Patterns of expression of Rb and p16 in astrocytic gliomas, and correlation with survival

The retinoblastoma pathway is a key cell cycle regulatory complex that cont rols the passage of cells through the G1 checkpoint and is a frequent targe t of genetic alterations in gliomas. In this study, we examined the express ion of Rb and p16 in 170 primary astrocytic gliomas by immunohistochemical techniques, and correlated the expression with overall survival to determin e their prognostic value as immunomarkers. There were 130 patients with gli oblastoma multiforme (GBM) and 40 with anaplastic astrocytoma (AA). Alterat ions in the levels of Rb or p16 expression were seen in the majority (>90%) of the gliomas studied. The expression of Rb was completely absent or low in 47.5% of the GEM and 67.5% of the AA. The remainder of the tumors was im munopositive for Rb to varying degrees. Immunoreactivity for p16 was absent in 56% of the GEM and 77.5% of the AA. Kaplan-Meier survival plots (log-ra nk test) and Cox proportional hazards regression analysis, adjusted for age and histology, showed that neither Rb nor p16 expression independently pre dicted survival. The results of our study suggest that although genetic alt erations of Rb and p16 are common in gliomas, immunohistochemical analysis of these markers correlates poorly with prognosis.