Cloning of estrogen-responsive messenger RNAs in the T-47D human breast cancer cell line
A complementary DNA library has been constructed from the polyadenylated mRNA of steroid-deprived T-47D cells which had been restimulated with estrogen for 24 h. Screening of 15,000 recombinants by sequential rounds of colony, Southern and Northern blot differential hybridization has identified eight different clones which vary in abundance and are stimulated between 2.5- and 8-fold by estrogen. Whereas five recombinants hybridize to single mRNA sequences, two clones, pSyd 2 and pSyd 8, appear
... and pSyd 8, appear to hybridize weakly to an addition mRNA sequence and one clone, pSyd 3, hybridizes to a multiple mRNA species (1.9, 1.7, 0.9, and 0.5 kilobases). Furthermore, at least one clone, pSyd 2, appears to be expressed only in ER-positive cells. While its level of expression is stimulated by estrogen approximately 4-fold in all the estrogen and progesterone receptor-positive cell lines tested (T-47D, ZR-75-1, and MCF-7), pSyd 2 levels in the estrogen and progesterone receptor-negative HBL-100 cell line were lower than the corresponding levels in estrogen-stimulated T-47D cells and were unresponsive to estradiol. These results show that we have isolated several estrogen-responsive sequences which will be useful in studying hormone regulation of gene expression and may provide additional markers of hormone responsiveness in breast cancer.