Adenovirus-mediated gene transfer of dominant negative Ha-Ras inhibits proliferation of primary meningioma cells

OBJECTIVE: Previous studies demonstrated that activation of receptor tyrosine kinases in human meningiomas by an autocrine or paracrine growth-stimulatory loop plays an important role in meningioma proliferation. Although it is well established that the proliferative signal from protein tyrosine kinase receptors is transduced through Pas proteins, the relevance of the Ras pathway in meningioma proliferation, to our knowledge, has not been studied. The purpose of this study was, therefore, to determine whether Pas proteins are functionally important in meningioma proliferation. METHODS: Meningioma cells of nine primary cell cultures were infected with the recombinant adenovirus Ad-rasN17 encoding: the dominant negative Pas protein or control adenovirus Ad-pAC. Ras-N17 is a Pas mutant protein with substitution of asparagine for serine at position 17 in the cellular Ha-Pas protein that inhibits function of all endogenous cellular Pas proteins. Proliferation of meningioma cells was measured using [H-3]thymidine or 5-bromo-2'-deoxyuridine labeling and detection assays. RESULTS: Infection of meningioma cells with Ad-rasN17 dramatically increased the expression levels of the Ras-N17 mutant protein and inhibited phosphorylation of the mitogen-activated protein kinases, compared with uninfected cells or cells infected with the control adenovirus. Suppression of Pas proteins inhibited proliferation of ail exponentially growing and growth-arrested meningioma cells stimulated with serum. CONCLUSION: The obtained results suggest that proliferation of primary meningioma cells is dependent on the presence of functional Pas proteins. Therefore, inhibition of the Pas pathway may be important in preventing growth factor-stimulated meningioma proliferation.