PROP1 and CTNNB1 expression in adamantinomatous craniopharyngiomas with or without β-catenin mutations

INTRODUCTION: Activating mutations in exon 3 of the beta-catenin gene are involved in the pathogenesis of adamantinomatous craniopharyngiomas. Recently, the interaction between beta-catenin and PROP1 has been shown to be responsible for pituitary cell lineage determination. We hypothesized that dysregulated PROP1 expression could also be involved in the pathogenesis of craniopharyngiomas. OBJECTIVES: To determine whether dysregulated gene expression was responsible for tumor pathogenesis in adamantinomatous craniopharyngiomas, the beta-catenin gene was screened for mutations, and the expression of the beta-catenin gene and PROP1 was evaluated. METHODS: The beta-catenin gene was amplified and sequenced from 14 samples of adamantinomatous craniopharyngiomas. PROP1 and beta-catenin gene expression was assessed by real-time RT-PCR from 12 samples, and beta-catenin immunohistochemistry was performed on 11 samples. RESULTS: Mutations in the beta-catenin gene were identified in 64% of the adamantinomatous craniopharyngiomas samples. Evidence of beta-catenin gene overexpression was found in 71% of the tumors with beta-catenin mutations and in 40% of the tumors without mutations, and beta-catenin immunohistochemistry revealed a nuclear staining pattern for each of the analyzed samples. PROP1 expression was undetectable in all of the tumor samples. CONCLUSION: We found evidence of beta-catenin gene overexpression in the majority of adamantinomatous craniopharyngiomas, and we also detected a nuclear beta-catenin staining pattern regardless of the presence of a beta-catenin gene mutation. These results suggest that WNT signaling activation plays an important role in the pathogenesis of adamantinomatous craniopharyngiomas. Additionally, this study was the first to evaluate PROP1 expression in adamantinomatous craniopharyngiomas, and the absence of PROP1 expression indicates that this gene is not involved in the pathogenesis of this tumor, at least in this cohort.