Nicotinamide (NAM) Modulates Transcriptional Signature of Ex Vivo Cultured UCB CD34+ Cells (Omidubicel) and Preserves Their Stemness and Engraftment Potential

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.3718-3718
• Main Authors: Lodie, Tracey, Adams, Julian, Yackoubov, Dima, Steinhardt, Yair, Ashengrau, Dorit, Bitansky, Adi, Maliutina, Alina, Cohen, Sherry, Buhenvald, Boaz, Shahor, Moshe, Dinowitz, Nathan, Caspi, Vered, Peled, Amnon, Peled, Tony
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-131124

Historical efforts at expansion of umbilical cord blood (UCB) derived CD34+ hematopoietic stem cells (HSCs) ex vivo with cytokines yielded large numbers of progenitors for transplantation but impaired their long-term engraftment ability. We used nicotinamide (NAM), an allosteric inhibitor of NAD-enzymes, to create omidubicel, an investigational cell therapy designed to improve the expansion of CD34+ HSCs for bone marrow transplant. A Phase 1/2 clinical study of omidubicel in patients with high-risk hematologic malignancies showed rapid neutrophil engraftment and a more favorable immune reconstitution profile in patients compared to historical controls.1 We hypothesized that NAM treatment maintains the stemness and engraftment potential of omidubicel, which is associated with clinical benefit.2 We performed transcriptome, transcription factor (TF), and pathway analysis by next generation sequencing (NGS) to discern the mechanism of action of NAM and to elucidate the pathways leading to the preservation of engraftment after ex vivo expansion of omidubicel compared to CD34+ cells grown in the absence of NAM. Transcriptome analysis revealed that treatment of CD34+ cells with cytokines alone (stem cell factor [SCF], thrombopoietin [TPO], IL-6, and FLT3 ligand) led to an increase in pathways responsible for cell proliferation and differentiation, apoptotic stress, and production of reactive oxygen species (ROS), and matrix metalloproteinases (MMPs), all of which were attenuated by NAM. TF enrichment analysis of NAM-upregulated genes and downregulated genes demonstrated that NAM modulated several TFs critically involved in pathways of HSC cell self-renewal, differentiation, apoptosis and migration. Specifically, NF-kB, C-Jun, LXR/RXR and PPARα/RXRα, and AMPK-mTor signaling were all reduced in NAM-treated CD34+ cells compared to controls. Reduced expression of key genes involved in the production of ROS and reactive nitrogen species (RNS) including NADPH-oxidase-related genes (CYBB, NCF2 and NCF4) and iNOS, suggested that NAM-expanded CD34+ cells were less exposed to oxygen and nitrogen free radical stress than controls. NAM also downregulated the expression of several matrix metalloproteinases (MMP) genes including MMP7, MMP9, MMP12 and MMP19. NAM-induced downregulation of MMPs may explain the increase in engraftment in patients receiving omidubicel. Pathway analysis of differentially expressed (DE) genes was conducted using ingenuity (IPA) software. IPA analysis