[Estradiol and 3 H-thymidine incorporation in cultured human cancer cells (breast-endometrium)].

Nuclear incorporation of 3 H-Thymidine is widely used as a measure of DNA synthesis and cell proliferation. We have studied by this way the growth-stimulating action of estrogens on a human breast cancer cell line (FAM). We have observed discrepancies between 3 H-Thymidine incorporation and true cell proliferation: after estradiol treatment, we have noted increased incorporation of DNA precursor but no change in the cell number. Our preliminary results show that there was no increase of the size of nuclei, no increase of the DNA content. So, there is a need for a cell number control of results recording a growth promoting activity when only based on 3 H-Thymidine incorporation. A biochemical explanation of this discrepancy is submitted.