HEALTH REPORT - Scientists Learn More About How Cancer Sprea

HEALTH REPORT - Scientists Learn More About How Cancer Spreads
By Cynthia Kirk

Broadcast: Wednesday, December 14, 2005

I'm Faith Lapidus with the VOA Special English Health Report.

Scientists have learned more about the way cancer spreads from one place in the body to another. Once it spreads, it gets more difficult to treat.

 
xeno cancer cells
Cancer is a disease of uncontrolled cell growth. Traditional thinking is that cells simply break off the main cancer, travel through the blood and grow in other organs.

But the new findings suggest there is more to this process. Researchers found that cells from the main tumor¹ send out messengers. These prepare the new organ for a secondary tumor.

It works this way. The primary tumor releases proteins called growth factors into the blood. They signal cells at the target organ to produce a sticky protein, called fibronectin. Fibronectin attaches to the surface of bone marrow² cells. The result is a kind of landing area for cancer to arrive and grow into a secondary tumor.

The bone marrow cells help make vessels³ for blood to pass through and feed the cancer cells. The researchers believe that without the bone marrow cells, the tumors could not land on the new organ and grow.

Scientists from Cornell University in Ithaca, New York, led the research. The study appeared in the publication Nature. It involved laboratory mice. The researchers killed off bone marrow cells in the animals and replaced them with special new ones. The bone marrow cells were brightly colored, so the researchers could observe them. The mice were then injected with lung cancer cells.

The researchers were surprised when the bone marrow cells reached the lungs days before any cancer cells. They found that the bone marrow cells arrived to prepare the lungs for the cancer to spread. Other tests led to similar findings.

The researchers believe they would find the same results in humans. They say knowledge of the process could lead to new ways to fight cancer.

Cancers can be caused by genetic⁴ or environmental conditions, or a combination. There are estimates that about one-third of cancer deaths could be prevented if people took better care of themselves. That includes better diet, exercise and no smoking.

Researchers recently studied the causes of the seven million cancer deaths worldwide in two thousand one. They linked nine avoidable risks to almost two and one-half million of them. The study led by Harvard researchers in the United States appeared in the Lancet.

This VOA Special English Health Report was written by Cynthia Kirk. I'm Faith Lapidus.

1 tumor   

n.（肿）瘤，肿块(英)tumour

参考例句：

• He was died of a malignant tumor.他死于恶性肿瘤。
• The surgeons irradiated the tumor.外科医生用X射线照射那个肿瘤。

2 marrow   

n.骨髓；精华；活力

参考例句：

• It was so cold that he felt frozen to the marrow. 天气太冷了，他感到寒冷刺骨。
• He was tired to the marrow of his bones.他真是累得筋疲力尽了。

3 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

4 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。