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When you hear the word "tumor", you probably think "not good". And they can be pretty scary.
当你听到‘肿瘤’这个词的时候，你或许会觉得这是‘不好的东西’。而且它们非常可怕。
In their mildest form, tumors are just a lump of cells hanging out in your body.
在肿瘤最温和的时期，它们只是挂在你身体内的一块细胞。
At their worst, those cells are dividing and spreading like wildfire — they're cancerous.
最糟糕的情况下，那些细胞会分裂，像野火般迅速传播—它们是癌性的。
But there's one kind of tumor that's basically straight out of a horror movie.
但是有一种肿瘤，它们像是从恐怖电影里走出来的一样。
If you peek inside a teratoma, you might find hair, teeth, eyes, or even brain cells.
如果你瞥一眼畸胎瘤，你或许会看到上边有毛发、牙齿、眼睛甚至是脑细胞。
As strange as these tumors are, the jumbles of body parts aren't actually turning into people.
虽然这些肿瘤非常怪异，但是这些身体部分是不会真的转变成人的。
But they have taught us a lot about stem cells and how early development works.
但是它们告诉了我们很多关于干细胞的知识以及其早期发育的作用。
Most tumors start when a random mutation in one cell's DNA makes it go rogue and divide too much.
多数肿瘤开始于某一细胞DNA中的随机突变然后分裂。
So, for instance, a lung tumor might be a cluster of the cells that would normally line your lungs.
例如，肺肿瘤或许是正常排列在你肺部的一块细胞。
If that tumor keeps growing, the cells can develop more random mutations, which can create more small differences between them.
如果这块肿瘤持续生长，细胞也会发育出更多随机突变，因而在此之间创造出了更多细小的区别。
But — on the whole — it's still lung-like tissue.
但总体而言，它仍然是类似肺部的组织。
Teratomas, on the other hand, look like you blended up a human and started growing something from the goop.
另一方面，畸胎瘤看起来像是把将人类搅浑然后从这一坨黏糊糊的东西上开始发育。
And we think that's because of the cells that spawn these tumors.
我们认为这是因为细胞产生了这些肿瘤。
Most teratomas develop from germ cells in the ovaries and testes.
多数畸胎瘤是从卵巢和睾丸的生殖细胞中生长出来的。
Those are the cells that divide to produce mature sperm and eggs.
那些细胞会进行分裂，产生成熟的精子和卵子。
As you probably know, sperm and eggs fuse together to make embryos.
你或许知道，精子和卵子相结合制造出了胚胎。
And the cells in early embryos have an ability biologists call pluripotency,
早期胚胎中的细胞有一种被生物学家成为多能性的能力，
which means that with the right physical and chemical signals,
这意味着只要有正确的生理和化学信号，
they can become pretty much anything, from skin cells to liver cells.
它们可以变成任何东西，比如皮肤细胞或肝细胞。
If enough random mutations happen in germ cells, they can unlock pluripotency at the wrong time.
如果干细胞中发生足够的随机突变，它们可以在错误的时机封锁多能性。
Combined with wildly dividing cells, that leads to teratomas.
和疯狂的分裂细胞相结合，它们可以导致畸胎瘤。
As teratomas form, they have at least a tiny bit of all three kinds of developmental tissue that embryos have.
畸胎瘤至少拥有三种少量的发育组织，而少量这三种发育组织是胚胎所拥有的。
There's the endoderm, which goes on to make your gut lining, the mesoderm,
它们分别是内胚层，持续组成肠壁；中胚层，
which makes your muscles, blood vessels, and skeleton, and the ectoderm, which makes your skin and brain.
组成你的肌肉、血管和骨架，以及外胚层，组成你的皮肤和大脑。
To be clear, they are not embryos — their growth isn't nearly controlled enough.
说得清楚点就是，它们并非胚胎—它们的生长没有得到足够的控制。
But that developmental tissue is how hair and eyeballs can start sprouting in these tumors.
但是那种发育组织是毛发和眼球如何能在这些肿瘤中开始发芽的原因。
Scientists really started digging into teratomas in the 1950s and 60s.
科学家是在1950年代和60年代开始研究畸胎瘤的。
A team using mice to study the health hazards of cigarettes found teratomas in a mouse's testes,
一组团队利用老鼠研究香烟的健康危害，但他们却在老鼠的睾丸中发现了畸胎瘤，
then switched over to tumor research soon after.
然后他们很快便转向了肿瘤研究。
Through careful experimentation with these tumors, biologists started to realize that embryonic development happened in a similar way.
通过对这些肿瘤的仔细研究，生物学家开始意识到胚胎的发育也是利用一种类似的方式。
In embryos it was just … less broken.
只是在胚胎中没有那么破碎。
Plus, they discovered that mouse embryonic stem cells implanted into the testes of healthy adult mice could grow into teratomas too.
再加上他们发现植入健康成年老鼠体内的老鼠胚胎干细胞也可以生长成畸胎瘤。
So really, you can pretty much trace the field of stem cell research back to teratomas.
所以真的可以将干细胞研究领域追溯回畸胎瘤。
And it's a field that could help a lot of people someday.
这个领域在未来能够帮助很多人。
Normally, it's hard to donate tissues to patients that need them, because our bodies reject foreign stuff.
一般来说，要向需要的病人捐赠组织是件困难的事情，因为我们的身体会排斥外来物质。
That's where pluripotent stem cells come in, like embryonic stem cells.
所以就需要多能干细胞，比如胚胎干细胞。
We might be able to use them to grow tissues that can be transplanted without triggering those defenses,
或许我们能够利用它们培育可供移植的组织而无需触发体内的防御机制，
which could be really useful for medicine.
这一点对医学来说非常有帮助。
But, obviously, scientists don't want to accidentally transplant tissues that create teratomas.
但是显然，科学家并不想蓄意移植导致畸胎瘤的组织。
Even if it turns out to be benign, finding a tooth-filled lump inside you would not be a good surprise.
即使是良性的肿瘤，但在你的身体内找到满是牙齿的肿瘤块也不是件好事。
So there's a lot we have to learn before these potential therapies get close to becoming a reality.
所以在将潜在治疗方法变成现实之前，我们还有很多需要去了解的。
And on that list is why seemingly normal embryonic stem cells grow into tumors with a bunch of body parts.
其中包括，为什么看似正常的胚胎干细胞会发育成长有人类部分的肿瘤。
Thanks for watching this episode of SciShow!
感谢收看本期《科学秀》！
If you want to learn about more weird things hiding in human bodies, check out our video about the natural painkiller in your spit!
如果你想了解更多隐藏在人体内的诡异事情，请点击观看我们关于人类唾液中天然止痛药的视频！
And for more of all kinds of science, you can go to youtube.com/scishow and subscribe.
观看更多不同科学视频，请登录youtube.com/scishow进行订阅。
