Fig 2: Correlation between the proportion of tumor-infiltrating immune cells and CD2 expressionNote: (A) Correlation analysis of the expression levels of tumor-infiltrating immune cells and CD2; (B) Correlation of M0 macrophage ratio with CD2 expression; (C) Correlation of M1 macrophage ratio with CD2 expression; (D) Correlation of M2 macrophage ratio with CD2 expression.

Fig 3: Single-gene differential analysis of candidate DEGsNote: (A) Differential expression of CD40LG in BC tissue and normal breast tissue next to cancer; (B) Differential expression of CD52 in BC tissue and normal breast tissue next to cancer; (C) Differential expression of CD2 in BC tissue and normal breast tissue next to cancer; (D) Differential expression of CD3E in BC tissue and normal breast tissue next to cancer; (E) Differential expression of SPN in BC tissue and normal breast tissue next to cancer; (F) Differential expression of CD5 in BC tissue and normal breast tissue next to cancer; (G) Differential expression of CD27 in BC tissue and normal breast tissue next to cancer; (G) Differential expression of CD27 in BC tissue and normal breast tissue next to cancer. (E) Differential expression of SPN in BC and normal breast tissues; (F) Differential expression of CD5 in BC and normal breast tissues next to cancer; (G) Differential expression of CD27 in BC and normal breast tissues next to cancer; (H) Differential expression of CD48 in BC and normal breast tissues next to cancer; (I) Differential expression of ITK in BC and normal breast tissues next to cancer (I) Differential expression of ITK in BC and normal breast tissues; (J) Differential expression of IL-7R in BC and normal breast tissues.

Fig 4: CD2/CD27 could influence M2 polarization of macrophages and participate in breast cancer brain metastasis.Note: (A) IVIS spectral system is used for in vivo bioluminescence imaging to monitor tumor growth; (B) H&E staining is used to observe the morphology of nude mouse tumor tissue (× 200); (C) TUNEL staining is used to detect cell apoptosis in nude mouse tumor tissue (× 200); (D) Ki67 immunohistochemical staining is used to detect Ki67 protein expression in nude mouse tumor tissue (× 200); (E) RT-qPCR is used to detect the expression of CD2 and CD27 mRNA in nude mouse tumor tissue; (F) WB is used to detect the expression of CD2 and CD27 protein in nude mouse tumor tissue; (G) Flow cytometry is used to detect the proportion of macrophages in each group of nude mouse tumor tissue. (H) The Glutamine content in tumor tissues of each group was measured using the Glutamine Assay Kit. * indicates P<0.05 compared with the oe-NC group, with 8 nude mice in each group.

Fig 5: Screening of BC brain metastasis-associated DEGsNote: (A) Heat map of differential expression in the BC brain metastasis dataset; (B) GO and KEGG pathway analysis; (C,D) CD2 and CD27 expression level levels in the brain metastasis group; (E,F) GSEA analysis of the signaling pathways involved in CD2 and CD27.