Lecture 10 - 12

Question 1

What are the two kinds of inflammation?

Answer 1

Acute or chronic

Question 2

What occurs during the resolution of an inflammation?

Answer 2

The levels of proinflammatory mediators and infiltrated immune cells decline

Question 3

What is chronic inflammation?

Answer 3

It is caused by infectious or autoimmune diseases. It is a prolonged abnormal immune response that is not resolved by the normal feedback mechanisms
- associated with the development of 30% of malignancies worldwide

Question 4

What is chronic inflammation thought to promote in tumours?

Answer 4

• tumour initiation, progression and metastasis by providing a tumour-supporting microenvironment

Question 5

What is an important concept about metastatic spread?

Answer 5

Metastatic spread is responsible for ~90% of cancer-related mortality

Question 6

What is responsible for metastatic spread?

Answer 6

Changes in genes controlling cell-cell and cell matrix interactions (eg., E-cadherin, integrins)

Question 7

What is E-cadherin?

Answer 7

A transmembrane protein that mediates cell-cell interactions

Question 8

What is tumour progression associated with?

Answer 8

• the loss of E-cadherin function and the transition to a more motile and invasive phenotype
• cell pseudopod movement
• requires the coordinated regulation of both E-cadherin-mediated cell-cell adhesions and integrin-mediated adhesions that contact the surrounding ECM

Question 9

How is the regulation of E-cadherin and integrin dynamic?

Answer 9

Cells respond to external cues from the tumour microenvironment that regulate polarity, directional migration and invasion

Question 10

How would a loss of cadherin junction occur?

Answer 10

E-cadherins are supported by p120, alpha and beta catenin. If any of the catenins lose their function, then there is a loss of cadherin junction

Question 11

How does cadherin junctions protect the cell from cancer?

Answer 11

• protects from growth factors effecting the cell due to contact inhibition
• stays differentiated

Question 12

What are integrins?

Answer 12

Heterodimeric cell-surface glycoproteins that serve to mediate cell-ECM interactions
- like cues from the extracellular environment to the actin cytoskeleton

Question 13

What is EMT?

Answer 13

• epithelial to mesenchymal transition (EMT)
• a process normally involved in embryonic morphogenesis and wound healing/repair
• cells acquire ability to invade, resist apoptosis and to disseminate
• controlled by several TF (eg., Slug)

Question 14

What is Slug?

Answer 14

• a zinc finger transcriptional repressor which down-regulates expression of E-cadherin

Question 15

What does Slug do the cell?

Answer 15

• Causes a loss of adheren junctions and expression of matrix degrading enzymes, increased motility and resistance to apoptosis

Question 16

What occurs if Slug expression was increased?

Answer 16

It induces tightly bound epithelial cells to break into a loose mesenchymal phenotype and maintenance of this phenotype enables metastasis of tumour cells

Question 17

How was it determined that Slug suppresses E-cadherin transcription?

Answer 17

On a western blot:

• cells that had been less invasive in nature had large amounts of E-cadherin and little to no expression of Slug
• in more invasive cells, there was no E-cadherin and large amounts of Slug expressed

Question 18

What three changes occur during tissue invasion and metastasis?

Answer 18

1. Changes in genes controlling cell-cell and cell matrix interactions
2. Upregulation of protease genes (eg. matrix metalloproteases)
3. Down-regulation of protease inhibitors

Question 19

Is genomic instability a product of being cancerous or a cause?

Answer 19

• cancer arises from the accumulation of multiple mutations in the same cell
• tumour cells must acquire an increased mutability
• results in the loss of p53 and DNA repair genes

Question 20

What is the role of MSH2 and MSH6?

Answer 20

• MSH2: the protein that recognizes the mismatch

- MSH6: the protein that performs the repairs

Question 21

What occurs if there are mutations in MSH2 and 6 that results in down regulation?

Answer 21

It will result in the loss of fidelity that is identified in cancer

Question 22

What occurs if there is a double stranded DNA break repair?

Answer 22

• the loss is lethal to a cell
• apoptosis or necrosis
• chromosomal abnormalities

Question 23

What are important proteins that if mutated can contribute to cancer?

Answer 23

Rad 51 (& 50), ATM, BRCA1 and BRCA2

Question 24

How would a mutated ATM (eg. down-regulated)cause cancer?

Answer 24

• lack of ATM would decrease the phosphorylation of p53

- p53 would be unable to act on p21, Gadd45 and 14-3-3 which would result in S phase and M phase occurring.

Question 25

What are the roles of BRCA1 and 2?

Answer 25

They act as scaffolds in assembling repair machinery

Question 26

What are the differences between BRCA1 &2?

Answer 26

- BRCA1 is a large protein that allows other proteins to attach (including BRCA2). If knocked out, it is lethal as it is needed for DNA repair - Rad50 is bound to BRCA1 and Rad51 is bound to BRCA2

Question 27

What are the roles of Rad 50 & 51?

Answer 27

- both involved in double stranded DNA repair - both allow other proteins to bind to it - Rad50 binds to BRCA1 - Rad51 binds to BRCA2

Question 28

Do normal cells prefer glycolysis or the citric acid cycle? What about cancer cells?

Answer 28

- normal tissues tend to use the citric acid cycle in aerobic conditions (90%), if undergoing hypoxia in anaerobic conditions then they use glycolysis (10%) - cancer cells are more prone to using glycolysis despite high oxygen levels

Question 29

What is the Warburg Effect?

Answer 29

Even in the presence of oxygen, cancer cells reprogram their energy metabolism to preferentially use glycolysis

Question 30

What is the mechanism of the Warburg Effect?

Answer 30

- Ras is activated oncogenically - With PTEN, Ras activates HIF1-alpha - HIF1-beta binds to HIF1-alpha which allows them to enter the nucleus as a TF - Glut1 is expressed

Question 31

How do HIF1-alpha levels decrease?

Answer 31

- HIF1-alpha can be hydroxylated - once hydroxylated, VHL (Von Hippel-Lindau factor (E3)) can bind HIF1-alpha - results in the ubiquination of the complex - negative regulation

Question 32

If mitochondrial activity was decreased, how would this help a tumour?

Answer 32

- less HIF1-alpha available | - can not induce apoptosis

Question 33

What is PET Scanning?

Answer 33

- Positron Emission Tomography (18 Fluorodeoxyglucose tracer) - utilizes the reliance of cancer cells on glycolysis (glucose uptake) to generate images of the cancer

Question 34

Why do cancers make the switch to glycolysis? Is there an advantage?

Answer 34

1. One possible advantage is the glycolysis leads to an increase in anabolic substrates for lipid, protein synthesis, etc. 2. Decreases the reliance on the mitochondria

Question 35

Cancer cell growth is limited to areas surrounding blood vessels, What is the result of this?

Answer 35

- decrease of oxygen consumption - increase in growth radius - reduced use for mitochondrial function to conserve oxygen located in cells not near the blood vessel

Question 36

How does the tumour microenvironment effect (fibroblast, endothelial cell and immune cells) the acquired traits?

Answer 36

- fibroblasts contribute to the support that allows cancer cells to grow large - endothelial cells, stimulated by VEGF, allows cancer cells to enter the blood stream - immune cells with their surveying and editing has allowed the cancer cell to avoid the editing and will seed eslewhere