POU5F1 and neoplasm: Gassenmaier et al. indicated that CXC chemokine receptor 4 (CXCR4)+ RCC cells presented CSC characteristics, such as increased resistance to TKIs, higher sphere-forming ability, and tumor growth-inducing potential in vivo, and expressed high levels of the stem cell-associated markers, OCT3/4, Nanog, and Sox2 [40].