Abstract
An epithelial-mesenchymal transition (EMT) has been implicated in cancer metastasis, drug resistance, and in conferring stem cell-like traits to cancer cells. Most studies investigating EMT in cancer have either utilized immortalized or cancer cell lines that are already primed to undergo an EMT and do not adequately represent a fully differentiated epithelial state in the absence of an EMT induction. Hence, model systems are required which recapitulate all stages of EMT in cancer cells. Here, we report the derivation and characterization of epithelial PyMT-1099 cancer cells from the MMTV-PyMT mouse model of breast cancer. We demonstrate that PyMT-1099 cells undergo an EMT upon TGFβ treatment, while upon TGFβ withdrawal they go through a mesenchymal-epithelial transition (MET), as assessed by changes in cell morphology and marker expression and comparable to normal murine mammary gland NMuMG cells. However, in contrast to NMuMG cells, PyMT-1099 cells show an increase in cell migration and are highly tumorigenic and metastatic when transplanted into immunocompromised mice. Finally, we report cancer cell-specific changes in gene expression during EMT of PyMT-1099 cells not found in non-transformed NMuMG cells. Thus, PyMT-1099 cells are a versatile tool to study breast cancer-associated EMT and MET in vitro and in vivo.
Highlights
An epithelial-mesenchymal transition (EMT) has been implicated in cancer metastasis, drug resistance, and in conferring stem cell-like traits to cancer cells
To derive a cancer-specific cell line that could be used as an adequate model to study the process of an EMT in vitro and in vivo, we isolated cells from a mammary gland tumor of the MMTV-PyMT (FVB/N) transgenic mouse model of breast cancer[26]
3 out of 6 mice from the long-term TGFβ-treated (LT) group yielded 2–3 metastases and only 1 out of 6 mice in the parental group yielded just one metastasis. These results collectively suggest that PyMT-1099 cells are a suitable model to study primary tumor growth and invasion, tumor cell EMT, and the formation of lung metastasis in immunocompromised mice in vivo
Summary
An epithelial-mesenchymal transition (EMT) has been implicated in cancer metastasis, drug resistance, and in conferring stem cell-like traits to cancer cells. Few examples include the normal murine mammary gland (NMuMG) cells[18], Py2T cells[19], the 4T1 cell series[20], Madin-Darby canine kidney cells (MDCK) cells[21] or the human cell lines MCF10A22,23, MCF724 or immortalized human mammary epithelial (HMLE) cells[16] While these cell lines are used across laboratories studying EMT, they are associated with some caveats. While NMuMG, MDCK and MCF10A cells undergo an efficient transition from an epithelial to a mesenchymal phenotype in response to TGFβ in vitro, these cells are only immortalized and cannot be used to study a cancer-associated EMT in vivo. Py2T cells overcome this problem as they have been derived from a mammary gland tumor of a MMTV-PyMT transgenic mouse and can be transplanted into mice to study cancer cell EMT in vivo. PyMT-1099 cells are an excellent model for EMT and MET research both in vitro and in vivo
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