Identification and functional characterization of the cancer-initiating cell population in human ovarian clear cell carcinoma (occc) lines
Blane Gebreyes5, Bart Kolendowski1,3, Vasu Bhat2,3, Yudith R. Valdes1,3, Trevor G. Shepherd1,3,4,6,7, Gabriel E. DiMattia1,3,5,7.
1The Mary & John Knight Translational Ovarian Cancer Research Unit, Verspeeten Family Cancer Centre, London, ON, Canada; 2Translational Breast Cancer Research Unit, Verspeeten Family Cancer Centre, London, ON, Canada; 3Lawson Health Research Institute, London Health Sciences Center, London, ON, Canada; 4Anatomy and Cell Biology, Western University, London, ON, Canada; 5Biochemistry, Western University, London, ON, Canada; 6Obstetrics & Gynaecology, Western University, London, ON, Canada; 7Oncology, Western University, London, ON, Canada
Introduction: OCCC is a rare histotype of epithelial ovarian cancer with poor late-stage prognosis. One determinant of OCCC mortality is the extent of regional and distant metastases within the peritoneal cavity. Metastasis is responsible for 90% of cancer deaths and can be attributed to a small subpopulation of highly tumorigenic cells with a capacity for self-renewal, known as cancer stem cells (CSCs). Despite making up only 0.01-2% of the average tumour mass, these cells play a crucial role in treatment resistance, disease spread, and recurrence.
Methods: RT-qPCR, Western blotting, and FLOW cytometry will be employed to establish a baseline expression profile for well-characterized CSC markers. Select lines will undergo CSC enrichment through the development of drug-resistant (carboplatin, paclitaxel, AZD-8055) lines or through specialized culture conditions meant to sustain only CSCs. Changes in the expression of well-characterized CSC markers in enriched cell lines will be investigated relative to the parental cell line and will be functionally characterized via in vivo xenotransplantation.
Results: The expression of different stem cell markers (NANOG, SOX2, c-MYC, KLF4) did not correlate with the expression of aldehyde dehydrogenase (ALDH) 1A1, nor the activity of ALDH family members, in human OCCC cell lines. The ability to proliferate in suspension culture in standard media did not predict cell line viability in suspension culture using CSC-enriching media. KOC-7c, JHOC-5, ES2, and RMG-I lines were viable in both conditions, however, OVTOKO and TOV-21G were only able to grow in standard media.
Conclusions: This is the first time human OCCC cell lines have been enriched with CSCs for identification and functional characterization. These results may provide a platform for future studies aimed at understanding how various epigenetic features define OCCC CSCs to potentially identify existing epigenome-targeted therapies which may selectively kill CSCs.
Mary and John Knight Memorial Gift . London Run for Ovarian Cancer. Wolfe Senior Fellowship. Canadian Institutes of Health Research.