title: Constitutive levels of cAMP-dependent protein kinase activity determine sensitivity of human multidrug-resistant leukaemic cell lines to growth inhibition and apoptosis by forskolin and tumour necrosis factor alpha.
abstract: The cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) signal pathway regulates cell proliferation, differentiation and cell death. It may also regulate the multidrug resistance (MDR) phenotype in leukaemic cells. These data showed that MDR1+ K/Dau600 cells exhibited a higher basal level of PKA activity than MDR- parental cells. The significance of this on tumour necrosis factor alpha (TNFalpha)-induced apoptosis and cytostasis was investigated further. In comparison with MDR1- parental cells, K/Dau600 cells had a higher expression of PKA regulatory subunit RIalpha and nuclear catalytic subunit PKAcalpha. They were also more susceptible to inhibition of proliferation and induction of apoptosis by TNFalpha and/or forskolin, but this could be attenuated by H89. An increase in cAMP was associated with the apoptosis in the K/Dau600 cell line. Forskolin inactivated NF-kappaB in K/Dau600 cells but not in K562 cl. 6 cells, whereas TNF activated NF-kappaB in K562 cl.6 cells but not in K/Dau600 cells. 8-Cl-cAMP exhibited similar inhibitory effects on the proliferation of all of the cell lines used via its metabolite 8-Cl-adenosine, which indicates that these effects were independent of residual PKA or cAMP. Therefore, the differential sensitivity to apoptosis and/or growth inhibition could be mediated via cAMP, partly through PKA via NF-kappaB and partly by PKA-independent pathways.
authors.affiliation: Department of Haematology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD, UK.
authors.forename: Y
authors.initials: Y
authors.lastname: Yin
authors.forename: P D
authors.initials: PD
authors.lastname: Allen
authors.forename: L
authors.initials: L
authors.lastname: Jia
authors.forename: M G
authors.initials: MG
authors.lastname: MacEy
authors.forename: S M
authors.initials: SM
authors.lastname: Kelsey
authors.forename: A C
authors.initials: AC
authors.lastname: Newland
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D005576:Colforsin / Q000627:therapeutic use*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D007938:Leukemia / Q000188:drug therapy / Q000201:enzymology* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D013449:Sulfonamides; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000627:therapeutic use
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D016328:NF-kappa B; D013449:Sulfonamides; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C044258:8-chloro-cyclic adenosine monophosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide