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. 
The Department of Diagnostic Radiology, May clinic-Rochester, has extensive 
experience in CT and sonographically- guided needle biopsy (see reviews by 
Charboneau et al., 1989, and Charboneau, 1991). Sonographically— guided biopsy of 
metastatic lesions in the liver can be carried out with a high degree of accuracy and 
safety. Overall accuracy was 91% in the biopsy of 126 consecutive masses of various 
histologic types 3cm or less in diameter in various anatomic locations. The accuracy 
increases to 98% for masses 2-3 cm in diameter, the range to which we will restrict 
delivery of DNA/liposome complex. Current techniques are not limited to this caliber 
(21-22) gauge needles). 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 study from the Mayo Clinic of 1,000 
consecutive CT-guided biopsies, the rate of complication from the use of an 18-gauge 
biopsy needle was 0.3%, the same as the rate of complication from the use of a 21-gauge 
needle (Welch et al., 1989). 
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). Virtually any region of the liver can 
be biopsied with safety. For purposes of this proposal, noduled 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. 
State-of-the-art facilities exist at Mayo for carrying out sonographically-directed 
biopsy and delivery of materials at deep sites in the body. Dr. Charboneau and his 
colleagues have now used 95% ethanol as an ablative agent in over 20 patients with 
hepatic tumors who were not candidates for other surgical or medical therapy. This 
has involved injecting solitary or, occasionally, up to three intrahepatic masses 5 cm or 
less in diameter. In most instances, 2-8 ml of ethanol is injected into multiple regions of 
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Recombinant DNA Research, Volume 18 
