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Introduction Discovery of viruses History What is cancer How viruses cause cancer Growth of cancer cells Classification of oncogenic virus Mechanism of oncogenic virus Drugs used to treat oncogenic viruses Precautions to prevent infection during cancer treatment Conclusion References
CONTENTS
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An oncovirus is a virus that can cause cancer. This term originated
from studies of acutely transforming retroviruses in the 1950–60s,
often called oncornaviruses to denote their RNA virus origin.
Now refers to any virus with a DNA or RNA genome causing
cancer and is synonymous with "tumor virus" or "cancer virus".
The vast majority of human and animal viruses do not cause
cancer, probably because of long-standing coevolution between the
virus and its host.
INTRODUCTION
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Worldwide, the WHO International Agency for Research on
Cancer estimated that in 2002, 17.8% of human cancers were
caused by infection, with 11.9% being caused by one of seven
different viruses.
The importance of this is that these cancers might be easily
prevented through vaccination (e.g., papillomavirus vaccines),
diagnosed with simple blood tests, and treated with less-toxic
antiviral compounds.
CONT...
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1908: Vilhelm Ellerman and Olaf Bang, University of
Copenhagen, first demonstrated that avian sarcoma leukosis
virus could be transmitted after cell-free filtration to new
chickens, causing leukemia.
1933: Richard Edwin Shope discovered cottontail rabbit
papillomavirus or Shope papillomavirus, the first mammalian
tumor virus.
1957: Sarah Stewart and Bernice Eddy discovered polyoma
virus.
DISCOVERY OF VIRUSES
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1964: Anthony Epstein, Bert Achong and Yvonne Barr identify the
first human oncovirus from Burkitt lymphoma cells. A herpesvirus,
this virus is formally known as human herpesvirus 4 but more
commonly called Epstein-Barr Virus or EBV.
1980: Human T-lymphotropic virus 1 (HTLV I), the first human
retrovirus was discovered by Bernard Poiesz and Robert Gallo at NIH
and Mistuaki Yoshida and coworkers in Japan.
2008: Chang and Moore, now at the University of Pittsburgh Cancer
Institute, developed a new method to identify cancer viruses based on
computer subtraction of human sequences from a tumor
transcriptome, called digital transcriptome subtraction (DTS).
DISCOVERY OF HUMAN ONCOVIRUSES
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The theory that cancer could be caused by a virus began with the
experiments of Oluf Bang and Vilhelm Ellerman in 1908 who
first show that avian erythroblastosis (a form of chicken
leukemia) could be transmitted by cell-free extracts. This was
subsequently confirmed for solid tumors in chickens in 1910-
1911 by Peyton Rous.
By the early 1950s it was known that viruses could remove and
incorporate genes and genetic material in cells. It was suggested
that these new genes inserted into cells could make the cell
cancerous. Many of these viral oncogenes have been discovered
and identified to cause cancer.
HISTORY
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Cancer results from alterations in critical
regulatory genes that control cell proliferation,
differentiation, and survival. Studies of tumor
viruses revealed that specific genes (called
oncogenes) are capable of inducing cell
transformation, thereby providing the first
insights into the molecular basis of cancer.
WHAT IS CANCER
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The viral agents causing cancer in eukaryotic animals by integrating in host genome.
A virus associated with malignancies in natural host, experimental animals or cell cultures.
viruses which modified proto- oncogene, obligatory host specific, with the ability immortalization, possess genes which stimulate growth and cause cancer.
HOW VIRUSES CAUSE CANCER
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Human papilloma virus (HPV), a DNA virus, causes transformation
in cells through interfering with tumor suppressor proteins such as
p53.
Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) is
associated with Kaposi’s sarcoma, a type of skin cancer.
Epstein-Barr virus (EBV or HHV-4) is associated with four types of
cancers.
Merkel cell polyomavirus – a polyoma virus – is associated with the
development of Merkel cell carcinoma.
Human cytomegalovirus (CMV or HHV-5) is associated with
mucoepidermoid carcinoma and possibly other malignancies.
DNA ONCOGENIC VIRUSES
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Not all oncoviruses are DNA viruses. Some RNA viruses have
also been associated such as the hepatitis C virus as well as
certain retroviruses, e.g., human T-lymphotropic virus (HTLV-1)
and Rous sarcoma virus (RSV).
RNA ONCOGENIC VIRUSES
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VirusPercent of
cancersAssociated cancer types
Hepatitis viruses, including hepatitis B (HBV) and hepatitis C (HCV)
4.9Hepatocellular carcinoma (liver cancer).
Human T-lymphotropic virus (HTLV) 0.03 Adult T-cell leukemia
Human papillomaviruses (HPV) 5.2Cancers of cervix, anus, penis, vulva/vagina, and oropharyngeal cancer.
Kaposi’s sarcoma-associated herpesvirus (HHV-8)
0.9Kaposi’s sarcoma, multicentric Castleman's disease and primary effusion lymphoma
Merkel cell polyomavirus Not available Merkel cell carcinoma
Epstein–Barr virus (EBV) Not available
Burkitt’s lymphoma, Hodgkin’s lymphoma, Post-transplant lymphoproliferative disease and Nasopharyngeal carcinoma.
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Wash your hands after using the bathroom, blowing your nose,
coughing, or sneezing.
Wash your hands after touching animals, collecting trash, or
taking out garbage.
Use moist cleaning wipes to clean surfaces and things that you
touch, such as door handles, ATM or credit card keypads, and
any items that are used by other people.
Stay away from anyone with a fever, the flu, or other infection.
PRECAUTIONS TO PREVENT INFECTION DURING CANCER TREATMENT
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Do not wade, play, or swim in ponds, lakes, rivers, or water
parks.
Wear shoes all the time — in the hospital, outdoors, and at
home. This helps you avoid injury and keep germs off your
feet.
Do not keep fresh flowers or live plants in your bedroom.
Use hot water to clean your dishes.
CONT…
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Globally, almost 20% of cancers are related to infection agents.
Several viruses with oncogenic potential stimulate cell proliferation
and cause tumors and cancer in animals and humans. They act with
different mechanisms depending on different factors.
The tumor viruses with small genomes integrate into host cell
chromosomal DNA and cause mutations and chromosomal
rearrangements that predispose to cancer. The oncogenic DNA and
RNA viruses that are carrying oncogenes encode transforming
proteins to stimulate tumor formation.
CONCLUSION
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1. Murat ŞEVİK, Laboratory of Molecular Microbiology,
Veterinary Control Institute, Konya – TURKEY, Oncogenic
viruses and mechanism of oncogenesis, 2012; 36(4): pg.
no.323-329.
2. Parkin, Donald Maxwell (2006). "The global health burden
of infection-associated cancers in the year 2002".
International Journal of Cancer, 118 (12): pg. no.3030–44.
3. Oncovirus, from wikipedia, the free encyclopedia.
REFERENCES
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