Resveratrol and 3,3’-diindolylmethane differentially regulate aryl hydrocarbon receptor and estrogen receptor alpha to modulate diverse signalling pathways in MCF-7 human breast cancer cells

Abstract

Abstract Background Inhibitory crosstalk between estrogen receptor alpha (ERα) and aryl hydrocarbon receptor (AHR) regulates 17β-estradiol (E2)-dependent breast cancer cell signalling. ERα and AHR are ligand activated transcription factors that mediate the actions of E2 and pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), respectively. Like ERα, AHR binds many dietary compounds, including resveratrol (RES) and 3,3´diindolylmethane (DIM) often found in berries and cruciferous vegetables, respectively. RES activates ERα but inhibits AHR, whereas DIM activates ERα and AHR. Thus, dietary intake of RES and DIM will modulate both receptor activities. Here we used chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) and transcriptomics (RNA-seq) to study ERα and AHR crosstalk after treatment of MCF-7 human breast cancer cells with DIM, RES, E2 or TCDD alone or in combination. Methods and Results 1 h or 6 h ligand treated MCF-7 cells were profiled for ERα and AHR binding sites using ChIP-seq or gene expression changes using RNA-seq, respectively. E2 resulted in 866 differentially expressed genes (DEGs), 532 of which were also bound by ERα. DIM and RES resulted in 577 and 446 DEGs, respectively, with 278 of the RES and 393 of the DIM DEGs also bound by ERα. An estrogen response element (ERE) was enriched after treatments with all three ligands, while an AHR response element (AHRE) was also enriched in the DIM-ERα but not after E2-ERα bound sites. An ERE was enriched in E2 + TCDD and DIM AHR bound sites but not for the TCDD-AHR bound sites. We found that 90% of the DEGs closest to an AHR binding site after DIM or E2 + TCDD also had an ERE and 60% of coregulated genes were common to both treatments. Collectively, our data show that DIM activates ERα and AHR like that of E2 + TCDD, while RES activates ERα but inhibits AHR. Conclusion The dietary compounds DIM and RES differentially regulate ERα and AHR action and likely other signalling pathways, which need to be considered to properly interpret their cellular and biological responses. These data further highlight the complex crosstalk between ERa and AHR and suggest that when both receptors are activated ERa dominants causing the preferential recruitment of AHR to ERa target genes.