Collaborative interactions between malignant cancer cells and their surrounding nonmalignant stromal cells are increasingly recognized as crucial factors in tumor biology. In adenocarcinomas such as serous ovarian cancer, stromal cells in the microenvironment are recruited either locally from neighboring tissues or distantly from the circulation and bone marrow. To study the effects of bone marrow-derived stromal cells on ovarian cancer, two bone marrow preadipocyte stromal cell lines, MS5 and OP9, were used in coculture with ovarian cancer cell lines. Large number of adipocytes was observed in coculture of ovarian cancer cells with stromal cells when compared to stromal cells cultured alone. To quantify the extent of adipogenesis induced by ovarian cancer cells, MS5 or OP9 was cocultured with three ovarian cancer cell lines OVCAR3, OVCAR5 and SKOV3 by using 0.4 μm transwell permeable support and stained for oil red O after 7 days. OVCAR5 coculture resulted in highest increase in the amount of oil red O stain of 2.5±0.6-fold in MS5 and 2.6±0.8-fold in OP9 compared to MS5 or OP9 alone. Recently, it was reported that adipocytes promote ovarian cancer growth by providing energy to cancer cells (Nieman et al. Nature Medicine, 2011). In support of this observation, we found that coculture of MS5 yielded a 1.9±0.1-fold increase in number of OVCAR5 cells. After coculturing with MS5 or OP9 stromal cells for 7 days, OVCAR5 cells were harvested from the transwell permeable support to allow colonies to form in low melting point agarose for 28 days to determine the number of cancer stem/progenitor cells. OVCAR5 cultured alone has a colony formation efficiency of 2.64%. OVCAR5 that was cocultured with MS5 or OP9 has a higher percentage of colonies of 6.52% and 9.2% respectively. A panel of 17 cytokines/growth factors was analyzed by RT-PCR to determine the putative factors secreted by OVCAR5 that promotes adipogenesis. BMP4 and IL8 were found to be highly expressed in OVCAR5 when compared to SKOV3, which only mildly increased adipocyte number. shRNAs against BMP4 and IL8 were used to silence the respective cytokines in OVCAR5 by lentiviral vectors. Coculture of shBMP4 or shIL8 OVCAR5 cells with MS5 in transwell filter each resulted in a 15 and 24% decrease in oil red O stain, confirming the enhanced adipogenesis was partly conferred by BMP4 and IL8 secreted by OVCAR5. Our results illustrate how ovarian tumor cells modulate the host environment by stimulating differentiation of adipocytes from their precursor cells from the bone marrow mesenchymal stem cells, which in turn favor the proliferation and increase the number of ovarian cancer stem cells. This study strengthens the importance of tumor microenvironment in providing a tumor stem cell niche and proposes possible targets for cancer therapy that counteracts the differentiation of adipocytes caused by ovarian cancer cells.

Citation Format: Elissa Wai Pung Wong, Lingbo Shen, Jae-Hung Shieh, Malcolm A. S. Moore. Enhanced adipogenesis of bone marrow-derived stromal cells by ovarian cancer cells via BMP4 and IL8 is associated with increase in cancer stem/progenitor cells and cancer cell proliferation. [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 4866. doi:10.1158/1538-7445.AM2014-4866