Abstract
Members of four different groups of animal viruses are known to cause cancer in animals. (Only two of them, the leukoviruses and herpesviruses, cause cancer in nonlaboratory situations.) All the members of these groups of viruses form integrated viral DNA in infected cells. However, the efficiencies with which they cause cancer vary by over a dozen orders of magnitude. These differences in efficiency are a result of differences in efficiency of formation and expression of the genes for neoplastic transformation. Four models of mechanisms for formation of the genes for neoplastic transformation are presented. Two involve the formation of new DNA sequences. No efficient human cancer‐causing viruses are known. Therefore, it is proposed that human cancer is a result of formation of the genes for neoplastic transformation by misevolution of a normal cellular information transferring process. This misevolution is caused by chemicals, physical agents, or viruses.
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