Viruses in Osteosarcomas Induced by ²²⁶Ra

Summary

Three groups (15 in each) of 3-month-old mice were injected intraperitoneally with 0·5 μCi ²²⁶Ra. They were male and female C3H/H and female CBA/H. The groups were matched by similar controls that were not injected. Osteosarcomas were found in 14/15 of the female C3H/H mice–animals known to carry mammary-tumour viruses in milk–compared with 6/15 in their male counterparts. In CBA/H female mice, which have a very low incidence of both mammary tumours and leukaemia, osteo-sarcomas developed in 7/15 of the animals. The CBA/H mice lived about 5–8 months longer and revealed their osteosarcomas at a correspondingly later time than C3H/H mice. Virus particles were observed in each of the three mammary tumours and in 15 out of the 17 osteosarcomas examined by electron microscopy. No definitive statement can be made from this experiment whether or not osteosarcoma was caused by a virus; but the results suggest that viruses may be a contributory factor in the development of osteosarcoma in these animals.