6-Shogaol enhances renal carcinoma Caki cells to TRAIL-induced apoptosis through reactive oxygen species-mediated cytochrome c release and down-regulation of c-FLIP(L) expression

Pterostilbene and 6-shogaol exhibit inhibitory effects on sunitinib resistance and motility by suppressing the RLIP76-initiated Ras/ERK and Akt/mTOR pathways in renal cancer cells

Sunitinib (SUN) is the first-line targeted therapeutic drug for advanced renal cell carcinoma (RCC). However, SUN resistance is frequently observed to result in tumor metastasis, with a poor survival rate. Therefore, finding an effective and safe adjuvant to reduce drug resistance is important for RCC treatment. Pterostilbene (PTE) and 6-shogaol (6-S) are natural phytochemicals found in edible sources and have potential applications against various cancers. However, the biological mechanisms of PTE and 6-S in SUN-resistant RCC are still unclear. Accordingly, this study investigated the regulatory effects of PTE and 6-S on cell survival, drug resistance, and cell invasion in 786-O and SUN-resistant 786-O (786-O SUNR) cells, respectively. The results demonstrated that PTE and 6-S induced apoptosis in both cell lines by upregulating the Bax/Bcl-2 ratio. Additionally, PTE and 6-S increased SUN sensitivity by inhibiting the expression of the RLIP76 transport protein, reduced cell invasion and downregulated MMP expression in both 786-O and 786-O SUNR cells. Mechanistically, PTE, and 6-S significantly and dose-dependently suppressed the RLIP76-initiated Ras/ERK and Akt/mTOR pathways. In summary, PTE and 6-S induce apoptosis, enhance SUN sensitivity, and inhibit migration in both 786-O and 786-O SUNR cells. These novel findings demonstrate the potential of PTE and 6-S as target therapeutic adjuvants for RCC treatment.

An overview of 6-shogaol: new insights into its pharmacological properties and potential therapeutic activities

Ginger (Zingiber officinale Roscoe) has traditionally been used as a cooking spice and herbal medicine for treating nausea and vomiting. More recently, ginger was found to effectively reduce the risk of diseases such as gastroenteritis, migraine, gonarthritis, etc., due to its various bioactive compounds. 6-Shogaol, the pungent phenolic substance in ginger, is the most pharmacologically active among such compounds. The aim of the present study was to review the pharmacological characteristic of 6-shogaol, including the properties of anti-inflammatory, antioxidant and antitumour, and its corresponding molecular mechanism. With its multiple mechanisms, 6-shogaol is considered a beneficial natural compound, and therefore, this review will shed some light on the therapeutic role of 6-shogaol and provide a theoretical basis for the development and clinical application of 6-shogaol.

Anticancer perspective of 6-shogaol: anticancer properties, mechanism of action, synergism and delivery system

Cancer is a malignant disease that has plagued human beings all the time, but the treatment effect of commonly used anticancer drugs in clinical practice is not ideal by reason of their drug tolerance and Strong adverse reactions to patients. Therefore, it is imperative to find effective and low-toxic anticancer drugs. Many research works have shown that natural products in Chinese herbal medicine have great anticancer potential, such as 6-shogaol, a monomer composition obtained from Chinese herbal ginger, which has been confirmed by numerous in vitro or vivo studies to be an excellent anti-cancer active substance. In addition, most notably, 6-shogaol has different selectivity for normal and cancer cells during treatment, which makes it valuable for further research and clinical development. Therefore, this review focus on the anti-cancer attributes, the mechanism and the regulation of related signaling pathways of 6-shogaol. In addition, its synergy with commonly used anticancer drugs, potential drug delivery systems and prospects for future research are discussed. This is the first review to comprehensively summarize the anti-cancer mechanism of 6-shogaol, hoping to provide a theoretical basis and guiding significance for future anti-cancer research and clinical development of 6-shogaol.

6-Shogaol as a Novel Thioredoxin Reductase Inhibitor Induces Oxidative-Stress-Mediated Apoptosis in HeLa Cells

Inhibition of thioredoxin reductase (TrxR) is a crucial strategy for the discovery of antineoplastic drugs. 6-Shogaol (6-S), a primary bioactive compound in ginger, has high anticancer activity. However, its potential mechanism of action has not been thoroughly investigated. In this study, we demonstrated for the first time that 6-S, a novel TrxR inhibitor, promoted oxidative-stress-mediated apoptosis in HeLa cells. The other two constituents of ginger, 6-gingerol (6-G) and 6-dehydrogingerduone (6-DG), have a similar structure to 6-S but fail to kill HeLa cells at low concentrations. 6-Shogaol specifically inhibits purified TrxR1 activity by targeting selenocysteine residues. It also induced apoptosis and was more cytotoxic to HeLa cells than normal cells. The molecular mechanism of 6-S-mediated apoptosis involves TrxR inhibition, followed by an outburst of reactive oxygen species (ROS) production. Furthermore, TrxR knockdown enhanced the cytotoxic sensitivity of 6-S cells, highlighting the physiological significance of targeting TrxR by 6-S. Our findings show that targeting TrxR by 6-S reveals a new mechanism underlying the biological activity of 6-S and provides meaningful insights into its action in cancer therapeutics.

NS5-independent Ablation of STAT2 by Zika virus to antagonize interferon signalling

Flavivirus genus includes numerous arthropod-borne human pathogens that are clinically important. Flaviviruses are notorious for their ability to antagonize host interferon (IFN) induced anti-viral signalling. It has been documented that NS5s of flaviviruses mediate proteasome degradation of STAT2 to evade IFN signalling. Deciphering the molecular mechanism of the IFN antagonism by the viruses and reversing this antagonism may dictate anti-viral responses and provide novel antiviral approaches. In this report, by using Zika virus (ZIKV) as a model, we first demonstrated that ZIKV antagonized interferon signalling in an infectious dose-dependent manner; in other words, the virus antagonized interferon signalling at a high multiple of infection (MOI) and was sensitive to interferon signalling at a low MOI. Mechanistically, we found that ZIKV infection triggered degradation of ubiquitinated STAT2 and host short-lived proteins while didn't affect the proteasome activity per se. ZIKV infection resulted in suppression of host de novo protein synthesis. Overexpression of NS5 alone only marginally reduced STAT2 and had no effect on the host de novo protein synthesis. Ectopically expressed murine STAT2 that was resistant to NS5- and ZIKV-induced ablation exaggerated the IFN-induced anti-viral signalling. These data favour a new model of the innate immune evasion of ZIKV in which the viral infection triggers suppression of host de novo protein synthesis to accelerate the degradation of short-lived, ubiquitinated STAT2. As flaviviruses share a very conserved replication strategy, the mechanisms of IFN antagonism elucidated here might also be employed by other flaviviruses.

6-Shogaol induces apoptosis in acute lymphoblastic leukaemia cells by targeting p53 signalling pathway and generation of reactive oxygen species

Combination therapies, using medicinal herbs, are broadly recommended to attenuate the chemotherapy adverse effects. Based on our previous findings considering the anti-leukaemic effects of ginger extract on acute lymphoblastic leukaemia (ALL) cells, the present study was aimed to investigate the anti-cancer role of this pharmaceutical plant on ALL mice models. Moreover, we worked towards identifying the most anti-leukaemic derivative of ginger and the mechanism through which it may exert its cytotoxic impact. In vivo experiments were performed using five groups of six C57BL/6 nude mice, and the anti-leukaemic activity of ginger extract alone or in combination with methotrexate (MTX) was examined. Results showed increased survival rate and reduced damages in mice brain and liver tissues. Subsequently, MTT assay demonstrated synergistic growth inhibitory effect of 6-shogaol (6Sh) and MTX on ALL cell lines and patients primary cells. Eventually, the molecular anti-neoplastic mechanism of 6Sh was evaluated using Bioinformatics. Flow cytometry illustrated 6Sh-mediated apoptosis in Nalm-6 cells confirmed by Western blotting and RT-PCR assays. Further analyses exhibited the generation of reactive oxygen species (ROS) through 6Sh. The current study revealed the in vivo novel anti-leukaemic role of ginger extract, promoted by MTX. Moreover, 6-shogaol was introduced as the major player of ginger cytotoxicity through inducing p53 activity and ROS generation.

Effect of 6-Shogaol on the Glucose Uptake and Survival of HT1080 Fibrosarcoma Cells

Ginger is a plant that is native to southern China. In the last decade and research on the components of ginger has significantly increased; of these components, 6-shogaol exhibits the greatest potential antitumor capacity. However, the molecular mechanism through which 6-shogaol exerts its effects has not yet been elucidated. In this study, the effect of 6-shogaol on tumor cells that were derived from human fibrosarcoma (HT1080) was evaluated. Cell viability was determined by a (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT assay testing different concentrations of 6-shogaol (2.5–150 μM). Subsequently, the effect of 6-shogaol on reactive oxygen species (ROS) production, glucose uptake, and protein expression of the signaling pathway phosphatase and tensin homolog/ protein kinase B /mammalian target of rapamycin (PTEN/Akt/mTOR) was measured. 6-Shogaol reduced the viability of the tumor cells and caused an increase in ROS production, which was attenuated with the addition of N-acetylcysteine, and the recovery of cell viability was observed. The increase in ROS production in response to 6-shogaol was associated with cell death. Similarly, glucose uptake decreased with incremental concentrations of 6-shogaol, and an increase in the expression of mTOR-p and Akt-p proteins was observed; PTEN was active in all the treatments with 6-shogaol. Thus, the results suggest that cells activate uncontrolled signaling pathways, such as phosphoinositide 3-kinase (PI3K)/Akt/mTOR, among other alternative mechanisms of metabolic modulation and of survival in order to counteract the pro-oxidant effect of 6-shogaol and the decrease in glucose uptake. Interestingly, a differential response was observed when non-cancerous cells were treated with 6-shogaol.

Attenuation of autophagy flux by 6-shogaol sensitizes human liver cancer cells to TRAIL-induced apoptosis via p53 and ROS

Tumor necrosis factor (TNF)‑related apoptosis‑inducing ligand (TRAIL) is a member of the TNF superfamily and is an antitumor drug that induces apoptosis in tumor cells with minimal or no effects on normal cells. Here, it is demonstrated that 6‑shogaol (6‑sho), a bioactive component of ginger, exerted anti‑inflammatory and anticancer properties, attenuated tumor cell propagation and induced TRAIL‑mediated cell death in liver cancer cells. The current study identified a potential pathway by revealing that TRAIL and 6‑sho or chloroquine acted together to trigger reactive oxygen species (ROS) production, to upregulate tumor‑suppressor protein 53 (p53) expression and to change the mitochondrial transmembrane potential (MTP). Treatment with N‑acetyl‑L‑cysteine reversed these effects, restoring the MTP and attenuated ROS production and p53 expression. Interestingly, treatment with 6‑sho increased p62 and microtubule‑associated proteins 1A/1B light chain 3B‑II levels, indicating an inhibited autophagy flux. In conclusion, attenuation of 6‑sho‑induced autophagy flux sensitized cells to TRAIL‑induced apoptosis via p53 and ROS, suggesting that the administration of TRAIL in combination with 6‑sho may be a suitable therapeutic method for the treatment of TRAIL‑resistant Huh7 liver cells.

mTORC1/2 inhibitor and curcumin induce apoptosis through lysosomal membrane permeabilization-mediated autophagy

mTOR is an important regulator of cell growth and forms two complexes, mTORC1/2. In cancer, mTOR signaling is highly activated, and the regulation of this signaling, as an anti-cancer strategy, has been emphasized. However, PP242 (inhibitor of mTORC1 and mTORC2) alone did not induce human renal carcinoma cell death. In this study, we found that PP242 alone did not alter cell viability, but combined curcumin and PP242 treatment induced cell death. Combined PP242 and curcumin treatment induced Bax activation and decreased expression of Mcl-1 and Bcl-2. Furthermore, co-treatment with PP242 and curcumin-induced the downregulation of the Rictor (an mTORC2 complex protein) and Akt protein levels, and ectopic overexpression of Rictor or Akt inhibited PP242 plus curcumin induced cell death. Downregulation of Rictor increased cytosolic Ca²⁺ release from endoplasmic reticulum, which led to lysosomal damage in PP242 plus curcumin-treated cells. Furthermore, damaged lysosomes induced autophagy. Autophagy inhibitors markedly inhibited cell death. Finally, combined curcumin and PP242 treatment reduced tumor growth and induced cell death in xenograft models. Altogether, our results reveal that combined PP242 and curcumin treatment could induce autophagy-mediated cell death by reducing the expression of Rictor and Akt in renal carcinoma cells.

Occurrence, biological activity and metabolism of 6-shogaol

As one of the main bioactive compounds of dried ginger, 6-shogaol has been widely used to alleviate many ailments. It is also a major pungent flavor component, and its precursor prior to dehydration is 6-gingerol, which is reported to be responsible for the pungent flavor and biological activity of fresh ginger. Structurally, gingerols including 6-gingerol have a β-hydroxyl ketone moiety and is liable to dehydrate to generate an α,β-unsaturated ketone under heat and/or acidic conditions. The conjugation of the α,β-unsaturated ketone skeleton in the chemical structure of 6-shogaol explicates its higher potency and efficacy than 6-gingerol in terms of antioxidant, anti-inflammatory, anticancer, antiemetic and other bioactivities. Research on the health benefits of 6-shogaol has been conducted and results have been reported recently; however, scientific data are scattered due to a lack of systematic collection. In addition, action mechanisms of the preventive and/or therapeutic actions of 6-shogaol remain obscurely non-collective. Herein, we review the preparations, biological activity and mechanisms, and metabolism of 6-shogaol as well as the properties of 6-shogaol metabolites.

YM155 sensitizes TRAIL-induced apoptosis through cathepsin S-dependent down-regulation of Mcl-1 and NF-κB-mediated down-regulation of c-FLIP expression in human renal carcinoma Caki cells

YM155, a small-molecule survivin inhibitor, has been reported for its anti-cancer activity in various cancer cells. In this study, we investigated the effect of YM155 to enhance TRAIL-mediated apoptosis in human renal carcinoma cells. We found that YM155 alone had no effect on apoptosis, however, combined treatment with YM155 and TRAIL markedly induced apoptosis in human renal carcinoma cells (Caki, ACHN, and A498), breast cancer cells (MDA-MB231), and glioma cells (U251MG), but not normal cells [mesangial cell (MC) and human skin fibroblast (HSF)]. YM155 induced down-regulation of Mcl-1 expression at the post-translational levels, and the overexpression of Mcl-1 markedly inhibited YM155 plus TRAIL-induced apoptosis. Furthermore, YM155 induced down-regulation of c-FLIP mRNA expression through inhibition of NF-κB transcriptional activity. Ectopic expression of c-FLIP markedly blocked YM155-induced TRAIL sensitization. Taken together, our results suggested that YM155 sensitizes TRAIL-mediated apoptosis via down-regulation of Mcl-1 and c-FLIP expression in renal carcinoma Caki cells.

Up-regulation of 5-lipoxygenase by inhibition of cathepsin G enhances TRAIL-induced apoptosis through down-regulation of survivin

Cathepsin G is a serine protease secreted from activated neutrophils, it has important roles in inflammation and immune response. Moreover, cathepsin G promotes tumor cell-cell adhesion and migration in cancer cells. In this study, we investigated whether inhibition of cathepsin G could sensitize TRAIL-mediated apoptosis in cancer cells. An inhibitor of cathepsin G [Cathepsin G inhibitor I (Cat GI); CAS 429676-93-7] markedly induced TRAIL-mediated apoptosis in human renal carcinoma (Caki, ACHN, and A498), lung cancer (A549) and cervical cancer (Hela) cells. In contrast, combined treatment with Cat GI and TRAIL had no effect on apoptosis in normal cells [mesangial cell (MC) and human skin fibroblast (HSF)]. Cat GI induced down-regulation of survivin expression at the post-translational level, and overexpression of survivin markedly blocked apoptosis induced by combined treatment with Cat GI plus TRAIL. Interestingly, Cat GI induced down-regulation of survivin via 5-lipoxygenase (5-LOX)-mediated reactive oxygen species (ROS) production. Inhibition of 5-LOX by gene silencing (siRNA) or a pharmacological inhibitor of 5-LOX (zileuton) markedly attenuated combined treatment-induced apoptosis. Taken together, our results indicate that inhibition of cathepsin G sensitizes TRAIL-induced apoptosis through 5-LOX-mediated down-regulation of survivin expression.

Kaempferol Sensitizes Human Ovarian Cancer Cells-OVCAR-3 and SKOV-3 to Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-Induced Apoptosis via JNK/ERK-CHOP Pathway and Up-Regulation of Death Receptors 4 and 5

Background

Ovarian cancer is the most common gynecological malignancies in women, with high mortality rates worldwide. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) superfamily which preferentially induces apoptosis of cancer cells. However, acquired resistance to TRAIL hampers its therapeutic application. Identification of compounds that sensitize cancer cells to TRAIL is vital in combating resistance to TRAIL. The effect of kaempferol, a flavonoid enhancing TRAIL-induced apoptosis in ovarian cancer cells, was investigated in this study.

Material/Methods

The cytotoxic effects of TRAIL (25 ng/mL) and kaempferol (20–100 μM) on human ovarian cancer cells OVCAR-3 and SKOV-3 were assessed. Effect of kaempferol on the expression patterns of cell survival proteins (Bcl-xL, Bcl-2, survivin, XIAP, c-FLIP) and apoptotic proteins (caspase-3, caspase-8, caspase-9, Bax) were studied. The influence of kaempferol on expression of DR4 and DR5 death receptors on the cell surface and protein and mRNA levels was also analyzed. Apoptosis following silencing of DR5 and CHOP by small interfering RNA (siRNA), and activation of MAP kinases were analyzed as well.

Results

Kaempferol enhanced apoptosis and drastically up-regulated DR4, DR5, CHOP, JNK, ERK1/2, p38 and apoptotic protein expression with decline in the expression of anti-apoptotic proteins. Further transfection with siRNA specific to CHOP and DR5 indicated the involvement of CHOP in DR5 up-regulation and also the contribution of DR5 in kaempferol-enhanced TRAIL-induced apoptosis.

Conclusions

Kaempferol sensitized ovarian cancer cells to TRAIL-induced apoptosis via up-regulation of DR4 and DR5 through ERK/JNK/CHOP pathways.

A Mini-Review of Reactive Oxygen Species in Urological Cancer: Correlation with NADPH Oxidases, Angiogenesis, and Apoptosis

Oxidative stress refers to elevated reactive oxygen species (ROS) levels, and NADPH oxidases (NOXs), which are one of the most important sources of ROS. Oxidative stress plays important roles in the etiologies, pathological mechanisms, and treatment strategies of vascular diseases. Additionally, oxidative stress affects mechanisms of carcinogenesis, tumor growth, and prognosis in malignancies. Nearly all solid tumors show stimulation of neo-vascularity, termed angiogenesis, which is closely associated with malignant aggressiveness. Thus, cancers can be seen as a type of vascular disease. Oxidative stress-induced functions are regulated by complex endogenous mechanisms and exogenous factors, such as medication and diet. Although understanding these regulatory mechanisms is important for improving the prognosis of urothelial cancer, it is not sufficient, because there are controversial and conflicting opinions. Therefore, we believe that this knowledge is essential to discuss observations and treatment strategies in urothelial cancer. In this review, we describe the relationships between members of the NOX family and tumorigenesis, tumor growth, and pathological mechanisms in urological cancers including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, we introduce natural compounds and chemical agents that are associated with ROS-induced angiogenesis or apoptosis.

Methylglyoxal-induced apoptosis is dependent on the suppression of c-FLIPL expression via down-regulation of p65 in endothelial cells

Methylglyoxal (MGO) is a reactive dicarbonyl metabolite of glucose, and its plasma levels are elevated in patients with diabetes. Studies have shown that MGO combines with the amino and sulphhydryl groups of proteins to form stable advanced glycation end products (AGEs), which are associated with vascular endothelial cell (EC) injury and may contribute to the progression of atherosclerosis. In this study, MGO induced apoptosis in a dose-dependent manner in HUVECs, which was attenuated by pre-treatment with z-VAD, a pan caspase inhibitor. Treatment with MGO increased ROS levels, followed by dose-dependent down-regulation of c-FLIP_L . In addition, pre-treatment with the ROS scavenger NAC prevented the MGO-induced down-regulation of p65 and c-FLIP_L , and the forced expression of c-FLIP_L attenuated MGO-mediated apoptosis. Furthermore, MGO-induced apoptotic cell death in endothelium isolated from mouse aortas. Finally, MGO was found to induce apoptosis by down-regulating p65 expression at both the transcriptional and posttranslational levels, and thus, to inhibit c-FLIP_L mRNA expression by suppressing NF-κB transcriptional activity. Collectively, this study showed that MGO-induced apoptosis is dependent on c-FLIP_L down-regulation via ROS-mediated down-regulation of p65 expression in endothelial cells.

Reactive oxygen species and cancer paradox: To promote or to suppress?

Reactive oxygen species (ROS), a group of highly reactive ions and molecules, are increasingly being appreciated as powerful signaling molecules involved in the regulation of a variety of biological processes. Indeed, their role is continuously being delineated in a variety of pathophysiological conditions. For instance, cancer cells are shown to have increased ROS levels in comparison to their normal counterparts. This is partly due to an enhanced metabolism and mitochondrial dysfunction in cancer cells. The escalated ROS generation in cancer cells contributes to the biochemical and molecular changes necessary for the tumor initiation, promotion and progression, as well as, tumor resistance to chemotherapy. Therefore, increased ROS in cancer cells may provide a unique opportunity to eliminate cancer cells via elevating ROS to highly toxic levels intracellularly, thereby, activating various ROS-induced cell death pathways, or inhibiting cancer cell resistance to chemotherapy. Such results can be achieved by using agents that either increase ROS generation, or inhibit antioxidant defense, or even a combination of both. In fact, a large variety of anticancer drugs, and some of those currently under clinical trials, effectively kill cancer cells and overcome drug resistance via enhancing ROS generation and/or impeding the antioxidant defense mechanism. This review focuses on our current understanding of the tumor promoting (tumorigenesis, angiogenesis, invasion and metastasis, and chemoresistance) and the tumor suppressive (apoptosis, autophagy, and necroptosis) functions of ROS, and highlights the potential mechanism(s) involved. It also sheds light on a very novel and an actively growing field of ROS-dependent cell death mechanism referred to as ferroptosis.

New Frontiers in Promoting TRAIL-Mediated Cell Death: Focus on Natural Sensitizers, miRNAs, and Nanotechnological Advancements

Cancer is a multifaceted and genomically complex disease, and rapidly emerging scientific evidence is emphasizing on intra-tumor heterogeneity within subpopulations of tumor cells and rapidly developing resistance against different molecular therapeutics. There is an overwhelmingly increasing list of agents currently being tested for efficacy against cancer. In accordance with the concept that therapeutic agents must have fewer off target effects and considerable efficacy, TRAIL has emerged as one among the most deeply investigated proteins reportedly involved in differential killing of tumor cells. Considerable killing activity of TRAIL against different cancers advocated its entry into clinical trials. However, data obtained through preclinical and cell culture studies are deepening our understanding of wide-ranging mechanisms which induce resistance against TRAIL-based therapeutics. These include downregulation of death receptors, overexpression of oncogenes, inactivation of tumor suppressor genes, imbalance of pro- and anti-apoptotic proteins, and inactivation of intrinsic and extrinsic pathways. Substantial fraction of information has been added into existing pool of knowledge related to TRAIL biology and recently accumulating evidence is adding new layers to regulation of TRAIL-induced apoptosis. Certain hints have emerged underscoring miR135a-3p- and miR-143-mediated regulation of TRAIL-induced apoptosis, and natural agents have shown remarkable efficacy in improving TRAIL-based therapeutics by increasing expression of tumor suppressor miRNAs. In this review, we summarize most recent breakthroughs related to naturopathy and strategies to nanotechnologically deliver TRAIL to the target site in xenografted mice. We also set spotlight on positive and negative regulators of TRAIL-mediated signaling. Comprehensive knowledge of genetics and proteomics of TRAIL-based signaling network obtained from cancer patients of different populations will be helpful in getting a step closer to personalized medicine.

Jaceosidin induces apoptosis through Bax activation and down-regulation of Mcl-1 and c-FLIP expression in human renal carcinoma Caki cells

Jaceosidin is a flavonoid isolated from Artemisia vestita that has been reported to possess anti-tumor and anti-proliferative activities in many cancer cells. In this study, we investigated the anti-tumor activity of jaceosodin in renal carcinoma cells. Jaceosidin induced apoptosis in multiple human renal carcinoma cells (Caki, ACHN, A498, and 786-O), lung cancer cells (A549) and glioma cells (U251MG). In contrast, jaceosidin does not induce apoptosis in normal human umbilical vein cells (EA.hy926). Apoptotic cell death was associated with the activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase. Treatment with jaceosidin also caused loss of mitochondrial membrane potential (MMP) and Bax activation, which led to the release of cytochrome c into the cytosol. We also found that jaceosidin downregulated Mcl-1 and c-FLIP expression at the transcriptional level and that ectopic expression of Mcl-1 and c-FLIP blocked jaceosidin-induced apoptosis. Cumulatively, our results suggest that jaceosidin induces apoptosis in renal carcinoma cells through Bax activation and reduces Mcl-1 and c-FLIP expression.

Thymoquinone induces apoptosis through downregulation of c-FLIP and Bcl-2 in renal carcinoma Caki cells

Renal carcinoma is a common and frequently fatal carcinoma occurring worldwide and death rates due to this carcinoma are increasing with time. In the present study, we investigated the potential of thymoquinone a natural compound to induce apoptosis in renal carcinoma Caki cells. Thymoquinone efficiently enhanced the apoptotic population of Caki cells in a dose-dependent manner. Moreover, thymoquinone-mediated apoptosis caused downregulation of c-FLIP and Bcl-2, the master regulators of the anti-apoptotic mechanism. However, we did not find any changes in mRNA expression level of c-FLIP, therefore; this regulation of c-FLIP was a result of post-translation modification by thymoquinone. In contrast, expression of the Bcl-2 protein was observed at both transcriptional and translational level. However, we also observed that thymoquinone enhanced the level of intracellular reactive oxygen species (ROS) in Caki cells, which resulted in reduction of mitochondrial membrane potential (MMP) and cytochrome c release into cytoplasm. Our results postulate that thymoquinone induces apoptosis through downregulating c-FLIP and Bcl-2 which can be utilized as a chemotherapeutic agent to treat renal carcinoma.

Redox signaling: Potential arbitrator of autophagy and apoptosis in therapeutic response

Redox signaling plays important roles in the regulation of cell death and survival in response to cancer therapy. Autophagy and apoptosis are discrete cellular processes mediated by distinct groups of regulatory and executioner molecules, and both are thought to be cellular responses to various stress conditions including oxidative stress, therefore controlling cell fate. Basic levels of reactive oxygen species (ROS) may function as signals to promote cell proliferation and survival, whereas increase of ROS can induce autophagy and apoptosis by damaging cellular components. Growing evidence in recent years argues for ROS that below detrimental levels acting as intracellular signal transducers that regulate autophagy and apoptosis. ROS-regulated autophagy and apoptosis can cross-talk with each other. However, how redox signaling determines different cell fates by regulating autophagy and apoptosis remains unclear. In this review, we will focus on understanding the delicate molecular mechanism by which autophagy and apoptosis are finely orchestrated by redox signaling and discuss how this understanding can be used to develop strategies for the treatment of cancer.

Structurally related ganoderic acids induce apoptosis in human cervical cancer HeLa cells: Involvement of oxidative stress and antioxidant protective system

Ganoderic acids (GAs) produced by Ganoderma lucidum possess anticancer activities with the generation of reactive oxygen species (ROS). However, the role of oxidative stress in apoptotic process induced by GAs is still undefined. In this study, the effects of four structurally related GAs, i.e. GA-T, GA-Mk, and two deacetylated derivatives of GA-T (GA-T1 and GA-T2) on the antioxidant defense system and induced apoptosis in cervical cancer cells HeLa were investigated in vitro. Our results indicated that the tested GAs (5-40 μM) induced apoptotic cell death through mitochondrial membrane potential decrease and activation of caspase-9 and caspase-3. Furthermore, GAs increased the generation of intracellular ROS and attenuated antioxidant defense system by decreasing glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities. The above effects were remarkably blocked by the exogenous antioxidants, i.e. N-acetylcysteine, catalase and diphenyleneiodonium chloride. The potency of the four GAs toward induced apoptosis, generation of ROS and suppression of antioxidant defense system was in the order of: GA-T > GA-Mk ≈ GA-T1 > GA-T2 in HeLa cells. These findings suggest that GAs induced mitochondria-dependent cell apoptosis in HeLa cells are mediated via enhancing oxidative stress and depressing antioxidant defense. Additionally, the acetylation of hydroxyl groups in GAs may contribute to their pro-oxidant activities and cytotoxicity, which is helpful to the development of novel chemotherapy agents.