Fig. 4

Podoplanin expression facilitates melanoma tumour cell arrest in the lung through its interaction with platelets in vivo. CellTracker-labelled mixed PDPN+ (red) and PDPN- (green) B16-F0 cells were injected intravenously into WT mice. Mice were sacrificed at different time points (30 min, 2 h, 6 h), and the lungs were removed. (A). Representative image of labelled PDPN + and PDPN- cells that were arrested in the lung 2 h after cell injection. Scale bar = 50 μm. (B). The average numbers of labelled tumour cells per microscopic field were determined in cryotome-cut lung sections at each time point. At least 6 images for each lung were analysed. (**P < 0.01) (C). The average number of labelled cells in WT mice and CLEC-2 KO mice 30 min after injection. (**P < 0.01) (D). Graph showing the ratio of the decrease in platelet number (determined with the MASCOT haematology system) 3 min after injection of tumour cells compared to the platelet number before injection. Six mouse blood samples from each group were analysed. (***P < 0.001) (E). Cryosections of the lungs were stained for platelets with an anti-CD41 antibody. (F). The numbers of labelled PDPN + and PDPN- cells associated with platelets determined by evaluating the sections. Seven images for each section were analysed. Data are means ± SEMs. (***P < 0.001)