TENASCIN EXPRESSION IN ASTROCYTOMAS CORRELATES WITH ANGIOGENESIS

We investigated the expression and distribution of the extracellular m atrix protein tenascin (TN) in 59 astrocytomas and 11 samples of norma l brain by Western blot analysis and immunohistochemistry using antibo dies against human TN. The tumors included 14 juvenile pilocytic astro cytomas (grade I), 13 low grade fibrillary astrocytomas (grade II), 8 anaplastic astrocytomas (grade III), and 24 glioblastomas multiforme ( grade IV). Proliferation indices were calculated by computer-based ima ge analysis after immunostaining with the MIB-1 antibody against the K i-67 proliferation-associated antigen. Western blot analysis for TN on fresh frozen tumor tissue from 23 of the 59 astrocytomas indicated up to 4-fold higher TN expression in glioblastomas multiforme than in no ntumorous control tissues. Enhanced intercellular expression of TN was observed by immunohistochemistry in glioblastomas multiforme. Moreove r, TN immunostaining was consistently greater within and around the wa lls of hyperplastic blood vessels than nonhyperplastic vessels of both high grade tumors and juvenile pilocytic astrocytomas. Juvenile piloc ytic astrocytomas with increased TN expression by Western blot analysi s had vascular hyperplasia by light microscopy. proliferation indices moderately correlated with tumor grade. Enhanced immunohistochemical e xpression of TN was associated with higher tumor grade with higher pro liferation indices. The strong association of TN and vascular hyperpla sia, regardless of tumor grade, suggests that TN may play a crucial ro le in angiogenesis.