A chemical investigation of keratin and carcinomas deriving from rabbit papillomas (Shope).

In 1933, Shope (14) described a virus-induced papilloma occurring naturally in the cottontailS rabbit (genus Sylvilagus) and transmissible to the domestic rabbit (genus Oryctolagus). Later, Rous and Beard (13) found that the experimentally in duced papillomas in domestic rabbits often pro gressed to carcinomas; and Syverton and Berry (16,17)observedthesamephenomenon incotton tail rabbits. Because of its possible significance for the pathogenesis of mammalian cancers in@general, this virus-induced papilloma-to-carcinoma se quence aroused wide interest and has been the sub ject of numerous investigations. An outstanding feature of the Shope papilloma .istheproduction ofexcessive amounts ofkeratin ized epithelium, which may develop into enormous epithelial horns, sharply demarcated from the Un derlying tissue.t The present communication con cerns some of the chemical properties of this “keratin― and also of carcinomas deriving from the papillomas in cottontail rabbits. Keratinization, or cornification, which reflects the ultimate natural alterative change in super ficially situated structures of ectodermal origin, yields a wide variety of hard anuclear entities, such as horns, hoofs, nails, hair, the outer layers of