白血病成因以及治療方法

Despite advances in medicine, cancer remains one of the most frightening diagnoses patients can receive.

盡管醫(yī)學在進步，癌癥仍是患者們最怕聽到的診斷結果。

What makes it so difficult to cure is that it's not one illness,

使它難以治愈的原因是，它并不是一個單一的病變，

but a family of over 100 diseases occurring in different types of cells.

而是在不同的細胞內(nèi)發(fā)生的超過100種病變的統(tǒng)稱。

And one type of cancer has the unfortunate distinction of afflicting children more than any other type.

其中有一種癌癥給兒童帶來的折磨比其它任何一種癌癥都更加難熬。

This is leukemia, a cancer that begins in stem cells found in the bone marrow.

這就是白血病，一種始于骨隧中干細胞的癌癥。

A stem cell is a bit like an infant, undeveloped but possessing great potential.

干細胞有點兒像一個嬰兒，還未充分發(fā)育但潛能巨大。

Many stem cells specialize and become cells of organs, like the liver, brain and heart.

許多干細胞經(jīng)過分化變成器官細胞，例如肝臟、大腦和心臟。

But in some tissues, they can continue to divide into new stem cells throughout development,

但在某些組織中，它們將繼續(xù)分裂產(chǎn)生新的干細胞，

and into adulthood in order to frequently generate new cells and keep up with the body's needs.

而后再分化成熟以跟上身體生長發(fā)育需求。

One example is the bone marrow, where stem cells differentiate into many types of blood cells.

其中一個例子就是骨髓，其中的干細胞將分化為多種血細胞。

That includes red blood cells, which carry oxygen from the lungs to all tissues,

包括紅血球，用于將氧氣從肺輸送到所有組織，

platelets, which help stop bleeding by sticking to damaged blood vessels,

血小板，堵住受傷的血管以止血，

and white blood cells, which patrol the body, destroying potentially harmful invaders.

以及白血球，它們負責守護身體，摧毀潛在的有害入侵者。

Every once in a while, something goes wrong during a stem cell's specialization process

有時干細胞在分化過程中會出問題，

and harmful mutations occur in the cell's DNA.

細胞DNA會出現(xiàn)有害突變。

Cells with compromised DNA are supposed to self-destruct,

受損DAN的細胞一般會凋亡，

but some damaged cells ignore this order, replicating uncontrollably, even as they lose their original function.

但有些受損細胞沒有遵守這個規(guī)律，而是不受控制的不斷復制，盡管它們已失去了原有的功能。

These are what we know as cancer cells.

這就是我們所說的癌細胞。

It is not yet clear why leukemia is the most common childhood cancer,

為什么白血病是兒童最易患的癌癥還尚未知曉，

but one contributing factor may be that leukemias are often caused by just one or two DNA modifications,

但原因之一可能是一兩個DNA位點突變就能使白血病細胞產(chǎn)生，

while most cancers require many of them, allowing leukemias to arise faster than other types of cancer.

而其他癌癥則需要多個DNA位點的突變，這就使得白血病比其他癌癥發(fā)病快得多。

Moreover, some DNA alterations can occur in white blood cells during fetal development,

此外，白細胞中某些DNA改變在胎兒時期就能發(fā)生，

further increasing the risk of early leukemia.

所以增加了早期患白血病的風險。

But though it affects more children than any other cancer, adults constitute the majority of leukemia patients overall.

盡管比其他癌癥，兒童更容易得白血病，但總的來說成人白血病患者還是占大多數(shù)的。

Once leukemia strikes, the damaged cells reproduce in the blood and the bone marrow

患病后，受損細胞會在血液和骨髓里不斷復制，

until they take up all available space and resources.

直到它們侵占所有空間和資源。

When the bone marrow can no longer produce the required amount of functional cells, the blood becomes depleted.

當骨髓不能產(chǎn)生足夠數(shù)量的功能正常的細胞時，血液便枯竭了。

The lack of red blood cells means that muscles don't get enough oxygen,

紅血球的缺乏意味著肌肉得不到足夠的氧氣，

the reduced number of platelets is not sufficient to repair wounds,

血小板數(shù)量的減少也使得傷口難以修復，

and the dearth of functional white blood cells impairs the immune system, increasing the risk of infections.

而功能性白細胞的缺乏降低了免疫力，增加了受感染的風險。

To restore the normal function of the blood, leukemic cells have to be eliminated.

要重建正常的血液系統(tǒng)，白血病細胞需要被清除。

But because leukemias are not solid tumors, they can't be removed surgically.

但因為白血病并非實體瘤，所以它無法通過手術切除。

Instead, the cells are killed inside the body using various treatments that include chemotherapy,

不過存在許多其他方法能消滅體內(nèi)的白血病細胞，包括化療，

a combination of drugs that destroys quickly multiplying cells.

也就是一系列藥物，可殺死快速復制的細胞。

Unfortunately, this has the side effect of killing healthy cells, such as those found in hair follicles or intestines.

遺憾的是，這種療法也會殺死健康的細胞，例如毛囊或腸道。

And in some cases, the dosage required is so high that it kills all cells in the bone marrow, including stem cells.

有一些情況下，化療需要的藥量很大，會殺死骨髓里全部的細胞，包括干細胞。

When this happens, the body is no longer able to create new blood cells on its own.

這種情況下，身體無法自己產(chǎn)生新的血細胞。

Fortunately, outside help can come in the form of stem cells from the bone marrow of a donor.

幸運的是，干細胞可以從他人中獲得，也就是骨髓捐獻者。

Once transplanted into the patient, they rapidly repopulate the bone marrow and the blood.

當骨髓被移植到患者身體后，它會迅速產(chǎn)生骨髓和血液。

However, bone marrow transplants are a complicated process requiring antigen compatibility between the donor and recipient

然而，骨髓移植的過程很復雜，它要求捐獻者和患者間的抗原能夠匹配，

to keep the transplanted cells from from attacking the patient's own cells as foreign bodies.

這樣才能防治移植的細胞攻擊患者自身。

Unlike with blood transplants, there are thousands of HLA types,

細胞與輸血不同，HLA（人類白細胞抗原）有幾千種，

and even siblings and close relatives may not have compatible bone marrow.

甚至患者與兄弟姐妹、近親的HLA都不一定能相容。

If this is the case, the search is expanded to a database

這時，就得在數(shù)據(jù)庫進行搜尋，

containing the genetic makeup of millions of voluntary bone marrow donors.

數(shù)據(jù)庫錄入了數(shù)百萬骨髓捐獻者的基因。

The more potential donors there are, the more patients lives can be saved through successful transplants.

骨髓捐獻者越多，能通過骨髓移植被救治的患者就越多。

Leukemia may be a frightening disease, but there is strength and hope in numbers.

白血病固然可怕，但人多，力量和希望就大。