CCAAT/Enhancer Binding Protein Homologous Protein-Dependent Death Receptor 5 Induction and Ubiquitin/Proteasome-Mediated Cellular FLICE-Inhibitory Protein Down-Regulation Contribute to Enhancement of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis by Dimethyl-Celecoxib in Human Non–Small-Cell Lung Cancer Cells

Abstract

2,5-Dimethyl-celecoxib (DMC) is a derivative of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor with anticancer activity in both preclinical studies and clinical practice, and lacks COX-2-inhibitory activity. Several preclinical studies have demonstrated that DMC has better apoptosis-inducing activity than celecoxib, albeit with undefined mechanisms, and exhibits anticancer activity in animal models. In this study, we primarily investigated DMC's cooperative effect with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on the induction of apoptosis and the underlying mechanisms in human nonsmall-cell lung cancer (NSCLC) cells. We found that DMC was more potent than celecoxib in decreasing the survival and inducing apoptosis of NSCLC cells. When combined with TRAIL, DMC exerted enhanced or synergistic effects on the induction of apoptosis, indicating that DMC cooperates with TRAIL to augment the induction of apoptosis. To determine the underlying mechanism of the synergy between DMC and TRAIL, we have demonstrated that DMC induces a CCAAT/ enhancer binding protein homologous protein-dependent expression of DR5, a major TRAIL receptor, and reduces the levels of cellular FLICE-inhibitory protein (c-FLIP) (both the long and short forms), key inhibitors of death receptor-mediated apoptosis, by facilitating c-FLIP degradation through a ubiquitin/proteasome-dependent mechanism. It is noteworthy that enforced expression of c-FLIP or silencing of DR5 expression using DR5 small interfering RNA abrogated the enhanced effects on induction of apoptosis by the combination of DMC and TRAIL, indicating that both DR5 up-regulation and c-FLIP reduction contribute to cooperative induction of apoptosis by the combination of DMC and TRAIL. Together, we conclude that DMC sensitizes human NSCLC cells to TRAIL-induced apoptosis via induction of DR5 and down-regulation of c-FLIP.

Inhibition of Yin Yang 1-Dependent Repressor Activity of DR5 Transcription and Expression by the Novel Proteasome Inhibitor NPI-0052 Contributes to its TRAIL-Enhanced Apoptosis in Cancer Cells

“…There are several reports indicating a synergistic apoptotic response achieved by the combination of TRAIL with chemotherapeutic drugs (13,14). Increased apoptotic rates in a variety of cancer cell lines have also been reported after the combination of TRAIL with proteasome inhibitors resulting by augmentation of DR5 protein levels (15)(16)(17)(18)(19)(20)(21)(22)(23). Although the role of DR5 up-regulation and involvement in TRAIL-induced sensitization to apoptosis by proteasome inhibitors is well documented, the mechanism by which DR5 is up-regulated is not known and is the subject of the present investigation.…”

Cisplatin Induces p53-Dependent FLICE-Like Inhibitory Protein Ubiquitination in Ovarian Cancer Cells

“…9). Although FLIP ubiquitination has been detected in several cell subtypes (16)(17)(18), the precise mechanism underlying FLIP ubiquitination was not determined. In the present study, we show for the first time that Itch binds to FLIP S and FLIP L to facilitate FLIP ubiquitination in a time-dependent manner.…”

3,3′-diindolylmethane potentiates tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis of gastric cancer cells

“…For example, specific agents, such as dimethyl-celecoxib and 5,7-dimethoxyflavone, have been shown to induce the expression of DR5 via CHOP-dependent DR5 gene transactivation (18,19). Furthermore, previous studies have identified a close association between DR5 expression and ER stress (10,17).…”