Bcl-2, bcl-x, and bax expression in dysembryoplastic neuroepithelial tumors

Bcl-2, bcl-x and bax are regulatory proteins which are variably expressed in brain tissue and are known to be involved in the regulation of apoptosis; bcl-2 and bcl-x inhibit apoptosis and bax generally promotes apoptosis. This study is a retrospective clinicopathologic and immunohistochemical review of 18 dysembryoplastic neuroepithelial tumors (DNTs), specifically looking for evidence of aberrant expression of apoptosis regulatory proteins which may promote the survival of one or more of the cellular constituents of the tumor.

Eighteen patients (11 males) with DNTs comprise the study group. Patients at the time of surgery ranged in age from 2.1-52 years (mean 16.1 years). Mean seizure duration prior to surgery was 6.4 years (n = 16 patients). Sixteen patients were alive with markedly reduced or no seizures at a mean postsurgical follow-up interval of 63 months; 2 patients were lost to follow-up.

All tumors were characterized by an admixture of oligodendroglial cells, neurons and astrocytic cells, focally arranged against a microcystic background. Coexistent cortical dysplasia was noted in 14 evaluable cases. Mitotic figures were rarely noted in 2 tumors. MIB-labeling indices ranged from 0-0.6 (mean 0.2). Astrocytes which were part of the tumor stained with all three antibodies in all cases. The oligodendroglial-like cells of DNT stained positively for bcl-2 in 2/17 tumors, bcl-x in 10/17 tumors, and bax in 12/17 tumors. The neuronal cell component of the DNT stained positively with bcl-2 in 15/17 tumors, bcl-x in 5/17 tumors, and bax in 8/17 tumors.

Aberrant expression of apoptosis-associated proteins, similar to what has been previously described in gangliogliomas (another epilepsy-related, dysplasia-associated tumor), may play a role in the pathogenesis of DNT.