Combination of Fludarabine and Imatinib Induces Apoptosis Synergistically Through Loss of Mitochondrial Membrane Potential and Increases in Caspase-3 Enzyme Activity in Human K562 Chronic Myleloid Leukemia Cells

Anti-proliferative benefit of curcumol on human bladder cancer cells via inactivating EZH2 effector

We investigated the molecular mechanism of curcumol-induced apoptosis in bladder cancer cells. The mitochondrial membrane potential was measured using JC-1 staining. ROS generation of bladder cancer cells was determined using the DCFH staining method. The apoptosis of bladder cancer cells was examined using the Annexin V-FITC and PI double-staining method. Enforced expression of EZH2 in bladder cancer cells was accomplished by transfecting an EZH2 expression plasmidinto EJ and T24 cells. siRNAs targeting EZH2 were used to inhibit endogenous expression of EZH2. Curcumol dose-dependently inhibited proliferation and colony formation and induced apoptosis in EJ and T24 bladder cancer cells. These effects correlated with decreased accumulation of EZH2. In addition, suppression of EZH2 enhanced the inhibitory effects of curcumol on cell growth and colony formation and increased curcumol-induced apoptosis. Conversely, enforced expression of EZH2 ameliorated the inhibitory effects of curcumol on cell growth and colony formation and decreased curcumol-induced apoptosis in EJ and T24 cells. We also found that suppression of EZH2 induced ROS generation and MMP loss in both EJ and T24 cells. Conversely, up-regulation of EZH2 suppressed ROS generation and MMP loss. Our data indicate that curcumol inhibits proliferation and induces apoptosis by targeting EZH2 and modulating the mitochondrial apoptosis pathway.

Imatinib and its combination with 2,5-dimethyl-celecoxibinduces apoptosis of human HT-29 colorectal cancer cells

Mono-targeting by imatinib as a main antitumor agent does not always accomplish complete cancer suppression. 2,5-dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor, celecoxib, that lacks COX-2 inhibitory function. In this study, we aimed to show the apoptotic effects of imatinib in combination with DMC in human HT-29 colorectal cancer (CRC) cells. HT-29 CRC cells were treated with IC₅₀ dose of imatinib (6.60 μM), DMC (23.45 μM), and their combination (half dose of IC₅₀) for 24 h. The caspase-3 activity was estimated with colorimetric kit. The caspase-3 gene expression was evaluated by real-time PCR method. There was a significant up-regulation in caspase-3 enzyme activity and caspase-3 expression by imatinib and its half dose combination with DMC as compared to control. As a summary, the results of this study strongly suggest that half dose combination of imatinib with DMC induced apoptosis as potent as full dose imatinib in human HT-29 CRC cells, while minimizing undesired side effects related to imatinib mono-therapy. This study also pointed towards possible caspase-dependent actions of imatinib and DMC.

Cryptotanshinone acts synergistically with imatinib to induce apoptosis of human chronic myeloid leukemia cells

Imatinib resistance has emerged as a significant clinical problem in chronic myeloid leukemia (CML) treatment. In this study, we investigated the effect and mechanism of combination treatment with imatinib and cryptotanshinone (CPT) in CML cells. Cotreatment with imatinib and CPT showed a significant synergistic killing effect in both imatinib sensitive and resistant CML cell lines, as well as primary CML cells. Furthermore, combination treatment induced apoptosis significantly, as indicated by increases in apoptotic cell fraction and activities of proapoptotic proteins. Subsequent studies revealed that CPT significantly inhibited Bcr/Abl protein expression, as well as phosphorylation expression levels of signal transducer and activator of transcription 3 (STAT3), mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E (eIF4E), which are critical mediators of Bcr/Abl transformation. Furthermore, CPT in combination with imatinib dramatically decreased the activity of the Bcr/Abl pathway in both K562 and K562-R cells. Our results demonstrated that CPT increased imatinib-induced apoptosis in a Bcr/Abl dependent manner, suggesting a novel strategy for the treatment of CML.