Cell Signalling And Rational Therapies

Question 1

MAPK pathway

Answer 1

Ligand binds to MAPK eg. EGF
Dimerisation and phosphorylation of intracellular receptor
Recruitment of GRB2, SOS
Recruitment of Ras GDP
Ras activated by GTP
Recruitment of B-raf
Activation of MEK1/2,ERK1
Activation of transcription factors and gene expression e.g. STAT1/3
Ras GTP switched off

In cancer: Ras GTP not switched off = ⬆️ cell proliferation

Question 2

How does Ras act as an oncogene

Answer 2

Increases proliferation of cell if not switched off.

Can activate many kinases if activated

Question 3

PI3K pathway

Answer 3

Activation of kinase receptor by ligand
PI3K binding and activation
Phosphorylation of PIP2 to PIP3
Activation of AKT
1) Binds to BAX - inhibition if apoptosis
2) inhibits TSGs such as p53 by phosphorylation of MDM2

AKT and MDM2 are proto oncogenes

Question 4

Two ways to inhibit kinase

Answer 4

Intracellular kinase inhibitors eg. bcr abl

Monoclonal antibodies eg. Imatinib

Question 5

What is PTEN

Answer 5

Dephosphorylates PIP3
Inhibits activation of AKT
May be involved in regulation of cell growth

Question 6

-nib
-mab
Suffixes

Answer 6

Nib = kinase inhibitors
Mab = monoclonal antibodies

Question 7

Function of protein kinases

Answer 7

Can promote of inhibit enzyme action

Question 8

Vemurafenib action

Answer 8

Interrupts MAPK pathway - cell death in melanoma cells

Question 9

Mechanism of action of Imatinib

Answer 9

Targets BCR ABL
ABL is a tyrosine kinase which controls cell differentiation and DNA repair in some cells
Imatinib also targets some receptor tyrosine kinases
Prevents ABL phosphorylating its substrates

Question 10

Imatinib resistance

Answer 10

Amino acid change in ABL which prevents binding of imatinib to ABL

Question 11

Carboplatin resistance

Answer 11

Resistance to apoptosis

Question 12

2 second generations of Imatinib

Answer 12

Nilotinib and dasatinib
Can overcome 32/33 resistant mutations
Neither inhibit T315I

Question 13

3rd generation of drugs

Answer 13

Ponatinib

Overcomes resistance of amino acid change in imatinib

Question 14

How does Imatinib target tyrosine kinases

Answer 14

In mast cell leukemia
Imatinib used in mutated receptors
Resistance does occur in 75% of cases

Question 15

Resistance in mast cell leukemia

Answer 15

Kinase jammed in active position

Imatinib cannot bind

Question 16

EGFR kinase inhibitor examples

Answer 16

Gefitinib or erlotinib - NSCLC
Many responders found to have mutations in kinase domain of EGFR.
Mutant EGFR may activate PI3K/Ark pathway - inhibit apoptosis
Resistance can develop that block binding of drugs

Question 17

Method to make a kinase inhibitor

Answer 17

model compounds to see if they fit the domain
FMS inhibitor screen:
Add compounds to cells, see if they grow
Check weather inhibitor stops phosphorylation of receptors to check if they inhibit or kill cell
Need to use minimum drug amount that is effective.
Too much will lose specificity