The requirement for freshly isolated human tumor cells for the study of colorectal cancer stem cells.

411 Background: Reliable methods for the isolation of an enriched cancer stem cell (CSC) population in colorectal cancer (CRC) may provide new approaches for the identification of therapeutic targets. There is no consensus regarding the best methods to isolate a CRC tumor cell population enriched for CSCs. The goal of this study was to determine the utility of various CSC markers in both established cell lines and freshly isolated patient-derived tumor xenografts in order to validate methods of CSC isolation. Methods: Established human CRC cell lines (HCT116, HT29, SW480) and three freshly isolated CRC cell lines were studied. Freshly isolated cell lines were generated by first injecting CRC cells derived from clinical specimens into nude mice. Xenografted tumors were resected and FAC-sorted to isolate human cells. These cells were FAC-sorted for CD133, CD44, and ALDH activity. Tumorsphere formation and in vivo dilutional and serial tumorigenicity studies were done to validate methods for CSC enrichment. ...