CHARACTERIZATION OF THE ARYL-HYDROCARBON RECEPTOR AND ARYL-HYDROCARBON RESPONSIVENESS IN HUMAN OVARIAN-CARCINOMA CELL-LINES

The human ovarian carcinoma cell lines PE01, PE04, and PE06 express th e estrogen receptor and studies with the PE04 cells have shown that ta moxifen inhibits 17beta-estradiol-induced proliferation. 2.3,7,8-Tetra chlorodibenzo-p-dioxin TCDD) is a broad spectrum antiestrogen which wo rks through the aryl hydrocarbon receptor. Incubation of the three cel l lines with [H-3]TCDD followed by isolation of nuclear extracts showe d that the PE01, PE04, and PE06 cells express the aryl hydrocarbon rec eptor (23 to 87 fmol/mg protein) which exhibits sedimentation properti es (7.5 to 7.9 S) on sucrose gradients similar to that observed in oth er mammalian species. Aryl hydrocarbon responsiveness was determined b y the induction of P4501A1 mRNA levels and ethoxyresorufin O-deethylas e activity by TCDD. Induction of both parameters was observed only in the PE04 cells. Gel mobility shift assays with a consensus dioxin-resp onsive element (DRE, 26-mer) showed that after incubation of the nucle ar extracts from the 3 cell lines with P-32-DRE a retarded band formed only with nuclear receptor complex from PE04 cells. 17Beta-estradiol stimulated proliferation of the PE04 and PE06 but not the PE01 cells; 1 nM TCDD alone either did not affect or inhibited the growth of these cells and 1 nM TCDD significantly inhibited the 17beta-estradiol-indu ced proliferation of the PE04 and PE06 cells. Treatment of the PE04 ce lls with 1 nM 17beta-estradiol resulted in a time-dependent enhanced s ecretion of the M(r) 52,000 protein (procathepsin D) and, after 48 h, a 51 % increase in the secretion of this protein was observed. Cotreat ment of the PE04 cells with 0.1 or 1.0 nM TCDD completely inhibited th e 17beta-estradiol-induced secretion of the M(r) 52,000 protein. These data show that TCDD exhibits antiestrogenic activity in estrogen rece ptor-positive ovarian carcinoma cell lines; however, in the PE06 cells , there was no correlation between the effects of TCDD on the inductio n of CYP1A1 gene expression and the results of the gel shift assay (i. e., nonresponsiveness) versus the observed antiestrogenic activity.