Attempts of Transmission of the Newt Melanoma by Nucleic Acids Preparations.

Abstract

In the present study attempts were made to obtain DNA extracts with tumorigenic activity from the melanoma of the newt (Triturus cristatus Laur.). The DNA, prepared by two different methods from melanomas that had been transferred by cells for several generations, was injected subcutaneously in adult animals. Control animals were not treated or received DNA isolated from normal homologous organs. In all 320 animals were used, 238 of which were given DNA. The DNA preparations obtained according to the procedure of Colter et al. failed to induce tumors in any of the 111 inoculated animals, while the treatment with DNA extracted according to Kirby's method (127 cases) from tumors as well from normal tissues resulted in the development of melanomas with an incidence significantly higher than that observed in the group of untreated animals; however, the activity of the extracts was not modified by DNase treatment. The influence of factors such as neoplasia spread in the donors, duration of observation, geographical origin of animals and season of treatment was considered. Altogether 934 animals were studied, including those of other experimental series reported elsewhere: 670 were given nucleic acids extracted from tumors or normal organs, 204 received tumor or normal organ transplants, 60 were untreated. Of interest is the fact that the overall incidence of melanoma was much high in animals coming from areas of high industrialization, i.e. in the newts from the environs of Pavia (54.1 %), than in those from Naples (11 %): the difference between the two groups was highly significant and independent of the treatment. Due to the high tumor incidence in the newts from Pavia, no correlation could be demonstrated between biological activity of nucleic acid extracts and the above mentioned factors in the 670 animals treated. However, in the case of the newts from the Naples area a higher frequency of tumors was observed after treatment with nucleic acids extracted from melanoma, than after treatment with nucleic acids from normal organs: the result is statistically significant only at the 5 per cent level with the χ² test.