Study on clarification of unregulated gene expression to genome network by dioxin and related compounds using a human alveolar carcinoma cell line

芳烃受体(AhR)是一种配体激活的转录因子，介导2，3，7，8-四氯二苯并对二恶英(Dioxin)及其相关化合物的一系列毒性和生物效应。虽然AhR的生理配基尚未确定，但已有一些报道表明AhR不仅在异种代谢的调节中发挥重要作用，而且在维持体内平衡功能方面也发挥着重要作用。AHR配体β-萘黄酮能促进人肺泡癌细胞株A549细胞的增殖。与AHR拮抗剂α-萘黄酮联用后，这种增强作用消失。接下来，为了获得AhR调控细胞增殖的直接证据，我们分离了过表达AhR的克隆。这些克隆细胞的生长速度比对照细胞快，而且生长速度与t…成正比。更多的是AHR的量。细胞周期分析表明，AhR的过表达加速了细胞的生长，这很可能是由于M期晚期缩短到S期所致。对细胞周期调控基因表达谱的研究表明，AhR或AhR配体可诱导DP2、增殖细胞核抗原和RFC38的表达。DP2是一种转录因子，与E2F形成功能性二聚体，并调节与DNA合成有关的几个基因的表达。有趣的是，增殖细胞核抗原和RFC38都是E2F和DP复合体的靶基因。在AhR过表达的细胞和AhR激动剂处理的细胞中，E2F活性均显著增加，提示AhR激活的E2F/DP2可能诱导了增殖细胞核抗原和RFC38的表达以及随后的DNA合成。RNAi下调ARNT的表达可减弱AhR对A549细胞增殖的影响。因此，我们得出结论，AhR可能与ARNT合作，激活了A549细胞的DNA合成和随后的细胞增殖。较少

The arylhydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a spectrum of toxic and biological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) and related compounds. Although the physiological ligand for the AhR has not yet been identified, several reports have suggested that the AhR may play important roles not only in the regulation of xenobiotic metabolism but also in the maintenance of homeostatic functions.In this study, we first investigated the role of AhR on cell proliferation. The cell proliferation of A549 cells, a human alveolar carcinoma cell line, was enhanced by the treatment with the AhR-ligand, β -naphthoflavone. The enhancement effect was disappeared by the co-treatment with the AhR-antagonist, α-naphthoflavone. Next, in order to obtain direct evidence that the AhR regulates cell proliferation, we isolated the clones that overexpress the AhR. These clones grow faster than control cells, and the rate of growth is proportional to t … More he amount of the AhR. Cell cycle analysis revealed that the acceleration of cell growth by overexpression of the AhR is most probably due to shortening of the late M to S phases. Studies on the expression profiles of cell cycle regulators showed that the AhR or AhR ligand induces the expression of DP2, PCNA, and RFC38. DP2 is the transcription factor that forms the functional dimer with E2F and regulates the expression of several genes involved in DNA synthesis. Interestingly, both PCNA and RFC38 are target genes of E2F and the DP complex. E2F activity was substantially increased in both the AhR-overexpressing cells and the AhR-agonist treated cells, suggesting that AhR-activated E2F/DP2 may induce the expression of PCNA and RFC38 and subsequent DNA synthesis. Down-regulation of the expression of the Arnt by RNAi diminished the effects of the AhR on the cell proliferation of the A549 cells. Consequently, we conclude that the AhR, presumably in collaboration with the Arnt, activates the DNA synthesis and the subsequent cell proliferation in A549 cells. Less