Effect of HER-2/Neu Signaling on Sensitivity to TRAIL in Prostate Cancer
Abstract
We have previously observed that low extracellular pH (pHe) promotes tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cytotoxicity. In this study, we examined whether amiloride, which is an inhibitor of the Na+/H+ antiport and reduces intracellular pH (pHi), can augment TRAIL-induced apoptotic death. Human prostate adenocarcinoma DU-145 cells were treated with various concentration of TRAIL (10-200 ng/ml) and/or amiloride (0.1-1mM) for 4 h. Amiloride, which had little or no cytotoxicity, enhanced TRAIL-induced apoptosis. 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 antiapoptotic proteins (FLIP, IAP, and Bc1-2). However, unlike low extracellular pH, amiloride dephosphorylated Akt. Interestingly, amiloride also dephosphorylated PI3K and PDK-1 kinases along with PTEN and PP1alpha phosphatases. 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 PI3K-Akt pathway-associated kinases and phosphatases.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2004
- Accession Number
- ADA428425
Entities
People
- Yong J Lee
Organizations
- University of Pittsburgh