The carcinogenic effects of chronic exposure to ultraviolet radiation were compared in three inbred mouse strains with different coat colors. Albino mice (BALB/cAnN) developed tumors earlier than agouti [C3H/HeN (mammary tumor virus negative) hereafter called C3H-] or black (C57BL/6N) mice, and a large proportion of the tumors in the albino strain arose on the ears, in contrast to the other strains) in which dorsal tumors predominated. The most common histological types of tumor observed were fibrosarcomas, followed by squamous cell carcinomas. The types and frequency of types were comparable among the three strains. On the basis of a comparison of tumor growth in normal and immunosuppressed syngeneic recipients, primary tumors from the albino strain were the least antigenic as a group, whereas the C3H- tumors exhibited the greatest degree of antigenicity. In BALB/cAnN mice 33% of the ultravioletinduced tumors tested failed to grow in normal syngeneic mice although they grew in immunosuppressed recipients. In C57BL/6N mice 54% and C3H- mice 75% of the tumors tested were not transplantable in normal syngeneic recipients and grew only in immunologically deficient hosts.

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This work was supported by the National Cancer Institute under Contract N01-CO-25423 with Litton Bionetics, Inc., Bethesda, Md.

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