ESTABLISHMENT AND CHARACTERIZATION OF A NEW MAMMARY ADENOCARCINOMA CELL-LINE DERIVED FROM MMTV NEU TRANSGENIC MICE

A new murine cell line, named MG1361, was established from mammary ade nocarcinomas arising in a MMTV-neu transgenic mouse lineage where brea st tumors develop in 100% of females, due to the overexpression of the activated rat neu oncogene in the mammary gland. The MG1361 cell line shows an epithelial-like morphology, has a poor plating efficiency, l ow clonogenic capacity, and a doubling time of 23.8 hours. Karyotype a nd flow cytometry analysis revealed a hypotetraploid number of chromos omes, whereas cell cycle analysis showed 31.2% of cells to be in the G 1 phase, 21.4% in S and 47.4% in G2 + M. This cell line maintains a hi gh level of neu expression in vitro. The MG1361 cell line was tumorige nic when inoculated in immunodeficient (nude) mice and the derived tum ors showed the same histological features as the primary tumors from w hich they were isolated. MG1361 cells were positive for specific ER an d PgR binding which was competed by tamoxifen, making this cell line u seful for the evaluation of endocrine therapy. Moreover, they were sen sitive to etoposide treatment, suggesting that they could be a model f or the study of chemotherapy-induced apoptosis. As the tumors arising in MMTV-neu transgenic mice have many features in common with human ma mmary adenocarcinomas (Sacco et al., Gene Therapy 1995; 2: 493-497), t his cell line can be utilized to perform basic studies on the role of the neu oncogene in the maintenance of the transformed phenotype, and to test novel protocols of therapeutic strategies.