Induction of apoptosis through the activation of SAPK/JNK followed by the expression of death receptor Fas in X-irradiated cells

Current trends in the promising immune checkpoint inhibition and radiotherapy combination for locally advanced and metastatic urothelial carcinoma

Locally advanced and metastatic urothelial carcinoma (UC) remains a challenging malignancy, though several novel therapeutic drugs have been developed in recent years. Over the past decade, immune checkpoint inhibitors (ICI) have shifted the paradigm of therapeutic strategies for UC; however, only a limited number of patients respond to ICI. Since radiotherapy (RT) is widely known to induce systemic immune activation, it may boost the efficacy of ICI. Conversely, RT also causes exhaustion of cytotoxic T cells, and the activation and recruitment of immunosuppressive cells; ICI may help overcome these immunosuppressive effects. Therefore, the combination of ICI and RT has attracted attention in recent years. The therapeutic benefits of this combination therapy and its optimal regimen have not yet been determined through prospective studies. Therefore, this review article aimed to provide an overview of the current preclinical and clinical studies that illustrate the underlying mechanisms and explore the optimization of the RT regimen along with the ICI and RT combination sequence. We also analyzed ongoing prospective studies on ICI and RT combination therapies for metastatic UC. We noted that the tumor response to ICI and RT combination seemingly differs among cancer types. Thus, our findings highlight the need for well-designed prospective trials to determine the optimal combination of ICI and RT for locally advanced and metastatic UC.

Immunotherapies landscape and associated inhibitors for the treatment of cervical cancer

Cervical cancer ranks as the fourth most common form of cancer worldwide. There is a large number of situations that may be examined in the developing world. The risk of contracting HPV (Human Papillomavirus) due to poor sanitation and sexual activity is mostly to blame for the disease's alarming rate of expansion. Immunotherapy is widely regarded as one of the most effective medicines available. The immunotherapy used to treat cervical cancer cells relies on inhibitors that block the immune checkpoint. The poly adenosine diphosphate ribose polymer inhibited cervical cancer cells by activating both the programmed death 1 (PD-1) and programmed death ligand 1 (CTLA-1) checkpoints, a strategy that has been shown to have impressive effects. Yet, immunotherapy directed towards tumors that have already been invaded by lymphocytes leaves a positive imprint on the healing process. Immunotherapy is used in conjunction with other treatments, including chemotherapy and radiation, to provide faster and more effective outcomes. In this combination therapy, several medications such as Pembrolizumab, Durvalumab, Atezolizumab, and so on are employed in clinical trials. Recent developments and future predictions suggest that vaccinations will soon be developed with the dual goal of reducing the patient's susceptibility to illness while simultaneously strengthening their immune system. Many clinical and preclinical studies are now investigating the effectiveness of immunotherapy in slowing the progression of cervical cancer. The field of immunotherapy is expected to witness more progress toward improving outcomes. Immunotherapies landscape and associated inhibitors for the treatment of Cervical Cancer.

Selective multimodal bladder-sparing therapy for muscle-invasive bladder cancer: the present and the future

INTRODUCTION

Despite the lack of level 1 evidence, selective bladder-sparing therapy using trimodal therapy is currently recommended by guidelines as a standard of care in patients with non-metastatic, muscle-invasive bladder cancer who are eligible for the treatment.

AREAS COVERED

This article reviews major studies of selective, bladder-sparing therapy utilizing multiple modalities for muscle-invasive bladder cancer and those comparing the oncological outcomes between bladder-sparing therapy and radical cystectomy. Also discussed are predictive biomarkers potentially capable of guiding treatment decisions by patients with muscle-invasive bladder cancer and a novel strategy for boosting the antitumor immune response in bladder-sparing therapy. PubMed databases were searched for records of 30 June 2023 or earlier.

EXPERT OPINION

Selective, bladder-sparing therapy appears to be underutilized at present. To promote its use, measures should be taken to facilitate the referral of eligible patients to specialist centers and broaden the number of facilities providing the therapy. Recent studies have suggested a prognostic benefit of radiotherapy for the primary lesion in patients with metastatic bladder cancer. Given that irradiation can induce the abscopal effect, particularly in combination with immune checkpoint inhibitors, demand for bladder-sparing therapies may increase in the context of treatments for metastases.

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Chromosomal Location of Genes Differentially Expressed in Tumor Cells Surviving High-Dose X-ray Irradiation: A Preliminary Study on Radio-Fragile Sites

Altered gene expression is a common feature of tumor cells after irradiation. Our previous study showed that this phenomenon is not only an acute response to cytotoxic stress, instead, it was persistently detected in tumor cells that survived 10 Gy irradiation (IR cells). The current understanding is that DNA double-strand breaks (DSBs) are recognized by the phosphorylation of histone H2AX (H2AX) and triggers the ataxia-telangiectasia mutated (ATM) protein or the ATM- and Rad3-related (ATR) pathway, which activate or inactivate the DNA repair or apoptotic or senescence related molecules and causes the expression of genes in many instances. However, because changes in gene expression persist after passaging in IR cells, it may be due to the different pathways from these transient intracellular signaling pathways caused by DSBs. We performed microarray analysis of 30,000 genes in radiation-surviving cells (H1299-IR and MCF7-IR) and found an interesting relation between altered genes and their chromosomal loci. These loci formed a cluster on the chromosome, especially on 1q21 and 6p21-p22 in both irradiated cell lines. These chromosome sites might be regarded as “radio-fragile” sites.

Combining radiation therapy and immunotherapy for lung cancers: a narrative review

Lung cancer remains the leading cause of cancer morbidity and mortality worldwide among both men and women. While surgical resection remains the standard of care for early stage NSCLC, chemoradiation has been a mainstay of treatment for locally advanced non-small-cell lung cancer (LA-NSCLC) patients for decades. Consolidation immunotherapy has improved survival in this subset of patients after conventional chemoradiation, and has emerged as the new standard. The synergy between immunotherapy and radiation, as well as ongoing research on the effects of radiation on the immune system, allows for the exploration of new avenues in the treatment of LA-NSCLC. In addition to the use of durvalumab as consolidative systemic therapy after concurrent chemoradiotherapy for Stage III NSCLC, other combination regimens have been shown to be effective in various disease stages in preclinical and clinical studies. These regimens include CTLA-4 and PD/PDL-1 checkpoint inhibitors combined with radiation treatment. While these combined regimens have demonstrated efficacy, they are not without toxicity, and require additional evaluation when combined with radiation. In this review, we have summarized the immunostimulatory and immunosuppressive effects of radiation therapy. We also evaluate the current evidence and ongoing research supporting the combination of radiotherapy and immunotherapy across early to LA-NSCLC.

Differentiation Induction as a Response to Irradiation in Neural Stem Cells In Vitro

Radiotherapy plays a significant role in brain cancer treatment; however, the use of this therapy is often accompanied by neurocognitive decline that is, at least partially, a consequence of radiation-induced damage to neural stem cell populations. Our findings describe features that define the response of neural stem cells (NSCs) to ionizing radiation. We investigated the effects of irradiation on neural stem cells isolated from the ventricular-subventricular zone of mouse brain and cultivated in vitro. Our findings describe the increased transcriptional activity of p53 targets and proliferative arrest after irradiation. Moreover, we show that most cells do not undergo apoptosis after irradiation but rather cease proliferation and start a differentiation program. Induction of differentiation and the demonstrated potential of irradiated cells to differentiate into neurons may represent a mechanism whereby damaged NSCs eliminate potentially hazardous cells and circumvent the debilitating consequences of cumulative DNA damage.

Combining Radiotherapy With Anti-angiogenic Therapy and Immunotherapy; A Therapeutic Triad for Cancer?

Radiotherapy has been used for the treatment of cancer for over a century. Throughout this period, the therapeutic benefit of radiotherapy has continuously progressed due to technical developments and increased insight in the biological mechanisms underlying the cellular responses to irradiation. In order to further improve radiotherapy efficacy, there is a mounting interest in combining radiotherapy with other forms of therapy such as anti-angiogenic therapy or immunotherapy. These strategies provide different opportunities and challenges, especially with regard to dose scheduling and timing. Addressing these issues requires insight in the interaction between the different treatment modalities. In the current review, we describe the basic principles of the effects of radiotherapy on tumor vascularization and tumor immunity and vice versa. We discuss the main strategies to combine these treatment modalities and the hurdles that have to be overcome in order to maximize therapeutic effectivity. Finally, we evaluate the outstanding questions and present future prospects of a therapeutic triad for cancer.

Radiotherapy as a New Player in Immuno-Oncology

Recent development in radiation biology has revealed potent immunogenic properties of radiotherapy in cancer treatments. However, antitumor immune effects of radiotherapy are limited by the concomitant induction of radiation-dependent immunosuppressive effects. In the growing era of immunotherapy, combining radiotherapy with immunomodulating agents has demonstrated enhancement of radiation-induced antitumor immune activation that correlated with improved treatment outcomes. Yet, how to optimally deliver combination therapy regarding dose-fractionation and timing of radiotherapy is largely unknown. Future prospective testing to fine-tune this promising combination of radiotherapy and immunotherapy is warranted.

Cellular effects of a turmeric root and rosemary leaf extract on canine neoplastic cell lines

BACKGROUND

The use of nutraceuticals is gaining in popularity in human and canine oncology with a relatively limited understanding of the effects in the vastly different tumor types seen in canine oncology. We have previously shown that turmeric root (TE) and rosemary leaf (RE) extracts can work synergistically to reduce neoplastic cell growth, but the mechanisms are poorly understood and require further elucidation.

RESULTS

Three different canine cell lines (C2 mastocytoma, and CMT-12 mammary carcinoma, D17 osteosarcoma) were treated with 6.3 μg mL^-1 extract individually, or 3.1 μg mL^-1 of each extract in combination based on studies showing synergy of these two extracts. Apoptosis, antioxidant effects, cellular accumulation of curcumin, and perturbation of signaling pathways were assessed. The TE + RE combination treatment resulted in Caspase 3/7 activation and apoptosis in all cell lines, beyond the effects of TE alone with the CMT-12 cell line being most susceptible. Both extracts had antioxidant effects with RE reducing reactive oxygen species (ROS) by 40-50% and TE reducing ROS by 80-90%. In addition RE treatment enhanced the c-jun N-terminal kinase (JNK) activity in the C2 cell line and TE + RE exposure increased activated JNK by 4-5 times in the CMT-12 cell line. Upon further examination, it was found that RE treatment caused a significant increase in the cellular accumulation of curcumin by approximately 30% in the C2 and D17 cell lines, and by 4.8-fold in the CMT-12 cell line. This increase in intracellular curcumin levels may play a role in the synergy exhibited when using TE and RE in combination.

CONCLUSIONS

The use of RE in combination with TE induces a synergistic response to induce apoptosis which is better than either extract alone. This appears to be related to a variable increased TE uptake in cells and activation of pathways involved in the apoptotic response.

Aspirin-induced heat stress resistance in chicken myocardial cells can be suppressed by BAPTA-AM in vitro

Our recent studies have displayed the protective functions of aspirin against heat stress (HS) in chicken myocardial cells, and it may be associated with heat shock proteins (HSPs). In this study, we further investigated the potential role of HSPs in the aspirin-induced heat stress resistance. Four of the most important HSPs including HspB1 (Hsp27), Hsp60, Hsp70, and Hsp90 were induced by aspirin pretreatment and were suppressed by BAPTA-AM. When HSPs were induced by aspirin, much slighter HS injury was detected. But more serious damages were observed when HSPs were suppressed by BAPTA-AM than those cells exposed to HS without BAPTA-AM, even the myocardial cells have been treated with aspirin in prior. Comparing to other HSPs, HspB1 presented the largest increase after aspirin treatments, 86-fold higher than the baseline (the level before HS). These findings suggested that multiple HSPs participated in aspirin's anti-heat stress function but HspB1 may contribute the most. Interestingly, during the experiments, we also found that apoptosis rate as well as the oxidative stress indicators (T-SOD and MDA) was not consistently responding to heat stress injury as expected. By selecting from a series of candidates, myocardial cell damage-related enzymes (CK-MB and LDH), cytopathological tests, and necrosis rate (measured by flow cytometry assays) are believed to be reliable indicators to evaluate heat stress injury in chicken's myocardial cells and they will be used in our further investigations.

Effects of Chronic Low-Dose Radiation on Human Neural Progenitor Cells

The effects of chronic low-dose radiation on human health have not been well established. Recent studies have revealed that neural progenitor cells are present not only in the fetal brain but also in the adult brain. Since immature cells are generally more radiosensitive, here we investigated the effects of chronic low-dose radiation on cultured human neural progenitor cells (hNPCs) derived from embryonic stem cells. Radiation at low doses of 31, 124 and 496 mGy per 72 h was administered to hNPCs. The effects were estimated by gene expression profiling with microarray analysis as well as morphological analysis. Gene expression was dose-dependently changed by radiation. By thirty-one mGy of radiation, inflammatory pathways involving interferon signaling and cell junctions were altered. DNA repair and cell adhesion molecules were affected by 124 mGy of radiation while DNA synthesis, apoptosis, metabolism, and neural differentiation were all affected by 496 mGy of radiation. These in vitro results suggest that 496 mGy radiation affects the development of neuronal progenitor cells while altered gene expression was observed at a radiation dose lower than 100 mGy. This study would contribute to the elucidation of the clinical and subclinical phenotypes of impaired neuronal development induced by chronic low-dose radiation.

Radiation and checkpoint blockade immunotherapy: radiosensitisation and potential mechanisms of synergy

Checkpoint blockade immunotherapy has received mainstream attention as a result of striking and durable clinical responses in some patients with metastatic disease and a reasonable response rate in many tumour types. The activity of checkpoint blockade immunotherapy is not restricted to melanoma or lung cancer, and additional indications are expected in the future, with responses already reported in renal cancer, bladder cancer, and Hodgkin's lymphoma among many others. Additionally, the interactions between radiation and the immune system have been investigated, with several studies describing the synergistic effects on local and distant tumour control when radiation therapy is combined with immunotherapy. Clinical enthusiasm for this approach is strengthened by the many ongoing trials combining immunotherapy with definitive and palliative radiation. Herein, we discuss the biological and mechanistic rationale behind combining radiation with checkpoint blockade immunotherapy, with a focus on the preclinical data supporting this potentially synergistic combination. We explore potential hypotheses and important considerations for clinical trial designs. Finally, we reintroduce the notion of radiosensitising immunotherapy, akin to radiosensitising chemotherapy, as a potential definitive therapeutic modality.

Inflammation-induced ROS generation causes pancreatic cell death through modulation of Nrf2/NF-κB and SAPK/JNK pathway

Chronic pancreatitis is characterized by progressive loss of exocrine and endocrine functions of the pancreas and is considered to be the single most important cause for development of pancreatic cancer. Recent evidence suggests that inflammation and oxidative stress play pivotal roles in the development of clinical conditions like pancreatitis, type 2 diabetes mellitus, and metabolic syndrome. Nonetheless, molecular signaling pathways linking inflammation, oxidative stress, and pancreatic cell death are not yet well defined. In this study, bacterial lipopolysaccharide (LPS) was used (injected twice a week for three weeks) to emulate a chronic systemic inflammatory state in experimental Swiss albino mice. Using this model, we traced the genesis of inflammation-induced pancreatic dysfunction and mapped the signaling events which contribute to the induction of this state. Histopathological studies revealed the appearance of cell injuries and increased collagen content in LPS-exposed group, indicative of fibrosis. Assays for intraperitoneal glucose tolerance, insulin levels, and insulin receptor mRNA expression signified inflammation-induced insulin insensitivity. For the first time we present evidence that cellular inflammation and subsequent oxidative stress modulate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/NF-E2-related factor 2 or Nuclear factor (erythroid-derived 2)-like 2 pathway and initiates pancreatic cell death by activation of stress-responsive Rho/stress-activated protein kinase or SAPK/Jun-N-terminal kinase (JNK) pathway. Scavenging of intracellular reactive oxygen species (ROS) by a standard antioxidant N-acetyl cysteine led to pancreatic cell survival. The data obtained strongly indicates that the LPS/toll-like receptor-4 or TLR-4/ROS/NF-κB pathway is critically involved in the initiation of inflammation, oxidative stress, and pancreatic cell death and might prove to be an excellent choice as a target for novel therapeutic strategies in the management of metabolic disorders.

Molecular mechanism of acute radiation enteritis revealed using proteomics and biological signaling network analysis in rats

BACKGROUND AND AIMS

Radiation enteritis (RE) has emerged as a significant complication that can progress to severe gastrointestinal disease and the mechanisms underlying its genesis remain poorly understood. The aim of this study was to identify temporal changes in protein expression potentially associated with acute inflammation and to elucidate the mechanism underlying radiation enteritis genesis.

METHODS

Male Sprague-Dawley rats were irradiated in the abdomen with a single dose of 10 Gy to establish an in vivo model of acute radiation enteritis. Two-dimensional fluorescence difference gel electrophoresis, matrix-assisted laser desorption/ionization time-of-flight spectrometer (MALDI-TOF) tandem mass spectrometry, and peptide mass fingerprinting were used to determine differentially expressed proteins between normal and inflamed intestinal mucosa. Additionally, differentially expressed proteins were evaluated by KO Based Annotation System to find the biological functions associated with acute radiation enteritis.

RESULTS

Intensity changes of 86 spots were detected with statistical significance (ratio ≥ 1.5 or ≤ 1.5, P < 0.05). Sixty one of the 86 spots were identified by MALDI-TOF/TOF tandem mass spectrometry. These radiation-induced proteins with biological functions showed that the FAS pathway and glycolysis signaling pathways were significantly altered using the KOBAS tool.

CONCLUSIONS

Our results reveal an underlying mechanism of radiation-induced acute enteritis, which may help clarify the pathogenesis of RE and point to potential targets for therapeutic interventions.

Crosstalk between Fas and JNK determines lymphocyte apoptosis after ionizing radiation

Radiation simultaneously activate Fas and JNK pathway in lymphocytes but their precise interaction is not clearly understood. Activation of Fas pathway is required for radiation induced apoptosis, however induction of JNK pathway may or may not contribute in apoptosis. Here we report that Fas, Fas associated death domain and total JNK are activated in a dose- and time-dependent radiation exposure. A biphasic pattern of phospho-JNK was found at lower doses (1 and 2 Gy), however at higher doses of radiation phospho-JNK was continuously activated. Interestingly, Fas ligand expression remained biphasic at all the doses of radiation. Our results suggest that the Fas pathway is the major player in radiation-induced apoptosis, with JNK playing a contributory role. We also observed that Fas ligand expression by radiation is dependent on JNK activation. We also propose that radiation activates JNK pathway, but sustained activation is required for maximal induction of apoptosis at later times. Our findings define a mechanism for crosstalk between JNK and Fas pathway in radiation-induced apoptosis, which may lead to the development of new therapeutic strategies.

Targeting radioresistant osteosarcoma cells with parthenolide

Osteosarcoma is a devastating tumor of bone, primarily affecting adolescents. Osteosarcoma tumors are notoriously radioresistant. Radioresistant cancers, including osteosarcoma, typically exhibit a considerable potential for relapse and development of metastases following treatment. Relapse and metastatic potential can, in part, be due to a specific radioresistant subpopulation of cells with stem-like characteristics, cancer stem cells, which maintain the capacity to regenerate entire tumors. In the current study, we have investigated whether in vitro treatments with parthenolide, a naturally occurring small molecule that interferes with NF-κB signaling and has various other effects, will re-sensitize cancer stem cells and the entire cell population to radiotherapy in osteosarcoma. Our results indicate that parthenolide and ionizing radiation synergistically induce cell death in LM7 osteosarcoma cells. Importantly, the combination treatment results in a significant reduction in the viability of both the overall population of osteosarcoma cells and the cancer stem cell subpopulation. This effect is dependent on the ability of parthenolide to induce oxidative stress. Therefore, as a supplement to current multimodal therapy, parthenolide may sensitize osteosarcoma tumors to radiation and greatly reduce the prevalence of relapse and metastatic progression.

Apoptosis of peripheral blood lymphocytes and mutations in the gene of the T-cell receptor in survivors of chronic radiation exposure

This research has been conducted to study the activity of apoptosis of peripheral blood lymphocytes (PBLs) and the frequency of CD3-/CD4+ PBLs in people who have suffered chronic low-intensity radiation exposure. An increase in the frequency of apoptotic cells (TUNEL) is demonstrated in the group of exposed individuals relative to the control group. The frequency of mutations in the gene of the T-cell receptor in the exposed individuals is also elevated. Analyses of the mean values of apoptosis and CD3-CD4+ PBLs in different dose subgroups have found an increase in the proportion of cells with mutant T-cell receptors against the background of a decrease in the frequency of apoptotic cells in the range of low and medium radiation doses.

Proteomic and redox-proteomic analysis of berberine-induced cytotoxicity in breast cancer cells

Berberine is a natural product isolated from herbal plants such as Rhizoma coptidis which has been shown to have anti-neoplastic properties. However, the effects of berberine on the behavior of breast cancers are largely unknown. To determine if berberine might be useful in the treatment of breast cancer and its cytotoxic mechanism, we analyzed the impact of berberine treatment on differential protein expression and redox regulation in human breast cancer cell line MCF-7 using lysine- and cysteine-labeling two-dimensional difference gel electrophoresis (2D-DIGE) combined with mass spectrometry (MS). This study demonstrated that 96 and 22 protein features were significantly changed in protein expression and thiol reactivity, respectively and revealed that berberine-induced cytotoxicity in breast cancer cells involves dysregulation of protein folding, proteolysis, redox regulation, protein trafficking, cell signaling, electron transport, metabolism and centrosomal structure. Our work shows that this combined proteomic strategy provides a rapid method to study the molecular mechanisms of berberine-induced cytotoxicity in breast cancer cells. The identified targets may be useful for further evaluation as potential targets in breast cancer therapy.

Regulation of cell survival and death signals induced by oxidative stress

Oxidative stress stimulates two opposite signaling pathways leading to cell death and cell survival. Preferential selection of survival signals leads to the protection of cells against damage induced by reactive oxygen species, whereas preferential acceleration of death signals can be used to advantage in tumor therapy with oxidizing agents such as ionizing radiation and anticancer drugs. In vitro and in vivo experiments using cultured mammalian cells and experimental animals showed that ERK was included in survival signals and SAPK and p38 MAPK in death signals in oxidative stress. The activation of SAPK/JNK and subsequent expression of death receptor Fas on the cell surface caused the induction of cell death. The results mean that the acceleration of the activation of SAPK/JNK might lead to the enhancement of cell death by oxidizing agents like ionizing radiation and anticancer drugs. In fact, when cultured mammalian cells were exposed to ionizing radiation with 2-nitroimidazole derivatives having electrophilicity, the lethal effect of ionizing radiation was found to be enhanced together with the activation of SAPK/JNK and the enhancement of Fas expression. The activation of both survival and death signals was suppressed by the antioxidants N-acetylcystein and Trolox, suggesting that both signaling pathways are redox-regulated.

Caspase-independent apoptosis induction of quorum-sensing autoinducer analogs against chronic myeloid leukemia K562

Quorum sensing is defined as the ability of microorganisms to sense their population density via the release of signaling molecules called autoinducers (AIs). Various types of AI analogs were prepared and their antitumor properties against chronic myeloid leukemia (CML) K562 cells were investigated. Two AI analogs induced progressive apoptosis with JNK activation and p21 induction. In addition, this induction of apoptosis is not related to bcr-abl kinase, which sustains CML proliferation. However, the progression of apoptosis was not inhibited by a caspase family inhibitor. These results suggested that AI analogs could induce caspase-independent apoptosis in CML K562.

Oxidative stress as a significant factor for development of an adaptive response in irradiated and nonirradiated human lymphocytes after inducing the bystander effect by low-dose X-radiation

X-radiation (10cGy) was shown to induce in human lymphocytes transposition of homologous chromosomes loci from the membrane towards the centre of the nucleus and activation of the chromosomal nucleolus-forming regions (NFRs). These effects are transmitted by means of extracellular DNA (ecDNA) fragments to nonirradiated cells (the so-called bystander effect, BE). We demonstrated that in the development of the BE an important role is played by oxidative stress (which is brought about by low radiation doses and ecDNA fragments of the culture medium of the irradiated cells), by an enzyme of apoptosis called caspase-3, and by DNA-binding receptors of the bystander cells, presumably TLR9. Proposed herein is a scheme of the development of an adaptive response and the BE on exposure to radiation. Ionizing radiation induces apoptosis of the radiosensitive fraction of cells due to the development of the "primary" oxidative stress (OS). DNA fragments of apoptotic cells are released into the intercellular space and interact with the DNA-binding receptors of the bystander cells. This interaction activates in lymphocytes signalling pathways associated with synthesis of the reactive oxygen species and nitrogen species, i.e., induces secondary oxidative stress accompanied by apoptosis of part of the cells, etc. Hence, single exposure to radiation may be followed by relatively long-lasting in the cellular population oxidative stress contributing to the development of an adaptive response. We thus believe that ecDNA of irradiated apoptotic lymphocytes is a significant factor of stress-signalling.

Proteomics and pathway analysis identifies JNK signaling as critical for high linear energy transfer radiation-induced apoptosis in non-small lung cancer cells

During the past decade, we have witnessed an explosive increase in generation of large proteomics data sets, not least in cancer research. There is a growing need to extract and correctly interpret information from such data sets to generate biologically relevant hypotheses. A pathway search engine (PSE) has recently been developed as a novel tool intended to meet these requirements. Ionizing radiation (IR) is an anticancer treatment modality that triggers multiple signal transduction networks. In this work, we show that high linear energy transfer (LET) IR induces apoptosis in a non-small cell lung cancer cell line, U-1810, whereas low LET IR does not. PSE was applied to study changes in pathway status between high and low LET IR to find pathway candidates of importance for high LET-induced apoptosis. Such pathways are potential clinical targets, and they were further validated in vitro. We used an unsupervised shotgun proteomics approach where high resolution mass spectrometry coupled to nanoflow liquid chromatography determined the identity and relative abundance of expressed proteins. Based on the proteomics data, PSE suggested the JNK pathway (p = 6.10(-6)) as a key event in response to high LET IR. In addition, the Fas pathway was found to be activated (p = 3.10(-5)) and the p38 pathway was found to be deactivated (p = 0.001) compared with untreated cells. Antibody-based analyses confirmed that high LET IR caused an increase in phosphorylation of JNK. Moreover pharmacological inhibition of JNK blocked high LET-induced apoptotic signaling. In contrast, neither an activation of p38 nor a role for p38 in high LET IR-induced apoptotic signaling was found. We conclude that, in contrast to conventional low LET IR, high LET IR can trigger activation of the JNK pathway, which in turn is critical for induction of apoptosis in these cells. Thus PSE predictions were largely confirmed, and PSE was proven to be a useful hypothesis-generating tool.

EMMPRIN expression as a prognostic factor in radiotherapy of cervical cancer

PURPOSE

Overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN), a member of the immunoglobulin family and a glycoprotein enriched on the surface of many types of tumor cells, has been reported to be linked to invasion, metastasis, growth, and survival of malignant cells. Cervical cancer, the second most prevalent cancer in women worldwide and the fifth leading cause of cancer deaths, responds to radiotherapy variably, with 30% of cases recurring after therapy. The purpose of this study was to determine whether expression of EMMPRIN affects the response of cervical cancer to radiation therapy, and whether this membrane protein can be used as a prognostic marker for cervical cancer.

EXPERIMENTAL DESIGN

The retrospective cohort study included 82 patients with invasive cervical cancer referred to the Department of Gynecologic Oncology at The Cancer Hospital of Fudan University (Shanghai) between 1991 and 2000. These patients were treated with brachytherapy at a dose of 15 Gy at point A before radical hysterectomy. Expression of EMMPRIN in cervical tumor specimens was examined by immunohistochemistry staining before and after brachytherapy and scored for both staining intensity and percentage of tumor cells stained. EMMPRIN immunoreactivity and clinicopathologic data were analyzed with respect to survival end points using univariate and multivariate approaches.

RESULTS

The frequency of EMMPRIN overexpression was 52.4% in primary cervical cancer. After brachytherapy, EMMPRIN overexpression was significantly reduced (13.4%) compared with corresponding tumor before brachytherapy (P = 0.032). EMMPRIN expression was associated with pelvic lymph node metastasis (P = 0.026) and reduction in primary tumor volume following brachytherapy (P = 0.008). Although EMMPRIN expression before or after brachytherapy did not correlate with tumor-specific survival, but increased expression of EMMPRIN following brachytherapy tended to predict poor outcomes by univariate survival analysis (P = 0.0008). In addition, lymph vascular space invasion, deep stromal invasion, and lymph node metastasis were significantly associated with poor prognosis. In multivariate analysis, the independent prognostic factors for tumor-specific survival included the decreased expression of EMMPRIN after brachytherapy (P = 0.002; hazard ratio, 0.339; 95% confidence interval, 0.172-0.672) as well as lymph node metastasis (P = 0.044; hazard ratio, 2.053; 95% confidence interval, 1.020-4.133).

CONCLUSION

Expression of EMMPRIN was associated with a decrease in the reduction of cervical tumor following brachytherapy, and increased EMMPRIN expression after brachytherapy seemed to be an important predictor of poor survival in this patient cohort. Our study suggests that expression of EMMPRIN confers resistance to radiotherapy. Therefore, EMMPRIN expression in cervical cancer may be regarded both as a prognostic factor and a therapeutic target.

Enhanced CD95-mediated apoptosis contributes to radiation hypersensitivity of NBS lymphoblasts

The molecular causes for enhanced radiosensitivity of Nijmegen Breakage Syndrome cells are unclear, especially as repair of DNA damage is hardly impeded in these cells. We clearly demonstrate that radiation hypersensitivity is accompanied by enhanced gamma-radiation-induced apoptosis in NBS1 deficient lymphoblastoid cell lines. Differences in the apoptotic behavior of NBS1 (-/-) and NBS1 (+/-) cells are not due to an altered p53 stabilization or phosphorylation in NBS1 (-/-) cells. gamma-radiation-induced caspase-8 activity is increased and visualization of CD95 clustering by laser scanning microscopy shows a significant higher activation of the death receptor in NBS1 (-/-) cells. Further investigation of the molecular mechanisms reveals a role for reactive oxygen species-triggered activation of CD95. These results demonstrate that NBS1 suppresses the CD95 death receptor-dependent apoptotic pathway after gamma-irradiation and evidence is given that this is achieved by regulation of the PI3-K/AKT survival pathway.

Enhancement of cell death by TNF alpha-related apoptosis-inducing ligand (TRAIL) in human lung carcinoma A549 cells exposed to x rays under hypoxia

Our previous study showed that ionizing radiation induced the expression of death receptor DR5 on the cell surface in tumor cell lines and that the death receptor of the TNF alpha-related apoptosis-inducing ligand TRAIL enhanced the apoptotic pathway (Hamasu et al., (2005) Journal of Radiation Research, 46:103-110). The present experiments were performed to examine whether treatment with TRAIL enhanced the cell killing in tumor cells exposed to ionizing radiation under hypoxia, since the presence of radioresistant cells in hypoxic regions of solid tumors is a serious problem in radiation therapy for tumors. When human lung carcinoma A549 cells were irradiated under normoxia and hypoxia, respectively, radiation-induced enhancement of expression of DR5 was observed under both conditions. Incubation in the presence of TRAIL enhanced the caspase-dependent and chymotrypsin-like-protease-dependent apoptotic cell death in A549 cells exposed to X rays. Furthermore, it was shown that treatment with TRAIL enhanced apoptotic cell death and loss of clonogenic ability in A549 cells exposed to X rays not only under normoxia but also under hypoxia, suggesting that combination treatment with TRAIL and X irradiation is effective for hypoxic tumor cells.

Cadmium-induced apoptosis of hepatocytes is not associated with death receptor-related caspase-dependent pathways in the rat

Cadmium (Cd) is a heavy metal of considerable environmental and occupational concern. The liver is the major target organ of Cd toxicity that follows from repeated exposure to Cd. The aim of this study was to investigate the mechanism of cell death of Cd-induced hepatotoxicity in a rat model. Eighteen adult male Sprague-Dawley (SD) rats were injected daily with a dose of Cd acetate (30μM/kg body weight, subcutaneously). After 1, 2 and 7 days rats were euthanized and blood and liver tissues were sampled for analysis. Biochemical analyses of the level of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were undertaken. Histopathological and Western blot analyses for liver cellular damage and cell death were also performed. The results for the Cd-treated group of animals were compared to those from 12 control rats. The serum AST/ALT levels increased significantly 24h after CD exposure. From the Western blot analyses, activation of Bid, independent of caspase-8 was seen and Bax induced the release of cytochrome c into the cytosol from mitochondria in a dose-dependent manner. The level of Bcl-2 was decreased. Eventually, caspase-9 and caspase-3 were activated, and poly(ADP-ribose) polymerase (PARP) was cleaved in a dose-dependent manner. A histopathological analysis and DNA fragmentation test showed apoptotic cell death of the hepatocytes increased over time. These results suggest that Cd-induced liver cell apoptosis in the rat, over a period of 7 days, may not be related to the death-receptor pathway. Moreover, apoptosis is dose-dependent and associated with the decrement of Bcl-2.

Neuronal conduction of excitation without action potentials based on ceramide production

Background

Action potentials are the classic mechanism by which neurons convey a state of excitation throughout their length, leading, after synaptic transmission, to the activation of other neurons and consequently to network functioning. Using an in vitro integrated model, we found previously that peripheral networks in the autonomic nervous system can organise an unconventional regulatory reflex of the digestive tract motility without action potentials.

Methodology/Principal Findings

In this report, we used combined neuropharmacological and biochemical approaches to elucidate some steps of the mechanism that conveys excitation along the nerves fibres without action potentials. This mechanism requires the production of ceramide in membrane lipid rafts, which triggers in the cytoplasm an increase in intracellular calcium concentration, followed by activation of a neuronal nitric oxide synthase leading to local production of nitric oxide, and then to guanosine cyclic monophosphate. This sequence of second messengers is activated in cascade from rafts to rafts to ensure conduction of the excitation along the nerve fibres.

Conclusions/Significance

Our results indicate that second messengers are involved in neuronal conduction of excitation without action potentials. This mechanism represents the first evidence—to our knowledge—that excitation is carried along nerves independently of electrical signals. This unexpected ceramide-based conduction of excitation without action potentials along the autonomic nerve fibres opens up new prospects in our understanding of neuronal functioning.

Dual targeting of IGF-1R and PDGFR inhibits proliferation in high-grade gliomas cells and induces radiosensitivity in JNK-1 expressing cells

Increased expression and activation of receptor tyrosine kinases frequently occur in human brain tumors, mediating a variety of growth-promoting pathways and leading to radioresistance; however, little is known about their motogenic potency relative to one another. In this study, we found co-expression of Insulin like growth factor-1 receptor (IGF-1R) and platelet derived growth factor receptor (PDGFR) in two high-grade gliomas (HGG) cell lines 18 and 38. Dual targeting of IGF-1R and PDGFR increased cell death in both 18 and 38 cell lines in comparison to inhibition of either receptor alone. In addition, co-inhibition of IGF-1R and PDGFR increased radiosensitivity in 18 cells but failed to intensify the effect of radiation in 38 cells. In HGG cells, radiation-induced cell death has been connected to the activation of c-Jun-NH2-terminal kinase-1 (JNK1). We found that JNK1 was weakly expressed in 38 cells while it had an elevated expression in 18 cells. Exposure to ionizing radiation induced JNK1 activation only in 18 cells without affecting the protein activity in 38 cells. These results suggest that in 18 cell line radiation-activated JNK1 may provide an anti-proliferative signaling, parallel to receptors co-targeting. To test this hypothesis, HGG cells were treated with dominant negative JNK1 (dnJNK1) and the response to radiation was assayed in presence or absence of receptors co-inhibition. Indeed dnJNK protected 18 cells against gamma-irradiation-induced cell death. dnJNK treatment did not influence radiation response of the 38 cell line, which expressed low levels of JNK1. In conclusion we found that IGF-1R and PDGFR co-inhibition caused an increased cell death in two HGG cell line and induced the radiosensitization of the JNK1 expressing cell line.

Effects of ceramide inhibition on radiation-induced apoptosis in human leukemia MOLT-4 cells

In the present study, using inhibitors of ceramide synthase (fumonisin B1), ketosphinganine synthetase (L-cycloserine), acid sphingomyelinase (D609 and desipramine) and neutral sphingomyelinase (GW4869), the role of ceramide in X-ray-induced apoptosis was investigated in MOLT-4 cells. The diacylglycerol kinase (DGK) assay showed that the intracellular concentration of ceramide increased time-dependently after X irradiation of cells, and this radiation-induced accumulation of ceramide did not occur prior to the appearance of apoptotic cells. Treatment with D609 significantly inhibited radiation-induced apoptosis, but did not inhibit the increase of intracellular ceramide. Treatment with desipramine or GW4869 prevented neither radiation-induced apoptosis nor the induced increase of ceramide. On the other hand, fumonisin B1 and L-cycloserine had no effect on the radiation-induced induction of apoptosis, in spite of significant inhibition of the radiation-induced ceramide. From these results, it was suggested that the increase of the intracellular concentration of ceramide was not essential for radiation-induced apoptosis in MOLT-4 cells.

Selective pharmacologic inhibition of c-Jun NH2-terminal kinase radiosensitizes thyroid anaplastic cancer cell lines via induction of terminal growth arrest

CONTEXT

The high radioresistance of anaplastic thyroid cancer (ATC) and cultured ATC cells stipulates for the means of increasing their radiosensitivity. It has been shown that c-Jun NH(2)-terminal kinase (JNK) activation is one of the manifestations of radiation response in ATC cells.

OBJECTIVE

Assessment of the effect of selective JNK inhibition on ATC cell radiosensitivity and clarification of the associated mechanisms.

RESULTS

The JNK inhibitor markedly suppressed ATC cell growth in a reversible cytostatic manner. The combination treatment with JNK inhibitor plus ionizing radiation induced a significant decrease in clonogenic survival of irradiated cells as compared with either singular treatment. The effect was not due to apoptosis of exposed cells but to a profound senescence-like terminal growth arrest occurring irrespectively of cells' p53 mutational status. Postradiational DNA damage repair was also significantly compromised in the presence of SP600125.

CONCLUSIONS

JNK signaling is an essential component of ATC cell proliferation and survival after radiation therapy. Hence, pharmacological interference with JNK pathway in combination with radiotherapy may be a promising treatment of ATC.

Increased radiation-induced apoptosis of Saos2 cells via inhibition of NFκB: A role for c-Jun N-terminal kinase

To elucidate the possible effect of NFkappaB on radioresistance, we used the osteosarcoma cell line Saos2, stably expressing the NFkappaB constitutive inhibitor, mIkappaB (Saos2-mIkappaB) or stably transfected with the empty vector (Saos2-EV). Ionizing radiation induced "intrinsic" apoptosis in Saos2-mIkappaB cells but not in Saos2-EV control cells, with intact NFkappaB activity. We find as expected, that this NFkappaB activity was enhanced following irradiation in the Saos2-EV control cells. On the other hand, inhibition of NFkappaB signaling in Saos2-mIkappaB cells led to the upregulation of the pro-apoptotic systems, such as Bax protein and c-Jun N-terminal Kinase (JNK)/c-Jun/AP1 signaling. Inhibition of NFkappaB resulted in decreased expression of the DNA damage protein GADD45beta, a known inhibitor of JNK. Subsequently, JNK activation of c-Jun/AP-1 proteins increased radiation-induced apoptosis in these mutants. Radiation-induced apoptosis in Saos2-mIkappaB cells was inhibited by the JNK specific inhibitor SP600125 as well as by Bcl-2 over-expression. Furthermore, release of cytochrome-c from mitochondria was increased and caspase-9 and -3 were activated following irradiation in Saos2-mIkappaB cells. Antisense inhibition of GADD45beta in Saos2-EV cells significantly enhanced apoptosis following irradiation. Our results demonstrate that radioresistance of Saos2 osteosarcoma cells is due to NFkappaB-mediated inhibition of JNK. Our study brings new insight into the mechanisms underlying radiation-induced apoptosis of osteosarcoma, and may lead to development of new therapeutic strategies against osteosarcoma.

JNK/SAPK and p38 SAPK-2 mediate mechanical stretch-induced apoptosis via caspase-3 and -9 in NRK-52E renal epithelial cells

BACKGROUND/AIMS

In renal epithelial cells, mechanical forces produced from urinary obstruction serve as potential mediators of apoptosis by activating specific intracellular signaling pathways. In this study, we sought to further define the role of JNK and p38 SAPK-2 pathway and caspase activation in stretch-induced apoptosis.

METHODS

Immortalized cell lines derived from the various components of the nephron were subjected to cyclical stretch and their differential apoptotic response was assessed. Pharmacologic inhibitors and Western blot analysis were used to assess the involvement of the MAPK pathways. Caspases' activity was assessed with ELISA and by Western blot analysis.

RESULTS

Stretch-induced apoptosis was dependent upon the cell phenotype and the degree of stretch. In NRK-52E cells, it was mediated through both JNK and p38 SAPK-2 pathways, and inhibition of either pathway reduced the degree of stretch-induced apoptosis. Stretched cells showed increased activity of caspase-3 and -9 but not -2 or -8. Stretch-induced apoptosis was modulated by inhibition of caspase-3 and to a lesser extent by caspase-9.

CONCLUSION

These findings suggest that stretch induces apoptosis in renal epithelial cells through the specific activation of JNK/SAPK and p38 SAPK-2 pathways and is dependent on the activation of caspase-3 and -9.

Hypoxia-induced BAX overexpression and radiation killing of hypoxic glioblastoma cells

One major challenge in treating glioblastoma multiforme (GBM) has been the presence of radiation-resistant hypoxic cells. The pro-apoptosis protein BAX has been reported to be a possible radiation sensitizer of cancer cells; however, to our knowledge, no studies have reported on the effects of BAX on radiation sensitivity under hypoxic conditions. Therefore, in this study, we specifically overexpressed murine Bax in hypoxic cells in an attempt to enhance radiation-induced cell killing. We have previously stably transfected U-251 MG and U-87 MG human GBM cells with constructs containing murine Bax under the regulation of nine copies of hypoxia-responsive elements (HREs). During hypoxia, the transcriptional complex hypoxia-inducible factor 1 (HIF1) forms and binds to HRE; this binding facilitates the transcription of downstream genes. In the experiments reported here, two protocols were used. In the first protocol, parent and clone cells were exposed to graded doses of X rays under hypoxic conditions, left hypoxic for 0, 4, 16 or 24 h, and then assayed for clonogenic cell survival. In the second protocol, cells were incubated under hypoxic conditions for 20 h, irradiated with graded doses under hypoxia, then left in hypoxic conditions for 4 h before being assayed for clonogenic cell survival. Western blots showed that we had successfully increased Bax expression in both U-251 MG and U-87 MG Bax clone cells after 16 h of hypoxic incubation, yet dose-response curves showed no difference in radiation-induced cell killing between control non-Bax-expressing pNeo clone cells and the U-251 MG Bax clone cells using either protocol. In U-87 MG cells, the first protocol showed no difference in radiation response between control pNeo clone cells and the Bax clone, similar to the results obtained in U-251 cells. However, the second protocol revealed that Bax overexpression did render these cells more sensitive to radiation under hypoxic conditions. Therefore, we conclude that whether Bax is a radiation enhancer under hypoxia not only is cell line-dependent but also depends on when the Bax overexpression occurs.

Post-irradiation hypoxic incubation of X-irradiated MOLT-4 cells reduces apoptotic cell death by changing the intracellular redox state and modulating SAPK/JNK pathways

To elucidate radiobiological effects of hypoxia on X-ray-induced apoptosis, MOLT-4 cells were treated under four set of conditions: (1) both X irradiation and incubation under normoxia, (2) X irradiation under hypoxia and subsequent incubation under normoxia, (3) X irradiation under normoxia and subsequent incubation under hypoxia, and (4) both X irradiation and incubation under hypoxia, and the induction of apoptosis was examined by fluorescence microscopy. About 28-33% apoptosis was observed in cells treated under conditions 1 and 2, but this value was significantly reduced to around 18-20% in cells treated under conditions 3 and 4, suggesting that post-irradiation hypoxic incubation rather than hypoxic irradiation mainly caused the reduction of apoptosis. The activation and expression of apoptosis signal-related molecules SAPK/JNK, Fas and caspase-3 were also suppressed by hypoxic incubation. Effects of hypoxic incubation were canceled when cells were treated under conditions 3 and 4 with an oxygen-mimicking hypoxic cell radiosensitizer, whereas the addition of N-acetyl-L-cysteine again reduced the induction of apoptosis. From these results it was concluded that hypoxia reduced the induction of apoptosis by changing the intracellular redox state, followed by the regulation of apoptotic signals in X-irradiated MOLT-4 cells.

Enhanced induction of apoptosis by combined treatment of human carcinoma cells with X rays and death receptor agonists

The death receptors Fas and DR5 are known to be expressed not only in immune cells but also in various tumor cells. The aim of the present study was to determine whether X irradiation enhanced induction of apoptosis in Tp53 wild type and Tp53-mutated tumor cell lines treated with agonists against these death receptors. We showed that 5 Gy of X irradiation significantly up-regulated the expression of death receptors Fas and DR5 on the plasma membrane in gastric cancer cell lines MKN45 and MKN28, lung cancer cell line A549, and prostate cancer cell line DU145, and that subsequent treatments with agonistic molecules for these death receptors, Fas antibody CH11 and TRAIL, increased the formation of active fragment p20 of caspase 3 followed by the induction of apoptosis. This death-receptor-mediated apoptosis was independent of Tp53 status since MKN28 and DU145 were Tp53-mutated. The post-irradiation treatment of the cells with N-acetyl-L-cysteine (NAC) abolished the up-regulation of the expression of Fas and DR5 on the plasma membrane. NAC also attenuated the increase in the formation of p20 and the induction of apoptosis by agonistic molecules. These results suggested that the increase in the induction of apoptosis by combined treatment with X irradiation and CH11 or TRAIL occurred through a change of the intracellular redox state independent of Tp53 status in human carcinoma cell lines.

In vivo modulation of signaling factors involved in cell survival

In vivo expression of cell survival factors protein kinase C (PKC), nuclear factor kappaB (NFkappaB), and extracellular signal-regulated kinase (Erk), which may contribute to the development of radioresistance following radiotherapy, was looked for. Their modulation with natural compounds (curcumin, rutin or nicotinamide) was attempted in mice bearing a serially transplanted fibrosarcoma. Expression of protein kinase C was isoform specific. No translocation of any of the isozymes was noticed following gamma-irradiation as has been reported elsewhere. None of the isoforms could be significantly inhibited by the modulators. However, significant inhibition of radiation-induced ERK and NFkappaB was observed with both curcumin and nicotinamide. Therefore we conclude that use of inhibitors of MAP kinases or NFkappaB may be a more promising strategy to enhance tumour cell killing or to prevent the development of radioresistance during radiotherapy.

Enhancement of radiation-induced apoptosis by preirradiation with low-dose X-rays in human leukemia MOLT-4 cells

The effects of low-dose preirradiation on the process of radiation-induced cell death were investigated in human leukemic MOLT-4 cells. By 0.2 Gy of X-rays given 12 h prior to a challenge dose of 5 Gy, the process of apoptosis was accelerated. The acceleration was associated with a certain increase in caspase 3 activity, a disruption of the mitochondrial transmembrane potential, and an accumulation of p53 proteins. This finding is in contrast to the radiation adaptive responses in which a small dose of preirradiation would induce certain radiation resistance and decrease the cell death after irradiation with higher doses.