Nonmalignant and Malignant Changes in Hamsters Inoculated with Extracts of Human Osteosarcomas

Abstract

Several Years ago we announced the discovery of a virus that induces osteosarcomas in mice and described the radiographic appearance of the neoplasms as they developed in animals that had been inoculated with this virus (FBJ) on the day of birth (1, 2). Since then we have been searching for a similar oncogenic agent in human osteosarcomas by injecting cell-free extracts of tissues from osteosarcoma patients into neonatal Syrian hamsters. Previous reports have described the lesions that arose in hamsters soon after injection of such extracts (3) and the initial 6 osteosarcomas produced by material from the first 7 patients (4). The present interim report extends the earlier observations and illustrates some of the radiographic changes that have appeared in hamsters treated with material from 43 patients with osteosarcoma. Materials and Methods The technics used in the search for a virus responsible for human osteosarcomas are modifications of those developed by Gross (5), as described in earlier reports (3, 4). Into the right lower abdominal cavity of zero to four-day-old Syrian hamsters is injected a 0.1 to 0.2 ml of extract of surgical or autopsy specimens from patients with osteosarcoma, prepared by differential centrifugation after grinding with sodium citrate. Tissue specimens have included primary bone tumors, muscle adjacent to or some distance away from the primary tumor, and metastatic lesions occurring in bone and lung. In some instances tissues from hamsters treated with such extracts have themselves been extracted, and these were then injected into other newborn hamsters. Occasionally, successive passages from hamster to hamster have been made, the first animal in the series having received an extract of human tissue. Control material, processed in the same way, has consisted of (a) plasma or muscle from patients without evidence of any kind of neoplastic disease and (b) tissues from untreated hamsters. Additional experience is being derived from a related experiment in which hamsters have been treated with comparable extracts of canine osteosarcomas. The inoculated hamsters are observed daily and, except for those used for passage of extract to other hamsters, are permitted to live until moribund. All animals are autopsied, and tissues are then selected for histologic study. The skeleton is examined radiographi-cally at about four weeks of age and then at four to eight-week intervals throughout life, depending upon current findings. For radiography, the animals are anesthetized with intraperitoneal sodium pentobarbital. A beryllium-window rotating anode x-ray tube with a 1.5-mm focal spot is used without filtration in order to utilize the low-energy x rays. Kilovoltage varies from 35 to 39 kVp and time from 1/10 to 3/20 seconds at 200 mA, depending on animal size; target-to-film distance is 16 inches.