The role of inflammation in the genesis of the cystic component of craniopharyngiomas.

Craniopharyngioma accounts for 5-10% of childhood tumors and, despite of the benign histological features, its clinical course can be malignant because of critical anatomical relationships with neural and vascular structures and the possible morbidity associated to resection. Only a few studies have addressed the molecular characterization of the cyst fluid so far and the mechanisms of action of intracystic agents are not clearly understood yet. The acidic soluble proteins contained in the cystic fluid of six patients with cystic craniopharyngioma, three of them treated with intratumoral interferon-alpha, were analyzed. A high performance liquid chromatography electrospray ionization mass spectrometry analysis was performed. The antimicrobial peptides alpha-defensins 1-3 relevant for innate immunity were detected in the cystic fluid before the intratumoral treatment. Amount of peptides significantly decreased in cystic fluid during pharmacological treatment. Detection of alpha-defensins 1-3 excludes that cyst fluid formation can derive from disruption of blood-brain barrier and suggests the involvement of innate immune response in pathology of craniopharyngioma cyst formation. The reduction of alpha-defensins could derive both from direct antitumoral effect of interferon-alpha on squamous epithelial cells of craniopharyngioma cyst and from its immuno-modulatory effects on the recruitment of cells of innate immune systems. Interestingly, the clinical patient outcome well correlates with the gradual reduction of alpha-defensins 1-3 amount. Additional studies will be necessary to establish the role of these molecules in the pathogenesis of craniopharyngioma, and further investigations will be necessary to confirm the efficacy of the antitumoral activity of interferon-alpha.