Epidermal growth factor receptor and caveolin-1 coexpression identifies adult supratentorial ependymomas with rapid unfavorable outcomes.

Supratentorial ependymomas account for a minority of intracranial ependymomas, which still have uncertain prognostic markers. Among them, epidermal growth factor receptor (EGFR) overexpression correlates with a poor prognosis. In glioblastoma cells, EGFR function has been reported to be regulated by its migration from cell membrane infoldings called caveolae and by its colocalization with the caveolae-associated protein caveolin-1 (cav-1). Therefore, we decided to investigate cav-1 expression and coexpression with EGFR in a series of adult intracranial ependymomas. We analyzed 22 adult supratentorial ependymomas and compared tumor grades as determined by the WHO classification and patient survival rates with the expression of EGFR, cav-1, and p53 and the values of the proliferation marker Ki-67, all tested by immunohistochemistry; in addition, we investigated the mutational profile of cav-1. The results demonstrate that the tumor grade is directly correlated with EGFR, Ki-67, and cav-1 expression only, whereas (by univariate analysis) the expression of all the studied markers, as well as the tumor histological grade, significantly correlated with the patient's overall survival (OS). By multivariate analysis using the Cox proportional hazards model, among all variables considered, cav-1 was the only independent prognostic marker related to OS (relative risk = 13.92; P = .013). Among grade II ependymomas, only cav-1 correlated with poor OS (P = .011), distinguishing 2 distinct subgroups of tumors with different outcomes despite sharing identical grading. All the patients studied carried wild-type cav-1 sequences, demonstrating that cav-1 overexpression is not driven by activating mutations, as previously reported in other tumor types. Interestingly, after stratifying all cases into 4 distinct groups according to cav-1 and EGFR expression (cav-1+/EGFR+, cav-1-/EGFR-, cav-1+/EGFR-, and cav-1-/EGFR+), the coexpression of cav-1 and EGFR identified a subset of patients with definitively poor prognoses. Further studies are needed to support this evidence on a larger scale and to clarify how cav-1 and EGFR interaction can influence tumor aggressiveness.