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

C. Transfer of other genes against
restenosis and arterial injury
A number of vascular disorders can be treated by
arterial gene transfer (Nabel et al, 1990, 1993a-c; Ohno et
al, 1994; Takeshita et al, 1994b; Chang et al, 1995a,b).
One of the drawbacks has been the low percentage of the
cells transfected which were in the order of 1% to less
than 0.1% using naked plasmid delivery with a balloon
catheter (e.g. Isner et al, 1996a), cationic liposomes (Nabel
et al, 1990, 1993a-c), or retroviruses (Flugelman et al,
1992). A variety of genes have been transferred into
arterial wall cells. Transfer of the human growth hormone
gene, a secreted protein, into rabbit arterial organ culture
using lipofectin permitted determination of hGH levels in
the culture medium using a sensitive immunoassay
method (Takeshita et al, 1994b). The ADA gene has been
transferred efficiently to vascular smooth muscle cells in
rats (Lynch et al, 1992). Transfer of the fibroblast growth
factor-1 gene (Nabel et al, 1993b), of the platelet-derived
growth factor B gene (Nabel et al, 1993c), or of the
transforming growth factor-β1 gene (Nabel et al, 1993a,b)
into animal arteries promoted intimal hyperplasia and
angiogenesis.
The therapeutic induction of angiogenesis in ischemic
tissues using recombinant cytokines is also promising for
clinical application (Norrby, 1997).
In vivo suppression of injury-induced vascular smooth
muscle cell (VSMC) accumulation is a widely used
approach (Ohno et al, 1994). Other than VEGF gene
transfer (Isner et al, 1996a, see above), additional
approaches for the treatment of restenosis after injuryinduced
VSMC accumulation is via delivery of the HSVtk
gene followed by ganciclovir treatment in order to kill
preferentially the smooth muscle cells (Guzman et al,
Gene Therapy and Molecular Biology Vol 1, page 105
105
1994; Ohno et al, 1994); by transfer of the cytosine
deaminase (CD) gene the product of which is capable of
metabolizing 5-fluorocytosine (5-FC) to 5-fluorouracil in a
rabbit femoral artery model of balloon-induced injury
(Harrell et al, 1997); by transfer of the RB (Chang et al,
1995a; Smith et al, 1997), or p21 genes (Chang et al,
1995b); by transfer of ras (Indolfi et al, 1995), TGFβ gene
(Grainger et al, 1995); and, by transfer of the nitric oxide
synthase gene (von der Leyen et al, 1995).
At the molecular level, arterial injury results in
exposure of vascular smooth muscle cells (VSMC) and
fibroblasts to multiple growth factors that activate second
messengers and induce expression of immediate-early
genes within minutes to hours after stimulation resulting in
the exit of VSMC from the quiescent G0 state. A series of
CDKs are activated and tumor suppressor genes need to be
down-regulated for VSMC proliferation including p53,
p21, p16, and RB (reviewed by Muller, 1997). Therapeutic
strategies to restrict neointima formation in the injured
artery include (i) inhibition in the expression of protooncogenes
(c-myc); (ii) transfer of suicide genes (HSV-tk,
CD); (iii) use of molecular decoys or drugs to block
specific steps required for cell cycle progression, (iv)
transfer of tumor suppressor genes (p21, RB); (v)
treatment with antisense oligonucleotides to down regulate
genes required for cell proliferation or DNA synthesis
(antisense cyclin G1, PCNA); (vi) transfer of a number of
unrelated genes such as of gax, TGF-β, hirudin, PKCδ, βinterferon
(Table 7). It is worth considering that delivery
of recombinant adenoviruses themselves causes (i) a
pronounced infiltration of T cells throughout the artery
wall; (ii) upregulation of intercellular adhesion molecule-1
and vascular cell adhesion molecule-1 in arterial smooth
muscle cells; (iii) neointimal hyperplasia (Newman et al,
1995).