Mitochondrial dysfunction is an essential step for killing of non-small cell lung carcinomas resistant to conventional treatment

A Mini Review on Molecules Inducing Caspase-Independent Cell Death: A New Route to Cancer Therapy

Most anticancer treatments trigger tumor cell death through apoptosis, where initiation of proteolytic action of caspase protein is a basic need. But under certain circumstances, apoptosis is prevented by the apoptosis inhibitor proteins, survivin and Hsp70. Several drugs focusing on classical programmed death of the cell have been reported to have low anti-tumorogenic potency due to mutations in proteins involved in the caspase-dependent programmed cell death with intrinsic and extrinsic pathways. This review concentrates on the role of anti-cancer drug molecules targeting alternative pathways of cancer cell death for treatment, by providing a molecular basis for the new strategies of novel anti-cancer treatment. Under these conditions, active agents targeting alternative cell death pathways can be considered as potent chemotherapeutic drugs. Many natural compounds and other small molecules, such as inorganic and synthetic compounds, including several repurposing drugs, are reported to cause caspase-independent cell death in the system. However, few molecules indicated both caspase-dependent as well caspase-free cell death in specific cancer lines. Cancer cells have alternative methods of caspase-independent programmed cell death which are equally promising for being targeted by small molecules. These small molecules may be useful leads for rational therapeutic drug design, and can be of potential interest for future cancer-preventive strategies.

Maclurin exerts anti-cancer effects in human osteosarcoma cells via prooxidative activity and modulations of PARP, p38, and ERK signaling

Maclurin [(3,4-dihydroxyphenyl)-(2,4,6-trihydroxyphenyl) methanone] is a natural compound that can be extracted from white mulberry(Morus alba) and purple mangosteen(Garcinia mangostana). Maclurin is known for its dual-sided effect on reactive oxygen species (ROS). Osteosarcoma is a primary malignant tumor of the bone and is one of the most aggressive cancers. It is common especially in children and young adults and can progress into highly metastatic cancer. In this study, we investigated the anti-cancer effects of maclurin on U2OS human osteosarcoma cells. The results indicated that maclurin exerts prooxidative effects and induces apoptosis via capase-3-independent PARP regulation in U2OS human osteosarcoma cells. Maclurin also inhibits the migration of U2OS human osteosarcoma cells. Maclurin modulates two of the three major mitogen-activated protein kinases that are closely linked with cancer metastasis; that is, it activates p38 and inactivates Extracellular signal-regulated kinase. The apoptosis-inducing effects of maclurin on U2OS osteosarcoma cells were diminished by additional treatment with antioxidant N-acetyl cysteine (NAC), but the migration-inhibiting effect was not affected by NAC treatment. This further suggested the only apoptosis-inducing effect of maclurin may be strongly related to its prooxidative activity. Taken together, these results suggested that maclurin may be a strong candidate molecule as an anti-osteosarcoma agent.

Sulfur dioxide induces apoptosis via reactive oxygen species generation in rat cardiomyocytes

Epidemiological evidence suggests that the incidence and mortality of cardiovascular diseases are closely related to sulfur dioxide (SO₂). In the present study, H9C2 cells were incubated with 100 μM NaHSO₃ with or without pretreatment of an antioxidant, N-acetyl-L-cysteine (NAC). The changes of apoptosis rate, mitochondrial membrane potential (MMP), ATP content, caspase-3 activity, and reactive oxygen species (ROS) were detected. Rats were inhaled 7 mg/m³ SO₂ and/or intraperitoneal injected with 50 mg/kg (bw) of NAC for 30 days. RT-PCR and Western blot were used to detect the mRNA and protein levels of apoptosis-related genes. We found that the apoptosis of H9C2 cells was induced by NaHSO₃, which decreased the content of MMP and ATP, and induced the expression of caspase-3. NAC can inhibit the apoptosis induced by NaHSO₃ treatment. SO₂ and NaHSO₃ decreased the expression of Bcl-2 and the ratio of Bcl-2/Bax, increased the expression of Bax and P53 accumulation and phosphorylation, and activated caspase-9 and caspase-3. Whereas NAC can reduce the changes of apoptosis-related proteins in rat heart. Our results suggest that SO₂ induces ROS-mediated P53 and caspase-dependent mitochondrial signaling pathways in H9C2 cells and rat hearts. Antioxidant therapy can reduce the adverse reactions of SO₂ and lead to a decline in the cardiovascular disease induced by SO₂.

Gene expression profiling of breast cancer cell lines treated with proton and electron radiations

OBJECTIVE

Technological advances in radiation therapy are evolving with the use of hadrons, such as protons, indicated for tumors where conventional radiotherapy does not give significant advantages or for tumors located in sensitive regions, which need the maximum of dose-saving of the surrounding healthy tissues. The genomic response to conventional and non-conventional linear energy transfer exposure is a poor investigated topic and became an issue of radiobiological interest. The aim of this work was to analyze and compare molecular responses in term of gene expression profiles, induced by electron and proton irradiation in breast cancer cell lines.

METHODS

We studied the gene expression profiling differences by cDNA microarray activated in response to electron and proton irradiation with different linear energy transfer values, among three breast cell lines (the tumorigenic MCF7 and MDA-MB-231 and the non-tumorigenic MCF10A), exposed to the same sublethal dose of 9 Gy.

RESULTS

Gene expression profiling pathway analyses showed the activation of different signaling and molecular networks in a cell line and radiation type-dependent manner. MCF10A and MDA-MB-231 cell lines were found to induce factors and pathways involved in the immunological process control.

CONCLUSION

Here, we describe in a detailed way the gene expression profiling and pathways activated after electron and proton irradiation in breast cancer cells. Summarizing, although specific pathways are activated in a radiation type-dependent manner, each cell line activates overall similar molecular networks in response to both these two types of ionizing radiation. Advances in knowledge: In the era of personalized medicine and breast cancer target-directed intervention, we trust that this study could drive radiation therapy towards personalized treatments, evaluating possible combined treatments, based on the molecular characterization.

Fluoride induced tissue hypercalcemia, IL-17 mediated inflammation and apoptosis lead to cardiomyopathy: Ultrastructural and biochemical findings

An increased prevalence of cardiac complications has been observed in residents of fluorosis endemic areas chronically exposed to fluoride. Fluoride induces soft tissue injury due to oxidative stress, lipid peroxidation (LPO) and mitochondriopathy. It was hypothesized that chronic fluoride exposure induces apoptosis in cardiomyocytes due to inflammation, lysis of extra cellular matrix and altered calcium metabolism. This study was planned to evaluate the effects of chronic fluoride exposure and the mechanism of action in the cardiac muscle. Fifteen week old male Wistar rats were administered a human equivalent dose of fluoride (50 and 100 ppm ad-libitum, HED = 5 & 10 ppm in human) for 75-days. After 75-days of fluoride exposure, the animals were euthanized and fluoride, oxidative stress (SOD, GPX, Catalase activities) and LPO were measured. Histopathological and ultrastructural pathological examinations were conducted on the cardiac tissues using light, atomic force and electron microscopies. The cardiac tissues were also assessed for apoptosis (TUNEL/Caspase assays), and tissue calcium levels (Alizarin-assay and SEM-EDX). Tissue inflammation and expression of IL-17, MMP-9, Caspase-3 and Bcl-2 were evaluated. In the fluoride exposed groups, a significant (≤0.05) increase in levels of oxidative stress, LPO and apoptosis were observed. The IL-17, MMP-9 and Caspase-3 were significantly (≤0.05) higher in the cardiac muscle after chronic fluoride exposure. The fluoride seems to have induced inflammation in the cardiac tissues, as well as an increase in tissue calcium (≤0.05). There was significant damage to cardiac muscle fibres including, thinning, distortion and neo-vasculogenesis following chronic fluoride exposure. Mitochondriopathy, lysis of ground substance, oedema, and hyper-vacuolation was seen in fluoride treated groups. Remarkable levels of distortion and bending in Z band were observed under the AFM. Many of these observed changes mimic those occurring in cardiomegaly, cardiac hypertrophy and cardiomyopathies.

Fluoride induces apoptosis in H9c2 cardiomyocytes via the mitochondrial pathway

Numerous studies have shown that chronic excessive fluoride intake can adversely affect different organ systems. In particular, the cardiovascular system is susceptible to disruption by a high concentration of fluoride. The objectives of this study were to explore the mechanism of apoptosis by detecting the toxic effects of different concentrations of sodium fluoride (NaF) in H9c2 cells exposed for up to 96 h. NaF not only inhibited H9c2 cell proliferation but also induced apoptosis and morphological damage. With increasing NaF concentrations, early apoptosis of H9c2 cells was increased while the mitochondrial membrane potential was decreased. Compared with the control group, the mRNA levels of caspase-3, caspase-9, and cytochrome c all increased with increasing concentrations of NaF. In summary, these data suggest that apoptosis is involved in NaF-induced H9c2 cell toxicity and that activation of the mitochondrial pathway may occur.

Visfatin induces the apoptosis of endothelial progenitor cells via the induction of pro-inflammatory mediators through the NF-κB pathway

Endothelial progenitor cells (EPCs) are an independent factor predicting cardiovascular events. Visfatin plays an important role in the pathogenesis of various metabolic disorders. In this study, we examined the effects of visfatin on the apoptosis of EPCs and the mechanisms underlying these effects. Cultured EPCs pre-treated with various concentrations of visfatin, FK866 (visfatin inhibitor) and BAY11-7085 [referred to as BAY11; nuclear factor-κB (NF-κB) inhibitor] were used to investigate the association between visfatin and EPC apoptosis. Following treatment with visfatin for 48 h, the EPCs exhibited a dose-dependent increase in apoptosis and an upregulated expression of Bax, caspase-3 and NF-κB at both the mRNA and protein level, and a decreased protein expression of Bcl-2. Compared with the untreated control group, the increase in EPC apoptosis, as well as in Bax and caspase-3 expression was significant following treatment with 150 ng/ml visfatin, which also induced a dose-dependent and significant increase in the protein expression of interleukin-6 (IL-6) and intercellular adhesion molecule-1 (ICAM-1). All the visfatin-induced effects were suppressed by pre-treatment with FK866. Pre-incubation of the EPCs with BAY11 for 1 h followed by treatment with visfatin (150 ng/ml) for 48 h also abolished visfatin-induced apoptosis; it also abolished the promoting effects of visfatin on the expression of caspase-3, Bax, ICAM-1 and IL-6, and its suppressive effects on the protein expression of Bcl-2. On the whole, our data indicate that visfatin induces EPC apoptosis by increasing the expression of pro-inflammatory mediators partly through the regulation of NF-κB.

Apoptosis-inducing factor and calpain upregulation in glutamate-induced injury of rat spiral ganglion neurons

Spiral ganglion neuron (SGN) damage and apoptosis can lead to noise-induced hearing loss, age-associated hearing loss and, in certain cases, auditory neuropathy. The apoptosis-inducing factor (AIF)-associated pathway may be important in this process. The present study aimed to investigate the expression levels of AIF and calpain in damaged SGNs. Glutamate (Glu) perfusion and cell culture in different concentrations of Glu were performed to damage the SGNs of Sprague-Dawley (SD) rats, with saline water used as a control Different concentrations (5, 10, 20 and 40 mM) of Glu were injected into the cochlear tympanic canal of 18 SD rats, and 10, 20 and 40 mM Glu were added to SGN cultures. Auditory brainstem responses (ABR) were measured prior to and 2 days following the injection of Glu. Immunofluorescent staining was used to detect the SGN damage and the expression levels of AIF and calpain in vivo and in in vitro. Transmission electron microscopy (TEM) was used to measure cell apoptosis and reverse transcription-quantitative polymerase chain reaction was used to analyse the gene expression levels of AIF and calpain in the damaged SGNs. The TEM identified mitochondrial vacuolisation, swelling of the SGN and hetero-chromatin formation. Injection of Glu reduced the number of SGNs and induced apoptosis. AIF was observed to translocate into the nuclei of the SGNs in the 20 and 40 mM Glu groups, and the expression levels of AIF and calpain were markedly upregulated in the modiolus of the Glu-damaged SGNs. The upregulation of AIF and calpain may be important in the process of SGN damage and apoptosis.

Comprehensive review on betulin as a potent anticancer agent

Numerous plant-derived substances, and their derivatives, are effective antitumour and chemopreventive agents. Yet, there are also a plethora of tumour types that do not respond, or become resistant, to these natural substances. This requires the discovery of new active compounds. Betulin (BE) is a pentacyclic triterpene and secondary metabolite of plants abundantly found in the outer bark of the birch tree Betulaceae sp. BE displays a broad spectrum of biological and pharmacological properties, among which the anticancer and chemopreventive activity attract most of the attention. In this vein, BE and its natural and synthetic derivatives act specifically on cancer cells with low cytotoxicity towards normal cells. Although the antineoplastic mechanism of action of BE is not well understood yet, several interesting aspects of BE's interactions are coming to light. This review will summarize the anticancer and chemopreventive potential of BE in vitro and in vivo by carefully dissecting and comparing the doses and tumour lines used in previous studies, as well as focusing on mechanisms underlying its activity at cellular and molecular level, and discuss future prospects.

Ameloblastic carcinoma of the mandible: Report of a case and review

Ameloblastic carcinoma is a rare malignant odontogenic neoplasm that can arise either as a de novo lesion or from pre-existing ameloblastoma. Histopathologically, the tumor retains an ameloblastomatous differentiation pattern but shows cytological features of malignancy. Owing to variable biologic behavior and paucity of long-term follow-up cases, there has been no clear consensus on treatment protocol. The present case of ameloblastic carcinoma arose in the mandible of a 24-year-old male. Surgical treatment involved resection of the mandible along with regional lymph nodes. The patient has been on follow up for the past one year without any recurrence or metastases. An update on ameloblastic carcinoma encompassing the histogenesis, immunohistochemical features and treatment aspects are included.

The Yin and Yang of redox regulation

Mammalian cells produce reactive oxygen and nitrogen species (ROS/RNOS) in response to an oxidative environment. Powerful antioxidant mechanisms have been developed in order to avoid oxidative stress by contributing to the maintenance of redox homeostasis. Traditionally, accumulation of ROS/RNOS is considered deleterious for cells as it can lead to loss of cellular function, aging, and cell death. Consequently, ROS/RNOS imbalance has been implicated in the etiology and/or progression of numerous pathologies such as cardiovascular diseases, inflammation, and cancer. An interesting concept that has emerged more recently is that not only have cells developed efficient systems to cope with ROS/RNOS accumulation but they have also learned to profit of them under certain circumstances. This notion is supported by data showing that ROS/RNOS can act as signaling molecules affecting the function and activity of a multiplicity of protein kinases and phosphatases controlling cellular homeostasis. This review does not provide an exhaustive overview of molecular mechanisms linked to ROS/RNOS generation and processing but includes relevant examples highlighting the dichotomic nature of these small molecules and the multitude of effects elicited by their accumulation. This aspect of ROS/RNOS ought to be taken into account particularly in novel therapeutic setups that aim to achieve high efficiency and minimal or no side effects.

Differential sensitivity to apoptosome apparatus activation in non-small cell lung carcinoma and the lung

The intrinsic apoptosis pathway represents an important mechanism of stress-induced death of cancer cells. To gain insight into the functional status of the apoptosome apparatus in non-small cell lung carcinoma (NSCLC), we studied its sensitivity to activation, the assembly of apoptosome complexes and stability of their precursors, and the importance of X-linked inhibitor of apoptosis (XIAP) in the regulation of apoptosome activity, using cell-free cytosols from NSCLC cell lines and NSCLC tumours and lungs from 62 surgically treated patients. Treatment of cytosol samples with cytochrome c (cyt-c) and dATP induced proteolytic processing of procaspase-9 to caspase-9, which was followed by procaspase-3 processing to caspase-3, and by generation of caspase-3-like activity in 5 of 7 studied NSCLC cell lines. Further analysis demonstrated formation of high-M_r Apaf-1 complexes associated with cleaved caspase-9 in the (cyt-c + dATP)-responsive COLO-699 and CALU-1 cells. By contrast, in A549 cells, Apaf-1 and procaspase-9 co-eluted in the high-M_r fractions, indicating formation of an apoptosome complex unable of procaspase-9 processing. Thermal pre-treatment of cell-free cytosols in the absence of exogenous cyt-c and dATP lead to formation of Apaf-1 aggregates, unable to recruit and activate procaspase-9 in the presence of cyt-c and dATP, and to generate caspase-3-like activity. Further studies showed that the treatment with cyt-c and dATP induced a substantially higher increase of caspase-3-like activity in cytosol samples from NSCLC tumours compared to matched lungs. Tumour histology, grade and stage had no significant impact on the endogenous and the (cyt-c + dATP)-induced caspase-3-like activity. Upon addition into the cytosol, the XIAP-neutralizing peptides AVPIAQK and ATPFQEG only moderately heightened the (cyt-c + dATP)-induced caspase-3-like activity in some NSCLC tumours. Taken together, the present study provides evidence that the apoptosome apparatus is functional in the majority of NSCLCs and that its sensitivity to the (cyt-c + dATP)-mediated activation is often enhanced in NSCLCs compared to lungs. They also indicate that XIAP does not frequently and effectively suppress the activity of apoptosome apparatus in NSCLCs.

Role of glutathione in cancer progression and chemoresistance

Glutathione (GSH) plays an important role in a multitude of cellular processes, including cell differentiation, proliferation, and apoptosis, and disturbances in GSH homeostasis are involved in the etiology and progression of many human diseases including cancer. While GSH deficiency, or a decrease in the GSH/glutathione disulphide (GSSG) ratio, leads to an increased susceptibility to oxidative stress implicated in the progression of cancer, elevated GSH levels increase the antioxidant capacity and the resistance to oxidative stress as observed in many cancer cells. The present review highlights the role of GSH and related cytoprotective effects in the susceptibility to carcinogenesis and in the sensitivity of tumors to the cytotoxic effects of anticancer agents.

Inhibition of Ephrin B3-mediated survival signaling contributes to increased cell death response of non-small cell lung carcinoma cells after combined treatment with ionizing radiation and PKC 412

Radiation therapy is frequently used to treat non-small cell lung cancers (NSCLCs). We have previously shown that a combination of ionizing radiation (IR) and the staurosporine analog PKC 412, but not Ro 31–8220, increases cell death in NSCLC cells. To identify genes involved in the enhancement of cell death, a total gene profiling in response to co-administration of (i) PKC 412 with IR, or (ii) Ro 31–8220 with IR was implemented. These combined treatments caused upregulation of 140 and 179 genes and downregulation of 253 and 425 genes, respectively. Certain genes were selected and verified by real-time quantitative PCR and, of these genes, robust suppression of Ephrin B3 expression was suggested as a possible cell death-inducing mechanism of combined treatment with IR and PKC 412. Indeed, silencing of Ephrin B3 using siRNA in NSCLC cells resulted in a major alteration of their morphology with an elongated phenotype, decreased proliferation and increased cell death signaling. Moreover, silencing of Ephrin B3 in combination with IR caused a decrease in IR-mediated G₂-arrest, induced cellular senescence, inhibited MAPK ERK and p38 phosphorylation, and caused an upregulation of p27^kip1 expression. Finally, silencing of Ephrin B3 in combination with IR sensitized U-1810 cells to IR-induced apoptosis. In conclusion, we identify and describe Ephrin B3 as a putative signaling molecule involved in the response of NSCLC cells to combined treatment with PKC 412 and ionizing radiation.

Cross-talk between NFkB and the PI3-kinase/AKT pathway can be targeted in primary effusion lymphoma (PEL) cell lines for efficient apoptosis

Background

A number of constitutively activated signaling pathways play critical roles in the survival and growth of primary effusion lymphoma cells (PELs) including NFkB and PI3/AKT kinase cascades. NFkBis constitutively activated in a number of malignancies, including multiple myeloma, Burkitt’s lymphoma and diffuse large cell B-cell lymphoma. However, its role in primary effusion lymphoma has not been fully explored.

Methodology/Principal Findings

We used pharmacological inhibition and gene silencing to define the role of NFkB in growth and survival of PEL cells. Inhibition of NFkB activity by Bay11-7085 resulted in decreased expression of p65 in the nuclear compartment as detected by EMSA assays. In addition, Bay11-7085 treatment caused de-phosphorylation of AKT and its downstream targets suggesting a cross-talk between NFkB and the PI3-kinase/AKT pathway. Importantly, treatment of PEL cells with Bay11-7085 led to inhibition of cell viability and induced apoptosis in a dose dependent manner. Similar apoptotic effects were found when p65 was knocked down using specific small interference RNA. Finally, co-treatment of PEL cells with suboptimal doses of Bay11-7085 and LY294002 led to synergistic apoptotic responses in PEL cells.

Conclusion/Significance

These data support a strong biological-link between NFkB and the PI3-kinase/AKT pathway in the modulation of anti-apoptotic effects in PEL cells. Synergistic targeting of these pathways using NFKB- and PI3-kinase/AKT- inhibitors may have a therapeutic potential for the treatment of PEL and possibly other malignancies with constitutive activation of these pathways.

Detecting the effect of targeted anti-cancer medicines on single cancer cells using a poly-silicon wire ion sensor integrated with a confined sensitive window

A mold-cast polydimethylsiloxane (PDMS) confined window was integrated with a poly-silicon wire (PSW) ion sensor. The PSW sensor surface inside the confined window was coated with a 3-aminopropyltriethoxysilane (γ-APTES) sensitive layer which allowed a single living cell to be cultivated. The change in the microenvironment due to the extracellular acidification of the single cell could then be determined by measuring the current flowing through the PSW channel. Based on this, the PSW sensor integrated with a confined sensitive window was used to detect the apoptosis as well as the effect of anti-cancer medicines on the single living non-small-lung-cancer (NSLC) cells including lung adenocarcinoma cancer cells A549 and H1299, and lung squamous-cell carcinoma CH27 cultivated inside the confined window. Single human normal cells including lung fibroblast cells WI38, lung fibroblast cells MRC5, and bronchial epithelium cell Beas-2B were tested for comparison. Two targeted anti-NSCLC cancer medicines, Iressa and Staurosporine, were used in the present study. It was found that the PSW sensor can be used to accurately detect the apoptosis of single cancer cells after the anti-cancer medicines were added. It was also found that Staurosporine is more effective than Iressa in activating the apoptosis of cancer cells.

Caspase signalling controls microglia activation and neurotoxicity

Activation of microglia and inflammation-mediated neurotoxicity are suggested to play a decisive role in the pathogenesis of several neurodegenerative disorders. Activated microglia release pro-inflammatory factors that may be neurotoxic. Here we show that the orderly activation of caspase-8 and caspase-3/7, known executioners of apoptotic cell death, regulate microglia activation through a protein kinase C (PKC)-δ-dependent pathway. We find that stimulation of microglia with various inflammogens activates caspase-8 and caspase-3/7 in microglia without triggering cell death in vitro and in vivo. Knockdown or chemical inhibition of each of these caspases hindered microglia activation and consequently reduced neurotoxicity. We observe that these caspases are activated in microglia in the ventral mesencephalon of Parkinson's disease (PD) and the frontal cortex of individuals with Alzheimer's disease (AD). Taken together, we show that caspase-8 and caspase-3/7 are involved in regulating microglia activation. We conclude that inhibition of these caspases could be neuroprotective by targeting the microglia rather than the neurons themselves.

Increase of reduced nicotinamide adenine dinucleotide fluorescence lifetime precedes mitochondrial dysfunction in staurosporine-induced apoptosis of HeLa cells

In vivo noninvasive detection of apoptosis represents a new tool that may yield a more definite diagnosis, a more accurate prognosis, and help improve therapies for human diseases. The intrinsic fluorescence of reduced nicotinamide adenine dinucleotide (NADH) may be a potential optical biomarker for the apoptosis detection because NADH is involved in the respiration for the mitochondrial membrane potential (ΔΨ) formation and adenosine-5'-triphosphate (ATP) synthesis, and the depletion of ΔΨ and ATP level is the hallmark of apoptosis. We have previously observed the NADH fluorescence lifetime change is associated with staurosporine (STS)-induced mitochondria-mediated apoptosis. However, its relationship with mitochondrial functions such as ΔΨ, ATP, and oxygen consumption rate is not clear. In this study, we investigated this relationship. Our results indicate that the NADH fluorescence lifetime increased when ΔΨ and ATP levels were equal to or higher than their values of controls and decreased before the depletion of ΔΨ and ATP, and the oxygen consumption rate did not change. These findings suggest that the increased NADH fluorescence lifetime in STS-induced cell death occurred before the depletion of ΔΨ and ATP and activation of caspase 3, and was not simply caused by cellular metabolic change. Furthermore, the NADH fluorescence lifetime change is associated with the pace of apoptosis.

Capsaicin may induce breast cancer cell death through apoptosis-inducing factor involving mitochondrial dysfunction

The majority of breast cancer patients are resistant to chemotherapy or radiotherapy due to the down-regulation or lack of caspase-3 expression. Capsaicin was found to inhibit cancer cell growth in caspase-3-deficient human breast cancer cells. This study aimed to investigate the growth-inhibitive effect of capsaicin and its mechanisms in human breast cancer cell lines, MCF-7 and BT-20. The results showed that cell viability decreased in a dose-dependent manner in both the caspase-3-deficient and non-deficient cells through inducing cell apoptosis and arresting the cell cycle in the S phase. Capsaicin significantly decreased mitochondria membrane potential, induced the cleavage of PARP-1, and decreased procaspase-7 expression in both cells. Apoptosis-inducing factor (AIF) was distinctly released from mitochondria and translocated into the cytoplasm and nucleus in MCF-7 cells (52.9%), but not in BT-20 cells (2%) after treatment with 200 μM of capsaicin for 24 hours. Capsaicin inhibited breast cancer cell growth through inducing cell apoptosis and cell cycle arrest in the S phase. This apoptotic effect could be induced through the mitochondrial pathway, and PARP-1 subsequently cleaved by activation of caspase-7. The application of capsaicin in clinical therapy could be useful for breast cancer patients.

Apoptosis-inducing factor mediates dopaminergic cell death in response to LPS-induced inflammatory stimulus: evidence in Parkinson's disease patients

We show that intranigral lipopolysaccharide (LPS) injection, which provokes specific degeneration of DA neurons, induced caspase-3 activation in the rat ventral mesencephalon, which was mostly associated with glial cells. In contrast, nigral DA neurons exhibited AIF nuclear translocation in response to LPS. A significant decrease of the Bcl-2/Bax ratio in nigral tissue after LPS injection was observed. We next developed an in vitro co-culture system with the microglial BV2 and the DA neuronal MN9D murine cell lines. The silencing of caspase-3 or AIF by small interfering RNAs exclusively in the DA MN9D cells demonstrated the key role of AIF in the LPS-induced death of DA cells. In vivo chemical inhibition of caspases and poly(ADP-ribose)polymerase-1, an upstream regulator of AIF release and calpain, proved the central role of the AIF-dependent pathway in LPS-induced nigral DA cell death. We also observed nuclear translocation of AIF in the ventral mesencephalon of Parkinson's disease subjects.

Critical role for hyperpolarization-activated cyclic nucleotide-gated channel 2 in the AIF-mediated apoptosis

This study establishes HCN2 channels as physiological relevant ‘calcium gates' that mediate apoptosis-inducing factor-dependent cell death in cancer and primary neuronal cells.

Cellular calcium uptake is a controlled physiological process mediated by multiple ion channels. The exposure of cells to either one of the protein kinase C (PKC) inhibitors, staurosporine (STS) or PKC412, can trigger Ca²⁺ influx leading to cell death. The precise molecular mechanisms regulating these events remain elusive. In this study, we report that the PKC inhibitors induce a prolonged Ca²⁺ import through hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) in lung carcinoma cells and in primary culture of cortical neurons, sufficient to trigger apoptosis-inducing factor (AIF)-mediated apoptosis. Downregulation of HCN2 prevented the drug-induced Ca²⁺ increase and subsequent apoptosis. Importantly, the PKC inhibitors did not cause Ca²⁺ entry into HEK293 cells, which do not express the HCN channels. However, introduction of HCN2 sensitized them to STS/PKC412-induced apoptosis. Mutagenesis of putative PKC phosphorylation sites within the C-terminal domain of HCN2 revealed that dephosphorylation of Thr⁵⁴⁹ was critical for the prolonged Ca²⁺ entry required for AIF-mediated apoptosis. Our findings demonstrate a novel role for the HCN2 channel by providing evidence that it can act as an upstream regulator of cell death triggered by PKC inhibitors.

Thioredoxin reductase 1 knockdown enhances selenazolidine cytotoxicity in human lung cancer cells via mitochondrial dysfunction

Thioredoxin reductase (TR1) is a selenoprotein that is involved in cellular redox status control and deoxyribonucleotide biosynthesis. Many cancers, including lung, overexpress TR1, making it a potential cancer therapy target. Previous work has shown that TR1 knockdown enhances the sensitivity of cancer cells to anticancer treatments, as well as certain selenocompounds. However, it is unknown if TR1 knockdown produces similar effect on the sensitivity of human lung cancer cells. To further elucidate the role of TR1 in the mechanism of selenocompounds in lung cancer, a lentiviral microRNA delivery system to knockdown TR1 expression in A549 human lung adenocarcinoma cells was utilized. Cell viability was assessed after 48 hr treatment with the selenocysteine prodrug selenazolidines 2-butylselenazolidine-4(R)-carboxylic acid (BSCA) and 2-cyclohexylselenazolidine-4-(R)-carboxylic acid (ChSCA), selenocystine (SECY), methylseleninic acid (MSA), 1,4-phenylenebis(methylene)selenocyanate (p-XSC), and selenomethionine (SEM). TR1 knockdown increased the cytotoxicity of BSCA, ChSCA, and SECY but did not sensitize cells to MSA, SEM, or p-XSC. GSH and TR1 depletion together decreased cell viability, while no change was observed with GSH depletion alone. Reactive oxygen species generation was induced only in TR1 knockdown cells treated with the selenazolidines or SECY. These three compounds also decreased total intracellular glutathione levels and oxidized thioredoxin, but in a TR1 independent manner. TR1 knockdown increased selenazolidine and SECY-induced mitochondrial membrane depolarization, as well as DNA strand breaks and AIF translocation from the mitochondria. These results indicate the ability of TR1 to modulate the cytotoxic effects of BSCA, ChSCA and SECY in human lung cancer cells through mitochondrial dysfunction.

Delayed activation of caspase-independent apoptosis during heart failure in transgenic mice overexpressing caspase inhibitor CrmA

Although caspase activation is generally thought to be necessary to induce apoptosis, recent evidence suggests that apoptosis can be activated in the setting of caspase inhibition. In this study, we tested the hypothesis that caspase-independent apoptotic pathways contribute to the development of heart failure in the absence of caspase activation. Acute cardiomyopathy was induced using a single dose of doxorubicin (Dox, 20 mg/kg) injected into male wild-type (WT) and transgenic (Tg) mice with a cardiac-specific expression of cytokine response modifier A (CrmA), a known caspase inhibitor. Early (6 day) survival was significantly better in CrmA Tg (81%) than WT (38%) mice. Twelve days after Dox injection, however, the mortality benefit had dissipated, and increased cardiac apoptosis was observed in both groups. There was, however, a significantly greater release of apoptosis-inducing factor (AIF) from mitochondria to cytosol in CrmA Tg compared with WT mice, which suggests that an enhancement of activation in caspase-independent apoptotic pathways had occurred. The administration of a poly(ADP-ribose) polymerase-1 inhibitor, 4-amino-1,8-naphthalimide (4-AN), to Dox-treated mice resulted in significantly improved cardiac function, a significant blockade of AIF released from mitochondria, and decreased cardiac apoptosis. There were also significantly improved survival in WT (18% without 4-AN vs. 89% with 4-AN) and CrmA Tg (13% without 4-AN vs. 93% with 4-AN) mice 12 days after Dox injection. In conclusion, these findings suggest that apoptosis can be induced in the heart lacking caspase activation via caspase-independent pathways and that enabling the inhibition of AIF activation may provide a significant cardiac benefit.

Dasatinib synergizes with JSI-124 to inhibit growth and migration and induce apoptosis of malignant human glioma cells

Background:

Src family kinases (SFK) collectively regulate a variety of cellular functions in many cancer types, including proliferation, invasion, motility, survival, differentiation, and angiogenesis. Although Dasatinib (BMS-354825), an ATP-competitive, small molecule tyrosine kinase inhibitor, suppresses the activity of SFKs at nanomolar concentrations, IC50 values for antiproliferative effects in glioma cell lines were well above the clinically achievable range, suggesting the need to interfere with other components of receptor-induced downstream signaling in order to achieve an optimal therapeutic effect.

Materials and Methods:

The cytotoxic effects of combining Src and STAT3 inhibition on glioma cell lines were evaluated using assays to measure cell proliferation, apoptosis and migration. Western blotting and immunocytochemistry was used to monitor its effects on cell signaling and morphology.

Results:

Silencing Src and STAT3 expression each partially inhibited cell proliferation and migration. In addition, JSI-124 significantly enhanced the efficacy of dasatinib in vitro. Combination of dasatinib and JSI-124 achieved significant inhibition of migration in all cell lines, which correlated with the inhibition of Src and downstream mediators of adhesion (e.g. focal adhesion kinase). Cells exposed to dasatinib and JSI-124 exhibited morphological changes that were consistent with an upstream role for Src in regulating focal adhesion complexes.

Conclusions:

Targeting the Src and STAT pathways may contribute to the treatment of cancers that demonstrate increased levels of these signaling mediators, including malignant human glioma. Clinical studies in these tumor types are warranted.

Proinsulin C-peptide regulates ribosomal RNA expression

Proinsulin C-peptide is internalized into cells, but a function of its intracellular localization has not been established. We now demonstrate that, upon cellular entry, C-peptide is localized to the nucleoli, where it promotes transcription of genes encoding for ribosomal RNA. We find that C-peptide binds to histones and enhances acetylation of lysine residue 16 of histone H4 at the promoter region of genes for ribosomal RNA. In agreement with synchrony of ribosomal RNA synthesis and cell proliferation, we show that C-peptide stimulates proliferation in chondrocytes and HEK-293 cells. This regulation of ribosomal RNA provides a mechanism by which C-peptide can exert transcriptional effects and implies that the peptide has growth factor activity.

The Cdk inhibitor p57(Kip2) controls LIM-kinase 1 activity and regulates actin cytoskeleton dynamics

The cyclin-dependent kinase inhibitor p57(Kip2) gene has been suggested to be a tumor suppressor gene, being inactivated in various cancer types, linked to tumor progression and poor patient outcome. Here, we report that p57(Kip2) interacts with the actin cytoskeleton modifying enzyme, LIM-kinase 1 (LIMK-1) but not LIMK-2. This interaction enhances activity of LIMK-1, independently of its activator Rho-associated kinase. This resulted in an increased phosphorylation and consequent inactivation of the actin depolymerization factor, cofilin. In accordance, selective p57(Kip2) expression promotes actin stress fiber formation in cancer cells. Fluorescence recovery after photobleaching analysis of fluorescent-labeled actin further demonstrated that p57(Kip2) expression results in reduction of actin protein mobile fraction, which affects its turnover rate in cell. Finally, we present evidence that the p57(Kip2) control of LIMK-1 ultimately affects cell mobility negatively. Thus, in addition to its established function in control of proliferation and cell death, these results indicate that p57(Kip2) is critical in the regulation of actin cytoskeleton dynamic and by this means migration ability of cancer cells.

Detection and quantification of the evolution dynamics of apoptosis using the PET voltage sensor 18F-fluorobenzyl triphenyl phosphonium

Apoptosis is a key mechanism in numerous pathologies. However, there are no effective noninvasive means available for an early detection and quantitative assessment of evolution dynamics of the apoptotic process. Here, we have characterized the ability of the novel PET voltage sensor (18)F-fluorobenzyl triphenyl phosphonium ((18)F-FBnTP) to quantify the time-dependent apoptotic action of the taxanes paclitaxel and docetaxel in vitro and in vivo.

METHODS

The duration-dependent treatment effect of paclitaxel on (18)F-FBnTP uptake was assayed in human MDA-MB-231 breast carcinoma cells. The expression of the proapoptotic Bax and antiapoptotic Bcl-2 mitochondrial proteins, release of the apoptogen cytochrome c, and activation of executioner caspase-3 were determined by Western blotting. The fraction of viable cells was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The effect of docetaxel on (18)F-FBnTP and (18)F-FDG uptake in orthotopic prostate tumors in mice was compared.

RESULTS

(18)F-FBnTP cellular uptake in viable cells declined linearly with the increasing duration of paclitaxel treatment, from 3 to 24 h, and plateaued at 48 h. The extent of decrease of (18)F-FBnTP correlated strongly with the Bax-to-Bcl-2 ratio (R(2) = 0.83) and release of cytochrome c (R(2) = 0.92), but preceded in time the caspase-3 cleavage. The P-glycoprotein blocker verapamil did not interfere with (18)F-FBnTP cellular uptake. (18)F-FBnTP prostate tumor contrast was greater than (18)F-FDG prostate tumor contrast. Docetaxel caused a marked decrease (52.4%) of (18)F-FBnTP tumor uptake, within 48 h, whereas (18)F-FDG was much less affected (12%).

CONCLUSION

The voltage sensor (18)F-FBnTP is a viable means for quantification of paclitaxel pharmacodynamics. (18)F-FBnTP permits the detection of paclitaxel apoptotic action in vivo earlier than does (18)F-FDG. (18)F-FBnTP may afford a novel approach for early detection and quantitative assessment of the cumulative-effect kinetics of proapoptotic drugs and conditions using PET.

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.

Trauma-hemorrhagic shock-induced pulmonary epithelial and endothelial cell injury utilizes different programmed cell death signaling pathways

Intestinal ischemia after trauma-hemorrhagic shock (T/HS) results in gut barrier dysfunction and the production/release of biologically active and tissue injurious factors in the mesenteric lymph, which, in turn, causes acute lung injury and a systemic inflammatory state. Since T/HS-induced lung injury is associated with pulmonary endothelial and epithelial cell programmed cell death (PCD) and was abrogated by mesenteric lymph duct ligation, we sought to investigate the cellular pathways involved. Compared with trauma-sham shock (T/SS) rats, a significant increase in caspase-3 and M30 expression was detected in the pulmonary epithelial cells undergoing PCD, whereas apoptosis-inducing factor (AIF), but not caspase-3, was detected in endothelial cells undergoing PCD. This AIF-mediated pulmonary endothelial PCD response was validated in an in situ femoral vein assay where endothelial cells were found to express AIF but not caspase-3. To complement these studies, human umbilical vein endothelial cell (HUVEC), human lung microvascular endothelial cell (HLMEC), and human alveolar type II epithelial cell (A549) lines were used as in vitro models. T/HS lymph induced the nuclear translocation of AIF in HUVEC and HLMEC, and caspase inhibition in these cells did not afford any cytoprotection. For proof of principle, AIF silencing in HUVEC reversed the cytotoxic effects of T/HS on cell viability and DNA fragmentation. In A549 cells, T/HS lymph activated caspase-3-mediated apoptosis, which was partially abrogated by N-benzyloxycarbonyl-Val-Ala-Asp (zVAD). Additionally, T/HS lymph did not cause the nuclear translocation of AIF in A549 cells. Collectively, T/HS-induced pulmonary endothelial PCD occurs via an AIF-dependent caspase-independent pathway, whereas epithelial cells undergo apoptosis by a caspase-dependent pathway.

Glutathione in Cancer Biology and Therapy

The glutathione (GSH) content of cancer cells is particularly relevant in regulating mutagenic mechanisms, DNA synthesis, growth, and multidrug and radiation resistance. In malignant tumors, as compared with normal tissues, that resistance associates in most cases with higher GSH levels within these cancer cells. Thus, approaches to cancer treatment based on modulation of GSH should control possible growth-associated changes in GSH content and synthesis in these cells. Despite the potential benefits for cancer therapy of a selective GSH-depleting strategy, such a methodology has remained elusive up to now. Metastatic spread, not primary tumor burden, is the leading cause of cancer death. For patient prognosis to improve, new systemic therapies capable of effectively inhibiting the outgrowth of seeded tumor cells are needed. Interaction of metastatic cells with the vascular endothelium activates local release of proinflammatory cytokines, which act as signals promoting cancer cell adhesion, extravasation, and proliferation. Recent work shows that a high percentage of metastatic cells with high GSH levels survive the combined nitrosative and oxidative stresses elicited by the vascular endothelium and possibly by macrophages and granulocytes. ?-Glutamyl transpeptidase overexpression and an inter-organ flow of GSH (where the liver plays a central role), by increasing cysteine availability for tumor GSH synthesis, function in combination as a metastatic-growth promoting mechanism. The present review focuses on an analysis of links among GSH, adaptive responses to stress, molecular mechanisms of invasive cancer cell survival and death, and sensitization of metastatic cells to therapy. Experimental evidence shows that acceleration of GSH efflux facilitates selective GSH depletion in metastatic cells.

The heat shock protein antagonist 17-AAG potentiates the activity of enzastaurin against malignant human glioma cells

Recent studies have suggested that the proliferation of malignant gliomas may result from activation of protein kinase C (PKC)-mediated pathways. Enzastaurin (LY317615), an acyclic bisindolylmaleimide, is an oral inhibitor of PKCbeta as well as other isoforms. The initial objective of this study was to assess the efficacy of enzastaurin in a series of malignant human glioma cell lines with diverse genomic alterations. Although enzastaurin independently produced a dose-dependent inhibition of cellular proliferation and decreased cell viability in each of the glioma cell lines examined, and partially down-regulated Akt and GSK3beta phosphorylation, median effective concentrations were at the upper limits of, or above, the clinically achievable range in all cell lines tested. We therefore examined whether the efficacy of enzastaurin could be enhanced by combination with the HSP90 antagonist, 17-AAG, which inhibits Akt and other signaling intermediates by a distinct mechanism. In comparison to the effect of enzastaurin alone, combination of enzastaurin with 17-AAG led to marked enhancement of antiproliferative and cytotoxic effects. Simultaneous exposure to both agents significantly increased the release of cytochrome c, as well as caspase 3 activation, Bax cleavage, and inhibition of Akt phosphorylation. Cells exposed to enzastaurin and 17-AAG also displayed a significant reduction in cell cycle regulatory proteins, such as CDK4 and CDK6. Taken together, these findings suggest that the efficacy of enzastaurin can be potentiated by the addition of 17-AAG, and indicate that combining molecularly targeted therapies may provide a more effective strategy than single-agent therapy to treat patients with malignant gliomas.

Combinatorial action of the HDAC inhibitor trichostatin A and etoposide induces caspase-mediated AIF-dependent apoptotic cell death in non-small cell lung carcinoma cells

Commonly used regimens in cancer therapy rely on the induction of apoptotic cell death, and drug resistance can be attributed, at least in part, to a disabled apoptotic program. Non-small cell lung carcinomas (NSCLC), exhibit an intrinsic resistance to chemotherapy. Here, we show that co-treatment with etoposide (VP16) and the pan-histone deacetylase (HDAC) inhibitor trichostatin A (TSA), but not valproic acid (VPA), induced apoptotic cell death in drug-resistant NSCLC cells. Co-treatment, but not single treatment, with VP16 and TSA induced apoptosis in a caspase-dependent manner accompanied by a crucial decrease in Bcl-xL expression allowing Bax activation and subsequent initiation of the apoptosis inducing factor (AIF)-dependent death pathway. Importantly, AIF proved to be required for the effects of TSA/VP16 as RNA knockdown of AIF resulted in a complete abolishment of TSA/VP16-induced apoptotic cell death in drug-resistant NSCLC cells. Our results thus provide evidence for the requirement of both caspase-dependent and caspase-independent apoptotic pathways in TSA/VP16-mediated death of drug-resistant NSCLC cells, and extend previous suggestions that HDAC inhibitors in combination with conventional chemotherapeutic drugs could be valuable in the treatment of NSCLC cancer and other malignancies in which Bcl-xL is overexpressed.

Apoptosis effector mechanisms: a requiem performed in different keys

Apoptosis is the regulated form of cell death utilized by metazoans to remove unneeded, damaged, or potentially deleterious cells. Certain manifestations of apoptosis may be associated with the proteolytic activity of caspases. These changes are often held as hallmarks of apoptosis in dying cells. Consequently, many regard caspases as the central effectors or executioners of apoptosis. However, this "caspase-centric" paradigm of apoptotic cell death does not appear to be as universal as once believed. In fact, during apoptosis the efficacy of caspases may be highly dependent on the cytotoxic stimulus as well as genetic and epigenetic factors. An ever-increasing number of studies strongly suggest that there are effectors in addition to caspases, which are important in generating apoptotic signatures in dying cells. These seemingly caspase-independent effectors may represent evolutionarily redundant or failsafe mechanisms for apoptotic cell elimination. In this review, we will discuss the molecular regulation of caspases and various caspase-independent effectors of apoptosis, describe the potential context and/or limitations of these mechanisms, and explore why the understanding of these processes may have relevance in cancer where treatment is believed to engage apoptosis to destroy tumor cells.

Restoration of tissue factor pathway inhibitor-2 in a human glioblastoma cell line triggers caspase-mediated pathway and apoptosis

PURPOSE

The induction of apoptotic pathways in cancer cells offers a novel and potentially useful approach to improve patient responses to conventional chemotherapy. Tissue factor pathway inhibitor-2 (TFPI-2) is a protease inhibitor that is abundant in the extracellular matrix and highly expressed in noninvasive cells but absent or undetectable in highly invasive human glioblastoma cells.

EXPERIMENTAL DESIGN

Using a recombinant adeno-associated viral vector carrying human TFPI-2 cDNA, we stably expressed TFPI-2 in U-251 cells, a highly invasive human glioblastoma cell line. Our previous studies showed that restoration of TFPI-2 in glioblastomas effectively prevents cell proliferation, angiogenesis, and tumor invasion. In this study, we determined whether TFPI-2 restoration could induce apoptosis through the caspase-mediated signaling pathway.

RESULTS

The results from nuclear chromatin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and fluorescence-activated cell sorting analysis showed increased apoptosis in U-251 cells after restoration of TFPI-2. Caspase-9 and caspase-3 activity assays showed increased activity, indicating enhanced apoptosis. Immunofluorescence for cleaved caspase-9 and caspase-3 depicted increased expression and colocalization of both molecules. Western blot analysis showed increased transcriptional activities of Fas ligand, tumor necrosis factor-alpha, Bax, Fas-associated death domain, and tumor necrosis factor receptor 1-associated death domain as well as elevated levels of cleaved caspases and poly(ADP-ribose) polymerase. Semiquantitative reverse transcription-PCR depicted increased expression of tumor necrosis factor-alpha and Fas ligand and the related death domains tumor necrosis factor receptor 1-associated death domain and Fas-associated death domain.

CONCLUSIONS

Taken together, these results show that restoration of TFPI-2 activates both intrinsic and extrinsic caspase-mediated, proapoptotic signaling pathways and induces apoptosis in U-251 cells. Furthermore, our study suggests that recombinant adeno-associated viral vector-mediated gene expression offers a novel tool for cancer gene therapy.

Characterization of membrane potential-dependent uptake of the novel PET tracer 18F-fluorobenzyl triphenylphosphonium cation

PURPOSE

Mitochondrial dysfunction has been attributed a critical role in the etiology and pathogenesis of numerous diseases, and is manifested by alterations of the organelle's membrane potential (Deltapsi(m)). This suggests that Deltapsi(m) measurement can be highly useful for diagnostic purposes. In the current study, we characterized the capability of the novel PET agent (18)F-fluorobenzyl triphenylphosphonium ((18)F-FBnTP) to assess Deltapsi(m), compared with the well-established voltage sensor (3)H-tetraphenylphosphonium ((3)H-TPP).

METHODS

(18)F-FBnTP and (3)H-TPP uptake under conditions known to alter Deltapsi(m) and plasma membrane potential (Deltapsi(p)) was assayed in the H345 lung carcinoma cell line. (18)F-FBnTP biodistribution was assessed in CD1 mice using dynamic PET and ex vivo gamma well counting.

RESULTS

(18)F-FBnTP and (3)H-TPP demonstrated similar uptake kinetics and plateau concentrations in H345 cells. Stepwise membrane depolarization resulted in a linear decrease in (18)F-FBnTP cellular uptake, with a slope (-0.58+/-0.06) and correlation coefficient (0.94+/-0.07) similar (p>0.17) to those measured for (3)H-TPP (-0.63+/-0.06 and 0.96+/-0.05, respectively). Selective collapse of Deltapsi(m) caused a substantial decrease in cellular uptake for (18)F-FBnTP (81.6+/-8.1%) and (3)H-TPP (85.4+/-6.7%), compared with control. Exposure to the proapoptotic staurosporine, known to collapse Deltapsi(m), resulted in a decrease of 68.7+/-10.1% and 71.5+/-8.4% in (18)F-FBnTP and (3)H-TPP cellular uptake, respectively. (18)F-FBnTP accumulated mainly in kidney, heart and liver.

CONCLUSION

(18)F-FBnTP is a mitochondria-targeting PET radiopharmaceutical responsive to alterations in membrane potential with voltage-dependent performance similar to that of (3)H-TPP. (18)F-FBnTP is a promising new voltage sensor for detection of physiological and pathological processes associated with mitochondrial dysfunction, such as apoptosis, using PET.

T-cell ubiquitin ligand affects cell death through a functional interaction with apoptosis-inducing factor, a key factor of caspase-independent apoptosis

The lymphoid protein T-cell ubiquitin ligand (TULA)/suppressor of T-cell receptor signaling (Sts)-2 is associated with c-Cbl and ubiquitylated proteins and has been implicated in the regulation of signaling mediated by protein-tyrosine kinases. The results presented in this report indicate that TULA facilitates T-cell apoptosis independent of either T-cell receptor/CD3-mediated signaling or caspase activity. Mass spectrometry-based analysis of protein-protein interactions of TULA demonstrates that TULA binds to the apoptosis-inducing protein AIF, which has previously been shown to function as a key factor of caspase-independent apoptosis. Using RNA interference, we demonstrate that AIF is essential for the apoptotic effect of TULA. Analysis of the subcellular localization of TULA and AIF together with the functional analysis of TULA mutants is consistent with the idea that TULA enhances the apoptotic effect of AIF by facilitating the interactions of AIF with its apoptotic co-factors, which remain to be identified. Overall, our results shed new light on the biological functions of TULA, a recently discovered protein, describing its role as one of very few known functional interactors of AIF.

The cell cycle inhibitor p57(Kip2) promotes cell death via the mitochondrial apoptotic pathway

The p57(Kip2) gene belongs to the Cip/Kip family of cyclin-dependent kinase (CDK) inhibitors and has been suggested to be a tumor suppressor gene, being inactivated in various types of human cancers. However, little is known concerning p57(Kip2) possible interplay with the apoptotic cell death machinery and its possible implication for cancer. Here, we report that selective p57(Kip2) expression sensitizes cancer cells to apoptotic agents such as cisplatin, etoposide and staurosporine (STS) via a mechanism, which does not require p57(Kip2)-mediated inhibition of CDK. Translocation of p57(Kip2) to mitochondria occurs within 20 min after STS application. In fact, p57(Kip2) primarily promotes the intrinsic apoptotic pathways, favoring Bax activation and loss of mitochondrial transmembrane potential, consequent release of cytochrome-c into cytosol, caspase-9 and caspase-3 activation. In accordance, Bcl2 overexpression or voltage-dependent anion channel (VDAC) inhibition is able to inhibit p57(Kip2) cell death promoting effect. Thus, in addition to its established function in control of proliferation, these results reveal a mechanism whereby p57(Kip2) influences the mitochondrial apoptotic cell death pathway in cancer cells.

Role of HPV E6 proteins in preventing UVB-induced release of pro-apoptotic factors from the mitochondria

Apoptotic elimination of UV-damaged cells from the epidermis is an important step in preventing both the emergence and expansion of cells with carcinogenic potential. A pivotal event in apoptosis is the release of apoptogenic factors from the mitochondria, although the mechanisms by which the different proteins are released are not fully understood. Here we demonstrate that UV radiation induced the mitochondrial to nuclear translocation of apoptosis inducing factor (AIF) in normal skin. The human papillomavirus (HPV) E6 protein prevented release of AIF and other apoptotic factors such as cytochrome c and Omi from mitochondria of UV-damaged primary epidermal keratinocytes and preserved mitochondrial integrity. shRNA silencing of Bak, a target for E6-mediated proteolysis, demonstrated the requirement of Bak for UV-induced AIF release and mitochondrial fragmentation. Furthermore, screening non-melanoma skin cancer biopsies revealed an inverse correlation between HPV status and AIF nuclear translocation. Our results indicate that the E6 activity towards Bak is a key factor that promotes survival of HPV-infected cells that facilitates tumor development.

Targeting GSK-3: a promising approach for cancer therapy?

Glycogen synthase kinase (GSK)-3 has emerged as one of the most attractive therapeutic targets for the treatment of multiple neurological diseases, including Alzheimer's, stroke and bipolar disorders, as well as noninsulin-dependent diabetes mellitus and inflammation. Although the prominent role of GSK-3 in the adenomatous polyposis coli (APC)-beta-catenin destruction complex implies that inhibition of GSK-3 could possibly lead to tumor promotion through the activation of beta-catenin, several recent studies have shed new light on the activity of GSK-3 in cancer and provide insight into the molecular mechanisms by which it regulates tumor cell proliferation and survival of multiple human malignancies. In fact, GSK-3beta is a critical regulator of nuclear factor (NF)kappaB nuclear activity, suggesting that inhibition of GSK-3beta could be effective in the treatment of a wide variety of tumors with constitutively active NFkappaB. Herein, the authors will discuss the current understanding of the role of GSK-3 in human cancer and its potential as a therapeutic target.

Coadministration of Sorafenib with Rottlerin Potently Inhibits Cell Proliferation and Migration in Human Malignant Glioma Cells

Mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) are activated in the majority of gliomas and contribute to tumor cell growth and survival. Sorafenib (Bay43-9006; Nexavar) is a dual-action Raf and vascular endothelial growth factor receptor inhibitor that blocks receptor phosphorylation and MAPK-mediated signaling and inhibits growth in a number of tumor types. Because our initial studies of this agent in a series of glioma cell lines showed only partial growth inhibition at clinically achievable concentrations, we questioned whether inhibition of PKC signaling using the PKC-delta inhibitor rottlerin might potentiate therapeutic efficacy. Proliferation assays, apoptosis induction studies, and Western immunoblot analysis were conducted in cells treated with sorafenib and rottlerin as single agents or in combination. Sorafenib and rottlerin reduced proliferation in all cell lines when used as single agents, and the combination produced marked potentiation of growth inhibition. Flow-cytometric measurements of cells stained with Annexin V-propidium iodide and immunocytochemical assessment of cytochrome c and apoptosis-inducing factor release demonstrated that addition of rottlerin resulted in significantly higher levels of apoptosis than sorafenib alone. In addition, the combination of sorafenib and rottlerin reduced or completely inhibited the phosphorylation of extracellular signal-regulated kinase and Akt and down-regulated cell cycle regulatory proteins such as cyclin-D1, cyclin-D3, cyclin-dependent kinase (cdk)4, and cdk6 in a dose- and time-dependent manner. Our results clearly indicate that inhibition of PKC-delta signaling enhances the antiproliferative effect of sorafenib in malignant human glioma cell lines and support the examination of combinations of signaling inhibitors in these tumors.

Expression of apoptosome pathway-related transcripts in non-small cell lung cancer

PURPOSE

Tumour cells killing by cytotoxic therapies largely depends on triggering the intrinsic apoptosome-mediated caspase activation pathway but it had never been evaluated whether the expression of transcripts encoding the core components of apoptosome pathway is altered in non-small cell lung carcinoma (NSCLC).

METHODS

We investigated the expression status of several apoptosome pathway-related transcripts including Apaf-1, procaspase-9, -3, -6, -7 and Smac in tumour and lung tissue samples from 65 surgically treated NSCLC patients and in 10 NSCLC cell lines with using real time RT-PCR.

RESULTS

NSCLC tissues and cell lines showed significantly increased expression of procaspase-9, -3, -6 and Smac mRNAs as compared to the lungs and expression of these transcripts was simultaneously upregulated in a subset of NSCLCs belonging to different histopathological type, grade and stage categories. The expression of procaspase-7 mRNA in NSCLC tissues and cell lines and lungs was not significantly different. By contrast, the expression of Apaf-1 mRNA was frequently downregulated in the tumours as compared to matched lungs. Nevertheless, the examined NSCLC cell lines showed significantly higher expression of Apaf-1 mRNA than the lungs. The expression of Apaf-1, procaspase-9 and -6 mRNAs was higher in lung adenocarcinomas as compared to squamous cell lung carcinomas but the expression levels of the studied apoptosome pathway-related transcripts in the tumours were independent of tumour's grade and stage.

CONCLUSIONS

The results of the present study suggest that there is a subgroup of NSCLCs, which may be intrinsically primed for apoptosis through upregulated expression of transcripts encoding the apoptosome pathway components.