POU5F1 and neoplasm: Then, we assessed the effect of POSTN and PTK7 on the CSC-like phenotype of tumor cells and the RT-PCR analysis showed that PTK7 knockdown impaired the expression of the CSC markers CD166, SALL4, CD271, CD90, CD133, OCT-4, ALDH, SOX2, and NANOG in the HN6 and SCC-25 cells.