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The gut microbiome has stolen the show when it comes to the recent explosion of research on the bacteria that thrive within us. But bacteria also live in a woman’s breast tissue-and the mix of those microbes may have an equally important effect on health, according to a new study in Applied and Environmental Microbiology. The results “suggest that microbes in the breast, even in low amounts, may be playing a role in breast cancer-increasing the risk in some cases and decreasing the risk in other cases,” says Gregor Reid, a professor of microbiology and immunology at Western University in Ontario and the study’s senior author.

最近有关能在人体内大量繁殖的细菌研究中,消化系菌群最为大家所关注。但据《应用与环境微生物学》新发布的一项研究,细菌也存活于女性的乳房组织中-而且这些微生物的混合会对健康产生同样重要的影响。研究结果“表明乳房中的微生物,即便在少量情况下,也会对乳腺癌造成一定影响-它们在不同情况下抑制或促进罹患乳腺癌的风险”,Gregor Reid如此说,他是西安大略大学微生物学与免疫学的教授,也是本研究的资深作者。

One in eight women in the U.S. are diagnosed with breast cancer during their lifetimes, but its origins remain unknown in most cases. Age, genetic predisposition and environmental changes are often implicated-and according to a growing body of research, bacteria may be one of those environmental factors. For instance, as early as the 1960s a number of studies have found that breast-feeding is associated with a lower risk of breast cancer, and more recent work suggests that this may be because breast milk supports the growth of beneficial microorganisms.

在美国,每八位女性中就有一位被诊断出乳腺癌,但多数病例的病因仍然是个谜。经常被提到的影响因素有年龄、基因倾向和环境变化-而且据一项身体生长的研究表明,环境因素的其中之一就是细菌。比如,早在19世纪60年代,一系列研究就已发现母乳喂养会降低乳腺癌的发病风险,而近期更深入的研究认为这与母乳促进有益微生物的生长有关。

Reid and his team decided to pursue this line of thought. They analyzed bacterial DNA found in breast tissue samples from 58 women who were undergoing lumpectomies or mastectomies for either benign or cancerous tumors, as well as from 23 healthy women who had undergone breast reductions or enhancements. They found that women with breast cancer had higher levels of some types of bacteria, including Enterobacteriaceae, Staphylococcus and Bacillus. Women without cancer had higher levels of other types, such as Lactococcus and Streptococcus.

Reid和他的团队决定顺着这条思路深入研究。他们找来58位因良性或恶性肿瘤而进行乳房或乳房肿瘤切除的女性,和23位进行了缩胸或隆胸手术的健康女性,对她们乳房组织样本的细菌DNA分别研究分析。结果表明患有乳腺癌的女性体内某些类型的细菌数量更多,包括肠杆菌、葡萄球菌和其他一些杆菌。而健康女性则具有更多其他类型的细菌,比如乳球菌和链球菌。

It isn’t surprising in and of itself that the breast harbors microbes, says immunologist Delphine Lee, who studies breast cancer at the John Wayne Cancer Institute in Santa Monica, Calif., and was not involved in the study. “The breast is exposed to the outside environment through the nipple and ductal system. Bacteria can also get in the tissue through skin wounds and other mechanisms,” she explains. “But what we’re not sure of yet is whether certain bacteria are found near breast tumors because they cause breast cancer or because they just thrive in the tumor environment.”

免疫学家Delphine Lee说,乳房自身及其内部存在微生物不足为奇。她在加州圣莫妮卡的John Wayne肿瘤研究所进行有关乳腺癌的研究,但并未参与此次研究。“乳头和导管系统使乳房暴露在外部环境中,皮肤创伤和其他一些人体机制也为细菌提供了进入乳房组织的渠道”,她补充道,“但我们仍不能确定的是,某些细菌是在乳房肿瘤附近发现的,这到底是因为它们引发了乳腺癌,还是仅仅因为它们能在肿块环境下大量繁殖。”

If certain bacteria do instigate cancer, how would they do so? Some Enterobacteriaceae and Staphylococcus microbes seem to cause DNA damage-a known route to the development of cancer. Other bacteria may trigger inflammation. The exact mechanisms must be probed in further animal studies, Reid says, but eventually he hopes researchers will be able to use a patient’s bacterial makeup as a biomarker for cancer screening or to develop probiotics for improving prognosis and treatment outcomes.

如果某些细菌真的能引发癌症,它们是怎样作用的?肠杆菌属和葡萄球菌属微生物似乎会损伤DNA,这是大家都知道的癌症形成原因。其它细菌可能会引发炎症。Reid说探寻其中的确切机理需要更深入的动物研究,但他希望科学家最终能将病人的细菌组合用作生物标志,进行防癌筛查,或是发明新的益生菌种来改善预知诊断和治疗的效果。