EXPRESSION OF CD44 SPLICE VARIANTS IN HUMAN PRIMARY BRAIN-TUMORS

Expression of CD44, particularly of certain splice variants, has been linked to tumor progression and metastatic potential in a number of di fferent animal and human cancers. Although differential expression of CD44 standard epitopes (CD44s) in human brain tumors has been reported , the expression of CD44 variant exon encoded sequences (CD44v) in pri mary brain tumors in situ has not been studied in detail. In the prese nt study, the expression of CD44s and CD44v epitopes was analyzed immu nohistochemically on frozen sections of primary brain tumors. In addit ion, the expression of CD44 on cultured glioma cells was investigated by immunofluorescence flow cytometry. The results demonstrate the pres ence of CD44s epitopes and of CD44 splice variants containing CD44v4, v5 and v10 sequences in various types of brain tumors. A subgroup of h ighly malignant gliomas showed a strong (focal) expression of CD44v5. CD44v6 was absent in all brain tumors examined. CD44s appeared to be t he dominant form of CD44 expressed in primary brain tumors, its expres sion was not correlated with tumor grade. We envisage that CD44 isofor ms, in particular CD44s, may contribute to the invasive character of p rimary tumors by interacting with hyaluronate, one of the most abundan t molecules in the extracellular matrix of the brain.