Viruses are leading causes of different types of human cancers, accounting for
about 20% of total cases. Seven viruses are currently considered oncogenic
viruses, including hepatitis B virus (HBV), hepatitis C virus (HCV), human
papillomavirus (HPV), Epstein Barr virus (EBV), human herpes virus 8 (HHP8),
Merkel cell polyomavirus (MCPyV), and human T-lymphotropic virus type 1
(HTLV-1). The molecular mechanisms of viral oncogenesis are complex and
may involve the induction of chronic inflammation, disruption of host genetic
and epigenetic integrity and homeostasis, interference with cellular DNA
repair mechanisms resulting in genome instability and cell cycle dysregulation.
Genetic and epigenetic alterations induced by infection and replication of
oncogenic viruses may lead to the appearance and proliferation of cancer
stem cells, which are important for the initiation, progression, metastasis,
relapse, and chemotherapy resistance of cancers. The cover illustrates the
seven oncoviruses that could lead to human cancer.