Abstract 4319: Inability of putative ovarian cancer stem cells to engage OXPHOS confer 2-deoxyglucose-mediated prevention of in vivo recurrence
Authors: Alvero Ayesha B. , Montagna Michele , Sumi Natalia J. , Joo Won Duk , Craveiro Vinicius , Graham Emma , Mor Gil 
Published: May 2015

Background:

Mortality in ovarian cancer does not usually occur at primary diagnosis but rather in the recurrent setting where patients present with chemoresistance and carcinomatosis. Prevention of recurrence can therefore have an impact on patient survival. Due to its inherent chemoresistance, cancer stem cells that are left after surgery are thought to drive recurrent disease owing to its tumor-initiating properties and enhanced capacity for repair. We demonstrate that the putative epithelial ovarian cancer (EOC) stem cells have a unique bioenergetic profile that can be targeted with the goal of delaying and/or preventing recurrent disease.

Methods:

In vitro: Pure clones of CD44+/MyD88+ and CD44-/MyD88- EOC cells were treated with 20 mM 2-DG, 5 μM Oligomycin, or 1 mM dinitrophenol (DNP). ATP levels were quantified using Celltiter Glo. Mitochondrial content and membrane potential (MMP) were measured using Mitotracker Green and Red, respectively. In vivo: CD44+/MyD88+/mCherry+ EOC stem cells were injected i.p. in nude mice. Mice received four doses of 12 mg/kg Paclitaxel q3d and then randomized to maintenance with 2-DG (500 mg/kg every MWF) or maintenance with saline. All treatments were given i.p. Tumors were monitored by live in vivo imaging using In Vivo FX System and quantified using the region of interest (ROI) tool based on mCherry fluorescent area.

Results:

Treatment with Oligomycin or DNP did not affect viability nor ATP content in CD44+/MyD88+ EOC stem cells but 2-DG induced rapid decline in ATP and death, which was not rescued with Succinate co-treatment. In contrast, in CD44-/MyD88- EOC cells, treatment with Oligomycin, DNP, or 2-DG only slightly decreased ATP without inducing cell death. Despite having more mitochondria, EOC stem cells have: (1) lower levels of Cox- I, -II, and -IV; (2) undetectable levels of pyruvate dehydrogenase; (3) and higher levels of UCP2 compared to CD44-/MyD88- EOC cells. Administration of 2-DG, as maintenance treatment post-chemotherapy, significantly delayed progression of recurrent disease and decreased i.p. tumor burden in the xenograft model. All mice maintained in saline recurred with average time-to-recurrence of 11 days. In contrast, only 25% of the mice maintained in 2-DG demonstrated recurrence with average time-to-recurrence of 19 days. Finally, analysis of tumors post-mortem show high levels of the autophagic markers p-AMPK and cleaved LC3 in the 2-DG maintained group compared to control.

Conclusion:

We demonstrate that the exclusive reliance of EOC stem cells to glycolysis to meet its ATP requirement and its inability to engage OXPHOS even under stress conditions can be exploited to target these otherwise chemoresistant cancer cells for the prevention of recurrence. Our results show the potential of maintenance treatment with glycolysis inhibitors, administered following standard chemotherapy, in improving survival in patients with ovarian cancer.

Citation Format: Ayesha B. Alvero, Michele Montagna, Natalia J. Sumi, Won Duk Joo, Vinicius Craveiro, Emma Graham, Gil Mor. Inability of putative ovarian cancer stem cells to engage OXPHOS confer 2-deoxyglucose-mediated prevention of in vivo recurrence. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4319. doi:10.1158/1538-7445.AM2014-4319