Overexpression of cyclin D1 in meningioma is associated with malignancy grade and causes abnormalities in apoptosis, invasion and cell cycle progression

Cyclin D1 has been reported overexpressed in many malignant cancers. However, the expression pattern and biological function of cyclin D1 in meningiomas are still unknown. In this study, we examined the expression of cyclin D1 in meningioma with immunohistochemistry and correlated the measure to the recurrence. Potential effects of cyclin D1 on tumor growth and apoptosis were also examined in representative cell lines (IOMM-Lee and CH157) by inhibiting cyclin D1 with RNA interference. We demonstrate that cyclin D1 mRNA and protein expression are positively correlated with meningioma grade and that higher cyclin D1 expression correlates with higher recurrence. Knockdown of cyclin D1 by the siRNA decreased IOMM-Lee and CH157 cell proliferation, promoted the rate of apoptosis and attenuated invasive capacity. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blot analysis revealed that cells stably underexpressing cyclin D1 showed lower expression of survivin and the antiapoptotic protein B cell lymphoma-2 (Bcl-2) compared to control cells. These results indicate that high cyclin D1 expression is associated with a poor outcome of meningioma patients and knockdown of cyclin D1 expression may be a potential treatment for malignant meningioma.