茶是人们最喜爱的饮料之一,全世界的饮茶量仅次于饮水量而居所有饮料消费的第二位.流行病学研究表明,某些肿瘤的发生与茶叶的消费显负相关.茶及其主要成分茶多酚不仅具有防癌作用,而且对体内外的肿瘤细胞具有直接杀伤作用,但其抗癌机制尚未完全明了.研究发现,许多天然植物成分能诱导肿瘤细胞凋亡,并能使肿瘤细胞发生细胞周期阻滞,抑制肿瘤细胞增殖.因此,茶提取物或茶多酚的抗癌作用可能也是通过诱导肿瘤细胞凋亡,影响细胞的生长周期来实现的. 

目的
    研究茶多酚诱导肺癌细胞凋亡的作用及其对细胞周期的阻滞作用. 

方法
    体外培养人肺腺癌SPC-A1细胞,取对数生长期细胞,调整细胞浓度至10~5/ml,接种至培养板继续培养24h,分对照组及茶多酚药物组(茶多酚终浓度为50μg/ml、100μg/ml、150μg/ml、200μg/ml、250μg/ml、300μg/ml),加药后继续培养12h、24h及36h,应用MTT法、琼脂糖凝胶电泳、透射电镜及流式细胞仪观察茶多酚诱导细胞凋亡的作用及阻滞细胞周期的作用. 

结果
    MTT法显示茶多酚可抑制肺癌细胞的增殖活性,其抑制作用随时间的延长而增强,以36h抑制作用最强.在浓度50μg/ml～150μg/ml范围内,抑制作用随浓度增高而增强；当浓度大于150μg/ml时,抑制作用随浓度增高反而减弱.琼脂糖凝胶电泳显示特征性的梯状条带,透射电镜可见凋亡细胞的形态学改变,线粒体空泡化、核凝聚、核固缩.流式细胞术发现茶多酚可使肺癌细胞阻滞于G_1期,以24h、150μg/ml阻滞作用最强(P＜0.05). 结论 茶多酚可诱导人肺癌SPC-A1细胞的凋亡,并使细胞周期阻滞于G_1期.
    Background Tea, the most popular beverage worldwide, is consumed only second to water. Epidemilogic studies have suggested that drinking green tea is negatively correlated with cancergenesis. Besides their cancer-preventive effects, green tea and its main component tea polyphenols also have direct anticancer effects both in vivo and in vitro. But the underlying mechanisms are not completely understood. It is well known that many natural products inhibit tumor cell proliferation by inducing apoptosis and blocking cell cycle. Therefor, It is reasonable that tea polyphenols inhibit tumor growth by the induction of apoptosis.Objective To evaluate the effects of tea polyphenols on the induction of apoptosis and blockage of cell cycle.Methods SPC-A1 cells were divided into seven groups after 24-hour culture at the concentration of 105/ml, that is control group and six treatment groups. The latter were administered green tea polyphenols at concentration of 50μg/ml, 100μg/ml, 150μg/ml, 200μg/ml, 250μg/ml, 300μg/ml respectively. Inhibition of SPC-A1 cell growth is observed by MTT method and flow cytimetry. Apoptosis is detected by gel electrophoresis and transmissional electron microscope. The datas were collected at the time of 12h, 24h and 36h respectively after treatment.Results The proliferation of SPC-A1 were significantly inhibited by green tea polyphenols and the inhibitionrate was time-dependent (12h-36h) and concentration-dependent (50 g/ml-150 g/ml). Its inhibitory effect decreased when the concentration exceeds 150 g/ml. "DNA ladder" was viewed on agarose gel. Typical nuclear condensation was observed by tranmissional electron microscope. SPC-A1 cells were blocked in G1 phaes. The highest G1 peak was detected at the concentration of 150 g/ml after 24h (P<0. 05).Conclusion Green tea polyphenols inhibit tumor cell proliferation by inducing cancer cell apoptosis and blocking cell cycle.