Hartman Johan, Müller Patrick, Foster James S, Wimalasena Jay, Gustafsson Jan-Ake, Ström Anders
Center for Biotechnology, Department of BioSciences, Karolinska Institutet, Novum, S-141 57 Huddinge Sweden.
Oncogene. 2004 Nov 18;23(54):8826-33. doi: 10.1038/sj.onc.1208139.
We have previously shown that expression of the transcription factor HES-1 is required for the growth-inhibitory effect of all-trans retinoic acid on MCF-7 cells. In this study, we have used T47D cells with tetracyclin-regulated expression of wild-type or a dominant-negative form of HES-1. Expression of HES-1 in T47D cells inhibited G1/S-phase transition and activation of Cdk2 elicited by estrogen. Estrogen treatment of T47D cells caused increased expression of E2F-1, and this expression was inhibited by cotreatment with all-trans retinoic acid. We show that the effect is mediated through HES-1, which directly downregulates E2F-1 expression through a CACGAG-site within the E2F-1 promoter. Furthermore, proliferation caused by heregulin-beta1 treatment of T47D cells was inhibited by all-trans retinoic acid and this effect was mediated by HES-1. Interestingly, heregulin-beta1-mediated upregulation of E2F-1 expression was directly inhibited by HES-1 through the same CACGAG-site as seen with estrogen-stimulated induction. In addition, we found that two important downstream target genes of estrogen and heregulin-beta1 that are regulated through E2F-1, cyclin E and NPAT, were both regulated in a similar fashion by all-trans retinoic acid, and these effects were antagonized by dominant-negative HES-1. These findings establish that HES-1 inhibits both estrogen- and heregulin-beta1-stimulated growth of breast cancer cells, and further suggest that growth inhibition induced in these cells by all-trans retinoic acid occurs via HES-1-mediated downregulation of E2F-1 expression.
我们之前已经表明，转录因子HES-1的表达是全反式维甲酸对MCF-7细胞生长抑制作用所必需的。在本研究中，我们使用了四环素调控野生型或显性负性形式的HES-1表达的T47D细胞。T47D细胞中HES-1的表达抑制了雌激素引发的G1/S期转换和Cdk2的激活。雌激素处理T47D细胞导致E2F-1表达增加，而全反式维甲酸共处理可抑制这种表达。我们表明这种作用是通过HES-1介导的，HES-1通过E2F-1启动子内的一个CACGAG位点直接下调E2F-1的表达。此外，全反式维甲酸抑制了这里调节素β1处理T47D细胞所引起的增殖，且这种作用由HES-1介导。有趣的是，HES-1通过与雌激素刺激诱导相同的CACGAG位点直接抑制这里调节素β1介导的E2F-1表达上调。此外，我们发现雌激素和这里调节素β1通过E2F-1调控的两个重要下游靶基因，细胞周期蛋白E和NPAT，均以类似方式受到全反式维甲酸的调控，且这些作用被显性负性HES-1拮抗。这些发现证实HES-1抑制雌激素和这里调节素β1刺激的乳腺癌细胞生长，并进一步表明全反式维甲酸在这些细胞中诱导的生长抑制是通过HES-1介导的E2F-1表达下调发生的。
