文章来源:未知 文章作者:meng 发布时间:2010-05-14 02:46 字体: [ ]  进入论坛

It is well established that exposure to ionizing radiation(电离辐射) can result in mutations or other genetic1 damage that cause cells to turn cancerous. Now a new study led by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has revealed another way in which radiation can promote cancer development. Working with cultures of human breast cells, the researchers discovered that radiation exposure can alter the environment surrounding the cells so that future cells are more likely to become cancerous. "Our work shows that radiation can change the microenvironment(小环境,微环境) of breast cells, and this in turn can allow the growth of abnormal cells with a long-lived phenotype(显型,表型) that has a much greater potential to be cancerous," says Paul Yaswen, a cell biologist and breast cancer research specialist with Berkeley Lab's Life Sciences Division.

A cell's phenotype is its full complement2 of observable(觉察得到的) physical or biochemical characteristics. Different cells can have phenotypes that look dramatically different or exhibit radically3 different behavior even though their genetic makeup4 (genotype) is identical. Signals from outside the cell can alter a cell's phenotype by regulating (or de-regulating) the cell's use of its genes5. Studies have shown that if a cell develops a pre-cancerous phenotype, it can pass on these "epigenetic(外生的,后生的) " changes to its daughters, just as it can pass on genetic mutations.

"Many in the cancer research community, especially radiobiologists, have been slow to acknowledge and incorporate in their work the idea that cells in human tissues are not independent entities6, but are highly communicative with each other and with their microenvironment," Yaswen says. "We provide new evidence that potential cancer agents and their effects must be evaluated at a systems level."

Yaswen is the corresponding author of a paper describing this study that appears in the on-line journal Breast Cancer Research, titled "Promotion7 of variant8 human mammary(乳房的,乳腺的) epithelial cell(上皮细胞) outgrowth by ionizing radiation: an agent-based model supported by in vitro studies." Co-authoring the paper were Rituparna Mukhopadhyay, Sylvain Costes, Alexey Bazarov, William Hines and Mary Helen Barcellos-Hoff.

"The work we did was performed with non-lethal but fairly substantial doses of radiation, unlike what a woman would be exposed to during a routine mammogram(乳房X线照片) ," says Yaswen, who is also a member of the Bay Area Breast Cancer and the Environment Research Center. "However, the levels of radiation involved in other procedures, such as CT scans or radiotherapy, do start to approach the levels used in our experiments and could represent sources of concern."

For their study, Yaswen and his collaborators worked with human mammary epithelial cells (HMECs), the cells that line breast ducts, where most breast cancers begin. In a culture dish, the vast majority of breast cells display a phenotype that allows them to divide between five and 20 times before becoming senescent(衰老的) . However, also present are rare variant HMECs, which display a phenotype that allows them to continue dividing for many weeks in culture. This vHMEC phenotype arises spontaneously and is much more susceptible9 to malignancy(恶意,恶性) because it lacks a tumor-suppressing protein called p16.

To test the effects of radiation on cellular10 environment and subsequent cell behavior, the research team grew sets of HMECs from normal breast tissue in culture dishes for about a week, then exposed each set to a single treatment of a low-to-moderate dose of radiation. They then compared the irradiated sets to sets of breast cells that were not irradiated. Four to six weeks after the radiation treatments, most of the cells in both the irradiated and unirradiated sets had permanently11 stopped dividing.

"However, the daughters of breast cells exposed to radiation formed larger, more numerous patches of cells with the vHMEC phenotype than did the daughters of the unirradiated cells," Yaswen says. "An agent-based model developed by Sylvain Costes and Mary Helen Barcellos-Hoff suggests that the radiation increased the rate at which short-lived cells became senescent."

In a culture dish, breast cells will only divide and grow so long as there is room for daughter cells to spread out. When the dish becomes full, the cells stop dividing. By promoting premature12 senescence in the normal HMEC, the radiation treatments accelerated the outgrowth of the vHMECs.

"Radiation exposure did not directly induce(引诱) new vHMECs and the effect was not dose-dependent in the dose range we investigated," Yaswen says. "However, by getting normal cells to prematurely13 age and stop dividing, the radiation exposure created space for epigenetically altered cells that would otherwise have been filled by normal cells. In other words, the radiation promoted the growth of pre-cancerous cells by making the environment that surrounded the cells more hospitable14(殷勤的,舒适的) to their continued growth."


1 genetic PgIxp     
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
2 complement ZbTyZ     
  • The two suggestions complement each other.这两条建议相互补充。
  • They oppose each other also complement each other.它们相辅相成。
3 radically ITQxu     
  • I think we may have to rethink our policies fairly radically. 我认为我们可能要对我们的政策进行根本的反思。
  • The health service must be radically reformed. 公共医疗卫生服务必须进行彻底改革。
4 makeup 4AXxO     
  • Those who failed the exam take a makeup exam.这次考试不及格的人必须参加补考。
  • Do you think her beauty could makeup for her stupidity?你认为她的美丽能弥补她的愚蠢吗?
5 genes 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名词复数 )
  • You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
6 entities 07214c6750d983a32e0a33da225c4efd     
实体对像; 实体,独立存在体,实际存在物( entity的名词复数 )
  • Our newspaper and our printing business form separate corporate entities. 我们的报纸和印刷业形成相对独立的企业实体。
  • The North American continent is made up of three great structural entities. 北美大陆是由三个构造单元组成的。
7 promotion eRLxn     
  • The teacher conferred with the principal about Dick's promotion.教师与校长商谈了迪克的升级问题。
  • The clerk was given a promotion and an increase in salary.那个职员升了级,加了薪。
8 variant GfuzRt     
  • We give professional suggestions according to variant tanning stages for each customer.我们针对每位顾客不同的日晒阶段,提供强度适合的晒黑建议。
  • In a variant of this approach,the tests are data- driven.这个方法的一个变种,是数据驱动的测试。
9 susceptible 4rrw7     
  • Children are more susceptible than adults.孩子比成人易受感动。
  • We are all susceptible to advertising.我们都易受广告的影响。
10 cellular aU1yo     
  • She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
  • Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。
11 permanently KluzuU     
  • The accident left him permanently scarred.那次事故给他留下了永久的伤疤。
  • The ship is now permanently moored on the Thames in London.该船现在永久地停泊在伦敦泰晤士河边。
12 premature FPfxV     
  • It is yet premature to predict the possible outcome of the dialogue.预言这次对话可能有什么结果为时尚早。
  • The premature baby is doing well.那个早产的婴儿很健康。
13 prematurely nlMzW4     
  • She was born prematurely with poorly developed lungs. 她早产,肺部未发育健全。 来自《简明英汉词典》
  • His hair was prematurely white, but his busy eyebrows were still jet-black. 他的头发已经白了,不过两道浓眉还是乌黑乌黑的。 来自辞典例句
14 hospitable CcHxA     
  • The man is very hospitable.He keeps open house for his friends and fellow-workers.那人十分好客,无论是他的朋友还是同事,他都盛情接待。
  • The locals are hospitable and welcoming.当地人热情好客。