GLS and cancer: The GAC isoform is more frequently upregulated in cancer cells than KGA (Wang et al., 2010), and has been shown to be regulated by MYC (Gao et al., 2009; Wise et al., 2008; Yuneva et al., 2007), leading to a ‘glutamine addiction’ phenotype in MYC-driven tumors (Wise and Thompson, 2010).