FIGURE 4 from Epithelial Expressed B7-H4 Drives Differential Immunotherapy Response in Murine and Human Breast Cancer

Overexpression of B7-H4 in the EMT6 murine model induced resistance to anti-PD-L1 ICI. A, EMT6 cells were virally transduced with the pBabe-B7-H4 retroviral vector and overexpress exogenous murine B7-H4. B, EMT6 B7-H4+ tumors maintain high B7-H4 expression in vivo assessed by IHC. C, Animals were orthotopically injected with EMT6 cells ± B7-H4 and treated 1x per week with anti-PD-L1 at 200 µg (first dose) or 100 µg (subsequent doses) for 4 weeks, after tumors reached 100 mm³. D, EMT6-B7-H4⁺ tumors are significantly resistant to anti-PD-L1 immunotherapy compared with control tumors. Data were analyzed by one-way ANOVA of individual AUC values with Tukey post hoc test for multiple comparisons between EMT6 anti-PD-L1 and EMT6-B7-H4⁺ anti-PD-L1–treated groups (P = 0.0174, EMT6 Isotype n = 21, EMT6 anti-PD-L1 n = 23, EMT6-B7-H4⁺ Isotype n = 21, EMT6-B7-H4⁺ anti-PD-L1 n = 23. Data were collected from a total of three independent experiments). E and F, When tumor response is categorized into three groups, EMT6-B7-H4⁺ tumors have overall greater intrinsic resistance to treatment and reduced complete response compared with EMT6 control tumors (P = 0.035, χ² = 6.683, df = 2, n = 23 mice for EMT6 parental tumors and n = 31 mice for B7-H4 tumors). G, EMT6-B7-H4⁺ tumors were stained by mIF. B7-H4 is expressed on CD45⁻ tumor cells in vivo. Representative image shown. Scale bar 10 µm. H, Quantification of G, n = 3 mice. Data analyzed by unpaired t test. Data were analyzed in GraphPad Prism v10.