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Role of HER‐2/neu signaling in sensitivity to tumor necrosis factor‐related apoptosis‐inducing ligand: Enhancement of TRAIL‐mediated apoptosis by amiloride
Author(s) -
Kim Ki M.,
Lee Yong J.
Publication year - 2005
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20512
Subject(s) - amiloride , cancer research , protein kinase b , apoptosis , pi3k/akt/mtor pathway , lncap , kinase , chemistry , phosphorylation , tyrosine kinase , biology , signal transduction , cancer cell , microbiology and biotechnology , biochemistry , cancer , genetics , organic chemistry , sodium
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 PP1α 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. © 2005 Wiley‐Liss, Inc.