It is known that both HIF-1α and HIF-2α induction activate OCT4, c-MYCc, SOX2 and enrich the expression of CD133- and CD44-positive cancer cells, along with the enhanced self-renewal functions and tumorigenic potential [4], while several studies proposed that cancer stemness is predominately controlled by HIF-2α [30, 62]. Here, CD44 is linked to cancer.