Radiation responses of subrenally transplanted syngeneic and allogeneic mouse fibrosarcomas.

The radiation responses of two tumor types transplantable into C3H/He mice and differing in radiosensitivity, i.e., 3-methylcholanthrene (MCA)-induced fibrosarcoma and NFSa fibrosarcoma, were investigated using the subrenal capsule assay. Subrenal tumor growth was histologically confirmed. Volume regression and regrowth of subrenal capsule-implanted and subcutaneously implanted tumors after X-irradiation were compared. No difference was found in tumor growth speed (volume doubling time: 1.2-1.3 days) between the subrenal transplants into C3H/He mice, syngeneic to the tumor grafts, and those into immuno-incompetent C57BL mice, allogeneic to the tumor grafts. The tumor growth rates for subrenal capsule transplants were 1.7- to 1.8-fold higher than those for subcutaneous transplants of the same tumor type. A marked difference was found in the radiation responses of the two tumor types by the subrenal capsule assay, i.e., tumor regrowth time following 20 Gy irradiation was more than 8 days for MCA-induced fibrosarcoma and 4.5-5.4 days for radioresistant NFSa fibrosarcoma. These values correlate well with the estimated radiation sensitivities of these tumors.