Oncogenic Role of Tumor Viruses in Humans

Abstract

Viruses are the intracellular pathogens that reproduce only in the living cell and manipulate the cellular machinery to produce more viruses. Viral replications can affect cellular genes of the host in multiple cancerous ways. Approximately, 20% of all human oncogenesis is caused by cancer-causing viruses known as oncoviruses. Viral infection causes chronic inflammation leading to cell death, uncontrollable proliferation, and modulated expression of some of the regulatory proteins. Oncogenesis is a multistep phenomenon in which normal host cells are transformed into cancerous cells on the basis of host genetic variability. Oncogenic viruses encode genes that cause viral replication and transformation of the host cells to produce viral proteins and protein complexes. The phenomenon from basic viral infection to tumorigenesis is lengthy due to the involvement of factors like immunity complications, cellular mutations, and exposure to other cancerous agents. The viruses that are involved in human cancer development are Hepatitis B virus (HBV), Hepatitis C virus (HCV), Epstein-Barr virus (EBV), Human papilloma virus (HPV), Kaposi's sarcoma herpes virus (KSHV), and Human T lymphotrophic virus 1 (HTLV-1). This review article summarizes advanced knowledge related to human oncogenic viruses and the molecular mechanisms that lead to tumorigenesis in humans.

Regulation of Autophagy in Cells Infected With Oncogenic Human Viruses and Its Impact on Cancer Development

“…Hepatitis B virus (HBV) and hepatitis C virus (HCV) are involved in approximately 80% of human hepatocellular carcinoma (HCC). Epstein-Barr virus (EBV), human herpesvirus 8 (HHV8), and human T-lymphotropic virus 1 (HTLV-1) showing lymphocytes tropism (Akram et al, 2017) are human viruses directly associated with cancer development. All these viruses encode genes essential for viral replication, which transform the host cells leading to chronic inflammation, uncontrolled proliferation, and the alteration of several cellular pathways, which are responsible for malignant transformation depending on the host genetic background and immune system response ( Table 1).…”

Hepatitis B and C virus infection and risk of haematological malignancies

“…Approximately 20% of human cancers can be related to infectious agents, including viruses, bacteria and parasites . Hepatitis B virus (HBV) and hepatitis C virus (HCV) together with Epstein‐Barr virus (EBV), Kaposi's sarcoma herpes virus (KSHV), human immunodeficiency virus, type‐1 (HIV‐1), human T cell lymphotrophic virus, type‐1 (HTLV‐1) and some types of human papillomavirus (HPV) are classified as Group 1 oncogenic human viruses according to the International Agency for Research on Cancer (IARC) …”

Deregulation of the Notch pathway as a common road in viral carcinogenesis

“…Viruses are pathogens that manipulate and take advantage of the host's cellular machinery for their replication . Some infections are considered biological carcinogens .…”

“…Tumor viruses include hepatitis B and C viruses (HBV and HCV respectively), Epstein‐Barr virus (EBV), Kaposi sarcoma‐associated herpesvirus (KSHV), human papillomavirus (HPV), human T lymphotropic virus (HTLV‐1), and Merkel cell polyomavirus (MCPyV) . A common feature among them is their ability to cause persistent infections in the host cell and the deregulation of key cellular pathways such as Wnt, Akt/PI3K, NF‐kB, and Notch, promoting cancer …”

“…As abovementioned, several cell pathways are hijacked by oncogenic viruses to cause transformation, and many of those crosstalk with Notch. Wnt signaling, just as the Notch signaling pathway, is known for its role in determining cell fate .…”