Ex Vivo Treatment of Umbilical Cord Blood with Prostaglandin E2 Alters the Molecular and Functional Properties of T Cells Via Modulating Wnt/β-Catenin Signaling

The favorable outcome of umbilical cord blood transplantation (UCBT) is compromised by prolonged time to engraftment, delayed immunologic reconstitution and late memory T cell skewing. Studies in zebrafish and mice have shown that the prostaglandin compound, 16,16 dimethyl prostaglandin E2 (PGE₂) increases HSC engraftment. We performed a Phase Ib clinical trial of double UCBT (dUCBT) using one untreated and one ex vivo PGE₂-treated UCB unit to determine safety and engraftment. 12 subjects with hematologic malignancies were enrolled. The PGE₂-UCB was the dominant source of hematopoiesis in 10 of 12 subjects with full T cell chimerism detected as early as 13 days. In UCB T cells, PGE₂ mediated increase of intracellular cAMP, activation of PKA and modulated the Wnt/β-catenin pathway as determined by upregulation of β-catenin and expression of Wnt target genes Lef1, Tcf7 and Runx1. PGE₂ inhibited proliferation of UCB T cells in response to stimulation via CD3/CD28 and resulted in high expression of IL-7 receptor (CD127). Assessment of T cell reconstitution indicated that during the first year, the numbers of total T cells (CD3⁺), CD4⁺ and CD8⁺ T subsets remained significantly lower (p=0.036) in PGE₂-UCBT recipients compared to dUCBT recipients without PGE₂. To examine whether PGE₂-mediated Wnt/β-catenin imprinting might be evident in PGE₂-UCBT recipients, we examined expression of the Wnt/β-catenin target Eomes, a transcription factor that links the long-term memory CD8⁺ T cells to effector potency and protective immunity. Expression of Eomes was significantly elevated in PBMCs of PGE₂-UCBT recipients compared to controls. Consistent with the role of Wnt/β-catenin to maintain a central memory/stem cell memory CD8⁺ phenotype, there was an increased fraction of CD8⁺CD62L⁺ cells in recipients of PGE₂-UCBT in contrast to the late memory T cell skewing in dUCBT recipients without PGE₂. Moreover, PGE₂-UCBT recipients displayed potent antiviral immunity resulting in a reduced incidence of CMV viremia and no EBV-mediated posttransplant lymphoproliferative disorder. Our findings indicate that PGE₂-UCB treatment induces Wnt-mediated gene programming and might favor the generation of long-lived memory CD8⁺ T cells.