For an exploration of the up-regulated TREM2 in macrophages, we analyzed the single cell RNA sequencing data of human lung adenocarcinoma [35], and identified TREM2-positive macrophages (TREM2+ M) and TREM2-negative macrophages (TREM2− M) (Supplementary Fig. 2A-C). Here, TREM2 is linked to lung adenocarcinoma.