Differential expression of somatostatin receptors in ependymoma: Implications for diagnosis

Somatostatin receptors (SSts) have been found in a variety of brain tumors, e.g., meningiomas, medulloblastomas and astrocytomas, Our aim was to inves tigate their expression in ependymomas, Using RT-PCR, expression of mRNA fo r the different SSt subtypes was analyzed and quantified in 28 ependymomas and correlated with different variables (age, tumor location, histological grade, recurrence and survival). In addition, in 8 cases, protein expressio n was studied in vitro, using immunohistochemistry, and in vivo, by somatos tatin scintigraphy, mRNAs for all 5 subtypes were variably expressed in eac h ependymoma. The Southern blotting signal obtained after SSt(1) and SSt(2) amplification was higher than that for the other receptor subtypes, No sig nificant correlation was seen between the level of SSt(1) and SSt(2) mRNA e xpression and age, location, histological grading, recurrence or survival. In the 8 cases, SSt(1) staining was negative in 3 and low in 5, Staining fo r SSt(2A) was positive but low in every specimen analyzed. SSt(1) and SSt(2 ) immunoreactivity was seen only in the cytoplasm of tumoral cells. Somatos tatin scintigraphy showed clear uptake, which agreed with MRI data in the m ajority of cases, However, no correlation was seen between tracer uptake in tensity and histological grade, SSt(1) and SSt(2) mRNA expression or immuno staining intensity. This evidence for the expression of SSt(2) receptors in ependymomas opens interesting prospects for their follow-up, (C) 2001 Wile y-Liss, Inc.