title: Amiloride potentiates TRAIL-induced tumor cell apoptosis by intracellular acidification-dependent Akt inactivation.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor gene family, is considered as one of the most promising cancer therapeutic agents due to its ability to selectively induce tumor cell apoptosis. In this study, we investigated whether the Na(+)/H(+) exchanger inhibitor, amiloride, promotes TRAIL-induced apoptotic death both in sensitive and resistant tumor cells, HeLa and LNCaP cells, respectively, and its underlying molecular mechanism. Amiloride enhanced TRAIL-induced apoptosis and activation of caspase-3 and -8 in both cells. This compound increased TRAIL-induced mitochondrial cytochrome c release and poly(ADP-ribose) polymerase cleavage. Moreover, amiloride-induced intracellular acidification, and inhibited the phosphorylated activation of the serine/threonine kinase Akt, which is known to promote cell survival, in both tumor cells. These data suggest that amiloride sensitizes both tumor cells to TRAIL-induced apoptosis by promoting Akt dephosphorylation and caspase-8 activation via the intracellular acidification and that Na(+)/H(+) exchanger inhibitors may play an important role in the anti-cancer activity of TRAIL, especially, in TRAIL-resistant tumors with highly active and expressed Akt.
authors.affiliation: Vascular System Research Center, Kangwon National University, Chunchon, Kangwon-do, Republic of Korea.
authors.forename: Young-Lai
authors.initials: YL
authors.lastname: Cho
authors.forename: Kwang-Soon
authors.initials: KS
authors.lastname: Lee
authors.forename: Seon-Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Seung
authors.initials: S
authors.lastname: Namkoong
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Hansoo
authors.initials: H
authors.lastname: Lee
authors.forename: Kwon-Soo
authors.initials: KS
authors.lastname: Ha
authors.forename: Jeong-A
authors.initials: JA
authors.lastname: Han
authors.forename: Young-Guen
authors.initials: YG
authors.lastname: Kwon
authors.forename: Young-Myeong
authors.initials: YM
authors.lastname: Kim
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000737:chemistry* / Q000187:drug effects; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000737:chemistry / Q000201:enzymology* / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D000584:Amiloride; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt