Dietary ligands diindolylmethane and resveratrol result in diverse ERα signaling not seen after E2 and a subset of diindolylmethane mediated signaling needs concurrent AHR activation.

Inhibitory crosstalk between estrogen receptor alpha (ER alpha ) and aryl hydrocarbon receptor (AHR) regulates 17-estradiol (E2)-dependent breast cancer cell signaling. ER alpha and AHR are transcription factors activated by E2 and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), respectively. Dietary ligands resveratrol (RES) and 3,30diindolylmethane (DIM) also activate ER alpha while only DIM activates AHR and RES represses it. DIM and RES are reported to have anti-cancer and antiinflammatory properties. Studies with genome-wide targets and AHR- and ER alpha-regulated genes after DIM and RES are unknown. We used chromatin immunoprecipitation with high-throughput sequencing and transcriptomics to study ER alpha as well as AHR coregulation in MCF-7 human breast cancer cells treated with DIM, RES, E2, or TCDD alone or E2+TCDD for 1 and 6 h, respectively. ER alpha bound sites after being DIM enriched for the AHR motif but not after E2 or RES while AHR bound sites after being DIM and E2+TCDD enriched for the ERE motif but not after TCDD. More than 90% of the differentially expressed genes closest to an AHR binding site after DIM or E2+TCDD also had an ER alpha site, and 60% of the coregulated genes between DIM and E2+TCDD were common. Collectively, our data show that RES and DIM differentially regulate multiple transcriptomic targets via ER alpha and ER alpha /AHR coactivity, respectively, which need to be considered to properly interpret their cellular and biological responses. These novel data also suggest that, when both receptors are activated, ER alpha  dominates with preferential recruitment of AHR to ER alpha  target genes. MCF-7 human breast cancer cells treated with DIM, RES, E2, or TCDD alone or E2+TCDD for 1 and 6 h and assayed for ERa and AHR binding via ChIP sequencing and gene expresison changes via RNA sequencing respectively.

雌激素受体α（estrogen receptor alpha, ERα）与芳香烃受体（aryl hydrocarbon receptor, AHR）之间的抑制性交叉调控，可调控17β-雌二醇（17β-estradiol, E2）依赖的乳腺癌细胞信号通路。ERα与AHR分别为E2与2,3,7,8-四氯二苯并对二噁英（2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD）所激活的转录因子。膳食配体白藜芦醇（resveratrol, RES）与3,3'-二吲哚甲烷（3,3'-diindolylmethane, DIM）同样可激活ERα；其中仅DIM能够激活AHR，而RES则可抑制AHR的活性。已有研究证实DIM与RES均具备抗癌与抗炎特性，但目前尚无针对DIM与RES处理后全基因组靶点以及AHR、ERα调控基因的相关研究。本研究采用染色质免疫共沉淀测序（chromatin immunoprecipitation with high-throughput sequencing, ChIP-seq）与转录组学技术，对经单独DIM、RES、E2或TCDD，以及E2+TCDD处理1小时与6小时的MCF-7人乳腺癌细胞进行分析，以探究ERα与AHR的共调控机制。结果显示：DIM处理后，ERα结合位点显著富集AHR基序，而E2或RES处理后未观察到该富集现象；DIM与E2+TCDD处理后，AHR结合位点显著富集雌激素反应元件（estrogen response element, ERE）基序，而TCDD单独处理后则无此富集。在DIM或E2+TCDD处理后，靠近AHR结合位点的差异表达基因中，超过90%同时存在ERα结合位点；且DIM与E2+TCDD的共调控基因中，有60%为二者共有。综合分析本研究数据可知，RES与DIM可分别通过ERα以及ERα/AHR协同活性，差异化调控多组转录组靶点，在阐释二者的细胞与生物学效应时需充分考虑该调控机制。本研究的新颖数据同时提示，当两种受体均被激活时，ERα将占据主导地位，优先招募AHR至ERα的靶基因区域。本数据集的样本为经单独DIM、RES、E2或TCDD，以及E2+TCDD处理1小时与6小时的MCF-7人乳腺癌细胞，分别通过ChIP测序检测ERα与AHR的结合情况，并通过RNA测序分析基因表达变化。