Three spontaneous tumors of the C3H mouse have been used in a comparison of their transplantability and radiation response (local control) in syngeneic C3Hf/Sed mice and in allogeneic athymic NCr/Sed-nu/nu nude mice. The tumors were: MCaIV, a moderately well-differentiated mammary carcinoma; FSaII, a poorly differentiated fibrosarcoma; and SCCVII, a moderately well differentiated squamous cell carcinoma. The tumors were studied as fourth to seventh generation transplants. Assays to determine the number of tumor cells that, on the average, transplant the tumor to half of the recipients or transplant sites (TD50) demonstrated that these 3 tumors transplanted into the s.c. tissue of the NCr/Sed-nu/nu as readily as of C3Hf/Sed mice. The TD50 for MCaIV was slightly but significantly lower in 4-week-old NCr/Sed-nu/nu mice which had received 6 Gy whole body irradiation (WBI) 24 h before transplantation, namely, 5.8 × 104 (95% confidence limits, 4.5–7.6) versus 7.8 × 104 (6.0–10.0). The 6-Gy WBI did not affect the TD50 for 8- to 10-week-old mice. Similarly, the TD50 for SCCVII was lower in 6-Gy WBI NCr/Sed-nu/nu recipients (1.5 × 104versus 3.9 × 104). The TD50 for FSaII was not affected by 6-Gy WBI. Further, the TD50 for FSaII following i.v. injection of tumor cells (transplant to lung) was the same for C3Hf/Sed and NCr/Sed-nu/nu mice (this obtained for normal or 6-Gy WBI-treated subjects). The radiation doses which on the average achieve control of half of the MCaIV, FSaII, and SCCVII tumors were lower, higher, and the same in NCr/Sed-nu/nu than in C3Hf/Sed mice, respectively. The radiation doses which achieve control of half of the MCaIV and SCCVII tumors were not affected by 6-Gy WBI before transplantation.

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This work was supported in part by USPHS Grant CA13311 awarded by the National Cancer Institute, Department of Health and Human Services.

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