Prediction of Chronic Lung Graft-Versus-Host Disease By Angiopoietin-2

Background: Severe chronic graft versus host disease (cGVHD) of the lung is a rare but often fatal complication of allogeneic stem cell transplantation (SCT). In order to identify patients at high risk of lung cGVHD prior to transplant, the aim of the present study was to test systematically candidate biomarkers for this purpose, thereby focusing on endothelial risk factors previously shown to be associated with the risk of refractory acute GVHD. These factors included angiopoietin-2 (ANG2), serum nitrates and asymmetric dimethylarginine (ADMA), as well as single nucleotide polymorphisms (SNPs) in the thrombomodulin gene (THBD).

Methods: Patients were eligible if they were allo-grafted between June 2002 and December 2011 at our institution, and if their blood samples were available for nitrate, ANG2 and ADMA measurement at different landmarks (collected immediately before conditioning and on day +100 after allogeneic SCT). Concentrations of ANG2, ADMA and serum nitrates were quantified in patients’ sera by the multiplex protein array technology (Luminex). THBD SNP genotyping was performed using KASPar SNP Genotyping System v2.0 of K Bioscience in 384-well format. Cumulative incidence analysis of cause-specific hazards was performed. The occurrence of cGVHD was evaluated retrospectively by chart review applying clinical and histological criteria developed by the National Institute of Health’s consensus project (Filipovich et al., 2005).

Results: Of a total sample of 329 eligible patients, 14 (4%) fulfilled the criteria for lung cGVHD. 19 out of 329 patients (6%) developed severe gastrointestinal cGVHD and 15 out of 329 patients (4%) developed sclerodermatous cGVHD. Elevated pre-transplant levels of ANG2 (> 1000 pg/ml) correlated with the incidence of lung cGVHD (p=0.037). In contrast, there was no association between pre-transplant levels of ANG2 and severe gastrointestinal cGVHD (p=0.684) or sclerodermatous cGVHD (p=0.242). Similarly, high ANG2 levels (> 4000 pg/ml) on day +100 after allogeneic SCT predicted lung cGVHD (p=0.009). Again, this effect was specific for lung cGVHD, as there was no association between high ANG2 levels on day +100 and sclerodermatous cGVHD (p=0.300) or severe gastrointestinal cGVHD (p=0.702). There was no correlation between lung cGVHD and antecedent acute GVHD (p=0.796). Moreover, no significant correlations between serum nitrates, ADMA and thrombomodulin-(THBD)-SNPs and the risk of lung cGVHD or any other manifestation of severe cGVHD could be identified.

Conclusion: In contrast to other endothelial markers, elevated pretransplant and d +100 post-transplant ANG2 levels may be predictors of a high risk of lung cGVHD but not of gastrointestinal or sclerodermatous cGVHD. These preliminary results warrant validation by further studies. Moreover, this data suggests a different role of the endothelial component in the pathogenesis of acute vs chronic GVHD.