Joung Youn-Hee, Lim Eun-Joung, Kim Mi-Sun, Lim So Dug, Yoon So-Young, Lim Young Chang, Yoo Young Bum, Ye Sang-Kyu, Park Taekyu, Chung Ill-Min, Bae Ki-Yeol, Yang Young Mok
Department of Pathology, School of Medicine, and Bio-Food and Drug Research Center, Konkuk University, Chungju City 380-701, Korea.
Int J Oncol. 2008 Sep;33(3):477-84.
We have shown previously that hypoxia activates the cyclin D1 promoter via the Jak2/STAT5b pathway in breast cancer cells. Most solid tumors contain hypoxic components and overexpression of cyclin D1. The purpose of the present study was to investigate the molecular mechanism by which momilactone B exerts its inhibitory effects on breast cancer cells. Momilactone B, extracted from Korean rice hulls, suppressed hypoxia-induced increases in phospho-STAT5, STAT5b, cyclin D1, and cdk4 protein levels in human breast cancer cells. STAT5b expression was inhibited by siRNA experiments leading to decreased cyclin D1. The effects of momilactone B on cell growth and apoptosis-related gene expression were investigated in breast cancer cells under hypoxic conditions (2% O2). Bax and p21 expression was found to be up-regulated, whereas ppRb and bcl-2 were down-regulated in momilactone B-treated cells under hypoxic conditions. However, the p53 protein level did not change. Flow cytometry with Annexin-FITC staining showed that the number of apoptotic cells increased in hypoxic cells treated with momilactone B compared with untreated hypoxic cells. Furthermore, caspase activity increased upon treatment with momilactone B under hypoxic conditions. These results indicate that momilactone B inhibits the growth of breast cancer cells, regulates the expression of apoptosis-related genes, and induces apoptosis through STAT5b and a caspase-3 dependent pathway. We suggest that momilactone B accelerates hypoxia-induced apoptosis of human breast cancer cells through STAT5b, and may represent an effective chemopreventive or therapeutic agent against breast cancer.
我们之前已经表明，缺氧通过Jak2/STAT5b途径激活乳腺癌细胞中的细胞周期蛋白D1启动子。大多数实体瘤都含有缺氧成分且细胞周期蛋白D1过表达。本研究的目的是探讨茉莉内酯B对乳腺癌细胞发挥抑制作用的分子机制。从韩国稻壳中提取的茉莉内酯B可抑制人乳腺癌细胞中缺氧诱导的磷酸化STAT5、STAT5b、细胞周期蛋白D1和细胞周期蛋白依赖性激酶4（cdk4）蛋白水平的升高。小干扰RNA（siRNA）实验抑制了STAT5b的表达，导致细胞周期蛋白D1减少。在缺氧条件（2%氧气）下，研究了茉莉内酯B对乳腺癌细胞生长和凋亡相关基因表达的影响。发现在缺氧条件下用茉莉内酯B处理的细胞中，促凋亡蛋白Bax和p21的表达上调，而磷酸化视网膜母细胞瘤蛋白（ppRb）和抗凋亡蛋白bcl-2的表达下调。然而，p53蛋白水平没有变化。用膜联蛋白-FITC染色的流式细胞术显示，与未处理的缺氧细胞相比，用茉莉内酯B处理的缺氧细胞中凋亡细胞的数量增加。此外，在缺氧条件下用茉莉内酯B处理后，半胱天冬酶活性增加。这些结果表明，茉莉内酯B抑制乳腺癌细胞的生长，调节凋亡相关基因的表达，并通过STAT5b和半胱天冬酶-3依赖性途径诱导凋亡。我们认为，茉莉内酯B通过STAT5b加速缺氧诱导的人乳腺癌细胞凋亡，可能是一种有效的乳腺癌化学预防或治疗剂。
