Alexandru C. Stan, M.D., Ph.D. Professor of Neuropathology
Institute of Neuropathology
Brain tumor invasiveness; Glioblastoma angiogenesis; Multidrug resistance; Prodrug therapy
Our research is focussed onto two major problems encountered in the therapy of glioblastoma. First, glioblastoma is a highly invasive brain tumor. This property obviously determines a lower treatment success rate than might be expected for tumors, which almost never metastasize. In this process, the CD44 adhesion molecule has apparently a major function in regulating the adhesive and locomotory properties of glioblastoma cells, since during invasion, homotypic adhesion is reduced with a concomitant increase in heterotypic adhesion. Second, the multidrug-resistance (MDR) phenotype of glioblastoma is associated with over-expression of P-glycoprotein (P-gp, P-170) encoded by the multidrug-resistance-1 (MDR1) gene. P-gp facilitates active efflux of various xenobiotics, thus significantly lowering their therapeutic efficacy. We have previously demonstrated that local treatment with an anti-CD44s monoclonal antibody can strongly inhibit glioblastoma invasion, thus blocking tumor growth. We have also demonstrated that an enzymatically-engineered doxorubicin-mAb anti-CEA immunoconjugate is about 8-times more efficient in killing colonic carcinoma tumors than doxorubicin itself with virtually no side-effects. We have further demonstrated that doxorubicin can circumvent the P-gp-associated chemoresistance in glioblastoma cells, provided that the drug can persist intracellularly for as long as 24h.
- To target the highly potent chemotherapeutic substance doxorubicin, which is enzymatically engineered on the carbohydrate moieties of a monoclonal antibody to CD44s, the 85-90 kDa standard form of the CD44 adhesion molecule that is over-expressed by glioblastoma cells.
- To target anti-sense phosphorothioate oligo-deoxynucleotides, which are likewise enzymatically engineered on the anti-CD44s monoclonal antibody to P-glycoprotein that is over-expressed by endothelial cells within glioblastoma's vasculature. Using this combined therapeutic strategy we expect a dramatic increase of the drug's efficacy in killing tumor cells, which otherwise become resistant to conventional chemotherapy:
- High amounts of doxorubicin are shuttled into glioblastoma cells by the antibody due to over-expression of the CD44 adhesion molecule on the cell surface.
- High amounts of anti-sense phosphorothioate oligodeoxynucleotides are shuttled into endothelial cells by the antibody due to an improved linking procedure.
- High intracellular accumulation of "bio-active" doxorubicin is due to lack of lysosomal degradation of CD44 within glioblastoma cells.
- High intracellular retention of "bio-active" doxorubicin is due to suppressed expression of P-glycoprotein within endothelial cells.
Alexandru C. Stan, M.D., Ph.D., Prof.; Hans H. Wellhoener, M.D., PhD., Prof.;Veronika Thorns, M.D.; Sadanand Gaikwad, M.Sc.; Farid A. Jamai, cand. med.; Stephanie Alm, Technician
- Cell culture and cell transformation
- PCR, RT-PCR
- Blotting (northern, western)
- ELISA (cytotoxicity, apoptosis)
- FACS (miscellaneous)
- Histology and Immunohistochemistry
- Experimental animal treatment (mouse, rat)
- Stan A.C., Radu D.L., Casares S., Bona C.A., and Brumeanu T.-D. Antineoplastic efficacy of Doxorubicin enzymatically assembled on galactose residues of a monoclonal antibody specific for the carcinoembryonic antigen. Cancer Res. 59: 115 - 121 (1999).
- Stan, A.C., Casares S., Brumeanu T.-D., Klinman D.M., and Bona C.A. CpG motifs of DNA vaccines induce the expression of chemokines and MHC class II molecules on myocytes. Eur. J. Immunol. 31(1):301 - 310 (2001).
- Casares S., Stan A.C., Bona C.A., and Brumeanu T.-D. Antigen-specific downregulation of T cells by doxorubicin delivered through a recombinant MHC II-peptide chimera. Nat. Biotechnol. 19(2): 142 - 147 (2001).