Prognostic Impact of Follistatin in Acute Graft-Versus-Host Disease: Results from BMT CTN 0302 and 0802

Background:  Neovascularization and endothelial dysfunction are recognized sequelae of acute graft-versus-host disease (aGVHD).  We hypothesized that patients with abundant angiogenic factors (AF) involved in repair/regeneration would have improved survival relative those with higher levels of AF involved in damage/inflammation.

Patients and Methods:  We measured circulating levels of AF known predominantly for repair/regeneration (epidermal growth factor [EGF], fibroblast growth factor [FGF]-1, FGF-2, heparin binding-EGF-like growth factor, follistatin [FS], vascular endothelial growth factor [VEGF]-A, VEGF-C, and VEGF-D) and those known predominantly for endothelial dysfunction/inflammation (angiopoietin-2 [Ang2], endothelin-1, soluble endoglin [sEng], leptin, placental growth factor [PlGF]) in HCT recipients with grade III-IV aGVHD (N=17) compared to recipients without aGVHD (N=17) and healthy stem cell donors (HD, N=16) in a pilot study.  AF demonstrating <0.5-fold or >1.5-fold difference in median with p≤0.1 were validated in two cohorts of patients with aGVHD enrolled in Blood and Marrow Transplant Clinical Trials Network (BMT CTN) trials 0302 (N=105, serum) and 0802 (N=158, plasma). Samples were analyzed at aGVHD onset and day 28 post-aGVHD treatment and compared to control samples obtained at day +100 from University of Minnesota allogeneic hematopoietic cell transplant (HCT) recipients without aGVHD (N=53, serum). 

Results:  In the pilot study, significant differences in the levels of FS, EGF, VEGF-A, PlGF, Ang2, and sEng were found when comparing patients with aGVHD, allogeneic HCT recipients without aGVHD, and HD in the pilot study. In the CTN validation cohorts (Figure 1), VEGF-A and EGF were significantly lower in patients with aGVHD compared to HCT controls.  FS, sEng, and PlGF were all significantly elevated in patients with aGVHD compared to controls.  In multivariate analyses of 6-month survival including age, stage, and day 28 response in the validation cohorts, the day 28 FS level was an independent prognostic factor for survival in both CTN 0302 (HR 9.3, 95% CI 1.3 – 59.1, p=0.002) and 0802 (HR 2.8, 95% CI 1.04 – 6.9, p=0.04), with outcomes significantly worse when day 28 FS > 2000 pg/mL (Figure 2).

Conclusions:  Three circulating AFs are elevated in patients with aGVHD: FS, sEng and PlGF.  The level of FS at day 28 post aGVHD was an independent prognostic factor for survival in both CTN 0302 and 0802.  Although FS is important for regeneration after injury, excess FS may reflect more extensive tissue, especially endothelial, damage or loss, leading to higher mortality.  Studies aimed at identifying the source and mechanism of FS in aGVHD are ongoing.  Our results contribute to the growing body of knowledge supporting the endothelium as a relevant target of aGVHD in need of dedicated protection or therapy.