GLS and cancer: SLC1A5, also known as ASCT2 (for alanine, serine, cysteine transporter 2), is a neutral amino acid transporter that is localized in the plasma membrane.67,68 Glutamine is the preferred substrate for SLC1A5.68,69 SLC1A5 is being actively investigated as a pharmacological target in cancer.68 The protein is expressed in lung, skeletal muscle, large intestine, kidney, testis, T-cells, brain, and adipose tissue, but it is significantly upregulated in cancers.69 GLS is an amidohydrolase enzyme that generates glutamate from glutamine.63 There are four known isoforms of GLS.