Establishment of a murine breast cancer cell line undergoing TGFβ-induced EMT.

<p>(<b>A</b>) Primary tumor cells were isolated from an advanced breast tumor of a MMTV-PyMT transgenic female mouse and were cultured for at least 2 months prior to further experimentation, resulting in a novel cell line termed Py2T. (<b>B</b>) Py2T cells maintain the MMTV-PyMT transgene. The MMTV-PyMT transgene was detected by PCR and agarose gel electrophoresis. DNA from an MMTV-PyMT tumor and from normal murine mammary gland (NMuMG) cells served as positive and negative controls, respectively. (<b>C</b>) Py2T cells lost the expression of the MMTV-PyMT transgene. Immunoblotting for the PyMT protein was performed on lysates of Py2T cells untreated or treated with 0.1 µM Dexamethasone for up to 72 h to induce the MMTV promoter. Lysates of an MMTV-PyMT tumor and NMuMG cells served as positive and negative controls, respectively. (<b>D</b>) Treatment of Py2T cells with known EMT inducers. Cells were continuously treated with the indicated growth factors and cytokines for 10 days (2 ng/mL TGFβ1; 50 ng/mL EGF; 10 ng/mL IGF-I; 50 ng/mL HGF; 20 ng/mL FGF-2; 20 ng/mL PDGF-BB; 50 ng/mL IL-6). Potential morphological changes were analyzed by phase-contrast microscopy. (<b>E</b>) Expression of epithelial (E-cadherin) and mesenchymal (N-cadherin, fibronectin) markers were analyzed by immunoblotting of the lysates of cells treated in (D). (<b>F</b>) Immunoblotting analysis of EMT marker expression in Py2T and Py2T LT cells. The mesenchymal subline Py2T LT (long-term) was generated by TGFβ-treatment of Py2T cells for at least 20 days, and was subsequently maintained in TGFβ containing growth medium. (<b>G</b>) Analysis of markers for EMT and breast cell type before and after TGFβ-induced EMT. Immunofluorescence staining was performed with antibodies against E-Cadherin (epithelial marker), vimentin (mesenchymal marker), estrogen receptor alpha (ERα), cytokeratin 8/18 (luminal markers) and cytokeratin 14 (basal marker). Scale bar, 20 µm.