Transcript Gene augmentation

Newer cancer therapies
immunotherapy
angiotherapy
gene therapy
Angiotherapy
Key differences in tumour
vasculature
Different flow
characteristics /
blood volume
Microvasculature
permeability
Increased
fractional
volume of
extravascular,
extracellular
space
Angiogenesis-overview
Balance
between
inhibitory factors
(endostatin) and
angiogenic factors
(VEGF, bFGF)
angiogenic
factors
stimulate MMPs and
plasminogen
activators
Degradation
of
basement membrane
Invasion and
differentiation of
endothelial cells in
surrounding tissues
BLOOD FLOW
Before treatment
after treatment
MMPIs

Disappointing results with matrix
metalloproteinase inhibitors

Poor survival rate in phase III clinical trials
against renal cell carcinoma
Newer cancer therapies
gene therapy
Gene therapy
Antisense therapy
(suppress gene expression)
Gene augmentation
(supplement defective gene)
Antisense therapy
compensates for genetic
mutations that produce
destructive proteins
Main strategies involved are
1) short stretches of synthetic
DNA that target the mRNA
transcripts of abnormal
proteins preventing its
translation OR
small
RNA
molecules
(siRNA) used to degrade
aberrant RNA transcripts
Antisense therapy
2) provide a gene for a protein (intracellular
antibody) that can block the activity of the
mutant protein
3) design hybrids of DNA / RNA that might
direct repair of the mutant gene
Gene augmentation
most therapies simply add a useful gene into a
selected cell type to compensate for the missing or
flawed version or even instil an entirely new
version.
Direct approach
inducing cancer cells to make a protein that will kill
the cell.
Indirect approach
stimulating an immune response against selected
cells or eliminating the blood supply.
3 challenges in gene therapy
delivery
delivery
delivery
1) Package the gene
2) Protect the gene
3) deliver to the nucleus and release
in an active form
Vectors
‘Trojan horses’ that sneak the gene into the cell
Vectors
Carrier molecules designed
specifically to enter cells & deposit
therapeutic genes
Vectors can be viral or non-viral
METHODS OF VECTOR DELIVERY
Viral vector strategy
Replication & virulence genes can be
substituted with therapeutic genes
Retroviral vectors
designed to enter cell and deposit genes
Problems of retroviral therapy include
Lack of cell specificity:
Promiscuous: depositing genes into
several cell types resulting in reduced
target efficiency and unwanted
physiological effects
Random splicing into host DNA
resulting in normal gene disruption
and/or alteration in gene function
Adenoviral vectors
do not insert into
genome
temporary
lack of specificity
strong immune
response
Adeno-associated viral vectors
Integrate
into
genome but
small in
size
Nature Reviews Genetics
1; 91-99 (2000);
Conditionally replicating viruses
Non-viral Vectors
Advantages
non-toxic
no immune response
Non-viral Vectors
liposomes (lipoplexes)
Non-viral Vectors
amino acid polymers: cationic polymers
e.g. B-cyclodextrins
Non-viral Vectors
Gene gun
naked DNA
artificial human chromosomes
Tumour-suppressor gene delivery
Nature Reviews
Cancer (2001)
Vol 1; 130-141
Delivery of agents that block
oncogene expression
Nature
Reviews
Cancer
(2001)
Vol 1; 130141
Suicide gene delivery
Nature Reviews Cancer (2001) Vol 1; 130-141