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

of a PAX5 and p53 genes in the same expression vector
but with the wt p53 mutagenized at 2-3 nucleotides to
abort the PAX5 suppressive site was proposed as a
strategy to effectively suppress tumor cell proliferation
(Boulikas, 1997).
I. p53 gene bombs that explode in cancer
cells
Exogenous genes encoding "weapons" (suicide genes)
and "triggers" have been devised whose delivery to
somatic cells will affect only cancer cells. The production
of mutated forms of p53 at high levels by cancer cells
Boulikas: An overview on gene therapy
Figure 22. Involvement of p53 and Pax5 in B cell apoptosis. Adapted from Stuart et al (1995).
the absence of transfection of these cells, a phenomenon
known as "bystander effect".
Trigger genes in plasmids were made up of the DNAbinding
domain of GAL4 (aa 1-147) fused in frame to a
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(normal cells do not have adequate amounts of wt p53
protein) is being exploited to pull a molecular trigger
resulting in the transcriptional activation of a toxic gene
and in the death of cancer cells (da Costa et al, 1996). This
invention is based on the fact that (i) powerful chimeric
transcription factors can be engineered consisting of a
DNA-binding domain (DBD) and a transactivation domain
(TAD) and (ii) prokaryotic or viral enzymes are able to
convert nontoxic prodrugs into toxic derivatives (suicide
genes, see HSV-tk, CD and PNP further below); the toxic
derivative produced in tumor cells which are transfected
can diffuse to surrounding cells causing their killing even
in
protein domain that could interact with p53; the p53binding
domain was the 84-708 aa region of SV40 T
antigen or of the 305-393 aa TAD domain of p53 (which
acts as a tetramer) and which is similar between wt and