Glycogen Synthase Kinase-3β Inhibition Preserves Hematopoietic Stem Cell Activity and Inhibits Leukemic Cell Growth

Abstract

Abstract Ex vivo expansion of cord blood cells generally results in reduced stem cell activity in vivo. Glycogen synthase kinase-3β (GSK-3β) regulates the degradation of β-catenin, a critical regulator of hematopoietic stem cells (HSCs). Here we show that GSK-3β inhibition activates β-catenin in cord blood CD34+ cells and upregulates β-catenin transcriptional targets c-myc and HoxB4, both known to regulate HSC self-renewal. GSK-3β inhibition resulted in delayed ex vivo expansion of CD34+ cells, yet enhanced the preservation of stem cell activity as tested in long-term culture with bone marrow stroma. Delayed cell cycling, reduced apoptosis, and increased adherence of hematopoietic progenitor cells to bone marrow stroma were observed in these long-term cultures treated with GSK-3β inhibitor. This improved adherence to stroma was mediated via upregulation of CXCR4. In addition, GSK-3β inhibition preserved severe combined immunodeficiency (SCID) repopulating cells as tested in the nonobese diabetic/SCID mouse model. Our data suggest the involvement of GSK-3β inhibition in the preservation of HSC and their interaction with the bone marrow environment. Methods for the inhibition of GSK-3β may be developed for clinical ex vivo expansion of HSC for transplantation. In addition, GSK-3β inhibition suppressed leukemic cell growth via the induction of apoptosis mediated by the downregulation of survivin. Modulators of GSK-3β may increase the range of novel drugs that specifically kill leukemic cells while sparing normal stem cells. Disclosure of potential conflicts of interest is found at the end of this article.