title: Sensitisation of HL60 human leukaemic cells to cytotoxic drug-induced apoptosis by inhibition of PI3-kinase survival signals.
abstract: Drug resistance remains a serious limiting factor in the treatment of acute myeloid leukaemia (AML) either at initial presentation or following primary or subsequent relapses. Using specific kinase inhibitors, this study has investigated the contribution of the Ras/PI3-kinase regulated survival pathways to drug resistance and suppression of apoptosis in a cell line derived from AML (HL60). Inhibition of the Raf/MAP-kinase (ERK) pathway with a specific MAP-kinase inhibitor, apigenin did not sensitise HL60 cells to drug-induced apoptosis, indicating a lack of involvement in chemoresistance. In contrast, the PI3-kinase inhibitors, LY294002 and wortmannin, did induce a significant increase in apoptosis in combination with cytotoxic drugs. The contribution of downstream mediators of PI3-kinase, p70S6-kinase and PKB/Akt were then investigated. While inhibition of p70S6-kinase with rapamycin did not increase drug-induced apoptosis, PI3-kinase inhibition resulted in notable dephosphorylation of PKB, suggesting that the PI3-kinase/PKB survival pathway may play a major role in chemoresistance in AML. This pathway has been reported to mediate heterodimer interactions with the proapoptotic regulator, Bad. In contrast to previous studies, we found no evidence of Bad binding to anti-apoptotic Bcl-2, Bcl-XL or McI-1, or of alterations in Bax heterodimers. This suggests that alternative targets of PI3-kinase/PKB, distinct from the Bcl-2 family may be responsible for contributing to survival factor-mediated drug resistance in AML.
authors.affiliation: Department of Biochemistry, University College Cork, Ireland, UK.
authors.forename: D M
authors.initials: DM
authors.lastname: O'Gorman
authors.forename: S L
authors.initials: SL
authors.lastname: McKenna
authors.forename: A J
authors.initials: AJ
authors.lastname: McGahon
authors.forename: K A
authors.initials: KA
authors.lastname: Knox
authors.forename: T G
authors.initials: TG
authors.lastname: Cotter
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D047310:Apigenin; D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D019281:Dimerization; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005047:Etoposide / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D019254:Genes, bcl-2; D018922:HL-60 Cells / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D008942:Mitoxantrone / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D000077191:Wortmannin; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
chemical_list: D000730:Androstadienes; D000970:Antineoplastic Agents; C494819:BAD protein, human; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009025:Morpholines; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D003609:Dactinomycin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D005047:Etoposide; D047310:Apigenin; D004317:Doxorubicin; D003513:Cycloheximide; D008942:Mitoxantrone; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020123:Sirolimus; D002166:Camptothecin; D000077191:Wortmannin