The eIF4E/eIF4G interaction inhibitor 4EGI-1 augments TRAIL-mediated apoptosis through c-FLIP Down-regulation and DR5 induction independent of inhibition of cap-dependent protein translation.
The small molecule 4EGI-1 was identified as an inhibitor of cap-dependent translation initiation owing to its disruption of the eIF4E/eIF4G association through binding to eIF4E. 4EGI-1 exhibits growth-inhibitory and apoptosis-inducing activity in cancer cells; thus, we were interested in its therapeutic efficacy in human lung cancer cells. 4EGI-1, as a single agent, inhibited the growth and induced apoptosis of human lung cancer cells.When combined with the death ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), enhanced apoptosis-induced activity was observed. As expected, 4EGI-1 inhibited eIF4E/eIF4G interaction and reduced the levels of cyclin D1 and hypoxia-inducing factor-1alpha (HIF-1alpha), both of which are regulated by a cap-dependent translation mechanism. Moreover, 4EGI-1 induced CCAAT/enhancer-binding protein homologous protein-dependent DR5 expression and ubiquitin/proteasome- mediated degradation of cellular FLICE-inhibitory protein (c-FLIP). Small interfering RNA-mediated blockade of DR5 induction or enforced expression of c-FLIP abrogated 4EGI-1's ability to enhance TRAIL-induced apoptosis, indicating that both DR5 induction and c-FLIP down-regulation contribute to enhancement of TRAIL-induced apoptosis by 4EGI-1. However, inhibition of eIF4E/eIF4G interaction by knockdown of eIF4E effectively reduced the levels of cyclin D1 and HIF-1alpha but failed to induce DR5 expression, downregulate c-FLIP levels, or augment TRAIL-induced apoptosis. These results collectively suggest that 4EGI-1 augments TRAIL-induced apoptosis through induction of DR5 and down-regulation of c-FLIP, independent of inhibition of cap-dependent protein translation.
Fan
Songqing
S
Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA 30322, USA.
Li
Yikun
Y
Yue
Ping
P
Khuri
Fadlo R
FR
Sun
Shi-Yong
SY
D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics* / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D039561:Eukaryotic Initiation Factor-4E / Q000037:antagonists & inhibitors / Q000378:metabolism; D039603:Eukaryotic Initiation Factor-4G / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D006835:Hydrazones; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009574:Nitro Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects* / Q000235:genetics; D039381:RNA Cap-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000494:pharmacology*; D013844:Thiazoles / Q000008:administration & dosage / Q000494:pharmacology*
C517852:4EGI-1 compound; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D006835:Hydrazones; D009574:Nitro Compounds; D039381:RNA Cap-Binding Proteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D013844:Thiazoles