Enhanced osteosarcoma growth produced in rats by osteosarcoma allografts.

Transplanted syngeneic osteosarcomas (induced by 32P in DA rats) grew significantly larger in DA rats receiving a simultaneous transplant of allogeneic osteosarcoma than in rats receiving syngeneic tumour only (P less than 0-01). Two other malignant allogeneic tumours, and allogeneic spleen cells, did not alter the growth of the transplanted syngeneic osteosarcomas. When the allogeneic osteosarcoma was given 7 days before the syngeneic tumour, the reverse effect (retardation) occurred. When given 7 days after the syngeneic tumour cells, the effect on both syngeneic and allogeneic tumour growth was variable. Some possible reasons for these findings are discussed, and the argument is presented that immunological phenonema are involved in the reaction.