Clinical relevance of cytokeratin-negative circulating tumor cells.

Abstract

e21101 Background: Current enrichment techniques rely upon epithelial markers for capture of circulating tumor cells (CTCs). We developed a new method of isolating CTCs that lack EpCAM and/or cytokeratin (CK) expression; presumably cells that have undergone epithelial-to-mesenchymal transition (EMT). We sought to assess if such CTCs have clinical significance. Methods: After IRB approval, blood from ovarian or colorectal carcinoma patients was collected. A microfluidic-based (CEE) platform and antibody cocktail targeting epithelial and mesenchymal markers was utilized for capture and analysis of CTCs. Cells that were CK+/CD45- and CK-/CD45- were enumerated then examined for aneuploid status by fluorescent in situ hybridization (FISH) to further classify each cell as either normal or aneuploid (≥2 abnormalities by FISH). Results were then correlated with clinical outcome. Results: Total numbers of normal and aneuploid CK+ cells were significantly higher than either CK+ or CK- aneuploid cells for ovarian (p<0.09) and colorectal (CK+ aneuploid, p<0.01; CK- aneuploid, p<0.05) cancers. Overall, numbers of CK+ and CK- aneuploid cells were not significantly different (ovarian p=1.0, colorectal p=0.34). For ovarian cancer patients, presence of CK- aneuploid cells correlated with four-fold shorter progression free survival (PFS) (8 months with v. 33 months without detection; p<0.04). No significant difference in PFS was seen when CK+ aneuploid cells were detected (41 months with v. 25 months without detection; p<0.49). Preliminary results further suggest that detection of CK- aneuploid cells is associated with suboptimal tumor debulking. Conclusions: Enumeration of total CK+ cells was found to be higher than CK- cell populations in both cancer types. However, only CK- aneuploid cells were significantly associated with clinical outcome. These data suggest post-EMT (CK-) CTCs occur with lower frequency than classically defined CK+ CTCs, however they may carry more clinical relevance.