Developing novel therapies to improve blood stem cell transplantation outcomes

PROJECT SUMMARY Acute Graft-versus-host disease (aGVHD) is a frequent and lethal complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in which donor T cells destroy HLA mismatched host tissues by secreting inflammatory cytokines (TNF-α and IFN-γ) and/or inducing direct cytotoxic cellular responses. Despite recent advances, aGVHD still remains a major clinical problem, underscoring the need to elucidate further its mechanisms to then develop novel therapeutic strategies. In this proposal, we are investigating epithelial growth factor like 7 (EGFL7) as a potential modulator of aGVHD. EGFL7 is a repressor of endothelial cell activation which plays an important physiological role in angiogenesis. Recently, it has also been documented that EGFL7 plays a significant role in regulating inflammation by repressing endothelial cell activation in response to the inflammatory cytokines such as TNF-α. The repression of endothelial cell activation by EGFL7 results in reduced expression of cellular adhesion molecules such as ICAM-1, VCAM, and E-Selectin, which results in reduced adhesion and extravasation of inflammatory cells into target tissues. Based on these data, we hypothesized that increasing EGFL7 levels after allo-HSCT will diminish the severity of aGVHD by interfering with the migration of T cells to the target tissues. Our preliminary data showed that treatment with recombinant EGFL7 (rEGFL7) in two different murine models of aGVHD decreases aGVHD severity and improves survival in recipient mice after allogeneic transplantation with respect to controls without affecting graft versus leukemia (GVL) effect. Furthermore, we showed that rEGFL7 treatment results in higher thymocytes, T, B and dendritic cells in recipient mice after allo-HSCT. Overall, our preliminary data support a role for EGFL7 in the modulation of aGVHD. In this proposal, we would like to dissect the mechanisms by which EGFL7 modulates aGVHD and impact on immune BM reconstitution and to perform preclinical studies using rEGFL7 as a therapy to prevent and treat aGVHD. We are planning to achieve these goals by performing the following aims: Specific Aim 1: To dissect the mechanisms by which EGFL7 modulates aGVHD and impact on immune reconstitution. In this aim, we will systematically assess endothelial cell activation status and T cell phenotypes in murine models of aGVHD after EGFL7 therapy. Furthermore, we will explore whether EGFL7 has any direct effects on T cell function and intestinal stem cells. Last, we will investigate the EGFL7 effects on immune reconstitution. Specific Aim 2: To perform preclinical studies using rEGFL7 as a therapy to prevent and treat aGVHD. In this aim, we would like to perform initial toxicology, pharmacokinetics and pharmacodynamic studies to select the best dose and schedule to prevent and treat aGVHD. In addition, we would like to investigate whether rEGFL7 therapy is effective in a steroid refractory aGVHD murine model. Impact: The identification of EGFL7 as new therapy for GVHD will benefit primarily patients undergoing allo- HSCT to cure hematologic malignancies.