S100A9 and malignant colon neoplasm: To gain insight into the mechanisms through which GM‐Exo promote colon cancer cell stemness and subsequent tumor progression, we mined MDSC exosomes mass spectrometry data for potential stemness mediators.18 The pro‐inflammatory protein S100A9 was previously shown to be abundant in MDSC‐ derived exosomes and to have a chemotactic function for MDSCs.18, 24 As shown in Figure3A, abundant S100A9 protein was detected in GM‐Exo.