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 GEM 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 GEM, 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 GEM cells and tumors. Flow cytometric analysis demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 mu g/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 +/- 0.48 [SD])-measured as the quotient: tumor surface (mm(2))/brain surface (mm(2)) 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 GEM 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.