Fig. 2: Spatial Proximity Analysis Uncovers Distinct Cell-Cell Interactions in Black American (BA) and White American (WA) Triple Negative Breast Cancer (TNBC) Using Imaging Mass Cytometry (IMC).

a Landscape of cell-cell interactions in BA (left) and WA (right) TNBC, based on pairwise interactions between the 20 cell clusters defined in Fig. 1d. Race-specific interactions were identified using a linear mixed model, where the interaction score is modeled as score ~ race + patient, with race as a fixed effect and patient as a random effect. Coefficients for the BA (left) and WA (right) terms are shown, with positive coefficients indicating enriched interactions and negative coefficients indicating depleted interactions. Significant BA-specific interactions are highlighted with red boxes, while significant WA-specific interactions are highlighted with blue boxes. b Top six spatially resolved cell-cell interactions in BA TNBC (blue bars) compared to WA TNBC (red bars), with significance determined by -log10 P values (green bars). P-values are derived from 1-sided F-test, adjusted for multiple comparisons. BA TNBC tumors are characterized by Endothelial-Macrophage-Mesenchymal (Endo-Mac-Vim) interactions. Error bars represent the 95% confidence interval (CI) derived from 100 leave-2-patient-out subsampling. c Same as panel (b) but showing the top five spatially resolved cell-cell interactions in WA TNBC (red bars) compared to BA TNBC (blue bars), with significance computed by -log10 P-values (green bars). P-values are derived from 1-sided F-test, adjusted for multiple comparisons. WA TNBC tumors are marked by immune exhaustion-related interactions. Error bars represent the 95% CI derived from 100 leave-2-patient-out subsampling. d Spatial illustration of key BA-associated cell-cell interactions identified by IMC, showing co- localization of Endothelial (black) and Macrophage (orange) clusters in BA patients. e Spatial illustration of key WA-associated cell-cell interactions identified by IMC, highlighting the prominent interactions between Cytotoxic cells (orange) and Exhausted T cells (pink) in WA tumors, suggesting immune exhaustion. f Multiplex immunofluorescence validation of Endothelial (CD31)-Macrophage (CD163) interactions in BA TNBC, but not in WA TNBC. Representative images from three BA and three WA TNBC patients are shown. Magnified images (from the large white box) of areas marked by small white boxes are included as insets. Scale Bar: 40 um. g, h Pixel-level co-localization quantification of Endothelial-Macrophage interaction, shown in panel (f), across the entire tumor tissue (g) and per cell within the tumor (h) in BA and WA TNBC. In each boxplot, N = 40 images were used for the BA group (27 patients) and N = 63 images were used for the WA group (44 patients). P-values for panels (g) and (h) were calculated using the Mann-Whitney test. Box plots represent the median (center line), interquartile range (25–75%; bounds of the box), and whiskers extending to the 1.5 IQRs. Points that fall outside this range are displayed independently. All data points are used; no outlier exclusion was applied. Source data are provided as a Source Data file.