Abstract 5894: Stromal fibroblasts from metastatic breast cancer promote proliferation and migration of breast cancer cell and regulate its stemness
Authors: Gui Yirui , Aguilar-Mahecha Adriana , Buchanan Marguerite , Basik Mark 
Published: July 2017

Breast cancer is one of the most common causes of cancer-related death in women in the world. Although most research is focused on the tumor cells, it is important to elucidate the molecular nature of the tumor-stromal relationship to truly understand the biology of breast tumor growth. Cancer-associated fibroblasts (CAFs) are the major cellular constituents in the tumor microenvironment. CAFs are in direct contact with the adjacent cancer cells and crosstalk with them through soluble cytokines, growth factors and exosomes during carcinogenesis in human breast cancer. To determine for the first time the function of CAFs in metastatic sites of breast cancer, we collected CAFs from human patients of metastatic sites (m-CAFs) and compared them with CAFs from primary tumor (p-CAFs) and normal fibroblasts (NFs). We found that m-CAFs expressed higher levels of α-smooth muscle actin (SMA) compared with p-CAFs and NFs. The proliferation of MDA-MB-436 breast cancer cells was significantly increased by treatment with conditioned medium (CM) from m-CAFs compared with p-CAFs in vitro. Also, CM by m-CAFs induced paclitaxel resistance in MDA-MB-436 cells, suggesting that soluble factors produced by m-CAFs promote chemo-resistance, to a greater extent than CM from p-CAFs. The migration and invasion ability of MDA-MB-436 cells co-cultured with m-CAFs CM was significantly greater than that of the p-CAFs CM. m-CAFs outperformed the p-CAFs and NFs in terms of their ability to promote sphere-forming activity in a 3D in vitro culture model. Furthermore, m-CAFs protected MDA-MB-436 cells from the cytotoxic effects of doxorubicin more than p-CAFs in this spheroid 3-D culture. When MDA-MB-436 cells were sorted from these spheroids and grew in the respective CMs, they showed higher expression of the stemness markers of CD44+CD24- compared with cells obtained from p-CAFs/MDA-MB-436 spheroids. Also these cells from the co-culture with m-CAFs experienced with the cadherin switch. Nanog has been demonstrated to promote chemoresistant and epithelial-mesenchymal transition (EMT). The results displayed that MDA-MB-436 cells incubated with the CM from the m-CAFs had a higher expression of Nanog compared with that of p-CAFs. RNA-seq results showed that IGF2 is one of the most different genes between m-CAFs and p-CAFs, its expression was more significant in m-CAFs co-cultured with MDA-MB-436 cells than p-CAFs. The signaling pathway in MDA-MB-436 cells were comparable between co-cultured with m-CAFs CM and the IGF2 stimulation at 2 hours. All these data illustrates that fibroblasts isolated from metastatic site differed in terms of their ability to promote breast cancer cells progression compared to p-CAFs. Our data suggests that m-CAFs are more potent than p-CAFs in inducing the proliferation, migration, drug resistance and cancer stemness of breast cancer cells in an in vitro model.

Citation Format: Yirui Gui, Adriana Aguilar-Mahecha, Marguerite Buchanan, Mark Basik. Stromal fibroblasts from metastatic breast cancer promote proliferation and migration of breast cancer cell and regulate its stemness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5894. doi:10.1158/1538-7445.AM2017-5894