Establishment and Characterization of an In Vitro Model of Ovarian Cancer Stem-like Cells with an Enhanced Proliferative Capacity.

The establishment of cancer stem-like cell (CSC) culture systems may be instrumental in devising strategies to fight refractory cancers. Inhibition of the Rho kinase ROCK has been shown to favorably affect CSC spheroid cultures. In this study, we show how ROCK inhibition in human serous ovarian cancer (SOC) cells can help establish a CSC system, which illuminates cancer pathophysiology and its treatment in this setting. In the presence of a ROCK kinase inhibitor, spheroid cultures of SOC cells expressed characteristic CSC markers including ALDH1A1, CD133, and SOX2, along with differentiation and tumorigenic capabilities in mouse xenograft models of human SOC. High expression levels of ALDH, but not CD133, correlated with spheroid formation CSC marker expression and tumor forming capability. In clinical specimens of SOC, high levels of ALDH1A1 correlated with advanced stage and poor prognosis. Pharmacologic or genetic blockade of ALDH blocked cell proliferation and reduced expression of SOX2, the genetic ablation of which abolished spheroid formation, whereas SOX2 overexpression inhibited ALDH1A1 expression and blocked spheroid proliferation. Taken together, our findings illustrated a new method to culture human ovarian CSC, and they defined a reciprocal regulatory relationship between ALDH1A1 and SOX2, which impacts ovarian CSC proliferation and malignant progression.