title: Phosphatidylinositol-3 kinase inhibitors reproduce the selective antiproliferative effects of imatinib on chronic myeloid leukaemia progenitor cells.
abstract: We investigated the role of the phosphatidylinositol-3 kinase (PI-3K) pathway in regulating the proliferation of primary chronic myeloid leukaemia (CML) progenitor cells by using imatinib to inhibit the activity of p210(Bcr-Abl). The effect of imatinib on the expression of PI-3K pathway proteins was investigated by kinase assays and Western blotting; PI-3K was inhibited by wortmannin or LY294002, Jak2 by AG490 and farnesylation by FTI II; progenitor cell proliferation (self-renewal) was measured by growing myeloid colonies in vitro, then replating them to observe secondary colony formation. Suppression of p210(Bcr-Abl) with imatinib indirectly suppressed the activity of PI-3K and its downstream targets (Erk, Akt and p70S6 kinase), thereby implicating the PI-3K pathway in p210(Bcr-Abl)-mediated signalling in primary CML progenitor cells. The PI-3K inhibitors, wortmannin and LY294002 reproduced the differential effects of imatinib on normal and CML progenitor cell proliferation in vitro by increasing normal cell (P = 0.001) and reducing CML cell proliferation (P = 0.0003). This differential effect was attributable to dysregulated signalling by granulocyte colony-stimulating factor in CML. The responses of individual patient's cells to wortmannin correlated with their responses to imatinib (P = 0.004) but not their responses to AG490 (Jak2 kinase inhibitor) or FTI II (farnesyltransferase inhibitor). Individual responses to wortmannin also correlated with responses to interferon alpha (IFNalpha) (P = 0.016). Imatinib-resistant K562 cells were sensitive to LY294002. Inhibition of the PI-3K pathway may be common to imatinib and IFNalpha and reflect dysregulated cytokine signalling. As imatinib-resistant cells remained sensitive to wortmannin and LY294002, targeting the PI-3K pathway may provide an alternative therapy for imatinib-resistant patients.
authors.affiliation: Department of Haematology, Imperial College Faculty of Medicine, London, UK.
authors.forename: S B
authors.initials: SB
authors.lastname: Marley
authors.forename: J L
authors.initials: JL
authors.lastname: Lewis
authors.forename: H
authors.initials: H
authors.lastname: Schneider
authors.forename: C E
authors.initials: CE
authors.lastname: Rudd
authors.forename: M Y
authors.initials: MY
authors.lastname: Gordon
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors; D000730:Androstadienes / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides; D015153:Blotting, Western / Q000379:methods; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002867:Chromones / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D051231:Farnesyltranstransferase; D006801:Humans; D000068877:Imatinib Mesylate; D007371:Interferon-gamma / Q000627:therapeutic use; D053614:Janus Kinase 2; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000201:enzymology / Q000276:immunology; D009025:Morpholines / Q000627:therapeutic use; D019869:Phosphatidylinositol 3-Kinases / Q000032:analysis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010879:Piperazines / Q000627:therapeutic use*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines / Q000627:therapeutic use*; D015398:Signal Transduction / Q000187:drug effects*; D013234:Stem Cells / Q000187:drug effects; D020032:Tyrphostins / Q000627:therapeutic use; D000077191:Wortmannin
chemical_list: D019883:Alkyl and Aryl Transferases; D000730:Androstadienes; D000970:Antineoplastic Agents; D001549:Benzamides; D002867:Chromones; D051231:Farnesyltranstransferase; D000068877:Imatinib Mesylate; D007371:Interferon-gamma; D053614:Janus Kinase 2; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010879:Piperazines; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D020032:Tyrphostins; D000077191:Wortmannin; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C507924:JAK2 protein, human