Role of oxidative stress and neutrophil reprogramming in mediating venous thrombosis in colorectal cancer.

Abstract

e15733 Background: Colorectal cancer associated venous thrombosis (CRC-VT) is a major cause of mortality in CRC patients, yet the mechanisms linking CRC to thrombosis remain unclear. NETosis, a process in which neutrophils release prothrombotic extracellular traps (NETs), is elevated in various cancers. However, the mechanisms of cancer-associated NETosis and its contribution to CRC-VT remain unknown. We hypothesized that CRC associated reactive oxygen species (ROS) reprogram neutrophil toward a pro-NETotic phenotype promoting a prothrombotic state. Methods: C57BL/6J wild-type (WT) mice were subcutaneously injected with murine CRC cells (MC38). Neutrophil subpopulations were characterized by spectral flow cytometry. Spontaneous and agonist induced NETosis in bone marrow-derived neutrophils was quantified by immunostaining. Pharmacological and genetic approaches were used to assess contribution of ROS to NETosis. Venous thrombosis susceptibility was evaluated using inferior vena cava (IVC) stenosis model. DNase I treatment for NET degradation, Ly6G-mediated neutrophil depletion, and Nox2-KO mice were used to assess causality. Nox2-NADPH oxidase is the key superoxide generating enzyme in neutrophils and drives NETosis. Results: C57BL/6J mice bearing CRC-tumors exhibited elevated circulating neutrophils and H3Cit (a marker of NETosis). Spectral flow cytometry showed reduced maturation marker CD16 but elevated migration/activation markers (CD11b, CD62L), co-localized with H3Cit, indicating a CRC-driven-pro-NETotic reprogramming. Neutrophils displayed altered nuclear morphology with loss of lobulation, suggesting expansion of immature subsets. Bone marrow-derived neutrophils showed increased spontaneous and agonist-induced NETosis, suppressed by Nox2 inhibition or antioxidants. Finally, in IVC stenosis model, tumor-bearing mice developed larger thrombi, which were significantly reduced by DNase I treatment or Ly6G-mediated neutrophil depletion. Furthermore, tumor-bearing Nox2-KO mice showed reduced NET formation and venous thrombosis, suggesting that Nox2 mediated NETosis contributes to thrombosis in CRC model. Conclusions: ROS-driven neutrophil reprogramming links CRC to venous thrombosis. Our data may support ROS/NETs as potential targets to reduce CRC-VT burden.