POU5F1 and cancer: The findings that overexpression of germ cell markers, such as, Oct4, SSEA1 (a germ cell marker in human), Nanog, Ifitm3, and c-Kit has been documented in numerous human cancers and some of these genes are shown to play important roles in tumorigenesis23–26 raise the possibility that the appearance of germ cell-like cells is common in human cancers.