SEMINAR PPT PRESENTATION
Transcript of SEMINAR PPT PRESENTATION
ONCOGENIC VIRUSES A REVIEW
JERRY EJE ABU
UJ/2010/NS/0755
AIM OF REVIEWThis study aims at highlighting the distribution and Epidemiology of Viruses Associated with Cancer.
OBJECTIVE OF THE REVIEW1. To highlight cancer causing viruses in human.2. To highlight the mechanisms they use to cause cancer.3. To highlight the epidemiology and distribution of these cancer causing viruses.
INTRODUCTIONViruses are only able to reproduce by entering a living cell and manipulating the
cell’s machinery to create more viruses. During the viral replication process, certain
virus’s DNA or RNA affect the host cell’s genes in ways that may cause it to become
cancerous. These viruses are known as oncogenic viruses, meaning viruses that
cause or give rise to tumors. Oncogenic viruses belong to a number of viral
families, including the RNA virus families Retroviridae and Flaviviridae and the DNA
virus families Hepadnaviridae, Herpesviridae, Poliomaviridae and Papillomaviridae
(Klein, 2002).
Some of the viruses now known or suspected of being linked to cancer in humans
include; human papilloma viruses, the Epstein-Barr virus, the hepatitis B and C
viruses, the human herpes virus 8, human immunodeficiency virus (HIV) and the
human T-lymphotrophic virus-1 (Liao, 2006).
BODY OF REVIEW
Table 1: Carcinogenic mechanisms of oncogenic viruses
Source: (International Agency for Research on Cancer, 2009)
When an oncogene is activated by mutation, the structure of the encoded protein is changed in a way that enhances its transforming activity. Many types of mutation occur in oncogenes (Rodenhuis, 1992).
GROUPS OF ONCOGENIC VIRUSES
Oncogenic viruses can be divided into 2 groups, based on their genetic
material, as DNA and RNA tumor viruses (Zheng, 2010).
Table 2: Human oncogenic RNA viruses.
Source: (Zheng, 2010) HTLV: Human T-cell leukemia virus.
Table 3: Human oncogenic DNA viruses.
Source: (Butel, 2000; Zheng, 2010; McLaughlin-Drubin and Munger, 2008; Zheng and Ou, 2009) HBV: Hepatitis B virus, EBV: Epstein-Barr virus, KSHV: Kaposi’s sarcoma-associated herpesvirus, HHV: Human herpes virus, HPV: Human papillomavirus, MCV: Molluscum contagiosum virus
Epidemiology of viruses associated with human cancerThe International Agency for Research on Cancer has comprehensively assessed
the carcinogenicity of the biological agents to humans based on epidemiological
and mechanistic evidence (IARC 2009). Seven viruses including Epstein–Barr
Virus (EBV), hepatitis B virus (HBV), hepatitis C virus (HCV), Kaposi’s sarcoma
herpes virus (KSHV), human immune deficiency virus, type-1 (HIV-1), human T
Cell lymphotrophic virus, type-1 (HTLV-1),and several types of human papilloma
virus (HPV) have been classified as Group1 human carcinogen.
PREVALENCE OF ONCOGENIC VIRUS INFECTION IN THE WORLD
HBV
HCV
HIV
PREVALENCE OF ONCOGENIC VIRUS INFECTION IN THE WORLD…..continue
HPV
HTLV-1
KSHV
INCIDENCE OF SOME VIRUS-CAUSED CANCERS IN THE WORLD
NASOPHARYNGEAL CARCINOMA
BURKITT LYMPHOMA
INCIDENCE OF SOME VIRUS-CAUSED CANCERS IN THE WORLD
HEPATOCELLULAR CARCINOMA
CERVICAL CANCER
KAPOSI’S SARCOMA
CONCLUSIONGlobally, viral infections contribute to about 15% to 20% of all human cancers (Zur, 2001). 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 host factors. The
tumor viruses with small genomes integrate into host cell chromosomal DNA and cause mutations
and chromosomal rearrangements that predispose to cancer (Murat, 2012). Viral infection is now
considered as the second major preventable cancer risk factor after tobacco use. The universal
immunization program against HBV in Taiwan and Gambia has successfully lowered the incidence
of Hepatocellular carcinoma (HCC) in the vaccinated population. The first HPV vaccine approved in
2006 are expected to reduce deaths from cervical cancer by 75%, a number that should be a great
inspiration for similar research on other human oncogenic viruses as well (Zheng and Ou, 2009).
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