Distribution of Metastases in the Brown-Pearce Tumor. III. Effect of Homologous Material. ∗

It has been shown that a single injection of a saline emulsion of 0.05-0.1 cc of Brown-Piearce tumor tissue which has been kept frozen for 10 days or longer in an anaerobic state will render rabbits susceptible to subsequent transplantation with the tumor. 1 The injection of this homologous material increases (a) the incidence and volume of the primary tumor growths, and (b) the incidence, number, and volume of the metastases, with a consequent decrease in the longevity and an increase in the mortality of the animals. The material, when injected, produces no obvious lesions, nor does it visibly affect the health of the animal. It can be desiccated, passed through a Berkefeld “V” filter, 2 and inactivated by heating to 55°C.^a It differs biologically from the spreading factor described by Duran-Reynals. 4

It has been shown that the relative distribution of metastases in this tumor is constant and characteristic following intratesticular inoculation, and remains unaffected by long transplantation into various breeds of rabbit. 5 The present paper concerns the possible effects of the injection of the homologous material in relation to the relative distribution of metastases.

Two groups of rabbits were used. The first consisted of 202 young adult male rabbits from 19 standard breeds, which were injected with the tumor alone. 5 The second consisted of 44 young adult male rabbits of pure and mongrel stocks, which received a single injection of 0.3 cc of the homologous material into one testicle 2 weeks before inoculation with the tumor. Both groups of animals received a single unilateral intratesticular injection of 0.3 cc of a saline emulsion of fresh Brown-Pearce tumor. The variations of breed in the 2 groups were not considered important, since this factor has been shown not to affect the relative distribution of metastases. 6