TY - JOUR
T1 - Aryl hydrocarbon receptor gene silencing with small inhibitory RNA differentially modulates Ah-responsiveness in MCF-7 and HepG2 cancer cells
AU - Abdelrahim, Maen
AU - Smith, Roger
AU - Safe, Stephen
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2003/6/1
Y1 - 2003/6/1
N2 - Sequence-specific small interfering RNA (siRNA) duplexes can be used for gene silencing in mammalian cells and as mechanistic probes for determining gene function. Transfection of siRNAs for the aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) mRNAs in MCF-7 breast cancer cells resulted in a 60 to 80% decrease in levels of AhR and ARNT proteins in whole-cell extracts and decreased binding of nuclear extracts to 32P-labeled dioxin-responsive element. siRNA for the AhR also decreased 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 protein, CYP1A1-dependent activity, and luciferase activity in cells transfected with an Ahresponsive construct. 17β-Estradiol (E2) induces proliferation of MCF-7 cells through enhanced G0/G1 → S phase progression, and this response is inhibited in cells cotreated with E2 plus TCDD. The effects of TCDD on E2-induced cell-cycle progress were partially blocked in MCF-7 cells transfected with siRNA for AhR. The results also indicated that siRNA-dependent decreases in AhR protein in MCF-7 cells were accompanied by increased G0/G1 → S phase progression, suggesting a growth-inhibitory role for the "endogenous" AhR. Surprisingly, TCDD alone induced G0/G1 → S phase progression and exhibited estrogenic activity in MCF-7 cells transfected with siRNA for the AhR. In contrast, degradation of the AhR in HepG2 liver cancer cells resulted in decreased G0/G1 → S phase progression, and this was accompanied by decreased expression of cyclin Dl, cyclin E, cyclin-dependent kinase 2 (cdk2), and cdk4. In the absence of ligand, the AhR exhibits growth-inhibitory (MCF-7) and growth-promoting (HepG2) activity that is cell context-dependent.
AB - Sequence-specific small interfering RNA (siRNA) duplexes can be used for gene silencing in mammalian cells and as mechanistic probes for determining gene function. Transfection of siRNAs for the aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) mRNAs in MCF-7 breast cancer cells resulted in a 60 to 80% decrease in levels of AhR and ARNT proteins in whole-cell extracts and decreased binding of nuclear extracts to 32P-labeled dioxin-responsive element. siRNA for the AhR also decreased 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 protein, CYP1A1-dependent activity, and luciferase activity in cells transfected with an Ahresponsive construct. 17β-Estradiol (E2) induces proliferation of MCF-7 cells through enhanced G0/G1 → S phase progression, and this response is inhibited in cells cotreated with E2 plus TCDD. The effects of TCDD on E2-induced cell-cycle progress were partially blocked in MCF-7 cells transfected with siRNA for AhR. The results also indicated that siRNA-dependent decreases in AhR protein in MCF-7 cells were accompanied by increased G0/G1 → S phase progression, suggesting a growth-inhibitory role for the "endogenous" AhR. Surprisingly, TCDD alone induced G0/G1 → S phase progression and exhibited estrogenic activity in MCF-7 cells transfected with siRNA for the AhR. In contrast, degradation of the AhR in HepG2 liver cancer cells resulted in decreased G0/G1 → S phase progression, and this was accompanied by decreased expression of cyclin Dl, cyclin E, cyclin-dependent kinase 2 (cdk2), and cdk4. In the absence of ligand, the AhR exhibits growth-inhibitory (MCF-7) and growth-promoting (HepG2) activity that is cell context-dependent.
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U2 - 10.1124/mol.63.6.1373
DO - 10.1124/mol.63.6.1373
M3 - Article
C2 - 12761348
AN - SCOPUS:0037764668
VL - 63
SP - 1373
EP - 1381
JO - Molecular Pharmacology
JF - Molecular Pharmacology
SN - 0026-895X
IS - 6
ER -