['Multiple studies suggest that the hemostatic and innate immune systems functionally cooperate in establishing the fraction of tumor cells that successfully form metastases. In particular, platelets and fibrinogen have been shown to support metastatic potential through a mechanism coupled to natural killer (NK) cell function. As the transglutaminase that ultimately stabilizes platelet/fibrin thrombi through the covalent crosslinking of fibrin, factor (F) XIII is another thrombin substrate that is likely to support hematogenous metastasis.', 'Directly define the role of FXIII in tumor growth, tumor stroma formation, and metastasis.', 'Tumor growth and metastatic potential were quantitatively and qualitatively evaluated in wild-type mice and gene-targeted mice lacking the catalytic FXIII-A subunit.', 'Loss of FXIIIa function significantly diminished hematogenous metastatic potential in both experimental and spontaneous metastasis assays in immunocompetent mice. However, FXIII was not required for the growth of established tumors or tumor stroma formation. Rather, detailed analyses of the early fate of circulating tumor cells revealed that FXIII supports the early survival of micrometastases by a mechanism linked to NK cell function.'] Does factor XIII transglutaminase support hematogenous tumor cell metastasis through a mechanism dependent on natural killer cell function?