SPP1 and esophageal squamous cell carcinoma: Single cell transcriptomics and spatial transcriptomics studies also identified other genes in this subpopulations in different tumors such as TREM2 and FN1 in breast cancer (31–33); MARCO and VEGFA in colorectal cancer (CRC) (34, 35); ENO1, LDHA, ALDOA, and TPI1 in non-small cell lung cancer (NSCLC); APOE in pancreatic ductal adenocarcinoma (PDAC) (36); metalloproteinases (MMP9, MMP12, and MMP7) in hepatocellular carcinoma (37); TREM2, C1QC, C1QB, C1QA, SPP1, and APOE in esophageal squamous cell carcinoma (38) (Figure 1).