Aquaporin 1 protein expression is associated with BRAF V600 mutation and adverse prognosis in cutaneous melanoma

Despite experimental findings suggesting the prognostic significance of Aquaporin 1 (AQP1) in human melanoma, no published clinical data are available. We studied the expression of AQP1 protein in cutaneous melanoma, correlated our findings with standard histological and genetic markers, and long-term clinical follow-up. Our study evaluated the AQP1 protein expression in 78 melanoma patients, representing two predefined risk cohorts using the immune labeling technique with commercially available anti-AQP1 antibodies on routinely formalin-fixed and paraffin-embedded tumor tissue samples. BRAF V600E mutation analyses were carried out successfully in 70 patients using PCR and restriction fragment length polymorphism analyses, followed by confirmatory analysis with the Sanger sequencing technique. AQP1-expressing melanoma cells were found in 52 cases (66.7%, median H-score=124.24). Significantly higher AQP1 H-scores (P=0.047) were found in the 'high-risk' patients. No correlations were found with the established histological markers, such as mitotic index (P=0.42), Clark level (P=0.95), and Breslow thickness (P=0.51). BRAF V600 mutation analyses were successful in 89%, and showed a two times higher mutation frequency in the 'high-risk' group. The BRAF V600 mutations were significantly associated with AQP1 expression (P=0.014). Long-term follow-up indicated a reduced progression-free survival (P=0.036) and overall survival (P=0.017) for the AQP1-positive cutaneous melanoma patients. AQP1 expression is likely to be associated with an adverse prognosis in cutaneous melanoma.