| Research Abstract |
The glioma-associated antigen, which mouse monoclonal antibody ONS-M21 (Br J Cancer, 1999) recognized, was integrin alpha3. The expression of integrin alpha3 in the normal brain has been reported to be very low or even undetectable. It appears that the level of this antigen expressed in glioma is correlated with the grade of malignancy and invasion. It is, therefore, very important to investigate integrin alpha3 in glioma cells in order to expect the prognosis of their patients. On the other hand, in the experimental gene therapy of glioma with retroviral vectors reconstructed brain-specific promoter, myelin basic protein (MBP) promoter (Hum Gene Ther, 1997 ; Gene Ther, 1998), it is demonstrated that mouse glioma models were completely recovered with intraperitoneal administration of ganciclovir (GCV), if herpes simplex thymidine kinase (HTK) could be introduced into about 25 % of glioma cells. To obtain high-titer recombinant retroviruses, we constructed plasmid pDL^#, which carries t
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he extended Psi region and the polyomavirus early region, including the replication origin and the early gene. Then we modified the packaging cell lines, PA317, by stably introducing the polyomavirus early gene, and established PAMP5 1 from PA317 cells (Hum Gene Ther, 1998). In vivo experiments by using these high-titer recombinant retroviruses, 80 % of mouse glioma models were completely recovered (Hum Gene Ther, in submitted). In this way we could get very effective vectors, but we could not get therapeutic effects at all by these vectors, if tumor does not have retrovirus receptors. For the tumors that did not have these receptors, we investigated the delivery of HTK genes into glioma cells in vivo using hemagglutinating virus of Japan (HVJ)-liposomes, which are coated by Sendai virus envelope protein. Highly efficient delivery was observed in disseminated glioma cells of MG mice, and 8O0/c of these mice expressing the HTK gene were cured by administration of GCV (Gene Ther, 1997). And moreover, we will thoroughly investigate more specific gene therapy for glioma by HVJ liposome-binding humanized (Mol Immunol, 1995) or single-chain antibodies (Anticancer Res, 1998). When humans medulloblastoma ONS-76 cells were co-cultured with ONS-M21 antibodies, about 20% antibodies were internalized into these cells for less than 30 minutes (Cancer lett, 1998). A cytotoxic effect against ONS-76 cells was found by the iminunotoxin which was bounded with ricin A chain and ONS-M21 antibodies, but not against antigen-negative human hepatoma HuH-7 and colon cancer SW480 cells. These results suggest that ONS-M2 I antibodies could effectively deliver toxins, chemotherapeutic agents or radionuclei to malignant glioma specifically. Now we, however, try to transduce HTK genes into the glioma cells by installments, because the molecular weight of HTK genes-binding ONS-M21 is too big to introduce HTK gene complex by the lump. Less
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