Abstract

Background: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.Methods:A sphere formation assay, cell proliferation, RT–PCR, western blot, FACS, immunohistochemistry and tumour xenograft were used to study the role of HIF2α.Results: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.Conclusions: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.

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