immunologic rejection of the transduced cells and also produced transplantation resistance 
against the parent tumor cells (58). In another instance, transfection of H-2^ melanoma 
cells with the H-2D<^ gene did not lead to rejection (59), however increased differential 
expression of H-2D products relative to H-2K may have affected the metastatic potential 
and immunogenicity of tumor cells (60). The effects of allogeneic H-2K gene expression in 
tumor cells was examined in another study (61). Several subclones which were selected in 
vitro and expressed an allogeneic gene were rejected in mice syngeneic for the parental 
tumor tine, however, other subclones did not differ from the parental, untransduced line in 
generating tumors. This finding suggests that clone-to-clone variation in in vivo growth 
and tumorigenic capacity may result in other modifications of cells caused by transfection 
or the subcloning procedure, which affects their tumorgenicity. These types of clonal 
differences would likely be minimized by transducing a population of cells directly in vivo. 
Because the H-2K class I MHC antigen is strongly expressed on most tissues and can 
mediate an allogeneic rejection response, we chose it in our animal model studies designed 
to enhance the immunogenicity of tumors in vivo. These studies extended previous efforts 
to modify tumor cells by developing a system for the direct introduction of genes into 
tumors by in vivo infection using retroviral vectors or by DNA lipid complex mediated 
transfection. This technology can also be used to deliver specific recombinant cytokines into 
the tumor microcirculation and to understand the immunologic basis for tumor rejection in 
vivo. 
1.2.3 Intra-lesional Therapy 
The Department of Diagnostic Radiology at the University of Chicago has extensive 
experience in CT and sonographically-guided needle biopsy. Sonographically— guided 
biopsy of metastatic lesions can be carried out with a high degree of accuracy and safety. It 
is almost always possible to obtain a core rather than an aspirate of tissue by using a 16-19 
gauge needle, needles with cutting ends, and improved biopsy sampling technology. In a 
review from the Mayo Clinic, overall accuracy was 91% in the biopsy of 126 consecutive 
masses of various histologic types 3cm or less in diameter. It is almost always possible to 
obtain a core rather than an aspirate of tissue by using a 16-19 guage needle, needles with 
cutting ends, and improved biopsy sampling technology. In a study from the May Clinic of 
1,000 consecutive CT-guided biopsies, the rate of complication from the use of an 18-guage 
biopsy needle was 0.3%, the same as the rate of complication from the use of a 21-guage 
needle. This capability allows, in one sitting, biopsy of the intended target for gene transfer, 
documentation of metastatic cancer in the lesion, and delivery of the DNA/liposomal 
mixture to the targeted nodule(s). For purposes of this protocol, nodules 2-4 cm in size that 
are easily accessible will be selected to further ensure successful target injection and to 
reduce the possibility of morbidity. 
One advantageous feature of sonographically-guided delivery of DNA/liposomal complex 
is that the distribution of the fluid within the injected area can be visualized and 
documented on videotape. Apparently, the release of small bubbles from dissolved air in 
fluids at room temperature injected into tissue causes the area perfused to become hyper 
echoic. This allows the radiologist to observe the regions of the nodule being injected. 
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Recombinant DNA Research, Volume 19 
