Abstract 5479: Glycogen synthase kinase-3 (GSK3) differently targets in MLL leukemia cells

Abstract

Abstract Propose: We evaluated the anti-leukemic effect of GSK3 inhibitor for specific type of MLL-tranlocated cell line. Materials and methods: l GSK3 inhibitor: LiCl, SB216763, GSK3-IX l Cell line: MV4-11 [human lymphoblast, t(4:11)] MOLM-13 [human acute myeloid leukemia, ins(9:11)(q23;p22p23)] l Cell proliferation assay: XTT assay, Clonogenic assay l GSK3i activity & detection of histone acetylation and H3K4 methylation: Immunoblotting Summary: MLL gene encodes an enzyme which methylates histone H3 DNA-binding protein and positively regulates the expression of target genes in normal tissue. MLL rearrangement which is found in acute myeloid leukemia (AML), especially therapy-related AML, encodes fusion proteins that have lost H3 lys4-specific (H3K4) methyltransferase activity, and causes a transformation of hematopoietic cells into leukemia stem cells. GSK3, a serine/threonine kinase, plays a key role in glycogen metabolism and is constitutively expressed in resting cell. Although it has been thought that the inhibition of GSK3 causes apoptosis in neurons and other tissues, a paradoxical and unexpected cell death effect of GSK3 inhibition were reported recently in leukemic cell line with MLL translocation, especially t(4;11). Regarding the mechanism of the cytotoxic effect of GSK3 inhibitor, various molecules associated with the signaling pathway around MLL gene have been investigated. Acetylation of H3 peptides stimulates the activity of SET domain in MLL. MLL gene is cleaved at 2 conserved sites by taspase-1; N-terminal 320 kD fragment (N320) and a C-terminal 180 kD fragment (C180). RNA interference-mediated knockdown of taspase-1 resulted in an unprocessed MLL, and finally a loss of proper HOX gene expression. However, the exact mechanism has been still unknown and it remains to be uncertain whether GSK3 inhibitor shows cell death effect on various leukemic cell lines of MLL translocation with other partner gene. We intended to determine whether the inhibition of GSK3 induced cell death in different types of leukemia cell lines with MLL translocation. We examined the apoptotic effects of GSK3 inhibitors on MV4-11 and MOLM-13 cell line. LiCl and GSK3-IX induced cell death, H3K4 methylation and histone acetylation in dose-dependent manners on MV4-11 but did not induce on MOLM-13. However, SB216763 did not induced cell death both cell lines. Conclusion: Cell death effects with the inhibition of GSK3 may be different among leukemic cell line with MLL translocation according to the partner gene of MLL translocation. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5479.