SOX9 and neoplasm: In contrast, we provided evidence that ZIP4 is not only functionally involved in CSC activities as measured by drug-resistance, spheroid and colony formation in vitro, and tumor formation in vivo, but also an upstream regulator of several known CSC markers, including ALDH1, OCT4 [14], SOX9 [14,15,16], and NOTCH3, making ZIP4 a more logical and potentially more effective target for HGSOC.