Synergistic induction of cell death in liver tumor cells by TRAIL and chemotherapeutic drugs via the BH3-only proteins Bim and Bid. Cell Death Dis. 2010;1:e86. [PMID: 21368859 DOI: 10.1038/cddis.2010.66]

Involvement of NF-κB/PI3K/AKT signaling pathway in the protective effect of prunetin against a diethylnitrosamine induced hepatocellular carcinogenesis in rats

Prunetin (PRU) is an O-methylated flavonoid that is present in various natural plants and a primary significant compound found in isoflavone. Liver cancer creates major carcinogenic death despite recently advanced therapies. Hepatocellular carcinoma (HCC) treatment and prognosis are better in people with secure liver function. In the present study, we evaluated the action of PRU on diethylnitrosamine (DEN) alone HCC in a rat model through inflammation-mediated cell proliferative phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway analysis. Male Wistar rats were divided into four groups of six rats each. Group I, normal rats; Group II, DEN alone; Group III, DEN + PRU, and Group IV, PRU-alone. All groups of rats carried out hepatic cancer development by hypothesis antioxidant, biochemical, cell proliferative, apoptosis, cytokines protein, and gene expression status profiles. In tumor incidence DEN + PRU, 100% delayed the tumor growth disappearance of the lesion,  and reversal of normal liver architecture was observed. Liver marker enzymes levels decreased when antioxidant levels (superoxidase dismutase, catalase, glutathione peroxidase, and glutathione reductase) were in Group III. Proinflammatory markers nuclear factor-κB, interleukin (IL)-6, IL-1β, and tumor necrosis factor α, were elevated in the rat's serum in Group III. Cell proliferative markers proliferating cell nuclear antigen and Cyclin-D1 protein expressions were downregulated; in contrast, Bcl-2, Bax, caspase-3, and caspase-9 gene expressions were upregulated and then it followed that protein expression of PI3K/AKT was downregulated in PRU-treated groups. PRU assisted reversal of liver damage, antioxidant enzyme restoration cytokine balance, protein, and gene expression to control levels. Taken together, PRU improves functions of the liver, and as such prevents HCC. PRU can be used together with chemopreventives for HCC.

Hibiscus Flower and Olive Leaf Extracts Activate Apoptosis in SH-SY5Y Cells

Compounds of natural origin may constitute an interesting tool for the treatment of neuroblastoma, the most prevalent extracranial solid tumor in children. PRES is a commercially available food supplement, composed of a 13:2 (w/w) extracts mix of Olea europaea L. leaves (OE) and Hibiscus sabdariffa L. flowers (HS). Its potential towards neuroblastoma is still unexplored and was thus investigated in human neuroblastoma SH-SY5Y cells. PRES decreased the viability of cells in a concentration-dependent fashion (24 h IC₅₀ 247.2 ± 31.8 µg/mL). Cytotoxicity was accompanied by an increase in early and late apoptotic cells (AV-PI assay) and sub G0/G1 cells (cell cycle analysis), ROS formation, reduction in mitochondrial membrane potential, and caspases activities. The ROS scavenger N-acetyl-L-cysteine reverted the cytotoxic effects of PRES, suggesting a key role played by ROS in PRES-mediated SH-SY5Y cell death. Finally, the effects of OE and HS extracts were singularly tested and compared to those of the corresponding mixture. OE- or HS-mediated cytotoxicity was always significantly lower than that caused by PRES, suggesting a synergic effect. In conclusion, the present findings highlight the potential of PRES for the treatment of neuroblastoma and offers the basis for a further characterization of the mechanisms underlying its effects.

The mitochondrial disruptor devimistat (CPI-613®) synergizes with genotoxic anticancer drugs in colorectal cancer therapy in a Bim-dependent manner

Colorectal cancer (CRC) is one of the most frequent tumor entities, with an increasing incidence and mortality in younger adults in Europe and the US. 5-year survival rates for advanced CRC are still low, highlighting the need for novel targets in CRC therapy. Here, we investigated the therapeutic potential of the compound devimistat (CPI 613®) that targets altered mitochondrial cancer cell metabolism and its synergism with the antineoplastic drugs 5-fluorouracil (5-FU) and irinotecan (IT) in CRC. Devimistat exerted a comparable cytotoxicity in a panel of established CRC cell lines and patient-derived short-term culture independent of their genetic and epigenetic status, whereas human colonic epithelial cells were more resistant indicating tumor selectivity. These findings were corroborated in intestinal organoid and tumoroid models. Mechanistically, devimistat disrupted mitochondrial membrane potential and severely impaired mitochondrial respiration, resulting in CRC cell death induction independent of p53. Combination treatment of devimistat with 5-FU or IT demonstrated synergistic cell killing in CRC cells as shown by Combenefit modelling and Chou-Talalay analysis. Increased cell death induction was revealed as major mechanism involving downregulation of anti-apoptotic genes and accumulation of pro-apoptotic Bim, which was confirmed by its genetic knockdown. In human CRC xenograft mouse models, devimistat showed anti-tumor activity and synergized with IT, resulting in prolonged survival and enhanced therapeutic efficacy. In human tumor xenografts, devimistat prevented IT-triggered p53 stabilization and caused synergistic Bim induction. Taken together, our study revealed devimistat as a promising candidate in CRC therapy by synergizing with established antineoplastic drugs in vitro and in vivo.

Anti-cancer Activity of Centipeda minima Extract in Triple Negative Breast Cancer via Inhibition of AKT, NF-κB, and STAT3 Signaling Pathways

Breast cancer is the most commonly diagnosed cancer in females worldwide. Estimates from the World Health Organization (WHO) International Agency for Research on Cancer, suggest that globally, there were around 2.1 million new breast cancer cases and 627,000 deaths due to breast cancer in 2018. Among the subtypes of breast cancer, triple negative breast cancer (TNBC) is the most aggressive and carries the poorest prognosis, largest recurrence, and lowest survival rate. Major treatment options for TNBC patients are mainly constrained to chemotherapy, which can be accompanied by severe side effects. Therefore, development of novel and effective anti-cancer drugs for the treatment of TNBC are urgently required. Centipeda minima is a well-known traditional Chinese herbal medicine that has historically been used to treat rhinitis, sinusitis, relieve pain, and reduce swelling. Recent studies have shown that Centipeda minima exhibited efficacy against certain cancers, however, to date, no studies have been conducted on its effects in breast cancer. Here, we aimed to investigate the anti-cancer activity of the total extract of Centipeda minima (CME), and its underlying mechanism, in TNBC. In MDA-MB-231, we found that CME could significantly reduce cell viability and proliferation, induce apoptosis and inhibit cancer cell migration and invasion, in a dose and time-dependent manner. We showed that CME may potentially act via inhibition of multiple signaling pathways, including the EGFR, PI3K/AKT/mTOR, NF-κB, and STAT3 pathways. Treatment with CME also led to in vitro downregulation of MMP-9 activity and inhibition of metastasis. Further, we demonstrated that CME could significantly reduce tumor burden in MDA-MB-231 xenograft mice, without any appreciable side effects. Based on our findings, CME is a promising candidate for development as a therapeutic with high efficacy against TNBC.

Countering TRAIL Resistance in Melanoma

Melanoma of the skin has become a prime example for demonstrating the success of targeted cancer therapy. Nevertheless, high mortality has remained, mainly related to tumor heterogeneity and inducible therapy resistance. But the development of new therapeutic strategies and combinations has raised hope of finally defeating this deadly disease. TNF-related apoptosis-inducing ligand (TRAIL) represents a promising antitumor strategy. The principal sensitivity of melanoma cells for TRAIL was demonstrated in previous studies; however, inducible resistance appeared as a major problem. To address this issue, combination strategies were tested, and survival pathway inhibitors were shown to sensitize melanoma cells for TRAIL-induced apoptosis. Finally, cell cycle inhibition was identified as a common principle of TRAIL sensitization in melanoma cells. Mitochondrial apoptosis pathways, pro- and antiapoptotic Bcl-2 proteins as well as the rheostat consisted of Smac (Second mitochondria-derived activator of caspase) and XIAP (X-linked inhibitor of apoptosis protein) appeared to be of particular importance. Furthermore, the role of reactive oxygen species (ROS) was recognized in this setting. Inducible TRAIL resistance in melanoma can be explained by (i) high levels of antiapoptotic Bcl-2 proteins, (ii) high levels of XIAP, and (iii) suppressed Bax activity. These hurdles have to be overcome to enable the use of TRAIL in melanoma therapy. Several strategies appear as particularly promising, including new TRAIL receptor agonists, Smac and BH3 mimetics, as well as selective kinase inhibitors.

Death Receptor Interactions With the Mitochondrial Cell Death Pathway During Immune Cell-, Drug- and Toxin-Induced Liver Damage

Due to its extensive vascularization and physiological function as a filter and storage organ, the liver is constantly exposed to infectious and tumorigenic threat, as well as damaging actions of xenobiotics. Detoxification reactions are essential for the excretion of harmful substances, but harbor also the risk of “side effects” leading to dangerous metabolites of otherwise harmless substances, a well known effect during paracetamol overdose. These drugs can have detrimental effects, which often involves the induction of sterile inflammation and activation of the immune system. Therefore, the role of certain immune cells and their effector molecules in the regulation of drug-induced liver damage are of special interest. Hepatocytes are type II cells, and death receptor (DR)-induced cell death (CD) requires amplification via the mitochondrial pathway. However, this important role of the mitochondria and associated CD-regulating signaling complexes appears to be not restricted to DR signaling, but to extend to drug-induced activation of mitochondrial CD pathways. We here discuss the role of members of the TNF family, with a focus on TRAIL, and their interactions with the Bcl-2 family in the crosstalk between the extrinsic and intrinsic CD pathway during xenobiotic-induced liver damage.

Induction of Apoptosis Scutellaria baicalensis Georgi Root Extract by Inactivation of the Phosphatidyl Inositol 3-kinase/Akt Signaling Pathway in Human Leukemia U937 Cells

Background

The roots of Scutellaria baicalensis Georgi (Labiatae) have been widely used in traditional medicine for treatment of various diseases. In this study, we investigated the effects of ethanol extracts of S. baicalensis roots (EESB) on the growth ofn human leukemia U937 cells.

Methods

The effect of EESB on cell viability was measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apoptosis was determined using 4,6-diamidino-2-phenyllindile staining and flow cytometry. The effects of EESB on the expression of regulatory proteins of apoptosis and phosphatidyl inositol 3-kinase (PI3K)/Akt signaling were determined by Western blotting. Caspase activity and mitochondrial membrane potential (MMP) were measured using flow cytometric analysis.

Results

EESB significantly inhibited the growth of U937 cells and induced apoptosis, which was associated with down-regulation of anti-apoptotic Bcl-2, up-regulation of pro-apoptotic Bax, the loss of MMP and activation of caspase-9 and -3. We also found that EESB enhanced the expression of death receptors (DRs) and their associated ligands and induced the activation of caspase-8 and truncation of Bid. In addition, EESB suppressed PI3K/Akt signaling and EESB-induced apoptosis and growth inhibition were further increased by inhibition of PI3K activity.

Conclusions

Our results indicated that the pro-apoptotic effect of EESB was mediated through the activation of DR-mediated intrinsic and mitochondria-mediated extrinsic apoptosis pathways and inhibition of the PI3K/Akt signaling in U937 cells.

LMP2 immunoproteasome promotes lymphocyte survival by degrading apoptotic BH3-only proteins

The role of the immunoproteasome is perceived as confined to adaptive immune responses given its ability to produce peptides ideal for MHC Class-I binding. Here, we demonstrate that the immunoproteasome subunit, LMP2, has functions beyond its immunomodulatory role. Using LMP2-deficient mice, we demonstrate that LMP2 is crucial for lymphocyte development and survival in the periphery. Moreover, LMP2-deficient lymphocytes show impaired degradation of key BH3-only proteins, resulting in elevated levels of pro-apoptotic BIM and increased cell death. Interestingly, LMP2 is the sole immunoproteasome subunit required for BIM degradation. Together, our results suggest LMP2 has important housekeeping functions and represents a viable therapeutic target for cancer.

Evaluation of Efficiency of Modified Polypropylenimine (PPI) with Alkyl Chains as Non-viral Vectors Used in Co-delivery of Doxorubicin and TRAIL Plasmid

In this study, co-delivery system was achieved via plasmid encoding TNF related apoptosis inducing ligand (pTRAIL) and doxorubicin (DOX) using carrier based on polypropylenimine (PPI) modified with 10-bromodecanoic acid. Incorporation of alkylcarboxylate chain to PPIs (G4 and G5) could improve transfection efficiency via overcoming the plasma membrane barrier of the cells and decrease cytotoxicity of PPI. Characterization of fabricated NPs revealed that PPI G5 in which 30% of primary amines were substituted by alkyl carboxylate chain (PPI G5-Alkyl 30%) has higher drug loading as compared to the other formulations. PPI G5-Alkyl 30% indicated a decreased drug release may be due to alkyl chains on the surface of PPI, which serve as an additional hindrance for drug diffusion. In vitro cytotoxicity experiments demonstrated that co-delivery system induced apoptosis of tumor cells more efficiently than each of delivery system alone. Furthermore, these results revealed that our combined delivery platform of pTRAIL and DOX using Alkyl-modified PPI G5 can significantly improve the anti-tumor activity and this strategy might develop a new therapeutic window for cancer treatment.

Bax retrotranslocation potentiates Bcl-xL's antiapoptotic activity and is essential for switch-like transitions between MOMP competency and resistance

The rapid, typically all-or-none process of mitochondrial outer membrane permeabilization (MOMP) constitutes a primary cell death decision that is controlled by the Bcl-2 family interactome. However, how strict all-or-none MOMP decisions are governed by and emanate from the dynamic interplay of pro- and antiapoptotic Bcl-2 family members remains incompletely understood. In particular, it is unclear to which extent the shuttling of Bcl-2 family species between lipid and aqueous phases contributes to regulating MOMP sensitivity. Here, we studied the interplay of tBid, Bax, and Bcl-x_L, using a combined approach of deterministic mathematical modeling and retrospective as well as prospective experimental testing of model predictions. Systems modeling of the tBid–Bax interplay and their fluxes between cytosol and mitochondrial membranes reproduced experimental data on tBid-triggered Bax activation and oligomerization highly accurately. Extending these studies to analyze the cell-protective role of Bcl-x_L strikingly revealed that the activity of Bcl-x_L to retrotranslocate activated Bax from membranes back into the cytosol is essential to reproduce or correctly predict experimental outcomes. These included the potency of Bcl-x_L in suppressing Bax oligomerization, its role in limiting Bax membrane recruitment, the resistance threshold to low concentrations of MOMP triggers as well as a response potentiaton arising from combinations of tBid and sensitizer BH3-only peptides. Importantly, retrotranslocation activity of Bcl-x_L is necessary to strictly separate conditions of MOMP competency and resistance. Our results therefore identify Bax retrotranslocation by Bcl-x_L as an indispensable component of the molecular switch by which Bcl-2 family members govern cellular death decisions.

Local Anesthetics Inhibit the Growth of Human Hepatocellular Carcinoma Cells

BACKGROUND

Hepatocellular carcinoma (HCC) is an aggressive cancer with limited therapeutic options. Retrospective studies have shown that the administration of local anesthetics (LAs) during cancer surgery could reduce cancer recurrence. Besides, experimental studies reported that LAs could inhibit the growth of cancer cells. Thus, the purpose of this study was to investigate the effects of LAs on human HCC cells.

METHODS

The effects of 2 LAs (lidocaine and ropivacaine) (10 to 10 M) were studied after an incubation of 48 hours on 2 HCC cell lines, namely HuH7 and HepaRG. Cell viability, cell cycle analysis, and apoptosis and senescence tests were performed together with unsupervised genome-wide expression profiling and quantitative real-time polymerase chain reaction for relevant genes.

RESULTS

We showed that LAs decreased viability and proliferation of HuH7 cells (from 92% [P < .001] at 5 × 10 M to 40% [P = .02] at 10 M with ropivacaine and from 87% [P < .001] to 37% [P = .02] with lidocaine) and HepaRG progenitor cells (from 58% at 5 × 10 M [P < .001] to 29% at 10 M [P = .04] with lidocaine and 59% [P < .001] with ropivacaine 5 × 10 M) in concentration-dependent manner. LAs have no effect on well-differentiated HepaRG. Ropivacaine decreased the mRNA level of key cell cycle regulators, namely cyclin A2, cyclin B1, cyclin B2, and cyclin-dependent kinase 1, and the expression of the nuclear marker of cell proliferation MKI67. Lidocaine had no specific effect on cell cycle but increased by 10× the mRNA level of adenomatous polyposis coli (P < .01), which acts as an antagonist of the Wnt/β-catenin pathway. Both LAs increased apoptosis in Huh7 and HepaRG progenitor cells (P < .01).

CONCLUSIONS

The data demonstrate that LAs induced profound modifications in gene expression profiles of tumor cells, including modulations in the expression of cell cycle-related genes that result in a cytostatic effect and induction of apoptosis.

Liver cell injury caused by bad habits

Apoptosis and necrosis of liver cells induced by environmental or genetic factors are the main features of liver injury. Liver injury is usually caused by apoptosis of liver cells, which is controlled by a complex regulatory system involved in liver damage and secondary inflammation. This article aims to review liver injury caused by bad habits and the underlying molecular mechanisms.

Cell death at the intestinal epithelial front line

The intestinal epithelium represents the largest epithelial surface in our body. This single-cell-layer epithelium mediates important functions in the absorption of nutrients and in the maintenance of barrier function, preventing luminal microorganisms from invading the body. Due to its constant regeneration the intestinal epithelium is a tissue not only with very high proliferation rates but also with very prominent physiological and pathophysiological cell death induction. The normal physiological differentiation and maturation of intestinal epithelial cells leads to their shedding and apoptotic cell death within a few days, without disturbing the epithelial barrier integrity. In contrast excessive intestinal epithelial cell death induced by irradiation, drugs and inflammation severely impairs the vital functions of this tissue. In this review we discuss cell death processes in the intestinal epithelium in health and disease, with special emphasis on cell death triggered by the tumour necrosis factor receptor family.

Thiazolides promote apoptosis in colorectal tumor cells via MAP kinase-induced Bim and Puma activation

While many anticancer therapies aim to target the death of tumor cells, sophisticated resistance mechanisms in the tumor cells prevent cell death induction. In particular enzymes of the glutathion-S-transferase (GST) family represent a well-known detoxification mechanism, which limit the effect of chemotherapeutic drugs in tumor cells. Specifically, GST of the class P1 (GSTP1-1) is overexpressed in colorectal tumor cells and renders them resistant to various drugs. Thus, GSTP1-1 has become an important therapeutic target. We have recently shown that thiazolides, a novel class of anti-infectious drugs, induce apoptosis in colorectal tumor cells in a GSTP1-1-dependent manner, thereby bypassing this GSTP1-1-mediated drug resistance. In this study we investigated in detail the underlying mechanism of thiazolide-induced apoptosis induction in colorectal tumor cells. Thiazolides induce the activation of p38 and Jun kinase, which is required for thiazolide-induced cell death. Activation of these MAP kinases results in increased expression of the pro-apoptotic Bcl-2 homologs Bim and Puma, which inducibly bind and sequester Mcl-1 and Bcl-x_L leading to the induction of the mitochondrial apoptosis pathway. Of interest, while an increase in intracellular glutathione levels resulted in increased resistance to cisplatin, it sensitized colorectal tumor cells to thiazolide-induced apoptosis by promoting increased Jun kinase activation and Bim induction. Thus, thiazolides may represent an interesting novel class of anti-tumor agents by specifically targeting tumor resistance mechanisms, such as GSTP1-1.

Mitochondrial biology, targets, and drug delivery

In recent years, mitochondrial medicine has emerged as a new discipline resting at the intersection of mitochondrial biology, pathology, and pharmaceutics. The central role of mitochondria in critical cellular processes such as metabolism and apoptosis has placed mitochondria at the forefront of cell science. Advances in mitochondrial biology have revealed that these organelles continually undergo fusion and fission while functioning independently and in complex cellular networks, establishing direct membrane contacts with each other and with other organelles. Understanding the diverse cellular functions of mitochondria has contributed to understanding mitochondrial dysfunction in disease states. Polyplasmy and heteroplasmy contribute to mitochondrial phenotypes and associated dysfunction. Residing at the center of cell biology, cellular functions, and disease pathology and being laden with receptors and targets, mitochondria are beacons for pharmaceutical modification. This review presents the current state of mitochondrial medicine with a focus on mitochondrial function, dysfunction, and common disease; mitochondrial receptors, targets, and substrates; and mitochondrial drug design and drug delivery with a focus on the application of nanotechnology to mitochondrial medicine. Mitochondrial medicine is at the precipice of clinical translation; the objective of this review is to aid in the advancement of mitochondrial medicine from infancy to application.

Platinum(IV) complex LA-12 exerts higher ability than cisplatin to enhance TRAIL-induced cancer cell apoptosis via stimulation of mitochondrial pathway

In search for novel strategies in colon cancer treatment, we investigated the unique ability of platinum(IV) complex LA-12 to efficiently enhance the killing effects of tumor necrosis factor-related apoptosis inducing ligand (TRAIL), and compared it with the sensitizing action of cisplatin. We provide the first evidence that LA-12 primes human colon cancer cells for TRAIL-induced cytotoxicity by p53-independent activation of the mitochondrial apoptotic pathway. The cooperative action of LA-12 and TRAIL was associated with stimulation of Bax/Bak activation, drop of mitochondrial membrane potential, caspase-9 activation, and a shift of the balance among Bcl-2 family proteins in favor of the pro-apoptotic members. In contrast to cisplatin, LA-12 was a potent inducer of ERK-mediated Noxa and BimL protein upregulation, and more effectively enhanced TRAIL-induced apoptosis in the absence of Bax. The cooperative action of LA-12 and TRAIL was augmented following the siRNA-mediated silencing of Mcl-1 in both Bax proficient/deficient cells. We newly demonstrated that LA-12 induced ERK-mediated c-Myc upregulation, and proved that c-Myc silencing inhibited the mitochondrial activation and apoptosis in colon cancer cells treated with LA-12 and TRAIL. The LA-12-mediated sensitization to TRAIL-induced apoptosis was demonstrated in several colon cancer cell lines, further underscoring the general relevance of our findings. The selective action of LA-12 was documented by preferential priming of cancer but not normal colon cancer cells to TRAIL killing effects. Our work highlights the promising potential of LA-12 over cisplatin to enhance the colon cancer cell sensitivity to TRAIL-induced apoptosis, and provides new mechanistic insights into their cooperative action.

JNK1/2 regulate Bid by direct phosphorylation at Thr59 in response to ALDH1L1

BH3 interacting-domain death agonist (Bid) is a BH3-only pro-apoptotic member of the Bcl-2 family of proteins. Its function in apoptosis is associated with the proteolytic cleavage to the truncated form tBid, mainly by caspase-8. tBid translocates to mitochondria and assists Bax and Bak in induction of apoptosis. c-Jun N-terminal kinase (JNK)-dependent alternative processing of Bid to jBid was also reported. We have previously shown that the folate stress enzyme 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) activates JNK1 and JNK2 in cancer cells as a pro-apoptotic response. Here we report that in PC-3 prostate cancer cells, JNK1/2 phosphorylate Bid at Thr59 within the caspase cleavage site in response to ALDH1L1. In vitro, all three JNK isoforms, JNK 1–3, phosphorylated Thr59 of Bid with JNK1 being the least active. Thr59 phosphorylation protected Bid from cleavage by caspase-8, resulting in strong accumulation of the full-length protein and its translocation to mitochondria. Interestingly, although we did not observe jBid in response to ALDH1L1 in PC-3 cells, transient expression of Bid mutants lacking the caspase-8 cleavage site resulted in strong accumulation of jBid. Of note, a T59D mutant mimicking constitutive phosphorylation revealed more profound cleavage of Bid to jBid. JNK-driven Bid accumulation had a pro-apoptotic effect in our study: small interfering RNA silencing of either JNK1/2 or Bid prevented Bid phosphorylation and accumulation, and rescued ALDH1L1-expressing cells. As full-length Bid is a weaker apoptogen than tBid, we propose that the phosphorylation of Bid by JNKs, followed by the accumulation of the full-length protein, delays attainment of apoptosis, and allows the cell to evaluate the stress and make a decision regarding the response strategy. This mechanism perhaps can be modified by the alternative cleavage of phospho-T59 Bid to jBid at some conditions.

Involvement of extrinsic and intrinsic apoptotic pathways together with endoplasmic reticulum stress in cell death induced by naphthylchalcones in a leukemic cell line: advantages of multi-target action

Chalcones, naturally occurring open-chain flavonoids abundant in plants, have demonstrated anticancer activity in multiple tumor cells. In a previous work, the potential anticancer activity of three naphthylchalcones named R7, R13 and R15 was shown. In this study, the mechanism of actions of these chalcones was originally shown. The chalcones presented concentration and time-dependent cytotoxicity. To determine the type of cell death induced by chalcones, we assessed a series of assays including measurements of the caspase-8, -9 and -12 activities, expression of important apoptosis-related genes and proteins, changes in the cell calcium concentration and cytochrome c release. The activities of caspase-8, -9 and -12 increased after the treatment of L1210 cells with the three compounds. Chalcones R7 and R13 induced an increase of pro-apoptotic proteins Bax, Bid and Bak (only chalcone R13), as well as a decrease in anti-apoptotic Bcl-2 expression. These chalcones also induced an increase in Fas and a decrease in p21 and p53 expression. Chalcone R15 seems to act by a different mechanism to promote cell death, as it did not change the mitochondrion-related proteins, nor did it induce the cytochrome c release. All compounds induced an increase in cell calcium concentration and an increase in CHOP expression, which together with an increase in caspase-12 activity, suggest that chalcones could induce an endoplasmic reticulum (ER) stress. Taken together, these results suggest that chalcones induce apoptosis by different pathways, being an interesting strategy to suggest for cancer therapy.

Melatonin induces transcriptional regulation of Bim by FoxO3a in HepG2 cells

Background:

Melatonin induces apoptosis in many different cancer cell lines, including hepatocellular carcinoma cells. However, the responsible pathways have not been clearly elucidated. A member of the forkhead transcription factors' family, FoxO3a, has been implicated in the expression of the proapoptotic protein Bim (a Bcl-2-interacting mediator of cell death). In this study, we used human HepG2 liver cancer cells as an in vitro model to investigate whether melatonin treatment induces Bim through regulation by the transcription factor FoxO3a.

Methods:

Cytotoxicity of melatonin was compared in HepG2 hepatoblastoma cells and primary human hepatocytes. Proapoptotic Bim expression was analysed by reverse transcriptase–polymerase chain reaction and western blot. Reporter gene assays and chromatin immunoprecipitation assays were performed to analyse whether FoxO3a transactivates the Bim promoter. Small interfering RNA (siRNA) was used to study the role of FoxO3a in Bim expression. Immunofluorescence was performed to analyse FoxO3a localisation in HepG2 cells.

Results:

Melatonin treatment induces apoptosis in HepG2 cells, but not in primary human hepatocytes. The proapoptotic effect was mediated by increased expression of the BH3-only protein Bim. During melatonin treatment, we observed increased transcriptional activity of the forkhead-responsive element and could demonstrate that FoxO3a binds to a specific sequence within the Bim promoter. Furthermore, melatonin reduced phosphorylation of FoxO3a at Thr³² and Ser²⁵³, and induced its increased nuclear localisation. Moreover, silencing experiments with FoxO3a siRNA prevented Bim upregulation.

Conclusion:

This study shows that melatonin can induce apoptosis in HepG2 hepatocarcinoma cells through the upregulation of proapoptotic Bim mediated by nuclear translocation and activation of the transcription factor FoxO3a.

Inhibition of MKK7-JNK by the TOR signaling pathway regulator-like protein contributes to resistance of HCC cells to TRAIL-induced apoptosis

BACKGROUND & AIMS

The TOR signaling pathway regulator-like (TIPRL) protein, the mammalian ortholog of yeast TIP41, was identified in an expression profiling screen for factors that regulate human liver carcinogenesis. We investigated the role of human TIPRL protein in hepatocellular carcinoma (HCC).

METHODS

We measured the level of TIPRL in HCC and adjacent nontumor tissues from patients. We used small interfering RNAs and zebrafish to study the function of TIPRL. We used annexin V propidium iodide staining and immunoblot analyses to measure apoptosis and activation of apoptotic signaling pathways. We used confocal microscopy, coimmunoprecipitation, and glutathione-S transferase pull-down analyses to determine interactions among mitogen-activated protein kinase kinase 7 (MKK7 or MAP2K7), TIPRL, and the protein phosphatase type 2A (PP2Ac). We studied the effects of TIPRL in tumor xenografts in mice.

RESULTS

Levels of TIPRL were higher in HCC tissues and cell lines than nontumor tissues and primary hepatocytes. Knockdown of tiprl expression in zebrafish led to large amounts of apoptosis throughout the embryos. Incubation of HCC cells, but not primary human hepatocytes, with small interfering RNA against TIPRL (siTIPRL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) caused prolonged activation (phosphorylation) of MKK7 and c-Jun N-terminal kinase (JNK) and led to apoptosis, indicated by cleavage of procaspase-8,-3 and of poly-(adenosine diphosphate-ribose) polymerase. TIPRL bound to MKK7 and PP2Ac and promoted the interaction between MKK7 and PP2Ac. In mice, injection of HCC xenograft tumors with siTIPRL and TRAIL led to tumor apoptosis and regression.

CONCLUSIONS

TIPRL is highly up-regulated in human HCC samples and cell lines, compared with noncancerous liver tissues. TIPRL prevents prolonged activation of MKK7 and JNK and TRAIL-induced apoptosis by mediating the interaction between MKK7 and PP2Ac.

Dacarbazine and the agonistic TRAIL receptor-2 antibody lexatumumab induce synergistic anticancer effects in melanoma

Mapatumumab and lexatumumab (targeting death receptor 4 (DR4) and 5 (DR5), respectively) are agonistic TRAIL receptor antibodies that induce apoptosis in a wide range of cancer cells. The potency of mapatumumab and lexatumumab was assessed in mono therapy protocols, and the ability to sensitize for dacarbazine (DTIC) treatment was explored in ten different melanoma cell lines. Our data indicated that melanoma cell lines tend to be resistant to mapatumumab, most likely due to low expression of DR4, while a dose dependent response to lexatumumab was observed. Combining DTIC and lexatumumab induced an additive or synergistic effect on cell death in the various melanoma cell lines. The synergistic effect observed in the FEMX-1 cell line was related to enhanced cleavage of Bid in parallel with elevated expression of the pro-apoptotic proteins Bim, Bax and Bak. Furthermore, the anti-apoptotic proteins Bcl-XL, cIAP-1, XIAP and livin were down regulated. Cleavage of Bid and down regulation of cIAP-2 and livin were observed in vivo. Altogether, these data suggest a change in the balance between pro- and anti-apoptotic proteins favoring induction of apoptosis. In the more therapy resistant cell line, HHMS, no changes in the pro- and anti-apoptotic proteins were observed. FEMX-1 xenografts treated with DTIC and lexatumumab showed reduced growth and increased level of apoptosis compared to the control groups, providing arguments for further evaluation of this combination in melanoma patients.

Caloric restriction: is mammalian life extension linked to p53?

Caloric restriction, that is limiting food intake, is recognized in mammals as the best characterized and most reproducible strategy for extending lifespan, retarding physiological aging and delaying the onset of age-associated diseases. The aim of this mini review is to argue that p53 is the connection in the abilities of both the Sirt-1 pathway and the TOR pathway to impact on longevity of cells and organisms. This novel, lifespan regulating function of p53 may be evolutionarily more ancient than its relatively recent role in apoptosis and tumour suppression, and is likely to provide many new insights into lifespan modulation.

Oleifolioside A mediates caspase-independent human cervical carcinoma HeLa cell apoptosis involving nuclear relocation of mitochondrial apoptogenic factors AIF and EndoG

Apoptosis, the main type of programmed cell death, plays an essential role in a variety of biological events. Whereas "classical" apoptosis is dependent on caspase activation, caspase-independent death is increasingly recognized as an alternative pathway. To develop new anticancer agents, oleifolioside A was isolated from Dendropanax morbifera Leveille and the biochemical mechanisms of oleifolioside A-induced apoptosis in HeLa cells were investigated. Exposure to oleifolioside A resulted in caspase activation and typical features of apoptosis, although cell death was not prevented by caspase inhibition. Oleifolioside A treatment induced up-regulation of Bad, loss of mitochondrial membrane potential, nuclear relocation of mitochondrial factors, apoptosis-inducing factor (AIF), endonuclease G (EndoG), and apoptosis induction. This is the first report of anticancer activity of oleifolioside A, and nuclear translocation of AIF and EndoG in oleifolioside A-treated HeLa cells might represent an alternative death signaling pathway in the absence of caspase activity.

Hormesis, cell death and aging

Frequently, low doses of toxins and other stressors not only are harmless but also activate an adaptive stress response that raise the resistance of the organism against high doses of the same agent. This phenomenon, which is known as "hormesis", is best represented by ischemic preconditioning, the situation in which short ischemic episodes protect the brain and the heart against prolonged shortage of oxygen and nutrients. Many molecules that cause cell death also elicit autophagy, a cytoprotective mechanism relying on the digestion of potentially harmful intracellular structures, notably mitochondria. When high doses of these agents are employed, cells undergo mitochondrial outer membrane permeabilization and die. In contrast, low doses of such cytotoxic agents can activate hormesis in several paradigms, and this may explain the lifespan-prolonging potential of autophagy inducers including resveratrol and caloric restriction.

Role of the promyelocytic leukaemia protein in cell death regulation

The promyelocytic leukaemia gene PML was originally identified at the t(15;17) translocation of acute promyelocytic leukaemia, which generates the oncogene PML-retinoic acid receptor α. PML epitomises a subnuclear structure called PML nuclear body. Current models propose that PML through its scaffold properties is able to control cell growth and survival at many different levels. Here we discuss the current literature and propose new avenues for investigation.

Thiazolide-induced apoptosis in colorectal cancer cells is mediated via the Jun kinase-Bim axis and reveals glutathione-S-transferase P1 as Achilles' heel

Glutathione-S-transferase of the Pi class (GSTP1) is frequently overexpressed in a variety of solid tumors and has been identified as a potential therapeutic target for cancer therapy. GSTP1 is a phase II detoxification enzyme and conjugates the tripeptide glutathione to endogenous metabolites and xenobiotics, thereby limiting the efficacy of antitumor chemotherapeutic treatments. In addition, GSTP1 regulates cellular stress responses and apoptosis by sequestering and inactivating c-Jun N-terminal kinase (JNK). Thiazolides are a novel class of antibiotics for the treatment of intestinal pathogens with no apparent side effects on the host cells and tissue. Here we show that thiazolides induce a GSTP1-dependent and glutathione-enhanced cell death in colorectal tumor cell lines. Downregulation of GSTP1 reduced the apoptotic activity of thiazolides, whereas overexpression enhanced it. Thiazolide treatment caused strong Jun kinase activation and Jun kinase-dependent apoptosis. As a critical downstream target of Jun kinase we identified the pro-apoptotic Bcl-2 homolog Bim. Thiazolides induced Bim expression and activation in a JNK-dependent manner. Downregulation of Bim in turn significantly blocked thiazolide-induced apoptosis. Whereas low concentrations of thiazolides failed to induce apoptosis directly, they potently sensitized colon cancer cells to TNF-related apoptosis-inducing ligand- and chemotherapeutic drug-induced cell death. Although GSTP1 overexpression generally limits chemotherapy and thus antitumor treatment, our study identifies GSTP1 as Achilles' heel and thiazolides as novel interesting apoptosis sensitizer for the treatment of colorectal tumors.

The proapoptotic Bcl-2 family member Bim plays a central role during the development of virus-induced hepatitis

The proapoptotic Bcl-2 homolog Bim was shown to control the apoptosis of both T cells and hepatocytes. This dual role of Bim might be particularly relevant for the development of viral hepatitis, in which both the sensitivity of hepatocytes to apoptosis stimuli and the persistence of cytotoxic T cells are essential factors for the outcome of the disease. The relevance of Bim in regulating survival of cytotoxic T cells or induction of hepatocyte death has only been investigated in separate systems, and their relative contributions to the pathogenesis of T cell-mediated hepatitis remain unclear. Using the highly dynamic model system of lymphocytic choriomeningitis virus-mediated hepatitis and bone marrow chimeras, we found that Bim has a dual role in the development of lymphocytic choriomeningitis virus-induced, T cell-mediated hepatitis. Although the absence of Bim in parenchymal cells led to markedly attenuated liver damage, loss of Bim in the lymphoid compartment moderately enhanced hepatitis. However, when both effects were combined in Bim(-/-) mice, the effect of Bim deficiency in the lymphoid compartment was overcompensated for by the reduced sensitivity of Bim(-/-) hepatocytes to T cell-induced apoptosis, resulting in the protection of Bim(-/-) mice from hepatitis.

TRAIL dependent fratricidal killing of gp120 primed hepatocytes by HCV core expressing hepatocytes

The mechanism by which HIV and HCV cooperatively accelerate hepatocyte damage is not clearly understood; however, each virus affects the TRAIL: TRAIL-receptor system. We, therefore, questioned whether the independent effects of HCV and HIV combine to synergistically result in TRAIL dependent hepatocyte killing. We describe that Huh7 hepatocytes treated with HIV gp120 results in both increase TRAIL-R2 expression and an acquired sensitivity to TRAIL mediated killing. Moreover HCV infection and HCV core expression alone in Huh7 cells upregulates TRAIL. Co-incubation of HIV gp120 primed hepatocytes with HCV core expressing hepatocytes results in the selective death of the HIV gp120 primed hepatocytes that is selectively blocked by TRAIL-R2-Fc fusion protein. Liver biopsies from HIV mono-infected patients have increased TRAIL-R2; biopsies from HCV infected patients have increased TRAIL, while co-infected liver biopsies have increased PARP cleavage within hepatocytes indicating enhanced apoptosis. These findings suggest a pathogenic model to understand why HIV/HCV co-infection accelerates liver injury.

Cell death pathology: the war against cancer

Programmed cell death was a fundamental discovery, awarded with the Nobel price in 2002 to Sulston, Brenner and Horvitz. Since then it has been clear that alteration of apoptotic pathways is a common feature of tumors, enabling cancer cells to survive chemotherapeutic interventions. Thus, apoptosis is an attractive target in cancer therapy, with the aim to revert the cancer-related alterations of the cell death machinery. Here, we overview the fundamental apoptotic pathways and summarize the attempts to target apoptosis to restore cell death in cancer cells with a special focus on the p53-family and autophagy.

Cell death pathology: cross-talk with autophagy and its clinical implications

Autophagy is a self-digesting mechanism that cells adopt to respond to stressful stimuli. Morphologically, cells dying by autophagy show multiple cytoplasmic double-membraned vacuoles, and, if prolonged, autophagy can lead to cell death, "autophagic cell death". Thus, autophagy can act both as a temporary protective mechanism during a brief stressful episode and be a mode of cell death in its own right. In this mini-review we focus on recent knowledge concerning the connection between autophagy and programmed cell death, evaluating their possible implications for therapy in pathologies like cancer and neurodegeneration.

Cell death in disease: from 2010 onwards

The strong interest in cell death, and the shift in emphasis from basic mechanisms to translational aspects fostered the launch last year of the new sister journal of Cell Death and Differentiation, named Cell Death and Disease, to reflect its stronger focus towards clinical applications. Here, we review that first year of activity, which reflects an enthusiastic response by the scientific community. On the basis of this, we now launch two novel initiatives, the start of a new section dedicated to cancer metabolism and the opening of a new editorial office in Shanghai.

Apoptosis: why and how does it occur in biology?

The literature on apoptosis has grown tremendously in recent years, and the mechanisms that are involved in this programmed cell death pathway have been enlightened. It is now known that apoptosis takes place starting from early development to adult stage for the homeostasis of multicellular organisms, during disease development and in response to different stimuli in many different systems. In this review, we attempted to summarize the current knowledge on the circumstances and the mechanisms that lead to induction of apoptosis, while going over the molecular details of the modulator and mediators of apoptosis as well as drawing the lines between programmed and non-programmed cell death pathways. The review will particularly focus on Bcl-2 family proteins, the role of different caspases in the process of apoptosis, and their inhibitors as well as the importance of apoptosis during different disease states. Understanding the molecular mechanisms involved in apoptosis better will make a big impact on human diseases, particularly cancer, and its management in the clinics.

BBC3 (PUMA) regulates developmental apoptosis but not axonal injury induced death in the retina

BACKGROUND

Naturally occurring apoptosis is a developmental process that shapes the retina by eliminating overproduced neurons. In the absence of the proapoptotic Bcl-2 family member BAX, developmental apoptosis in the retina is disrupted and extra neurons survive. It is unknown how BAX is activated or if this regulation varies between neuronal types and subtypes. Since the Bcl-2 family members BIM, BID, and BBC3 (PUMA) are powerful direct activators of BAX, we used mice deficient for each of these genes to investigate their importance in developmental apoptosis.

RESULTS

Bax deficient mice have an increase in retinal ganglion cells (RGCs), bipolar cells and dopaminergic amacrine cells, but not photoreceptors, horizontal cells or cholinergic amacrine cells. The retinas of adult Bim and Bid deficient mice appeared to have no increase in any retinal cell type. Bbc3 deficient mice, either homozygous or heterozygous for a null allele of Bbc3, had an increase in the same cell types as Bax deficient mice. An analogous result may occur in the brain where, similar to Bax deficient mice, Bbc3 deficient mice have a larger gross brain weight compared to wild type mice. In contrast to its developmental role, BBC3 did not appear to be a primary factor in BAX-dependent axonal injury induced neurodegeneration in adult RGCs.

CONCLUSION

The regulation of BAX activation in the retina appears to be complex, dependent on the developmental stage of the animal, the nature of the insult and even the type of neuron.