Carcinogenesis Experiments Using Human Skin Xenografted onto SCID-lineage Mice

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Carcinogenesis experiments have been performed in in vivo study system of mouse skin that is applied with chemical carcinogens or in vitro study system using cultured cells. Although these experiments have recently revealed a lot of information on carcinogenesis at molecular levels, precise carcinogenesis process in human organs is still unclear. Of course, it is not permitted to perform in vivo carcinogenesis experiments in humans. To produce a new in vivo experimental system of human skin, we tried to use human normal or diseasedskin transplanted onto scid-lineage mice and performed carcinogenesis experiments using the system. The following results were obtained by the present study.1. It was revealed that nude-scidmice is an excellent recipient of human skin graft. Grafted human skin on this mouse was well maintained and could be used for various kinds of experiments.2. Atypical cells of human precancerous skin lesions such as Bowen's disease survived in the grafts transplanted onto nude-scidor beige-scid mice. The survival rate in nude-scidmice was better than that in beige-scidmice. Progression into invasive carcinoma was hardly observed, however, a lesion of Bowen's disease transplanted onto a beige-scid mouse showed progression into invasive SCC during 223 days' observation period.3. Application of a chemical carcinogen, DMBA,to transplanted human skin accompanied with UVB irradiation did not produce obvious cancer macroscopically. Microscopic examination, however, revealed that intraepidemal proliferation of atypical keratinocytes in some of the skin grafts.