３８種類のがんの全遺伝情報を解析、数多くの新発見　国際研究

【東京ＡＦＰ＝時事】数十種類のがんのすべての遺伝情報を調べる大規模な研究の結果、がんができる仕組みの解明やより良い治療法の開発につながるとみられる数多くの新たな発見があったと、国際研究グループが発表した。（写真は資料写真）
　パンキャンサー・プロジェクトでは、１３００人以上の世界の研究者が、２８００人近くの患者から採取した３８種類のがんのすべての遺伝情報を解析する大規模な研究を行った。
　その結果、がんの直接的な原因となるいわゆる「ドライバー変異」の数と位置や、さまざまな組織で発見されたがんに驚くべき類似性があることなど、多くの新しい発見があったという。
　研究結果は６日、英科学誌ネイチャーなどのネイチャー・リサーチ出版誌に掲載された２０本以上の研究論文で発表された。がんゲノムに関する過去最大で最も包括的な研究となった。
　研究では、それぞれのがんにある数千種類の変異の組み合わせと、変異を引き起こす８０種類以上のプロセスを突き止めた。その中には、年齢に関係するものや遺伝性のもの、喫煙などライフスタイルに関係するものなどがあった。
　また、一部のがんでは、がんと診断される数十年前に初期段階に入っている場合もあり、幼少期にすでにがんが発生していたケースもあった。「このことは、早期介入に適した時期は予想以上に広いことを示している」と、英遺伝子研究機関ウェルカム・サンガー研究所のピーター・キャンベル氏は話す。
　研究では、変異のパターンとそれがどこで起きるかが分かれば、通常の診断方法では特定できないがんのおよそ１～５％を特定できる可能性があることも明らかになった。
　研究プロジェクト運営委員会のメンバーであるリンカーン・スタイン氏は、カナダのオンタリオがん研究所が発表した声明の中で、「腫瘍の原因と形成について得られた知識によって、がんの早期発見、より目的を明確にした治療法の開発、そして患者により効果の高い治療を行うための新たなツールや治療法を開発できる」と述べた。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/02/06-13:30）

A massive, decade-long study sequencing the genomes of dozens of cancers has revealed the secrets of how tumours form and may pave the way for better and more targeted treatment.
The Pan-Cancer Project brought together over 1,300 researchers globally to tackle the mammoth task of sequencing the genomes of 38 types of cancer in nearly 2,800 patients.
Their work produced a host of new discoveries -- from the number and location of so-called driver mutations that push cells to reproduce uncontrollably, to the surprising similarities between cancers found in different types of tissue.
The results were published Thursday in nearly two dozen papers in Nature and other Nature Research journals and represent the largest and most comprehensive study of whole cancer genomes ever.
With the knowledge we have gained about the origins and evolution of tumours, we can develop new tools and therapies to detect cancer earlier, develop more targeted therapies and treat patients more successfully, said Lincoln Stein, a member of the project steering committee, in a statement issued by the Ontario Institute for Cancer Research.
Among the key findings of the work is the massive variety in cancer genomes, said Peter Campbell of the Wellcome Sanger Institute, another steering committee member.
The most striking finding is just how different one person's cancer genome is from another person's, he told AFP.
The study found thousands of combinations of mutations in individual cancers, as well as over 80 processes that cause the mutations, some of them age-related and others inherited or linked to lifestyle factors such as smoking.
- 'Exciting themes' -
But within the enormous variety there were exciting themes, Campbell said.
For example, the work found the early development of some cancers can occur decades before diagnosis, sometimes even in childhood.
This shows that the window of opportunity for early intervention is much wider than we expected, Campbell said.
The research also found that patterns of mutations, and where they occur, can help identify the approximately 1-5 percent of cancers that cannot be identified through regular diagnostics.
A sequenced genome can even reveal occasional misdiagnosis of a cancer type.
Most work on sequencing the cancer genome has focused on the approximately two percent known as the protein-coding genes.
But the Pan-Cancer Study sequenced entire genomes, uncovering new cancer-causing driver mutations in the other 98 percent, known as non-coding genes.
The researchers found enormous variation in the number of mutations in a given cancer, from very few in some cancers seen in children, to up to 100,000 in lung cancer samples.
And in around five percent of cases, no known driver mutations were found at all, implying there are mutations that have not yet been identified.
- 'Enormous spectrum' -
The sequencing helps map out the many types of mutations -- from changes in single DNA letters to much larger insertions or deletions of genetic code -- that can cause cancer.
It also revealed that cancers in different parts of the body are sometimes much more alike than had been thought.
We may have a type of breast cancer and prostate cancer where the driver mutations are similar, said Joachim Weischenfeldt, a co-author and associate professor at the University of Copenhagen.
This means that the patient with prostate cancer may benefit from the same treatment as the one you would give the breast cancer patient, he said in a statement issued by the university.
In practical terms, the findings will help identify difficult-to-diagnose cancers, allow more targeted treatment based on the specific driver mutations behind a particular cancer, and potentially allow earlier diagnosis of developing tumours.
We are finding that cancer represents the far end of an enormous spectrum of change, said Campbell.
If we can understand the forces at play in our normal organs as we age, what causes mutations to accumulate, what causes some clones to expand and others to fade, what lifestyles do to tilt this balance, then we can think about ways to intervene early, with a view to preventing or slowing the emergence of untreatable cancers.