Activation of retrovirus in transgenic mice: association with development of olfactory neuroblastoma.

A line of transgenic mice that express the human adenovirus type 12 E1A and E1B genes under the regulatory control of the mouse mammary tumor virus long terminal repeat was studied. Mice from this line develop olfactory neuroblastomas at approximately 6 months of age. Large numbers of type C retrovirus (ecotropic murine leukemia virus) particles were found in the tumor rosettes. No similar examples of virus activation were identified in tumors from other transgenic experiments. Examination of spontaneous olfactory neuroblastomas from three domestic cats also demonstrated retrovirus in tumor rosettes.