Induction of Tumors in Syrian Hamsters by a Cytopathogenic Virus Derived From a C3H Mouse Mammary Tumor2

Abstract

Tumors of the kidney and heart have been induced, by a cytopathogenic virus, in Syrian hamsters. The virus, which had been recovered in tissue culture from an extract of a C3H/Jax mouse mammary tumor and serially cultivated in vitro on normal mouse cells, was injected subcutaneously into the hamsters on their 1st day of life. In 3 experiments with both random-bred and partly inbred hamsters, over 90 percent of animals died with tumors. Mortality was highest around the 12th day after the animals received the virus, and at autopsy, in most of the animals, both kidneys were massively enlarged and diffusely infiltrated with tumor. A second, lower peak incidence of death occurred around the 19th day; in these animals, nodular tumors of the kidney and heart were found. The tumors were spindle-cell sarcomas which were locally invasive and many metastasized to the lungs. A number of these tumors grew progressively after transplantation into adult hamsters and killed their new hosts. Hemorrhage into the peritoneal and pleural cavities was common in animals that died with extensive tumors after receiving the virus. Localized vascular dilatations were also commonly found in the liver, lungs, intestine, and reproductive organs of these animals. At the surface of the liver and lungs, the dilatations formed blood-filled blebs, and rupture of these blebs probably led to the hemorrhages that were observed. Newborn hamster controls that received supernatant fluid from cultures of normal mouse kidney cells, normal monkey kidney cells, or fresh culture medium developed no tumors during the first 10 weeks thereafter. A number of animals that received fluid from normal mouse kidney cultures were retained for 5½ months and they remained free of tumors. However subcutaneous tumors developed in a number of animals that received fluid from monkey kidney cultures and in one that had received fresh medium only, after a long latent period, which indicated that these animals had somehow received a small dose of virus. The results demonstrate an extraordinarily rapid and regular induction of malignancy by a mammalian tumor virus.