Mammary Neoplasia after in vitro X-irradiation of Mammary Tissue

Abstract

WE have been unable to find any reports that mammary neoplasia can be induced in rats by in vitro exposure of mammary tissue to ionizing radiation. (Our use of the term in vitro implies the removal of mammary tissue, its exposure to radiation in vitro and its subsequent transplantation into the same or another rat.) Dao et al.¹ have shown that mammary tissue taken from a rat given 7,12-dimethyl-alpha-benzanthracene (DMBA) when transplanted into another rat often developed mammary neoplasia in the transplant, and Brennan et al.^2,3 have reported that the exposure of mammary tissue in vitro to DMBA, with autologous transplantation into the same rat, often resulted in mammary neoplasia in the transplant. For the case of the experiments of Brennan et al., a troublesome question remains. Was some DMBA transferred with the mammary transplant ? If so, then the induction may have taken place in the transplanted tissue and may consequently have been in vivo. Brennan et al. attempted to control the transfer of DMBA by washing the mammary tissue and to monitor the DMBA remaining in the mammary tissue by use of ultraviolet fluorescence. It is not, however, clear whether an ultraviolet control was performed, so it is possible that the subsequent neoplasia was in fact caused by the exposure to ultraviolet light.