Department of Biosciences and Nutrition, Karolinska Institutet, Novum, 141 57, Huddinge, Sweden.
Breast Cancer Res Treat. 2010 Apr;120(2):317-26. doi: 10.1007/s10549-009-0381-6. Epub 2009 Mar 26.
We have previously shown that the anti-proliferative effect of retinoic acid in human breast cancer cell line MCF-7 is dependent on HES-1 expression. Here we show that retinoic acid induces HES-1 expression via upregulation of transcription factor SOX9. By expressing a dominant negative form of SOX9, disrupting endogenous SOX9 activity, the retinoic acid-induced HES-1 mRNA expression was inhibited. We found an enhancer regulating HES-1 expression: two SOX9 binding sites upstream of the HES-1 gene that were capable of binding SOX9 in vitro. By performing chromatin immunoprecipitation, we showed that SOX9 binding to the HES-1 enhancer was induced by retinoic acid in vivo. In reporter assays, transfection of a SOX9 expression plasmid increased the activity of the HES-1 enhancer. The enhancer responded to retinoic acid; furthermore, the expression of a dominant negative SOX9 abolished this response. Taken together, we present here a novel transcriptional mechanism in regulating hormone-dependent cancer cell proliferation.
我们之前已经证明，维甲酸在人乳腺癌 MCF-7 细胞系中的抗增殖作用依赖于 HES-1 的表达。在这里，我们表明维甲酸通过上调转录因子 SOX9 诱导 HES-1 的表达。通过表达 SOX9 的显性负形式，破坏内源性 SOX9 活性，抑制维甲酸诱导的 HES-1 mRNA 表达。我们发现了一个调节 HES-1 表达的增强子：HES-1 基因上游的两个 SOX9 结合位点，能够在体外与 SOX9 结合。通过进行染色质免疫沉淀，我们表明 SOX9 在体内与 HES-1 增强子的结合是由维甲酸诱导的。在报告基因实验中，转染 SOX9 表达质粒增加了 HES-1 增强子的活性。该增强子对维甲酸有反应；此外，显性负 SOX9 的表达消除了这种反应。综上所述，我们在这里提出了一种新的转录机制，用于调节激素依赖性癌细胞增殖。
