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.