Genistein represses telomerase activity via both transcriptional and posttranslational mechanisms in human prostate cancer cells
Genistein represses telomerase activity via both transcriptional and posttranslational mechanisms in human prostate cancer cells
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DOI：
10.1158/0008-5472.can-05-2494
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发表时间：
2006-02-15
期刊：
影响因子：
11.2
通讯作者：
Banerjee, PP
中科院分区：
文献类型：
--
作者：
Jagadeesh, S;Kyo, S;Banerjee, PP
染料木黄酮是大豆中含量最丰富的一种黄酮类化合物，对多种癌细胞具有抗增殖作用，包括前列腺癌。然而，染料木黄酮的抗增殖作用的分子机制还不完全清楚。由于端粒酶的激活是细胞获得永生和增殖能力的关键，我们研究了染料木黄酮在前列腺癌细胞端粒酶活性调节中的作用。在这里，我们表明，染料木黄酮诱导的细胞增殖抑制与端粒酶活性的降低。通过逆转录PCR和hTERT启动子活性检测，我们发现染料木黄酮剂量依赖性地降低hTERT的表达和转录活性。使用各种缺失的hTERT启动子构建体，我们确定hTERT核心启动子足以观察染料木黄酮诱导的hTERT转录活性抑制。由于c-Myc参与hTERT的转录调节，因此检查了c-Myc表达。染料木黄酮处理后，c-Myc信息和蛋白质呈剂量依赖性减少。这些结果表明，金雀异黄素通过下调c-Myc表达抑制hTERT转录活性。然而，染料木黄酮诱导的hTERT转录活性的抑制并没有被hTERT启动子的c-Myc突变所阻断，这表明另外的因素参与了染料木黄酮依赖的端粒酶活性的抑制。有趣的是，我们观察到金雀异黄素下调Akt的活化，从而磷酸化hTERT并抑制其易位到细胞核。这些结果首次表明，金雀异黄素抑制前列腺癌细胞中的端粒酶活性，不仅通过抑制hTERT的转录活性通过c-Myc，但也通过翻译后修饰的hTERT通过Akt。
Genistein, the most abundant isoflavone present in soybean has antiproliferative effects on a variety of cancer cells, including prostate cancer. However, the molecular mechanism of antiproliferative effects of genistein is not entirely understood. Because the activation of telomerase is crucial for cells to gain immortality and proliferation ability, we examined the role of genistein in the regulation of telomerase activity in prostate cancer cells. Here, we show that genistein-induced inhibition in cell proliferation is associated with a reduction in telomerase activity. Using reverse transcriptase-PCR and hTERT promoter activity assays, we showed that genistein decreased hTERT expression and transcriptional activity dose-dependently. Using various deleted hTERT promoter constructs, we defined that the hTERT core promoter is enough to observe the genistein-induced repression of hTERT transcriptional activity. Because c-Myc is involved in transcriptional regulation of hTERT, c-Myc expression was examined. A dose-dependent decrease in c-Myc message and proteins was observed with genistein treatment. These results indicate that genistein represses hTERT transcriptional activity via the down-regulation of c-Myc expression. However, genistein-induced repression of hTERT transcriptional activity was not blocked by the mutation of c-Myc at the hTERT promoter, suggesting that additional factors are involved in genistein-dependent repression of telomerase activity. Interestingly, we observed that genistein down-regulates the activation of Akt thereby phosphorylation of hTERT and inhibits its translocation to the nucleus. These results show for the first time that genistein represses telomerase activity in prostate cancer cells not only by repressing hTERT transcriptional activity via c-Myc but also by posttranslational modification of hTERT via Akt.