CD44 expression in primary and recurrent oligodendrogliomas and in adjacent gliotic brain tissue

CD44 expression was evaluated in 114 primary and recurrent oligodendrogliomas (46 primary oligodendrogliomas grade II and 15 recurrences grade II; 17 primary anaplastic oligodendrogliomas and nine recurrent oligodendrogliomas grade III; 14 glioblastomas with oligodendroglial growth pattern and 13 tumour recurrences grade IV). CD44 expression was found to correlate with tumour grading (P<0.001) and with survival (Kaplan-Meier Log Rank P<0.01, median survival 28 months in oligodendrogliomas with CD44 expression vs. 108 months in CD44-negative tumours). However, multivariate Cox regression analysis of grading and CD44 expression revealed that CD44 expression had no prognostic relevance independent of histological grading. Characterization of CD44 positive cells by double labelling with GFAP revealed that in addition to oligodendroglioma cells, reactive astrocytes within the tumour, at the invasive margin and along the pathways of oligodendroglioma invasion in the subpial matrix, and in the vicinity of vessels, frequently expressed CD44. It is suggested that in analogy to carcinoma invasion where a tumour-induced production of hyaluronan was found in fibroblasts at the invasive margin of the tumour, in the brain reactive astrocytes may produce hyaluronan which would facilitate the adhesion of new CD44-positive astrocytic processes but which would also promote tumour invasion.