Viruses may cause up to 40 percent of cancers including brain tumours and leukaemia, scientists claim.
If they are proved correct in further tests, it could pave the way for vaccinations against several types of cancer and therapies to cure them. The claim follows research which has discovered viruses in types of cancer which were never thought to have been linked with infection.
It has been known for decades that viruses cause some types of cancer but it was thought to be only 10 to 20 percent of cases.
The best known are the hepatitis B and C bugs, which can cause liver cancer, and the human papilloma virus (HPV) which can cause cervical cancer.
Nobel Prize winner Harald zur Hausen, who jointly discovered the link between cervical cancer and HPV in the 1980s, said he expected more discoveries to follow and suggested that viruses could be involved in cancer of the skin, breast, gut and lungs.
But scientists warn it could take a long time and huge investment before vaccines are developed.
Alan Rickinson, professor of cancer studies at Birmingham University, said: "If we can understand how these viruses work we could prevent people from contracting them and even create therapies that use the patient's own immune system to destroy infected or cancerous cells."
The process still confounds experts because viruses work by invading cells and making them produce more viruses. But this process then kills the cell which should mean it cannot become cancerous. One theory is that cancer-causing viruses can remain hidden in cells for years, preventing the cell from repairing mutations.
据英国《每日邮报》10月17日报道，科学家称包括脑肿瘤和白血病在内，有百分之四十的癌症可能由病毒引起。
如果该观点得到进一步的证实，那么将为研发癌症预防疫苗和新疗法铺平道路。这项声明是通过研究几种癌病变中发现的病毒后所作出的，此前从未设想过这些病毒具有传染性。
几十年来，病毒会引发某些类型的癌症已众所周知，但这种案例被认为仅占10%-20%。
最出名的就是会引发肺癌的乙型肝炎和丙型肝炎病毒，以及引发子宫颈癌的人类乳头瘤病毒。
诺贝尔奖得主哈拉尔德-楚尔-豪森说他希望能有更多的新发现并建议将病毒引发癌病变的研究扩展到皮肤、乳房、肠道以及肺部。哈拉尔德在20世纪80年代（与两位法国医学家）曾参与了子宫颈癌与人类乳头瘤病毒之间联系的研究发现。
但是科学家们警告，在疫苗研发出来之前将会等待很长时间以及做出巨大的投资。
伯明翰大学癌症研究所的教授艾伦-瑞金森说；"如果我们能知晓这些病毒的工作原理，就能阻止人们接触此类病毒染病，甚至能开创新疗法，利用病人自身的免疫系统破坏受感染或是癌变的细胞。
病毒引发癌变的过程仍然困扰着专家们，因为病毒是通过入侵细胞并使之分裂更多的病毒来工作的。但这一过程随后会杀死该细胞，这意味着它是不可能发生癌变的。有一种理论认为引发癌病变的病毒会潜伏在细胞之中达数年之久，阻止细胞修复变异。
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