Expression of type II and type XI collagens in canine mammary mixed tumors and demonstration of collagen production by tumor cells in collagen gel culture.

The development of cartilaginous collagen types, II and XI, in canine mammary mixed tumors was studied biochemically and immunohistochemically. In mixed tumor, an alcian blue-positive myxomatous region appeared in the stroma, where round-shaped proliferating myoepithelial cells were scattered. Type II collagen was distributed in metaplastic cartilage matrix, while type XI was located only in the pericellular region, where proliferating cells were positively stained with anti-actin and anti-keratin antibodies. The accumulation of collagen types II and XI in the tumor mass was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting of the extract of the lesion using type-specific antibodies to collagen types II and XI. Tumor cells isolated from metaplastic tumor mass expressed both collagen types II and XI and myoepithelial types of cytoskeleton in gel culture, in which an alcian blue-positive substance became detectable in the pericellular region on day 3 and type II and type XI collagens on day 5. This may be a useful model for studying chondrocyte-type gene expression during tumorigenesis.