Analysis of PTPRZ expression in glioma and schwannoma — PTPRZ-long is highly expressed and shed in glioma —

Protein tyrosine phosphatase receptor type Z (PTPRZ) is a central nervous system-specific receptor that shows enhanced expression in gliomas. Our earlier work identified a soluble, proteolytically released form of this molecule (sPTPRZ) in cerebrospinal fluid (CSF), which appeared markedly increased in glioma cases relative to non-tumor controls, implying possible diagnostic value. The expression landscape of PTPRZ across other primary brain tumors, such as schwannomas or meningiomas, has not been systematically clarified. Here, transcriptome profiling of 443 surgically resected brain tumor samples revealed the strongest PTPRZ expression in gliomas, with schwannomas showing the second-highest levels. Because alternative mRNA splicing generates PTPRZ-long and PTPRZ-short isoforms, we performed qPCR analysis to analyze each isoform. qPCR revealed co-expression of the long and short isoforms of PTPRZ in glioma tissues, while schwannomas exclusively expressed the short isoform, lacking detectable PTPRZ-long transcripts. Applying a newly established sandwich ELISA designed to detect the long isoform-derived soluble PTPRZ (sPTPRZ-long), together with immunoblotting using multiple antibodies, we verified the absence of sPTPRZ-long in schwannoma CSF samples. These findings emphasize that PTPRZ-long expression and shedding into CSF are glioma-specific events, supporting its potential use as a molecular biomarker for glioma diagnosis.