SLC1A5 and cancer: The Na+ gradient is used to import glutamine and other amino acids into cancer cells via SLC1a5/ASCT2 (Fig. 2), which is upregulated and highly active in many cancer types (Dolinska et al., 2003; Hassanein et al., 2013; van Geldermalsen et al., 2016; Witte et al., 2002).