Cell-free Transmission of a Methylcholanthrene-induced Malignant Melanoma in Amphibians

Abstract

Methylcholanthrene-induced malignant melanomas of the newt can be successfully transplanted by cell-graft with a 80–100 percent take. Filtrates were prepared from a transplanted tumor at the 5th passage. The aseptically removed tumor fragments were ground by hand in a mortar, 0.05 M sterile chilled citrate buffer at pH 6.6 (containing 1 mg percent of jaluronidase) being added to obtain a cell suspension of 5 percent concentration. After 1 hour of standing at room temperature (25 – 27 °C), the cell suspension was centrifuged at 5.000 x g at 0°C, for 10'; the supernate was centrifuged again at 5.000 x g for 10′. The second supernate was then passed through membranes of 150 – 250 mμ porosity (membranfilter Gottingen N° 8) at 0°C. The filters were impervious to «E. coli», as determined by tests carried out immediately after the filtration of each extract (incubation at 37 °C for 6–8 days). Two filtrates were inoculated, subcutaneously, into a total of 15 adult newts; 9 of them developed melanomas after 1–4 months, with metastases in all organs. The transplanted and filtrate-induced melanomas were morphologically similar to the methylcholanthrene-induced tumors. Spontaneous melanoma was never observed in about 1800 newts examined in this laboratory.