Plasma MPs and tumor growth in Par4 KO mice. (A) Plasma MPs from WT and Par4 KO mice were analyzed by nanoparticle tracking, and are shown ± SEM (n = 6); P < .03. (B) A total of 1 × 10⁶ LLC cells were seeded in the flanks of WT and Par4 KO mice, and tumor volumes were measured 8 days after seeding, shown ± SEM (n = 6); P < .03. (C) LLC tumors were seeded as in panel B, and 1 × 10¹⁰ freshly isolated PMPs were transfused in the tail vein every 24 hours beginning at day 8 as indicated. Tumor volumes were measured daily, and are shown ± SEM (n = 6); *P < .03; **P < .002. (D) Tumors from panel C were resected, fixed, and processed for IHC with antibodies to murine CD41 (α_IIb integrin, red) to label endogenous PMPs, and cleaved caspase-3 (green); DAPI stain is shown in blue. (E) Tumor sections from panel C stained with antibodies to human CD41 (α_IIb integrin, red) to label transfused PMPs, cleaved caspase-3 (cl. cas-3, green), and DAPI (blue). Bars, 15 μm.