Gene expression of insulin-like growth factor II in human intracranial meningioma

Abstract

Insulin-like growth factor II (IGF-II) is synthesized in the normal brain of adult humans predominantly in the choroid plexus and meninges and is secreted in the cerebrospinal fluid. The authors measured IGF-II transcripts and peptides in biopsy specimens from human intracranial tumors including astrocytomas, glioblastomas, and meningiomas. The presence of IGF-II mRNA was analyzed in 12 human brain tumors by Northern analysis of total RNA extracted from tumor biopsies and by in situ hybridization of tissue sections. The amount of immunoreactive IGF-II was determined by radioimmunoassay of tumor extracts. Northern analysis of RNA from four meningiomas showed IGF-II mRNA of 6.0, 4.8, and 2.2 kb, and in situ hybridization revealed that meningioma tumor cells contained IGF-II mRNA. In contrast, biopsy specimens from four astrocytomas, one oligoastrocytoma, and four glioblastomas showed no IGF-II mRNA. Radioimmunoassay of IGF-II in tumor extracts showed that all tumors contained IGF-II (40-160 ng/g tissue). Two meningiomas contained the highest amounts of IGF-II (144 and 160 ng/g tissue). IGF-II mRNA is present in higher amounts in benign meningiomas than in malignant glioblastomas and astrocytomas, whereas the content of immunoreactive IGF-II is similar. On the basis of these findings, the authors believe that IGF-II may be involved in growth regulation of meningiomas.