Carcinogenesis Flashcards Preview

Biology Of Cancer > Carcinogenesis > Flashcards

Flashcards in Carcinogenesis Deck (36)
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1
Q

Features of a benign tumour?

A

Slow growth
Non-invasive
No metastasis

2
Q

Features of a malignant tumour?

A

Rapid growth
Invasive
Potential for metastasis

3
Q

What are the stages of carcinogenesis?

A

Initiation
Promotion
Progression

4
Q

What happens in initiation?

A

Unrepaired DNA damage due to a carcinogenic initiator

5
Q

What happens in promotion?

A

Coronal expansion from rapid proliferation leading to benign tumour formation

6
Q

How long does promotion take?

A

10 to 30 years

7
Q

How do carcinogens cause mutations?

A

After being metabolised, it forms a DNA adduct (covalent bond) which causes a mutation

8
Q

What can be a mutagen and how do they cause the damage?

A

A virus causing insertional mutagenesis
Chemicals causing DNA adducts
UV and ionising radiation causing single and double strand breaks

9
Q

Function of a proto-oncogene?

A

Cause cell growth and gene transcription

10
Q

Normal function of a tumour suppressor gene?

A

Cell repair
Cell cycle control
Cell death

11
Q

Difference between a tumour initiator and promoter?

A

Initiators are mutagens
Promoter causes multiplication of the damaged cells
If exposed to a promoter first and then the initiator, nothing will happen

12
Q

Example of a promoter?

A

Oestrogen for breast cancer

Androgens for prostate cancer

13
Q

What can be an intracellular cause of a gene mutating?

A

Misinterpretation of code
Polymerase slippage
Base malalignment
Ineffective repair with age

14
Q

What can be environmental causes of mutations and how?

A

Carcinogens which bind to DNA and alter the sequence, affecting replication
Ionising radiation/UV can cause strand breaks or cross-links
DNA can be translocated to transcriptionally active regions

15
Q

Give examples of initiators

A
Chemical carcinogens
Oncogenic viruses
Radiation
UV light 
Oxygen free radicals
16
Q

Give examples that can cause mutations in genes

A
Alteration of bases
Strand breaks 
Base oxidation
Deletion of bases
Deletion of chromosome fragments
Adducts of carcinogen and base
Chromosome translocation/rearrangement
Gene amplification
17
Q

Examples of some chemical promoters?

A

Phorbol esters
Phenols in tobacco tar
Xenoestrogens found in insecticides
Saccharin

18
Q

Give inflammatory examples of promoters

A

Chronic irritation from eg pipe smoking
Endoparasites eg schistosoma haematobium causing bladder cancer
Bacterial infection eg H pylori

19
Q

Which drug can be given to block oestrogen receptors?

A

Tamoxifen

20
Q

What is cancer?

A

A group of diseases sharing similar characteristics, all of which show inappropriate proliferation, invasion and metastasis

21
Q

What is cell signalling required for?

A
Cell cycle progression
Proliferation
Inflammation
Pro/anti-apoptosis
Metastasis
Invasion
22
Q

What is cell signalling controlled by?

A
Cell surface receptors 
Ligands
Cascade of intracellular signal transduction 
Proteins
Transcription factors 
Inhibitors
Mitogens
Cytokines
23
Q

What can be changed about cell signalling pathways so that they promote cancer?

A

Increase in receptor expression
Mutant receptor expression (self-activating)
Down-regulation of inhibitory proteins/mechanisms
Increased ligand expression
Increased expression of transcription factors

24
Q

What are the six hallmarks of cancer and how does it do it?

A

Induce angiogenesis - active VEGF signalling

Evade growth suppressors - inactivate cell cycle checkpoint

Sustain proliferative signalling - constitutively activate growth factor signalling

Activate invasion and metastasis - loss of cell-to-cell interactions

Replicative immortality - inactivated cell death pathway

Resistance to cell death - activated anti-cell death signalling

25
Q

Other than the six hallmarks of cancer, what are 4 more important features recently discovered?

A

Tumour-promoting inflammation
Avoid immune destruction
Genome instability and mutation
Deregulating cellular energetics

26
Q

General risk factors for cancer?

A
Genes
Carcinogens
Radiation
Chemicals eg abestos
Viruses eg HPV 
Diet
Alcohol
Smoking
27
Q

What are some carcinogens in different foods?

A
Heterocyclic amines (meat)
Toxins 
Inflammation/oxidative stress inducers
Hot drinks/food
Alcohol
28
Q

Which foods specifically are carcinogens?

A
Red meat
Animal fat
Salted fish
BBQ/chargrilled foods
Salt-preserved foods
Contaminated foods (fungus)
29
Q

What evidence is there that foods affect cancer risk?

A

Migration studies

Intervention trials

30
Q

What increases heterocyclic amine concentration?

A

Cooking meat and increasing the cooking time

Metabolised to the liver to genetoxic metabolites

31
Q

How does barbecuing meat increase cancer risk?

A

Burns fat to produce polyaromatic hydrocarbons which require metabolic activation
Adducts to DNA bases - p53

32
Q

How do high carb foods increase cancer risk?

A

If they are roasted or baked eg cereal, coffee, bread, crisps
Contain acrylamide which is a genotoxic metabolite which adducts to DNA

33
Q

What is chemoprevention?

A

Inhibition, retardation or reversal of the carcinogenic process

34
Q

Examples of drugs in chemoprevention?

A

Tamoxifen
Celecoxib (COX-2)
Aspirin (COX)
Herceptin (EGFR Ab)

35
Q

What is a direct acting carcinogen?

A

One that binds directly to DNA

36
Q

What are procarcinogens?

A

Require metabolic activation