Chapter 11 - Evolution of viruses: tumor complications

Abstract

Oncoviruses, which have genetic material and protein layers called tumor viruses, contain both DNA and RNA that have the capacity to cause human cancer, but DNA oncoviruses stands responsible to cause higher infection compared to RNA oncoviruses. When the oncoviral DNA enters the genome of humans, it will convert the healthy cells into infected cells that cause cancer. There are two major types of the protein associated with this mechanism: tumor proteins (p53) and retinoblastoma. Worldwide, about 15%–20% of all the human cancer occurs due to oncoviruses. It is classified into six distinct families of animal viruses. Hhv4, also termed the Epstein-Barr virus, is capable of infecting the human body through saliva. The hepatitis B virus, which belongs to the Hepadnaviridae family, it infects through several fluids and causes severe lung infections and leads to cancer; still no proper treatments are available for this, although prevention can be done by particular vaccines. Hepatitis C virus (HCV) is transmitted from person to person through blood contact, Human herpesvirus 8 affects people having weak immunity and with HIV. Human T-lymphotropic virus 1 is the foremost tumorigenic retrovirus affecting humans; it causes cancer and can be spread through bodily fluids and breast milk. Human papillomavirus can spread through sexual contacts; it causes cancer in both males and females through genital warts. Olaf Bang and Vilhelm Ellermann discovered the theory of cancer-causing viruses through experiments in 1908; they also experimented with the avian erythroblastosis virus, which is associated with leukemia and other cancers in animals. In 1911, Peyton Rous discovered the avian virus, also known as bird flu, which causes tumors in chicken. The mammalian tumor virus was distinguished in 1930 by Richard Shope and John Bittner. In the 1960s, 1970s, 1980s, and 1990s, breakthroughs occurred in terms of various human hepatitis viruses RNA viruses that contribute to cancer are HCV and HLVT-1. Epidemiological data and experiments have shown that cancer caused by virus is the second most risk factor that occurs in the human population. This cancer can be transferred through various mechanisms, such as oncogenes; it can be transmitted directly into the infected cells. The tumors caused by the virus are closely associated with oncogenic diseases. These tumor viruses can be prevented by vaccines, such as vaccine against hepatitis B. Oncolytic virotherapy exploits viruses with discriminating tropism for neoplastic tissues and cells for treating cancer. These can be used as biomarkers with potential application for increased diagnostics, faster screening, and providing researchers with the ideology of treating cancer.