Platelets contain proangiogenic and BMDC mobilization factors. NOD/SCID mice were injected subcutaneously with human LNCaP-C4–2 cells. After 28 days of tumor growth, platelets were isolated from the whole blood of control (white columns) and tumor-bearing (black columns) mice and lysed. A species-specific array for human proteins was used to determine the concentrations of tumor-derived cytokines, represented as mean values ± SEM (n = 4). (A) Tumor-derived thrombopoietin (TPO), interleukin-6, (IL-6), stromal-derived factor 1a (SDF-1a), and vascular endothelial growth factor (VEGF) are highly concentrated in platelets. (B) Tumor-derived granulocyte cololny-stimulating factor (G-CSF), monocyte colony-stimulating factor (M-CSF), matrixmetalloproteinase-9 (MMP-9), and granulocyte-macrophage colony-stimulating factor (GM-CSF) are present at lower levels in platelets. No tumor-derived proteins were found in the platelets of control mice, demonstrating the specificity of the array. *P < .05 vs control (Student t test). ***P < .005 vs control (Student t test).