Abstract 1222: Establishment of a reliable metastasizing syngeneic breast cancer mouse model using orthotopically implanted 4T1 cells after several rounds of isolating and reimplanting lung metastases
Authors: Lingnau Andreas , Hoffmann Steffen , Moor Sandra , Schaefer-Obodozie Cynthia , Schaechtele Christoph 
Published: May 2015

Abstract
Many human breast cancer cell lines have been implanted into immunodeficient mice in order to establish in vivo xenograft models, subcutaneous or orthotopic variants, in order to mimic this type of cancer as good as possible. However, especially the metastasising capabilities of these models turned out to be highly disappointing. In order to get more reliable models, breast cancer cells have often been implanted intravenously or intracardially rather than orthotopically. These models do work fine but resemble only limited parts of the complicated metastasis process. Therefore, a metastasis event originated from an orthotopically growing breast tumor seems more appropriate and displays an expanded view on the process of metastasis.
In the model presented here, the murine brast cancer cell line 4T1 was transduced with fire fly luciferase and implanted orthotopically into the fat pad of female BALB/C mice. The metastasis rate in this model is known to be better than in the common human xenografts transplanted in mice, although still limited. In order to get higher metastasis rates we tried to improve this model by resecting and recultivating the metastases of the invaded lungs after orthotopic implantation of the 4T1 cells. Cultured cells were checked for in vitro luciferase activity in parallel with ex vivo analysis of the lung tissue part which was used for the isolation of the cells. After using this approach for several rounds, what we refer to as “subpopulationing”, we checked for increased metastasis properties of this newly isolated breast cancer cells. The new 4T1-M-ortho-luc cells were implanted ortotopically in parallel to the parental 4T1-luc cell line and we analysed 9 different organs ex vivo for luciferase activity. Whereas in the parental model only in lung tissue metastasis in all implanted mice (12/12) was detectable, the metastasis rate in the new model, generated by “subpopulationing”, bounced up to 4 organs with measurable metastasis in 100 % of the mice and in general to a much higher degree of metastasis in most other organs. Only in liver tissue no metastases could be detected in both models.
Treatment of the mice with Doxorubicin clearly diminished tumor growth in both breast cancer models and can therefore serve as a potent positive control here.
With this new 4T1-M-ortho cell line we have available a metastasing breast cancer cell line that shows reliable metastasis observed in several organs of the mouse when implanted orthotopically. This model is suitable for testing potential anti-meatstasizing compounds aginst breast cancer. In addition, since this model is established in immunocompetent mice, and is therefore also perfectly suited for approaches involving the immune system of breast cancer patients.
Citation Format: Andreas Lingnau, Steffen Hoffmann, Sandra Moor, Cynthia Schaefer-Obodozie, Christoph Schaechtele. Establishment of a reliable metastasizing syngeneic breast cancer mouse model using orthotopically implanted 4T1 cells after several rounds of isolating and reimplanting lung metastases. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1222. doi:10.1158/1538-7445.AM2014-1222