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Cancer Flashcards

(89 cards)

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1
Q

What is the definition of cancer?

A

A group of diseases that includes solid tumours at almost any site of the body and leukaemias

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2
Q

What differentiates cancer from most other diseases?

A

It is a disease of the body’s own cells

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3
Q

What is cancer caused by?

A

Uncontrollable division of abnormal cells

The cells behave abnormally as they have lost the ability to regulate when they need to grow and divide

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4
Q

Why are the most common cancers lung and skin cancer?

A

These occur in tissues where cell death and replacement is the most frequent

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5
Q

What are the 4 features of cancer cells?

A
  1. uncontrolled cell division
  2. change in morphology (shape) of the cells
  3. Dedifferentiation of cells
  4. Cell migration into adjacent as well as distant tissues
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6
Q

What is meant by dedifferentiation of cells?

A

This involves cells regressing from a specialised form to a similar state resembling that of stem cells

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7
Q

What are the 3 characteristics of cancer cells grown in the lab?

A
  1. uncontrolled growth
  2. loss of contact inhibition
  3. cells are immortal
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8
Q

What would happen to normal cells once they had filled the surface of a petri dish?

A

They stop growing due to sending each other signals when they are touching each other and have formed a layer

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9
Q

What would happen if normal cells that had filled the petri dish were diluted and placed in a larger dish?

A

The cells would continue dividing

They would eventually stop dividing altogether as they have a finite lifespan

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10
Q

What is meant by ‘loss of contact inhibition’ in cancer cells?

A

Cancer cells do not stop growing once they have filled the petri dish

They begin to pile on top of each other

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11
Q

What is meant by cancer cells being ‘immortal’?

A

They continue to grow without dying off

They do NOT have a finite lifespan

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12
Q

What is a metastatic cancer?

A

A cancer that has spread from the primary site of origin into different areas of the body

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13
Q

What is metastasis?

A

The spread of cancer cells to new areas of the body

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14
Q

What are the 4 stages in cancer development?

A
  1. single hyperproliferative cell
  2. early adenoma
  3. late adenoma
  4. carcinoma
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15
Q

When does hyperproliferation occur in the 1st stage of cancer development?

A

It occurs when there is an abnormally high rate of cell proliferation by rapid division

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16
Q

What are the characteristics of an early adenoma?

A

It is a small clump of cells

It is a non-cancerous tumour that does not have the ability to spread to other parts of the body

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17
Q

How is the late adenoma formed?

A

The cells continue to divide uncontrollably and pile on top of each other

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18
Q

What are the characteristics of a carcinoma?

A

The cancer cells have begun to invade the local tissue

They can now enter blood vessels and be transported around the body

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19
Q

What are the series of mutations which lead to tumour formation?

A

Mutations may encourage the growth of cells to form a malignant tumour

Further mutations may cause the tumour to become metastatic

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20
Q

How many mutations must occur in order for cancer to develop?

A

There must be multiple mutations in several key genes

Cancer does not occur from a single gene mutation

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21
Q

Cancer only occurs when mutations occur in which 3 types of genes?

A
  1. proto-oncogenes and oncogenes
  2. tumour suppressor genes
  3. DNA repair genes
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22
Q

What is the role of proto-oncogenes?

A

They are growth promoting genes that tell cells when to grow and divide

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23
Q

What is the difference between a proto-oncogene and an oncogene?

A

A proto-oncogene is a normal gene, that when mutated becomes an oncogene, which contributes to cancer

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24
Q

What do mutations in proto-oncogenes lead to?

A

It increases activity of the oncogenes and leads to inappropriate switching on of cell division

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25
What is the role of tumour suppressor genes?
They are growth-inhibiting genes that maintain a cell in a non-dividing state
26
What happens when there is a mutation in a tumour suppressor gene?
It leads to uncontrolled cell division
27
What is the role of DNA repair genes?
They repair any damage to DNA
28
Why is cancer more frequently seen in older people?
The process of accumulating mutations in several genes takes many years
29
What is a malignant cancer?
Malignant cancer cells form a cancer at the original organ
30
How does a malignant cancer spread around the body?
The malignant cancer cells will develop more mutations and form a metastatic tumour This can then spread to other organs through the bloodstream
31
What are the 2 types of point mutations? How many nucleotides do they tend to affect?
Missense and nonsense mutations They affect only one or very few nucleotides in a gene sequence
32
What is a missense mutation?
When a single nucleotide is changed and the codon now codes for a different amino acid
33
What is a nonsense mutation?
When a single nucleotide is changed and the codon becomes a stop codon This results in a truncated protein product
34
What is an insertion/deletion mutation?
The addition or loss of nucleotides, from a single base pair to huge swathes of chromosome
35
What happens if a multiple of 3 is inserted/deleted? What if it is not a multiple of 3?
If a multiple of 3 bases is added or deleted, it causes an amino acid to be inserted or deleted If it is not a multiple of 3, it causes a frameshift mutation
36
What is gene amplification?
An increase in the number of copies of a gene without a proportional increase in other genes
37
What does gene amplification result from?
The duplication of a region of DNA that contains a gene This occurs through errors in DNA replication and repair machinery
38
What are the most common genetic changes found in human cancer cells?
Translocations
39
What is a translocation?
A chromosome abnormality caused by a rearrangement of parts between non-homologous chromosomes
40
In which ways can translocations cause cancer?
1. a gene may be moved to a more transcriptionally active region of the new chromosome 2. two genes may be recombined into a new gene through fusion
41
What is aneuploidy?
Any departure from the normal structure or number of chromosomes e.g. trisomy
42
What are the two different things that a mutation can do to a gene?
1. disrupt the coding sequence sufficiently to stop the protein from functioning normally, if at all 2. make the protein more active
43
In cancer cells, how does the number of mutations affect how the cancer progresses?
1. initial mutation occurs in a single cell 2. as the cell expands, other mutations will be picked up 3. some mutations incur a growth advantage 4. more mutations continue to develop as the cell grows
44
What is the genetic instability in cancer cells caused by?
Exposure to carcinogens or mutations in DNA repair genes
45
What are the 3 things that mutation induction requires?
1. chemical modification of DNA and/or 2. replication of DNA 3. resulting in misincorporation by DNA polymerase
46
How may DNA polymerase usually make mistakes and what do they result in?
DNA polymerase naturally makes mistakes which result in the accumulation of genetic variation or polymorphisms in coding and non-coding sequences of the genome Some of these changes are deleterious mutations
47
What increases the tendency of polymerases to make mistakes?
The presence of chemical modifications in DNA
48
How may chemical modifications of nucleotides arise?
1. through environmental influence | 2. through endogenous reactive molecules, such as free radicals
49
How are normal cells induced to divide?
By positive growth factors binding to receptors on the cell surface
50
What happens when a positive growth factor binds to a receptor on the cell surface?
The internal portion of the growth factor receptor is activated This activates a cascade of intracellular signalling proteins The signal reaches the nucleus and initiates transcription of genes involved in regulating the cell cycle
51
How are normal cells prevented from dividing?
Through negative growth factors These are produced by growing tissues when sufficient cell division has taken place
52
How do negative growth factors affect the cell after binding to receptor proteins on the cell surface?
They initiate a signalling cascade that shuts down the cell cycle This results in the cell entering a quiescent/dormant state
53
What are the other key properties of normal cells?
1. they have a finite lifespan 2. they have a self-destruct mechanism called apoptosis 3. they have no influence on blood vessel formation 4. they are tightly joined together and are immobile 5. they are genetically stable
54
What are the 5 key properties of cancer cells?
1. independent of positive growth factors 2. resistant to negative growth factors 3. resistant to apoptosis 4. angiogenic 5. invasive and metastatic
55
What is meant by cancer cells being angiogenic?
They have the ability to cause blood vessels to form nearby As the tumour grows, the increasing number of cells requires more blood vessels to supply O2 and nutrients
56
What is the difference between a cancer cell being invasive and it being metastatic?
They are invasive when they begin to invade surrounding tissues They are metastatic when they exist in other tissues other than the ones in which they first developed
57
What is a cancer syndrome?
When cancer develops from mutated genes that have been genetically inherited
58
What types of cancer tend to be common in certain families? Inherited predispositions account for what % of all cancers?
Colon and breast cancers Inherited predispositions account for 5% of all cancers
59
What are examples of biological agents and the cancers which they cause?
Hepatits B and C - liver cancer Human papilloma virus - cervical cancer H.pylori - stomach cancer
60
What are examples of chemical agents and the cancers they cause?
1. cigarette smoke - lung, bladder and others | 2. Heterocyclic amines in cooked meat - colon cancer
61
What are examples of physical agents and the cancers they cause?
UV in sunlight - skin cancer X-rays and gamma-rays - radiotherapy related leukaemia
62
What is a carcinogen?
Any agent that significantly increases the risk of developing cancer
63
Why are most carcinogens described as 'genotoxic'?
Genotoxicity describes the property of chemical agents that damage the genetic information within a cell, causing mutations
64
How do non-genotoxic carcinogens cause cancer?
They induce cell division and DNA replication without being mutagenic
65
What other word can be used to describe genotoxic carcinogens?
Mutagens All mutagens are genotoxic, but not all genotoxic substances are mutagens
66
How do carcinogens increase the chance of cancer occurring?
They increase cell proliferation, so increase the chances of mutations occurring
67
What type of study must be carried out to show that a chemical is carcinogenic in humans?
Epidemiology studies This involves looking for an association between the exposure to the chemical and the incidence of cancer
68
What are the 2 types of epidemiology studies?
1. case-control studies | 2. prospective (cohort) studies
69
What is involved in a case-control study?
Comparing diseased groups with matched control groups Looking for factors that are more common in people with the disease
70
What is important to consider when preparing a case-control study?
Variation should try to be reduced between the disease and control group e.g. same gender, same age, come from the same city
71
How can the results of a case-control study show strong evidence?
If the study is repeated many times in different places and the results are repeated
72
What is involved in a prospective (cohort) study?
A population is followed over time to confirm that a disease is linked to a suspected cause
73
What types of people are involved in a cohort study and what type of data is collected?
Healthy people are followed and split into an exposed and unexposed group and exposure data is collected This establishes whether there is an association between exposure and disease
74
What are the pros and cons of a cohort study?
It is less susceptible to bias and more effective but... It takes longer
75
How many carcinogens are in cigarette smoke and how do they cause cancer?
It contains over 50 chemical carcinogens These react with DNA to cause DNA damage
76
What is benzopyrene? How does it affect DNA?
It is a polycyclic aromatic hydrocarbon found in tobacco smoke It binds to deoxyguanosine to form a DNA adduct
77
What does the presence of a DNA adduct lead to?
Increased chance of mutation
78
What is significant about benzopyrene containing aromatic rings?
It is not soluble in water so it is difficult for the body to excrete
79
What happens once benzopyrene has bound to guanine?
DNA polymerase is unable to recognise guanine This means the wrong base is inserted opposite guanine
80
What does a non-melanoma skin cancer develop from?
They develop in the epidermis (outermost layer of skin)
81
What is the difference between a squamous cell carcinoma and a basal cell carcinoma?
SC - starts in the cells lining the upper epidermis BC - starts in the cells lining the bottom of the epidermis They are both non-melanoma
82
How common and curable are non-melanoma skin cancers?
Quite common and often curable There is a much lower risk that the cancer will spread to other parts of the body
83
Where does melanoma skin cancer develop from?
Skin cells called melanocytes
84
Why is melanoma skin cancer more dangerous than non-melanoma?
It is more fatal and can spread to other organs easily There is a chance of melanoma returning once it has been treated
85
How does UV-B damage DNA and cause potentially mutagenic damage?
It puts energy into the DNA molecule to break the sugar-phosphate backbone It may change some of the bases
86
What is the thymine dimer?
Energy from UV-B radiation causes covalent bonds to form between adjacent thymine molecules DNA polymerase cannot recognise the thymine in this state
87
How do different genotoxic agents (mutagens) affect DNA?
They can modify DNA in different ways This leads to lots of different mutational outcomes which vary in severity
88
What are DNA lesions?
Sites of damage in the base-pairing or structure of the DNA molecule
89
What are the 5 tips to avoid getting cancer?
1. don't smoke 2. drink in moderation 3. avoid too much time in the sun 4. eat a balanced diet with lots of fruit and vegetables and not too much sugar or red meat 5. maintain a healthy weight

Nucleic Acids (4 decks)

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