CCL18 and non-small cell lung carcinoma: We found that MTHFD1 expression gradually increased as monocytes differentiate into macrophages and it was mainly expressed in CCL18+ macrophages (Fig. 6E), and meanwhile CCL18 expression was up-regulated in TCGA-LUAD patients with high-risk (Additional file 3: Fig. S2E), suggesting that MTHFD1 may be implicated in immunosuppressive macrophage differentiation of NSCLC.