ESTABLISHMENT OF A CELL-LINE (MCM-B2) FROM A BENIGN MIXED TUMOR OF CANINE MAMMARY-GLAND

A cell line was established from a benign mixed tumour of the canine m ammary gland. Light microscopy of the cells cultured on plastic dishes revealed monolayer colonies. Cells that grew within the collagen gel matrix formed large three-dimensional colonies with a branching patter n. Immunohistochemically, these cells reacted intensely with anti-vime ntin antiserum and mildly with anti-desmin antiserum. Ultrastructural examination revealed a large nucleus, intracytoplasmic organelles and intermediate filaments, which varied among cells. The cells possessed an abnormal chromosome number, an average of so per cell. Histological ly, the xenografted tumour of cultured cells was similar to anaplastic carcinoma and reacted strongly with antivimentin antiserum, mildly wi th anti-desmin antiserum, and weakly with anti-keratin antiserum. The average chromosome number of cells form the xenografted tumour was the same as that of the original cultured cells. These findings suggest t hat the cell line might be derived from stem cells or atypical cells, and that it should be useful as a model for the study of cell differen tiation and proliferation in canine mammary rumours.