如今，全世界每七个死亡案例中就有一个是死于癌症。 Today cancer causes one in every seven deaths worldwide.
但是，癌症是如何开始的， But how does cancer start,
我们又采取了什么措施抗击癌症呢？ and what is being done to combat it?
我们的身体含有数以万亿计高度特化的细胞， Our bodies contain trillions of highly specialized cells
并且每个细胞都携带着基因 and each carries genes responsible
负责调控细胞生长和细胞分裂。 for regulating cell growth and division.
但是当遗传改变打乱这个进程时， But when a genetic change disrupts this process
细胞就开始不受控制地生长和分裂， cells begin to grow and divide uncontrollably
从而形成了癌症。 thereby becoming cancer.
导致癌症的遗传改变通常发生在三种类型的基因中。 The genetic changes that cause cancer usually happen in three types of genes.
原癌基因，向细胞发出生长和分裂的信号。 Proto-oncogenes, which signal a cell to grow and divide.
肿瘤抑制基因，向细胞发出停止分裂的信号。 Tumor suppressor genes, which signal a cell to stop dividing.
以及DNA修复基因，它们能够保存并维持基因序列稳定。 And DNA repair genes, which preserve and maintain genetic codes.
这些基因的改变会导致细胞生长异常， Changes in these genes lead to abnormal cell growth
从而导致“组织块”的出现，这就是肿瘤。 resulting in masses of tissues called tumors.
肿瘤可能是良性的，也就是说它们只存在于一个区域， Tumors may be benign, meaning that they remain in one area,
也可能是恶性的，意味着它们能够扩散。 or malignant, which means that they are capable of spreading.
通过一种叫“转移”的方式， Through a process called metastasis
恶性肿瘤细胞最终将会脱落， a malignant tumor's cells will eventually break off,
在全身游走， travel throughout the body,
然后开始在身体其他部位形成新的肿瘤 and begin forming tumors in other regions.
当这种情况发生时，癌症就变成了转移性的， When this happens the cancer has become metastatic
并且最为凶险。 and is most dangerous.
产生癌症的原因仍然是个谜。 The cause of cancer is still a mystery.
在某些遗传改变的背后， Inherited traits may be behind some of the genetic changes
遗传因素可能是导致癌细胞形成的元凶， that lead to the formation of cancerous cells,
环境暴露也可能是原因之一。 and so might environmental exposures.
例如暴露于过度的太阳辐射， Such as excessive radiation from the sun,
或香烟的化学物质中。 or chemicals in cigarette smoke.
在如今的美国，大约三分之一的人 In the United States today roughly one-third of all people
最终会患上癌症。 will eventually develop cancer.
在100多种不同类型的癌症中， Of the over 100 different types of cancer
乳腺癌是目前最常见的类型， breast cancer is currently the most prevalent type,
肺癌导致的死亡人数最多。 and lung cancer causes the most deaths.
但是我们对抗癌症的能力正在提高。 But our ability to fight cancer is improving.
自上世纪90年代以来，美国癌症死亡率 Since just the 1990s cancer mortality rates
下降超过26%， have dropped more than 26% in the US,
超过两百万人的生命得到拯救。 and more than two million lives have been saved.
随着治疗方法和早期发现能力的提高、 As treatments and methods of early detection improve,
医生、科学家以及大众 and doctors, scientists, and the public
对癌症有了更好的了解， better understand cancer,
与癌症的斗争仍充满了希望！ hope remains in the fight against the disease.
医课：译员LOIS