GLUL and neoplasm: Gln metabolism is fundamental also for tumor‐associated macrophage (TAM) function, as macrophage‐specific targeting of glutamine synthetase (GS) in tumor‐bearing mice skews TAMs and MAMs (namely metastasis‐associated macrophages) toward an “M1‐like” state, promoting tumor vessel pruning, vascular normalization, accumulation of cytotoxic T cells, and metastasis inhibition (Palmieri et al, 2017; Menga et al, 2020).