Why is it so hard to cure cancer? - Kyuson Yun

翻译人员: Tianyu Qiao 校对人员: Jack Zhang

Why is it so difficult to cure cancer?

为什么治愈癌症如此困难？

We've harnessed electricity,

我们已经成功开发了电力，

sequenced the human genome,

给人类基因组进行了排序，

and eradicated small pox.

成功根治了水痘。

But after billions of dollars in research,

但是在科学研究上 花费了数十亿美元后，

we haven't found a solution for a disease that affects more than 14 million people

我们还是没办法治愈一种 影响着超过 1400 万人

and their families at any given time.

和家庭的疾病。

Cancer arises as normal cells accumulate mutations.

癌症的病因是正常细胞的变异增多。

Most of the time, cells can detect mutations or DNA damage

大多数时候，细胞可以检测到 变异或 DNA 受损，

and either fix them or self destruct.

然后进行修复或者自我毁灭。

However, some mutations allow cancerous cells to grow unchecked

然而，有些变异会让 癌变的细胞悄悄增长，

and invade nearby tissues,

然后侵入附近的组织，

or even metastasize to distant organs.

或者转移到其它的器官。

Cancers become almost incurable once they metastasize.

癌变细胞一旦转移 就无法医治

And cancer is incredibly complex.

而且癌症非常复杂，

It's not just one disease.

它并不是单一的疾病。

There are more than 100 different types

癌症有 100 多个种类，

and we don't have a magic bullet that can cure all of them.

我们还没有一个能治愈 所有癌症的万能药。

就大多数癌症来讲，

For most cancers,

treatments usually include a combination of surgery to remove tumors

治疗方式通常包括 动手术切除肿瘤，

and radiation and chemotherapy to kill any cancerous cells left behind.

和做放射及化疗来除掉 剩余的癌细胞。

Hormone therapies,

激素疗法，

immunotherapy,

免疫治疗，

and targeted treatments tailored for a specific type of cancer

和针对某种癌症的定制疗法

are sometimes used, too.

有时候也会被采用。

In many cases, these treatments are effective

很多情况下，这些治疗方式很有效，

and the patient becomes cancer-free.

病人可以被治愈。

But they're very far from 100% effective 100% of the time.

但是这些疗法绝不算是 百分百的成功。

So what would we have to do to find cures for all the different forms of cancer?

那我们该怎样找到 治愈不同种癌症的解决方案呢?

We're beginning to understand a few of the problems

目前我们已经开始明白

scientists would have to solve.

科学家们该向哪些方向努力了。

First of all, we need new, better ways of studying cancer.

首先，我们需要更新和更好 的研究癌症的方法。

Most cancer treatments are developed using cell lines grown in labs

大多数癌症治疗法都是使用 实验室培育的细胞研发出来的，

from cultures of human tumors.

这些细胞来自人类的肿瘤体。

These cultured cells have given us critical insights

这些实验室培育的细胞 对于我们理解

about cancer genetics and biology,

癌症基因和生物机理来说非常关键，

but they lack much of the complexity of a tumor in an actual living organism.

但这种细胞缺失了活体内 肿瘤所含有的复杂性。

It's frequently the case that new drugs, which work on these lab-grown cells,

通常，新研发出的药 在实验室细胞上药效不错，

will fail in clinical trials with real patients.

但是试用在真正 的病人身上却没效果。

One of the complexities of aggressive tumors

活跃肿瘤的其中一个复杂性在于，

is that they can have multiple populations of slightly different cancerous cells.

即使有些癌细胞间的区别很小， 它们也可以产生出多个群体。

Over time, distinct genetic mutations accumulate in cells

时间一长，不同的基因变异 在细胞内积累起来，

in different parts of the tumor, giving rise to unique subclones.

出现在肿瘤的不同部位， 产生独特的亚克隆体。

For example, aggressive brain tumors called glioblastomas

比如，活跃的脑瘤 被称为胶质母细胞瘤，

can have as many as six different subclones in a single patient.

在一个母体中可以有 多达 6 个不同的亚克隆体，

This is called clonal heterogeneity,

这种现象叫做克隆异质性。

and it makes treatment difficult because a drug that works on one subclone

此特性让治疗变得很困难， 能治一种亚克隆体的药

may have no effect on another.

可能对另一种完全无效。

我们还面临着一个挑战。

Here's another challenge.

A tumor is a dynamic interconnected ecosystem

肿瘤是活跃的相互联系的生态系统，

where cancer cells constantly communicate with each other

癌细胞们一直在互相交流，

and with healthy cells nearby.

也和附近健康的细胞保持着联系。

They can induce normal cells to form blood vessels that feed the tumor

它们促使正常的细胞 形成为癌细胞供应养分和

and remove waste products.

清理废物的血管。

They can also interact with the immune system

它们也可以和免疫系统互动，

to actually suppress its function,

从而影响系统的正常运作，

让其无法识别和摧毁癌变部位。

keeping it from recognizing or destroying the cancer.

If we could learn how to shut down these lines of communication,

如果我们能研究出如何制止 这些互动和交流，

we'd have a better shot at vanquishing a tumor permanently.

就有可能永久地消灭癌变。

Additionally, mounting evidence suggests

另外，越来越多的证据显示，

we'll need to figure out how to eradicate cancer stem cells.

我们需要研究出 消除癌症干细胞的方法。

These are rare but seem to have special properties

干细胞不常见， 但是它们的特质是

that make them resistant to chemotherapy and radiation.

对化疗和放射疗法有抵抗性。

In theory, even if the rest of the tumor shrinks beyond detection during treatment,

理论上来讲，即使大多数肿瘤 在治疗期间收缩到无法被识别，

a single residual cancer stem cell could seed the growth of a new tumor.

一小点剩余的癌细胞 也有可能长成新肿瘤。

Figuring out how to target these stubborn cells

找到攻克这些倔强细胞的方法

might help prevent cancers from coming back.

也许可以帮助防止癌细胞的复发。

Even if we solved those problems, we might face new ones.

即使我们解决了这些问题， 也可能面临新的问题。

Cancer cells are masters of adaptation,

癌细胞的适应性非常强，

adjusting their molecular and cellular characteristics to survive under stress.

在苛刻的环境下也能通过调整 它们的分子和细胞特征生存下来。

When they're bombarded by radiation or chemotherapy,

当它们被放疗和化疗攻击的时候，

some cancer cells can effectively switch on protective shields

有些癌细胞可以 有效转换到自卫模式，

against whatever's attacking them by changing their gene expression.

改变它们的基因特征， 抵抗向它们发起进攻的因素。

Malignant cancers are complex systems that constantly evolve and adapt.

恶性癌症有着复杂的系统， 适应性强，变化多端。

To defeat them, we need to find experimental systems

要想攻克恶性癌症，我们需要找到 和它们有相似复杂性的系统

that match their complexity,

来进行实验，

and monitoring and treatment options that can adjust as the cancer changes.

并随着癌细胞的变化 随时调整治疗方案。

But the good news is we're making progress.

值得欣慰的是， 我已经取得了进步。

Even with all we don't know,

即使我们目前对癌症 的了解还不够多，

the average mortality rate for most kinds of cancer

大多数种类癌症的平均致死率

has dropped significantly since the 1970s and is still falling.

已经从 1970 年代开始 大幅度持续降低。

We're learning more every day,

我们每天都有新的研究成果，

and each new piece of information gives us one more tool to add to our arsenal.

每一点科研的新进展都使 我们抗击癌症的军火库更加壮大。