Effect of progesterone and estradiol-17beta on nucleic acid synthesis in vitro in carcinoma of the endometrium.

Nucleic acid synthesis was studied in 26 tumor specimens, during a one-hour in vitro incubation with the addition of progesterone and estradiol-17beta. On the response scale used, deoxyribonucleic acid and ribonucleic acid synthesis decreased linearly as the logarithmic concentration of either hormone increased. Inhibition of nucleic acid synthesis was highly significant (P less than 0.001) at 80 microgram per milliliter of progesterone and at 40 microgram per milliliter of estradiol. No evidence of synergism was found when the two hormones were combined at these concentrations. In Grade I and II tumors, the effect when both hormones were combined approximated the sum of effects of the individual hormones. In Grade III tumors, little difference was seen between treatment groups.