Effect of Injected Frog-Kidney Tumor Extracts on Development of Tumors Under Promoting Conditions2

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Abstract
Previous reports indicated that Lucke'' kidney tumors occurred spontaneously with an incidence of 35 to 50 percent when Vermont Rana pipiens were maintained for 35 weeks under the tumor-promoting conditions of large body size and high environmental temperature. However, workers reporting group differences in tumor incidence related to injection of tumor extracts had in all instances used conditions in some way favoring low incidences of spontaneous tumor formation. In this report, results of injected tumor extracts in frogs kept under promoting conditions are given. The rate of tumor formation in frogs given injections was somewhat accelerated for several months, but both experimental and control groups eventually reached the same incidence. These findings are discussed in the light of the presumed viral nature of the Lucke tumor.