5-Aminoimidazole-4-carboxamide riboside sensitizes TRAIL- and TNFα-induced cytotoxicity in colon cancer cells through AMP-activated protein kinase signaling

Abstract

Death receptor-mediated tumor cell death, either alone or in combination with other anticancer drugs, is considered as a new strategy for anticancer therapy. In this study, we have investigated the effects and molecular mechanisms of 5-aminoimidazole-4-carboxamide riboside [AICAR; a pharmacologic activator of AMP-activated protein kinase (AMPK)] in sensitizing tumor necrosis factor (TNF) -related apoptosis-inducing ligand (TRAIL) -and TNFA-induced apoptosis of human colon cancer HCT116 cells. The cytotoxic action of AICAR requires AMPK activation and may occur at various stages of apoptotic pathways. AICAR cotreatment with either TRAIL or TNFA enhances activities of caspase-8, caspase-9, and caspase-3; down-regulates the antiapoptotic protein Bcl-2; increases the cleavage of Bid and results in the decrease of mitochondrial membrane potential; potentiates activation of p38 and c-Jun NH 2 -terminal kinase; and inhibits nuclear factor-KB activity. In addition, this sensitized cell apoptosis was neither observed in p53-null HCT116 cells nor affected by the cotreatment with mevalonate. In summary, we have developed a novel strategy of combining AICAR with TRAIL for the treatment of colon cancer cells. The sensitization effect of AICAR in cell apoptosis was mediated through AMPK pathway, requires p53 activity, and involves mitochondria-dependent apoptotic cascades, p38 and c-Jun NH 2 -terminal kinase. [Mol Cancer Ther 2007;6(5):1562 -71]

AMPK-independent down-regulation of cFLIP and sensitization to TRAIL-induced apoptosis by AMPK activators

“…Furthermore, AICAR treatment of a colon cancer cell line has been reported to sensitize these cells to TNF-alpha or TRAIL-induced apoptosis [21]. In our study, we demonstrate that pre-treatment of human breast cancer cells with AMPK activators promotes the activation by TRAIL of a caspase-dependent mechanism of apoptosis in these cells.…”

“…Specifically, AMPK has been proposed to have a pro-apoptotic effect in A c c e p t e d M a n u s c r i p t 5 different tumor cells. Moreover, its activation by AICAR has been shown to sensitize human colon adenocarcinoma cells to TRAIL and TNF-induced apoptosis [21]. Against these data, AMPK has been proposed as an anti-apoptotic molecule to protect cells from ischemia, hyperglycemia, glucose deprivation, fatty acids and ceramide [22][23][24] .…”

15-deoxy-Δ12,14-prostaglandin J2 up-regulates death receptor 5 gene expression in HCT116 cells: involvement of reactive oxygen species and C/EBP homologous transcription factor gene transcription

“…Measurement of Cell Viability by the 3-(4,5-Dimethylthiazol-2-yl)2,5-Diphenyltetrazolium Bromide Assay Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) assay as we described previously (25). The net absorbance (A 550-630 ) indicates the enzymatic activity of mitochondria and implies cell viability.…”

“…Immunoblotting Analysis After stimulation, cell lysates were harvested as described previously (25), and equal amounts of the soluble protein, as determined by the Bradford protein assay, were denatured, subjected to SDS-PAGE, and transferred to nitrocellulose membranes. Proteins were then detected by specific antibodies followed by chemiluminescence detection reagent (Amersham Biosciences).…”

“…Cells were seeded into 24-well plates overnight before transfection with 0.1 Ag plasmid using the Lipofect-AMINE 2000 reagent (Invitrogen). Twenty-four hours later, cells were treated with 15dPGJ 2 for another 24 h, and luciferase activity was determined as we described previously (25) 2 were added for 2 h, and the fluorescence intensity was determined with excitation and emission wavelengths at 488 and 530 nm, respectively, in a flow cytometer at room temperature. Acquisition and analysis were done with FACScan.…”