| Abstract: | The growth of numerous human oestrogen target cell lines is said to have been stimulated by oestradiol. We studied the action of this hormone on the growth of two human cancer cell lines originating from endometrium (GUS), and from breast (FAM). Oestradiol was inactive on endometrial cell multiplication as well as on their tritiated thymidine uptake, but in FAM breast cancer cells, we noticed a discrepancy between tritiated thymidine uptake and actual cell proliferation: there was a 40% increase in DNA precursor uptake, but no change in either the number of cells or in their DNA content, both of which were verified by two different methods. Therefore, an actual increased nuclear (autoradiographic) uptake of thymidine did take place in oestrogenized cells, associated with an increase of incorporation into DNA (a rise of radioactivity in the acid-insoluble materials), but finally there was no greater total DNA increase in the whole treated population than in control cells. Then we examined the metabolism of tritiated thymidine in oestradiol-treated FAM cells. We extracted the radioactive thymine nucleotides and characterized them chromatographically: the oestradiol caused an increase in the labelling of deoxythymine monophosphate (TMP). How these results are consistent with both unmodified cell count and whole DNA content is discussed. |
