Aromatase activity and the effect of estradiol and testosterone on DNA synthesis in endometrial carcinoma cell lines

Human endometrial and breast carcinoma cell lines were examined for aromatase activity and the effects of sex steroids (estradiol and testosterone) on DNA synthesis. Aromatase activity was high (greater than 500 fmol/10⁷ cells/24 h) in the cell lines MCF-7 and OMC-2, moderate (100–499 fmol/10⁷ cells/24 h) in the cell lines HEC-59 and Ishikawa, and low (less than 100 fmol/10⁷ cells/24 h) in the HHUA cell line. A substantial stimulation of DNA synthesis by estradiol (10⁻⁹M) was observed in cell lines HEC-59, OMC-2, and MCF-7, with an increase in ³H]thymidine uptake of over 250%. The Ishikawa cell line was stimulated moderately (115–249%). No estradiol-induced increase in DNA synthesis was observed in HHUA. Responsiveness of DNA synthesis to testosterone was observed in cell lines that showed the greatest response to estradiol, namely HEC-59, OMC-2, and MCF-7. Otherwise, estrogen-responsiveness did not always correlate with a significant aromatase activity. These data suggest that some but not all endometrial carcinomas may possess an aromatase-dependent growth stimulating system.