Scientists have found two new genetic variations that appear to increase the risk of the most common skin cancer among people of European descent.

    The variations play no role in skin color but people with both of them are nearly three times more likely to develop basal cell carcinoma compared with people without the changes, researchers from Iceland's Decode Genetics said on Sunday.

    Darker skin is traditionally regarded as an important protection against skin cancer.

    "Here we have two variants that have no impact on pigmentation and only affect the risk of basal cell carcinoma," Kari Stefansson, Decode's chief executive, who led the study, said in a telephone interview. "We don't know why that is."

    Basal cell carcinoma is the most common form of cancer worldwide, and in the vast majority of cases are thought to be caused by exposure to ultraviolet rays of the sun, according to the American Academy of Dermatology.

    Most cases are easy to treat when detected early, but in rare instances the cancer is resistant to treatment, causing damage to skin and sometimes invading bone and cartilage.

    The researchers at Decode, a biotech company hunting for new drugs using Iceland's unique gene pool dating back to the Vikings, analyzed genes of more than 30,000 people to identify the impact of the genetic variations located on chromosome 1.

    These variations differed from past genetic changes linked to basal cell carcinoma in that unlike the others they were not associated with fair skin or pigmentation.

    The study published in Nature Genetics also found that the risk of developing basal cell carcinoma was 12 times higher for people with these new variations along with the three other genetic changes already linked to the cancer.

    "Exposure to the sun has no direct impact on the genes, which add to the total risk of basal cell carcinoma," Stefansson said.

    科學家發現了兩個新的基因變異似乎增加了歐洲后裔患最常見皮膚癌的風險。

    來自冰島解碼基因機構的研究人員說，該基因變異對皮膚顏色并無作用，但與無基因變異的人群相比，有兩種基因變異的人群患皮膚基底細胞癌的機率增加近三倍。

    傳統上將較黑的皮膚視為預防皮膚癌的重要屏障。

    解碼基因機構主任、這項研究的領導人凱里-斯蒂芬森(Kari Stefansson）在一次電話采訪中說：“我們發現的這兩個基因變異對色素沉著并無作用，僅僅影響患皮膚基底細胞癌的風險。對此原因，我們不知道。”

    根據美國皮膚科學會（American Academy of Dermatology）的說法，皮膚基底細胞癌是世界范圍內最常見的癌癥，絕大部分病例被認為是由接觸太陽光的紫外線引起的。

    多數病例發現早時易于治療，但極少數病例難以治療，可引起皮膚損害，有時侵入骨頭和軟骨。

    解碼基因機構是一家利用冰島的可追溯到維京人的基因庫來搜尋新藥的生物技術公司，該機構分析了3萬多人的基因，以識別１號染色體上的基因變異的影響。

    這些基因變異與以往的與皮膚基底細胞癌有關的基因變化不同，它們與皮膚的白與黑無關。

    這篇發表在《自然遺傳學》(Nature Genetics)上的論文還發現，這兩個新的基因變異與另外其它三個與癌癥有關的基因變化并存的人群，患皮膚基底細胞癌的風險高出常人１２倍。

    斯蒂芬森說：“接觸太陽光對增加皮膚基底細胞癌總風險的基因并無直接影響。”