Ovarian cancer cells with the CD117 phenotype are highly tumorigenic and are related to chemotherapy outcome

Cancer stem cells (CSCs) play an important role in the recurrence and drug resistance of cancer. Isolation and characterization of CSCs from ovarian cancer samples may help to provide novel diagnostic and therapeutic targets in the management of recurrent disease and drug resistance in ovarian cancer. Here, we developed a xenograft model in which cells from 14 samples of human ovarian serous adenocarcinoma tissue or ascites were implanted in immunodeficient mice to test the tumorigenic potential of different populations of ovarian cancer cells. We identified and isolated the tumorigenic cells as CD117⁺Lineage⁻ from three different xenografts. As few as 10³ cells with the CD117⁺Lineage⁻ phenotype, which comprise < 2% of the xenograft tumor cells, were able to regenerate tumors in a mouse model, a 100-fold increase in tumorigenic potential compared to CD117⁻Lineage⁻ cells. The tumors that arose from purified CD117⁺Lineage⁻ cells reproduced the original tumor heterogeneity and could be serially generated, demonstrating the ability to self-renew and to differentiate, two defining properties of stem cells. Furthermore, immunohistochemistry analysis of 25 patients with advanced ovarian serous adenocarcinoma revealed positive immunostaining for CD117 in 40% (10 of 25) of patients. CD117 expression was statistically correlated with resistance to conventional chemotherapy (P = 0.027). In conclusion, our study demonstrates that human ovarian cancer cells with the CD117⁺ phenotype possess the unique properties of CSCs, including self-renewal, differentiation, a high tumorigenic potential, and chemoresistance. Future studies designed to target CD117⁺ cancer cells may identify more attractive and effective therapies for treatment of ovarian cancer.