Neutrophil extracellular trap formation is an independent risk factor for occult cancer in patients presenting with venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE), particularly unprovoked VTE, is associated with occult cancer. The optimal screening regimen remains controversial. Neutrophil extracellular traps (NETs) are implicated in cancer-associated thrombosis, and elevated biomarkers of NET formation are associated with poor prognosis.

OBJECTIVES

To investigate the association between NET formation and occult cancer in patients with VTE.

METHODS

Blood biomarkers associated with NETs and neutrophil activation (nucleosomal citrullinated histone H3 [H3Cit-DNA], cell-free DNA, and neutrophil elastase) were quantified in patients with VTE. The primary outcome was cancer diagnosed during a one-year follow-up.

RESULTS

This study included 460 patients with VTE, of which 221 (48%) had isolated deep vein thrombosis. Forty-three patients had active cancer at inclusion and were excluded from the primary analysis Cancer during follow-up was diagnosed in 29 of 417 (7.0%) patients. After adjustment for age and unprovoked VTE, the hazard ratio of cancer during follow-up per 500 ng/mL increase of H3Cit-DNA was 1.79 (95% CI, 1.03-3.10). Furthermore, patients with cancer-associated VTE (known active cancer or cancer diagnosed during follow-up) had higher levels of H3Cit-DNA than cancer-free patients with VTE after adjustment for age, hemoglobin, gender, chronic obstructive pulmonary disease, previous cancer, and start of anticoagulant treatment (odds ratio 2.06 per 500 ng/mL increase of H3Cit-DNA [95% CI, 1.35-3.13]).

CONCLUSIONS

H3Cit-DNA is an independent predictor for occult cancer in patients with VTE and elevated in cancer-associated VTE, suggesting that H3Cit-DNA is potentially a useful diagnostic marker for cancer in patients with VTE and that elevated NET formation is a hallmark of cancer-associated VTE.

Appropriate sera for calibration and control of specific protein assays

An ultracentrifugation technique is described which makes it possible to prepare protein calibrators and control sera which (i) are stable (more than 8 years documented for nine proteins), (ii) are clear (remains clear for more than 8 years at -80 degrees C), (iii) contain genuine proteins (documented electrophoretically and immunologically), and (iv) are reproducible to prepare (collection and preparation).

Metabolism of C3 and factor B in patients with congenital factor I deficiency

The metabolism of complement factor B and C3 was analyzed in three previously described patients with congenital deficiency of factor I (C3b/C4b inactivator). Samples taken at steady state contained elevated levels of Ba and Bb, whereas native factor B was not detectable. Following plasma infusion in two of the patients Ba was rapidly cleared (within 8-12 hr) from the circulation and native factor B increased transiently, reaching normal levels within 22-24 hr. In parallel with the increase in Ba, factor B decreased during the following days, reaching preinfusion level after seven days. This was in contrast to a continued increase in C3 concentration, which was still within the normal range 15 days after infusion, despite the presence of only trace amounts of native B. In vitro complement activation experiments, employing purified C3Nef IgG as alternative pathway activator and aggregated IgG as classical pathway activator, were performed on selected serum samples (base-line, 12 hr and 15 days postinfusion samples) from the plasma infusion series. It was demonstrated that (a) C3Nef could not induce alternative pathway C3-conversion in factor B depleted samples and (b) C3-degradation by CP-activation could still occur in B-depleted samples, although at a much slower rate compared to normal human serum. These results may partly explain the difference in kinetics of factor B and C3 metabolism seen after plasma infusion in patients with factor I deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

A new micromethod for routine measurement of serum LDL-apolipoprotein B

A new method for low density lipoprotein (LDL) (d 1.019-1.063 g/ml)-apolipoprotein B (apoB) determination has been developed, based on the fact that very low density and intermediate density lipoproteins (VLDL and IDL) contain apolipoprotein C-I (apoC-I), whereas this apolipoprotein is apparently absent in LDL. VLDL and IDL were quantitatively precipitated with a monospecific anti-apoC-I antibody whereafter LDL-apoB in the supernatant was quantitated by Laurell rocket electrophoresis. Over a wide range of cholesterol and triglyceride values there was a linear correlation with LDL-apoB values measured after ultracentrifugation. The method would be useful for routine measurements, especially in children, since only 25 microliter of serum is required, and for making the diagnosis of hyperapobetalipoproteinemia, which at present is complicated.