Investigating the Protein Signature of Adamantinomatous Craniopharyngioma Pediatric Brain Tumor Tissue: Towards the Comprehension of Its Aggressive Behavior

Although histologically benign, adamantinomatous craniopharyngioma (AC) pediatric brain tumor is a locally aggressive disease that frequently determines symptoms and hormonal dysfunctions related to the mass effect on the surrounding structures. Another typical feature of this benign neoplasm is the presence of voluminous liquid cysts frequently associated with the solid component. Even if studies have been devoted to the proteomic characterization of the tumor intracystic fluid, poor explorations have been performed on its solid part, principally investigated by transcriptomics technologies. In the present study, seven specimens of AC whole tumor tissue have been analyzed by LC-MS for a preliminary assessment of the proteomic profile by a top-down/bottom-up integrated approach. Thymosin beta 4, ubiquitin, calmodulin, S100 proteins, prothymosin alpha isoform 2, alpha-defensins 1-4, and fragments largely belonging to vimentin, hemoglobin, and glial fibrillary acidic protein characterized the intact proteome. The identification of alpha-defensins, formerly characterized in AC intracystic fluid, reinforces the hypothesis of a role for inflammation in tumor pathogenesis. A total number of 1798 unique elements were identified by a bottom-up approach with a special focus on the 433 proteins commonly characterized in the 85.7% of the samples analyzed. Their gene ontology classification evidenced the involvement of the adherence system, intermediate filaments, and actin cytoskeleton in tumor pathogenesis and of elements part of the Wnt, FGF, and EGFR signaling pathways. In addition, proteins involved in calcium modulation, innate immunity, inflammation, CCKR and integrin signaling, and gonadotropin-releasing hormone receptor pathways were also outlined. Further than confirming proteomic data previously obtained on AC intracystic fluid, these results offer a preliminary overview of the AC whole tissue protein phenotype, adding new hints towards the comprehension of this still obscure pediatric brain tumor.