Abstract 433: Expression of stem cell and EMT markers on circulating tumor cells

Abstract Tumor metastasis contributes significantly to cancer mortality especially in breast, colon, lung and prostate cancers and is believed to be associated with distant seeding of circulating tumor cells (CTC) present in the peripheral blood that arise from the primary tumor. Various studies on breast, colon and prostate cancer suggest that CTC numbers are good prognostic indicators. Although there are different technologies available to detect CTCs from peripheral blood, the CellSearchTM (Veridex, NJ, USA) technology is the only system approved by the US FDA for clinical utilization in metastatic breast, colorectal and prostate cancer. This system is based on a semiautomated immunomagnetic enrichment in combination with image cytometry and uses ferrofluid-conjugated antibodies for epithelial cell adhesion molecule (EpCAM), a cell surface antigen expressed on most normal epithelial cells and carcinomas to capture CTCs and cytokeratin (CK) 8, 18 & 19 to image. Additionally, by definition, CTCs are negative for CD45 (leukocyte common antigen). One major limitation of the CellSearchTM system is the sole dependence on anti-EpCAM antibody-based enrichment. Recent studies have demonstrated that epithelial cancer cells transition into mesenchymal-like tumor cells to gain migratory capacity, and therefore, CTC enumeration using the EpCAM-based system may be misleading due to the lower expression of this antigen. Based on this observation, we hypothesize that CTCs might express stem cell and EMT-associated markers, both hallmarks of the metastatic properties of these cells. To test this concept, we determined the expression of the stem/progenitor (Doublecortin like Kinase-I [DCLK-1]; CD133) and EMT (β-Catenin, Fibronectin and Vimentin) markers on a panel of lung cancer cells (A549: epithelial lung carcinoma, H358: bronchioalveolar carcinoma, H69: small cell lung cancer), colon cancer cells (SW480: colorectal adenocarcinoma, SW620: colorectal adenocarcinoma derived from metastatic lymph node) and tumor cells isolated from the ascites fluid of ovarian cancer patients. Tumor cells isolated from ascites fluids were also labeled with a DCLK-1 specific antibody and sorted using Fluorescence-activated cell sorting (FACS). Both DCLK-1 positive and negative cells from the cell sorting were stained by immunofluorescence and images were taken using inverted microscopy. Our data demonstrate that a small population of cells in the tumor cell lines and the tumor cells isolated from the ascites fluid of ovarian cancer patients have cancer stem cell properties. Furthermore, these cells also express stem/progenitor and EMT markers. These findings suggest that using these markers may be more sensitive and informative on patient prognosis than the use of EpCAM and cytokeratins for the detection and enumeration of circulating tumor cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 433. doi:1538-7445.AM2012-433