GPVI–galectin-3 interaction promotes tumor cell extravasation and subsequent metastasis. (A,C) Representative fluorescence microscopy images of lung sections of WT, Gp6^−/− (A) and Syk^+/+ and Syk^−/− (C) mice 6 hours after IV injection of MC38-CFSE cells (green). Lung vessels were stained for endoglin (CD105, red). Asterisks indicate lung alveoli. The bar represents 10 µm. (B-D) The bar graphs show the percentage of intravascular and extravascular MC38-CFSE cells in lungs of WT, Gp6^−/−, Syk^+/+ and Syk^−/− mice; n = 4 mice per group; *P < .05, by Fisher’s exact test. (E-F) MC38 and AT-3 tumor cells were injected subcutaneously (E) or directly into the tail vein (F) of Syk^+/+ and Syk^−/− mice. Spontaneous and experimental lung metastasis were determined at 30 and 15 days after injection, respectively. (E) Quantification showing primary tumor volume (left) and number of metastases (right). (F) Metastases in lungs of Syk^+/+ and Syk^−/− mice. Data are presented as the mean ± standard deviation (SD); n = 5 mice per group; *P < .05; **P < .01, by Mann-Whitney test.