ABSTRACT
Due to the high prevalence and mortality rate of colorectal cancer (CRC), new treatment approaches like combination therapy seem to be necessary. The relationship between chronic inflammation and colorectal cancer development and progression has been shown to be important. Celecoxib, a selective COX-2 inhibitor, is the only non-steroidal anti-inflammatory drug (NSAID) that has been approved for cancer therapy and prevention. Because of cardiovascular side effects of COX-2 inhibitors, combination therapy may improve the therapeutic profile. 17-Demethoxy-17-allylamino geldanamycin (17-AAG), a heat shock protein 90 (HSP90) inhibitor, shows anti-inflammatory effects via down-regulation of the key mediators of inflammation such as Nuclear Factor κB (NF-kB), JAK/Signal Transducer and Activator of Transcription (JAK/STAT). Thus, we studied the effect(s) of combination of 17-AAG and celecoxib on HT-29 cells viability and apoptosis induction. Based on MTT results, we showed an increase in the inhibitory effect of celecoxib when combined with 17-AAG, especially at low a concentration of celecoxib. Flow cytometry analysis demonstrated that apoptosis induction is probably the mechanism of additive inhibitory effects of 17-AAG and celecoxib combination. To explore the possible mechanism of apoptosis induction by 17-AAG and celecoxib combination, levels of BAX and BCL-2 proteins were determined by western blotting. The BAX/BCL-2 ratio in the combination group was increased compared to 17-AAG or celecoxib alone, mainly via decreasing BCL-2 levels. In conclusion, 17-AAG, increased inhibitory effects of celecoxib on HT-29 cells, probably by induction of apoptosis.
Subject(s)
Apoptosis/drug effects , Benzoquinones/pharmacology , Celecoxib/pharmacology , Cell Proliferation/drug effects , HSP90 Heat-Shock Proteins/antagonists & inhibitors , Lactams, Macrocyclic/pharmacology , Proto-Oncogene Proteins c-bcl-2/metabolism , bcl-2-Associated X Protein/metabolism , Blotting, Western , Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/pathology , Cyclooxygenase 2 Inhibitors/pharmacology , Flow Cytometry , HSP90 Heat-Shock Proteins/metabolism , HT29 Cells , Humans , Proto-Oncogene Proteins c-bcl-2/genetics , bcl-2-Associated X Protein/geneticsABSTRACT
The existence of multiple-interactive roles between several signaling pathways in tumorigenesis shows the significance of pharmacological factors like heat shock protein 90 (HSP90) inhibitors which control several signaling pathways simultaneously. HSP90 as a molecular chaperone supports the active conformational structure and function of several oncogenic signal proteins, termed "client" proteins, some of them act as a link between cancer and inflammation. Prostaglandin E2 (PGE2) is one of the major mediators of inflammation in colorectal cancer development and progress. However, the relationship between chaperone activity of HSP90 and PGE2 levels remains unclear. We evaluated the inhibitory effects of 17-demethoxy-17-allylamino geldanamycin (1 7-AAG), an HSP90 inhibitor, on PGE2 levels in HT-29 colorectal cancer cells. For the first time, we showed inhibitory effects of 17-AAG, on PGE2 levels in HT-29 colorectal cancer cells. 17-AAG inhibited PMA-induced cyclooxygenase-2 (COX-2) mRNA expression and protein level. We showed 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression induced by 17-AAG treatment at both mRNA and protein levels. In conclusion, we found that inhibitory effects of 17-AAG on PGE2 levels in HT-29 colorectal cancer cells were mediated through modulating COX-2 and 15-PGDH expression.
