A Transmissible Leukemia in the "A" Strain of Mice

Abstract

The genetic uniformity of the Strong A strain (1), brought about by many years of brother-to-sister matings with a consistent elimination of all collateral lines, reflects itself in the uniformly positive response of mice of this strain to the implantation of tumors arising in the strain, whether spontaneous or induced experimentally. The rate of growth is quite uniform and there are no regressions. In attempts to influence the growth of neoplasms in animals by various methods, it is imperative that tumors with reproducible growth and physiological characteristics be used. These requirements are best met by using tumors arising in genetically uniform animals. Previously leukemia has not been observed in the Strong A strain. The present report concerns a leukemia in these mice which seems ideal for experimental purposes. The original case of leukemia observed in this strain developed in a mouse which had received prolonged injections of estrogenic hormone in connection with studies on the induction of cancer of the breast. This mouse, 42A, received, beginning at the age of 6 days and continuing for the next 275 days, a total of 19,500 international units of hydroxy-estrin benzoate in solution in oil. At the end of this time a laparotomy was performed and the right horn of the uterus was split open, after which 5,000 international units of hydroxy-estrin benzoate per week were injected subcutaneously for three more weeks. Eight days after the first laparotomy the abdominal cavity was again opened. At this time the uterine horns were grayish white and the right horn had not healed. The ovaries, which had been very small eight days previously, were considerably enlarged.