Wenzel U, Kuntz S, Brendel M D, Daniel H
Institute of Nutritional Sciences, University of Giessen, Germany.
Cancer Res. 2000 Jul 15;60(14):3823-31.
Flavonoids are polyphenolic compounds that occur ubiquitously in plants. They are discussed to represent cancer preventive food components in a human diet that is rich in fruits and vegetables. To understand the molecular basis of the putative anticancer activity of flavonoids, we investigated whether and how the core structure of the flavones, 2-phenyl-4H-1-benzopyran-4-one (flavone) affects proliferation, differentiation, and apoptosis in HT-29 human colon cancer cells. Moreover, the effects of flavone in transformed epithelial cells were compared with those obtained in nontransformed primary mouse colonocytes. Proliferation, differentiation, and apoptosis in transformed as well as nontransformed colon cells were measured by fluorescence-based techniques. Apoptosis was also determined by changes in membrane permeability, FACScan analysis, and detection of DNA fragmentation. Semiquantitative reverse transcription PCR was performed to assess the effects of flavone on transcript levels. Flavone was found to reduce cell proliferation in HT-29 cells with an EC(50) value of 54.8 +/- 1.3 microM and to potently induce differentiation as well as apoptosis. The flavonoid proved to be a stronger apoptosis inducer than the clinically established antitumor agent camptothecin. The effects of flavone in HT-29 cells were associated with changed mRNA levels of cell-cycle- and apoptosis-related genes including cyclooxygenase-2 (COX-2), nuclear transcription factor kappaB (NF-kappaB), and bcl-X(L). Moreover, flavone, but not camptothecin, displayed a high selectivity for the induction of apoptosis and of growth inhibition only in the transformed colonocytes. In conclusion, the plant polyphenol flavone induces effectively programmed cell death, differentiation, and growth inhibition in transformed colonocytes by acting at the mRNA levels of genes involved in these processes. Because these genes play a crucial role in colon carcinogenesis, flavone may prove to be a potent new cytostatic compound with improved selectivity toward transformed cells.
黄酮类化合物是普遍存在于植物中的多酚类化合物。它们被认为是人类富含水果和蔬菜饮食中具有防癌作用的食物成分。为了了解黄酮类化合物假定的抗癌活性的分子基础，我们研究了黄酮（2-苯基-4H-1-苯并吡喃-4-酮）的核心结构是否以及如何影响HT-29人结肠癌细胞的增殖、分化和凋亡。此外，还将黄酮对转化上皮细胞的作用与未转化的原代小鼠结肠细胞进行了比较。通过基于荧光的技术检测转化和未转化结肠细胞中的增殖、分化和凋亡情况。还通过膜通透性变化、流式细胞仪分析和DNA片段检测来确定凋亡。进行半定量逆转录PCR以评估黄酮对转录水平的影响。发现黄酮可降低HT-29细胞的增殖，其半数有效浓度（EC50）值为54.8±1.3微摩尔，并能有效诱导分化和凋亡。事实证明，这种黄酮类化合物是比临床常用抗肿瘤药物喜树碱更强的凋亡诱导剂。黄酮在HT-29细胞中的作用与细胞周期和凋亡相关基因（包括环氧合酶-2（COX-2）、核转录因子κB（NF-κB）和bcl-XL）的mRNA水平变化有关。此外，黄酮仅在转化的结肠细胞中对凋亡诱导和生长抑制具有高选择性，而喜树碱则无此特性。总之，植物多酚黄酮通过作用于参与这些过程的基因的mRNA水平，有效诱导转化结肠细胞的程序性细胞死亡、分化和生长抑制。由于这些基因在结肠癌发生中起关键作用，黄酮可能被证明是一种对转化细胞具有更高选择性的新型有效细胞生长抑制剂。
