How does cancer spread through the body? - Ivan Seah Yu Jun

癌症是如何在体内传播的？ - Ivan Seah Yu Jun

翻译人员: Chelsea Luo 校对人员: Matt Chan

The onset of cancer usually begins as a solitary tumor

癌症一般是由身体某处单独的肿瘤演变而来的。

in a specific area of the body.

一旦肿瘤没被及时去除，

If the tumor is not removed,

cancer has the ability to spread to nearby organs,

癌细胞便有能力扩散到附近的器官，

as well as places far away from the origin, such as the brain.

甚至更远，例如大脑。

那么到底癌症是怎么转移到新的区域的呢？

So how does cancer move to new areas,

and why are some organs more likely to get infected than others?

为什么有些器官受感染的可能性会更大呢？

The process of cancer spreading across the body is known as metastasis.

癌细胞在体内扩散的过程叫做转移。

It begins when cancer cells from an initial tumor invade nearby normal tissue.

当癌细胞离开原发肿瘤部位侵入附近正常的细胞组织， 这一过程便开始了。

As the cells proliferate,

随着细胞的快速扩散，

they spread via one of the three common routes of metastasis:

它们通过三种不同转移路径中的其中一条， 扩散到体内其他部位。

transcoelomic, lymphatic, or hematogenous spread.

分别是种植性转移，血道转移和淋巴转移。

In transcoelomic spread, malignant cells penetrate the covering surfaces

在种植性转移中，恶性细胞 穿透体内腔体的表层。

of cavities in our body.

这些表层叫做腹膜。

These surfaces are known as peritoneum

and serve as walls to segment the body cavity.

它们像墙一样把我们的体腔分隔开来。

Malignant cells in ovarian cancer, for example,

举个例子，卵巢癌的恶性细胞

spread through peritoneum, which connects the ovary to the liver,

穿过连接卵巢和肝脏的腹膜，

resulting in metastasis on the liver surface.

使得癌症转移到肝脏表层。

Next, cancerous cells invade blood vessels when they undergo hematogenous spread.

接着，癌细胞侵入血管并开始血道转移，

As there are blood vessels almost everywhere in the body,

它们随着这些遍布全身的血管

malignant cells utilize this to reach more distant parts of the body.

到达身体较远的地方。

Finally, lymphatic spread occurs when the cancer invades the lymph nodes,

最后，癌细胞侵入淋巴结 发生淋巴转移

and travels to other parts of the body via the lymphatic system.

通过淋巴系统到达身体的其他部位。

As this system drains many parts of the body,

因为淋巴系统灌溉身体各处

it also provides a large network for the cancer.

这为癌症转移提供了巨大的网络。

In addition, the lymphatic vessels empty into the blood circulation,

汇入血液的淋巴管让 恶性细胞进入血液循环，

allowing the malignant cells to undergo hematogenous spread.

给了它们血道转移的机会。

Once at a new site, the cells once again undergo proliferation,

一旦到达新位置，恶性细胞再次 快速繁殖

and form small tumors known as micrometastases.

并形成小肿瘤，叫做微转移。

These small tumors then grow into full-fledged tumors,

这些小肿块最终繁殖成 发育完全的肿瘤，

and complete the metastatic process.

完成转移的过程。

Different cancers have been known to have specific sites of metastasis.

现在已经知道，不同类型的癌细胞会向不同的地方转移。

For example, prostate cancer commonly metastasizes to the bone,

比如说，前列腺癌通常转移到骨骼

while colon cancer metastasizes to the liver.

而直肠癌一般向肝脏转移。

Various theories have been proposed to explain the migration pattern

人们给出了许多理论来解释

癌细胞的迁移模式。

of malignant cells.

Of particular interest are two conflicting theories.

其中最引人注意的是两个相互矛盾的理论。

一位英国外科医生， 斯蒂芬·派吉特

Stephen Paget, an English surgeon,

came up with the seed and soil theory of metastasis.

提出了种子-土壤学说。

The seed and soil theory stated that cancer cells die easily

这种理论认为，在错误的微环境下

癌细胞很容易死亡，

in the wrong microenvironment,

hence they only metastasize to a location with similar characteristics.

因此它们只往相似的环境转移。

However, James Ewing, the first professor of pathology at Cornell University,

而詹姆斯·尤因，康奈尔大学的第一位病理学教授，

challenged the seed and soil theory,

却给出了与土壤学说相反的解释。

and proposed that the site of metastasis was determined by the location

他认为，转移的地点是由初期肿瘤

进入的血管和淋巴管的位置决定的。

of the vascular and lymphatic channels which drain the primary tumor.

Patients with primary tumors that were drained by vessels leading to the lung

当一个患者初期肿瘤的脉管通向肺部，

would eventually develop lung metastases.

他的癌细胞便会转移到肺部。

Today, we know that both theories contain valuable truths.

如今，我们知道这两个理论都有一定的道理，

Yet the full stories of metastasis is much more complicated

不过癌细胞的转移比它们解释的 要复杂太多太多。

than either of the two proposed theories.

Factors like the cancer cell's properties,

许多因素，例如癌细胞的特点

and the effectiveness of the immune system in eliminating the cancer cells,

和免疫系统去除这些细胞的效力

also play a role in determining the success of metastasis.

都影响着癌症转移的成功率。

Unfortunately, many questions about metastasis remain unanswered until today.

不幸的是，很多关于转移 的问题至今仍是未解之谜。

Understanding the exact mechanism holds an important key

完全了解该机理对于

to finding a cure for advanced stage cancers.

寻找治疗晚期癌症的方法来说至关重要。

By studying both the genetic and environmental factors,

研究使癌细胞转移成功的

which contribute to successful metastasis,

基因因素和环境因素

we can pinpoint ways to shut down the process.

可以让我们找到阻止这过程的方法。

The war against cancer is a constant struggle,

与癌症的战斗是持续而艰难的，

and scientists are hard at work developing new methods against metastasis.

科学家们依旧在研究 新的抑制转移的方法。

Of recent interest is immunotherapy,

最近备受关注的是免疫疗法：

a modality which involves harnessing the power of the immune system

通过加强免疫系统的能力

to destroy the migrating cells.

来消灭迁移的细胞。

许多方式都能达到这种效果，

This can be done in different ways,

such as training immune cells to recognize cancerous cells via vaccines.

例如通过疫苗让免疫细胞 识别癌细胞。

或者注射人造白介素，一种通常由 免疫系统分泌的化学成份，

The growth and activity of the immune cells

can also be stimulated by injecting man-made interleukins,

来刺激免疫细胞的生长和活动。

chemicals which are usually secreted by the immune cells of the body.

These two treatments are only the tip of the iceberg.

这两种治疗方式都只是冰山一角。

With the collaborated research efforts of governments, companies and scientists,

在政府，公司和科学家们 的共同努力下

perhaps the process of metastasis will be stopped for good.

也许有一天，我们真的能成功制止癌症转移。