Thangapazham Rajesh L, Passi Neena, Maheshwari Radha K
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
Cancer Biol Ther. 2007 Dec;6(12):1938-43. doi: 10.4161/cbt.6.12.4974. Epub 2007 Sep 1.
Currently, there is no effective therapy for estrogen independent breast cancer. MDA-MB-231 is an estrogen receptor negative highly invasive human breast cancer cell line and has been used as a relevant model system to evaluate drugs with chemopreventive potential against highly invasive breast cancer phenotypes. Epidemiological studies though inconclusive have shown that consumption of Green Tea Polyphenols (GTP) reduces the incidence and progression of breast cancer. Green tea is an important source of antioxidants that may be useful for chemoprevention of cancer. Recently published preclinical study from our lab suggested that GTP and EGCG treatment inhibit proliferation and induce apoptosis of MDA-MB-231. In this study, we have evaluated apoptotic and anti-invasive activity of green tea polyphenols (GTP) and its principal constituent Epigallocatechin gallate (EGCG) in MDA-MB-231 human breast cancer cell line. In in vitro human breast cancer model, EGCG and GTP induced apoptosis and significantly decreased invasion of breast cancer cells. Western blotting of MDA-MB-231 cell lysates from EGCG and GTP treated and untreated control revealed an increase in bax, reduction in bcl2 and PARP cleavage. Quantitative fluorescence labeling resulted in a 24-28% reduction in invasion through matrigel by EGCG and 15-23% reduction by GTP in a dose dependent manner. Focussed microarray analysis and reverse transcriptase polymerase chain reaction and zymogram analysis revealed inhibition of MMP-9 expression by polyphenol treatment. Furthermore, AKT was found to be inhibited both at the RNA and protein level by polyphenol treatment. Moreover EGCG and GTP decreased AKT phosphorylation as found out by Western blotting for Phospho-AKT (Ser-473). beta-catenin level was found to be decreased both in cytoplasm and nucleus. For the first time we report the connection of beta-catenin and AKT modulation by GTP and EGCG as a possible mechanism for the induction of apoptosis in human breast cancer cells and also inhibition in their invasive capacity.
目前，对于雌激素非依赖性乳腺癌尚无有效的治疗方法。MDA-MB-231是一种雌激素受体阴性的高侵袭性人乳腺癌细胞系，已被用作相关模型系统，以评估具有化学预防潜力的药物对高侵袭性乳腺癌表型的作用。流行病学研究虽尚无定论，但已表明食用绿茶多酚（GTP）可降低乳腺癌的发病率和进展。绿茶是抗氧化剂的重要来源，可能对癌症的化学预防有用。我们实验室最近发表的临床前研究表明，GTP和表没食子儿茶素没食子酸酯（EGCG）处理可抑制MDA-MB-231的增殖并诱导其凋亡。在本研究中，我们评估了绿茶多酚（GTP）及其主要成分表没食子儿茶素没食子酸酯（EGCG）在MDA-MB-231人乳腺癌细胞系中的凋亡和抗侵袭活性。在体外人乳腺癌模型中，EGCG和GTP诱导凋亡并显著降低乳腺癌细胞的侵袭能力。对EGCG和GTP处理组及未处理对照组的MDA-MB-231细胞裂解物进行蛋白质免疫印迹分析，结果显示bax增加、bcl2减少以及PARP裂解。定量荧光标记显示，EGCG和GTP以剂量依赖方式使通过基质胶的侵袭减少24 - 28%和15 - 23%。聚焦微阵列分析、逆转录聚合酶链反应和酶谱分析显示多酚处理可抑制MMP-9表达。此外，发现多酚处理在RNA和蛋白质水平均抑制AKT。而且，通过磷酸化AKT（Ser-473）的蛋白质免疫印迹发现EGCG和GTP降低了AKT磷酸化。β-连环蛋白水平在细胞质和细胞核中均降低。我们首次报道GTP和EGCG对β-连环蛋白和AKT的调节作用，这可能是诱导人乳腺癌细胞凋亡并抑制其侵袭能力的一种机制。
