암의 유전성은 종류에 따라 직계 가족에서 가까운 친척, 또는 먼 친척에게까지 나타나며 특히 유방암과 전립선암은 5대까지 이어진다. 이런 사실은 1955-2002년 사이에 암으로 진단된 아이슬란드인 3만2천 명의 1-5대까지 가계를 조사한 결과 밝혀졌다.
부모-자녀-형제지간인 1대는 DNA의 50%를 공유하고 있지만 5대는 공유하는 DNA가 3.125%밖에 안 된다.
아이슬란드 총 인구 28만8천 명 거의 전부의 유전자 데이터베이스를 갖고 있는 유전연구회사 디코드 지네틱스가 실시한 이 조사 분석에 따르면 27가지 암 가운데 21가지가 정도의 차이는 있지만 유전성이 있고 이 중 14가지는 가까운 친척 사이에만 유전되는 것으로 나타났다.
특히 위암, 폐암, 대장암은 환자의 배우자에게 빈발하는 것으로 나타났는데 이는 부부가 함께 하는 생활습관이 강력한 요인으로 작용함을 시사하는 것이어서 주목된다.
전체 암 중에서 유전성이 가장 강력하게 나타난 것은 매우 희귀한 암인 구순암(口脣癌)으로 직계가족 중 이런 환자가 있는 사람은 발병률이 5배 높았다.
디코드 지네틱스 회장인 카리 스테판손 박사는 다음 단계의 연구는 이러한 암들을 촉진하는 핵심 유전자를 찾아내는 작업이 될 것이라고 말했다.
The times 2004-12-28
Cancer risk among families identified
BY MARK HENDERSON, SCIENCE CORRESPONDENT
BREAST and prostate cancer are the types of the disease that sweep most widely across extended families, research has shown.
The two tumours head the first “league” of inherited cancer, which has identified seven forms in which a person’s risk is increased when even a distant relative suffers from the disease.
People with a history of breast, prostate, lung, stomach, colon, kidney and bladder cancer among distant family members such as second cousins and great aunts have a greater risk of developing the condition, the study found.
Some degree of genetic risk appears to be involved in 21 of the 27 types studied, though in 14 of these the danger applies only to people who have a close relative with the form in question. Stomach, lung and colon cancer were also seen much more frequently among the partners of sufferers. This suggests strongly that lifestyle factors that couples tend to share have a powerful influence over these conditions.
The table sheds light on the way in which different cancers follow patterns of inheritance, and could help doctors to develop strategies for detecting, treating and preventing diverse forms of the disease.
The findings come from a major study of cancer patients and their relatives in Iceland, undertaken by the company deCODE Genetics, which has amassed a unique genetic database covering most of the island’s population of 288,000.
It examined the rates at which cancer occurred among all first to fifth-degree relatives of 32,000 patients who had cancer diagnosed between 1955 and 2002. A first-degree relative is a parent or child or sibling who shares 50 per cent of an individual’s DNA. Fifth-degree relatives, such as great-great-great grandparents, share 3.125 per cent of DNA with the patient. Details of the study are published today in the open-access journal Public Library of Science Medicine.
The influence of inherited genes on cancer is highest for rare forms such as lip tumours, in which having a first-degree relative to the disease can raise a person’s relative risk fivefold.
The increased risk, however, applies to these conditions only when the affected relative is your child, parent or full sibling: it disappears for more distant family relationships.
For cancers such as breast and prostate, a person’s relative risk compared to the general population is highest if the afflicted family member is a close relative. A raised risk remains, however, even among the fifth degree relatives of sufferers.
Kari Stefansson, chief executive of deCODE genetics, said: “The next step is to isolate the key genes contributing to the common forms of the disease and to use this to develop better medicine. At the same time it is crucial to emphasise that lifestyle and environmental factors play a very significant role in the development of cancer.”
People worried that cancer may run in their family are to have specialised centres where they can go for advice. Macmillan Cancer Relief and the Department of Health are to open three centres as part of the Government’s £50 million genetics strategy. The centres will provide testing and care for people who have a close family member who has suffered from breast, ovarian or bowel cancer.
HIGH FAMILY RISK
Meninges (tissues covering the brain)
The risks of all these cancers are at least doubled if a father, mother or sibling suffers them. Some, such as lip cancer, are very rare but have high heritability.