Therapeutic Targeting CNS Tumours

Question 1

Challenges for the treatment of brain tumours?

Answer 1

• BBB
• Tumour resistance
• Heterogeneity
• Diffusing nature of some tumours
• Invasive of local delivery to the brain

Question 2

What properties of drugs are needed to cross BBB?

Answer 2

Lipophilic and low molecular weight

Question 3

Can chemotherapy drugs cross BBB?

Answer 3

Not well at all

Question 4

Common anti cancer drug?

Answer 4

Temozolomide

Question 5

Why p-glycoproteins are barrier to chemotherapy?

Answer 5

Act as efflux pumps, pumping anti-cancer drugs out of the tumours

Question 6

Potential solutions to improve chemotherapeutic drug delivery?

Answer 6

• Intracranial infusion of arabinose/mannitol
• Convection enhanced therapy (CED)
• Polymeric Vesicles

Question 7

Properties of glioblastoma?

Answer 7

Very invasive and very aggressive (WHO classfied as grade IV glioma)

Question 8

Tumour cells___: receive nutrients via diffusion

Tumour cells ___: require their own vasculature

Answer 8

Tumour cells <2mm: receive nutrients via diffusion

Tumour cells >2mm: require their own vasculature

Question 9

Vascular targets in endothelial cells?

Answer 9

VEGF and VEGFR receptors, αvβ3 and αvβ5 integrins, MMP-2, MMP-9, EGFR

Question 10

Vascular targets in pericytes

Answer 10

aminopeptidases APA and APN, NG2 proteoglycan, PDGFRs

Question 11

Vascular targets in tumour cells

Answer 11

VEGF and VEGFR receptors, αvβ3 and αvβ5 integrins, MMP-2, MMP-9, EGFR

Question 12

Define gene therapy

Answer 12

Delivering a therapeutic gene to replace and correct an abnormal gene

Question 13

Examples of viral vectors?

Answer 13

retroviruses/lentiviruses- RNA, adenoviruses (Ad)- dsDNA, adeno-associated viruses (AAV)- ssDNA

Question 14

Examples of non-viral vectors?

Answer 14

• Lipoproteins (w/ aqueous core)

- Cation polymers (+ve region binds to -ve tumour cells)

Question 15

How to make a vector?

Answer 15

• Replace wild-type gene with the therapeutic gene
• Use a gene promoter e.g. CMV promoter (before the therapeutic gene)
• Use a PolyA sequence to stop transcription (after the therapeutic gene)

Question 16

Problems with eukaryotic viral vectors?

Answer 16

• Undesired uptake by liver
• Uptake by reticuloendothelial system (RES)
• Tropism for normal tissues
• Low penetrance for tumour tissues
• Presence of antiviral neutralising antibodies

Question 17

Advantages of Bacteriophage therapies?

Answer 17

• Safe (if no bacteria left, cleared within 3 days)
• Targeted (ligand-directed targeting)
• Cost-effective production at high titres
• No need to ablate for any tropism

Question 18

Types of Bacteriophage?

Answer 18

• Tailed: bacteriophage lambda (dsDNA)

- Filamentous: bacteriophage M13 (ssDNA)

Question 19

Describe bacteriophage entry

Answer 19

• Phage binds to pilus

- Phage DNA inserted into cell cytoplasm

Question 20

Advantages of RGD-AAVP?

Answer 20

• Specific for brain tumours (binds to αv-integrin receptor)
• IV delivery
• Easily crosses BBB
• Cheap to produce

Question 21

Typical medulloblastoma patient?

Answer 21

Most common brain tumour in children

high survival and high morbidity

Question 22

Medulloblastoma response to TMZ

Answer 22

It is resistant

Question 23

Treatment approaches for medulloblastoma?

Answer 23

• Short hairpin RNA (shRNA) to neutralise mRNA and block expression -> kills 40% of tumour cells
• Cilengitide (blocks integrins) -> small effect to block tumour growth
• Phage to deliver shRNA and block mTOR pathway and THEN give TMZ (as resistance is removed)

Question 24

Typical diffuse intrinsic pontine glioma patient (DIPG)

Answer 24

Young children

Question 25

What is chemovirotherapy?

Answer 25

Combining chemo-radiotherapy with gene therapy (e.g. AAVP+TMZ)

Question 26

Non-targeted AAVP without RGD: ___

TMZ: ___

RGD-AAVP and HSVTk: ___

RGD-AAVP with TMZ: ___

Answer 26

Non-targed AAVP without RGD: no effect

TMZ: small effect

RGD-AAVP and HSVTk: tumour shrinks slightly

RGD-AAVP with TMZ: 100% tumour cells eliminated