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Zoologger:公然藐视致癌物质的啮齿动物

已有 3874 次阅读 2013-8-26 17:46 |个人分类:小楼一夜听春雨——翻译|系统分类:科普集锦| 啮齿动物, 致癌物质, 天然抗癌



    201381913:28 安迪科格伦

种类: SPALAX ehrenbergi盲鼹鼠

栖息地:如果你碰巧住在地中海东部,那它们就在你脚下的土壤里,潮湿、黑暗又缺氧的地下坑道里。

 

中东盲鼹鼠将其20年的寿命几乎全都匆匆忙忙间花在了缺氧、黑暗还发霉的地下坑道里。但是关于它还有个问题:在近50年对这种啮齿动物的研究里居然都没有发现它们会患上癌症。我们最终也可能会将枪口对准这种辗转腾挪躲避肿瘤的技能。

 

鼹鼠已经成功进化了两次。皮毛是唯一能区分非洲裸鼹鼠和亚洲盲鼹鼠的特征,但这两种动物居然在啮齿类动物完全不同的进化树分支。

在这两种里,属于一个bathyergids家族的非洲鼹鼠可能更特殊些。两个非洲品种-裸鼹鼠和达马拉兰鼹鼠-它们是世界上唯一两种像白蚁般社会化的哺乳动物在:一个的女王一样的雌性产下所有其他成员。

spalacid家族的亚洲鼹鼠并不遵循这种不寻常的繁殖行为。但它们却和它们的非洲兄弟共享一个特征:它们从来不会患上癌症。事实上,研究人员刚刚发现,即便把中东盲鼹鼠暴露在一些强力致癌化学物质里,它们也不会患癌。实验把20只鼹鼠暴露在强力致癌物长达三年,但是只有一只得了肿瘤。

“我们已经证明,无论鼹鼠是年轻还是年老,它们都几乎不可能患上癌症,”以色列海法大学的亚伦Aaron AVIVI说。相比之下,大鼠和小鼠暴露于相同的化学品里短短几个月内就会得上肿瘤。

顽强的免疫力

鼹鼠强免疫力可能的成因是,他们的细胞和组织中含有某种物质可以保护它们甚至免受最强力致癌化学物质的危害。亚伦和他的同事们正试图找出这些物质,从而用新颖有效的方式去和人类癌症相抗衡- 他们已经有所斩获。

这个团队把从鼹鼠腋下获得的成纤维细胞与人体肝癌和乳腺癌细胞培养在了一起。成纤维细胞迅速杀死了人体癌细胞。所以成纤维细胞分泌的液体里有可能有某种东西可以抗衡癌症。而当他检查实验时,亚伦发现,成纤维细胞和他们的分泌物并不会损害健康的人体细胞。“它只针对癌细胞,”他说。

相比较而言,实验室正常的大鼠、小鼠和另一种被称为刺鼠的啮齿动物其成纤维细胞和分泌物都无力阻止人类癌症细胞的生长。

好粘

今年早些时候,纽约罗切斯特大学的一个研究小组发现了在非洲裸鼹鼠的体内发现了一种化学物质,这种化学物质似乎可以保护它们免于受到癌症的危害。维拉Vera Gorbunova和她的同事们得出的结论是这种化学物质是一种高分子量透明质酸(HMM –HA)——鼹鼠通过分泌这种粘性物质来在密闭蜿蜒的地下隧道里穿行。

当维拉用遗传工程手段来处理裸鼹鼠使其不能再分泌HMM-HA以后,他们变得极易患癌,这表明该物质是保护他们的关键。

但是亚伦并不确信,HMM-HA就可以解释他的中东鼹鼠为什么不得癌症。他说,鼹鼠的成纤维细胞提取物里确实含有粘性物质,但是它似乎并不会在动物的天然抗癌能力里发挥关键作用,在实验室中抵抗癌细胞也并不活跃。

维拉说,可能还有一些其他的机制在共同起作用。中东鼹鼠的细胞会分泌另一种被称为β-干扰素化学物质,它可以杀死癌细胞。但她仍然相信,保护裸鼹鼠和盲鼹鼠的关键化学物质是HMM-HA

亚伦同时还在继续检查其他能杀死癌细胞的化学物质。“我们未来的工作就是去发现鼹鼠的细胞到底分泌了哪种能杀死癌细胞的物质,“他说。

Zoologger: The rat thatdefies powerful carcinogens

·                           Updated 13:28 19 August2013 by Andy Coghlan

·                           For similar stories, visitthe Zoologger and Cancer Topic Guides

Zoologger is our weekly column highlighting extraordinary animals – andoccasionally other organisms – from around the world

Species: Spalax ehrenbergi
Habitat: Dark, suffocating tunnels in damp soildeep beneath you – if you happen to live in the eastern Mediterranean

As anti-cancer regimes go, this one isn't going to get many takers. The Middle East blind mole rat spends almost all of its 20years of life hurrying down dark and fusty tunnels full of oxygen-deprived air.But for reasons unknown, it works: in 50 years of research on the rodents, nonehas ever spontaneously developed cancer. We might finally be zeroing in on anexplanation for their tumour-dodging skills.

Mole rats are so successful they've evolved twice. Fur might seem be theonly thing distinguishing the naked mole ratsMovie Camera of Africa from theblind mole rats of Asia, but the two animalsactually sit on entirely different branches of the rodent evolutionarytree.

Of the two groups, the mole rats of Africa,which belong to a family called thebathyergids, are probably the more peculiar. Two African species – the naked mole ratand the Damaraland mole rat – are the only mammals in the world to have optedfor a termite-like eusocial existence: a single queen gives birth to all other colony members.

The Asian mole rats – in the spalacid family – do not go in for this kind of unusual breeding behaviour. But theydo share one thing in common with their African doppelgangers: they neverdevelop cancer. In fact, researchers have just discovered that the Middle East blind mole rat will not develop cancer evenwhen it is exposed to some potent cancer-causing chemicals. After three yearsof exposure to one of two powerful carcinogens, only one of the 20 animalsstudied developed any tumours.

"We've shown that whether the rats are young or old, it's almostimpossible to induce cancer in them," says Aaron Avivi of the University of Haifain Israel.By contrast, rats and mice exposed to the same chemicals developed tumours in amatter of months.

Stubbornimmunity

A possible implication of the mole rats' stubborn immunity is that theircells and tissues contain substances that protect them even from some of themost powerful cancer-causing chemicals. Avivi and his colleagues are now tryingto identify such substances, in an effort to find new and potent agents tocombat cancer in people – and they are making progress.

The team took fibroblast skin cells from the armpits of the rats and grewthem in culture alongside cancer cells, including two types each of human liverand breast cancers. The fibroblasts rapidly killed the human cancer cells. Sodid fluids secreted by the fibroblasts, suggesting that there's something inthere of great value to combat cancer. And when he checked, Avivi found thatthe fibroblasts and their secretions didn't harm healthy human cells. "Itwas only cancer cells," he says.

As controls, fibroblasts and secretions from normal lab rats, mice, andanother rodent called the spiny mouse were powerless to stop the human cancercells growing.

Globbygoo

Earlier this year, a research team from the Universityof Rochester in New York identified a chemical in Africannaked mole rats that seems to protect them against developing cancer. Vera Gorbunova and her colleagues concluded that the chemical is high-molecular-masshyaluronan (HMM-HA) – a sticky, globbygoo that the rats secrete to help them slither through tight tunnelsunderground.

When Gorbunova genetically engineered naked mole rats so that they couldnot make HMM-HA, they became vulnerable to cancer, suggesting that thesubstance is a key to protecting them.

Avivi isn't convinced that HMM-HA can explain why his Middle East mole rats do not get cancer, though. He says that theextracts from their fibroblasts do contain the sticky substance, but that inspalacids it does not seem to play a key role in the animals' naturalresistance to cancer or activity against cancer cells in the lab.

Gorbunova says there are some other possible mechanisms. The Middle East mole rat cells might secrete anotherchemical, called beta interferon, which kills cancerous cells. But she remainsconvinced that the key chemical protecting both naked and blind mole rats isHMM-HA.

Avivi, meanwhile, is continuing to check for other cancer-killingchemicals that might be responsible. "Our future work is to try to findwhat Spalax cells secrete that only interacts with andkills cancer cells," he says.

 

 http://www.newscientist.com/article/dn24055-zoologger-the-rat-that-defies-powerful-carcinogens.html




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