ADAMTS13 as a thromboinflammatory brake at the vascular-immune interface: from viral immunothrombosis to the tumor microenvironment.
ADAMTS13 is conventionally regarded as the protease whose severe deficiency causes thrombotic thrombocytopenic purpura (TTP). By cleaving shear-unfolded ultra-large and high-molecular-weight von Willebrand factor (VWF), ADAMTS13 limits a platelet- and leukocyte-adhesive vascular scaffold. We propose a narrower and testable extension of this biology to cancer: an imbalance between VWF burden and ADAMTS13 processing capacity may act as a context-dependent modifier or amplifier of thromboinflammation in selected VWF-rich, shear-exposed tumor vascular niches, but is not established as an initiating or universally rate-limiting cause of cancer-associated thrombosis. We define "relative ADAMTS13 insufficiency" as a research phenotype rather than a diagnosis or evidence of causality. It refers to ADAMTS13 activity outside the severe-deficiency range, typically ≥10%, together with increased VWF burden and a disproportionately low ADAMTS13 activity/VWF antigen ratio (ADAMTS13:Act/VWF: Ag). This phenotype is mechanistically nonspecific and may reflect increased VWF release, impaired whole-molecule VWF clearance, reduced ADAMTS13 production, stability, or availability, functional inhibition of proteolysis, reduced VWF susceptibility to cleavage, or shared upstream inflammation. Human evidence from COVID-19 and cancer remains predominantly associative, whereas tumor-relevant perturbation studies provide preclinical causal support in defined models. The causal importance of the VWF-ADAMTS13 axis in human tumors nevertheless remains unproven. We therefore position this module within a broader thromboinflammatory network that includes complement activation, neutrophil extracellular traps, platelet activation, and tissue factor-thrombin-fibrin pathways. ICI-associated endothelial phenotypes are distinguished from rare ICI-associated immune TTP with categorical severe ADAMTS13 deficiency. Candidate interventions are accordingly presented as mechanistic research nodes requiring staged validation rather than as established oncology therapies.