AQP1, AQP4 and AQP9 are expressed in brain tumours, and AQP4 expression increases with the severity of brain oedema (Saadoun et al., 2002a; Ding et al., 2010; Wang and Owler, 2011; Ding et al., 2013; Maugeri et al., 2016; Lan et al., 2017). The gene discussed is AQP4; the disease is brain neoplasm.