Expression of GATA3 in MDA-MB-231 Triple-negative Breast Cancer Cells Induces a Growth Inhibitory Response to TGFβ

Transforming growth factor (beta 1TGF beta 1) can promote proliferation in late stage cancers but acts as a tumor suppressor in normal epithelial cells and in early stage cancers. Although, the TGF beta pathway has been shown to play a key role in tumorigenesis and metastasis, only a limited number of models have been developed to understand this process. Here, we present a novel model system to discern this paradoxical role of TGF beta 1 using the MDA-MB-231 (MB-231) cell line. The MB-231 triple-negative breast cancer cell line has been extensively characterized and has been shown to continue to proliferate and undergo epithelial-to-mesenchymal transition (EMT) upon TGF beta 1 stimulation. We have previously shown by microarray analysis that expression of GATA3 in MB-231 cells results in reprogramming of these cells from a basal to a luminal subtype associated with a reduction of metastasis and tumorigenesis when implanted as xenografts. We now demonstrate that GATA3 overexpression in these cells results in a reduction of TGF beta 1 response, reversal of EMT, and most importantly, restoration of sensitivity to the inhibitory effects on proliferation of TGF beta 1. Microarray analysis revealed that TGF beta 1 treatment resulted in reduction of several cell cycle effectors in 231-GATA3 cells but not in control cells. Furthermore, our microarray analysis revealed a significant increase of BMP5 in 231-GATA3 cells. We demonstrate that combined treatment of MB-231 control cells with TGF beta 1 and BMP5 results in a significant reduction of cellular proliferation. Thus, this model offers a means to further investigate potentially novel mechanisms involved in the switch in response to TGF beta 1 from tumor promoter to tumor suppressor through the reprogramming of a triple-negative breast cancer cell line by the GATA3 transcription factor.