Smooth muscle and bone neoplasms in transgenic mice expressing SV40 T antigen.

Transgenic mice carrying the SV40 early region fused to the Drosophila hsp70 promoter developed smooth muscle and bone neoplasms. The smooth muscle tumors appeared in aged mice and were preferentially located on the muzzle or eyelids. Multiple neoplasms were often present and each appeared to be an independent proliferation. In contrast, the bone tumors typically developed in the petrous ridge and had all the features of osteogenic sarcomas, displaying distant metastasis and invasion of the brain. Cells in both types of tumors exhibited nuclear expression of SV40 T antigen. Mice homozygous for the transgene had a shorter latency for appearance of smooth muscle tumors and developed osteosarcomas more frequently than hemizygous mice. This model system implicates the cellular T antigen-binding proteins, such as Rb and p53, in the pathogenesis of bone and soft tissue neoplasms in mice.