Fig. 5: OxLDL induces TREM2 and SPP1 expression via the TREM2/SYK/CEBPα axis in TAMs.

A UMAP projection (upper) and barplot (lower) show Spp1 expression in TAMs from Trem2-wildtype or Trem2-KO tumors, with two-tailed Wilcoxon-test statistics. B Relative SPP1 protein (left, representative of n = 3 biological replicates), mRNA (middle), and supernatant (right) expression in wildtype or Trem2^−/− TAMs treated with oxLDL (50 μg/mL). C Flow cytometry of IFNγ in CD8⁺T cells co-cultured with wildtype or Trem2^−/− TAMs treated with oxLDL. D Transwell migration and evasion assays of Hepa1–6 co-cultured with wildtype or Trem2^−/− TAMs treated with oxLDL. Scale bar, 100 μm. Quantification was performed with n = 5 random fields. E–G Western blot (WB) and flow cytometry of pSYK expression in BMDM or TAM treated with vehicle, LDL (50 μg/mL) or oxLDL (E), in wildtype or Trem2^−/− TAMs treated with oxLDL (F), and in TAMs isolated from wildtype or Trem2^−/− tumors (G). H Protein (left, representative of n = 3 biological replicates) and supernatant (right) expression of SPP1 in TAMs treated with oxLDL ± R406 (5 μM) or Piceatannol (40 μM). I Venn diagram shows the overlapping activated TFs in human and mouse TREM2⁺TAM (left). Regulon ranks of top enriched TFs in human and mouse TREM2⁺TAM (right). J Heatmap summarizing the qPCR results in TAMs treated with vehicle or oxLDL with indicated TF KD (mean of n = 3 biological replicates). K, L WB of CEBPα levels in BMDM or TAM treated with vehicle, LDL or oxLDL (K), in wildtype or Trem2^−/− TAMs treated with oxLDL (L, left), and in TAMs isolated from wildtype or Trem2^−/− tumors (L, right). M ChIP-qPCR assays of CEBPα binding at the Trem2 or Spp1 promoter (n = 3 experimental replicates). N Co-immunoprecipitation assays of DNMT3A and CEBPα interaction in TAMs treated with vehicle or oxLDL. O 5mC levels at the CpG-rich promoter regions of Trem2 and Spp1 were determined by BS-PCR in wildtype or Trem2^−/− TAMs treated with vehicle or oxLDL ± siCebpa. P Schematic of the co-injection experiments. Q Tumor volume of Hepa1-6 cells co-injected with shNC/shCebpa TAMs (n = 6 mice). R, S Flow cytometry of TREM2, SPP1 expression in TAMs (R) and IFNγ expression in tumor-infiltrating CD8⁺T cells (S) (n = 6 mice). T Schematic summarizing the mechanism of oxLDL inducing TREM2 and SPP1 expression in TAMs. WB results shown were representative of three independent experiments in (E–G, K, L, N). Data represent the mean ± SD, n = 3 biological replicates in (B, C, E–H). Statistical significance was determined by the Wilcoxon signed rank test (A) and two-tailed unpaired t test (B–H, M, Q–S). Schematics in P and T were created in BioRender. Chu, T. (2025) https://BioRender.com/r2v4jgs. Source data is provided as a Source Data file.