Cancer 3

Question 1

What is melanoma?

Answer 1

Skin cancer- derived from melanocytes (moles)

Question 2

What are the risk factors for skin cancer?

Answer 2

Age- accumulate mutations
Sex- higher risk in makes- psychosocial? hormones?
Skin colour- 24x higher risk for white skin
Sunburn UV exposure
GENETICS

Question 3

Which mutations can predispose you to develop skin cancer?

Answer 3

Mutated DNA repair genes- xeroderma pigmentosum
Mutated melanocortin receptor
Mutated CDKN2A/P16/P14- send cells to apoptosis when theyre damaged
Rare TERT promoter mutations- activate TERT expression- cells which shouldve died survive

Question 4

What do melanoma cells constitutively express?

Answer 4

MAPK

Question 5

What are the 2 types of initiator mutations of melanoma?

Answer 5

BRAFV600E

NRAS

Question 6

Mutations often seen in progressing stages

Answer 6

TERT
SWI/ SNF- involved in chromatin remodelling
CDKN2A

Question 7

Later stage mutations in melanomas

Answer 7

P53

PTEN

Question 8

Why was yeast used to study melanomas? what was its drawback

Answer 8

To look at the cell cycle machinery

Yeast do not have upstream signals that activate genes

Question 9

What are the upstream signals we’re interested in and what model animal can we study them with?

Answer 9

EGF/RAS/MAPK

Drosophila and C.elegans

Question 10

When do we need to use a vertebrate model animal?

Answer 10

To look at tumour growth and metastasis- specifically angiogenesis and the immune system

Question 11

Explain: Tyr:CreERT2

Answer 11

Tyrosinase promoter (only in melanoctyes) activatable by tamoxifen

Question 12

Explain: Brafca

Answer 12

Cre-activatable form of BRAF

Question 13

Explain: PTENlox

Answer 13

a loxed allele of PTEN- inactivated by Cre mediated excision

Question 14

What happens to CreERT2 when tamoxifen is introduced?

Answer 14

Cre-ERT2 will go into the nucleus and activate BRAF
PTEN will be will be activated
Need BRAF with the loss of PTEN to create a melanoma

Question 15

Whats characteristic of a mutant foxn1 mouse? Why are they not great in studying cancer?

Answer 15

Defective immune system

The immune system plays an important role in cancer- these mice are immunocompromised

Question 16

Whats an inhibitor of the BRAFV600E mutation? Which animal was involved in its discovery

Answer 16

PLX4032 is temporarily very effective against melanoma

The mouse

Question 17

Whats the downfall of PLX4032?

Answer 17

Only effective temporarily

And only inhibits the function of the BRAFV600E mutant

Question 18

What transgenic animal was used to screen for compounds that intefered with melanocyte precursor formation? What was the discovery?

Answer 18

Zebrafish
Tg mitfa:braf(V600E)
Melanomas have a neural crest progenitor sequence

Question 19

What followed the discovery that neural crest progenitor cells were involved in melanomas?

Answer 19

Chemical screen of 2000 chemicals that inhibited crestin

Question 20

What is crestin?

Answer 20

A marker for neural crest progenitors

Question 21

What was found to inhbit crestin? What drug is based on this compounds and hat does it do

Answer 21

NSC21067 - an inhibitor of DHODH

Leflunomide- increases the potency of PLX4032

Question 22

Which genes cause progression of melanomas? What was done to answer this question?

Answer 22

They knew it was a gene found in a region of chromosome 1 - tested candidate genes from this region
Melanoma assay on zebrafish
mitfa:braf (V600E) fish
test fish used: mitfa-/- fish in a P53-/- background
Engineered a vector- miniCoopR

Question 23

What did they do with the miniCoopR and what was the result?

Answer 23

injected each plasmid in the eggs of test line and found one that significantly enhanced cancer formation compared to mitfa alone - SETDB1

Question 24

What are the advantages of using zebrafish?

Answer 24

Cheaper than mice- can use greater numbers
can visualise cells etc using GFP
Can effectively do genetic/ chemical screens

Question 25

What was in the miniCoopR vector?

Answer 25

The mitfa promoter and a candidate gene