AQP1 and xerostomia: Several treatments have shown beneficial effects against IR-induced xerostomia, such as antioxidants (e.g., amifostine), gene transfer of human aquaporin 1 cDNA (hAQP1) (Baum et al., 2017; Baum et al., 2009; Delporte et al., 1997; Gao et al., 2011; Shan et al., 2005; Vitolo and Baum, 2002), fibroblast growth factor-2 (Guo et al., 2014), or sonic hedgehog (Hu et al., 2018), intraperitoneal injection of the immune inhibitor rapamycin (Zhu et al., 2016), stem cell transplantation, and salivary gland regeneration.