SPP1 and pulmonary fibrosis: A previous study indicated that Mφ were further divided into three major groups, namely FABP4hi, SPP1hi, and FCN1hi, and played diverse roles in fibrotic lower lobes in idiopathic pulmonary fibrosis (IPF).45 Here, to extensively investigate the heterogeneity of Mφ between the two NSCLC subtypes, 11,016 Mφ were reclustered into four discrete subpopulations based on signature genes, which were defined as FABP4, FCN1, SPP1, and SELENOP-Mφ (Fig. 5a–c).