Gene-Expression Profile of Steroid-Refractory Acute Graft-Versus-Host Disease.

Abstract 4549

Steroid-refractory acute graft-versus-host disease (aGVHD) remains to be the major complication of allogeneic hematopoietic stem cells transplantation (allo-HSCT). aGVHD is characterized by tissue injury and is associated with high morbidity and mortality, most notably in cases of severe course and/or resistance to corticoids. aGVHD appears usually within the first 100 days after transplantation. This study should lead to identification of molecular patterns characterizing patients’ sensitivity or resistance to corticoid therapy. We performed an oligonucleotide microarray analysis (whole genome Human OneArray, Phalanx) of 13 patients with hematological malignancies who received allo-HSCT. Peripheral blood samples were collected at the time of aGVHD manifestation and subsequently mononuclear cells were isolated (Ficoll-Paque gradient). In total, five patients with resistance, and eight patients with sensitivity to corticoids were included in the analysis. The significance analysis of micorarrays (SAM) revealed a set of differentially expressed genes: GBP5 (guanylate binding protein 5), PRG3 (proteoglycan 3), CDK5RAP2 (CDK5 regulatory subunit associated protein 2), and, especially, ARG1 gene (arginase, liver) whose expression was significantly higher in the group of resistant patients (with 4.89-fold change). As published earlier, arginase is released from human granulocytes during purulent inflammatory reactions and induces a suppression of T-cell proliferation and cytokine synthesis (Munder et al., 2006). These findings might confirm our hypothesis that expression levels of ARG1 gene could reflect the severity of aGVHD. ARG1 gene was detected apparently in a fraction of immature forms of granulocytes which are released into the peripheral blood after allo-HSCT. Thus, both immature granulocytes and mononuclear cells are then isolated using Ficoll-Paque gradient. To validate arginase as a marker of unfavorable grade of aGVHD, it is necessary to examine expression profile of ARG1 gene in neutrophils. Therefore, it is important to separate both mature and immature forms of neutrophils (using different method than Ficoll gradient), as well as examine gene expression profile of a down-regulated CD3ζ chain in T-cells. Down-regulation of CD3ζ chain is due to arginase-mediated depletion of arginine in the T-cell environment (Munder et al., 2006). We assume that ARG1 gene expression profile might have a potential to influence patients′ response to corticoid therapy of unfavorable grade of aGVHD. This study is in progress and further analyses will be focused on monitoring of ARG1 and CD3ζ chain expression levels in a larger cohort.

Supported by IGA MZ CR NS9683-4/2008 and MSMT CR MSM0021622430.