TSP-1 expression in platelets is an indicator of tumor growth and regression. (A) Western blot analysis of TSP-1 expression in equivalent numbers of platelets harvested from wild-type and Tsp-1^−/− mice immediately after inoculation (No tumor) with Lewis lung cells that express TSP-1 and in mice with tumor volumes of 500 mm³. β-Actin was probed as a loading control. (B) Immunofluorescence analysis of TSP-1 (red) and VEGF (green) expression in platelets harvested from wild-type mice before tumor growth (0) and after tumors reached 500 mm³ (500). Platelets were immunostained with secondary antibody alone to ensure specificity (data not shown). Bar represents 2 μm. (C) Western blot analysis of TSP-1 expression in platelets isolated from an inducible tumor model, LSL-K-ras^G12D x p53^fl/fl mice, after Adeno-Cre-induced sarcoma formation in the extremities. β-Actin was probed as a loading control. Right: Images of LSL-K-ras^G12D x p53^fl/fl mice that were mock infected (uninfected) and 10 weeks after Adeno-Cre infection. Red circles represent sarcomas. (D) Platelet TSP-1 expression by Western blot is probed during tumor growth and after tumor resection on the indicated days. β-Actin was probed as a loading control. Right: Quantification of TSP-1 expression relative to β-actin.