Induction of papillomas in rabbits with nucleic acid extracts from Vx7 carcinomas.

Nucleic acid extracts from transplantable carcinomas Vx7 and Vx2, long maintained in domestic rabbits, were assayed for their ability to produce papillomas in animals of this kind. The Vx7 had been serially transferred 111 times when this was attempted and Vx2 was in its 203rd generation. The nucleic acid extracts from the Vx7 carcinomas consistently yielded papillomas whereas those from Vx2 completely failed to do so. The tumorigenicity of the Vx7 extracts was slight and regression of the induced papillomas often took place, as happens not infrequently to the growths caused by nucleic acid extracts obtained directly from papillomas. Malignant conversion, a common event in tumors induced by Shope papilloma virus, was also observed to occur among papillomas which were induced by the nucleic acid extracts from Vx7 carcinomas, and which kept persisting over a year on the skin of experimental animals.