CD44 expression and MMP-2 secretion by mouse glioma cells: Effect of interferon and anti-CD44 antibody

We have previously reported that invasiveness of mouse glioma G-26, which expresses CD44 adhesion molecule, was inhibited in vitro following treatment with anti-CD44 antibody or mouse interferon α/β (MuIFNα/β). Here, we evaluated whether the expression of transmembrane CD44 adhesion molecule and/or secretion of extracellular matrix metalloproteinases (MMPs) were affected when glioma cell invasion was inhibited. Flow cytometric evaluation of CD44 adhesion molecule expression in G-26 glioma using anti-CD44 antibody, confirmed that G-26 cells were CD44⁺. Following 3-day treatment with MuIFN α/β at 8×10² or 8×10³ IU/ml of glioma cells, the expression of CD44 was not significantly affected as reflected by CD44⁺ cell number and fluorescence intensity. The pretreatment of glioma cells for 1 day with anti-CD44 antibody resulted in a 30-60% decrease of CD44 expression. This coincided with significantly (p<0.05) lower cell activity as judged by MTT assay for mitochondrial activity. The zymographic evaluation of MMP activity in the G-26 glioma cell culture showed a high level of the active form of MMP-2. This level of MMP-2 was decreased following 3 day treatment of G-26 glioma cells with either 8×10³ or 8×10³ IU/ml of MuIFNα/β but only the latter concentration produced statistically significant 55% decrease. However, following a 1 day treatment of G-26 glioma cells with anti-CD44 antibody, the level of active MMP-2 form was not significantly affected. These findings indicate that while the inhibitory effect of IFN on glioma invasion was accompanied by a decreased level of the active form of MMP-2 released extracellularly, the expression of the transmembrane CD44 adhesion molecule was not affected. Conversely, anti-CD44 antibody pretreatment of G-26 glioma, which led to the inhibition of glioma invasion, resulted in decreased CD44 expression and lower cell activity but had no effect on the MPP-2.