Lecture 8 - viruses and cancer Flashcards
what are infectious agents and cancer?
In 2018: 2.2 million infection attributed cancers diagnosed
(~13-15% of cancers globally)
11 infectious pathogens classified as group 1 carcinogens
H. pylory is single biggest causer (810 000 cases)
Human papillomavirus (690 000), hepatitis B virus (360 000) and hepatitis C virus (160 000).
what are the characteristics of a tumour causing virus?
Persist in the host
Long interval before tumour development( months to years)
Mechanism:
Direct: Retrovirus, KSHV, HPV
Indirect: Retrovirus, HCV, HBV ,(HIV-1)
what are Human papillomavirus (HPV)?
HPV - extremely common worldwide
>100 types of HPV (~40 sexually transmitted)
14 cancer-causing (high risk types)
Two HPV types (16 and 18) cause 70% of cervical cancers and precancerous cervical lesions
Cervical cancer – globally, 530 000 new cases in 2012
84% in less developed regions
High risk HPV: anus, vulva, vagina and penis cancer
what is cervical screening in the UK?
Sample of cells from the surface of cervix
Molecular test for high risk HPVs
If HPV detected, checked under a microscope to look for abnormal cells (cytology)
If abnormal cells detected - refer to colposcopy
(HPV molecular testing as primary screen introduced in Scotland in 2020)
What is the HPV vaccination strategy?
HPV 16 and 18 responsible for
70% of cervical cancer
HPV 6 and 11 major causes of
genital warts
Gardasil 9 protects against HPV
types 6, 11, 16, 18, 31, 33, 45,
52, and 58
(~90% of HPV types causing
cervical, vulvar, vaginal, and
anal cancers)
it is very successful
what are the 3 mechanisms for retroviruses and cancer?
Transducing (animal only)
Cis-activating (animal only)
Trans-activating (human)
what is tax? a transcriptional activator
Viral protein (no equivalent in cellular genome)
Regulates transcription of specific cellular genes
what is HIV-1 (an oncogenic virus?)
Not cancer inducing
Suppresses the immune system
“Normal cancers” can not be eliminated
Immune escape of cancer causing viruses e.g. KSHV
what is cancer and hepatitis?
Hepatitis B virus (HBV)
DNA (double and single stranded)
Hepatitis C virus (HCV)
Cytoplasmic RNA virus
Chronic infection is leading causeof hepatocellular carcinoma (~70% of cases)
what is the Hepatitis B virus
Viral infection that attacks the liver
Can cause acute and chronic disease
Chronic infection in:
80–90% infected during the first year of life
30–50% of children infected before the age of 6 yrs
<5% of otherwise healthy persons who are infected as adults
20–30% of adults who are chronically infected will develop cirrhosis and/or liver cancer
what is the Hepatitis C virus (HCV)
Both acute and chronic hepatitis
~20-40% of people infected will clear the virus
Remainder develop chronic HCV infection
Risk of cirrhosis is between 20–30% within 20 years
what is HBV vaccine and treatment?
WHO call to increase vaccination globally
(HBsAg vaccine)
Now part of the UK childhood immunisation schedule
HBV antiviral drugs available
(long term therapy) – reduces but does
not eliminate risk of HCC
what us HCV treatment?
Cure chronic infection in >90% of cases (treatment 8-12 weeks)
Biggest impact on HCC risk predicted in patients treated before cirrhosis has developed
Expensive (e.g. Harvoni $94,500/ 12-week treatment)
how do you cure HCV?
Virus targeting drugs
Highly effective
WHO aim: 80% reductionin infection by 2030
