科學家：得不得癌症 基本看運氣
這個消息可能對那些極其注重保健養生的人是個打擊，但是科學家發現，即使生活方式健康，依然有三分之二的癌症是難以避免的，因爲大部分癌症都是DNA複製時突然產生的錯誤所致。
Two thirds of cancers are unavoidable even if you live a healthy life, a study has shown.
研究表明，即使生活方式健康，依然有三分之二的癌症是難以避免的。
Scientists in the US found cancers are caused by random mistakes in the genetic code that occur when cells divide.
美國科學家發現，細胞分裂時產生的基因序列隨機錯誤能致癌。
The findings challenge the widespread view that cancer mutations are generally inherited or triggered by environmental factors.
這一發現之前，人們普遍認爲，細胞癌變通常是遺傳或者環境因素所致。
Instead, the vast majority of cancers are probably down to unlucky defects in replicating DNA that occur out of the blue, they suggest.
然而，研究人員指出，大部分癌症的發生可能都是DNA複製時突然產生的錯誤所致。
Lead scientist Dr Cristian Tomasetti, from Johns Hopkins Kimmel Cancer Center in the US, said: "It is well-known that we must avoid environmental factors such as smoking to decrease our risk of getting cancer.
美國約翰霍普金斯大學金墨爾癌症中心首席科學家克里斯蒂安•托馬塞蒂博士指出：“衆所周知，我們必須避開吸菸等環境因素從而減少罹癌的可能。”
"But it is not as well-known that each time a normal cell divides and copies its DNA to produce two new cells, it makes multiple mistakes.
“但是，很多人不知道的是，每當一個正常的細胞分裂並複製DNA從而產生兩個新細胞時，會發生各種各樣的錯誤。”
"These copying mistakes are a potent source of cancer mutations that historically have been scientifically undervalued, and this new work provides the first estimate of the fraction of mutations caused by these mistakes."
“這些細胞分裂時產生的錯誤是導致癌基因變異的重要原因，但是，一直以來，這種觀點在科學領域都未受到足夠重視。這是第一次有研究猜測認爲，癌基因的變異可能源於細胞分裂時產生的錯誤。”
The research, published in the journal Science, indicates that almost two-thirds of cancer-causing mutations are due to DNA copying errors.
這項發表在《科學》期刊上的研究表明，將近三分之二的致癌基因突變可能源於DNA複製時產生的錯誤。
The discovery helps explain why cancer often strikes people who follow all the rules of healthy living and have no family history of the disease.
這一發現有助於解釋爲何罹癌的通常是那些生活方式健康且無家族病史的人。
Cancers triggered by copying errors could occur "no matter how perfect the environment", according to co-author Dr Bert Vogelstein, also from the Johns Hopkins Kimmel Cancer Center.
同樣來自美國約翰霍普金斯大學金墨爾癌症中心的伯特•沃格斯坦博士是本次研究論文的共同著者，他表示，“不管外部環境多麼無可挑剔”，由基因複製錯誤導致的癌症都有可能發生。
He said: "We need to continue to encourage people to avoid environmental agents and lifestyles that increase their risk of developing cancer mutations.
他還提到：“我們要繼續鼓勵人們避開那些增加癌基因變異風險的環境因素和生活方式。”
"However, many people will still develop cancers due to these random DNA copying errors, and better methods to detect all cancers earlier, while they are still curable, are urgently needed."
“不過，很多人仍會因爲DNA複製時隨機產生的錯誤患上癌症，因此，我們現在急需找到更好的方法及早檢測出所有癌症，在它們還可以治癒時發現它們。”
The team studied mutations that drive abnormal cell growth in 32 different types of cancer.
研究人員對32種癌症中導致細胞異常生長的變異原因進行了研究。
Using DNA sequencing and epidemiological data, they developed a mathematical system of assessing the role of genetic copying errors in cancer.
研究人員利用DNA測序和流行病學資料，建立了數學模型，以此評估基因複製時隨機產生的錯誤在罹癌中起到的作用。
The results showed that it generally took two or more critical gene mutations to trigger cancer.
研究結果表明，一般情況下，癌症的發生至少需要兩種關鍵基因的變異。
In some cancer types, such as those affecting the prostate, brain and bone, more than 95% of the harmful mutations were due to random DNA copying errors.
在部分癌症種類中，例如前列腺癌、腦癌和骨癌等，至少95%的有害突變是DNA複製時隨機產生的錯誤所致。
Copying mistakes were linked to 77% of pancreatic cancers but only 35% of lung cancers, which were mostly triggered by smoking and other environmental factors.
雖然77%的胰腺癌和DNA複製時產生的錯誤有關，但是，這種錯誤造成的肺癌比例僅爲35%，吸菸等環境因素纔是引起肺癌的主要原因。
Overall, 66% of cancer mutations resulted from copying errors, 29% from lifestyle or environmental factors, and just 5% from inherited faulty genes.
整體而言，在引起細胞癌變的衆多原因中，細胞分裂時產生的錯誤佔比66%，生活或環境因素佔比29%，異常基因遺傳佔比僅爲5%。
The researchers compared DNA copying errors to "typos" in a written manuscript.
研究人員將細胞分裂錯誤比作書稿上的“打字錯誤”。
"You can reduce your chance of typographical errors by making sure you're not drowsy while typing and that your keyboard isn't missing some keys," said Dr Vogelstein.
沃格斯坦博士表示：“打字的時候我們可以通過確保自己意識清醒、鍵盤上的鍵沒有缺漏，來減少拼寫錯誤。”
"But typos will still occur because no-one can type perfectly."
“但是，打錯字的情況仍會出現，畢竟，誰也做不到一字不錯。”
Professor Mel Greaves, director of the Centre for Evolution and Cancer at The Institute of Cancer Research in London, said: "Even if, as this study suggests, most individual cancer mutations are due to random chance, the researchers admit that the cancers they cause may still be preventable.
倫敦癌症研究所進化與癌症中心董事梅爾•格里夫斯教授表示：“雖然正如這項研究顯示的那樣，大多數癌基因變異是因爲細胞分裂時隨機產生的錯誤所致，但是，研究人員也承認說，這種癌症或許也能預防。”
"We have good evidence to show that cancer is caused by a complex mix of environmental exposures, inherited risk, and random chance.
“我們有充分證據表明，癌症的發生是環境因素、遺傳風險以及細胞分裂時隨機產生的錯誤這三種因素共同所致。”
"And while the genes we inherit from our parents are unreturnable and many chance events are non-negotiable, fortunately for us, exposures are major contributors to our risk of cancer and offer a route to risk reduction or prevention."
“另外，雖然我們無法改變從父母那裏遺傳的基因，很多偶然事件也無法避免，但是所幸，環境因素是導致我們患上癌症的主要原因，憑這一點，我們也能降低或防範自己罹癌的風險。”
