[Show abstract][Hide abstract] ABSTRACT: FTY720, Fingolimod, is a functional antagonist to the sphingosine-1-phoaphate (S1P) receptor and an inhibitor of sphingosine kinase 1. Here, we showed that a combination of FTY720 and TRAIL induced apoptosis in human renal, breast, and colon carcinoma cells. Most importantly, this combination had no effect on normal cells. Furthermore, the combined treatment with FTY720 and TRAIL reduced tumor growth in xenograft models. FTY720 up-regulated death receptor (DR)5 at post-translational level. Knockdown of DR5 markedly blocked apoptosis induced by the combined treatment. FTY720 also inhibited Mcl-1 expression at the post-translational level. Over-expression of Mcl-1 blocked apoptosis induced by FTY720 and TRAIL. Interestingly, phospho-FTY720 and inhibitors of sphingosine kinase failed to enhance TRAIL-induced apoptosis. Thus, FTY720 enables TRAIL-induced apoptosis through up-regulation of DR5 and down-regulation of Mcl-1 in human cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Melatonin is involved in many physiological functions and it has differential effects on apoptosis in normal and cancer cells. However, the mechanism of its anti-tumor roles is not well understood. In this study, we show that melatonin enhances tunicamycin-induced apoptosis in human breast carcinoma MDA-MB-231 cells. Melatonin up-regulates pro-apoptotic protein Bim expression at the transcriptional levels in the presence of tunicamycin. Melatonin inhibits tunicamycin-induced COX-2 expression in MDA-MB-231 cells. Furthermore, inhibition of COX-2 activity using the COX-2 inhibitor, NS398, increases tunicamycin-induced apoptosis. Interestingly, these effects were not associated with melatonin receptor signal pathways. Pertussis toxin (a general Gi -protein inhibitor) or luzindole (a non-specific melatonin receptor antagonist) did not reverse the effect of melatonin. In addition, melatonin blocked tunicamycin-induced NF-κB transcriptional activity, p65 nuclear translocation and p38 MAPK activation. Melatonin-mediated p38 MAPK inhibition contributed to decreased COX-2 mRNA stability. Taken together, our results suggest that melatonin enhances anti-tumor function through up-regulation of Bim expression and down-regulation of COX-2 expression in tunicamycin-treated MDA-MB-231 cells. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Journal of Pineal Research 02/2015; 58(3). DOI:10.1111/jpi.12217 · 7.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ABT-737, a BH3-mimetic small-molecule inhibitor, binds with very high affinity to Bcl-2, Bcl-xL and Bcl-w, and inhibits their activity. Aurora kinase is one of the serine/threonine kinase family members and is a vital and critical regulator of mitosis and meiosis. In the present study, we investigated the effects and mechanisms of a combined treatment of ABT-737 and VX-680 (Aurora kinase inhibitor) in human breast cancer MDA-MB‑435S cells. ABT-737 plus VX-680 induced caspase-dependent apoptosis in the human breast cancer cells. Combined treatment with ABT-737 and VX-680 led to the downregulation of Bcl-2 expression at the transcriptional level and the downregulation of c-FLIP and Mcl-1 expression at the post-transcriptional level. Overexpression of Bcl-2 or c-FLIP could not block the induction of apoptosis caused by the combined treatment with ABT-737 and VX-680. However, overexpression of Mcl-1 partially inhibited the induction of apoptosis. In contrast, the combined treatment with ABT-737 and VX680 had no effect on the apoptosis in normal cells. Taken together, our study demonstrated that combined treatment with ABT-737 and VX-680 induced apoptosis in anti‑apoptotic protein (Bcl-2 or c-FLIP)-overexpressing cells.
[Show abstract][Hide abstract] ABSTRACT: Withaferin A, a withanolide derived from the medicinal plant Withania somnifera, has been reported to exhibit anti-tumorigenic activity against various cancer cells. In this study, we show that withaferin A inhibits the constitutive and recombinant human growth-arrest-specific protein 6 (rhGas6)-induced phosphorylation of Axl and STAT3. In addition, withaferin A also induces the down-regulation of Axl protein expression in a lysosome-dependent manner and inhibits rhGas6-induced wound healing and cell migration. Furthermore, the overexpression of Axl attenuates withaferin A-induced apoptosis. Taken together, the data from the present study indicate that the withaferin A-mediated down-regulation of the Gas6/Axl signaling pathway mediates the inhibition of cell migration and the induction of apoptosis.
Biochemical and Biophysical Research Communications 08/2014; 451(3). DOI:10.1016/j.bbrc.2014.08.018 · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silibinin, an effective anti-cancer and chemopreventive agent, has been shown to exert multiple effects on cancer cells, including inhibition of both cell proliferation and migration. However, the molecular mechanisms responsible for these effects are not fully understood. We observed that silibinin significantly induced the expression of the non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) in both p53 wild-type and p53-null cancer cell lines, suggesting that silibinin-induced NAG-1 up-regulation is p53-independent manner. Silibinin up-regulates EGR-1 expression. The ectopic expression of EGR-1 significantly increased NAG-1 promoter activity and NAG-1 protein expression in a dose-dependent manner. Furthermore, down-regulation of EGR-1 expression using siRNA markedly reduced silibinin-mediated NAG-1 expression, suggesting that the expression of EGR-1 is critical for silibinin-induced NAG-1 expression. We also observed that reactive oxygen species (ROS) are generated by silibinin; however, ROS did not affect silibinin-induced NAG-1 expression and apoptosis. In addition, we demonstrated that the mitogen-activated protein kinase (MAP kinase) signal transduction pathway is involved in silibinin-induced NAG-1 expression. Inhibitors of p38 MAP kinase (SB203580) attenuated silibinin-induced NAG-1 expression. Furthermore, we found that siRNA-mediated knockdown of NAG-1 attenuated silibinin-induced apoptosis. Collectively, the results of this study demonstrate for the first time that up-regulation of NAG-1 contributes to silibinin-induced apoptosis in cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Melatonin (N-acetyl-5-methoxytryptamine) has recently gained attention as an anti-cancer agent and for combined cancer therapy. In this study, we investigated the underlying molecular mechanisms of the effects of melatonin on cancer cell death. Treatment with melatonin induced apoptosis and up-regulated the expression of the pro-apoptotic protein Bcl-2-interacting mediator of cell death (Bim) in renal cancer Caki cells. Furthermore, down-regulation of Bim expression by siRNA markedly reduced melatonin-mediated apoptosis. Melatonin increased Bim mRNA expression through the induction of Sp1 and E2F1 expression and transcriptional activity. We found that melatonin also modulated Bim protein stability through the inhibition of proteasome activity. However, melatonin-induced Bim upregulation was independent of melatonin's antioxidant properties and the melatonin receptor. Taken together, our results suggest that melatonin induces apoptosis through the upregulation of Bim expression at the transcriptional level and at the post-translational level. This article is protected by copyright. All rights reserved.
Journal of Pineal Research 10/2013; 56(1). DOI:10.1111/jpi.12102 · 7.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: RU486 (mifepristone) exerts an anticancer effect on cancer cells via induction of apoptosis. However, the molecular mechanisms are not fully understood. Here, we investigated the effect of RU486 on the apoptosis of U937 human leukemia cells. RU486 markedly increased apoptosis in U937 cells as well as in MDA231 human breast carcinoma, A549 human lung adenocarcinoma epithelial and HCT116 human colorectal carcinoma cells. RU486 increased dose-dependent release of mitochondrial cytochrome c, and reduced the mitochondrial membrane potential (MMP, Δψm) in RU486‑treated U937 cells. We also found that overexpression of Bcl-2 completely blocked RU486-mediated apoptosis. However, reactive oxygen species signaling had no effect on RU486‑induced apoptosis. RU486 increased the phosphorylation of p38 MAPK and JNK, but p38 MAPK only was associated with RU486-mediated apoptosis. Taken together, RU486 induces apoptosis through reduction in the mitochondrial membrane potential and activation of p38 MAPK in U937 human leukemia cells.
[Show abstract][Hide abstract] ABSTRACT: Withaferin A is a steroidal lactone purified from the Indian medicinal plant Withania somnifera. It exhibits a wide variety of activities, including anti-tumor, anti-inflammation, and immunomodulation properties. In this review, we focused on the anti-cancer effects of withaferin A. Withaferin A inhibits cell proliferation, metastasis, invasion, and angiogenesis in cancer cells. Furthermore, it sensitized irradiation, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-, and doxorubicin-mediated apoptosis. The results showed that multiple mechanisms were involved in withaferin A-mediated anti-cancer effects. First, withaferin A increased intracellular reactive oxygen species (ROS) production and induced ER stress- and mitochondria-mediated apoptosis. Second, withaferin A inhibited the signaling pathways (Jak/STAT, Akt, Notch, and c-Met), which are important in cell survival, proliferation, and metastasis. Third, it induced apoptosis and inhibited cancer cell migration through the up-regulation of prostate apoptosis protein-4 (Par-4). Finally, withaferin A up-regulated pro-apoptotic protein expression levels through the inhibition of proteasome activity. Our findings suggested that withaferin A is a potential, potent therapeutic agent.
[Show abstract][Hide abstract] ABSTRACT: Calyculin A (Cal A) is a serine/threonine phosphatase inhibitor that is capable of inducing apoptosis in cancer cells. In this study, we examined whether Cal A could modulate TRAIL-induced apoptosis in human renal carcinoma-derived Caki cells. Our results show that Cal A is capable of sensitizing Caki cells to TRAIL-induced apoptosis, as well as U2OS human osteosarcoma cells and A549 human lung adenocarcinoma epithelial cells. Cal A increases intracellular ROS production and down-regulates c-FLIP(L) expression. Interestingly, the down-regulation of protein phosphatase 1 (PP1) by PP1 siRNA also reduced c-FLIP(L) expression via reactive oxygen species production. Furthermore, Cal A induced death receptor 4 (DR4) mRNA and protein expression by enhancing DR4 mRNA stability. We also found that PP4 siRNA up-regulated DR4 mRNA and protein expression. Collectively, our results suggest that Cal A could enhance TRAIL-mediated apoptosis via the down-regulation of c-FLIP(L) and the up-regulation of DR4 in human renal cell carcinoma cell line Caki.
[Show abstract][Hide abstract] ABSTRACT: Rottlerin, a selective inhibitor of novel isoforms of protein kinase C δ (PKC δ), has been shown to exert multiple effects on cancer cells, including inhibition of cell proliferation and migration. However, the molecular mechanisms responsible for these effects are not fully understood. We found that rottlerin dramatically induced non-steroidal anti-inflammatory drug activated gene-1 (NAG-1) expression in both p53 wild-type and p53-null cancer cell lines, suggesting that NAG-1 upregulation is a common response to rottlerin that occurs independently of p53 in multiple cell lines. Although rottlerin is known to inhibit PKC δ, PKC δ siRNA and overexpression of dominant-negative (DN)-PKC δ did not affect rottlerin-mediated induction of NAG-1. These results suggest that rottlerin induces NAG-1 upregulation via a PKC δ-independent pathway. We also observed that CHOP protein levels were significantly increased by rottlerin, but CHOP siRNA did not affect rottlerin-induced NAG-1 expression. In addition, we demonstrated the involvement of the mitogen-activated protein kinase (MAP kinase) signal transduction pathway in rottlerin-induced NAG-1 expression. Inhibitors of MEK (PD98059) and p38 MAP kinase (SB203580) prevented rottlerin-induced NAG-1 expression. Furthermore, we found that down-regulation of NAG-1 attenuated rottlerin-induced apoptosis. Collectively, the results of this study demonstrate, for the first time, that upregulation of NAG-1 contributes to rottlerin-induced apoptosis in cancer cells.
[Show abstract][Hide abstract] ABSTRACT: TRAIL resistance in many cancer cells is one of the major problems in TRAIL-based cancer therapy. Thus, the agents that can sensitize the tumor cells to TRAIL-mediated apoptosis are strictly needed for the improvement of anti-cancer effect of TRAIL. Acrolein is a byproduct of lipid peroxidation, which has been involved in pulmonary, cardiac and neurodegenerative diseases. We investigated whether acrolein, an α,β-unsaturated aldehyde, can potentiate TRAIL-induced apoptosis in human renal cancer cells. The combined treatment with acrolein and TRAIL significantly induced apoptosis, and stimulated of caspase-3 activity, DNA fragmentation, and cleavage of PARP. We found that acrolein down-regulated the protein level of Bcl-2 and Bcl-2 overexpression inhibited the cell death induced by the combined treatment with acrolein and TRAIL. In addition, acrolein up-regulated C/EBP homologous protein (CHOP) and TRAIL death receptor 5 (DR5) and down-regulation of CHOP or DR5 expression using the respective small interfering RNA significantly attenuated the apoptosis induced by acrolein plus TRAIL. Interestingly, pretreatment with an antioxidant, N-acetylcysteine (NAC), inhibited not only CHOP and DR5 up-regulation but also the cell death induced by acrolein plus TRAIL. Taken together, our results demonstrated that acrolein enhances TRAIL-induced apoptosis in Caki cells through down-regulation of Bcl-2 and ROS dependent up-regulation of DR5.
Experimental Cell Research 08/2011; 317(18):2592-601. DOI:10.1016/j.yexcr.2011.08.005 · 3.37 Impact Factor