Cell Death Machinery Research Articles

REACTIVE OXYGEN OR NITROGEN SPECIES (ROS/ RNS) AND RESPONSE OF ANTIOXIDANTS AS SCAVENGERS DURING BIOTIC STRESS IN PLANTS: AN OVERVIEW

Phytopathogens have evolved diverse independent and complex modes of penetrating and accessing plant cellular contents. The synthesis of reactive oxygen or nitrogen species (ROS/RNS) by the utilization of molecular oxygen during plant–pathogen interactions results in to oxidative burst, a signaling cascade to defense. ROS array includes singlet oxygen, the hydroxyperoxyl radical, the superoxide anion, hydrogen peroxide, the hydroxyl radical and the closely related reactive nitrogen species, nitric oxide. ROS acts synergistically directs to signal amplification to drive the hypersensitive reaction (HR) and initiates systemicdefenses. The role of ROS in successful pathogenesis, it is ideal to inhibit the cell death machinery selectively and simultaneously to monitor other defense and pathogenesis-related processes. With the understanding of the interplay underlying the localized activation of the oxidative burst following perception of pathogen avirulence signals and key downstream responses including gene activation, cell death, and long-distance signaling, novel strategies will be developed for engineering enhanced protection against pathogens by manipulation of the oxidative burst and oxidant-mediated signal pathways. In this over review, it is reported the different roles of ROS/RNS in host–pathogen interactions with example on Alternaria- Sesamum interaction.

GPER-independent inhibition of adrenocortical cancer growth by G-1 involves ROS/Egr-1/BAX pathway

We previously demonstrated that treatment of the H295R adrenocortical cancer cell line with the non-steroidal, high-affinity GPER (G protein-coupled estrogen receptor 1) agonist G-1 reduced tumor growth in vitro and in vivo through a GPER independent action. Moreover, we observed that G-1 treatment induces cell-cycle arrest and apoptosis following a sustained ERK1/2 activation. However, the precise mechanisms causing these effects were not clarified. Starting from our preliminary published results, we performed a microarray study that clearly evidenced a strong and significative up-regulation of EGR-1 gene in H295R cells treated for 24h with micromolar concentration of G-1. The microarray findings were confirmed by RT-PCR and Western-blot analysis as well as by immunofluorescence that revealed a strong nuclear staining for EGR-1 after G-1 treatment. EGR-1 is a point of convergence of many intracellular signaling cascades that control tumor cell growth and proliferation as well as others that relate to cell death machinery. Here we found that the increased Egr-1 expression was a consequence of G-1-mediated ROS-dependent ERK activation that were promptly reversed by the presence of the antioxidant n-acetyl-cysteine. Finally, we observed that silencing EGR-1 gene expression reversed the main effects induced by G-1 in ACC cells, including upregulation of the negative regulator of cell cycle, p21Waf1/Cip1 and the positive regulator of mitochondrial apoptotic pathway, BAX, as well as the cell growth inhibition. The identified ROS/MAPK/Egr-1/BAX pathway as a potential off-target effect of the G-1 could be useful in implementing the pharmacological approach for ACC therapy.

BOK promotes chemical-induced hepatocarcinogenesis in mice

BCL-2-related ovarian killer (BOK) is a conserved and widely expressed BCL-2 family member with sequence homology to pro-apoptotic BAX and BAK, but with poorly understood pathophysiological function. Since several members of the BCL-2 family are critically involved in the regulation of hepatocellular apoptosis and carcinogenesis we aimed to establish whether loss of BOK affects diethylnitrosamine (DEN)-induced hepatocarcinogenesis in mice. Short-term exposure to DEN lead to upregulation of BOK mRNA and protein in the liver. Of note, induction of CHOP and the pro-apoptotic BH3-only proteins PUMA and BIM by DEN was strongly reduced in the absence of BOK. Accordingly, Bok-/- mice were significantly protected from DEN-induced acute hepatocellular apoptosis and associated inflammation. As a consequence, Bok-/- animals were partially protected against chemical-induced hepatocarcinogenesis showing fewer and, surprisingly, also smaller tumors than WT controls. Gene expression profiling revealed that downregulation of BOK results in upregulation of genes involved in cell cycle arrest. Bok-/- hepatocellular carcinoma (HCC) displayed higher expression levels of the cyclin kinase inhibitors p19INK4d and p21cip1. Accordingly, hepatocellular carcinoma in Bok-/- animals, BOK-deficient human HCC cell lines, as well as non-transformed cells, showed significantly less proliferation than BOK-proficient controls. We conclude that BOK is induced by DEN, contributes to DEN-induced hepatocellular apoptosis and resulting hepatocarcinogenesis. In line with its previously reported predominant localization at the endoplasmic reticulum, our findings support a role of BOK that links the cell cycle and cell death machineries upstream of mitochondrial damage.

EBV and Apoptosis: The Viral Master Regulator of Cell Fate?

Epstein–Barr virus (EBV) was first discovered in cells from a patient with Burkitt lymphoma (BL), and is now known to be a contributory factor in 1–2% of all cancers, for which there are as yet, no EBV-targeted therapies available. Like other herpesviruses, EBV adopts a persistent latent infection in vivo and only rarely reactivates into replicative lytic cycle. Although latency is associated with restricted patterns of gene expression, genes are never expressed in isolation; always in groups. Here, we discuss (1) the ways in which the latent genes of EBV are known to modulate cell death, (2) how these mechanisms relate to growth transformation and lymphomagenesis, and (3) how EBV genes cooperate to coordinately regulate key cell death pathways in BL and lymphoblastoid cell lines (LCLs). Since manipulation of the cell death machinery is critical in EBV pathogenesis, understanding the mechanisms that underpin EBV regulation of apoptosis therefore provides opportunities for novel therapeutic interventions.

Webinar | Deciphering cancer: Investigating cell death mechanisms

Cell death, including autophagy, necroptosis, and apoptosis, is a physiological process critical for normal development and function of multicellular organisms. Many of the signals that elicit cell death converge on mitochondria, which regulate cell death by a pivotal process called mitochondrial outer membrane permeabilization (MOMP). In apoptosis, MOMP is tightly regulated by the Bcl-2 family of proteins, composed of both proapoptotic (Bax, Bak, Bid, Bim) and antiapoptotic (Bcl-2, Bcl-xL, Bcl-W) members, which act in part by governing mitochondrial death signaling through cytochrome C release and subsequent activation of caspases. Irrespective of caspase activity, MOMP can lead to cell death by causing a progressive decline in mitochondrial function. Under certain circumstances, however, a cell can survive cell death; its survival may have pathophysiological consequences leading to cancer, autoimmunity, neurodegeneration, and resistance to cancer therapies. This webinar will examine how identification of dysregulated cell-death mechanisms underpinning various pathologies can be exploited to develop novel treatments for cancer and neurodegenerative diseases that directly activate the cell-death machinery. View the Webinar

Cold atmospheric helium plasma causes synergistic enhancement in cell death with hyperthermia and an additive enhancement with radiation

Cold atmospheric plasmas (CAPs) have been proposed as a novel therapeutic method for its anti-cancer potential. However, its biological effects in combination with other physical modalities remain elusive. Therefore, this study examined the effects of cold atmospheric helium plasma (He-CAP) in combination with hyperthermia (HT) 42 °C or radiation 5 Gy. Synergistic enhancement in the cell death with HT and an additive enhancement with radiation were observed following He-CAP treatment. The synergistic effects were accompanied by increased intracellular reactive oxygen species (ROS) production. Hydrogen peroxide (H2O2) and superoxide (O2•–) generation was increased immediately after He-CAP treatment, but fails to initiate cell death process. Interestingly, at late hour’s He-CAP-induced O2•– generation subsides, however the combined treatment showed sustained increased intracellular O2•– level, and enhanced cell death than either treatment alone. He-CAP caused marked induction of ROS in the aqueous medium, but He-CAP-induced ROS seems insufficient or not completely incorporated intra-cellularly to activate cell death machinery. The observed synergistic effects were due to the HT effects on membrane fluidity which facilitate the incorporation of He-CAP-induced ROS into the cells, thus results in the enhanced cancer cell death following combined treatment. These findings would be helpful when establishing a therapeutic strategy for CAP in combination with HT or radiation.

Using biological technologies for preservation of Malus sieversii natural populations in the Zhongar–Alatau State National Nature Park of Kazakhstan

Apple ring rot, which is caused by Botryosphaeria dothidea, severely affects apple production. The mechanisms employed in apple cells against B. dothidea remain unknown. In this research, the pathogen infection mode and the relationship between cell death and disease resistance in ‘Fuji’/B. dothidea interaction pathosystem were investigated. By using transmission electron microscopy (TEM), our research showed that the pathogen infects apple cells both intracellularly and extracellularly. However, compared with that in immature fruit, the incidence of hyphae in the interior of mature apple fruit cells increased dramatically, suggesting that cell wall-mediated penetration resistance could be important in apple resistance against B. dothidea. TEM ultrastructural characterization identified the nuclear morphology of programmed cell death induction in both apple fruit and callus cells under B. dothidea infection. Overexpression of MdVDAC2 (MDP0000271281), which encodes an outer-membrane localized anion channel protein in mitochondria, significantly promoted cell death under B. dothidea infection and simultaneously inhibited pathogen infection, suggesting that cell death represents a disease resistance mechanism in apple against B. dothidea infection. Furthermore, BdCatalase (KAF4307763), a cytochrome P450 family protein BdCYP52A4 (KAF4300696), and subtilisin-domain containing proteins were identified from B. dothidea-secreted proteins, which suggested the potential involvement of active oxygen species and phytoalexins in combating B. dothidea infection and triggering or dampening apple resistance. Collectively, our research suggested that cell wall-mediated penetration resistance, programmed cell death machinery and microbial effector-interrelated signaling were among strategies recruited in apple to combat B. dothidea. The current research laid the foundation for further investigations into resistance mechanisms in apple.

Abstract 2315: Overcoming treatment resistance in cisplatin-resistant ovarian carcinoma cells by tissue-specific miRNAs

Abstract Ovarian cancer is a common human cancer with a poor outcome and a high risk of death. Due to resistances to current standard therapies (carboplatin and paclitaxel for 3 to 6 cycles) additional therapeutic approaches are required and novel specific biomarkers for ovarian cancer patients are necessary. MicroRNAs (miRNA) are conserved, small noncoding RNAs regulating gene expression by binding to their target mRNA which have been shown to regulate biological processes including apoptosis. Apoptosis is a conserved, irreversible process that allows cells to undergo a highly regulated form of cell death. However, the final role of miRNAs in apoptotic signaling has not yet been fully determined. Modulating the expression of key molecular components of the cell death machinery is an attractive strategy for cancer therapy overcoming chemo drug resistance. To extend the pool of potential miRNA as anticancer agents and biomarkers, we transferred a high content miRNA screening for pro-apoptotic miRNAs to human cancer cell lines. Based on the high recovery rate of apoptosis inducing miRNAs in SKOV3 cells analyses were extended to multiple ovarian carcinoma cell lines with different genetic background. After transfection of miR-1912-5p the apoptosis rate increased strongly in cisplatin-resistant cells. In combination treatment with carboplatin the apoptotic effect increased after transfection of miR-1912-5p in the cisplatin-resistant A2780 cells. Furthermore, miR-1912-5p, miR-147b and miR-3073a showed significant apoptosis induction in the various ovarian cancer cell lines alone and in combined therapy with carboplatin. Western Blot analysis revealed an enhanced expression of the pro-apoptotic proteins Bak1 and Bax and a decrease inBcl2 and Bcl-xL. We characterized the miRNAs in regard to their endogenous expression and detected an enhanced expression after apoptosis induction by chemotherapeutic drugs. Finally, analysis of The Cancer Genome Atlas data showed an influence on the median survival of ovarian cancer patients (> 69 years). Our data indicate a potential benefit of tissue specific pro-apoptotic miRNAs in regard to cisplatin-resistant cells. Furthermore the study identified novel pro-apoptotic miRNAs with their potential use as novel therapeutic entities or prognostic biomarkers for ovarian cancer. Citation Format: Michael Kleemann, Jeremias Bereuther, Simon Fischer, Kim Marquart, Simon Hänle, Kristian Unger, Verena Jendrossek, Christian U. Riedel, René Handrick, Kerstin Otte. Overcoming treatment resistance in cisplatin-resistant ovarian carcinoma cells by tissue-specific miRNAs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2315. doi:10.1158/1538-7445.AM2017-2315

Coupled Caspase and N-End Rule Ligase Activities Allow Recognition and Degradation of Pluripotency Factor LIN-28 during Non-Apoptotic Development

Recent findings suggest that components of the classical cell death machinery also have important non-cell-death (non-apoptotic) functions in flies, nematodes, and mammals. However, the mechanisms for non-canonical caspase substrate recognition and proteolysis, and the direct roles for caspases in gene expression regulation, remain largely unclear. Here we report that CED-3 caspase and the Arg/N-end rule pathway cooperate to inactivate the LIN-28 pluripotency factor in seam cells, a stem-like cell type in Caenorhabditis elegans, thereby ensuring proper temporal cell fate patterning. Importantly, the caspase and the E3 ligase execute this function in anon-additive manner. We show that CED-3 caspase and the E3 ubiquitin ligase UBR-1 form a complex that couples their invivo activities, allowing for recognition and rapid degradation of LIN-28 and thus facilitating a switch in developmental programs. The interdependence of these proteolytic activities provides a paradigm for non-apoptotic caspase-mediated protein inactivation.

An update on immunotherapies including chimeric antigen receptor T-cells therapy and stem cell transplantation in chronic lymphocytic leukemia

Immunotherapy has become a cornerstone of therapy in oncology. For chronic lymphocytic leukemia (CLL), the treatment landscape has been changing quickly. What historically has been a disease treated with chemoimmunotherapy, and transplant in select cases, now has several newly available, targeted therapies. Many of the newly approved therapies are targeted at the B cell receptor pathway, and also have notable effect on the tumor microenvironment. Additionally, there are a number of trials looking at immune checkpoint blockade in CLL with promise noted when combined with other immune modulating therapies. Many advances have also been made in cellular therapies in CLL, including methods of allogeneic stem cells transplantation and bioengineered chimeric antigen receptor T-cells (CAR-T) which direct the immune system to kill cancer cells expressing specific antigens. The latter therapy may ultimately allow patients to avoid the risks of an allogeneic transplant while harnessing a T cell vs . leukemia effect. The future of therapy in CLL may include utilization of novel immunotherapies in combination with agents that target key pathways such a B cell receptor signaling and cell death machinery.

Abstracts from the In Vitro Toxicology Society Annual Meeting Radisson Blu Hotel Glasgow, United Kingdom November 14–15, 2016

Abstracts from the In Vitro Toxicology Society Annual Meeting Radisson Blu Hotel Glasgow, United Kingdom November 14–15, 2016

Flavonoids and darkness lower PCD in senescing Vitis vinifera suspension cell cultures.

BackgroundSenescence is a key developmental process occurring during the life cycle of plants that can be induced also by environmental conditions, such as starvation and/or darkness. During senescence, strict control of genes regulates ordered degradation and dismantling events, the most remarkable of which are genetically programmed cell death (PCD) and, in most cases, an upregulation of flavonoid biosynthesis in the presence of light.Flavonoids are secondary metabolites that play multiple essential roles in development, reproduction and defence of plants, partly due to their well-known antioxidant properties, which could affect also the same cell death machinery. To understand further the effect of endogenously-produced flavonoids and their interplay with different environment (light or dark) conditions, two portions (red and green) of a senescing grapevine callus were used to obtain suspension cell cultures. Red Suspension cell Cultures (RSC) and Green Suspension cell Cultures (GSC) were finally grown under either dark or light conditions for 6 days.ResultsDarkness enhanced cell death (mainly necrosis) in suspension cell culture, when compared to those grown under light condition. Furthermore, RSC with high flavonoid content showed a higher viability compared to GSC and were more protected toward PCD, in accordance to their high content in flavonoids, which might quench ROS, thus limiting the relative signalling cascade. Conversely, PCD was mainly occurring in GSC and further increased by light, as it was shown by cytochrome c release and TUNEL assays.ConclusionsEndogenous flavonoids were shown to be good candidates for exploiting an efficient protection against oxidative stress and PCD induction. Light seemed to be an important environmental factor able to induce PCD, especially in GSC, which lacking of flavonoids were not capable of preventing oxidative damage and signalling leading to senescence.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0917-y) contains supplementary material, which is available to authorized users.

The contribution of the programmed cell death machinery in innate immune cells to lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic multi-factorial autoimmune disease initiated by genetic and environmental factors, which in combination trigger disease onset in susceptible individuals. Damage to the kidney as a consequence of lupus nephritis (LN) is one of the most prevalent and severe outcomes, as LN affects up to 60% of SLE patients and accounts for much of SLE-associated morbidity and mortality. As remarkable strides have been made in unlocking new inflammatory mechanisms associated with signaling molecules of programmed cell death pathways, this review explores the available evidence implicating the action of these pathways specifically within dendritic cells and macrophages in the control of kidney disease. Although advancements into the underlying mechanisms responsible for inducing cell death inflammatory pathways have been made, there still exist areas of unmet need. By understanding the molecular mechanisms by which dendritic cells and macrophages contribute to LN pathogenesis, we can improve their viability as potential therapeutic targets to promote remission.

Abstract 3527: Inhibition of autophagosome closure promotes iDISC-mediated apoptosis in AML cells

Abstract Macroautophagy (hereafter referred to as autophagy) is a lysosomal degradation process whereby cellular components, such as damaged organelles, are enclosed in double-membrane structures called autophagosomes and delivered to lysosomes for degradation and recycling. Autophagy is known to be essential for cancer pathogenesis and progression through its intimate crosstalk with programed cell death machinery, apoptosis. However, the role of autophagy in apoptosis pathway remains highly controversial and context-dependent, which makes developing autophagy-targeted anti-cancer treatments hard to achieve. We have previously reported that autophagosomal membranes can serve as a platform for caspase-8 activation through the assembly of an intracellular Death-Inducing Signaling Complex (iDISC). In the present study, we demonstrate that inhibition of phagophore closure by depleting Atg2A/B stabilizes iDISCs and induces caspase-8-initiated apoptosis in acute myeloid leukemia (AML) cells. We found that knockout of Atg2A/B, but not Atg7, promotes the oligomerization of caspase-8 on Atg16L- and LC3-positive phagophore membranes upon nutrient starvation. Starvation-induced capase-8 activation and apoptosis induction in Atg2A/B-deficient cells were strongly suppressed by the inhibition of caspase-8. These results suggest that autophagy inhibition at the phagophore closure step can shift cytoprotective autophagy to a pro-death mechanism and thus may be a promising strategy to enhance the efficacy of anticancer therapy. Citation Format: Zhenyuan Tang, Yoshinori Takahashi, Hong-Gang Wang. Inhibition of autophagosome closure promotes iDISC-mediated apoptosis in AML cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3527.

Hydra as a model organism to decipher the toxic effects of copper oxide nanorod: Eco-toxicogenomics approach.

Nanotechnology has emerged as a powerful field of applied research. However, the potential toxicity of nano-materials is a cause of concern. A thorough toxicological investigation is required before a nanomaterial is evaluated for application of any kind. In this context, there is concerted effort to find appropriate test systems to assess the toxicity of nanomaterials. Toxicity of a nanomaterial greatly depends on its physicochemical properties and the biological system with which it interacts. The present research was carried out with a view to generate data on eco-toxicological impacts of copper oxide nanorod (CuO NR) in Hydra magnipapillata 105 at organismal, cellular and molecular levels. Exposure of hydra to CuO NR resulted in severe morphological alterations in a concentration- as well as duration-dependent manner. Impairment of feeding, population growth, and regeneration was also observed. In vivo and in vitro analyses revealed induction of oxidative stress, genotoxicity, and molecular machinery of apoptotic cell death, accompanied by disruption of cell cycle progression. Taken together, CuO nanorod is potentially toxic to the biological systems. Also, hydra offers potential to be used as a convenient model organism for aquatic ecotoxicological risk assessment of nanomaterials.

Janus Kinase 1 Is Essential for Inflammatory Cytokine Signaling and Mammary Gland Remodeling.

Despite a wealth of knowledge about the significance of individual signal transducers and activators of transcription (STATs), essential functions of their upstream Janus kinases (JAKs) during postnatal development are less well defined. Using a novel mammary gland-specific JAK1 knockout model, we demonstrate here that this tyrosine kinase is essential for the activation of STAT1, STAT3, and STAT6 in the mammary epithelium. The loss of JAK1 uncouples interleukin-6-class ligands from their downstream effector, STAT3, which leads to the decreased expression of STAT3 target genes that are associated with the acute-phase response, inflammation, and wound healing. Consequently, JAK1-deficient mice exhibit impaired apoptosis and a significant delay in mammary gland remodeling. Using RNA sequencing, we identified several new JAK1 target genes that are upregulated during involution. These include Bmf and Bim, which are known regulators of programmed cell death. Using a BMF/BIM-double-knockout epithelial transplant model, we further validated that the synergistic action of these proapoptotic JAK1 targets is obligatory for the remodeling of the mammary epithelium. The collective results of this study suggest that JAK1 has nonredundant roles in the activation of particular STAT proteins and this tyrosine kinase is essential for coupling inflammatory cytokine signals to the cell death machinery in the differentiated mammary epithelium.

Identification and Characterization of Plant Cell Death-Inducing Secreted Proteins From Ustilaginoidea virens.

Ustilaginoidea virens (Cooke) Takah (telemorph Villosiclava virens) is an ascomycetous fungus that causes rice false smut, one of the most important rice diseases. Fungal effectors often play essential roles in host-pathogen coevolutionary interactions. However, little is known about the functions of U. virens effectors. Here, we performed functional studies on putative effectors in U. virens and demonstrated that 13 of 119 putative effectors caused necrosis or necrosis-like phenotypes in Nicotiana benthamiana. Among them, 11 proteins were confirmed to be secreted, using a yeast secretion system, and the corresponding genes are all highly induced during infection, except UV_44 and UV_4753. Eight secreted proteins were proven to trigger cell death or defenses in rice protoplasts and the secretion signal of these proteins is essential for their cell death-inducing activity. The ability of UV_44 and UV_1423 to trigger cell death is dependent on the predicted serine peptidase and ribonuclease catalytic active sites, respectively. We demonstrated that UV_1423 and UV_6205 are N-glycosylated proteins, which glycosylation has different impacts on their abilities to induce cell death. Collectively, the study identified multiple secreted proteins in U. virens with specific structural motifs that induce cell death or defense machinery in nonhost and host plants.

Programmed cell death and clearance of cell corpses in Caenorhabditis elegans.

Programmed cell death is critical to the development of diverse animal species from C. elegans to humans. In C. elegans, the cell death program has three genetically distinguishable phases. During the cell suicide phase, the core cell death machinery is activated through a protein interaction cascade. This activates the caspase CED-3, which promotes numerous pro-apoptotic activities including DNA degradation and exposure of the phosphatidylserine "eat me" signal on the cell corpse surface. Specification of the cell death fate involves transcriptional activation of the cell death initiator EGL-1 or the caspase CED-3 by coordinated actions of specific transcription factors in distinct cell types. In the cell corpse clearance stage, recognition of cell corpses by phagocytes triggers several signaling pathways to induce phagocytosis of apoptotic cell corpses. Cell corpse-enclosing phagosomes ultimately fuse with lysosomes for digestion of phagosomal contents. This article summarizes our current knowledge about programmed cell death and clearance of cell corpses in C. elegans.

Predicting Multi-Drug Inhibition Interactions based on Signaling Networks and Single Drug Dose-Response Information

Inhibiting multiple pathways/targets with combination drug therapies is widely used to maximize therapeutic benefit in many diseases. Therapeutic success can often be improved by concurrently and/or sequentially inhibiting multiple pathways/targets by combining drugs with different mechanisms of action. It is critical to understand potential drug interactions in developing and optimizing new multidrug regimens. We used data from experiments of single drugs (and few combinations) and existing signaling network knowledge from sources such as KEGG, to develop a statistical rescaling model to describe the effects of drugs on network topology. The model comprises a Hill equation for signals arriving at each receptor, a generic enzymatic rate equation to transmit signals among connecting genes, and a regression model to represent the cumulative effect of genes implicated in activation of the cell death machinery. We performed in silico experiments to derive a global sensitivity index of each term in the functional ANOVA of the dose-response model by generating doses of the drugs with the Quasi Monte-Carlo method. Only terms with large (principal) global sensitivity indices remain in the functional dose-response model. Thus, we reduce a high dimensional problem into one that can be managed experimentally. The model generates an index that indicates potential interactions of the drugs and the principal combinations, those associated with large global sensitivity indices, can be considered as candidates for further experimental validation.

Apoptosis as anticancer mechanism: function and dysfunction of its modulators and targeted therapeutic strategies.

Apoptosis is a form of programmed cell death that results in the orderly and efficient removal of damaged cells, such as those resulting from DNA damage or during development. Apoptosis can be triggered by signals from within the cell, such as genotoxic stress, or by extrinsic signals, such as the binding of ligands to cell surface death receptors. Deregulation in apoptotic cell death machinery is an hallmark of cancer. Apoptosis alteration is responsible not only for tumor development and progression but also for tumor resistance to therapies. Most anticancer drugs currently used in clinical oncology exploit the intact apoptotic signaling pathways to trigger cancer cell death. Thus, defects in the death pathways may result in drug resistance so limiting the efficacy of therapies. Therefore, a better understanding of the apoptotic cell death signaling pathways may improve the efficacy of cancer therapy and bypass resistance. This review will highlight the role of the fundamental regulators of apoptosis and how their deregulation, including activation of anti-apoptotic factors (i.e., Bcl-2, Bcl-xL, etc) or inactivation of pro-apoptotic factors (i.e., p53 pathway) ends up in cancer cell resistance to therapies. In addition, therapeutic strategies aimed at modulating apoptotic activity are briefly discussed.