Development of Gene Imaging Technique Using Radiolabeled Antisense DNA

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08457241
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Radiation science
• Research Institution: Kanazawa University
• Principal Investigator: TONAMI Norihisa Kanazawa University School of Medicine, Professor, 医学部, 教授 (60019940)
• Co-Investigator(Kenkyū-buntansha): SHIBA Kazuhiro Kanazawa University Radioisotope Center, Assistant, アイソトープ総合センター, 助手 (40143929) ; YOKOYAMA Kunihiko Kanazawa University Hospital, Lecturer, 医学部・附属病院, 講師 (60230661)
• Project Period (FY): 1996 – 1997
• Keywords: antisense DNA / oligonucleotide / radioisotope / imaging diagnosis / gene imaging / delivery system / induced hypertension

Research Abstract

Using radiolabeled antisense oligonucletides(DNA), lesions of amplified mRNA can be imaged with gamma cameras. For this approach, the stable radiometal chelates, which are appropriate for oligonucletide, is required. We have developed the in vivo model system where nude mice xenografted tumor cells express P-glycoprotein (P-gp). To image multidrug resistant tumors caused by P-gp, we designed the 15mer of antisense DNA sequence for the mdrl gene coding P-gp. The 5'-end of the oligonucletide was modified with the thiol group and the maleimido-C3-benzyl-EDTA chelate was reacted. However, the final product was not identified as the objective compound. Further investigation was warranted. The small molecules like oligonucleotides tend to be cleared very rapidly from the blood and therefore, the absolute tumor uptake of this kind of the tracer is limited. We have tried to increase the tumor uptake of radiolabeled antibodies by modifying the hemodynamics of the tumor tissue. The combination usage of angiotensin-Il, continuously infused at 2 mug/kg/min, and a kininase inhibitor, enalapril maleate, 30 jig increased the mouse blood pressure from 95/61 to 153/67. And the tumor uptake was also increased by the factor of 1.62 with little change in normal organ distribution. The autoradiography showed that more homogeneous distribution of the radiolabeled antibody in the tumor because of recanalization of vascular beds and increased vascular permeability. In conclusions, enhanced tumor uptake was achieved by manipulating hemodynamics and vascular permeability of the tumor tissue and this technique can be applied for smaller molecule as the oligonucleotides.