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Biology 465 > DNA Damage > Flashcards

DNA Damage Flashcards

1
Q

What are the two types of DNA damage?

A
  1. Spontaneous alterations and damage to DNA

2. Environmental damage to DNA

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2
Q

What is DNA damage most commonly caused by?

A

Chemicals or radiation

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3
Q

How are people exposed to chemical carcinogens?

A

It’s a result of being exposed due to occupation, pollution in the ambient environment, lifestyle choices or pharmaceutical use.

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4
Q

What do chemical carcinogens act through?

A

They act through “genotoxic” or DNA damaging mechanisms, which involve covalent binding of the chemical to DNA (DNA adduct formation)

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5
Q

What is a necessary requirement for tumor induction when exposed to cancer carcinogens?

A

They’re typically frequent and/or chronic over the years which results in the accumulation of DNA damage or DNA adduct formation

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6
Q

What have studies in animal models indicated about environmental DNA damage?

A

The ability to reduce DNA damage will also result in the reduction of tumour risk

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7
Q

What was the hypothesis determined by the animal model studies?

A

Individuals having the highest levels of DNA adducts may have an increased cancer risk, compared to individuals with the lowest levels of DNA adducts

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8
Q

What is a DNA adduct?

A

A segment DNA that is bound to a cancer causing agent

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9
Q

What did Poirier review in 2012?

A

He reviewed 12 investigations showing a 2- to 9-fold increased risks for cancer in individuals having the highest DNA adduct levels, compared matched individuals with the lowest DNA adducts

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10
Q

What other preliminary evidence did the studies reviewed by Poirier provide?

A

It provided preliminary evidence that multiple types of DNA adducts combind, or DNA adducts combined with other risk factors (eg., infection or inflammation), may be associated with more than 10-fold higher cancer risks, compared to those found with a single carcinogen

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11
Q

What did the data from the preliminary evidence reviewed by Poirier suggest?

A

It suggested that a reduction in human DNA adduct level is likely to produce a reduction in human cancer risk

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12
Q

What reactive oxygen species are produced by normal metabolism?

A

Superoxide and hydrogen peroxide

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13
Q

What is NOX?

A

NAD(P)H oxidase (NOX) is a membrane bound enzyme that macrophages use to produce O2- to kill bacteria

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14
Q

Is NOX upregulated or downregulated in TAMs?

A

Upregulated

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15
Q

How does the Fenton reaction lead to DNA damage?

A

Reduced transition metals react with hydrogen peroxide to produce hydroxyl radicals which have the capacity to damage macromolecules (eg., DNA)

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16
Q

What are the three ways radical oxides, from the Fenton reaction, damage biomolecules?

A
  1. Scission: DNA double-strand breaks
  2. Modification: 8-oxoguanine, HNE, etc.
  3. Cross-links: thymine-tyrosine cross-links, etc.
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17
Q

What cancer causing mutations of the genome are due to damage of biomolecules?

A
  • Amplification
  • Deletion
  • Point mutation
  • Translocation (fusion gene)
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18
Q

What does oxidation of DNA lead to?

A

DNA damage and mispairing

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19
Q

How can Chromosome Aberrations be detected?

A
  1. Microscopy detection

2. Importance of double strand breaks

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20
Q

How can micronuclei be detected?

A
  1. Microscopy detection

2. Flow cytometry detection

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21
Q

How can single strand breaks be detected?

A
  1. Comet assay (single cell gel electrophoresis)
  2. Alkaline elution
  3. Gel electrophoresis
  4. PCR assays
22
Q

What was the result of antioxidant supplementation (alpha-tocopherol, beta-carotene and vitamin C) in smokers and non-smokers?

A
  • There were decreases in oxidative DNA damage in human blood lymphocytes.
  • Sites sensitive to Endonuclease III, an enzyme that excises oxidized pyrimidine bases from DNA, decreased
23
Q

What is the result of gamma radiation?

A

DNA double strand breaks

24
Q

How was the DNA, in the experiment by Dr.Chantal Courtemanche, treated?

A
  • Fractions of DNA was actively release

- cells were irradiated either in agarose (no repair) or in culture (possible recombination repair)

25
Q

What is significant about hypoxia and its effect on DNA?

A
  • It’s an oxidant stressor
  • The microenvironment is supported by HIF1-alpha and angiogenesis
  • > induces DNA damage
26
Q

What does DMTU do?

A
  • An antioxidant

- Attenuates hypoxia-induced DNA damage

27
Q

What is an example of DNA base damage?

A

Modified guanines: oxo^8-dG

28
Q

What are the seven sources of oxidative DNA damage?

A
  • Endogenous metabolism
  • Inflammation
  • Smoking
  • Cancer
  • Ionizing radiation
  • Exercise
  • Xenobiotics
29
Q

How many oxidation products of DNA bases are possible?

A

18 adducts are possible

30
Q

What are the three types of oxidized guanines?

A
  1. 8-oxo-2’-deoxyguanosine (oxo^8dG)
  2. 8-oxoguanosine (oxo^8G)
  3. 8-oxoguanine (oxo^8Gua)
31
Q

Why is oxidized guanine a problem?

A

It is a modification to the DNA that could cause problems in DNA synthesis due to improper base pairing

32
Q

What is the advantage to Gas Chromotography Mass Spectrometry (GC-MS) detection of modified bases?

A

Can detect an array of base damage

33
Q

What is the disadvantage to Gas Chromotography Mass Spectrometry (GC-MS) detection of modified bases?

A

Must run at a high temperature

34
Q

What is the advantage of High Performance Liquid Chromatography - Electrochemical (HPLC-EC) detection of modified bases?

A

Can be done at room temperature minimizing artifactual damage

35
Q

What is the disadvantage of HPLC-EC detection of modified bases?

A

Can only detect modified bases that give a clear EC signal

36
Q

What does Epigallocatechin o-Gallae (EGCG) do?

A

Inhibits neutrophil infiltration and oxidative DNA damage in phorol ester-treated mouse skin

37
Q

What important discovery was determined from the EGCG experiments?

A

Tumour numbers and volume correlate with oxidative DNA damage but if you block the oxidative DNA damage, you can block the amount of tumour

38
Q

What is EGCG?

A

A gallate produced in plants

- The reason that eating more fruits and vegetables can be a cancer preventative (increases EGCG)

39
Q

What are the advantages of Antibody detection?

A

High throughput

40
Q

What are the disadvantages of Antibody detection?

A

Not analytical, mostly qualitative in nature up to this point

41
Q

What is Ferric nitrilotiracetate-induced oxidative DNA damage in renal proximal tubule cells associated with?

A

Necrotic cell death

42
Q

What is the advantage to Post labeling methods for detecting base damage?

A

It’s sensitive

43
Q

What is the disadvantage to Post labeling methods for detecting base damage?

A

Must use a radioactive nucleotide for detection

44
Q

What happens when Uracil is incorporated into DNA and not repaired?

A

It causes chromosome breaks

  • the same way as that of radiation induced chromosome breaks
  • lesions in opposing DNA strands are excised by base excision repair, which causes a chromosome break
45
Q

How can you detect uracil incorporation into DNA?

A

GC-MS with negative Cl for the detection of uracil in DNA

46
Q

What are AP sites?

A
  • Apurinic and apyrimidinic (AP or abasic) sites
  • lesions in DNA
  • formed either spontaneously or as intermediates during the course of base excision repair of oxidized, deaminated or alkalated bases
47
Q

Where are oxidative DNA lesions with mutagenic potential formed?

A

In inflammation-related cancer cells

48
Q

What was the mechanism proposed by Ohnishi et al?

A

The generation of cancer stem cells by inflammation:

  • Chronic inflammation results in the production of ROS and RNS
  • ROS and RNS cause both DNA damage and tissue injury in the stem cells
  • DNA damage results in genomic instability and mutation
  • The mutation and damaged stem cells result in cancer stem cells that lead to carcinogenesis
49
Q

What does chronic inflammation by infectious agents, inflammatory diseases, and other factors cause and how does it cause this damage?

A

ROS/RNS generation results in various types of damage to nucleic acids, proteins and tissues

50
Q

What can tissue injury during chronic inflammation activate?

A

Progenitor/stem cells for regeneration

51
Q

In the progenitor/stem cells made for regeneration, what can ROS/RNS generate?

A

Due to the ROS/RNS causing multiple mutations, they may generate mutant stem cells and cancer stem cells which leads to carcinogenesis.

52
Q

Where was 8-nitroguanine formed?

A

It was formed in stem cell marked positive cells in infection-associated cancer tissues

Biology 465 (15 decks)

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