INVESTIGATING NEUTROPHIL EXTRACELLULAR TRAPS AS A POSSIBLE PROGNOSTIC MARKER IN DIFFUSE LARGE B-CELL LYMPHOMA AND CLASSICAL HODGKIN LYMPHOMA

Abstract

Introduction: Neutrophil extracellular traps (NETs) are complexes of decondensed chromatin and granule proteins that can be released from activated neutrophils during infections or in inflammatory conditions, including cancer. Accumulation of NETs in tissues and blood can contribute to increased inflammation, thrombosis and organ damage. In several types of solid cancers, NETs have been shown to facilitate metastasis and tumour growth, leading to a worse prognosis. However, little is known about the role of NETs in malignant lymphomas.

Methods: The concentration of NETs was analysed in plasma samples taken at diagnosis from patients with diffuse large B-cell lymphoma (DLBCL, n = 227) and classical Hodgkin lymphoma (cHL, n = 117) in the Uppsala Umeå Comprehensive Cancer Consortium (U-CAN) biobank. Plasma from blood donors (n = 54) were used as healthy controls. NETs were measured using a commercial enzyme-linked immunosorbent assay (ELISA) targeting complexes of citrullinated histones and extracellular DNA, a biomarker with high specificity for NETs. Clinical data, including blood counts at diagnosis and treatment outcome, was extracted from patient records and analysed in relation to the plasma concentrations of NETs.

Results: Higher concentrations of NETs were seen in plasma from DLBCL patients (range 0.62 to 200 ng/ml) compared to cHL patients (p < 0.01, range 0.58 to 62 ng/ml) and healthy controls (p < 0.001, range 1.0 to 37 ng/ml). The level of NETs in cHL was not significantly higher than in control samples. In both DLBCL and cHL, a poorer overall survival was seen in patients with concentrations of NETs above median (7.4 and 5.6 ng/ml respectively, p < 0.05). There was no significant correlation between progression free survival and NETs. In cHL, there was a positive correlation between elevated levels of NETs and age above 45 years (p < 0.05), but no correlation to age was shown in DLBCL. The NET levels did not significantly differ between the sexes. A trend, although not significant, could be seen with increased NET levels in higher stages of both DLBCL and cHL. The plasma concentration of NETs in both lymphoma diseases showed a positive correlation with the neutrophil count in blood (p < 0.05), as well as erythrocyte sedimentation rate (ESR) above 50 mmHg (p < 0.01) at diagnosis.

Conclusions: In line with previous studies on NETs in cancer, we show that high levels of NETs in plasma correlates with worse survival for both DLBCL and cHL patients. However, plasma concentrations were only significantly increased in DLBCL compared to healthy controls, with no correlation to age or sex. Based on the results, NETs could be a possible prognostic marker to further investigate in malignant lymphoma. In both DLBCL and cHL, higher levels of NETs were seen in patients with elevated neutrophil count and high ESR, a sign of inflammation, at time of diagnosis. This suggests that NETs might play a role in the inflammatory aspects of the diseases.

Keywords: aggressive B-cell non-Hodgkin lymphoma; diagnostic and prognostic biomarkers; Hodgkin lymphoma

No potential sources of conflict of interest.