Chemosensitivity of solid tumor cells in vitro is related to activation of the CD95 system

Destabilizing the genome as a therapeutic strategy to enhance response to immune checkpoint blockade: a systematic review of clinical trials evidence from solid and hematological tumors

Background: Genomic instability is increased alterations in the genome during cell division and is common among most cancer cells. Genome instability enhances the risk of initial carcinogenic transformation, generating new clones of tumor cells, and increases tumor heterogeneity. Although genome instability contributes to malignancy, it is also an "Achilles' heel" that constitutes a therapeutically-exploitable weakness-when sufficiently advanced, it can intrinsically reduce tumor cell survival by creating DNA damage and mutation events that overwhelm the capacity of cancer cells to repair those lesions. Furthermore, it can contribute to extrinsic survival-reducing events by generating mutations that encode new immunogenic antigens capable of being recognized by the immune system, particularly when anti-tumor immunity is boosted by immunotherapy drugs. Here, we describe how genome-destabilization can induce immune activation in cancer patients and systematically review the induction of genome instability exploited clinically, in combination with immune checkpoint blockade. Methods: We performed a systematic review of clinical trials that exploited the combination approach to successfully treat cancers patients. We systematically searched PubMed, Cochrane Central Register of Controlled Trials, Clinicaltrials.gov, and publication from the reference list of related articles. The most relevant inclusion criteria were peer-reviewed clinical trials published in English. Results: We identified 1,490 studies, among those 164 were clinical trials. A total of 37 clinical trials satisfied the inclusion criteria and were included in the study. The main outcome measurements were overall survival and progression-free survival. The majority of the clinical trials (30 out of 37) showed a significant improvement in patient outcome. Conclusion: The majority of the included clinical trials reported the efficacy of the concept of targeting DNA repair pathway, in combination with immune checkpoint inhibitors, to create a "ring of synergy" to treat cancer with rational combinations.

Cancer Immunoediting: Elimination, Equilibrium, and Immune Escape in Solid Tumors

Emphasizing the dynamic processes between cancer and host immune system, the initially discovered concept of cancer immunosurveillance has been replaced by the current concept of cancer immunoediting consisting of three phases: elimination, equilibrium, and escape. Solid tumors composed of both cancer and host stromal cells are an example how the three phases of cancer immunoediting functionally evolve and how tumor shaped by the host immune system gets finally resistant phenotype. The elimination, equilibrium, and escape have been described in this chapter in details, including the role of immune surveillance, cancer dormancy, disruption of the antigen-presenting machinery, tumor-infiltrating immune cells, resistance to apoptosis, as well as the function of tumor stroma, microvesicles, exosomes, and inflammation.

Destined to Die: Apoptosis and Pediatric Cancers

Apoptosis (programmed cell death) is a systematic and coordinated cellular process that occurs in physiological and pathophysiological conditions. Sidestepping or resisting apoptosis is a distinct characteristic of human cancers including childhood malignancies. This review dissects the apoptosis pathways implicated in pediatric tumors. Understanding these pathways not only unraveled key molecules that may serve as potential targets for drug discovery, but also molecular nodes that integrate with other signaling networks involved in processes such as development. This review presents current knowledge of the complex regulatory system that governs apoptosis with respect to other processes in pediatric cancers, so that fresh insights may be derived regarding treatment resistance or for more effective treatment options.

Anti-cancer effects of cinnamon: Insights into its apoptosis effects

Cancer is known as a leading cause of death worldwide. In the last two decades, the incidence of cancer has been dramatically increased mostly due to lifestyle changes. The importance of this issue has attracted further attention to discover novel therapies to prevent and treat cancers. According to previous studies, drugs used to treat cancer have shown significant limitations. Therefore, the role of herbal medicines alone or in combination with chemotherapy drugs has been extensively studied in cancer treatment. Cinnamon is a natural component showing a wide range of pharmacological functions including anti-oxidant, anti-microbial and anti-cancer activities. Impaired apoptosis plays critical roles in the initiation and progression of cancer. Increasing evidence indicates that cinnamon, as a therapeutic agent, has anti-cancer effects via affecting numerous apoptosis-related pathways in cancer cells. Here, we highlighted anticancer properties of cinnamon, particularly through targeting apoptosis-related mechanisms.

Pevonedistat, a Nedd8-activating enzyme inhibitor, sensitizes neoplastic B-cells to death receptor-mediated apoptosis

While death receptor ligands (Fas and TRAIL) kill chemoresistant tumor cell lines, related therapies have limited clinical efficacy as single agents. Death receptor signaling is modulated by nuclear factor-κB (NFκB), a family of transcription factors which are constitutively active in B-cell malignancies. We and others have shown that pevonedistat, an investigational inhibitor of the NEDD8-activating enzyme, abrogates NFκB activity in B-cell neoplasia. Here we demonstrate that diffuse large B-cell lymphoma, particularly activated B-cell type, and primary chronic lymphocytic leukemia cells are re-sensitized to extrinsic apoptosis by pevonedistat. Pevonedistat enhanced caspase-8 processing following death receptor ligation, and downmodulated cFLIP, a NFκB-regulated protease-deficient caspase homolog. However, treatment with pevonedistat did not modulate death-inducing signaling complex in neoplastic B-cells, suggesting that they were sensitized to death ligands through the mitochondrial pathway. Our data provide rationale for further development of pharmacologic agents including pevonedistat in strategies which enhance death receptor signaling in lymphoid malignancies.

Apoptosis, Chemoresistance, and Breast Cancer: Insights From the MCF-7 Cell Model System

The MCF-7 cell line was derived from a patient with metastatic breast cancer in 1970. Since then it has become a prominent model system for the study of estrogen receptor-positive breast cancer. With this model as a focus, this review summarizes important studies addressing tumor necrosis factor-α as a prototypical apoptosis-inducing cytokine in MCF-7 cells. Both survival and death receptor signaling pathways are discussed in terms of their role in chemotherapy-induced apoptosis as well as in chemoresistance. Novel therapeutic approaches to the treatment of breast cancer are proposed utilizing knowledge of these signaling pathways as targets. Specifically, ceramide metabolism is proposed as a novel target for chemosensitivity, perhaps combined with selective inhibitors of Bcl-2 or PI3K/Akt/nuclear factor-κB. Suggested areas of future research include translational studies manipulating candidate survival and death signaling pathways.

Human-gyrovirus-Apoptin triggers mitochondrial death pathway--Nur77 is required for apoptosis triggering

The human gyrovirus derived protein Apoptin (HGV-Apoptin) a homologue of the chicken anemia virus Apoptin (CAV-Apoptin), a protein with high cancer cells selective toxicity, triggers apoptosis selectively in cancer cells. In this paper, we show that HGV-Apoptin acts independently from the death receptor pathway as it induces apoptosis in similar rates in Jurkat cells deficient in either FADD (fas-associated death domain) function or caspase-8 (key players of the extrinsic pathway) and their parental clones. HGV-Apoptin induces apoptosis via the activation of the mitochondrial intrinsic pathway. It induces both mitochondrial inner and outer membrane permebilization, characterized by the loss of the mitochondrial potential and the release into cytoplasm of the pro-apoptotic molecules including apoptosis inducing factor and cytochrome c. HGV-Apoptin acts via the apoptosome, as lack of expression of apoptotic protease-activating factor 1 in murine embryonic fibroblast strongly protected the cells from HGV-Apoptin–induced apoptosis. Moreover, QVD-oph a broad-spectrum caspase inhibitor delayed HGV-Apoptin–induced death. On the other hand, overexpression of the anti-apoptotic BCL-XL confers resistance to HGV-Apoptin–induced cell death. In contrast, cells that lack the expression of the pro-apoptotic BAX and BAK are protected from HGV-Apoptin induced apoptosis. Furthermore, HGV-Apoptin acts independently from p53 signal but triggers the cytoplasmic translocation of Nur77. Taking together these data indicate that HGV-Apoptin acts through the mitochondrial pathway, in a caspase-dependent manner but independently from the death receptor pathway.

Mitochondrial dysfunction in cancer

Mitochondria are semi-autonomous organelles of eukaryotic cells. They perform crucial functions such as generating most of the cellular energy through the oxidative phosphorylation (OXPHOS) system and some other metabolic processes. In addition, mitochondria are involved in regulation of cell death and reactive oxygen species (ROS) generation. Also, mitochondria play important roles in carcinogenesis via altering energy metabolism, resistance to apoptosis, increase of production of ROS and mtDNA (mitochondrial genome) changes. Studies have suggested that aerobic glycolysis is high in malignant tumors. Probably, it correlates with high glucose intake of cancerous tissues. This observation is contrary to Warburg's theory that the main way of energy generation in cancer cells is non-oxidative glycolysis. Further studies have suggested that in tumor cells both oxidative phosphorylation and glycolysis were active at various rates.

An increase of intracellular oxidative stress induces damage of cellular structure and somatic mutations. Further studies confirmed that permanent activity of oxidative stress and the influence of chronic inflammation damage the healthy neighboring epithelium and may lead to carcinogenesis. For instance, chronic inflammatory bowel disease could be related to high risk of colon adenocarcinoma.

The data have shown a role of ROS generation, mtDNA or nDNA alterations and abnormal apoptotic machinery in endometrial cancer progress. Recent studies suggest that mtDNA mutations might play a potential role in endometrial cancer progress and indicate an increase of mitochondrial biogenesis in this cancer. The investigators suggested that MtCOI and MtND6 alteration has an influence on assembly of respiratory complexes in endometrial cancer.

In many human cancers, there is a deregulation of the balance between cell growth and death. The tumor cells can avoid apoptosis through a loss of balance between anti- and pro-apoptotic proteins, reduced caspase function and impaired death receptor signaling. Over-expression of the anti-apoptotic BCL-2 gene has also been identified in numerous cancers including colon, thyroid, breast and endometrial cancer. Most studies have found low BCL-2 family gene expression, which could be a sign of blocking apoptosis in breast and endometrial cancer. Moreover, BCL-2 gene expression is correlated with the degree of aggressiveness and differentiation in endometrial cancer. As a result, it could be a valuable predictor of disease progression.

Gemcitabine sensitizes lung cancer cells to Fas/FasL system-mediated killing

Gemcitabine is a chemotherapy agent commonly used in the treatment of non-small cell lung cancer (NSCLC) that has been demonstrated to induce apoptosis in NSCLC cells by increasing functionally active Fas expression. The aim of this study was to evaluate the Fas/Fas ligand (FasL) system involvement in gemcitabine-induced lung cancer cell killing. NSCLC H292 cells were cultured in the presence or absence of gemcitabine. FasL mRNA and protein were evaluated by real-time PCR, and by Western blot and flow cytometry, respectively. Apoptosis of FasL-expressing cells was evaluated by flow cytometry, and caspase-8 and caspase-3 activation by Western blot and a colorimetric assay. Cytotoxicity of lymphokine-activated killer (LAK) cells and malignant pleural fluid lymphocytes against H292 cells was analysed in the presence or absence of the neutralizing anti-Fas ZB4 antibody, by flow cytometry. Gemcitabine increased FasL mRNA and total protein expression, the percentage of H292 cells bearing membrane-bound FasL (mFasL) and of mFasL-positive apoptotic H292 cells, as well as caspase-8 and caspase-3 cleavage. Moreover, gemcitabine increased CH11-induced caspase-8 and caspase-3 cleavage and proteolytic activity. Cytotoxicity of LAK cells and pleural fluid lymphocytes was increased against gemcitabine-treated H292 cells and was partially inhibited by ZB4 antibody. These results demonstrate that gemcitabine: (i) induces up-regulation of FasL in lung cancer cells triggering cell apoptosis via an autocrine/paracrine loop; (ii) induces a Fas-dependent apoptosis mediated by caspase-8 and caspase-3 activation; (iii) enhances the sensitivity of lung cancer cells to cytotoxic activity of LAK cells and malignant pleural fluid lymphocytes, partially via Fas/FasL pathway. Our data strongly suggest an active involvement of the Fas/FasL system in gemcitabine-induced lung cancer cell killing.

Combined treatment of murine fibrosarcoma with chemotherapy (Paclitaxel), radiotherapy, and intratumoral injection of dendritic cells

Background

New antitumor therapeutic strategies aim to combine different approaches that are able to induce tumor-specific effector and memory T cell responses that might control tumor growth. Dendritic cells (DCs) have the capacity to induce antigen-specific cytotoxic T lymphocytes. We have previously shown that the combined treatment of paclitaxel chemotherapy (Chemo) and injection of DCs led to complete tumor regression.

Objective

The goal of this study was to evaluate synergistic antitumor effect of a triple combination treatment comprising radiotherapy, paclitaxel Chemo and intratumoral injection of syngeneic bone marrow-derived DCs on murine fibrosarcoma, compared to other single or double combination treatments.

Methods

For the murine fibrosarcoma model, naïve C57BL/6 mice were inoculated intradermally with 2×10³ MCA102 cells in the right upper flank. Mice were assigned to five groups (untreatedcontrol, RT alone, RT+Chemo, RT+DC, and RT+Chemo+DC), with eight mice in each group. In vitro cytotoxicity assays were performed to assess the immune activity. The persistence of tumor-specific immunity was determined by second tumor challenge in mice with complete tumor regression.

Results

The triple combination treatment showed a significantly enhanced therapeutic efficacy by decreasing tumor size and inducing complete tumor regression, resulting in a cure of 50% of mice. The results of in vitro cytotoxicity assays and the second tumor challenge experiment strongly indicated the induction of a tumor-specific cytotoxic T lymphocyte response and acquisition of prolonged tumor immunity.

Conclusion

These findings suggest that the triple combination treatment can be a promising strategy for the treatment of murine fibrosarcoma.

β-Elemene enhances susceptibility to cisplatin in resistant ovarian carcinoma cells via downregulation of ERCC-1 and XIAP and inactivation of JNK

β-Elemene is a promising new plant-derived drug with broad-spectrum anticancer activity. It also increases cisplatin cytotoxicity and enhances cisplatin sensitivity in resistant human carcinoma cells. However, little is known about the mechanism of its action. To explore the potential therapeutic application of β-elemene as a drug-resistance modulator, this study investigated the underlying mechanism of β-elemene activity in cisplatin-resistant ovarian cancer cells. β-Elemene enhanced cisplatin sensitivity to a much greater extent in chemoresistant A2780/CP70 and MCAS human ovarian carcinoma cells compared to the chemosensitive parental cell line A2780. The dose-modifying factors for cisplatin were between 35 and 60 for A2780/CP70 cells and between 1.6 and 2.5 for A2780 cells. In the cisplatin-resistant ovarian carcinoma cells, β-elemene abrogated cisplatin-induced expression of excision repair cross-complementation group-1 (ERCC-1), a marker gene in the nucleotide excision repair pathway that repairs cisplatin-caused DNA damage. In addition, β-elemene not only reduced the level of X-linked inhibitor of apoptosis protein (XIAP), but also downregulated cisplatin-mediated XIAP expression in chemoresistant cells. Furthermore, β-elemene blocked the cisplatin-stimulated increase in the level of phosphorylated c-Jun NH₂-terminal kinase (JNK) in these cells. These novel findings suggest that the β-elemene enhancement of cisplatin sensitivity in human chemoresistant ovarian cancer cells is mediated at least in part through the impairment of DNA repair activity and the activation of apoptotic signaling pathways, thereby making resistant ovarian cancer cells susceptible to cisplatin-induced cell death.

Regulation of cell death in cancer-possible implications for immunotherapy

Since most anticancer therapies including immunotherapy trigger programmed cell death in cancer cells, defective cell death programs can lead to treatment resistance and tumor immune escape. Therefore, evasion of programmed cell death may provide one possible explanation as to why cancer immunotherapy has so far only shown modest clinical benefits for children with cancer. A better understanding of the molecular mechanisms that regulate sensitivity and resistance to programmed cell death is expected to open new perspectives for the development of novel experimental treatment strategies to enhance the efficacy of cancer immunotherapy in the future.

YB-1: oncoprotein, prognostic marker and therapeutic target?

Hanahan and Weinberg have proposed the ‘hallmarks of cancer’ to cover the biological changes required for the development and persistence of tumours [Hanahan and Weinberg (2011) Cell 144, 646–674]. We have noted that many of these cancer hallmarks are facilitated by the multifunctional protein YB-1 (Y-box-binding protein 1). In the present review we evaluate the literature and show how YB-1 modulates/regulates cellular signalling pathways within each of these hallmarks. For example, we describe how YB-1 regulates multiple proliferation pathways, overrides cell-cycle check points, promotes replicative immortality and genomic instability, may regulate angiogenesis, has a role in invasion and metastasis, and promotes inflammation. We also argue that there is strong and sufficient evidence to suggest that YB-1 is an excellent molecular marker of cancer progression that could be used in the clinic, and that YB-1 could be a useful target for cancer therapy.

Pro- and anti-apoptotic effects of p53 in cisplatin-treated human testicular cancer are cell context-dependent

In murine testicular cancer (TC) cells wild-type p53 contributes to sensitivity to DNA-damaging drugs in a dose-dependent way. In human TC, however, the role of wild-type p53 functionality in chemotherapeutic response remains elusive. We analyzed functionality of wild-type p53 in cisplatin sensitivity in the human TC setting using a p53 short interfering (si)RNA approach. The cisplatin-sensitive TC cell line (Tera), the subline with acquired cisplatin resistance (Tera-CP) and a panel of intrinsically resistant TC cell lines (Scha and 2102EP), all expressing wild-type p53, were used. p53 and p53 transcriptional targets MDM2 and p21 (Waf1/Cip1) (p21) were expressed in a p53 transactivation-dependent way in all TC cell lines. Following cisplatin exposure, expression levels of p53 increased, with a subsequent increase in MDM2 and p21 mRNA and protein levels and Fas cell membrane levels. Downregulation of p53 with siRNA lowered cisplatin-induced apoptosis in Tera and Tera-CP, which was associated with a diminished Fas membrane expression. In contrast, p53 suppression augmented cisplatin-induced apoptosis in Scha and 2102EP and concomitantly strongly suppressed MDM2 and p21 mRNA and protein expression. Our results indicate that p53 is involved in transactivation of pro- and anti-apoptotic genes in untreated and cisplatin-treated TC cells, but subtle differences are present between TC cell lines. The opposite role of p53 in cisplatin-induced apoptosis among TC cell lines demonstrates the importance of the cellular context for the p53 transactivation phenotype in TC cells.

Apoptosis in cancer: from pathogenesis to treatment

Apoptosis is an ordered and orchestrated cellular process that occurs in physiological and pathological conditions. It is also one of the most studied topics among cell biologists. An understanding of the underlying mechanism of apoptosis is important as it plays a pivotal role in the pathogenesis of many diseases. In some, the problem is due to too much apoptosis, such as in the case of degenerative diseases while in others, too little apoptosis is the culprit. Cancer is one of the scenarios where too little apoptosis occurs, resulting in malignant cells that will not die. The mechanism of apoptosis is complex and involves many pathways. Defects can occur at any point along these pathways, leading to malignant transformation of the affected cells, tumour metastasis and resistance to anticancer drugs. Despite being the cause of problem, apoptosis plays an important role in the treatment of cancer as it is a popular target of many treatment strategies. The abundance of literature suggests that targeting apoptosis in cancer is feasible. However, many troubling questions arise with the use of new drugs or treatment strategies that are designed to enhance apoptosis and critical tests must be passed before they can be used safely in human subjects.

A cDNA microarray analysis identifies 52 genes associated with cis-diamminedichloroplatinum susceptibility in head and neck squamous cell carcinoma cell lines

We analyzed the cis-diamminedichloroplatinum (CDDP) susceptibility of ten head and neck squamous cell carcinoma (HNSCC) cell lines and found that this susceptibility varied significantly among the cell lines. Apoptotic cell death was predominant after the CDDP treatment, and a significant association was observed between the induction of apoptosis and the CDDP susceptibility. An analysis using a cDNA microarray consisting of 23,040 genes identified 52 genes that showed altered expression patterns between super-sensitive and super-resistant cell lines after the CDDP treatments. Using these 52 genes, we successfully distinguished the super-resistant cell lines from others. Our present results give us valuable clues to better understand the chemosensitivities of such cells to CDDP. This will improve the clinical management of patients with HNSCC.

Disruption of the MDM2-p53 interaction strongly potentiates p53-dependent apoptosis in cisplatin-resistant human testicular carcinoma cells via the Fas/FasL pathway

Wild-type p53 has a major role in the response and execution of apoptosis after chemotherapy in many cancers. Although high levels of wild-type p53 and hardly any TP53 mutations are found in testicular cancer (TC), chemotherapy resistance is still observed in a significant subgroup of TC patients. In the present study, we demonstrate that p53 resides in a complex with MDM2 at higher cisplatin concentrations in cisplatin-resistant human TC cells compared with cisplatin-sensitive TC cells. Inhibition of the MDM2–p53 interaction using either Nutlin-3 or MDM2 RNA interference resulted in hyperactivation of the p53 pathway and a strong induction of apoptosis in cisplatin-sensitive and -resistant TC cells. Suppression of wild-type p53 induced resistance to Nutlin-3 in TC cells, demonstrating the key role of p53 for Nutlin-3 sensitivity. More specifically, our results indicate that p53-dependent induction of Fas membrane expression (∼threefold) and enhanced Fas/FasL interactions at the cell surface are important mechanisms of Nutlin-3-induced apoptosis in TC cells. Importantly, an analogous Fas-dependent mechanism of apoptosis upon Nutlin-3 treatment is executed in wild-type p53 expressing Hodgkin lymphoma and acute myeloid leukaemia cell lines. Finally, we demonstrate that Nutlin-3 strongly augmented cisplatin-induced apoptosis and cell kill via the Fas death receptor pathway. This effect is most pronounced in cisplatin-resistant TC cells.

Overexpression of DDB2 enhances the sensitivity of human ovarian cancer cells to cisplatin by augmenting cellular apoptosis

Cisplatin is one of the most widely used anticancer agents, displaying activity against a wide variety of tumors. However, development of drug resistance presents a challenging barrier to successful cancer treatment by cisplatin. To understand the mechanism of cisplatin resistance, we investigated the role of damaged DNA binding protein complex subunit 2 (DDB2) in cisplatin-induced cytotoxicity and apoptosis. We show that DDB2 is not required for the repair of cisplatin-induced DNA damage, but can be induced by cisplatin treatment. DDB2-deficient noncancer cells exhibit enhanced resistance to cell growth inhibition and apoptosis induced by cisplatin than cells with fully restored DDB2 function. Moreover, DDB2 expression in cisplatin-resistant ovarian cancer cell line CP70 and MCP2 was lower than their cisplatin-sensitive parental A2780 cells. Overexpression of DDB2 sensitized CP70 cells to cisplatin-induced cytotoxicity and apoptosis via activation of the caspase pathway and downregulation of antiapoptotic Bcl-2 protein. Further analysis indicates that the overexpression of DDB2 in CP70 cells downregulates Bcl-2 expression through decreasing Bcl-2 mRNA level. These results suggest that ovarian cancer cells containing high level of DDB2 become susceptible to cisplatin by undergoing enhanced apoptosis.

MYC in oncogenesis and as a target for cancer therapies

MYC proteins (c-MYC, MYCN, and MYCL) regulate processes involved in many if not all aspects of cell fate. Therefore, it is not surprising that the MYC genes are deregulated in several human neoplasias as a result from genetic and epigenetic alterations. The near "omnipotency" together with the many levels of regulation makes MYC an attractive target for tumor intervention therapy. Here, we summarize some of the current understanding of MYC function and provide an overview of different cancer forms with MYC deregulation. We also describe available treatments and highlight novel approaches in the pursuit for MYC-targeting therapies. These efforts, at different stages of development, constitute a promising platform for novel, more specific treatments with fewer side effects. If successful a MYC-targeting therapy has the potential for tailored treatment of a large number of different tumors.

Antitumor effect and mechanisms of arsenic trioxide on subcutaneously implanted human gastric cancer in nude mice

We sought to investigate the efficacy of arsenic trioxide (As(2)O(3)) against a human gastric cell line implanted in nude mice in vivo, as well as the mechanism involved. The solid tumor model was created in nude mice with the gastric cancer cell line SGC-7901. The animals were randomly divided into three groups. As(2)O(3) was injected into animals in two arsenic-treated groups (2.5 mg/kg and 5 mg/kg), and the same volume of saline solution was injected into the control group. The inhibitory effect was observed in every group. Apoptotic cells and apoptotic bodies were observed by transmission electron microscope; the fraction of apoptotic cells was detected by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) under laser confocal technology. The expression of Fas and FasL was detected by immunohistochemical staining. In nude mice, after treatment with 5 mg/kg and 2.5 mg/kg As(2)O(3), approximately 50% and 30% tumor growth inhibition were observed, respectively (P < 0.05 for both treatment groups). Increase in apoptotic cells and apoptotic bodies appeared in As(2)O(3)-treated tumors compared with the control group. The fluorescence intensity levels of apoptotic cells in tumor were significantly higher in the arsenic-treated groups (P < 0.05 for both treatment groups). The fluorescence intensity level of apoptotic cells in the 5-mg/kg group was higher than that in the 2.5-mg/kg group (P < 0.05). The expression of Fas protein increased in dose- and time-dependent manner after the treatment with As(2)O(3), but that of FasL protein showed no significant difference between control and treated groups. As(2)O(3) did not induce hepatic and renal system injury in the nude mice. As(2)O(3) can inhibit the growth of human gastric cell implanted tumor. We ascribe this to upregulation of Fas, which can induce apoptosis of gastric cells.

Cellular stress responses: cell survival and cell death

Cells can respond to stress in various ways ranging from the activation of survival pathways to the initiation of cell death that eventually eliminates damaged cells. Whether cells mount a protective or destructive stress response depends to a large extent on the nature and duration of the stress as well as the cell type. Also, there is often the interplay between these responses that ultimately determines the fate of the stressed cell. The mechanism by which a cell dies (i.e., apoptosis, necrosis, pyroptosis, or autophagic cell death) depends on various exogenous factors as well as the cell's ability to handle the stress to which it is exposed. The implications of cellular stress responses to human physiology and diseases are manifold and will be discussed in this review in the context of some major world health issues such as diabetes, Parkinson's disease, myocardial infarction, and cancer.

Evasion of apoptosis as a cellular stress response in cancer

One of the hallmarks of human cancers is the intrinsic or acquired resistance to apoptosis. Evasion of apoptosis can be part of a cellular stress response to ensure the cell's survival upon exposure to stressful stimuli. Apoptosis resistance may contribute to carcinogenesis, tumor progression, and also treatment resistance, since most current anticancer therapies including chemotherapy as well as radio- and immunotherapies primarily act by activating cell death pathways including apoptosis in cancer cells. Hence, a better understanding of the molecular mechanisms regarding how cellular stress stimuli trigger antiapoptotic mechanisms and how this contributes to tumor resistance to apoptotic cell death is expected to provide the basis for a rational approach to overcome apoptosis resistance mechanisms in cancers.

Intratumoral dendritic cells and chemoradiation for the treatment of murine squamous cell carcinoma

Dendritic cells are potent antigen-presenting cells that have been shown to have significant antitumor effects in vitro and in vivo. However, the therapeutic efficacy of dendritic cells as an immunotherapeutic treatment has been limited by both immunologic tolerance and active immunosuppression in the tumor microenvironment. To address this problem, we examined the ability of concurrent systemic chemotherapy and local, fractionated radiation to augment intratumoral dendritic cell injections in a mouse model of squamous cell carcinoma. Intratumoral injections of dendritic cells alone did not have a significant antitumor effect in mice with squamous cell carcinoma flank tumors, but the addition of chemoradiation resulted in significant tumor regression. Concurrent chemoradiation alone resulted in slower tumor growth, but no complete tumor regressions. The combination of chemoradiation and intratumoral dendritic cell injections resulted in improved survival and complete tumor regression in 30% mice. Mice with complete tumor regression were partially resistant to the repeat challenge with relevant tumor 60 days after treatment. These findings were partially dependent on the presence of CD4 T cells, CD8 T cells, and natural killer cells. Chemoradiation may augment intratumoral dendritic cell injections through increased intratumoral apoptosis and decreased intratumoral regulatory T cells. This work suggests a possible role for the use of intratumoral dendritic cell therapy with more traditional chemoradiation strategies.

Tumor resistance to apoptosis

One of the hallmarks of human cancers is the intrinsic or acquired resistance to apoptosis. Evasion of apoptosis may contribute to carcinogenesis, tumor progression and also to treatment resistance, since most current anticancer therapies including chemotherapy, radio- and immunotherapy primarily act by activating cell death pathways including apoptosis in cancer cells. Hence, a better understanding of the molecular mechanisms underlying tumor resistance to apoptotic cell death is expected to provide the basis for a rational approach to develop molecular targeted therapies.

[Value of targeted treatment for testicular cancer: from molecular approaches to clinical possibilities]

Due to the introduction of tyrosine kinase-inhibitors in the treatment of metastatic renal cell cancer, targeted therapy raises hopes for other urological tumors as well. Even if excellent cure rates, achieved by standardization of diagnosis und therapy, have made testicular cancer a curable disease, up to 6% of young patients still die from tumors refractory to therapy. The quality of life of patients in advanced stages needing aggressive treatment should be improved by new therapies with reduced side effects. The role of tyrosine kinase inhibitors and angiogenesis inhibitors as well as intervention in the cell cycle and induction of apoptosis are discussed.

Apoptotic pathways in tumor progression and therapy

Apoptosis is a cell suicide program that plays a critical role in development and tissue homeostasis. The ability of cancer cells to evade this programmed cell death (PCD) is a major characteristic that enables their uncontrolled growth. The efficiency of chemotherapy in killing such cells depends on the successful induction of apoptosis, since defects in apoptosis signaling are a major cause of drug resistance. Over the past decades, much progress has been made in our understanding of apoptotic signaling pathways and their dysregulation in cancer progression and therapy. These advances have provided new molecular targets for proapoptotic cancer therapies that have recently been used in drug development. While most of those therapies are still at the preclinical stage, some of them have shown much promise in the clinic. Here, we review our current knowledge of apoptosis regulation in cancer progression and therapy, as well as the new molecular targeted molecules that are being developed to reinstate cancer cell death.

Oxidative stress and apoptosis: impact on cancer therapy

It is well established that some chemotherapeutic agents and radiation therapy generate reactive oxygen species (ROS) in patients during cancer therapy. Free radicals, particularly ROS have been proposed as common mediators for apoptosis. Recent studies have demonstrated that the mode of cell death depends on the severity of the oxidative damage. This review will address some of the current paradigms of oxidative stress, and antioxidants on apoptosis, and discuss the potential mechanisms by which oxidants can regulate apoptotic pathways. It will also review new developments in eliminating cancer cells by selectively inducing apoptosis.

Apoptosis and chemo-resistance in colorectal cancer

Systemic chemotherapy plays an integral part in treating advanced colorectal cancer. However 50% of patients respond poorly or have disease progression due to resistance to chemotherapeutic agents. This article reviews the pathways that regulate apoptosis, apoptotic mechanisms through which chemotherapeutic agents mediate their effect and how deregulation of apoptotic proteins may contribute to chemo-resistance. Also discussed are potential therapeutic strategies designed to target these proteins and thereby improve response rates to chemotherapy in colorectal cancer.

Classification of heavy-metal toxicity by human DNA microarray analysis

Microarray technology is proving to be a useful tool to classify undefined environmental toxicants, to investigate underlying mechanisms of toxicity, and to identify candidate toxicant-specific genetic markers by examining global effects of putative toxicants on gene expression profiles. The aim of this study was to evaluate the toxicities of six heavy metals through the comparison with gene expression patterns induced by well-known chemicals. For this purpose, we first identified the genes altered specifically in HepG2 under the exposure of 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), phenol, and N-nitrosodimethylamine (DMN), which were selected as the model chemicals, using DNA microarray. On the basis of the expression profiles of these genes, toxicities of six heavy metals, arsenic, cadmium, nickel, antimony, mercury, and chromium, were evaluated. The specific gene alteration and hierarchical clustering revealed that biological action of six heavy metals was clearly related to that of DMNQ which has been reported to be a reactive oxygen species (ROS) generating chemical and which induced the genes associated with cell proliferative responses. These results suggest that cell proliferative responses which are probably caused by ROS are a major apparent biological action of high-dose heavy metals, supporting the previous reports. Overall, a mechanism-based classification by DNA microarray would be an efficient method for evaluation of toxicities of environmental samples.

Suppression of human colon tumor growth by adenoviral vector-mediated NK4 expression in an athymic mouse model

AIM: To investigate the suppressive effects of adenoviral vector-mediated expression of NK4, an antagonist of hepatocyte growth factor (HGF), on human colon cancer in an athymic mouse model to explore the possibility of applying NK4 to cancer gene therapy.

METHODS: A human colon tumor model was developed by subcutaneous implantation of tumor tissue formed by LS174T cells grown in athymic mice. Fifteen tumor-bearing mice were randomized into three groups (n = 5 in each group) at d 3 after tumor implantation and mice were injected intratumorally with phosphate-buffered saline (PBS) or with recombinant adenovirus expressing β-galactosidase (Ad-LacZ) or NK4 (rvAdCMV/NK4) at a 6-d interval for total 5 injections in each mouse. Tumor sizes were measured during treatment to draw a tumor growth curve. At d 26 after the first treatment, all animals were sacrificed and the tumors were removed to immunohistochemically examine proliferating cell nuclear antigen (PCNA), microvessel density (represented by CD31), and apoptotic cells. In a separate experiment, 15 additional athymic mice were employed to develop a tumor metastasis model by intraperitoneal injection (ip) of LS174T cells. These mice were randomized into 3 groups (n = 5 in each group) at d 1 after injection and were treated by ip injection of PBS, or Ad-LacZ, or rvAdCMV/NK4 at a 6-d interval for total two injections in each mouse. All animals were sacrificed at d 14 and the numbers and weights of disseminated tumors within the abdominal cavity were measured.

RESULTS: Growth of human colon tumors were significantly suppressed in the athymic mice treated with rvAdCMV/NK4 (2537.4 ± 892.3 mm³) compared to those treated by either PBS (5175.2 ± 1228.6 mm³) or Ad-LacZ (5578.8 ± 1955.7 mm³) (P < 0.05). The tumor growth inhibition rate was as high as 51%. Immunohistochemical staining revealed a similar PCNA labeling index (75.1% ± 11.2% in PBS group vs 72.8% ± 7.6% in Ad-LacZ group vs 69.3% ± 9.4% in rvAdCMV/NK4 group) in all groups, but significantly lower microvessel density (10.7 ± 2.4 in rvAdCMV/NK4 group vs 25.6 ± 3.8 in PBS group or 21.3 ± 3.5 in Ad-LacZ group, P < 0.05), and a markedly higher apoptotic index (7.3% ± 2.4% in rvAdCMV/NK4 group vs 2.6 ± 1.1% in PBS group or 2.1% ± 1.5% in Ad-LacZ group, P < 0.05) in the rvAdCMV/NK4 group compared to the two control groups. In the tumor metastasis model, the number and weight of disseminated tumors of mice treated with rvAdCMV/NK4 were much lower than those of the control groups (tumor number: 6.2 ± 3.3 in rvAdCMV/NK4 group vs 22.9 ± 7.6 in PBS group or 19.8 ± 8.5 in Ad-LacZ group, P < 0.05; tumor weight: 324 ± 176 mg in rvAdCMV/NK4 group vs 962 ± 382 mg in PBS group or 1116 ± 484 mg in Ad-LacZ group, P < 0.05).

CONCLUSION: The recombinant adenovirus, rvAdCMV/NK4, can attenuate the growth of colon cancer in vivo, probably by suppressing angiogenesis and inducing tumor cell apoptosis, but not by direct suppression of tumor cell proliferation. Moreover, rvAdCMV/NK4 may inhibit peritoneal dissemination of colon cancer cells in a murine tumor metastasis model. These findings indicate that NK4 gene transfer may be an effective tool for the treatment of colon cancer.

Influence of antitumor drugs on the expression of Fas system in SW480 colon cancer cells

AIMS

To observe the influence of popular antitumor drugs [5-fluorouracil (5-FU), mitomycin (MMC), cisplatin (CP) and all-trans retinoic acid (ATRA)] on the expression of Fas system in SW480 colon cancer cells.

METHODS

The expressions of Fas/FasL protein and mRNA in colon cancer line SW480 cells before and after the treatment of the antitumor drugs (5-FU, MMC, CP and ATRA) were detected by immunocytochemistry, flow cytometry and reverse-transcriptase polymerase chain reaction. Coculture assays of colon cancer cells and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes. Apoptosis of Jurkat cells were detected by flow cytometry and fluorescence microscopy.

RESULTS

SW480 expressed high FasL and low Fas without drug treatments. When treated with 5-FU, Fas expression rates in SW480 increased, but FasL remained unchanged. Both Fas and FasL increased significantly when treated with MMC and CP. Most importantly, ATRA could induce SW480 cells to differentiate, increase the expression of Fas and decrease the expression of FasL. The coculture of SW480 cells and Jurkat cells confirmed the function of FasL in the SW480 cells.

CONCLUSION

Certain antitumor drugs can change the expression of the Fas system in SW480 cells in different ways. In vitro, MMC and CP can increase the sensitivity of colon cancer cells to apoptosis signals, but they possibly facilitate immune escape of tumor cells. 5-FU results in immune escape of colon cancer cells. ATRA can down-regulate the possibility of counterattack of colon cancer cells.

Extrinsic versus intrinsic apoptosis pathways in anticancer chemotherapy

Apoptosis or programmed cell death is a key regulator of physiological growth control and regulation of tissue homeostasis. One of the most important advances in cancer research in recent years is the recognition that cell death mostly by apoptosis is crucially involved in the regulation of tumor formation and also critically determines treatment response. Killing of tumor cells by most anticancer strategies currently used in clinical oncology, for example, chemotherapy, gamma-irradiation, suicide gene therapy or immunotherapy, has been linked to activation of apoptosis signal transduction pathways in cancer cells such as the intrinsic and/or extrinsic pathway. Thus, failure to undergo apoptosis may result in treatment resistance. Understanding the molecular events that regulate apoptosis in response to anticancer chemotherapy, and how cancer cells evade apoptotic death, provides novel opportunities for a more rational approach to develop molecular-targeted therapies for combating cancer.

Intratumor murine interleukin-12 gene therapy suppressed the growth of local and distant Ewing's sarcoma

We evaluated the effect of interleukin-12 (IL-12) gene therapy using an Ewing's sarcoma animal model in T-cell-deficient nude mice. Subcutaneous injection of TC71 cells resulted in tumor development by day 5. Mice were treated with a single intratumor injection of adenovirus beta-galactosidase (Ad.beta-gal) or adenovirus murine IL-12 (Ad.mIL-12) (2 x 10(9) PFU) and killed 1-7 days later. Reverse transcriptase-polymerase chain reaction analysis of tumor tissue demonstrated peak expression of IL-12 p35 and p40 at 48 h, which persisted up to 7 days. For in vivo therapy, mice received intratumor Ad.beta-gal or Ad.mIL-12 twice weekly for 2.5 weeks starting on day 6. Ad.mIL-12-treated tumors were significantly smaller (median volume, 19.7 mm3; range, 3.41-159.5 mm3) than Ad.beta-gal-treated tumors (median volume, 3214.9 mm3; range 1679.9-5909.8 mm3, P<0.003) on day 31. The weight of Ad.mIL-12-treated tumors was also lighter than the Ad.beta-gal-treated tumors (median, 2 mg; range, 1-5 mg versus median, 1960 mg; range 1640-5230 mg, P<0.01). Ad.mIL-12 therapy significantly prolonged the survival time and also inhibited the growth of an untreated tumor on the contralateral side. Immunohistochemistry analysis of the IL-12-treated tumors demonstrated IL-12 expression with increased Fas, Fas ligand and tumor cell apoptosis. CD31 and vascular endothelial growth factor expression were decreased. These data suggest that IL-12 gene therapy may be useful in the treatment of Ewing's sarcoma.

Caspase-8 promotes cell motility and calpain activity under nonapoptotic conditions

Significant caspase-8 activity has been found in normal and certain tumor cells, suggesting that caspase-8 possesses an alternative, nonapoptotic function that may contribute to tumor progression. In this article, we report that caspase-8 promotes cell motility. In particular, caspase-8 is required for the optimal activation of calpains, Rac, and lamellipodial assembly. This represents a novel nonapoptotic function of caspase-8 acting at the intersection of the caspase-8 and calpain proteolytic pathways to coordinate cell death versus cell motility signaling.

Intranasal interleukin-12 gene therapy enhanced the activity of ifosfamide against osteosarcoma lung metastases

BACKGROUND

Cyclophosphamide (CTX) and ifosfamide (IFX) are alkylating agents used to treat osteosarcoma (OS). It was previously demonstrated that the sensitivity of OS cells to 4-hydroperoxycyclophosphamide (4-HC, the active metabolite of CTX) is augmented by interleukin (IL)-12 in vitro through a mechanism involving the Fas/FasL pathway. The purpose of these studies was to determine whether this synergistic effect is operational in vivo.

METHODS

Mice were injected intravenously with human LM7 osteosarcoma cells. Treatment was initiated with IFX (2.5 mg/kg intraperitoneally) with or without intranasal polyethylenimine (PEI):IL-12 gene therapy given twice weekly for 6 weeks.

RESULTS

Expression of IL-12 protein in the lung was demonstrated in all mice receiving intranasal PEI:IL-12 but not in control mice or those treated with IFX alone. Increased expression of FasL was detected in lungs of all mice receiving IFX. Both IFX and PEI:IL-12 alone significantly inhibited lung metastasis when compared with control groups (P < 0.05). However, the most significant tumor effect was observed in mice receiving IFX+PEI:IL-12 (P < 0.01). Immunohistochemical staining for CD31 and basic fibroblast growth factor (bFGF) and the number of proliferating cells as quantified by proliferating cell nuclear antigen (PCNA) staining were also most significantly decreased in mice receiving combination therapy.

CONCLUSIONS

These data indicate that combining IFX and IL-12 may have therapeutic potential and that this increased efficacy may be mediated through a mechanism involving the Fas/FasL pathway.

Deciphering cellular states of innate tumor drug responses

BACKGROUND

The molecular mechanisms underlying innate tumor drug resistance, a major obstacle to successful cancer therapy, remain poorly understood. In colorectal cancer (CRC), molecular studies have focused on drug-selected tumor cell lines or individual candidate genes using samples derived from patients already treated with drugs, so that very little data are available prior to drug treatment.

RESULTS

Transcriptional profiles of clinical samples collected from CRC patients prior to their exposure to a combined chemotherapy of folinic acid, 5-fluorouracil and irinotecan were established using microarrays. Vigilant experimental design, power simulations and robust statistics were used to restrain the rates of false negative and false positive hybridizations, allowing successful discrimination between drug resistance and sensitivity states with restricted sampling. A list of 679 genes was established that intrinsically differentiates, for the first time prior to drug exposure, subsequently diagnosed chemo-sensitive and resistant patients. Independent biological validation performed through quantitative PCR confirmed the expression pattern on two additional patients. Careful annotation of interconnected functional networks provided a unique representation of the cellular states underlying drug responses.

CONCLUSION

Molecular interaction networks are described that provide a solid foundation on which to anchor working hypotheses about mechanisms underlying in vivo innate tumor drug responses. These broad-spectrum cellular signatures represent a starting point from which by-pass chemotherapy schemes, targeting simultaneously several of the molecular mechanisms involved, may be developed for critical therapeutic intervention in CRC patients. The demonstrated power of this research strategy makes it generally applicable to other physiological and pathological situations.

In vitro and In vivo Antitumor Effects of the Dual Insulin-Like Growth Factor-I/Insulin Receptor Inhibitor, BMS-554417

The insulin-like growth factor receptor (IGF-IR) and insulin receptor are either overactivated and/or overexpressed in a wide range of tumor types and contribute to tumorigenicity, proliferation, metastasis, and drug resistance. Here, we show that BMS-554417, a novel small molecule developed as an inhibitor of IGF-IR, inhibits IGF-IR and insulin receptor kinase activity and proliferation in vitro, and reduces tumor xenograft size in vivo. In a series of carcinoma cell lines, the IC50 for proliferation ranged from 120 nmol/L (Colo205) to >8.5 micromol/L (OV202). The addition of stimulatory ligands was unnecessary for the antiproliferative effect in MCF-7 and OV202 cells. BMS-554417 treatment inhibited IGF-IR and insulin receptor signaling through extracellular signal-related kinase as well as the phosphoinositide 3-kinase/Akt pathway, as evidenced by decreased Akt phosphorylation at Ser473. At doses that inhibited proliferation, the compound also caused a G0-G1 arrest and prevented nuclear accumulation of cyclin D1 in response to LR3 IGF-I. In Jurkat T-cell leukemia cells, this agent triggered apoptotic cell death via the mitochondrial pathway. BMS-554417 was orally bioavailable and significantly inhibited the growth of IGF1R-Sal tumor xenografts in vivo. BMS-554417 is a member of a novel class of IGF-IR/insulin receptor inhibitors that have potential clinical applications because of their antiproliferative and proapoptotic activity in vitro and in vivo.

Fas expression in lung metastasis from osteosarcoma patients

The authors' animal studies have shown that the metastatic potential of osteosarcoma (OS) cells correlates inversely with Fas expression-that is, Fas-negative cells metastasize but Fas-positive cells do not. One reason for this in the context of OS lung metastases may be that Fas-positive cells are eliminated by engagement with the Fas ligand (FasL) constitutively expressed on the surface of pneumocytes, whereas Fas-negative tumor cells are not. The purpose of this study was to determine the status of Fas expression in OS lung metastases from patients. Specifically, archived paraffin-embedded specimens of lung metastases from 38 patients with OS were analyzed by immunohistochemistry. Lung nodules from 23 of the 38 patients (60%) were Fas negative, those from 12 patients (32%) were weakly positive, and that from only 1 patient (3%) was strongly positive. Findings in the samples from the remaining two patients (5%) could not be interpreted because of extensive necrosis. Most patients with the weakly positive tumors and the single patient with the strongly positive tumor received chemotherapy prior to lung resection. There was a significant correlation between Fas expression and the administration of preoperative salvage chemotherapy (P = 0.0013). These data indicate that loss of Fas may be one mechanism by which OS cells evade host resistance in the lung. Chemotherapy may induce regression by upregulating Fas.

Regulation of interleukin-2 induced soluble Fas ligand release from human peripheral blood mononuclear cells

Adjuvant interleukin (IL)-2 immunotherapy has been used in the treatment of different malignant dieseases. However, clinical results have been rather disappointing. Therefore, further investigations on IL-2-induced mediators of cytotoxicity seem to be necessary in order to possibly create cytokine cocktails which could enhance the IL-2-induced cytotoxicity. We therefore investigated the regulation of IL-2-induced release of soluble Fas Ligand (sFasL), since this factor is known to possess anti-tumor activities. In CD3-stimulated peripheral blood mononuclear cells IL-2 induced sFasL in a dose-dependent fashion. Maximum sFasL concentrations were obtained after stimulation of MNC for 120 hrs. Inhibition of endogenous IL-12 production significantly reduced IL-2-mediated sFasL release by about 25%. In contrast, addition of IL-12 enhanced the IL-2-induced sFasL about 1,5-fold. IL-10 and IL-4 reduced the IL-2-stimulated sFasL by about 30%. Interestingly, these suppressive effects could be antagonized by the addition of IL-12. Not only exogenous IL-10 but also endogenously produced IL-10 decreased the sFasL release to that extent which had been stimulated by IL-12. Since IL-12 and IL-10 only marginally influenced the IL-2-mediated cell proliferation as well as the IL-2-induced cell death, the IL-12- and IL-10-controlled sFasL release seems to be based on an enhanced production per cell. However, the increase in cell numbers as well as the decrease of viability during cell culture might additionally contribute to the IL-2-induced increase of sFasL release. This secondary effect might explain why IL-2-mediated sFasL production is only partially controlled by regulatory cytokines such as IL-4, IL-10 or IL-12. In conclusion, addition of IL-12 might increase the efficacy of IL-2 immunotherapy by inhibition of the IL-10-mediated negative feed-back loop on IL-2-mediated sFasL release.

Cancer-specific toxicity of apoptin is independent of death receptors but involves the loss of mitochondrial membrane potential and the release of mitochondrial cell-death mediators by a Nur77-dependent pathway

Apoptin, a small proline-rich protein derived from the chicken anaemia virus, induces cell death selectively in cancer cells. The signalling pathways of apoptin-induced, cancer cell-selective apoptosis are not well understood. Here, we demonstrate that apoptin triggers apoptosis by activating the mitochondrial/intrinsic pathway, and that it acts independently of the death receptor/extrinsic pathway. Jurkat cells deficient in either FADD or caspase-8 (which are both necessary for the extrinsic pathway) were equally as sensitive to apoptin as their parental clones. This demonstrates that apoptin is likely to act through the mitochondrial death pathway. Apoptin treatment causes a loss of mitochondrial membrane potential, and release of the mitochondrial proteins cytochrome c and apoptosis-inducing factor. Apoptin-induced cell death is counteracted by the anti-apoptotic Bcl-2 family members, Bcl-2 itself and Bcl-XL, as shown in Jurkat leukaemia cells. In addition, we describe the processing and activation of caspase-3. By contrast, cleavage of caspase-8, which is predominantly triggered by the death receptor pathway, is not observed. Furthermore, apoptin triggers the cytoplasmic translocation of Nur77, and the inhibition of Nur77 expression by siRNA significantly protects MCF7 cells from apoptin-triggered cell death. Thus, our data indicate that the apoptin death signal(s) ultimately converges at the mitochondria, and that it acts independently of the death receptor pathway.

Induction of reactive oxygen intermediates-dependent programmed cell death in human malignant ex vivo glioma cells and inhibition of the vascular endothelial growth factor production by taurolidine

OBJECT

Taurolidine, a derivative of the amino acid taurin, was recently found to display a potent antineoplastic effect both in vitro and in vivo. The authors therefore initiated studies to assess the potential antineoplastic activity of taurolidine in human glioma cell lines and in ex vivo malignant cell cultures. They also studied the mechanisms that induce cell death and the impact of taurolidine on tumor-derived vascular endothelial growth factor (VEGF) production.

METHODS

Cytotoxicity and clonogenic assays were performed using crystal violet staining. In the cytotoxicity assay 100% of glioma cell lines (eight of eight) and 74% of ex vivo glioma cultures (14 of 19) demonstrated sensitivity to taurolidine, with a mean median effective concentration (EC50) of 51 +/- 28 microg/ml and 56 +/- 23 microg/ml, respectively. Colony formation was inhibited by taurolidine, with a mean EC50 of 7 +/- 3 microg/ml for the cell lines and a mean EC50 of 3.5 +/- 1.7 microg/ml for the ex vivo glioma cultures. On observing this high activity of taurolidine in both assays, the authors decided to evaluate its cell death mechanisms. Fragmentation of DNA, externalization of phosphatidylserine, activation of poly(adenosine diphosphate-ribose) polymerase, loss of the mitochondrial membrane potential followed by a release of apoptosis-inducing factor, and typical apoptotic features were found after taurolidine treatment. Cell death was preceded by the generation of reactive O2 intermediates, which was abrogated by N-acetylcysteine but not by benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Moreover, taurolidine also induced suppression of VEGF production on the protein and messenger RNA level, as shown by an enzyme-linked immunosorbent assay and by reverse transcription-polymerase chain reaction.

CONCLUSIONS

Given all these findings, taurolidine may be a promising new agent in the treatment of malignant gliomas; it displays a combination of antineoplastic and antiangiogenic activities, inducing tumor cell apoptosis and inhibiting tumor-derived VEGF production.

Gene expression profiling of the irinotecan pathway in colorectal cancer

The exact mechanism responsible for large variation of response to chemotherapy remains unclear. This study profiled the gene expression for the entire irinotecan pathway to provide insights into individualized cancer therapy. The RNA expressions of 24 irinotecan pathway genes were measured in paired tumor and normal tissues from 52 patients with Dukes' C colorectal cancer using a real-time quantitative reverse transcription-PCR assay. The relative expression levels across the 24 pathway genes varied considerably, with a 441-fold range from highest to lowest expression levels for the tumor tissues and a 934-fold range for the normal tissues. Interpatient variability was also quite large, with a 33.6 median fold change in the tumor tissue genes and a 30.1 median fold change in the normal tissue genes. Six of the 24 irinotecan pathway genes had dramatically lower expression levels in the tumor samples than did the genes in the normal tissues (median range, 1.28-4.39 folds; P = 0.001-0.029). Eight genes had significantly higher levels (median range, 1.35-2.42 folds; P = 0.001-0.011). Using hierarchical clustering, three gene clusters and three patient groups were observed with high similarity indices by the RNA expressions in colorectal tumors. The three patient groups had no unique clinical pathologic features but could be differentiated by the statistically significant differences in RNA expression level of seven genes. Our study indicates that gene expression profiling could be valuable for predicting tumor response to chemotherapy and for tailoring therapy to individual cancer patients.

Indomethacin-induced activation of the death receptor-mediated apoptosis pathway circumvents acquired doxorubicin resistance in SCLC cells

Small-cell lung cancers (SCLCs) initially respond to chemotherapy but are often resistant at recurrence. A potentially new method to overcome resistance is to combine classical chemotherapeutic drugs with apoptosis induction via tumour necrosis factor (TNF) death receptor family members such as Fas. The doxorubicin-resistant human SCLC cell line GLC₄-Adr and its parental doxorubicin-sensitive line GLC₄ were used to analyse the potential of the Fas-mediated apoptotic pathway and the mitochondrial apoptotic pathway to modulate doxorubicin resistance in SCLC. Western blotting showed that all proteins necessary for death-inducing signalling complex formation and several inhibitors of apoptosis were expressed in both lines. The proapototic proteins Bid and caspase-8, however, were higher expressed in GLC₄-Adr. In addition, GLC₄-Adr expressed more Fas (3.1x) at the cell membrane. Both lines were resistant to anti-Fas antibody, but plus the protein synthesis inhibitor cycloheximide anti-Fas antibody induced 40% apoptosis in GLC₄-Adr. Indomethacin, which targets the mitochondrial apoptotic pathway, induced apoptosis in GLC₄-Adr but not in GLC₄ cells. Surprisingly, in GLC₄-Adr indomethacin induced caspase-8 and caspase-9 activation as well as Bid cleavage, while both caspase-8 and caspase-9 specific inhibitors blocked indomethacin-induced apoptosis. In GLC₄-Adr, doxorubicin plus indomethacin resulted in elevated caspase activity and a 2.7-fold enhanced sensitivity to doxorubicin. In contrast, no effect of indomethacin on doxorubicin sensitivity was observed in GLC₄. Our findings show that indomethacin increases the cytotoxic activity of doxorubicin in a doxorubicin-resistant SCLC cell line partly via the death receptor apoptosis pathway, independent of Fas.

Cellular processing of platinum anticancer drugs

Cisplatin, carboplatin and oxaliplatin are platinum-based drugs that are widely used in cancer chemotherapy. Platinum-DNA adducts, which are formed following uptake of the drug into the nucleus of cells, activate several cellular processes that mediate the cytotoxicity of these platinum drugs. This review focuses on recently discovered cellular pathways that are activated in response to cisplatin, including those involved in regulating drug uptake, the signalling of DNA damage, cell-cycle checkpoints and arrest, DNA repair and cell death. Such knowledge of the cellular processing of cisplatin adducts with DNA provides valuable clues for the rational design of more efficient platinum-based drugs as well as the development of new therapeutic strategies.

Exploiting death receptor signaling pathways for tumor therapy

Apoptosis or programmed cell death is a key regulator of physiological growth control and regulation of tissue homeostasis. Tipping the balance between cell death and proliferation in favor of cell survival may result in tumor formation. Moreover, current cancer therapies, e.g. chemotherapy, gamma-irradiation, immunotherapy or suicide gene therapy, primarily exert their antitumor effect by triggering an evolutionary conserved apoptosis program in cancer cells. For example, death receptor signaling has been implied to contribute to the efficacy of cancer therapy. Thus, failure to undergo apoptosis in response to anticancer therapy because of defects in death receptor pathways may result in resistance. Further insights into the mechanisms regulating apoptosis in response to anticancer therapy and how cancer cells evade cell death may provide novel opportunities for targeted therapeutics. Thus, agents designed to selectively activate death receptor pathways may enhance the efficacy of conventional therapies and may even overcome some forms of cancer resistance.

WP744 is a novel anthracycline with enhanced activity against neuroblastoma

BACKGROUND

Doxorubicin (Dox) is one of the most useful chemotherapeutic agents for patients with advanced neuroblastoma (NB). A series of Dox analogs with bulky substitutions at the C-4' at amino-sugar have been designed to impair interactions between the drug and P-glycoprotein (P-gp), a multidrug drug resistance (MDR) transporter. Two analogs, WP744 and WP769, were selected and their biological properties were compared with Dox and the daunorubicin-based bisintercalator WP631. These novel Dox analogs may have antitumor activity beyond MDR evasion.

MATERIALS AND METHODS

MTT assays were used to determine the potency of three structurally altered Dox analogs against a panel of NB cell lines with and without amplification of the MYCN oncogene. Flow cytometry (FCM) was used to analyze apoptosis and cell death and phenotype cell lines for surface expression of the MDR protein P-gp.

RESULTS

The 4'-O-benzylated Dox analogs WP744 and WP769 were 2 to 36 times more cytotoxic than Dox for the NB cell lines tested. The bis-intercalator WP631, despite its significantly greater affinity for DNA (>10,000-fold), was generally less potent against NB than Dox. In Tet21N cells, which conditionally express MYCN, greatly enhanced (nearly 6-fold) sensitivity to WP744 killing was seen when this oncogene was induced, while enhanced sensitivity to Dox was more modest (2-fold) under MYCN-induced conditions. Treatment with WP744 also resulted in enhanced apoptosis. Apoptosis, but not cell death, in response to either WP744 or Dox was inhibited by caspase inhibition, suggesting that cell death was not completely dependent upon apoptosis. P-gp expression was detectable on five NB cell lines. WP744 was more cytotoxic than Dox against both P-gp+ and P-gp- cells.

CONCLUSIONS

These findings demonstrate that 4'-O-benzylation of the anthracycline molecule significantly enhances potency against NB independent of MYCN status, caspase activation, and MDR phenotype. However, WP744 demonstrated a unique synergy with MYCN for cell killing when this oncogene was specifically induced. WP744 may be more useful than conventional agents for the treatment of tumor clones that harbor defects in apoptotic pathways, in those with MYCN amplification, and in those with drug-resistant tumors.