PTPRK and central nervous system cancer: Based on the facts that 1) PTPs are believed to have tissue-specific functions, 2) EGFR and β-catenin signaling are among the most frequently deregulated oncogenic pathways in glioma and 3) PTPRK is highly expressed in brain, we hypothesized that PTPRK exerts anti-glioma effect by inhibiting EGFR and β-catenin oncogenic signaling.