The Effect of Testosterone Propionate on Mammary Tumors in Mice of the C3H Strain

A rela t ionship be tween estrogenic activity and the product ion of tumors of the m a m m a r y g land has been clearly demons t r a t ed in various strains of mice. In v iew of the inh ib i tory action of testosterone on estrus, lactation, and the vaginal response to estrone in mice (4, 5), t he possibility of affecting spontaneous t u m o r format ion by inhib i t ion of estrogenic activity seemed wor thy of fu r the r invest igat ion. In 1936 , Lacassagne (2) reported that injections of testosterone had not al tered the inc idence of spontaneous m a m m a r y cancer in females of a h igh cancer strain, but the a m o u n t of h o r m o n e used was small. This report presents the end results of long-cont inued adminis t ra t ion of testosterone propionate on the developmen t of spontaneous m a m m a r y carc inoma in female mice of a h igh cancer strain (a ) w h e n injections were begun by the 5th week of life, and (b ) w h e n injections were given to older females wi th a history of n o r m a l breeding. It also includes observations on the fai lure of testosterone to affect the g r o w t h rate of m a m m a r y carc inoma in mice w h e n admin i s te red after the t u m o r is of palpable size. T h e exper iments were started in the spring of 1938 and extended over 2 years. T h e y were well unde r way w h e n the repor t of N a t h a n s o n and A n d e r v o n t (3) was published, bu t since our exper iments differed in some respects f rom theirs, it was decided to con t inue them.