Loss of endothelial Gα _s reduced primary tumor growth. (a–c) B16-F10 (a and b) or LLC1 (c) tumor cells were injected subcutaneously in control and EC-Gα_s-KO mice, and tumor growth was determined (n = 9 mice; a and c). B16-F10 tumor sections were analyzed for markers of endothelial cells (PECAM1; green), perivascular cells (α-SMA; red) or for proliferating cells (Ki67; red), and were stained with DAPI (blue). The bar diagrams (b) show the statistical evaluation (n = 6 mice per group). (d and e) Control or EC-Gα_s-KO mice crossed with MMTV-PyMT mice were monitored for occurrence of tumors as well as for the time point at which they had reached the endpoint of the experiment (d), and tumor sections were analyzed by immunohistochemistry (e) using antibodies recognizing endothelial cells (PECAM1; green), perivascular cells (α-SMA; red) and proliferating cells (Ki67; red), and were stained with DAPI (blue). The bar diagrams (e) show the statistical evaluation (n = 6 mice for each genotype). Bar length (b and e): 50 μm. Data represent mean values ± SEM; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001 (two-way ANOVA and Bonferroni’s post hoc test [a and c], two-tailed Student’s t test [b and e], and Gehan-Breslow-Wilcoxon test [d]).