01. Gene therapy Boulikas.pdf - Gene therapy & Molecular Biology

significant reduction in neointima formation (Ueno H et
al, 1997b).
Nitric oxide-generating vasodilators inhibit vascular
smooth muscle cell proliferation. S-nitroso-Nacetylpenicillamine
(SNAP), a nitric oxide-releasing
agent, inhibited the activity of cyclin-dependent kinase 2
(Cdk2) and the phosphorylation of RB but it did not
inhibit the activities of cyclin D-associated kinases Cdk4
and Cdk6 (Ishida et al, 1997). Suppression of injuryinduced
vascular smooth muscle cell accumulation was
also achieved by transfer of the endothelial cell nitric
oxide synthase gene (von der Leyden et al, 1995). Based
on the fact that administration of the nitric oxide (NO)
synthase inhibitor L-NAME to rabbit carotids eliminated
the difference in intimal thickening between VEGF and
mock-transfected (lacZ) arteries it was proposed that
VEGF may reduce smooth muscle cell proliferation via
VEGF-induced NO production from the endothelium
(Laitinen et al, 1997).
D. Atherosclerosis
The atherotic plaque is formed by a complex
mechanism initiated by the accumulation of lipid,
macrophages and T cells at artery lesions leading to
smooth muscle cell proliferation (Ross, 1993). TGF-β is
involved in atherosclerosis via its activation by plasmin
and via its inhibition by atherogenic lipoprotein deposited
on the arterial wall. Inhibition of TGF-β would lead to
smooth muscle cell proliferation; patients with advanced
coronary disease have decreased serum TGF-β levels;
furthermore, transgenic mice overexpressing lipoprotein
(a) exhibit decreased levels of TGF-β at sites of
lipoprotein (a) accumulation such as in the aortic wall
(Grainger et al, 1995). As prolonged overproduction of
TGF-β may lead to tissue fibrosis by overproduction of
extracellular cell matrix (Border and Noble, 1995) a
balanced overexpression of TGF-β might be of great
therapeutic value for heart disease.
The plasminogen system, via its triggers, t-PA and u-
PA and its inhibitor, plasminogen activator inhibitor-1
(PAI-1), has been implicated in thrombosis, arterial
neointima formation, and atherosclerosis (reviewed by
Carmeliet et al, 1997).
A number of animal models have been used to induce
atherosclerotic lesions such as the iliac arteries of New
Zealand white rabbits fed with cholesterol. Substantial
progress in vector development and the demonstration of
efficacy in relevant animal models will be required before
gene therapy for atherosclerosis becomes a clinical reality
(Rader, 1997).
E. Acidic and basic fibroblast growth
factors (aFGF, bFGF)
Gene Therapy and Molecular Biology Vol 1, page 109
109
Acidic and basic fibroblast growth factors and their
receptors are involved in many fundamental biological
processes but also in pathological processes (Webster and
Donoghue, 1998, this volume).
Whereas VEGF is a regulator of vascular permeability
and an endothelial cell growth factor the acidic and basic
fibroblast growth factor (aFGF, bFGF) and placenta
growth factor (PGF) polypeptides are endowed with
endothelial cell growth-promoting activity; however,
FGFs have not been reported to be expressed in blood
vessels in vivo. aFGF and bFGF seem to act as mitogens
for a large number of different cell types; in situ
hybridization analysis has shown that there is no
expression of FGF receptors 1 and 2 (Flg and Bek) in
capillary endothelial cells during embryonic development;
it is only VEGF and PGF which are known to be specific
for endothelial cells (for references see Millauer et al,
1993).
Many of the studies that have demonstrated therapeutic
efficacy using fibroblast (aFGF, bFGF, FGF-5),
endothelial (VEGF) and other types of factors using the
purified peptides can potentially be transferred to the gene
level. This will not require repeated administration of the
drug, especially whenever the somatic cell targets are
transfected efficiently and the expression of the transgene
lasts.
Liposome-mediated gene transfer of antisense-oriented
bFGF or fibroblast growth factor receptor-1 (FGFR-1)
cDNAs in episomal vectors into human melanomas,
grown as subcutaneous tumors in nude mice caused
complete arrest or regression of the tumors as a result of
blocked intratumoral angiogenesis and subsequent
necrosis (Wang and Becker, 1997). Inhibition of bFGF
synthesis in vivo using an antisense RNA strategy
significantly inhibited intimal thickening after arterial
balloon injury (Hanna et al, 1997).
Infection of human umbilical vein endothelial cell
cultures with a bFGF-expressing recombinant adenovirus
enhanced the proliferation rate and tubular formation of
these cells on reconstituted basement membrane
(Takahashi et al, 1997). Low level expression of bFGF
upregulated Bcl-2 and delayed apoptosis in NIH3T3 cells;
on the other hand cells expressing from 8-15 times
background levels of bFGF became phenotypically
transformed (gave dense foci at confluence, had decreased
adherence to tissue culture plates and grew colonies in soft
agar) (Wieder et al, 1997). Blood vessels of spontaneously
hypertensive rats were shown to be associated with
subphysiological amounts of bFGF; transfer of the bFGF
gene corrected hypertension, restored the physiological
levels of bFGF in the vascular wall, and ameliorated
endothelial-dependent responses to vasoconstrictors
(Cuevas et al, 1996).