GLS and plasma cell myeloma: This strategy has already shown success in numerous cancers; for example, inhibition of amino acid recycling sensitized neuroblastomas to cisplatin (Gunda et al., 2020), fueling histidine catabolism via histidine supplementation increases sensitivity of leukemic xenografts to methotrexate (Kanarek et al., 2018), and the glutaminase inhibitor CB-839 synergistically enhances the cytotoxicity of carfilzomib in treatment-resistant multiple myeloma cells, notably through its inhibition of glutamine-fueled mitochondrial respiration (Thompson et al., 2017).