CHI3L1 and cancer: Subcluster 3 was characterized by CHI3L1 (a chitinase-like protein with broad-ranging activity in inflammation, tissue repair and macrophage polarization41; Fig. 6b,f), NUPR1 (strongly expressed by basophils and neutrophils), FBP1 (fructose-1,6-bisphosphatase 1, a marker of human M1 polarization42) and MT1G (metallothionein 1G, associated with cancer-associated TREMhi macrophages43 and a pleiotropic regulator of myeloid cell function44).