Heterogeneity of induced testicular interstitial cell tumors of mice as evidenced by steroid biosynthetic enzyme activities.

Quantitative enzyme studies (17a-hydroxylase, 17,20-desmolase, 21-hydroxylase, and 20a-hydrox-ydehydrogenase), using as a source of enzyme small fragments (25-48 rag) of estrogeninduced testicular interstitial cell (Leydig cell) tumors of mice and their first generation transplants in castrate male isogeneic hosts, show rather conclusively that such tumors are composed of heterogeneous populations of hormone-producing cells. Our data supported the original concept that, during tumor induction or shortly thereafter, several enzyme systems involved in steroid biosynthesis in Leydig cells decrease in an apparently random fashion. However, it appeared evident that at least in certain neoplastic interstitial cells the activity of 20a-hydroxydehydrogenase, an enzyme whose functional significance has not yet been clearly established, increased significantly.