Cisplatin To Induce Cancer Stem Cell State In Ovarian Cancer.

e17098 Background: Ovarian cancer (OC) is the most lethal gynecological cancer. Despite high rates of response to initial cytoreductive surgery and taxane-platinum combination therapy, vast majority of patients recur. OC is marked by a high degree of cellular heterogeneity and contains a cancer stem cell (CSC) population that contributes to tumor growth, recurrence, and treatment resistance. Methods: We used isogenic OC cell lines A2780/CP70 (cisplatin naïve/resistant). A lentiviral construct, which contained GFP attached to the promoter region of the CSC transcription factor NANOG, was used to transduce them. Stably transduced cells were sorted based on their GFP intensity. Tumorsphere formation assays and tumor initiation experiments were performed to assess self-renewal. Sorted cells were cultured, treated with cisplatin, and counted for 5 days. Time-lapse imaging was performed to monitor GFP expression. Results: A2780 GFP+ cells expressed higher levels of CSC markers including CD44 and CD133. These cells had higher levels of NANOG and OCT4. Moreover, CP70 cells displayed higher NANOG and OCT4 expression as compared with A2780 cells. A2780 GFP+ cells were significantly more self-renewing than their GFP- counterparts. In addition, CP70 cells possessed higher self-renewal as compared to A2780. The gold standard functional CSC assay is tumor initiation and upon sorting and injection into NSG mice, all mice injected with GFP+ cells developed tumors whereas in mice injected with 50K and 5K GFP- cells, 4/5 and 3/5 developed tumors, respectively (CSC frequencies were 1:1; CI = 1:6,271-1:1, and 1:17,979; CI = 1:49,395-1:6,544 in GFP+ vs GFP- cells, respectively). Moreover, we compared cisplatin sensitivity between cultured GFP+ and GFP- A2780 cells, and found a significant survival advantage in GFP+ over GFP- cells. Upon cisplatin treatment, surviving GFP- cells showed higher GFP intensity and NANOG mRNA expression as compared to untreated cells. This was confirmed by visual induction of GFP using time-lapse microscopy. Conclusions: Cisplatin may serve as an inductive pressure for the stem cell state and enrich CSCs. Applying this knowledge to current OC treatment paradigms, partnering cytotoxic chemotherapy with a CSC targeted therapy, is paramount.