ABSTRACT 
Scientific Abstract 
The following protocol represents a treatment approach to otherwise 
incurable malignant human brain tumors that is based on an antisense gene 
therapy strategy. This antisense strategy has been used to cause complete regression 
of malignant gliomas in rat brain. We and others have shown that the C6 glioma 
cell line produces an overabundance of insulin-like growth factor (IGF-I). We 
designed an episome based vector to produce multiple copies of itself when inside of 
the cell, and to express RNA that is anti-sense to IGF-I. Using this vector, we have 
demonstrated a complete suppression of IGF-I synthesis in transfected C6 glioma 
cells. Injection of the transfected cells subcutaneously into rats bearing C6 glioma 
tumors results in complete regression of tumor. This occurs whether the tumor is 
within the cranium or in an extracranial site at a point distant to the site of injection 
of the transfected cells. We have further shown that the mechanism which results 
in destruction of tumor includes the promotion of a CD8 T cell-mediated immune 
response which is selective for the glioma cells. In mixed tumors containing both C6 
glioma and neuroblastoma, the T cell driven immune response remains targeted 
selectively to the glioma cells. This strategy of treatment is proposed in the protocol 
which follows. First, we will select patients with gliomas which over-express IGF-I. 
Second, these patients will be treated with the anti-sense strategy using the episome 
based vector. Finally, in the first phase of this trial we will determine toxicity which 
may define the limits of use for this methodology. The second phase of this study 
will determine efficacy as defined by changes in survival, time to tumor progression 
and/or to tumor regression. 
This approach to gene therapy for human brain cancer has several unique 
advantages. First, the episome based vector includes component parts of a virus 
that commonly infects humans and although capable of driving extrachromosomal 
episomal replication, does not reproduce active virus. Second, the large copy 
number of the vector within transfected cells insures the expression of antisense 
RNA quantities sufficient to inhibit the production of IGF-I. Third the technique 
will not require stereotactic injection into the site of malignancy, hence surgically 
invasive procedures over and above those ordinarily used to diagnose and treat 
such brain tumors will not be needed. Finally, the mechanism for tumor 
distruction includes a selectively targeted T lymphocyte mediated immune response 
leading to the prediction that complicating toxicity should be low. 
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Recombinant DNA Research, Volume 18 
