c-Myc inhibition is critical for HSC expansion and Rad51 expression
c-Myc plays a major role in the maintenance of glycolytic metabolism and hematopoietic stem cell (HSC) quiescence. Targeting modulators of HSC quiescence and metabolism could lead to HSC cell cycle entry with concomitant expansion. Here we show that c-Myc inhibitor 10074-G5 treatment leads to 2-fold increase in murine LSKCD34low HSC compartment post 7 days. In addition, c-Myc inhibition increases CD34+ and CD133+ human HSC number. c-Myc inhibition leads to downregulation of glycolytic and cyclin-dependent kinase inhibitor (CDKI) gene expression ex vivo and in vivo. In addition, c-Myc inhibition upregulates major HDR modulator Rad51 expression in hematopoietic cells. Besides, c-Myc inhibition does not alter proliferation kinetics of endothelial cells, fibroblasts or adipose derived mesenchymal stem cells, however; it limits bone marrow derived mesenchymal stem cell proliferation. We further demonstrate that a cocktail of c-Myc inhibitor 10074-G5 along with tauroursodeoxycholic acid (TUDCA) and i-NOS inhibitor L-NIL provides a robust HSC maintenance and expansion ex vivo as evident by induction of all stem cell antigens analyzed. Intriguingly, the cocktail of c-Myc inhibitor 10074-G5, TUDCA and L-NIL improves HDR related gene expression. These findings provide tools to improve ex vivo HSC maintenance and expansion, autologous HSC transplantation and gene editing through modulation of HSC glycolytic and HDR pathways.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC=\"FIGDIR/small/403584_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (65K):\norg.highwire.dtl.DTLVardef@a34597org.highwire.dtl.DTLVardef@12dcc37org.highwire.dtl.DTLVardef@1ba68edorg.highwire.dtl.DTLVardef@13edbfd_HPS_FORMAT_FIGEXP M_FIG Graphical abstract\n\nC_FIG HighlightsO_LIc-Myc inhibition induces ex vivo murine and human hematopoietic stem and progenitor cell proliferation and in vivo murine HSC pool\nC_LIO_LIc-Myc inhibition downregulates CDKIs and glycolytic gene expression in hematopoietic cells\nC_LIO_LIc-Myc inhibition do not cause apparent changes to endothelial cells, fibroblasts, or AD-MSCs but it limits BM-MSC proliferation\nC_LIO_LIc-Myc inhibition along with TUDCA and L-NIL improves HSC maintenance and expansion as evident by induction of all HSC surface antigens analyzed\nC_LIO_LIc-Myc inhibition alone upregulates major HDR modulator Rad51 expression in hematopoietic cells\nC_LIO_LICocktail of c-Myc inhibitor 10074-G5, TUDCA and L-NIL improves HDR and S-phase related gene expression\nC_LI