Chemical-viral interactions and multistep aspects of cell transformation.

This review provides evidence that cell culture systems can be used to demonstrate synergistic interactions between chemical carcinogens, tumour promoters and a viral agent in the transformation of mammalian cells. In addition, these systems provide evidence that the transformation of individual clones is a multistep, progressive process. Tissue culture systems should prove highly useful, therefore, for studying the possible synergistic interaction between environmental chemicals and specific viruses in the causation of certain human cancers. It is possible, for example, that the failure far to demonstrate conclusively the viral etiology of human cancers may be due to the fact that putative viruses cause cancer only via synergistic interactions with chemical carcinogens, tumour promoters, hormones or other cofactors. Hopefully, cell culture will facilitate studies on the role of interactions of multiple factors in the causation of human cancer and lead to an understanding of the fundamental mechanisms underlying tumour promotion and progression.