RNA-tumour-virus genes and transforming genes: patterns of transmission

Abstract

RNA tumour virus genes are contained in the chromosomal DNA of most vertebrates, and may be transmitted vertically from parent to progeny along with other cellular genes, as well as horizontally as infectious particles. Activation of these viral genes may be part of the means by which RNA tumour viruses produce cancer. Viral genes and their possible gene products have been characterized. The envelope glycoprotein, for example, interacts with specific membrane receptors on cell surfaces and the major phosphoprotein binds to specific viral RNA sequences. Type-C viral gene sequences have evolved as the species have evolved, and have been transferred between distantly related species under natural conditions. The presence of genetically transmitted viral genes in several vertebrate species, including primates, and the evidence that they may provide normal functions beneficial to the species carrying them, suggests that the potential to cause cancer is a pathological manifestation of a normal physiological process. Images Fig. 4

Norepinephrine modulates the growth‐inhibitory effect of transforming growth factor‐beta in primary rat hepatocyte cultures

“…The role of peptide growth factors in this process has taken on great significance with the identification of oncogenes that encode growth factors or their receptors. In addition, the discovery that transformed cells in culture often secrete growth factors into their medium has strengthened the autocrine hypothesis of tumor growth in which malignant cells secrete and respond to their own growth factors (Todaro and DeLarco, 1978).…”

Radiation leukaemogenesis: is virus really necessary?

“…Two recent reviews by Todaro (1978) and Klein and Klein (1977) both stress the generality of strong TATA for virally transformed cells, and thus the role of immunological surveillance in the control of such neoplasms. Klein and Klein made a strong case for the commonly investigated AKR leukaemia having been engineered by selection in the laboratory, and thus exceptional.…”

Cancer and Subversion of Host Defences

“…(1980). These findings do not detract from the possible importance of changes in macrophage function in malignant disease because: (a) different malignant cells may use different mechanisms to induce similar effects; (b) the presence of RNA tumour virus genes (virogenes or oncogenes) and thus of their gene products may be a common factor in many different types of malignant cell (Todaro, 1978); (c) even a known virus-induced neoplasm (a Friend leukaemia) may exert an immunosuppressive effect via both viral and non-viral factors (Ting et al, 1979).…”