Reflections on viruses and cancer

Abstract

In recent years human and animal cancers have increasingly been shown to have a viral component in their aetiology. Oncogenic viruses will continue to be discovered although with certain cancers there is also an important environmental component, and with others--congenital cancers and cancers of early childhood--an important genetic component. There is thus the probability that 'cancer' may not be an entity. Rather it may be a syndrome, the phenotypic expression of alteration of cellular metabolism, differentiation and cell death. More information is needed on the mathematics of cell division and destruction, in vivo and in vitro, and the involvement of 'biological clocks', i.e. ageing processes. These data, when available, should help us to understand better the nature of cancer and lead us to more effective methods of prevention and cure.

Reflections on the pathogenesis of diseases caused by the acute avian leukosis/sarcoma viruses with special reference to avian erythroblastosis

“…This confirms that inflammatory disease due to oncoviruses can occur in the absence of neoplastic change and that these other changes could be the result of cell damage and death. Apoptosis, or programmed cell death, is now recognised as a component of malignancy (Bowen and Bowen, 1990;Darcel, 1994). The massive amounts of mucin produced by Rous sarcomas could be the product of cell death rather than cell secretion.…”

“…Such a filtration mechanism might also apply to the PEBLEs. Until this work is done it cannot be assumed that the accumulation of PEBLEs in the liver and spleen is 'neoplastic' and, as such, 'serving no useful purpose' (Darcel, 1994). The statement that 'ascites occurs and haemorrhages in the viscera and subcutaneous tissues are common' suggests damage to the vascular endothelium and to elements involved in blood coagulation.…”

“…Cancers are multifactorial in causation (Darcel, 1994) and disease due to the L/S viruses is no exception. Many possible factors influencing viral carcinogenesis, such as immunosuppression or presence of carcinogens and co-carcinogens and factors such as hormonal status, important in the genesis of cancers, have not been considered in this essay.…”

“…Oncogenes (Darcel, 1994) are important in cell transformation. The following is a list of the viral oncogenes (v-onc) that have a role in the pathogenesis of the diseases under consideration and that 'transform' (Darcel, 1994) …”

“…References to the early origins of many of these viruses were documented by Darcel (1960Darcel ( , 1973. Virology relating to cancer in general has been discussed by Darcel (1994).…”