Chapter 7 - Role of viral human oncogenesis: recent developments in molecular approaches

Abstract

A virus that causes cancer is known as oncovirus. Approximately 12% of all cancers are caused by oncoviruses. More than 80% of human cancer casesoccur in the developing world. They have recognized seven human oncoviruses which cause cancer. Some known human oncoviruses are Kaposi’s sarcoma, human T-cell lymphtropic virus type 1, Burkitt lymphoma, human papillomavirus (HPV), Merkel cell polyomavirus (MCP), human herpesvirus 4, human herpesvirus-8 (HHV-8), and hepatitis B and hepatitis C viruses. Oncoviruses are of two types: DNA and RNA oncovirus. More than 90% of the population have been infected with Epstein–Barr virus (EBV) in adulthood, and now oncoviruses have accounted for about 20% of human cancers worldwide. According to statistics in the United States, they have estimated that women are more affected by HPV-associated cancers (83%) than men (74%). The human oncovirus EBV was recognized by herpesvirus and identified in Burkitt lymphoma cells in 1964, which is oncogenic in humans. Globally, 5.5 billion people are infected with EBV. The IARC specialized cancer agency of WHO estimated human cancer at about 17.8%, and 11.9% were caused by oncoviruses in 2002. Among 2658 samples collected from 38 different cancer types, 16% were associated with oncovirus in 2020. According to epidemiological studies, EBV is estimated to be positive in more than 90% of the world’s population. About 15–20 million people are chronic (HTLV-1) carriers, and 5% of them have chances of getting adult T-cell leukemia (ATL). Viral infection caused by hepatitis B and C affects the liver, leading to liver cancer and chronic viral hepatitis. The high infection rate of hepatitis C virus (HCV) is found in Southern Italy, Northern Africa, Mongolia, Pakistan, China, and some areas of Japan. The HCV population is divided into six genotypes (1–6) based on genetic variations between HCV isolates. Clinically, the genotype is important in predicting interferon-based therapy response. The high-rise types of HPV 16 and 18 are particularly responsible for 60%–70% of cervical cancer worldwide. At present, more or less 20 million individuals are infected worldwide. The virus discovered based on PCR technique in 1994 by Chang et al. is Kaposi’s sarcoma-associated herpes virus. The other virus discovered by digital transcriptome is MCP (MCV). Recently, biotechnology and molecular biology have developed analytical methods, such as PCR assay, PCR-ELISA, quantitative-PCR, multiplex-PCR, etc., which are used to detect or characterize pathogens like oncovirus. The current method of studies says that these cancer-causing viruses can be diagnosed and prevented through vaccination. They can be treated with less toxic antiviral compounds or diagnosed with simple blood tests.