Relapse of androgen-dependent tumour of mouse (Shionogi Carcinoma 115) after castration and oestrogen treatment.

To elucidate relapse of hormone-dependent tumour, mice bearing androgen-dependent carcinoma (SC 115) underwent castration or received oestrogen treatment. Since SC 115 consisted of two types of cells, androgen-sensitive round cells and -insensitive spindle-shaped cells, changes in the ratio of the cellular population were examined. After castration, spindle-shaped cells increased temporarily as the tumour regressed, then the round cells increased significantly along with an increase in size of the tumour. Oestrogen treatment did not influence the population. Androgen dependency and the growth rate of round cells were generally preserved in the next generation. Therefore, relapse may occur by an increase in the number of androgen-sensitive round cells.