Aquaporin-3 expression profile in malignant mesothelioma

Background & Objectives: Aquaporins regulate water transport in normal and neoplastic cells. They also play a role in cell migration, proliferation and adhesion. Preliminary data have shown AQP-1 upregulation in MM, but other aquaporin such as AQP-3 could present disregulation and be used as potential therapeutic targets: AQP-3 (an aquaglyceroporin expressed in the stratum corneum of the skin) was found to be overexpressed in colorectal, cervical, lung, oesophageal, gastric, skin and tongue (squamous) carcinomas and in hepatocarcinomas. Methods: Supported by preliminary biochemical results, a consecutive series of ten MM samples was evaluated with immunohistochemistry (Sigma Aldrich anti-AQP3 antibody) and AQP-3 expression was compared with adjacent non-neoplastic mesothelium. We evaluated only the positivity or negativity, regardless of the intensity of the staining. Results: Expression of AQP-3 was observed in 7 out of 10 cases, with a membrane (62%) or cytoplasmic (25%) pattern of expression in up to 70% of MM cells, while expression in non-neoplastic mesothelium was not significant. The only case of sarcomatoid malignant mesothelioma in our series was found to be negative for AQP-3. Conclusion: AQP-3 appears to be upregulated in 70% of our series of MMs, with a prevalent expression on the membrane surface, where the protein can play its natural role in water (and glycerol) exchange. The cases where a cytoplasmatic pattern was observed, suggest us that protein can play a pathogenetic role not only if correctly exported to the cellular membrane, but also if accumulated in the cytoplasm.