CD44 and prostate cancer: Specifically, CD44, α2 integrin, β1 integrin, and CD49f (α6 integrin) are the most commonly recognized prostate cancer stem cell markers, while EphA2 controls prostate cancer stem cell-like functions such as clonogenic potential, self-renewal, prostasphere formation, tumor onset, and dissemination of prostate carcinoma to the bone [18–27], and syndecan-1 (CD138) stabilizes prostate cancer tumor-initiating cells [36].