HIF2α is involved in the expansion of CXCR4-positive cancer stem-like cells in renal cell carcinoma.

Hypoxia and the subsequent activation of hypoxia-inducible factor-2α (HIF2α) contribute to the progression of a variety of cancers. However, their role in the generation of renal cell carcinoma-derived stem cells has not been fully addressed. A sphere formation assay, cell proliferation, RT-PCR, western blot, FACS, immunohistochemistry and tumour xenograft were used to study the role of HIF2α. Propagation of four renal cell carcinoma (RCC) cell lines (Caki-1, Caki-2, 786-O, 769-P) in anchorage-independent floating spheres led to the expansion of cells bearing the CXCR4 (CD184) surface marker. Inhibition of the CXCR4 pathway reduced sphere expansion. The enhanced self-renewal activity of the CXCR4-positive spheres was preceded by the upregulation of HIF2α. Knockdown of HIF2α abrogated CXCR4 expression and sphere formation. Finally, RCC-derived spheres showed an undifferentiated phenotype in vivo and formed subcutaneous tumours that highly expressed HIF2α and CXCR4. Inhibition of HIF2α abolished tumour growth in animal models. These results suggest that the generation of RCC-derived CSCs involves the activation of HIF2α and may provide a foundation for the development of new strategies to prevent the induction of CSCs in RCC.