The quest for human cancer viruses

A new approach to the important but difficult task of revealing possible human tumor viruses has been presented in this article. By systematic testing of already known human viruses for oncogenic properties, it was found that in hamsters injected intrapulmonarily with tissue culture fluid of human type 12 adenovirus within 24 hours after birth there was a very high incidence of malignant tumors at the site of injection in from 1 to 3 months. The tumorinducing activity was not lost by filtration through Selas 02 filters or by tissue culture passages in HeLa cells. Tumors thus induced grew in, and killed, a high percentage of the unconditioned young adult hamsters into which they were transplanted. No such tumors occurred in hamsters injected with control tissue culture fluid or with culture fluids of the other viruses tested, or in control breeder hamsters. The possibility that contamination with polyoma virus and simian virus 40 might be responsible for the tumors induced was specifically excluded by a variety of tests. The possible involvement of still other, as yet unknown, contaminant viruses was excluded by a positive association of the tumor-inducing ability with the adenovirus content. Of eight human sera tested, only those four which neutralized the adenovirus-type cytopathic effect also neutralized the tumor-inducing effect. Of 700 human sera tested, 26 percent contained CPE-neutralizing antibodies for type 12 adenovirus at titers of 1:4 and higher (23).