Abstract
The cyclin-dependent kinase (CDK) inhibitor p16(INK4a) and the MDM2 ubiquitin ligase inhibitor p19(ARF) are critical to the regulation of cell cycle progression. Their loss by deletion, mutation or epigenetic silencing is a common molecular alteration in many human cancers. To investigate the role of p16(INK4a)/p19(ARF) deficiency in CNS tumor pathogenesis, pregnant mice bearing p16(-/-)/p19(-/-), p16(+/-)/p19(+/-), and p16(+/+)/p19(+/+) embryos were exposed transplacentally on gestation day 14 to a single dose of the potent carcinogen, ethylnitrosourea (ENU). p16(+/-)/p19(+/-) male mice treated with ENU developed meningial proliferative lesions with a high incidence (5/10). The incidence was lower in other ENU-treated animals of both sexes and none occurred in saline-treated control animals. The lesions ranged from widespread meningeal proliferation and plaque-like thickening by neoplastic spindle cells consistent with meningiomatosis to a larger discrete mass consistent with a meningioma. Ultrastructural analysis revealed the presence of intercellular junctions between cells, supporting a meningothelial histogenesis. Spontaneous meningiomas occur rarely in wild-type mice but are a common neoplasm afflicting humans, accounting for between 13 and 26% of primary intracranial neoplasms. This ENU inducible meningeal lesion in p16(+/-)/p19(+/-) mice may provide additional insight into the pathogenesis of meningeal neoplasia and aid the development of therapeutics.