5分钟前，你的身体刚刚杀死了一个癌细胞：英语精读讲义

Somewhere in your body,

在你身体的某个角落，

your immune system just quietly killed one of your own cells,

你的免疫系统刚刚悄无声息地杀死了一个你自身的细胞，

stopping it from becoming cancer

阻止了它癌变，

and saving your life.

从而拯救了你的生命。

It does that all the time.

它一直在做着这样的工作。

The vast majority of cancer cells you develop will be killed without you ever noticing, 語法

你体内产生的绝大多数癌细胞都会在你毫无察觉的情况下被消灭，

which is an incredibly hard job because of what cancer cells are.

这是一项极其艰难的任务，因为癌细胞有着特殊的本质。

Parts of yourself that start to behave as individuals,

它们是你身体的一部分，却开始像独立的个体一样运作，

even if it hurts you.

哪怕这会伤害到你。

What is cancer and how does your body kill it all the time?

什么是癌症？你的身体又是如何无时无刻不在消灭它的？

Cancer is when corrupted cells multiply uncontrollably.

癌症是受损细胞失控繁殖的结果。

It can emerge from basically every type of cell in your body,

它基本上可以从你体内的任何一种细胞中产生，

so there's not just a single type of cancer, 語法

所以癌症不仅仅只有一种，

but hundreds.

而是有数百种。

Some grow slowly,

有些生长缓慢，

others are aggressive,

有些则具有很强的侵袭性，

some can be treated effectively,

有些可以被有效治疗，

others are deadly.

而另一些则是致命的。

In a sense,

从某种意义上说，

a cell that becomes cancer turns into something ancient and something new. 短語動詞

一个变成癌的细胞既退化成了某种古老的事物，又变成了某种新的东西。

Over billions of years,

在数十亿年的时间里，

evolution has molded cells to survive and thrive in a hostile environment, 短語搭配

进化塑造了细胞，让它们在恶劣的环境中生存繁衍，

fighting for space and resources,

争夺空间和资源，

until a new and exciting way of life emerged,

直到一种全新且令人兴奋的生活方式出现——

cooperation.

合作。

A division of labor that allowed cells to specialize and become more successful together. 用詞

这种分工让细胞能够专业化，并共同取得更大的成功。

But cooperation requires sacrifices.

但是合作需要牺牲。

For a multicellular being to stay healthy,

为了让多细胞生物保持健康，

the well-being of the collective has to matter more than the survival of the individual cell. 語法

集体的福祉必须凌驾于单个细胞的生存之上。

Cancer cells stop being part of the collective and become individuals again.

癌细胞不再作为集体的一部分，而是再次成为了个体。

Your body can handle a few rogue cells, 用詞

你的身体可以处理少数几个叛变的细胞，

but some cancer cells divide again and again,

但有些癌细胞会一遍又一遍地分裂，

becoming a sort of new organism within you,

在你体内变成一种类似新生物的存在，

taking resources you need to survive,

掠夺你生存所需的资源，

competing for the space you inhabit,

争夺你所居住的空间，

destroying the organs they were part of in the process.

并在这个过程中摧毁它们曾经所属的器官。

Despite the harm they cause,

尽管它们会造成伤害，

cancer cells are not evil.

癌细胞却并不邪恶。

They don't want to hurt you,

它们不想伤害你，

they don't want anything.

它们什么也不想要。

Cells are protein robots that just follow their programming,

细胞只是遵循其程序的蛋白质机器人，

which unfortunately has been corrupted.

只是不幸的是，它的程序被破坏了。

The soul of the cell.

细胞的灵魂。

In a nutshell, 習語

简而言之，

your cells have a nucleus filled with DNA.

你的细胞里有一个充满DNA的细胞核。

It consists of genes,

它由基因组成，

instructions for how to build proteins and when to make each one.

基因就是关于如何制造蛋白质以及何时制造每种蛋白质的指令。

These building instructions are copied and transferred to ribosomes,

这些制造指令被复制并转移到核糖体，

where they're used to make proteins.

在那里被用来制造蛋白质。

What kind of proteins your cells make determine what they can do.

你的细胞制造什么样的蛋白质决定了它们能做什么。

The important thing here is that a corrupt gene means you get a corrupt protein,

这里重要的是，基因受损意味着你会得到受损的蛋白质，

which will get important later.

这一点稍后会很关键。

Your DNA gets a tiny bit corrupted,

你的DNA会受到极微小的破坏，

it mutates tens of thousands of times each day.

它每天变异数万次。

Most of the time without any special cause,

大多数时候没有任何特殊原因，

just by being alive.

仅仅是因为你活着。

Almost all of these mutations are fixed very quickly or are not problematic.

几乎所有这些突变都会被非常快速地修复，或者根本不会造成问题。

Still, over time as your cells make copies of themselves,

然而，随着时间的推移，当你的细胞进行自我复制时，

damage is accumulating.

损伤就在不断积累。

Imagine having to make copies from copies from copies for decades. 表達脈絡

想象一下，几十年里不得不拿着复印件再复印，再拿复印件复印。

Maybe one day a hair got on the scanner or a corner got frayed.

也许有一天，扫描仪上掉了一根头发，或者角落被磨损了。

Each new mistake becomes part of the new copies and all the copies that follow.

每一个新错误都会成为新复印件的一部分，并体现在所有随后的复印件中。

You can increase DNA damage by doing things like smoking,

你可以通过吸烟、

drinking alcohol, by being obese,

饮酒、肥胖、

breathing in asbestos,

吸入石棉、

by not using sunscreen,

不涂防晒霜、

or contracting a virus like HPV. 文化背景

或者感染像HPV这样的病毒来增加DNA损伤。

But the simplest way to damage DNA and get cancer

但是损伤DNA并患上癌症的最简单方法，

is to be alive long enough.

就是活得足够久。

For many cancer cases,

对于许多癌症病例来说，

there is no cause other than bad luck.

除了运气不好，没有任何其他原因。

The damage that leads to cancer.

导致癌症的损伤。

We are simplifying,

我们把事情简化一下，

but roughly there are three categories of genes that need to be corrupted so cancer can arise.

大致有三类基因需要被破坏才能引发癌症。

The first key mutation is in the appropriately named tumor suppressor genes or TSGs. 文化背景

第一个关键突变发生在名副其实的抑癌基因（TSG）中。

These genes are a bunch of things.

这些基因包含很多种类。

For one, they produce control mechanisms that continuously scan your DNA for mistakes and copying errors 表達脈絡

首先，它们产生控制机制，不断扫描你的DNA中的错误和复制失误，

and fix them right away.

并立即修复它们。

And then they keep normal cells from multiplying recklessly. 語法

然后，它们会阻止正常细胞不计后果地繁殖。

If TSGs become damaged,

如果抑癌基因（TSG）受损，

your cells basically forget how to repair themselves

你的细胞基本上就会忘记如何自我修复，

and can reproduce unchecked. 用詞

并可能不受控制地繁殖。

The second crucial mutation can happen in your oncogenes. 文化背景

第二个关键突变可能发生在你的原癌基因中。

When oncogenes are turned on,

当原癌基因被开启时，

the cell is told to multiply rapidly.

细胞会被指令快速繁殖。

They were super active when you were inside your mother's womb.

当你在母亲的子宫里时，它们超级活跃。

To turn a single original cell into trillions in months,

为了在几个月内把一个原始细胞变成数以万亿计的细胞，

it needs to divide and grow rapidly.

它需要快速分裂和生长。

These rapid growth genes are turned off when there's enough of you. 短語動詞

当你长得足够大时，这些快速生长的基因就会被关闭。

When your oncogenes get corrupted,

当你的原癌基因受损时，

they basically turn on again.

它们基本上就会再次开启。

The third crucial mutation is in your cells' suicide switch. 習語

第三个关键突变发生在细胞的“自杀开关”上。

Most cells are constantly recycled and refreshed.

大多数细胞都在不断被回收和更新。

When cells amass too much damage,

当细胞积累了过多的损伤时，

they usually notice and special genes trigger a controlled suicide called apoptosis. 文化背景

它们通常能察觉到，特殊基因会触发一种称为细胞凋亡的受控自杀。

If the genes that control this process get damaged,

如果控制这个过程的基因受损，

cells are free to live on despite being dangerously corrupted. 講解

细胞就会无视危险的损坏而继续存活。

So, if a cell becomes unable to fix the mistakes in its genetic code,

所以，如果一个细胞变得无法修复其遗传密码中的错误，

loses the ability to destroy itself when it notices the damage,

在察觉到损伤时失去了自我毁灭的能力，

and begins to grow rapidly without restraint,

并且开始不受约束地快速生长，

it turns into a young cancer cell.

它就变成了一个初期的癌细胞。

These cells have to be killed as quickly as possible.

这些细胞必须尽快被杀死。

While they are bad at this stage,

虽然它们在这个阶段是有害的，

they are still pretty weak and easy to kill.

但它们仍然相当虚弱，很容易被杀死。

But if they continue to mutate and increase in number, 短語搭配

但如果它们继续变异并增加数量，

they can learn to avoid your defenses and become a real threat.

它们就能学会躲避你的防御，成为真正的威胁。

At any moment of your life,

在你生命的任何时刻，

your immune system is hunting these cells.

你的免疫系统都在搜捕这些细胞。

But how do you identify and kill corrupted cells that seem indistinguishable from healthy ones?

但是，你如何识别并杀死那些看起来与健康细胞无法区分的受损细胞呢？

How to find cancer?

如何寻找癌症？

Well, here we come back to the proteins your cells produce and the story they tell. 短語動詞

好吧，这又要回到你的细胞所制造的蛋白质以及它们所讲述的故事上。

So, if for example, your oncogenes switch back on,

所以，举例来说，如果你的原癌基因重新开启，

they make oncogene proteins.

它们就会制造原癌基因蛋白质。

Your immune system knows that they should not be present if you're an adult.

你的免疫系统知道，如果你是成年人，它们就不应该出现。

So, to know which cells are corrupt and which are healthy,

因此，要知道哪些细胞受损，哪些是健康的，

your immune system needs to know what proteins they're making inside.

你的免疫系统需要知道它们内部正在制造什么蛋白质。

To solve this,

为了解决这个问题，

evolution came up with MHC class 1 molecules, 講解

进化出了一套MHC-I类分子系统，

a sort of display window that makes cells transparent. 習語

这是一种让细胞变得透明的展示橱窗。

Cells constantly take little samples of the proteins they make

细胞不断地提取它们制造的蛋白质的小样本，

and put them into thousands of these MHC molecules

并将它们放入数以千计的这些MHC分子中，

to showcase what they're doing.

以展示它们正在做什么。

The selection is constantly refreshed,

展示的样本会不断更新，

always giving an up-to-date picture. 短語搭配

始终提供最新的情况。

There's a whole library of proteins that are highly dangerous

存在着一个极其危险的蛋白质特征库，

and should not be made by healthy cells,

健康细胞不应该制造这些蛋白质，

and your immune system has them all on file. 習語

而你的免疫系统已经将它们全部建档。

It has billions of specialized cells called T cells 文化背景

它拥有数十亿被称为T细胞的特化细胞，

made to recognize specific proteins.

专门用来识别特定的蛋白质。

If a T cell sees a forbidden protein in an MHC display window,

如果T细胞在MHC展示橱窗中看到了被禁止的蛋白质，

it knows that the cell is corrupted and kills it immediately.

它就知道该细胞已受损，并立即将其杀死。

But there's a flaw in this system.

但这个系统存在一个缺陷。

What if a cancer cell mutates and finds a way to circumvent this process? 短語搭配

如果癌细胞发生突变，找到绕过这个过程的方法怎么办？

All it needs to do is to stop making MHC class 1 molecules 語法

它需要做的就是停止制造MHC-I类分子，

and boom, it's invisible.

然后砰！它就隐身了。

Without display windows,

没有展示橱窗，

the immune system is blind and can't identify cancer anymore. 習語

免疫系统就成了瞎子，再也无法识别癌症了。

Fortunately,

幸运的是，

evolution found an ingenious solution,

进化找到了一个巧妙的解决方案：

the natural killer cell, 文化背景

自然杀伤细胞，

a judge, jury, and executioner. 習語

它是法官、陪审团和刽子手。

The killer.

杀手。

At this very second,

就在这一秒，

hundreds of millions of natural killer cells are patrolling your body,

数以亿计的自然杀伤细胞正在你的体内巡逻，

looking for cells that have already turned into cancer

寻找那些已经变成癌症

or are corrupted by a virus.

或被病毒破坏的细胞。

Natural killer cells go from cell to cell

自然杀伤细胞在细胞间游走，

to check for one thing.

只检查一件事。

Does a cell have MHC class 1 molecules?

这个细胞有MHC-I类分子吗？

Does it have a display window

它有展示橱窗吗？

and is it doing its duty of showing off what's going on inside itself? 講解

它是否履行了展示其内部情况的职责？

This is so amazing because it covers all of your bases. 習語

这真是太神奇了，因为它做到了万无一失。

While T cells look for the presence of the unexpected, 表達脈絡

T细胞寻找的是不应存在之物的出现，

something that should not be here,

即本不该在这里的东西；

natural killer cells look for the absence of the expected,

而自然杀伤细胞寻找的是应有之物的缺失，

the absence of something that should be here.

即本应在这里的东西却不在了。

The logic is,

逻辑是，

if a cell does not have display windows,

如果一个细胞没有展示橱窗，

it wants to hide something.

它就想隐藏什么。

And a cell that hides something must be killed.

而隐藏东西的细胞必须被杀死。

What makes the natural killer cell even more metal is that it's always in murder mode. 講解

让自然杀伤细胞更加硬核的是，它始终处于杀戮模式。

It patrols your body,

它在你体内巡逻，

checking cell after cell with the intention of killing it. 短語搭配

带着杀死的意图检查一个又一个细胞。

Your healthy cells have to convince it that they should not die today.

你健康的细胞必须说服它，它们今天不该死。

And a way to do that is to have MHC class 1 molecules. 語法

做到这一点的方法就是拥有MHC-I类分子。

So, in summary,

所以总的来说，

almost all young cancer cells you will ever develop in your life

你一生中可能产生的所有初期癌细胞，几乎

will be killed by your immune system.

都会被你的免疫系统杀死。

Okay,

好吧，

but if your body is this prepared, 用詞

但如果你的身体准备得如此充分，

why do we still get cancer?

为什么我们还是会得癌症呢？

Well,

这是因为，

sometimes cancer cells mutate more and get much better at fighting back. 短語動詞

有时癌细胞会发生更多的突变，反击能力大大增强。

Cancer is a story of an arms race, 習語

癌症是一个军备竞赛的故事，

an arms race that we will win eventually,

一场我们最终会赢得的军备竞赛，

maybe with the help of natural killer cells.

也许是在自然杀伤细胞的帮助下。

Right now,

目前，

a number of therapies are beginning to show amazing promise, 短語搭配

许多疗法开始展现出惊人的前景，

from cancer-fighting vaccines to engineered T cells 語法

从抗癌疫苗到基因工程T细胞，

and even natural killer cells.

甚至自然杀伤细胞疗法。

We'll look at these therapies in future videos.

我们将在以后的视频中介绍这些疗法。

So,

所以，

the war is not won yet,

这场战争还没有胜利，

but we are on to cancer 習語

但我们已经摸清了癌症的底细，

and eventually it will be eliminated once and for all. 習語

最终它将被一劳永逸地消灭。

Maybe sooner than we think.

也许比我们想象的还要快。

This video was made possible in part by direct viewer support 表達脈絡

本视频的制作部分得益于观众的直接支持，

and in part through a grant by Gates Ventures.

部分得益于Gates Ventures的赞助。

Thanks a lot for their support

非常感谢他们的支持，

and stay tuned for part two. 習語

请继续关注第二部分。

Please check out our source document for more background and in-depth information. 講解

请查看我们的参考文档以获取更多背景信息和深入资料。