title: Glutathione S-transferase M1 inhibits dexamethasone-induced apoptosis in association with the suppression of Bim through dual mechanisms in a lymphoblastic leukemia cell line.
abstract: Glutathione S-transferase mu (GSTM1) is mainly known as a detoxification enzyme but it has also been shown to be a negative regulator of apoptosis-related signaling cascades. Recently GSTM1 has been reported to be a significant risk factor for hematological relapse in childhood acute lymphoblastic leukemia, although the underlying mechanism remains largely unknown. Glucocorticoids play a crucial role in the treatment of childhood acute lymphoblastic leukemia, therefore we hypothesized that GSTM1 plays important roles in glucocorticoid-induced apoptotic pathways. To clarify the relationship between GSTM1 and drug resistance, GSTM1 was transfected into a T-acute lymphoblastic leukemia cell line, CCRF-CEM (CEM), and we established the GSTM1-expressing cell lines CEM/M1-4 and CEM/M1-9. Transduction of GSTM1 into CEM selectively decreased cellular sensitivity to dexamethasone in a manner that was independent of glutathione conjugation, but was due to apoptosis inhibition. Dexamethasone-induced p38-MAPK and Bim activation were concomitantly suppressed. Interestingly, nuclear factor kappa b (NF-kappaB) p50 activity was upregulated in GSTM1-expressing CEM. Inhibition of NF-kappaB by the pharmacological agent BAY11-7082 greatly enhanced the sensitivity of the GSTM1-expressing CEM to dexamethasone and was accompanied by an increase in Bim expression. Thus, we propose that GSTM1, a novel regulator of dexamethasone-induced apoptosis, causes dexamethasone resistance by suppression of Bim through dual mechanisms of both downregulation of p38-MAPK and upregulation of NF-kappaB p50.
authors.affiliation: First Department of Internal Medicine, University of Fukui, Matsuoka, Eiheiji, Fukui, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Hosono
authors.forename: Shinji
authors.initials: S
authors.lastname: Kishi
authors.forename: Sumiko
authors.initials: S
authors.lastname: Iho
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Urasaki
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshida
authors.forename: Hisanori
authors.initials: H
authors.lastname: Kurooka
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Yokota
authors.forename: Takanori
authors.initials: T
authors.lastname: Ueda
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors*; D000072224:Bcl-2-Like Protein 11; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D045744:Cell Line, Tumor; D003907:Dexamethasone / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005982:Glutathione Transferase / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors*; D052002:NF-kappa B p50 Subunit / Q000502:physiology; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D019328:Buthionine Sulfoximine; D003907:Dexamethasone; D005982:Glutathione Transferase; D008565:Membrane Proteins; D052002:NF-kappa B p50 Subunit; D011518:Proto-Oncogene Proteins; D048051:p38 Mitogen-Activated Protein Kinases; C000606775:BCL2L11 protein, human