Overexpression of Sema3E and Sema5A in pilocytic astrocytoma

Abstract

We have previously found that Sema5A, a member of the semaphorin gene family, is up-regulated in pediatric pilocytic astrocytomas (PA) at the mRNA level by microarray analysis and real-time RT-PCR. By further analysis of the expression level of all 17 semaphorin genes in the microarray dataset, we found that Sema5A and Sema3E are the only two semaphorin genes that are highly up-regulated in pilocytic astrocytomas.  In this study, the up-regulation of Sema3E was further confirmed by real-time RT-PCR. Furthermore, the over-expression of both SEMA3E and SEMA5A proteins were also confirmed by Western blot analysis and immunohistochemistry.  Since pilocytic astrocytoma is characterized by extensive vasculature, co-immunofluorescent staining of both CD31 and SEMA3E (or SEMA5A) was performed. The result showed that a higher expression of SEMA3E was around the CD31 positive endothelial cells. Based on semaphorin’s function in angiogenesis and a higher expression of SEMA3E and SEMA5A around endothelial cells in these PA samples, these genes could be potential biological markers and anti-angiogenesis therapeutic targets for pilocytic astrocytomas.