AQP1 and cholangiocarcinoma: In human astrocytomas, the expression levels of AQP1, 4, and 9 are largely increased (Saadoun et al., 2002a,b; Nico et al., 2009; El Hindy et al., 2013; Jelen et al., 2013), while the level of AQP1 was shown to be either increased (Mazal et al., 2005) or decreased (Aishima et al., 2007) in cholangiocarcinoma.