Abstract 1553: Redefining CTCs: Detection of cytokeratin-negative circulating tumor cells (CTCs)

Introduction: There is growing evidence that CTCs display an epithelial-mesenchymal transition phenotype. Current enrichment techniques rely upon epithelial markers for capture (anti-EpCAM antibodies and cytokeratin [CK]) and may miss important populations of circulating tumor cells. We sought to develop a new method for identification of CTCs. Methods: After IRB approval, blood from patients with ovarian or colorectal carcinoma was collected. Cell Enrichment and Extraction (CEE) technology, a microfluidic-based device using an antibody cocktail targeting epithelial and mesenchymal markers, was utilized for the capture and analysis of rare cells in blood. We enumerated cells that were CK+ and/or contained complex aneuploidy by fluorescent in situ hybridization (FISH). Blood samples from healthy volunteers served as a negative control. Fresh frozen tumor samples were analyzed on a subset of patients to search for concordance of molecular alterations with CTCs. An orthotopic ovarian cancer model was used to evaluate effects of chemotherapy on CTCs. Results: Enumeration of CK+ cells identified an average of 1 and 2 cells per 10 mL blood in ovarian and colorectal cancer patients, independent of stage or tumor grade. Enumeration did not correlate with serum tumor marker levels. The majority of CK+ cells had complex aneuploidy. Ovarian cancer patients had equal numbers of CK- and CK+ complex aneuploid cells (p=1.0). A three-fold increase in CK- over CK+ complex aneuploid cells was noted in patients with colorectal cancer, although not statistically significant (p