Role of HER-2/neu signaling in sensitivity to tumor necrosis factor-related apoptosis-inducing ligand: enhancement of TRAIL-mediated apoptosis by amiloride.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in numerous transformed cell lines but not in most normal cells. Although this selectivity offers a potential therapeutic application in cancer, not all cancers are sensitive to TRAIL-mediated apoptosis. In this study, we observed that amiloride, a current clinically used diuretic drug, which had little or no cytotoxicity, sensitized TRAIL-resistant human prostate adenocarcinoma LNCaP and human ovarian adenocarcinoma SK-OV-3 cells. The TRAIL-mediated activation of caspase, and PARP cleavage, were promoted in the presence of amiloride. Western blot analysis showed that combined treatment with TRAIL and amiloride did not change the levels of TRAIL receptors (DR4, DR5, and DcR2) and anti-apoptotic proteins (FLIP, IAP, and Bcl-2). However, amiloride dephosphorylated HER-2/neu tyrosine kinase as well as Akt, an anti-apoptotic protein. Interestingly, amiloride also dephosphorylated PI3K and PDK-1 kinases along with PP1alpha phosphatase. In vitro kinase assay revealed that amiloride inhibited phosphorylation of kinase as well as phosphatase by competing with ATP. Taken together, the present studies suggest that amiloride enhances TRAIL-induced cytotoxicity by inhibiting phosphorylation of the HER-2/neu-PI3K-Akt pathway-associated kinases and phosphatase.
Kim
Ki M
KM
Department of Surgery and Pharmacology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
Lee
Yong J
YJ
D000584:Amiloride / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology*; D045744:Cell Line, Tumor; D006801:Humans; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000584:Amiloride; D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D010744:Phosphoric Monoester Hydrolases; D018719:Erb-b2 Receptor Tyrosine Kinases; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha; C505653:TNFSF10 protein, human