We assessed expression of aldehyde dehydrogenase (ALDH), CD133, and CD44 as markers of CTCs with a tumor-initiating cell (TIC) phenotype in patients with PDAC and the relationship of this expression to patient outcomes.<b>Experimental Design:</b> Peripheral blood from 60 consecutive patients with PDAC undergoing surgical resection was obtained and processed using the Isolation by Size of Epithelial Tumor (ISET) method.
Furthermore, the TIC phenotype can change in xenografts: primary tumors in which all TICs are CD133(+) can give rise to xenografts that contain substantial numbers of CD133(-) TICs.