Cancer pathology

Question 1

What is cancer?

Answer 1

a disease of aberrant cell proliferation & differentiation?

Question 2

How high is the risk of cancer arising from functional ?

Answer 2

Low

Question 3

What are 3 environmental influences must affect cancer?

Answer 3

• infection
• diet
• noxious agents

Question 4

What is the Peyton Roux experiment?

Answer 4

“a sarcoma is transferred to a chicken”

Question 5

What does cancer arise from?

Answer 5

Virus encodes a hyperactive form of a human tyrosine kinase gene

Question 6

What are the effects of a hyperactive form of a human tyrosine kinase gene?

Answer 6

increased cell adhesion, cell proliferation, cell mobility

Question 7

What is an example of a virus that causes cancer?

Answer 7

cervical carcinoma - caused by human papillomavirus

Question 8

What is an example of a bacteria that causes cancer?

Answer 8

Gastric carcinoma - caused by helicobacter pylorii

Question 9

What is an example of a cancer caused by diet?

Answer 9

Aspergillus oryzae - koji mold - rice, peanuts - can cause hepatocellular carcinoma

(caused by aflatoxin) - in order to get rid of this toxin, the liver causes a structural change, that modifies DNA bases, results in a mutation

Question 10

What is an example of a noxious substance that causes cancer?

Answer 10

asbestos - causes mesothelioma

Question 11

What other factor can cause cancer other than environmental factors?

Answer 11

Genetic predisposition

Question 12

What is an example of a cancer caused by a genetic pre-disposition?

Answer 12

Breast cancer syndrome

Question 13

What is an example of a cancer caused by genetic predisposition?

Answer 13

chronic myeloid leukemia

Question 14

What is the chromosomal error that causes chronic myeloid leukemia?

Answer 14

there is a chromosomal translocation between chromosome 9 & chromosome 2

Question 15

What technique is used to establish what chromosomal changes cause certain cancers?

Answer 15

FISH (fluorescent in situ hybridisation)

Question 16

Why does chromosomal translocation have such a devastating effect on the proliferation of white blood cells?

Answer 16

Causes the fusion of 2 genes, one which is a positive regulator of cell growth

Question 17

What is a kinase?

Answer 17

An enzyme that phosphorylates proteins. It changes the function of the protein. This can either turn a protein on or off.

Question 18

What are oncogenes?

Answer 18

A gene with the potential to cause cancer, by transforming cellular behaviour

Question 19

How do oncogenes come about?

Answer 19

Arises from genes involved in regulated proliferation - PROTO-oncogenes

Question 20

What are the 2 structural shapes that Ras exists in?

Answer 20

Ras + GTP
Ras + GDP

Question 21

When the ras is bound to GTP, is the protein switched on or off?

Answer 21

Switched on

Question 22

When the ras is bound to GDP, is the protein switched on or off?

Answer 22

Switched off

Question 23

How fast is the rate of conversion between ras + GTP/GDP without GTPase?

Answer 23

Rate of conversion is slow without GTPase.

Question 24

What is the conversion from Ras + GTP to Ras + GDP called?

Answer 24

exchange

Question 25

What do growth factors bind to, in order to start cells proliferate?

Answer 25

receptors - e.g. tyrosine kinase receptors

Question 26

What are the different pathways which encourage cell growth from ras?

Answer 26

- cell growth - gene expression - gene morphology & movement

Question 27

Describe the state of mutant ras in tumors?

Answer 27

In mutant ras, the off ras state doesn't exist. This is because ras loses its GDP.

Question 28

What is the argument for the existence of tumour suppressor genes?

Answer 28

loss of growth suppressor gene more likely than gain-of-function oncogenes mutations.

Question 29

What is the argument against the existence of tumour suppressor genes?

Answer 29

loss of both alleles of putative growth suppressor genes unlikely

Question 30

What theory did Knudsen propose?

Answer 30

one/two-hit hypothesis

Question 31

Why is Knudsen's one/two-hit hypothesis important?

Answer 31

provides evidence: - for tumour suppressor gene hypothesis - that cancer requires wild-type alleles - for the basis of inherited predisposition to cancer

Question 32

A Chromosome 13 deletion can create what cancer?

Answer 32

retinoblastoma

Question 33

Describe the properties of oncogenes

Answer 33

- activating - gain of function - dominant - one allele mutated required to exert effect - enhanced effect on the function of the protein product

Question 34

Describe the properties of tumour suppressor genes

Answer 34

- inactivating - loss of function - recessive - two allele mutated required to exert effect - reduced effect on the function of the protein product

Question 35

How genetically stable are cancer cells?

Answer 35

cancer cells are genetically unstable

Question 36

What are the 3 causes of genetic instability?

Answer 36

Defects in: - DNA repair pathways - Correction mechanisms for DNA replication errors - Correction mechanisms for DNA segregation errors

Question 37

What is an example of a cellular stress that can induce apoptosis in normal cells?

Answer 37

DNA damage