Introduction

Abstract

Cancer is a large group of diseases representing the outcome of highly diverse patterns of dysfunction of cellular homeostasis, as was discussed in some detail in Chapter 7 and the Prefatory Chapter. Crucial advances in the last three decades, that led to an explosively growing understanding of the induction of cancer in animals and humans, came from studies on tumor viruses. This is because through the discovery of oncogenes these studies opened an ever-expanding vista on the functioning of the genome and of the network of normal cellular regulatory pathways (including more recently the tumorsuppressor genes) which maintain normal cellular homeostasis. Hence, the significance of these studies far supersedes the scope of viral tumorigenesis proper as they will probably lead to the elucidation of the mechanisms of action of all types of carcinogenic agents.