AQP1 and neoplasm: Several studies support a role for AQP1 in tumour progression: AQP1-null mice showed reduced tumour growth, metastasis and angiogenesis compared to AQP1-expressing mice [18,19]; mammary gland tumour cells transfected with AQP1 showed increased migration in vitro and increased tumour cell extravasation and lung metastases in vivo [20]; and in vitro inhibition of AQP1 reduced endothelial cell tube formation and the migration, invasion, and growth of colorectal cancer cell lines [12,13,14,21,22].