Brain metastasis is a frequent complication of the progression of malignant melanoma.
In a previous study aquaporin 1 (AQP1) protein expression was found to be associated
with increased mortality and decreased progression free survival in cutaneous melanoma.
To explore further the potential of this marker we studied the AQP1 protein expression
in 67 metastatic melanoma patients using immunohistochemistry. Primary tumor samples
were acquired from patients with brain (BR) (n = 44) and extra-cranial (EC) (n = 23)
metastases, while brain metastatic samples were collected during neurosurgical resection
(n = 5). Patients with brain metastases had shorter overall survival (p = 0.02) and
significantly higher AQP1 expression in the primary tumors (median H-score = 250 vs.
140, p = 0.044) as compared to patients of the EC metastasis group. AQP1 expression
was found to be significantly lower in the brain metastases compared to the corresponding
primary tumors (median H-score = 35 vs. 300 p = 0.01). However, in brain metastases
AQP1 expression was heterogenous, AQP1 protein was more abundant in the melanoma cells
far away from the capillaries as compared to tumor cells adjacent to vessels indicating
a hypoxia-driven expression of AQP1. We suggest that AQP1 expression could well be
a prognostic marker of brain metastatic potential of human cutaneous melanoma.
