Abstract #5674: MCF-10A benign mammary epithelial cells enhance the malignant phenotype of MDA-231 breast cancer cells in vitro and in vivo
Authors: Joanna Poczobutt, John Tentler, Pepper Schedin, Arthur Gutierrez-Hartmann
Journal: Cancer Research (2009)

Interactions between cancer cells and their microenvironment play a critical role in cancer development. However, the influence of normal epithelial cells on the carcinogenesis process has not been extensively examined. The purpose of this study is to investigate the interactions between human normal mammary epithelial cells and breast cancer cells.  As a model of breast cancer cells we used MDA-231-T1AS, a subline selected for high tumorigenicity in mice. The MCF-10A cell line served as a model of normal mammary epithelial cells. MDA-231 cells and MCF-10A cells were transduced with red and green fluorescent proteins, respectively, to serve as markers. We examined the interaction between the 2 cell lines  in vitro  using soft agar colony formation assay and  in vivo , using the nude mouse xenograft assay.   In the soft agar assay we set up mixed, normal-only and cancer-only cultures. We found that the number of colonies formed in the mixed culture was increased 4.6 fold in comparison to cancer-only. Using fluorescent microscopy, we determined that the colonies in the mixed culture were composed exclusively of cancer cells. Further experiments showed that medium conditioned by MCF-10A cells also increased the number of soft agar colonies formed by MDA-231 cells. Similar result was obtained with the MCF-12A non-transformed mammary epithelial cells. In the nude mouse tumorigenicity assay, we injected 1x10 6  of MDA-231 cells mixed with 4x10 6  of MCF-10A cells into mammary fat pads of nude mice (mixed tumors). As controls, we injected 1x10 6  of MDA-231 cells (cancer-only), and 4x10 6  of MCF-10A cells (normal-only). We determined that MCF-10A cells significantly accelerated the growth of tumors formed by MDA-231 breast cancer cells, although the normal cells did not contribute to the tumor mass. Proliferation rates in tumors harvested at days 7 and 14 post-inoculation were not different between mixed and cancer-only groups. To determine whether the normal cells actively secrete factors that enhance the tumorigenic growth of cancer cells we mixed cancer cells with paraformaldehyde-fixed normal cells. We observed that the growth of the tumors was equally enhanced by fixed cells.  The results of soft agar assay indicated that MCF-10A cells provided factors that enhanced the survival and proliferation of MDA-231 cells. In the nude mouse assay, MCF-10A cells dramatically enhanced the growth of MDA-231 breast cancer cells. Similar effect was elicited by paraformaldehyde-fixed MCF-10A cells, suggesting that in this assay the normal cells need not be alive to enhance the tumorigenic growth of breast cancer cells. In conclusion, these studies show that the mechanism by which normal epithelial cells enhance the transformed phenotype of breast cancer cells is via secreted factors and cell-cell contact.   Citation Information:  In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 5674.