Synergistic induction of tumor cell apoptosis by death receptor antibody and chemotherapy agent through JNK/p38 and mitochondrial death pathway

Acquired Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) Resistance of Human Colorectal Cancer Cells Is Linked to Histone Acetylation and Is Synergistically Ameliorated by Combination with HDAC Inhibitors

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an attractive target for the treatment of various malignancies; however, its therapeutic potential is limited because of the frequent occurrence of tumor cell resistance. In this study, we determined whether TRAIL resistance acquired by repeated administration could be overcome by HDAC inhibition in human colorectal cancer cells.

METHODS

TRAIL-resistant HCT116 human colorectal cancer cells (HCT116-TR) were generated by repeated treatment with 10 and 25 ng/mL TRAIL twice weekly for 28 days.

RESULTS

The resulting TRAIL-resistant cells were noncross-resistant to other chemotherapeutic agents. The levels of histone acetylation-related proteins, such as ac-histone H4 and HDAC1, were altered in HCT116-TR cells compared with the parental HCT116 cell line. The combined treatment with TRAIL and HDAC inhibitors significantly increased apoptosis in HCT116-TR cells and indicated a synergistic effect. The mechanism by which HDAC inhibition sensitizes HCT116-TR cells to TRAIL is dependent on the intrinsic pathway. In addition, we found that HDAC inhibition enhanced the sensitivity of cells to TRAIL through mitogen-activated protein kinases/CCAAT/enhancer-binding protein homologs of protein-dependent upregulation of death receptor 5.

CONCLUSION

These results suggest that histone acetylation is responsible for acquired TRAIL resistance after repeated exposure and acquired resistance to TRAIL may be overcome by combination therapies with HDAC inhibitors.

PEG-lipid-modified agonistic antibody against tumor necrosis factor receptor family elicits superior apoptosis-inducing activity against human carcinoma

We have recently developed a novel PEG-lipid-modified antibody to enhance the induction of apoptosis by the agonistic antibody. The chemically modified TRA-8 antibody [anti-death receptor 5 (DR5) antibody] with PEG-lipid (DSPE-PEG) demonstrated significant cytotoxic activity in vitro without the need for crosslinking with a secondary antibody, which is typically required. We investigated the correlation between the PEG-lipid structure and the cytotoxic activity of the modified antibodies by varying the PEG length or lipid structure. However, when the DSPE-PEG-modified TRA-8 antibody was incubated with plasma, it lost its cytotoxic activity, likely due to degradation in the DSPE-PEG component. Nevertheless, by designing new PEG-lipids that are intended to be resistant to enzymatic degradation, we were able to prevent this degradation and restore the cytotoxic activity of the modified antibody. These findings provide valuable insights for the design of PEG-lipid-modified antibodies and suggest their potential effectiveness in enhancing cancer therapy.

Metastasis suppressor genes in clinical practice: are they druggable?

Since the identification of NM23 (now called NME1) as the first metastasis suppressor gene (MSG), a small number of other gene products and non-coding RNAs have been identified that suppress specific parameters of the metastatic cascade, yet which have little or no ability to regulate primary tumor initiation or maintenance. MSG can regulate various pathways or cell biological functions such as those controlling mitogen-activated protein kinase pathway mediators, cell-cell and cell-extracellular matrix protein adhesion, cytoskeletal architecture, G-protein-coupled receptors, apoptosis, and transcriptional complexes. One defining facet of this gene class is that their expression is typically downregulated, not mutated, in metastasis, such that any effective therapeutic intervention would involve their re-expression. This review will address the therapeutic targeting of MSG, once thought to be a daunting task only facilitated by ectopically re-expressing MSG in metastatic cells in vivo. Examples will be cited of attempts to identify actionable oncogenic pathways that might suppress the formation or progression of metastases through the re-expression of specific metastasis suppressors.

The Lack of Standardization and Pharmacological Effect Limits the Potential Clinical Usefulness of Phytosterols in Benign Prostatic Hyperplasia

The prevalence of benign prostatic hyperplasia (BPH) markedly increases with age. Phytotherapeutic approaches have been developed over time owing to the adverse side effects of conventional medications such as 5-reductase inhibitors and α1-adrenergic receptor antagonists. Therefore, dietary supplements (DS) containing active compounds that benefit BPH are widely available. Phytosterols (PSs) are well recognized for their role in maintaining blood cholesterol levels; however, their potential in BPH treatment remains unexplored. This review aims to provide a general overview of the available data regarding the clinical evidence and a good understanding of the detailed pharmacological roles of PSs-induced activities at a molecular level in BPH. Furthermore, we will explore the authenticity of PSs content in DS used by patients with BPH compared to the current legislation and appropriate analytical methods for tracking DS containing PSs. The results showed that PSs might be a useful pharmacological treatment option for men with mild to moderate BPH, but the lack of standardized extracts linked with the regulation of DS containing PSs and experimental evidence to elucidate the mechanisms of action limit the use of PSs in BPH. Moreover, the results suggest multiple research directions in this field.

Ephedra herb reduces adriamycin-induced testicular toxicity by upregulating the gonadotropin-releasing hormone signalling pathway

OBJECTIVE

We investigated the protective effects of ephedra herb (HEPH) on adriamycin-induced testicular toxicity in rats and explored the potential mechanisms underlying these effects.

METHODS

A rat model of adriamycin injury was established, and sperm motility-related indicator and oxidative stress levels in the testis were evaluated. Serum levels of sex hormones and levels of testicular cell apoptosis were detected by enzyme-linked immunosorbent assay and flow cytometry, respectively. Western blotting (WB), immunofluorescence analyses, and reverse transcription-polymerase chain reaction (RT-PCR) were performed to evaluate the gonadotropin-releasing hormone (GnRH) signalling pathway- and meiosis-related genes and proteins. In subsequent in vitro experiments, adriamycin was used to stimulate GC-1 cells, which were treated with HEPH, ephedrine, or pseudoephedrine. Cell viability was assessed using flow cytometry to detect apoptosis and reactive oxygen species, whereas the GnRH signalling pathway and levels of meiosis-related genes and proteins were evaluated by InCell WB, a high-content imaging system, and RT-PCR.

RESULTS

Per in vivo experiments, HEPH restored testicular weight and function, sperm characteristics, serum and tissue hormonal levels, and antioxidant defences and significantly activated the GnRH signalling pathway- and meiosis-related protein levels. All protective effects of HEPH against adriamycin-induced injury were antagonised by the GnRH antagonist cetrorelix. In vitro, HEPH, ephedrine, and pseudoephedrine significantly reduced adriamycin-induced GC-1 cell apoptosis and reactive oxygen species levels and increased the expression of GnRH signalling pathway- and meiosis-related proteins. The effect of pseudoephedrine was greater than that of ephedrine, and these findings may be an important basis for understanding the effects of HEPH.

Atractylenolide III induces apoptosis by regulating the Bax/Bcl-2 signaling pathway in human colorectal cancer HCT-116 Cells in vitro and in vivo

Atractylodes is the dry root of atractylodes macrocephala koidz and has been commonly used as a traditional Chinese medicine (TCM). Atractylenolide III, a main component of atractylodes, has displayed significant effects on anti-inflammation and anticancer. However, the effects of atractylenolide III on growth inhibition and apoptosis induction in colon cancer remain unclear. The results showed that atractylenolide III significantly inhibited the cell growth and induce cellular apoptosis in HCT-116 cells in a concentration dependence manner in vitro. Mechanistic studies further showed that atractylenolide III could regulate the Bax/Bcl-2 apoptotic signaling pathway through promoting the expression of proapoptotic related gene/proteins Bax, caspase-9 and caspase-3 but inhibiting the expression of antiapoptotic related gene/protein Bcl-2 in HCT-116 cells. Furthermore, atractylenolide III also significantly inhibited the tumor growth of HCT-116 tumor xenografts bearing in nude mice through inducing apoptosis by upregulation of the expressions of Bax, cleaved caspase-3 and p53 but downregulation of the expressions of Bcl-2 in HCT-116 tumor tissues in vivo. The studies may provide the scientific rationale for the understanding of the anticancer effect of atractylenolide III. Therefore, atractylenolide III may have the potential to be developed as a promising novel anticancer agent for the treatment of colorectal cancer clinically.

Dichloromethane fractions of Calystegia soldanella induce S‑phase arrest and apoptosis in HT‑29 human colorectal cancer cells

Calystegia soldanella is a halophyte and a perennial herb that grows on coastal sand dunes worldwide. Extracts from this plant have been previously revealed to have a variety of bioactive properties in humans. However, their effects on colorectal cancer cells remain poorly understood. In the present study, the potential biological activity of C. soldanella extracts in the colorectal cancer cell line HT-29 was examined. First, five solvent fractions [n-hexane, dichloromethane (DCM), ethyl acetate, n-butanol and water] were obtained from the crude extracts of C. soldanella through an organic solvent extraction method. In particular, the DCM fraction was demonstrated to exert marked dose- and time-dependent inhibitory effects according to results from the cell viability assay. Data obtained from the apoptosis assay suggested that the inhibition of HT-29 cell viability induced by DCM treatment was attributed to increased apoptosis. The apoptotic rate was markedly increased in a dose-dependent manner, which was associated with the protein expression levels of apoptosis-related proteins, including increased Fas, Bad and Bax, and decreased pro-caspase-8, Bcl-2, Bcl-xL, pro-caspase-9, pro-caspase-7 and pro-caspase-3. A mitochondrial membrane potential assay demonstrated that more cells became depolarized and the extent of cytochrome c release was markedly increased in a dose-dependent manner in HT-29 cells treated with DCM. In addition, cell cycle analysis confirmed S-phase arrest following DCM fraction treatment, which was associated with decreased protein expression levels of cell cycle-related proteins, such as cyclin A, CDK2, cell division cycle 25 A and cyclin dependent kinase inhibitor 1. Based on these results, the present study suggested that the DCM fraction of the C. soldanella extract can inhibit HT-29 cell viability whilst inducing apoptosis through mitochondrial membrane potential regulation and S-phase arrest. These results also suggested that the DCM fraction has potential anticancer activity in HT-29 colorectal cells. Further research on the composition of the DCM fraction is warranted.

Chemotherapy-induced cognitive impairment: focus on the intersection of oxidative stress and TNFα

Chemotherapy-induced cognitive impairment (CICI) has been observed in a large fraction of cancer survivors. Although many of the chemotherapeutic drugs do not cross the blood-brain barrier, following treatment, the structure and function of the brain are altered and cognitive dysfunction occurs in a significant number of cancer survivors. The means by which CICI occurs is becoming better understood, but there still remain unsolved questions of the mechanisms involved. The hypotheses to explain CICI are numerous. More than 50% of FDA-approved cancer chemotherapy agents are associated with reactive oxygen species (ROS) that lead to oxidative stress and activate a myriad of pathways as well as inhibit pathways necessary for proper brain function. Oxidative stress triggers the activation of different proteins, one in particular is tumor necrosis factor alpha (TNFα). Following treatment with various chemotherapy agents, this pro-inflammatory cytokine binds to its receptors at the blood-brain barrier and translocates to the parenchyma via receptor-mediated endocytosis. Once in brain, TNFα initiates pathways that may eventually lead to neuronal death and ultimately cognitive impairment. TNFα activation of the c-jun N-terminal kinases (JNK) and Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathways may contribute to both memory decline and loss of higher executive functions reported in patients after chemotherapy treatment. Chemotherapy also affects the brain's antioxidant capacity, allowing for accumulation of ROS. This review expands on these topics to provide insights into the possible mechanisms by which the intersection of oxidative stress and TNFΑ are involved in chemotherapy-induced cognitive impairment.

DUSP16 promotes cancer chemoresistance through regulation of mitochondria-mediated cell death

Drug resistance is a major obstacle to the treatment of most human tumors. In this study, we find that dual-specificity phosphatase 16 (DUSP16) regulates resistance to chemotherapy in nasopharyngeal carcinoma, colorectal cancer, gastric and breast cancer. Cancer cells expressing higher DUSP16 are intrinsically more resistant to chemotherapy-induced cell death than cells with lower DUSP16 expression. Overexpression of DUSP16 in cancer cells leads to increased resistance to cell death upon chemotherapy treatment. In contrast, knockdown of DUSP16 in cancer cells increases their sensitivity to treatment. Mechanistically, DUSP16 inhibits JNK and p38 activation, thereby reducing BAX accumulation in mitochondria to reduce apoptosis. Analysis of patient survival in head & neck cancer and breast cancer patient cohorts supports DUSP16 as a marker for sensitivity to chemotherapy and therapeutic outcome. This study therefore identifies DUSP16 as a prognostic marker for the efficacy of chemotherapy, and as a therapeutic target for overcoming chemoresistance in cancer.

Increased Reactive Oxygen Species and Distinct Oxidative Damage in Resveratrol-suppressed Glioblastoma Cells

Background and Aim: Glioblastoma multiforme (GBM) is a highly aggressive brain malignancy that lacks reliable treatments. Resveratrol possesses anti-cancer effects, but its activity against glioblastoma cells is variable for unknown reasons. One mechanism through which anti-cancer drugs exert their effects is oxidative damage caused by increased reactive oxygen species (ROS) production. Thus, the present study examined the relationship between oxidative stress and sensitivity to resveratrol in glioblastoma cells.

Methods: Two GBM cell lines (U251 and LN428) were exposed to 100 μM resveratrol for 48 h, and proliferation and apoptosis were assessed. ROS generation was evaluated using 2′-7′-dichlorodihydrofluorescein diacetate-based flow cytometry and fluorescent microscopy. Immunocytochemical staining and western blotting were conducted at regular intervals to profile the expression patterns of superoxide dismutase-2 (SOD2), catalase, caspase-9, caspase-3, and sulfotransferases (SULTs) in untreated and resveratrol-treated GBM cells.

Results: Resveratrol-treated U251 cells, but not resveratrol-treated LN428 cells, exhibited remarkable growth arrest and extensive apoptosis accompanied by elevated intracellular ROS levels and attenuated SOD2 and catalase expression. Mitochondrial impairment and more distinct increases in the expression of activated caspase-9 and caspase-3 were detected in U251 cells following resveratrol treatment. The levels of resveratrol metabolic enzymes (SULT1A1 and SULT1C2) were lower in U251 cells than in LN428 cells.

Conclusions: Resveratrol increased ROS generation and induced oxidation-related cellular lesions in U251 cells by activating an ROS-related mitochondrial signal pathway. The levels of SULTs and ROS may indicate the therapeutic outcomes of resveratrol treatment in GBM.

Matrilin-2 prevents the TNFα-induced apoptosis of WB-F344 cells via suppressing JNK pathway

Oval cells, a kind of hepatic progenitor cell quiescent at normal condition, activates to proliferate and differentiate into hepatocytes under severe and long-term liver injury, which usually raises severe inflammation. However, how oval cell survives in the inflammatory milieu interne is still unclear. Tumor necrosis factor α (TNFα), mimicking inflammatory hepatic milieu interne, was used to treat oval cell line, WB-F344, to test the protective function of matrilin-2. In this study, our data suggested that matrilin-2 prevented TNFα-induced apoptosis in WB-F344 cells via inhibiting ASK1/MKK7/JNK pathway. In conclusion, we determined that matrilin-2 plays the key role in maintaining the survival of oval cell and guarantees its proliferation under various injury factors.

Erianin, a novel dibenzyl compound in Dendrobium extract, inhibits bladder cancer cell growth via the mitochondrial apoptosis and JNK pathways

Erianin, a component extracted from the traditional Chinese herbal medicine Dendrobium, has shown significant anti-tumour activity in various cancers but not in bladder cancer. In this study, we assessed the effects of Erianin on bladder cancer growth and elucidated the related mechanisms. First, Erianin was synthesized with high yields, and markedly suppressed EJ and T24 cell proliferation. It induced G2/M-phase arrest in vitro. Furthermore, Erianin triggered apoptosis via caspase cascades activation and the mitochondrial-mediated apoptotic pathway. Bim up-regulation and Bcl-2 down-regulation as the symbol of apoptosis which were found to play the dominant role in the effects of Erianin. We further showed that JNK pathway activation is necessary for the Erianin-mediated anti-proliferation and apoptotic response. Finally, Erianin exhibited anti-tumour activity and induced apoptosis in tumour tissue in vivo. Collectively, these results suggest that Erianin induced cell cycle G2/M-phase arrest and apoptosis via the JNK signalling pathway in bladder cancer, indicating the potential usefulness of Erianin for the therapy of bladder cancer.

Pharmacological levels of hydrogen sulfide inhibit oxidative cell injury through regulating the redox state of thioredoxin

Hydrogen sulfide (H₂S) is a gaseous mediator with multifaceted biological activities. It has anti-inflammatory and anti-oxidative effects. Currently, the mechanisms are not fully understood. Given that Trx/ASK1/P38 signaling pathway mediates many oxidative cell responses, we tested whether and how H₂S affected this pathway. Exposure of podocytes to Adriamycin (ADR), an antitumor drug, led to a P38-mediated oxidative cell injury, as evidenced by the increased protein carbonylation, oxidative activation of P38, and prevention of the cell death by antioxidants, NADPH oxidase inhibitor and P38 inhibitor. In the presence of H₂S donor NaHS, however, the podocyte injury was largely prevented. NaHS also significantly prevented cell death elicited by H₂O₂, menadione, and thioredoxin (Trx) inhibitors. These effects of H₂S were also associated with a potent inhibition of P38. Further analysis revealed that H₂S did not affect the protein level of TXNIP and Trx, two pivotal regulators of ASK1/P38 activation, but it promoted the dissociation of Trx from TXNIP. Moreover, it disrupted the H₂O₂-initiated polymerization of Trx and converted Trx from the oxidized to the reduced form. In HepG2 cells, inhibition of H₂S-producing enzyme cystathionine γ-lyase (CSE) increased Trx oxidation, promoted Trx binding to TXNIP and exaggerated cell injury caused by Trx inhibition. Collectively, our results indicate that H₂S exerted its antioxidative effects through the regulation of the redox state of Trx and interference with Trx/ASK1/P38 signaling pathway. Given the importance of the pathway in the mediation of multiple oxidative cell responses, our study thus provides novel mechanistic insight into the action of H₂S.

Lipocalin 2 inversely regulates TRAIL sensitivity through p38 MAPK-mediated DR5 regulation in colorectal cancer

TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis through death receptors (DRs)4 and/or 5 expressed on the cell surface. Multiple clinical trials are underway to evaluate the antitumor activity of recombinant human TRAIL and agonistic antibodies to DR4 or DR5. However, their therapeutic potential is limited by the high frequency of cancer resistance. In this study, we provide evidence demonstrating the role of lipocalin 2 (LCN2) in the TRAIL-mediated apoptosis of human colorectal cancer (CRC). By analyzing the mRNA expression data of 71 CRC tissues from patients, we found that DR5 was preferentially expressed in CRC tissues with a low LCN2 expression level compared to tissues with a high LCN2 expression level. Moreover, we analyzed the association between DR5 and LCN2 expression and this analysis revealed that DR5 expression in CRC tended to be inversely associated with LCN2 expression. By contrast, no association was found between the DR4 and LCN2 expression levels. The expression patterns of LCN2 in human CRC cell lines also exhibited an inverse association with DR5 expression. The knockdown of LCN2 by siRNA in the TRAIL‑resistant CRC cells expressing high levels of LCN2 led to a significant increase in TRAIL-induced apoptosis through the upregulation of DR5 protein and mRNA expression. The mechanism through which LCN2 silencing sensitized the CRC cells to TRAIL was dependent on the extrinsic pathway of apoptosis. In addition, we identified that the knockdown of LCN2 enhanced the sensitivity of the cells to TRAIL through the p38 MAPK/CHOP-dependent upregulation of DR5. Taken together, the findings of this study suggest that LCN2 is responsible for TRAIL sensitivity and LCN2 may thus prove to be a promising target protein in DR-targeted CRC therapy.

Novel Immunoliposome Technology for Enhancing the Activity of the Agonistic Antibody against the Tumor Necrosis Factor Receptor Superfamily

We have developed a technology for efficiently enhancing the anticancer apoptosis-inducing activity of agonistic antibodies against the tumor necrosis factor receptor (TNFR) superfamily by the formation of immunoliposomes. To induce apoptosis in cancer cells, agonistic antibodies to the TNFR superfamily normally need cross-linking by internal immune effector cells via the Fc region after binding to receptors on the cell membrane. To develop apoptosis-inducing antibodies that do not require the support of cross-linking by immune cells, we prepared immunoliposomes conjugated with TRA-8, an agonistic antibody against death receptor 5 (DR5), with various densities of antibody on the liposome surface, and evaluated their activities. The TRA-8 immunoliposomes exhibited apoptosis-inducing activity against various DR5-positive human carcinoma cells at a significantly lower concentration without cross-linking than that of the original TRA-8 and its natural ligand (TRAIL). The activity of the immunoliposomes was correlated with the density of antibodies on the surface. As the antibody component, not only the full-length antibody but also the Fab' fragment could be used, and the TRA-8 Fab' immunoliposomes also showed exceedingly high activity compared with the parental antibody, namely, TRA-8. Moreover, cytotoxicity of the TRA-8 full-length or Fab' immunoliposome against normal cells, such as human primary hepatocytes, was lower than that for TRAIL. Enhanced activity was also observed for immunoliposomes conjugated with other apoptosis-inducing antibodies against other receptors of the TNFR superfamily, such as death receptor 4 (DR4) and Fas. Thus, immunoliposomes are promising as a new modality that could exhibit significant activity at a low dose, for cost-effective application of an antibody fragment and with stable efficacy independent of the intratumoral environment of patients as a TNF superfamily agonistic therapy.

Enhancement of death receptor 4-mediated apoptosis and cytotoxicity in renal cell carcinoma cells by anisomycin

Renal cell carcinoma (RCC) is one of the most drug-resistant malignancies, and an effective therapy is lacking for metastatic RCC. Anisomycin is known to inhibit protein synthesis and induce ribotoxic stress. The aim of this study was to explore whether anisomycin enhances the cytotoxic effects of mapatumumab, a human agonistic monoclonal antibody specific for death receptor 4 (DR4), in human RCC cells. We examined the cytotoxicity of anisomycin alone and in combination with mapatumumab in human RCC cell lines and primary RCC cell cultures. RCC cells treated with anisomycin showed cytotoxicity in a dose-dependent manner. Anisomyin in combination with mapatumumab showed a synergistic effect not only in two human RCC cell lines but also in five primary RCC cell cultures. The synergy between anisomycin and mapatumumab for cytotoxicity was also observed for apoptosis. Interestingly, anisomycin significantly increased DR4 expression at both the mRNA and the protein level. Furthermore, the combination-induced cytotoxicity was significantly suppressed by a human recombinant DR4:Fc chimeric protein. The combination of anisomycin and mapatumumab also enhanced the activity of caspases 8 and 3, the downstream molecules of death receptors. These findings indicate that anisomycin sensitizes RCC cells to DR4-mediated apoptosis through the induction of DR4, suggesting that combinational treatment with anisomycin and mapatumumab might represent a novel therapeutic strategy for the treatment of RCC.

Neuroprotective Effect of Nanodiamond in Alzheimer's Disease Rat Model: a Pivotal Role for Modulating NF-κB and STAT3 Signaling

Current therapeutic approaches of Alzheimer's disease (AD) are symptomatic and of modest efficacy, and there is no available effective cure or prevention of AD; hence, the need arise to search for neuroprotective agents to combat AD. The current study aimed at investigating the neuroprotective effect of nanodiamond (ND), adamantine-based nanoparticles, in aluminum-induced cognitive impairment in rats, an experimental model of AD. AD was induced by aluminum chloride (17 mg/kg, p.o. for 6 weeks) and confirmed by Morris water maze and Y-maze behavioral tests. Biochemical and histological analyses of the hippocampus were also performed. Aluminum-treated rats showed behavioral, biochemical, and histological changes similar to those associated with AD. ND improved learning and memory and reversed histological alterations. At the molecular levels, ND mitigated the increase of hippocampal beta-amyloid (Aβ42) and beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) together with down-regulation of phosphorylated tau protein. It also modulated the excitatory glutamate neurotransmitter level. Furthermore, ND boosted the brain-derived neurotrophic factor (BDNF) and mitochondrial transcription factor-A (TFAM), suppressed the proinflammatory cytokine tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and curbed oxidative stress by hampering of inducible nitric oxide synthase (iNOS). Moreover, ND augmented the hippocampal levels of phosphorylated signal transducer and activator of transcription-3 (p-STAT3) and B cell leukemia/lymphoma-2 (Bcl-2) anti-apoptotic protein while diminished nuclear factor-kappaB (NF-κB) and caspase-3 (casp-3) expression. These findings indicate the protective effect of ND against memory deficits and AD-like pathological aberrations probably via modulating NF-kB and STAT3 signaling, effects mediated likely by modulating N-methyl-D-aspartate (NMDA) receptors.

Altered expression of mir-222 and mir-25 influences diverse gene expression changes in transformed normal and anaplastic thyroid cells, and impacts on MEK and TRAIL protein expression

Thyroid cancer is the most common endocrine malignancy and accounts for the majority of endocrine cancer-related deaths each year. Our group and others have previously demonstrated dysfunctional microRNA (miRNA or miR) expression in the context of thyroid cancer. The objective of the present study was to investigate the impact of synthetic manipulation of expression of miR-25 and miR-222 in benign and malignant thyroid cells. miR-25 and miR-222 expression was upregulated in 8505C (an anaplastic thyroid cell line) and Nthy-ori (a SV40-immortalised thyroid cell line) cells, respectively. A transcriptomics-based approach was utilised to identify targets of the two miRNAs and real-time PCR and western blotting were used to validate a subset of the targets. Almost 100 mRNAs of diverse functions were found to be either directly or indirectly targeted by both miR-222 and miR-25 [fold change ≥2, false discovery rate (FDR) ≤0.05]. Gene ontology analysis showed the miR-25 gene target list to be significantly enriched for genes involved in cell adhesion. Fluidigm real-time PCR technologies were used to validate the downregulation of 23 and 22 genes in response to miR-25 and miR-222 overexpression, respectively. The reduction of the expression of two miR-25 protein targets, TNF-related apoptosis-inducing ligand (TRAIL) and mitogen-activated protein kinase kinase 4 (MEK4), was also validated. Manipulating the expression of both miR-222 and miR-25 influenced diverse gene expression changes in thyroid cells. Increased expression of miR-25 reduced MEK4 and TRAIL protein expression, and cell adhesion and apoptosis are important aspects of miR-25 functioning in thyroid cells.

A novel orally active water-soluble inhibitor of human glutathione transferase exerts a potent and selective antitumor activity against human melanoma xenografts

We designed and synthesized two novel nitrobenzoxadiazole (NBD) analogues of the anticancer agent 6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexan-1-ol (NBDHEX). The new compounds, namely MC3165 and MC3181, bear one and two oxygen atoms within the hydroxy-containing alkyl chain at the C4 position of the NBD scaffold, respectively. This insertion did not alter the chemical reactivity with reduced glutathione, while it conferred a remarkable increase in water solubility. MC3181 was more selective than NBDHEX towards the target protein, glutathione transferase P1-1, and highly effective in vitro against a panel of human melanoma cell lines, with IC50 in the submicromolar-low micromolar range. Interestingly, the cellular response to MC3181 was cell-type-specific; the compound triggered a JNK-dependent apoptosis in the BRAF-V600E-mutated A375 cells, while it induced morphological changes together with an increase in melanogenesis in BRAF wild-type SK23-MEL cells. MC3181 exhibited a remarkable therapeutic activity against BRAF-V600E-mutant xenografts, both after intravenous and oral administration. Outstandingly, no treatment-related signs of toxicity were observed both in healthy and tumor-bearing mice after single and repeated administrations. Taken together, these results indicate that MC3181 may represent a potential novel therapeutic opportunity for BRAF-mutated human melanoma, while being safe and water-soluble and thus overcoming all the critical aspects of NBDHEX in vivo.

Tumor Microenvironment-Mediated Construction and Deconstruction of Extracellular Drug-Delivery Depots

Protein therapy has been considered the most direct and safe approach to treat cancer. Targeting delivery of extracellularly active protein without internalization barriers, such as membrane permeation and endosome escape, is efficient and holds vast promise for anticancer treatment. Herein, we describe a "transformable" core-shell based nanocarrier (designated CS-NG), which can enzymatically assemble into microsized extracellular depots at the tumor site with assistance of hyaluronidase (HAase), an overexpressed enzyme at the tumor microenvironment. Equipped with an acid-degradable modality, the resulting CS-NG can substantially release combinational anticancer drugs-tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) and antiangiogenic cilengitide toward the membrane of cancer cells and endothelial cells at the acidic tumor microenvironment, respectively. Enhanced cytotoxicity on MDA-MB-231 cells and improved antitumor efficacy were observed using CS-NG, which was attributed to the inhibition of cellular internalization and prolonged retention time in vivo.

JNK implication in adipocyte-like cell death induced by chemotherapeutic drug cisplatin

Recent evidence shows that tumor microenvironment containing heterogeneous cells may be involved in cancer initiation, growth and tumor cell response to anticancer therapy. Chemotherapy was designed to make toxic impact on malicious cells in organisms, however, the means to protect healthy cells against chemical toxicity are still unsuccessful. As known, the majority of tumor surrounding cells are cancer-associated adipocytes which influence cancer development, progression and treatment. Targeting the components of tumor microenvironment in combination with conventional cancer treatment may become an effective cancer therapy strategy. However, little is known about adipocyte death mechanisms during combined chemo- and targeted therapy. The importance of c-Jun-NH<inf>2</inf>-terminal kinase (JNK) signaling in tumor development and treatment has been demonstrated using various in vitro and in vivo cancer models. The aim of this study was to ascertain adipocyte viability during simultaneous stress kinase JNK inhibition and exposure to one of the most commonly used anticancer drugs cis-diamminedichloroplatinum II (cisplatin). Our model involved adipocyte-like cells (ADC) which were obtained during in vitro differentiation of adult rabbit muscle-derived stem cells. Cisplatin induced apoptotic cell death. During 24-hr cisplatin treatment gradual, strong and prolonged increase of both JNK and its target protein c-Jun phosphorylation was found in ADC. Pre-treatment of cells with SP600125 decreased cisplatin-induced activation of c-Jun and promoted apoptosis. Upregulation of proapoptotic Bax and downregulation of antiapoptotic Bcl-2 proteins were found to be regulated in JNK-dependent manner. Thus, the results prove the antiapoptotic role of activated JNK in adipocyte-like cells treated with cisplatin.

PGRMC1 contributes to doxorubicin-induced chemoresistance in MES-SA uterine sarcoma

Chemotherapy is one of the major categories of medical oncology and a primary tumor treatment; however, the effectiveness of chemotherapy is restricted by drug resistance. Overcoming resistance to chemotherapy and investigating molecular targeted therapies are challenges currently faced during resistance management. Progesterone receptor membrane component 1 (PGRMC1) is an adapter protein mediating cholesterol synthesis, steroid signaling, and cytochrome p450 activation. Attention has recently focused on the role of PGRMC1 in cell survival, anti-apoptosis, and damage response. In the present study, we used knockdown and overexpression approaches in the following set of uterine sarcoma models to further evaluate the role of PGRMC1 in drug resistance: the doxorubicin-sensitive MES-SA cells and the doxorubicin-resistant MES-SA/DxR-2 µM and MES-SA/DxR-8 µM cells (with different levels of doxorubicin resistance). PGRMC1 repressed doxorubicin-induced cytotoxicity and exhibited an anti-apoptotic effect; it also promoted cell proliferation and cell cycle progression to the S phase. Of note, PGRMC1 overexpression led to the epithelial-mesenchymal transition (EMT) of the sensitive MES-SA cells, thus facilitating their migration and invasion. The combination of PGRMC1 knockdown and the P-glycoprotein inhibitor verapamil significantly decreased the viability of P-glycoprotein-overexpressing MES-SA/DxR-8 μM cells after doxorubicin treatment. Taken together, our results show that PGRMC1 contributed to chemoresistance through cell proliferation, anti-apoptosis, and EMT induction, leading to the suggestion that PGRMC1 may serve as a therapeutic target in combination with an inhibitor in different drug resistance pathways and indicating the usefulness of predictive resistance biomarkers in uterine sarcoma.

Inhibitory effects of evodiamine on human osteosarcoma cell proliferation and apoptosis

Osteosarcoma is a primary malignancy of bone, which is characterized by the proliferation of malignant mesenchymal cells, particularly in children and adolescents. Evodiamine is extracted from a variety of traditional Chinese medicines, which has been reported to induce apoptosis in certain tumors, including cervical, prostate and breast cancer, however, its effect on oestosarcoma cells remains unclear. The aim of the present study was to investigate the effect of evodiamine on osteosarcoma cell proliferation and apoptosis, and explore the associated underlying molecular mechanism. A Cell Counting Kit 8 assay was performed to detect the effects of evodiamine on the proliferation of human osteosarcoma U2OS cells. Annexin V-fluorescein isothiocyanate/propidium iodide staining was performed to analyze the apoptotic rate of the cells. The effect of evodiamine on the protein expression levels of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3 and survivin were detected by performing western blot analysis. Evodiamine inhibited the growth of human osteosarcoma U2OS cells by inhibiting cell proliferation and inducing cell apoptosis. Western blotting demonstrated that evodiamine downregulated the expression of Bcl-2, caspase-3 and survivin, and upregulated the expression of Bax in human osteosarcoma cells. Evodiamine effectively inhibited proliferation and induced apoptosis of osteosarcoma cells in a dose-dependent manner via downregulation of Bcl-2, caspase-3 and survivin protein expression levels and upregulation of Bax protein expression levels.

Synergistic induction of apoptosis by mapatumumab and anthracyclines in human bladder cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in a variety of tumor cells by engaging the death receptors 4 (DR4) and 5 (DR5). We investigated the effect of chemotherapeutic drugs on DR4-mediated apoptosis in human bladder cancer cells, using a human monoclonal agonistic antibody specific for DR4, mapatumumab. Cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Synergy was assessed by isobolographic analysis. Treatment of human bladder cancer T24 cells with mapatumumab in combination with mitomycin C, vinblastine or gemcitabine did not overcome resistance to these agents. However, treatment with mapatumumab in combination with epirubicin (EPI) had a synergistic cytotoxic effect. Synergy was also obtained in KU7 and RT112 human bladder cancer cells. A synergistic effect was also observed with mapatumumab in combination with pirarubicin. The synergy obtained in cytotoxicity with mapatumumab and EPI was also achieved in apoptosis. EPI markedly increased DR4 expression in the bladder cancer cells at both the mRNA and protein levels. Furthermore, the combination-induced cytotoxicity was significantly suppressed by the DR4:Fc chimeric protein. The combination of EPI and mapatumumab significantly activated the caspase cascade, including caspase-8, -9 and -3, which are the downstream molecules of death receptors. These findings indicate that EPI sensitizes bladder cancer cells to DR4-mediated apoptosis through induction of DR4 and activation of caspases, suggesting that the combination therapy of EPI and mapatumumab may be effective for bladder cancer therapy.

Chidamide, a histone deacetylase inhibitor, functions as a tumor inhibitor by modulating the ratio of Bax/Bcl-2 and P21 in pancreatic cancer

Chidamide is a newly designed histone deacetylase (HDAC) inhibitor that has been applied in clinical trials. This study aimed to test the effect of Chidamide on proliferation and apoptosis in pancreatic cancer cell lines and in vivo tumors, as well as to determine the underlying mechanism. The PaTu8988 pancreatic tumor cell line either in culture or inoculated in nude mice were used to evaluate the antitumor characteristics of Chidamide. Proliferation and apoptosis of cultured PaTu8988 cells were examined by CCK-8 assay and Annexin V-FITC/PI double staining assay, respectively. Alterations in protein expression, including Caspase-3, Bcl-2‑like protein 4 (Bax), B-cell lymphoma 2 (Bcl-2) and p21, were tested by western blot analysis. The mRNA of different HDACs was examined by quantitative polymerase chain reaction (qPCR) experiments. Chidamide suppressed cell proliferation and induced early apoptosis of pancreatic tumor cells in a dose‑dependent manner after 48 h of treatment. Similarly, the in vivo study using pancreatic tumor murine model showed that Chidamide administration significantly inhibited the growth of pancreatic tumor and induced tumor cell apoptosis. The in vitro and in vivo studies found that Chidamide treatment significantly decreased the expression of type I HDACs, uncleaved Caspase-3 and p21 and increased the ratio of Bax/Bcl-2 expression. The results from the in vitro and in vivo studies suggested Chidamide might suppress the proliferation of pancreatic tumor cells by downregulating the expression of type I HDACs and p21, and promoting mitochondrial apoptosis pathway-dependent cell apoptosis in a dose-dependent manner. The study provided more evidence for clinical administration of Chidamide that targets pancreatic tumor cells and identified potential molecular targets for the development of potent anticancer drugs.

Antitumor and Apoptosis Induction Effects of Paeonol on Mice Bearing EMT6 Breast Carcinoma

Paeonol is a major phenolic micromolecular component of Moutan cortex Radicis, a traditional Chinese Medicine. It has shown antitumor effects in previous studies; however, the underlying mechanisms remain unknown. This study investigated the mechanism by giving treatments of placebo, cyclophosphamide, paeonol of 150 and 300 mg/kg to 4 groups of mice bearing EMT6 breast cancer. Apoptosis in tumor cells were confirmed by morphology analysis, including hematoxylin, eosin staining and TUNEL staining. The results showed that the weight of EMT6 breast tumor was significantly reduced in the groups treated with both 150 and 300 mg/kg of paeonol. Immunohistochemical and Western blot results showed that the expression of Bcl-2 was down-regulated while the expression of Bax, caspase 8 and caspase 3 was up-regulated respectively. These results suggest that paeonol exhibits antitumor effects and the mechanism of the inhibition is via induction of apoptosis, regulation of Bcl-2 and Bax expression, and activation of caspase 8 and caspase 3.

Two death-inducing human TRAIL receptors to target in cancer: similar or distinct regulation and function?

The emergence during evolution of two tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, receptor-1/DR4 and -2/DR5, able to induce apoptosis has raised the question whether they differ in function and regulation, which is of key importance for selecting either DR4 or DR5 selective pro-apoptotic agents for cancer treatment. In this review we found practically no information regarding possible differences in DR4 and DR5 function based on structural differences. On the other hand, a panel of different DR4 or DR5 selective pro-apoptotic agonists have been developed that were explored for efficacy in different tumour types in a large number of studies. Leukemic cells appear mainly sensitive for DR4-induced apoptosis, contrasting the situation in other tumour types that show heterogeneity in receptor preference and, in some cases, a slight overall preference for DR5. Both receptors were found to mediate intracellular stress-induced apoptosis, although this is most frequently reported for DR5. Interestingly, DR5 was also found to transmit non-apoptotic signalling in resistant tumour cells and recently nuclear localization and a role in microRNA maturation has been described. DR4 expression is most heavily regulated by promoter methylation, intracellular trafficking and post-translational modifications. DR5 expression is predominantly regulated at the transcriptional level, which may reflect its ability to respond to cellular stressors. It will be important to further increase our understanding of the mechanisms determining TRAIL receptor preference in order to select the appropriate TRAIL receptor selective agonists for therapy, and to develop novel strategies to enhance apoptosis activation in tumours.

Tumoricidal activity of combining the agonistic DR5 antibody D-6 with cisplatin in C30 cisplatin-resistant ovarian cancer in vitro and in vivo

A previous study by our group reported that the agonistic DR5 antibody D-6 was capable of triggering apoptosis in A2780 cisplatin-sensitive ovarian cancer cells and that this marked effect was enhanced by cisplatin in vitro. The present study examined whether D-6 and cisplatin may exert the same anti-tumor effect on C30 cisplatin-resistant ovarian cancer cells, and the underlying mechanisms were investigated. D-6 exhibited an apoptosis-inducing effect, increased the cell growth inhibition rate of C30 cells in a dose-dependent manner, induced significant morphological changes characteristic for apoptosis, as observed by electron microscopy, and downregulated the expression of caspase 3, 8 and 9 precursors in C30 cells treated with D-6 at the protein level. All of these effects were evidently enhanced when accompanied by cisplatin. Furthermore, D-6 alone or in combination with cisplatin in the established models of C30 tumor xenografts resulted in a significant repression of tumor growth, and evident apoptosis, as determined by a terminal transferase dUTP nick end labeling assay. In addition, the expression of caspase 3, 8 and 9 precursors in the tumor xenografts was as similar to that found in vitro. In conclusion, the present study suggested that D-6 may serve as a novel anti-tumor agent against C30 cisplatin‑resistant ovarian cancer, with the ability to trigger apoptosis via caspase-dependent and ‑independent pathways and the potential to decrease the cisplatin resistance of the C30 cell line.

Phenethyl isothiocyanate sensitizes glioma cells to TRAIL-induced apoptosis

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is a promising antitumor therapy. However, many cancer cells, including malignant glioma cells, tend to be resistant to TRAIL, highlighting the need for strategies to overcome TRAIL resistance. Here we show that in combination with phenethyl isothiocyanate (PEITC), exposure to TRAIL induced apoptosis in TRAIL-resistant glioma cells. Subtoxic concentrations of PEITC significantly potentiated TRAIL-induced cytotoxicity and apoptosis in glioma cells. PEITC dramatically upregulated DR5 receptor expression but had no effects on DR4 receptor. PEITC enhances TRAIL-induced apoptosis through the downregulation of cell survival proteins and the upregulation of DR5 receptors through actions on the ROS-induced-p53.

Myriocin induces apoptotic lung cancer cell death via activation of DR4 pathway

It has been known that myriocin inhibits melanoma growth. However, the effects and action mechanisms of myriocin on lung cancer cell growth have not been reported. In this study, we examined whether myriocin isolated from Mycelia sterilia inhibits cell growth of lung cancer cells (A549 and NCI-H460) as well as possible signaling pathways involved in cell growth inhibition. Different concentrations of myriocin inhibited the growth of lung cancer cells through the induction of apoptotic cell death. Consistent with cancer cell growth inhibition, myriocin induced the expression of death receptors (DRs) as well as p-JNK and p-p38 in both cell lines. Moreover, the combination of myriocin with DR4 ligand TRAIL, and other well known anti-tumor drugs (docetaxel and cisplatin) synergistically inhibited cancer cell growth, and induced DR4 expression. These results showed that myriocin inhibits lung cancer cells growth through apoptosis via the activation of DR4 pathways, and enhanced anti-cancer effects with well known drugs. Thus, our study indicates that myriocin could be effective for lung cancer cells as an anti-cancer drug and/or a conjunction agent with well known anti-cancers.

Mass cytometry to decipher the mechanism of nongenetic drug resistance in cancer

Nongenetic resistance has recently been described as a major impediment to effective cancer therapy. Nongenetic resistance is challenging to study since it occurs nonuniformly, even in cell lines, and can involve the interplay of multiple survival pathways. Until recently, no technology allowed measurement of large-scale alterations in survival pathways with single-cell resolution. Mass cytometry, a flow-based technique in which the activation of up to 50 proteins can be measured simultaneously in single-cell, now provides the ability to examine nongenetic resistance on the functional level on a cell-by-cell basis. The application of mass cytometry, in combination with new bioinformatic techniques, will allow fundamental questions on nongenetic resistance to be addressed: Is resistance caused by selection of cells with a pre-existing survival phenotype or induction of a survival program? Which survival pathways are necessary for nongenetic resistance and how do they interact? Currently, mass cytometry is being used to investigate the mechanism of nongenetic resistance to TRAIL-induced apoptosis. The approaches being developed to understand resistance to TRAIL will likely be applied to elucidate the mechanisms of nongenetic resistance broadly and in the clinic.

Proteasomal regulation of caspase-8 in cancer cell apoptosis

Previous studies demonstrated that proteasome inhibition sensitizes TRAIL resistant prostate cancer cells to TRAIL-mediated apoptosis via stabilization of the active p18 subunit of caspase-8. The present study investigated the impact of proteasome inhibition on caspase-8 stability, ubiquitination, trafficking, and activation in cancer cells. Using caspase-8 deficient neuroblastoma (NB7) cells for reconstituting non-cleavable mutant forms of caspase-8, we demonstrated that the non-cleavable forms of caspase-8 are capable of inducing apoptosis comparably to wild-type caspase-8, in response to proteasome inhibitor and GST-TRAIL. Moreover in the LNCaP human prostate cancer cells, caspase-8 polyubiquitination occurs after TRAIL stimulation and caspase-8 processing. Subcellular fractionation analysis revealed caspase-8 activity in both cytosol and plasma membrane fractions in both NB7 reconstituted caspase-8 cell lines, as well the LNCaP prostate cancer cells. The present results suggest that caspase-8 stabilization through proteasome inhibition leads to reactivation of the extrinsic pathway of apoptosis and identify E3 ligase mediating caspase-8 polyubiquitination, as a novel molecular target. Inhibition of this E3 ligase in combination with TRAIL towards restoring apoptosis signaling activation may have potential therapeutic significance in resistant tumors.

Asymmetric dimethylarginine attenuates serum starvation-induced apoptosis via suppression of the Fas (APO-1/CD95)/JNK (SAPK) pathway

Asymmetric dimethylarginine (ADMA) is synthesized by protein arginine methyltransferases during methylation of protein arginine residues and released into blood upon proteolysis. Higher concentrations of ADMA in blood have been observed in patients with metabolic diseases and certain cancers. However, the role of ADMA in colon cancer has not been well investigated. ADMA serum levels in human patients diagnosed with colon cancer were found to be higher than those present in healthy subjects. ADMA treatment of LoVo cells, a human colon adenocarcinoma cell line, attenuated serum starvation-induced apoptosis and suppressed the activation of the Fas (APO-1/CD95)/JNK (SAPK) (c-Jun N terminal protein kinase/stress-activated protein kinase)pathway. ADMA also suppressed the activation of JNK triggered by death receptor ligand anti-Fas mAb and exogenous C₂-ceramide. Moreover, we demonstrated that ADMA pretreatment protected LoVo cells from doxorubicin hydrochloride-induced cell death and activation of the Fas/JNK pathway. In summary, our results suggest that the elevated ADMA in colon cancer patients may contribute to the blocking of apoptosis of cancer cells in response to stress and chemotherapy.

Low amount of salinomycin greatly increases Akt activation, but reduces activated p70S6K levels

The present study identified a novel salinomycin (Sal)-sensitization mechanism in cancer cells. We analyzed the signal proteins Akt, Jnk, p38, Jak, and Erk1/2 in cancer cell lines that had arrested growth following low amounts of Sal treatment. We also tested the signal molecules PI3K, PDK1, GSK3β, p70S6K, mTOR, and PTEN to analyze the PI3K/Akt/mTOR pathway. The results showed that Sal sensitization positively correlates with large reductions in p70S6K activation. Interestingly, Akt was the only signal protein to be significantly activated by Sal treatment. The Akt activation appeared to require the PI3K pathway as its activation was abolished by the PI3K inhibitors LY294002 and wortmannin. The Akt activation by Sal was conserved in the other cell lines analyzed, which originated from other organs. Both Akt activation and C-PARP production were proportionally increased with increased doses of Sal. In addition, the increased levels of pAkt were not reduced over the time course of the experiment. Co-treatment with Akt inhibitors sensitized the Sal-treated cancer cells. The results thereby suggest that Akt activation is increased in cells that survive Sal treatment and resist the cytotoxic effect of Sal. Taken together; these results indicate that Akt activation may promote the resistance of cancer cells to Sal.

Death receptors as targets in cancer

Anti-tumour therapies based on the use pro-apoptotic receptor agonists, including TNF-related apoptosis-inducing ligand (TRAIL) or monoclonal antibodies targeting TRAIL-R1 or TRAIL-R2, have been disappointing so far, despite clear evidence of clinical activity and lack of adverse events for the vast majority of these compounds, whether combined or not with conventional or targeted anti-cancer therapies. This brief review aims at discussing the possible reasons for the lack of apparent success of these therapeutic approaches and at providing hints in order to rationally design optimal protocols based on our current understanding of TRAIL signalling regulation or resistance for future clinical trials.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

Oncoapoptotic signaling and deregulated target genes in cancers: special reference to oral cancer

Cancer is a class of diseases characterized by uncontrolled cell growth. The development of cancer takes place in a multi-step process during which cells acquire a series of mutations that eventually lead to unrestrained cell growth and division, inhibition of cell differentiation, and evasion of cell death. Dysregulation of oncoapoptotic genes, growth factors, receptors and their downstream signaling pathway components represent a central driving force in tumor development. The detailed studies of signal transduction pathways for mechanisms of cell growth and apoptosis have significantly advanced our understanding of human cancers, subsequently leading to more effective treatments. Oral squamous cell carcinoma represents a classic example of multi-stage carcinogenesis. It gradually evolves through transitional precursor lesions from normal epithelium to a full-blown metastatic phenotype. Genetic alterations in many genes encoding crucial proteins, which regulate cell proliferation, differentiation, survival and apoptosis, have been implicated in oral cancer. As like other solid tumors, in oral cancer these genes include the ones coding for cell cycle regulators or oncoproteins (e.g. Ras, Myc, cyclins, CDKs, and CKIs), tumor suppressors (e.g. p53 and pRb), pro-survival proteins (e.g. telomerase, growth factors or their receptors), anti-apoptotic proteins (e.g. Bcl2 family, IAPs, and NF-kB), pro-apoptotic proteins (e.g. Bax and BH-3 family, Fas, TNF-R, and caspases), and the genes encoding key transcription factors or elements for signal transduction leading to cell growth and apoptosis. Here we discuss the current knowledge of oncoapoptotic regulation in human cancers with special reference to oral cancers.

Non-canonical kinase signaling by the death ligand TRAIL in cancer cells: discord in the death receptor family

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-based therapy is currently evaluated in clinical studies as a tumor cell selective pro-apoptotic approach. However, besides activating canonical caspase-dependent apoptosis by binding to TRAIL-specific death receptors, the TRAIL ligand can activate non-canonical cell survival or proliferation pathways in resistant tumor cells through the same death receptors, which is counterproductive for therapy. Even more, recent studies indicate metastases-promoting activity of TRAIL. In this review, the remarkable dichotomy in TRAIL signaling is highlighted. An overview of the currently known mechanisms involved in non-canonical TRAIL signaling and the subsequent activation of various kinases is provided. These kinases include RIP1, IκB/ NF-κB, MAPK p38, JNK, ERK1/2, MAP3K TAK1, PKC, PI3K/Akt and Src. The functional consequences of their activation, often being stimulation of tumor cell survival and in some cases enhancement of their invasive behavior, are discussed. Interestingly, the non-canonical responses triggered by TRAIL in resistant tumor cells resemble that of TRAIL-induced signals in non-transformed cells. Better knowledge of the mechanism underlying the dichotomy in TRAIL receptor signaling may provide markers for selecting patients who will likely benefit from TRAIL-based therapy and could provide a rationalized basis for combination therapies with TRAIL death receptor-targeting drugs.

BNIP3 acts as transcriptional repressor of death receptor-5 expression and prevents TRAIL-induced cell death in gliomas

Glioblastoma multiforme (GBM) is the most common and malignant brain tumor, and current treatment modalities such as surgical resection, adjuvant radiotherapy and temozolomide (TMZ) chemotherapy are ineffective. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a novel cancer therapeutic agent for GBM because of its capability of inducing apoptosis in glioma cells. Unfortunately, the majority of glioma cells are resistant to TRAIL-induced apoptosis. The Bcl-2 nineteen kilodalton interacting protein (BNIP3) is a pro-cell death BH3-only member of the Bcl-2 family that is one of the highest expressed genes in hypoxic regions of GBM tumors. We previously found that BNIP3 is localized to the nucleus in GBM tumors and suppresses cell death in glioma cells. Herein, we have discovered when BNIP3 nuclear expression is knockdown in glioma cell lines and in normal mouse astrocytes, TRAIL and its death receptor, death receptor-5 (DR5) expression is increased. In addition, when nuclear BNIP3 expression is increased, the amount of TRAIL-induced apoptosis is reduced. Using a streptavidin pull-down assay, we found that BNIP3 binds to the DR5 promoter and nuclear BNIP3 binds to the DR5 promoter. Furthermore, nuclear BNIP3 expression in GBM tumors correlates with decreased DR5 expression. Taken together, we have discovered a novel transcriptional repression function for BNIP3 conferring a TRAIL resistance in glioma cells.

The role of intracrine androgen metabolism, androgen receptor and apoptosis in the survival and recurrence of prostate cancer during androgen deprivation therapy

Prostate cancer (CaP) is the most frequently diagnosed cancer and leading cause of cancer death in American men. Almost all men present with advanced CaP and some men who fail potentially curative therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. The goal of this review is to apply our current understanding of CaP and castration-recurrent CaP (CR-CaP) to earlier studies that characterized ADT and the molecular mechanisms that facilitate the transition from androgen-stimulated CaP to CR-CaP. Reexamination of earlier studies also may provide a better understanding of how more newly recognized mechanisms, such as intracrine metabolism, may be involved with the early events that allow CaP survival after initiation of ADT and subsequent development of CR-CaP.

Phosphorylated p38 and JNK MAPK proteins in hepatocellular carcinoma

BACKGROUND

The p38 and JNK MAPK proteins function as key mediators in cellular responses to extracellular stimuli. Deregulated p38 and JNK expressions have been associated with cancer development. This study aimed to investigate the association of p-p38 and p-JNK levels of the cancerous tissues with hepatocellular carcinoma (HCC) development.

MATERIALS AND METHODS

One hundred and four liver cancer tissues of patients with HCC who underwent curative resection were prospectively collected. The levels of activated/p-p38 and p-JNK were determined by the enzyme-linked immunosorbent assay. The associations of results with clinicopathological characteristics and overall survival were further statically analysed using chi-squared test, two-tailed Student's t-test and Kaplan-Meier survival curve.

RESULTS

The p-p38 levels were significantly higher in the HCC patients with a larger tumour (≥ 3 cm) and satellite tumour, and significantly correlated with the p-JNK levels. High p-p38 and low p-JNK expressions were associated with a poor survival in the patients with HCC (odds ratio, 4·24 and 0·20; P = 0·03 and 0·03, respectively). The Kaplan-Meier survival analysis showed that the HCC patients with high p-p38 expressions had a poor overall survival than those with low p-p38 expressions (P = 0·04), and a coexistent and high p-JNK expression remarkably improved this trend.

CONCLUSIONS

Increasing p-p38 levels in HCC tissues were associated with tumour size and the formation of satellite tumours. High p-p38 expression could serve as a predictor for a poor survival for the patients with HCC. Simultaneous expression of p-JNK in HCC tissues might antagonize the promoting effect of p-p38 in human liver cancer.

GSK3 inhibition prevents lethal GVHD in mice

Graft-versus-host disease (GVHD) is a major contributor to transplant-related mortality and morbidity after allogeneic stem cell transplantation. Despite advancements in tissue-typing techniques, conditioning regimens, and therapeutic intervention, the incidence rate of GVHD remains high. GVHD is caused by alloreactive donor T cells that infiltrate and destroy host tissues (e.g., skin, liver, and gut). Therefore, GVHD is prevented and treated with therapeutics that suppress proinflammatory cytokines and T-cell function (e.g., cyclosporine, glucocorticoids). Here we report that the small molecule inhibitor of glycogen synthase kinase 3, 6-bromoindirubin 3'-oxime (BIO), prevents lethal GVHD in a humanized xenograft model in mice. BIO treatment did not affect donor T-cell engraftment, but suppressed their activation and attenuated bone marrow and liver destruction mediated by activated donor T cells. Glycogen synthase kinase 3 inhibition modulated the Th1/Th2 cytokine profile in vitro and suppressed activation of signal transducers and activators of transcription 1 and 3 signaling pathways both in vitro and in vivo. Importantly, human T cells derived from BIO-treated mice were able to mediate anti-tumor effects in vitro, and BIO did not affect stem cell engraftment and multilineage reconstitution in a mouse model of transplantation. These data demonstrate that inhibition of glycogen synthase kinase 3 can potentially abrogate GVHD without compromising the efficacy of transplantation.

A novel anti-DR5 chimeric antibody and epirubicin synergistically suppress tumor growth

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of tumor cells. TRAIL receptor 2 (DR5) expression is high in tumor cells, transformed cells, and clinical tumor specimens and is low in most normal cells and tissues; therefore, DR5 is considered an attractive target for cancer therapy. In this study, HMCAZ5, a novel mouse-human chimeric antibody based on AD5-10, was generated and stably expressed in CHO-dhfr(-) cells. Highly purified HMCAZ5 exhibits a high affinity for the receptor that is equal to the parental mouse antibody, induces apoptosis in various cancer cells but not in normal hepatocytes, and elicits both antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in various human cancer cells. The anthracycline anticancer drug epirubicin (EPB) synergizes the cytotoxicity of HMCAZ5 in cancer cells by upregulating DR5 expression on the cell surfaces, enhancing p53 expression, Bid cleavage, and JNK phosphorylation and downregulating c-FLIP expression and Akt phosphorylation. Moreover, HMCAZ5 alone suppresses tumor growth, and EPB augments the tumoricidal activity in human colorectal and hepatocellular tumor xenografts in athymic nude mice. These data suggest that the anti-DR5 chimeric antibody HMCAZ5 may have a clinical use and represents a useful immunological strategy, in combination with chemotherapy, for the treatment of cancer.

Induction of proapoptotic antibodies to triple-negative breast cancer by vaccination with TRAIL death receptor DR5 DNA

TNF-related apoptosis-inducing ligand receptor 2 [TRAIL-R2 or death receptor 5 (DR5)] is expressed at elevated levels in a broad range of solid tumors to mediate apoptotic signals from TRAIL or agonist antibodies. We tested the hypothesis that DR5 DNA vaccination will induce proapoptotic antibody to trigger apoptosis of tumor cells. BALB/c mice were electrovaccinated with DNA-encoding wild-type human DR5 (phDR5) or its derivatives. Resulting immune serum or purified immune IgG induced apoptosis in triple-negative breast cancer (TNBC) cells, which were also TRAIL sensitive. The proapoptotic activity of immune serum at dilutions of 0.5-2% was comparable to that of 1-2 μg/ml of TRAIL. Apoptotic activity of immune serum was enhanced by antibody crosslinking. Apoptotic cell death induced by anti-DR5 antibody was shown by the cleavage of PARP and caspase-3. In contrast, immune serum had no effect on the proliferation of activated human T cells, which expressed low levels of DR5. In vivo, hDR5 reactive immune serum prevented growth of SUM159 TNBC cells in severe combined immune-deficient mice. DR5-specific IFN-γ-secreting T cells were also induced by DNA vaccination. Furthermore, the feasibility to overcome immune tolerance to self DR5 was shown by the induction of mouse DR5-binding antibody after electrovaccination of BALB/c mice with pmDR5ectm-Td1 encoding a fusion protein of mouse DR5 and an immunogenic fragment of tetanus toxin. These findings support DR5 as a promising vaccine target for controlling TNBC and other DR5-positive cancers.