Association of HMGB1 Polymorphisms with Outcome After Allogeneic Hematopoietic Cell Transplantation.

Abstract 2260

Poster Board II-237

Several studies have demonstrated that genetic variation in cytokine genes can modulate the immune reactions after allogeneic hematopoietic cell transplantation (HCT). High mobility group box 1 protein (HMBG1) is a pleiotropic cytokine that functions as a proinflammatory signal, important for the activation of antigen presenting cells (APC) and propagation of inflammation. HMGB1 is implicated in the pathophysiology of a variety of inflammatory diseases, and we have recently found the variation in the HMGB1gene to be associated with mortality in patients with systemic inflammatory response syndrome (SIRS). To assess the impact of the genetic variation in HMGB1 on outcome after allogeneic HCT, we genotyped 276 and 146 patient/donor pairs treated with allogeneic HCT for hematologic malignancies following myeloablative or non-myeloablative conditioning. Associations between genotypes and outcome were only observed in the cohort treated with myeloablative conditioning. Patient homozygosity or heterozygosity for the –1377delA minor allele was associated with increased risk of relapse (hazard ratio (HR) 2.11, P=0.02) and increased relapse related mortality (RRM) (P=0.03). The –1377delA minor allele has previously been associated with mortality in patients with SIRS, and although SIRS and allogeneic HCT are different entities the confirmative association of this polymorphic locus with mortality in 2 independent studies suggests that it is of pathophysiological importance. The three polymorphisms, 3814C>G, 1177G>C and 2351insT, tended to have the same effect on transplantation outcome, due to a moderate to strong linkage disequilibrium between loci. Of these three polymorphisms, patient homozygosity for the 3814C>G minor allele showed the strongest association with increased overall survival (HR 0.13, P=0.04), progression free survival (HR 0.30, P=0.05) and decreased probability of RRM (P=0.03). Patient carriage of the 2351insT minor allele reduced the risk of grade 2 to 4 acute graft versus host disease (GVHD) (HR 0.60, P=0.01), while donor carriage of the minor allele displayed a gene dosage effect, with a successive increase in risk of developing limited or extensive chronic GVHD per minor allele carried (HR 1.54, P=0.01). That patient HMGB1 genotypes were associated with outcomes dependent on primarily patient APCs, and that donor genotypes were associated with a, in part, donor APC dependent outcome, could suggest that the polymorphisms in HMGB1 influence the transcription of HMGB1 in APCs induced by the proinflammatory milieu after myeloablative conditioning, rather than the passively released from damaged cells, although these two mechanisms are not mutually exclusive. Our findings suggest that the inherited variation in HMGB1 is associated with outcome after allogeneic HCT following myeloablative conditioning. None of the polymorphisms were associated with treatment related mortality.