Can A Virus Cause Cancer: A Look Into The History And Significance Of Oncoviruses

Abstract

C an A V irus C ause C ancer ? A L ook into the H istory and S ignificance of O ncoviruses Niema Rwazavian T he I mportance of O ncoviruses Cancer, a disease caused by unregulated cell growth, is often attributed to chemical carcinogens (e.g. tobacco), hormonal imbalances (e.g. high levels of estrogen), or genetics (e.g. breast cancer susceptibility gene 1). While cancer can originate from any number of sources, many people fail to recognize another important etiology: oncoviruses, or cancer-causing (van Epps 2005). Although many in the scientific community were unconvinced of the role of viruses in cancer, research on the subject nevertheless continued. In 1933, Richard Shope discovered the first mammalian oncovirus, cottontail rabbit papillomavirus (CRPV), which could infect cottontail rabbits, and in 1936, John Bittner discovered the mouse mammary tumor virus (MMTV), which could be transmitted from mothers to pups via breast milk (Javier and Butle 2008). By the 1960s, with the additional “…despite limited awareness, oncoviruses are discovery of the murine leukemia (MLV) in mice and the SV40 nevertheless important because they represent virus in rhesus monkeys, researchers virus over 17% of the global cancer burden.” began to acknowledge the possibility that viruses could be linked to human cancers as well. The growing concern viruses. Oncoviruses are often overlooked because over the possibility of human cancer viruses lead to current preventative measures against cancer focus the creation of the U.S. Special Virus Cancer Program on modifiable lifestyle risk factors, such as diet and in 1964, which was devoted to the search for human exercise. Despite limited awareness, oncoviruses oncoviruses. are nevertheless important because they represent over 17% of the global cancer burden (Parkin 2006). discovered the first mammalian oncovirus, cottontail Studies have demonstrated that if these pathogens rabbit papillomavirus (CRPV), which could infect were eliminated, there would be 23.6% fewer cases of cancer in developing countries and 7.7% in developed countries, leading to a Preduction of 1.5 million and 390,000 cases of cancer per year, respectively (Parkin 2006). Given their significant yet surprising role in human cancer, oncoviruses are considered to be the second-most important risk factor after tobacco consumption for cancer development in humans (zur Hausen 1991). Currently, six viruses have been proven to cause over ten types of cancer in humans (see Table T he H istory of O ncovirus R esearch The discovery of oncoviruses dates back to the early 20th century, when in 1908 Oluf Bang and Vilhelm Ellerman, researchers at the University of Copenhagen, demonstrated that leukemia could be induced in healthy chickens by treating them with a filterable extract containing the avian leukemia virus (Javier and Butle 2008). Despite their results, the discovery of the first known tumor virus was credited to Payton Rous, who proved that the Rous sarcoma virus caused cancer in Plymouth Rock chickens B S J Figure 1. An electron micrograph of two Epstein Barr Virus virons. The dark sphere in the middle contains the virus’ genome. cottontail rabbits, and in 1936, John Bittner discovered the mouse mammary tumor virus (MMTV), which could be transmitted from mothers to pups via breast B erkeley S cientific J ournal • I nfectious D isease • F all 2010 • V olume 14 • I ssue 1 • 19