Biomarkers of Extracellular Matrix Remodeling in Chronic Gvhd

Chronic GVHD (cGVHD) is the most important long-term complication of allogeneic transplantation (HCT). It evolves from immune-mediated inflammation to fibrogenesis, resulting in end organ damage such as sclerotic skin and bronchiolitis obliterans syndrome. Thus, biomarkers of extracellular matrix (ECM) remodeling and fibrosis may provide insight into the biology of the disease and contribute to diagnosis and outcome prediction. In order to identify promising candidates, we conducted a discovery experiment in 112 adult patients (median age 52.5 y, range 18-68) with new onset cGVHD.  Median time to onset of cGVHD was 165 d (range 37-547) post-HCT.  Overall NIH severity at onset was mild (n=16, 14%), moderate (n=53, 47%) or severe (n=43, 39%).  The majority of patients had at least one overlap feature (elevated liver enzymes, erythematous rash or GI symptoms; 80%). Plasma samples were obtained at the time of cGVHD onset, biomarkers were assayed simultaneously using a lab-derived (non-commercial) Luminex bead-based assay, and levels of each analyte (assessed by deciles) that provided the best discrimination with survival were determined.   Levels of 3 profibrotic proteins (CCL2, IGF-1, IL-13Rα) significantly correlated with TGF-β levels.  Of these, TGF-β provided the strongest association with outcomes 1 y post-onset of cGVHD.  Patients with low TGF-β (≤ 10 pg/ml; n=36) were 3 times more likely to relapse (Cumulative Incidence (CI) 17% vs 5%, p=0.05) and 4 times more likely to experience NRM (CI 23% vs 5%, p=0.01) than patients with high TGF-β (> 10 pg/ml; n=76).   These increases resulted in lower progression free survival (PFS 60% vs 89%, p=0.001) and overall survival (OS 72% vs 92%, p=0.01).  Low TGF-β was also significantly correlated with the following features at onset:  low performance status (p=0.01), platelet < 100K (p=0.01), and NIH lung 2/3 (p=0.01). However, the impact of low TGF-β on OS and PFS was independent of each of these factors when assessed in bivariate analysis.  There was no correlation with TGF-β levels and other characteristics such as patient age, diagnosis, high risk disease at HCT, donor type, overall NIH score or progressive onset cGVHD.  Patients in the high TGF-β group and high IL-13 group (>200 pg/ml) were more likely to later develop sclerotic skin (n=20) (TGF-β 80% vs 65%, p=0.1; IL-13 85% vs 62%,p=0.04).  On the other hand, low level MMP2 (≤ 5000 pg/ml), an antifibrotic metalloproteinase, were more likely to develop sclerotic cGVHD (50% vs 21%, p=0.007).  These results suggest ECM turnover is active at the time of cGVHD onset, even prior to the development of clinically apparent sclerosis. Further investigation of factors that impact the balance and transition between inflammation and fibrosis may provide a better understanding of the pathophysiology and new biomarker opportunities for cGVHD.