• T47D variant;
  • estrogen growth-inhibition

T47D human breast cancer cells were cultured in estrogen-deficient media for up to 32 months and the resulting cell line (L(hE)) exhibited unique phenotypic and genotypic characteristics. Compared to low passage (L) cells, the L(hE) cells exhibited a significantly higher rate of proliferation, unique morphological features, advanced ploidy status and 5- to 10-fold higher levels of the estrogen receptor (ER) as determined by ligand binding and Western blot analysis. Sequence analysis of the DNA binding domain of the ER revealed a C[RIGHTWARDS ARROW]A transversion which resulted in a H513N amino acid change. Treatment of L cells with 10nm17β-estradiol (E2) resulted in a greater than two-fold increase in cell proliferation which was inhibited by tamoxifen, 4′-hydroxytamoxifen, ICI 164,384 and ICI 182,780. In contrast, 10nmE2 caused a 70% decrease in growth of L(hE) cells and this antimitogenic activity was blocked by ICI 164,384 and ICI 182,780 but not by tamoxifen or 4′-hydroxytamoxifen. L(hE) cells were E2-responsive in transient transfection studies using a plasmid containing an estrogen-responsive element derived from the vitellogenin A2 gene promoter. These data show that the phenotypic and genotypic characteristics of L(hE) T47D cells resemble those described for ER-negative cell lines stably transfected with the ER.