Since CD44 has been indicated as a putative surface marker for cancer stem/progenitor cells in breast and ovarian cancers [23,26,27,49], and since its expression was significantly up-regulated in the OVCAR-3 and ES2 cell lines under hypoxia, we decided to further analyze whether CD44 expression was associated with any stem-like property in these cells. The gene discussed is CD44; the disease is ovarian carcinoma.