绿茶成分儿茶素或可杀死口腔癌细胞

宾夕法尼亚州立大学食品科学家通过研究说，绿茶中的一种化合物可能会引发一个周期反应,这个反应过程中杀死口腔癌细胞的同时可保留健康细胞。研究可能会发现一种治疗口腔癌以及其他类型癌症的方法。

此前的研究发现,绿茶中含有儿茶素没食子酸酯化合物,该化合物可以杀死口腔癌细胞而不损害正常细胞,但研究人员尚不清楚该化合物杀死癌细胞的原因,Joshua Lambert说，目前的研究表明儿茶素可能引发线粒体内反应而导致细胞死亡。

“儿茶素可以破坏线粒体,线粒体遭破坏会形成一个可造成更大的破坏的恶性循环,直到所有细胞经历细胞程序性死亡,”Lambert说。“儿茶素可引起肿瘤细胞活性氧的形成,通过制造更多的活性氧来破坏线粒体和线粒体应答反应。”

随着这线粒体持续死亡,癌细胞也会降低抗氧化基因的表达,从而进一步降低其防御功能。“关掉它保护机制的同时儿茶素可引起氧化应激反应”Lambert说。据研究人员介绍儿茶素并未引起正常细胞抗击反应。事实上,它似乎增加了细胞的自身保护功能。

研究人员研究了正常人类口腔细胞与人类口腔癌症细胞，以鉴定儿茶素是如何不同的影响肿瘤细胞和正常细胞。他们在培养皿中培养了正常细胞和肿瘤细胞,然后用儿茶素作用于它们,大量多酚存在于绿茶中,在人类咀嚼绿茶口香糖之后大量的多酚浓聚物就存在于唾液中。在不同时期,研究人员将收集细胞并用来检查氧化应激和抗氧化反应的标记。

Lambert说下一步是研究动物机制。如果这些测试和人体试验获得成功,研究人员然后希望创建一种和目前治疗一样有效的没有副作用的抗癌治疗方法。

“化疗药物存在很多问题，尤其是早期化疗药物,它们只是有快速分裂细胞的作用,所以癌症细胞在迅速分裂,而你的毛囊细胞在迅速分裂,你的肠道细胞也在迅速分裂,所以化疗药物有很多的副作用,”Lambert说。“但你在喝绿茶的时候却没有这些副作用。”（转化医学网360zhyx.com）

本文系转化医学网原创编译整理，如需转载，请联系info@360zhyx.com。

附原文：A compound found in green tea may trigger a cycle that kills oral cancer cells while leaving healthy cells alone, according to Penn State food scientists. The research could lead to treatments for oral cancer, as well as other types of cancer.

Earlier studies had shown that epigallocatechin-3-gallate—EGCG—a compound found in green tea, killed oral cancer cells without harming normal cells, but researchers did not understand the reasons for its ability to target the cancer cells, said Joshua Lambert, associate professor of food science and co-director of Penn State's Center for Plant and Mushroom Foods for Health. The current study shows that EGCG may trigger a process in the mitochondria that leads to cell death.

"EGCG is doing something to damage the mitochondria and that mitochondrial damage sets up a cycle causing more damage and it spirals out, until the cell undergoes programmed cell death," said Lambert. "It looks like EGCG causes the formation of reactive oxygen species in cancer cells, which damages the mitochondria, and the mitochondria responds by making more reactive oxygen species."

As this mitochondrial demise continues, the cancer cell also reduces the expression of anti-oxidant genes, further lowering its defenses.

"So, it's turning off its mechanism of protection at the same time that EGCG is causing this oxidative stress," Lambert added.

The EGCG did not cause this reaction in normal cells. In fact, it appeared to increase the protective capabilities of the cell, according to the researchers, who report their findings in the online issue of Molecular Nutrition and Food Research.

The researchers studied normal human oral cells side-by-side with human oral cancer cells to determine how EGCG was affecting cancer cells differently than normal cells. They grew the normal and cancer cells on petri dishes and then exposed them to EGCG, the major polyphenol found in green tea, at concentrations typically found in the saliva after chewing green-tea chewing gum. At various times, the researchers would collect the cells and check for oxidative stress and signs of antioxidant response.

He said the next step would be to study the mechanism in animals. If those tests and human trials are successful, the researchers then hope to create anti-cancer treatments that are as effective as current treatments without the harmful side effects.

"The problem with a lot of chemotherapy drugs—especially early chemotherapy drugs—is that they really just target rapidly dividing cells, so cancer divides rapidly, but so do cells in your hair follicles and cells in your intestines, so you have a lot of side effects," said Lambert. "But you don't see these sorts of side effects with green tea consumption."