue and its counter receptors expressed on circulating breast tumor cells. Previously, our group has characterized glycosphingolipids and CD44 as E-selectin binding molecules expressed on BT-20 and MDA-MB-468 breast cancer cell lines. We now report that the ZR-75-1 breast cancer cell line possesses E-selectin ligand activity, yet does not express any of the known E-selectin ligands found on colon cancer cells, leukocyte, or BT-20 and MDA-MB-468 breast cancer cells. A systematic investigation to identify novel E-selectin ligands expressed by ZR-75-1 cells was performed. Molecules isolated from whole cell lysate by immunoprecipitation with mouse E-selectin/ human Fc chimera (E-Ig chimera) were analyzed by mass spectrometry, which revealed that a glycoprotein known as Mac-2 binding protein (Mac-2bp) is an E-selectin ligand. Immunoprecipitation of Mac-2bp from whole cell lysate by using anti-Mac-2bp antibody followed by western blotting with E-Ig chimera and HECA-452 antibody demonstrated that Mac-2bp is a sialofucosylated E-selectin ligand. Dual staining of ZR-75-1 cells with anti-Mac-2bp antibody and E-Ig chimera imaged by fluorescence microscopy showed that Mac-2bp is a cell surface glycoprotein that is co-localized with E-selectin binding epitopes. Collectively, these results demonstrated that Mac-2bp is a novel E-selectin ligand expressed by ZR-75-1 breast cancer cells.

In addition to the three breast cancer cell lines above, we tested four other breast cancer cell lines for their E-selectin ligand activity. Among the panel of cell lines examined, MDA-MB-231 and Hs-578t cells showed very weak activity for E-selectin binding as compared to the other five cell lines. Surprisingly, these were the only cells among all tested that were characterized by the CD44+/CD24-/low phenotype (&gt;80% of cells). Staining with E-Ig chimera with subsequent detection by flow cytometry revealed differential E-selectin ligand activities of cancer stem versus non-stem cell phenotypes. Further, BT-20 cells (predominantly CD44+/CD24+) were treated with the metastatic niche factor TGF-β to force EMT and transformation into cancer stem cells, and change(s) in E-selectin ligand expression and function were assessed. Based on these results, we propose a new paradigm for the metastasis cascade, whereby breast cancer cells home to distant organs via an E-selectin-mediated pathway followed by transformation into breast cancer stem cells using metastatic niche factors. This model is consistent with the notion that cancer cell plasticity might have a significant role in metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3338. doi:10.1158/1538-7445.AM2011-3338