3141 – BONE MARROW STROMAL CELLS ACTIVATE CREB1-MCL1 AXIS TO PROTECT HUMAN HEMATOPOIETIC STEM CELLS FROM DNA DAMAGE INDUCED APOPTOSIS

• Published in: Experimental hematology 2022, Vol.111, p.S115-S115
• Main Authors: Muddineni, Siva Sai Naga Anurag, Even, Chen Katz, Roitman, Adi Zipin, Milyavsky, Michael
• Format: Article
• Language: English
• ISSN: 0301-472X; 1873-2399
• DOI: 10.1016/j.exphem.2022.07.197

Anti-cancer treatments, such as chemo/radio-therapies suppress normal Hematopoietic Stem and Progenitor Cell (HSPCs) function and present an inherent risk of developing bone marrow failure and secondary leukemia. Mesenchymal Stromal Cells (MSCs) are a key component of the bone marrow (BM) microenvironment, but their direct role in human HSPC response to genotoxic stress is not clear. Here, we utilized a flexible co-culture system that mimics the physiological BM microenvironment and demonstrate that irradiated human HSPCs co-cultured with MSCs underwent significantly less apoptosis and preserved their LTC-IC ability. To delineate molecular networks mediating pro-survival signaling upon HSPC-MSC interaction, we performed proteomic and transcriptomic profiling of purified human HSPCs. We observed significant downregulation of pro-survival MCL1 protein levels in HSPCs upon irradiation, which is prevented upon co-culture with MSCs. Our RNA-seq analysis has revealed enrichment of cAMP Responsive Element Binding Protein 1 (CREB1) target genes in HSPCs co-cultured with MSCs. Functional studies utilizing MCL-1 inhibitor (S63845), CREB signaling activator (Forskolin), and measuring P-CREB levels revealed that MSCs modulate the CREB signaling pathway in HSPCs to prevent MCL-1 decline and apoptosis onset upon irradiation. The contribution of CREB signaling pathway to HSPCs survival in vivo is currently being studied using humanized mouse models. Collectively, our HSPC-MSC niche model provides a framework to systematically discern mechanisms involved in the crosstalk between these two essential cell types and revealed novel pharmacological agents that can mitigate radiation-induced hematological sequelae.