Tumour incidence in mammary glands transplanted from the strains C3H and O20 into their mammectomized F1-hybrids.

Abstract

AbstractIt has been demonstrated that genetic factors play an important role in the genesis of mammary cancer in mice but it was not known if the genetic action is localized in the mammary gland tissues or if the genetic influence is effective through some systemic mechanism. In this investigation the mammary glands from the inbred strains C3Hf and O20, differing in the incidence of mammary tumours, were transplanted into a common host, the F1 hybrid, so that systemic influences would be equal. A difference in susceptibility to tumour development was found between the transplanted C3Hf and O20 mammary glands. In the group of animals free of the agent there is a difference in tumour frequency. In the animals carrying the mammary tumour agent this difference is expressed in the average tumour age at which the tumours develop. The genetic susceptibility in these two strains is, therefore, retained in the transplanted mammary glands.Transplantation per se has no influence on tumour development.Transplanted mammary glands react in the same manner as mammary glands in situ. All transplantations have been done into completely mammectomized hosts to avoid interference with tumours developing in the glands of the host. Investigations with partly mammectomized animals have shown that the mammary tumour frequency and the average tumour age are related to the amount of mammary gland tissue present. A reduction of the mammary gland tissue also reduces the tumour frequency or delays the appearance of mammary tumours.