EXPRESSION OF CYCLIN D1 PROTOONCOGENE MESSENGER-RNA IN PRIMARY MENINGIOMAS MAY CONTRIBUTE TO TUMORIGENESIS

Meningiomas are benign brain tumors thought to arise by multi-step tum origenesis, involving both the activation of oncogenes and the loss of tumor suppressor genes. The cell cycle regulator proto-oncogene cycli n D1 has been implicated in the pathogenesis of several types of cance r. Northern blot analysis revealed expression of cyclin D1 mRNA in 8 ( 53%), and cyclin B mRNA in 12 of 14 (86%), primary meningiomas. Immuno cytochemistry using an antibody specific for cyclin D1 showed strong p ositivity amongst meningeal cells in the same meningioma samples. No c yclin D1 mRNA was detected in a sample of normal pachymeninges. Cyclin B, which has not yet been linked to tumorigenesis and serves as a mar ker for cellular proliferation, was expressed in a higher proportion o f meningioma samples. These data provide the first evidence for the ov erexpression of cyclin D1 and B mRNA and protein in primary human meni ngiomas, and are consistent with a proposed oncogenic role of cyclin D 1 in tumorigenesis. Excessive levels of the cyclin D1 proto-oncogene m ay lead to deregulation of G1 control in a proportion of arachnoid cap cells leading to tumorigenesis.