Breast Cancer Produced in Male Mice of the C57 (Black) Strain of Little

Bittner 1 has shown that hybrids from a cross between a mouse from a strain having a high incidence of mammary cancer and one from a low tumor strain have a high or low incidence of breast cancer depending on what type of mother they nurse. If the nursing mother comes from the strain having the high incidence of spontaneous tumors, a large percentage of the female hybrids will develop mammary cancer. If they are nursed, on the other hand, by a female from the low tumor strain very few will develop breast cancer. Female mice from a high cancer strain nursed by their own mothers have a high incidence of mammary cancer while if they are foster-nursed by a mouse from a low tumor strain the chance that they will develop breast cancer will be materially reduced.

An attempt was made to confirm this observation on a different strain of animals. Mice of the RIII (Paris) strain of Dobrovolskaia Zavadskaia were given to a female of the C57 (black) strain of Little to nurse while the young of the latter were given to the RIII mother. The RIII females have an incidence of spontaneous mammary cancer of 70% in virgin females. The incidence in C57 black females is less than 1%. The incidence of breast cancer occurring in these 2 groups of animals appears to confirm Bittner's observations but the number of animals is as yet not very statistically significant and consequently will be reported later in another place.

Since litters were shifted within less than 12 hours of birth when the sex was often hard to determine, many males which had been foster-nursed by mothers of the other strain became available.