Disruption of intracerebral progression of C6 rat glioblastoma by in vivo treatment with anti-CD44 monoclonal antibody.

OBJECT: Glioblastoma multiforme (GBM) invasiveness is a complex process that involves recognition and attachment of GBM cells to particular extracellular matrix (ECM) molecules before migrating into proteolytically modified matrix and inducing angiogenesis. The CD44 molecule, which is a transmembrane adhesion molecule found on a wide variety of cells including GBM, has been suggested as the principal mediator of migration and invasion. The aim of the present study was to demonstrate whether an antibody specific to the standard form of CD44 (CD44s, 85-90 kD) might prevent invasion and thus disrupt progression of C6 GBM in vivo. METHODS: Immunostaining demonstrated homogeneous expression of CD44s on the surface of C6 GBM cells and tumors. Flow cytometric analysis demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 microg/5 x 10(5) cells. Blocking of CD44s in vitro resulted in a dose-dependent progressive (up to 94+/-2.7%; mean +/- standard deviation [SD]) detachment of C6 cells from ECM-coated culture. Blocking of CD44s in vivo resulted in significantly reduced C6 brain tumors (3.6+/-0.4% [SD])--measured as the quotient: tumor surface (mm2)/brain surface (mm2) x 100--compared with untreated (19.9+/-0.9%) or sham-treated (19.2+/-1.1 to 19.3+/-2.5% [SD]) rats. Disruption of C6 GBM progression correlated with an improved food intake; treated rats were significantly less cachectic (166.6+/-16.4 g [SD]) than those that were untreated (83+/-2.7 g [SD]) or sham-treated (83.4+/-1.1 to 83+/-2.2 g [SD]) rats. CONCLUSIONS: The authors conclude that CD44s-targeted treatment with specific mAb may represent an effective means for preventing progression of highly invasive GBMs.

CD44s-targeted treatment with monoclonal antibody blocks intracerebral invasion and growth of 9L gliosarcoma.

Glioma invasiveness is a complex process involving recognition and attachment of tumor cells to particular extracellular matrix (ECM) molecules prior to migrating into proteolytically modified matrix and inducing angiogenesis. CD44 is a group of transmembrane adhesion molecules found on a wide variety of cells including gliomas that has been suggested as the principal mediator of migration/invasion. The aim of the present study was to demonstrate whether antibody specific for the standard form of CD44 (CD44s, 85-90 kDa) might prevent invasion, thus blocking growth of the 9L gliosarcoma in vivo. High expression of CD44s on the surface of 9L cells and brain tumors was demonstrated by immunochemistry. Fluorescence-activated cell sorting (FACS) demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 microg/5 x 10(5) cells. Blocking of CD44s in vitro resulted in a dose-dependent progressive, up to 95%+/-2.5% detachment of 9L cells from ECM-coated culture surfaces. Blocking of CD44s in vivo resulted in significantly reduced 9L brain tumors (2.5%+/-0.4%)--measured as the quotient: tumor surface (mm2)/brain surface (mm2) x 100--as compared to untreated (16.1%+/-2.2%) or sham-treated rats (16%+/-3.7% to 16.1%+/-3%). We conclude that CD44s-targeted treatment with specific mAb may be an effective means for preventing glioma progression.

[Inhibition of angiogenesis and growth of malignant gliomas in the athymic nude rat model: immunotherapy against "basic fibroblast growth factor"]. / Hemmung von Angiogenese und Wachstum maligner Gliome am Modell der Athymischen Nacktratte: Immuntherapie gegen "Basic Fibroblast Growth Factor".

An important feature of malignant progression in human gliomas is increased polymorphism of tumor cells associated with karyotypic heterogenity and a variety of secondary changes, one of which is increased angiogenesis. The capability of brain tumors for angiogenesis most probably is the earliest sign for malignancy in 95% of cases and occurs before typical changes of histology appear. Malignant brain tumors are known to produce several angiogenic growth factors. One of the most potent of these factors is the basic fibroblast growth factor (bFGF). In an experimental study human U87 MG glioma cells (2.10(5) cells/50 microliters) were implanted through a burrhole into the cerebral cortex in a group of 25 nude rats. After 3 weeks we found a reproducible extensive tumor growth with extensive neovascularization. Immunohistochemical evaluations proved a high expression of bFGF in the tumor. A parallel group of xenotransplanted rats were treated with 33 micrograms of rabbit anti-bFGF antibodies during tumor cell implantation. Thereafter, the same dosages of antibodies were administrated intracranially twice a week for 3 weeks. We found a significant inhibition of tumor vascularization and growth compared to other groups who had no treatment or who received irrelevant immunoglobulins or saline as a control. Our results indicate that inhibition of tumor angiogenesis might contribute to inhibition of tumor growth in malignant gliomas.