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aPATH P COPY (SC) > Neoplasia 3 > Flashcards

Neoplasia 3 Flashcards

1
Q

Carcinogenesis=

A

causes of cancer

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2
Q

name some intrinsic factors of neplasia

A

Hereditary

  • Autosomal dominant genes most likely to cause tumour in the young
    • Will develop neoplasia
    • E.g. breast cancer
  • Less frequent genes- neoplastic phenotype
    • Multiple abnormalities which lead to an increased risk

Age

  • The older you are the longer you’ve had to develop

Sex (particularly hormone)

  • E.g. breast cancer predominately a female cancer due to oestrogen exposure
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3
Q

Extrinsic factors

A

Environment

  • Chemical
  • Radiation
  • X-ray

Infection

  • HPV

Behaviour (30%)

  • Tobacco smoke
  • Obesity
  • Sun exposure (UV damage)
  • Alcohol
  • Lack of exercise (independent to BMI)
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4
Q

Being overweight and obese is the 2nd biggest cause of cancer

A

Keeping a healthy weight reduces the risk of 13 different types of cancer

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5
Q

smoking is the biggest

A

preventable cause of cancer (25%)

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6
Q

which cancers is smoking a risk factor for?

A
  • Lung cancer 7/10- most common cause of cancer death
  • Mouth
  • Pharynx
  • Nose
  • And sinuses
  • Larynx
  • Oesophagus
  • Liver
  • Pancreas
  • Stomach
  • Kidney
  • Bowel
  • Ovary
  • Bladder
  • Cervix
  • Some type of leukaemia
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7
Q

if you drink and smoke it increases your risk of which cancers

A

upper airwars and digestive tract cancer

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8
Q

evidence of cancer

A
  • Animal studies
  • Epidemiological studies
  • Studies of migrating population
    • Look at baseline risk in original country
    • Then look at the rate of cancer once they have migrated
    • E,g, Japanese migrants to USA
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9
Q

approx how much of cancer risk is due to environment/ extrinsic factors

A

85%

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10
Q

example of a chemical that is a carcinogen

A

2-napthylamine (also present in smoke) is an industrial carcinogen used in the dye manufacturing industry

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11
Q

2-napthylamine

A

This dye causes cancer

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12
Q

Malignant neoplasms caused by 2-napthylamine showed that:

A
  • There is a long delay between carcinogen exposure and malignant neoplasm onset
  • The risk of cancer depends on total carcinogen dosage
  • There is sometimes organ specificity for particular carcinogens e.g. bladder cancer
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13
Q
A
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14
Q

chemical carcinogenesis involves

A

initiation and promotion

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15
Q

initiation and promotion

A
  • Sequence in which carcinogens are administered is critical
  • Initiators must be given first
  • Followed by a second class carcinogen called promoters
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16
Q

Test used to tell if chemical is a carcinogen

A

AIMS test

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17
Q

AIMs test

A

positive result- carcinogen capable of causing mutation

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18
Q

why is rat liver used in AIMs test?

A

most chemicals are pro-carcinogens until they are been activated in the liver (by cytochrome P450)

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19
Q

people with germline mutations get

A

cancer earlier

  • neoplastic cells get a head start
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20
Q

an initiator=

A

anything that causes mutation e.g. radiation

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21
Q

promoters

A

anything that causes expansion of that population

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22
Q

examples of chemicals

A
  • polycyclic aromatic hydrocarbons
  • aromatic amines
  • N-nitroso compounds
  • alkylating agents
  • natural products
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23
Q

example of aklylating agent

A

Vinyl chloride

  • mainly found in factories
24
Q

natural products

A

aflatoxin B1

  • found in virus- liver cancer
25
Q

asbestos

A

natural products

  • okay if left as it is
  • as soon as disrupted will be inhalte and irritate alveoli
  • both initiator and promotor
26
Q

type of radiation that are mutagenic

A

Alpha

Beta

Gamma

X ray

Uv ray

27
Q

how can radiation cause cancer

A
  • damage DNA directly
  • or indirectly generating free radicals
28
Q

how does radiation create free radicals

A

by crashing into water

29
Q

25% of all malignant neoplasms are

A

skin neoplasms- UV

30
Q

sources of ionising radiation

A
  • radon gas
  • medical tests
31
Q

infections and cancer

A
  • Some infections directly affect genes that control cell growth
  • Others do so indirectly by causing chronic tissue injury and the resulting regeneration acts either as a promoter for pre-existing mutations or causes new mutations from DNA replication errors
32
Q

example of infection with direct effect

A

HPV

33
Q

Indirect effect

A

HEP B virus

  • chronic inflammation= promotor
34
Q

Human papilloma virus (HPV)

A
  • Makes 2 proteins E6 and E7
    • Virus infects cell
    • ensures it doesn’t die and then hijacks its DNA replication machinery to make more virus particles
    • E6 inhibits P53 which prevents cells from undergoing apoptosis
    • Hijacks cell cycle by interfering with Rb protein which is an important cell cycle checkpoint
35
Q

example of an inherited cancer

A

retinoblastoma - rare tumour of the eye

36
Q

how many Rb cases are familial or sporadic

A

40% familial

60% sporadically

37
Q

familial Rb

A
  • Autosomal dominant means more likely to get it young
  • Occurs early
  • Can affect both eyes
38
Q

Sporadic Rb

A
  • In one eye
  • Generally, aren’t at increased risk of other cancer
  • Need 2 sporadic hits (mutations)
  • Occurs later
39
Q

Tumour suppressors

A
  • Normal function to stop proliferation
  • Loss of function
  • Most instances both alleles must be damaged for transformation to occur
  • Abnormalities in these genes leads to failure of growth inhibition
40
Q

example of tumour suppressor gene

A

Retinoblastoma gene

  • Key gene regulation of G1/s cell cycle checkpoint
  • Also controls cellular differentiation
41
Q

Proto-oncogenes

A
  • Drive proliferation
  • Gain of function mutation
42
Q

example of protooncogene

A
  • Most common type of abnormalities involving proto-oncogenes in human tumours
  • They are mutated in approx. 15-20% of all malignant neoplasm
  • Some types of cancers the frequency of RAS mutation is much higher e.g. 90% of pancreatic adenocarcinomas
  • They were discovered initially in transforming retroviruses (HIV)
43
Q

protoncogenes and tumour suppressor genes

A

play opposing roles in the cell signalling pathways

44
Q

accumulation of mutations leads to

A

malignant cancers

45
Q

proto-oncogenes can encode

A
  • growth factors (e.g. PGDF),
  • growth factor receptors ( e.g. HER2),
  • plasma membrane signal transducers (e.g. RAS),
  • intracellular kinases (e.g. BRAF),
  • transcription factors (e.g. MYC),
  • cell cycle regulators (e.g. Cyclin D1) apoptosis regulators (e.g. BCL2)
46
Q

DNA repair genes

A
  • caretakers genes prevent accumulation of DNA damage
  • familial cancer syndromes help our understaning
  • some inherited cancer syndromes have germline mutations that indirectly affect DNA repair
47
Q

familial breast cancer

A
  • BRAC1/ BRAC2 genes
  • Involved in repairing double strand DNA breaks
  • Can also be found in sporadic malignant neoplasms
48
Q

Chromosome aggregation during mitosis can also be abnormal in malignant cells

A
  • Alterations account for accelerated mutations found in malignant neoplasms known as genetic instability
  • Genes that maintain stability belong to a class of tumour suppressor genes called caretaker genes
49
Q

malignant neoplasm = ………………. mutations

A

10 or less

50
Q

hallmarks of cancer (6)

A
  1. Self sufficiency in growth signals
  2. Resistance to growth stop signals – TSG’s (tumour suppressor genes)
  3. Cell immortalisation (no limitation on the number of times a cell can divide)
  4. Sustained ability to induce new blood vessels (angiogenesis)
  5. Resistance to apoptosis
  6. Ability to invade and produce metastases
51
Q

example of self0sufficient growth signal

A

HER2 gene amplification (breast cancer)

52
Q

example of resistance to anti-growth signals

A

CDKN2A gene deltion

(CDK inhibitor)

Melanoma

53
Q

example of grow indefinitley

A

telomorase gene activation

  • most cancers
54
Q

example of induce new blood vessels

A

activation of VEGF expression

  • many cancers
55
Q

example of resistance to apoptosis

A

BCL2 gene translocation (lymphoma)

56
Q

example of inavade and produce metastases

A

E-cadherin mutation

  • gastric cancer

aPATH P COPY (SC) (19 decks)

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