Gas6 deficiency protects mice against lung cancer-induced venous thrombosis. (A) WT and Gas6^−/− mice were injected with M27 cancer cells. After 14 days for the WT mice and 17 to 21 days for the Gas6^−/− mice, lung weight was measured to ascertain similar tumor burden. Lung weight was increased equivalently in WT and Gas6^−/− mice. WT mice injected with M27 cancer cells developed significantly larger thrombi compared with WT mice injected with phosphate-buffered saline. Gas6^−/− mice did not develop larger thrombi as seen by (B) clot weight, (C) H&E staining of thrombus sections (bars, 100 μm), and (D) higher magnification of H&E staining (bar, 10 μm). (E) Quantifications of the H&E staining expressed as thrombus size. (F) Cross-sectional area measured by ultrasonography confirmed that lung cancer increased venous thrombosis in WT but not Gas6^−/− mice. Injection of rGas6 restored the WT phenotype in Gas6^−/− mice. *P < .05 comparing WT vs WT + M27, WT vs WT + rGas6, and WT vs WT + rGas6 + M27; **P < .05 comparing Gas6^−/− vs Gas6^−/− + rGas6, Gas6^−/− vs Gas6^−/− + M27, and Gas6^−/− vs Gas6^−/− + rGas6 + M27; ***P < .05 comparing WT vs Gas6^−/−. n.s., not significant.