Galectin-3 on tumor cells mediates lung metastasis through platelet GPVI. Control (Ctrl) and galectin-3–deficient (Lgasl3 KO), MC38 and AT-3 tumor cells were injected subcutaneously (A) or directly into the tail vein (C-E) of WT, Gp6^−/− (B-E) and Lgals3^−/− or Gp6^−/−Lgals3^−/− (E) mice. Spontaneous (B) and experimental (C-E) lung metastasis were determined 30 or 15 days after injection, respectively. Quantification of primary MC38 tumor volume (A) and metastases (B-E) in lungs of WT, Gp6^−/− (B-E) and Lgals3^−/− or Gp6^−/−Lgals3^−/− (E) mice. Data are presented as the mean ± standard deviation (SD); n = 6 (A-C) and 5 (D-E) mice per group. *P < .05; **P < .01; ***P < .001; ****P < .0001, by 1-way analysis of variance followed by Tukey’s post hoc test. TC, tumor cells.