Culture-Expanded Human Invariant Natural Killer T Cells Suppress T-Cell Alloreactivity and Eradicate Leukemia

Graft-versus-host disease (GVHD) is a major cause of significant morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Invariant natural killer T (iNKT) cells are potent regulators of immune responses, protect from lethal GVHD, and promote graft-versus-leukemia effects in murine studies. Since iNKT cells constitute less than 0.5% of human peripheral blood mononuclear cells (PBMCs), in vitro expansion with their glycolipid ligands is required before they can be used for cytotherapy and experimental purposes. Three weeks of cell culture and autologous restimulation with either KRN7000, PBS44, or PBS57 resulted in a robust proliferation of iNKT cells from human PBMCs. Next, iNKT cells were sorted to a purity higher than 90% being crucial for further experimental and clinical applications. These iNKT cells significantly decreased activation and proliferation of allogeneic CD3+ T lymphocytes. In addition, leukemia cell lines and primary leukemia cells were efficiently lysed by culture-expanded iNKT cells. Importantly, culture-expanded donor iNKT cells promoted robust antileukemia activity against HLA-matched allogeneic patient leukemia cells. Our data indicate that the adoptive transfer of culture-expanded iNKT cells could be a powerful cytotherapeutic approach to induce immune tolerance and prevent leukemia relapse after allogeneic HCT in humans

MAT2A as Key Regulator and Therapeutic Target in MLLr Leukemogenesis

Epigenetic dysregulation plays a pivotal role in mixed-lineage leukemia (MLL) pathogenesis, therefore serving as a suitable therapeutic target. S-adenosylmethionine (SAM) is the universal methyl donor in human cells and is synthesized by methionine adenosyltransferase 2A (MAT2A), which is deregulated in different cancer types. Here, we used our human CRISPR/Cas9-MLL-rearranged (CRISPR/Cas9-MLLr) leukemia model, faithfully mimicking MLLr patients’ pathology with indefinite growth potential in vitro, to evaluate the unknown role of MAT2A. Comparable to publicly available patient data, we detected MAT2A to be significantly overexpressed in our CRISPR/Cas9-MLLr model compared to healthy controls. By using non-MLLr and MLLr cell lines and our model, we detected an MLLr-specific enhanced response to PF-9366, a new MAT2A inhibitor, and small interfering (si) RNA-mediated knockdown of MAT2A, by alteration of the proliferation, viability, differentiation, apoptosis, cell cycling, and histone methylation. Moreover, the combinational treatment of PF-9366 with chemotherapy or targeted therapies against the SAM-dependent methyltransferases, disruptor of telomeric silencing 1 like (DOT1L) and protein arginine methyltransferase 5 (PRMT5), revealed even more pronounced effects. In summary, we uncovered MAT2A as a key regulator in MLL leukemogenesis and its inhibition led to significant anti-leukemic effects. Therefore, our study paves the avenue for clinical application of PF-9366 to improve the treatment of poor prognosis MLLr leukemia

presentation_1_Culture-Expanded Human Invariant Natural Killer T Cells Suppress T-Cell Alloreactivity and Eradicate Leukemia.pdf

<p>Graft-versus-host disease (GVHD) is a major cause of significant morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Invariant natural killer T (iNKT) cells are potent regulators of immune responses, protect from lethal GVHD, and promote graft-versus-leukemia effects in murine studies. Since iNKT cells constitute less than 0.5% of human peripheral blood mononuclear cells (PBMCs), in vitro expansion with their glycolipid ligands is required before they can be used for cytotherapy and experimental purposes. Three weeks of cell culture and autologous restimulation with either KRN7000, PBS44, or PBS57 resulted in a robust proliferation of iNKT cells from human PBMCs. Next, iNKT cells were sorted to a purity higher than 90% being crucial for further experimental and clinical applications. These iNKT cells significantly decreased activation and proliferation of allogeneic CD3+ T lymphocytes. In addition, leukemia cell lines and primary leukemia cells were efficiently lysed by culture-expanded iNKT cells. Importantly, culture-expanded donor iNKT cells promoted robust antileukemia activity against HLA-matched allogeneic patient leukemia cells. Our data indicate that the adoptive transfer of culture-expanded iNKT cells could be a powerful cytotherapeutic approach to induce immune tolerance and prevent leukemia relapse after allogeneic HCT in humans.</p