Oral Cancer Aetiology Viruses Flashcards
What does oral cancer exclude?
posterior 1/3 of the tongue and soft palate because by definition they are a part of the oropharyngeal system
what are the infectious agents-viruses?
- Human papilloma virus (HPV)
- Epstein-barr virus (EBV) (HHV 4)
- Human immunodeficiency virus (HIV)
What are 5 types of HPV?
- Alpha
- Beta
- Gamma
- Mu
- Nu
Describe Epidermodysplasia verruciformis or tree man illness
- A rare autosomal recessive genetic
- Affects your skin and increases the risk of carcinoma of the skin
Describe Human papillomaviruses (HPVs)
high-risk types of HPV cause the following cancers
- cervical
- anal
- oropharyngeal
- vaginal
- vuvlar
- penile
- spread through direct sexual contact
- white, non-smoking males aged 35 to 55 are most at risk, 4 to 1 over females
Describe HPV
- ds DNA circular virus
- epitheliotrophic - targets mucosa
- only 1% progress to malignant disease
- widespread in humans and other animals
What does human papillomaviruses (HPVs) consist of?
- belong to the papvavirus group
- are small, non-enveloped DNA viruses of a symmetrical icosahedral shape
- Papillomavirus particles consist of a single molecule of double-stranded, circular DNA with approximately 8000 bp, contained in a capsid (spherical protein coat) composed of 72 capsomeres
- 200 types have already have identified
- HPV viruses can be grouped into high-risk (HR) and low-risk (LR) HPV types
- HR-HPVs are associated with carcinogenesis, 16,18, 31, 33, 35, 39, 45, and 52
- say high risk HPV 16 and 18 in exam
why is HPV 16 is of interest?
- due to oncogenic properties
- 6 early genes (E1, E2, E4, E5, E6 AND E7)
- 2 Late genes
(L1 and L2) - E6 and E7 have oncogenic properties they target tumour suppressor genes
What does HPV do?
- HPV infects undifferentiated proliferative basal cells, which are capable of dividing
- viral DNA localizes into the nucleus and establishes itself as an episome
- the viral proteins E1, E2, E6, and E7 are transcribed from the early promoter are expressed at a low level
- E6 and E7 may disturb the normal terminal differentiation by stimulating cellular proliferation and DNA synthesis
- the capsid proteins L1 and L2 accumulate in the mature epithelial cells
- the assembly of infectious virions takes place in terminally differentiated cells of the upper epithelial layers, and the virions are shed to the environment
What does HPV result in?
- Latency and malignant transformation through interactions of viral E6 and E7 a proteins with p53 and pRB
- E7 protein binds and inactivates a human tumour suppressor gene product, the retinoblastoma protein (pRB)
- viral E6 protein binds p53 and earmarks it for destruction by the ubiquitin pathway
- During the normal HPV life cycle, viral DNA is maintained episomally in the nucleus of the affected cell, a state predominately associated with “low-risk” HPV types such as HPV-6 and -11
describe oral HPV lesions
Benign
- Papilloma
- Condylomata
Malignant
- Cancer - SCC
List risk factors
- Number of sexual partners
- Weakened immune systems
HPV detection
- P16 staining
- In-situ hybridisation (ISH)
List the vaccinations
- quadrivalent Gardasil (HVP 6, 11, 16, 18)
- bivalent Cervarix (16, 18)
- nonvalent Gardasil 9 (16, 18, 31, 33, 45, 52 and 58)
Significance of HPV on cancer treatment outcome
In retrospective studies, HR-HPV - and/or p16INK4a positive tumours have been found to respond better to multimodal therapies as compared to HPV negative tumours, thereby favouring patient survival