Crosstalk between mitochondrial ROS and depolarization in the potentiation of TRAIL-induced apoptosis in human tumor cells

Establishing and Validating an Innovative Focal Adhesion-Linked Gene Signature for Enhanced Prognostic Assessment in Endometrial Cancer

Studies have highlighted the significant role of focal adhesion signaling in cancer. Nevertheless, its specific involvement in the pathogenesis of endometrial cancer and its clinical significance remains uncertain. We analyzed TCGA-UCEC and GSE119041 datasets with corresponding clinical data to investigate focal adhesion-related gene expression and their clinical significance. A signature, "FA-riskScore," was developed using LASSO regression in the TCGA cohort and validated in the GSE dataset. The FA-riskScore was compared with four existing models in terms of their prediction performance. We employed univariate and multivariate Cox regression analyses towards FA-riskScore to assess its independent prognostic value. A prognostic evaluation nomogram based on our model and clinical indexes was established subsequently. Biological and immune differences between high- and low-risk groups were explored through functional enrichment, PPI network analysis, mutation mining, TME evaluation, and single-cell analysis. Sensitivity tests on commonly targeted drugs were performed on both groups, and Connectivity MAP identified potentially effective molecules for high-risk patients. qRT-PCR validated the expressions of FA-riskScore genes. FA-riskScore, based on FN1, RELN, PARVG, and PTEN, indicated a poorer prognosis for high-risk patients. Compared with published models, FA-riskScore achieved better and more stable performance. High-risk groups exhibited a more challenging TME and suppressive immune status. qRT-PCR showed differential expression in FN1, RELN, and PTEN. Connectivity MAP analysis suggested that BU-239, potassium-canrenoate, and tubocurarine are effective for high-risk patients. This study introduces a novel prognostic model for endometrial cancer and offers insights into focal adhesion's role in cancer pathogenesis.

In vitro anticancer effects of recombinant anisoplin through activation of SAPK/JNK and downregulation of NFκB

Emerging chemotherapeutic resistance is considered as one of the major obstacles in breast cancer therapy. Fungal ribotoxins possess promising therapeutic potential against cancer owing to their ribosome-targeted protein synthesis inhibitory action. Though the entomopathogenic ribotoxin anisoplin was characterized in the earlier study, its therapeutic efficacy against cancer cells remained unexplored. In the current study, recombinant anisoplin has been successfully produced in Escherichia coli BL21(DE3) expression system and further purified and validated by in silico, biophysical and functional characterizations. Recombinant anisoplin significantly reduced the viability of MCF-7 breast cancer cells in a dose-dependent manner. It exhibited an IC50 value of 4 μM with concurrent 3.5 fold elevation in the intracellular reactive oxygen species. Anisoplin also resulted in depolarization of the mitochondrial membrane and subsequently induced apoptosis, as evident from flow cytometric analyses. In addition, MCF-7 cells significantly lost their self-renewal capability for clonal expansion and regeneration upon treatment. Immunoblotting experiments further confirmed activation of downstream JNK-dependent MAP kinase signaling pathway due to ribotoxic stress response generated by anisoplin through upregulation of phospho-SAPK/JNK expression. This upregulation was further correlated with the NFκB expression profile, leading to cell death, highlighting therapeutic potential of the recombinant anisoplin.

Cluster-Assembled Zirconia Substrates Accelerate the Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

Due to their high mechanical strength and good biocompatibility, nanostructured zirconia surfaces (ns-ZrOx) are widely used for bio-applications. Through supersonic cluster beam deposition, we produced ZrOx films with controllable roughness at the nanoscale, mimicking the morphological and topographical properties of the extracellular matrix. We show that a 20 nm ns-ZrOx surface accelerates the osteogenic differentiation of human bone marrow-derived MSCs (bMSCs) by increasing the deposition of calcium in the extracellular matrix and upregulating some osteogenic differentiation markers. bMSCs seeded on 20 nm ns-ZrOx show randomly oriented actin fibers, changes in nuclear morphology, and a reduction in mitochondrial transmembrane potential when compared to the cells cultured on flat zirconia (flat-ZrO₂) substrates and glass coverslips used as controls. Additionally, an increase in ROS, known to promote osteogenesis, was detected after 24 h of culture on 20 nm ns-ZrOx. All the modifications induced by the ns-ZrOx surface are rescued after the first hours of culture. We propose that ns-ZrOx-induced cytoskeletal remodeling transmits signals generated by the extracellular environment to the nucleus, with the consequent modulation of the expression of genes controlling cell fate.

Adverse PFAS effects on mouse oocyte in vitro maturation are associated with carbon-chain length and inclusion of a sulfonate group

OBJECTIVES

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that are widely used in various products. PFAS are characterized by their fluorinated carbon chains that make them hard to degrade and bioaccumulate in human and animals. Toxicological studies have shown PFAS toxic effects: cytotoxicity, immunotoxicity, neurotoxicity, and reproductive toxicity. However, it is still unclear how the structures of PFAS, such as carbon-chain length and functional groups, determine their reproductive toxicity.

METHODS AND RESULTS

By using a mouse-oocyte-in-vitro-maturation (IVM) system, we found the toxicity of two major categories of PFAS, perfluoroalkyl carboxylic acid (PFCA) and perfluoroalkyl sulfonic acid (PFSA), is elevated with increasing carbon-chain length and the inclusion of the sulfonate group. Specifically, at 600 μM, perfluorohexanesulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) reduced the rates of both germinal-vesicle breakdown (GVBD) and polar-body extrusion (PBE) as well as enlarged polar bodies. However, the shorter PFSA, perfluorobutanesulfonic acid (PFBS), and all PFCA did not show similar adverse cytotoxicity. Further, we found that 600 μM PFHxS and PFOS exposure induced excess reactive oxygen species (ROS) and decreased mitochondrial membrane potential (MMP). Cytoskeleton analysis revealed that PFHxS and PFOS exposure induced chromosome misalignment, abnormal F-actin organization, elongated spindle formation, and symmetric division in the treated oocytes. These meiotic defects compromised oocyte developmental competence after parthenogenetic activation.

CONCLUSIONS

Our study provides new information on the structure-toxicity relationship of PFAS.

Photodynamic therapy, a promising treatment approach for cutaneous infectious granulomas

Cutaneous infectious granulomas are mainly caused by fungi and bacteria. Antibiotics are the primary therapeutic choices for the diseases, but the drug-resistant pathogens become increasingly prevalent. Thus, there is an urgent need to explore novel approaches to treating cutaneous infectious granulomas. Photodynamic therapy (PDT) is widely used as an alternative treatment for various kinds of skin diseases, and evidence has been accumulating that PDT is also effective for the treatment of cutaneous infectious granulomas. In this narrative review, we sought to summarize the recent literature concerning the applications and mechanisms of PDT in the treatment of cutaneous infectious granulomas. Clinical and basic research has demonstrated that PDT is an effective approach in treating fungal infections such as sporotrichosis and chromoblastomycosis. In addition, PDT is also used to treat atypical mycobacterial infections such as Mycobacterium marinum. PDT can significantly shorten the duration of antibiotics treatment, resulting in diminishment of adverse effects. The potential mechanisms of PDT are to kill the pathogens directly or elicit modulatory effects on the immune microenvironments. We conclude that PDT is a promising therapeutic choice for the treatment of cutaneous infectious granulomas.

Combating Cancer Stem-Like Cell-Derived Resistance to Anticancer Protein by Liposome-Mediated Acclimatization Strategy

Antibody-based therapeutics, which induce apoptosis of malignant cells by selectively binding to their receptors, hold tremendous promise for clinical cancer therapy. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received considerable interest due to its favorable capability of activating apoptosis in cancer cells by interacting with death receptors (DRs). However, cancer stem-like cells (CSCs) show deficient or lower DR and are highly resistant to TRAIL-mediated apoptosis limiting the therapeutic efficacy. Here, we report a liposome-mediated acclimatization strategy to overcome the CSC-emanated TRAIL resistance. The liposomal assemblies coencapsulating plasmid DNA encoding TRAIL and salinomycin enable cancer cells as protein generators to express TRAIL, and more importantly, can acclimatize resistant CSCs to be sensitized to the TRAIL-triggered apoptosis by salinomycin-induced upregulation of DR expression on CSCs. This programmable liposome-based drug codelivery system shows the potential to efficiently eliminate CSCs and inhibit CSC-enriched tumor growth in the orthotopic colon tumor mouse model.

Label-Free Target Identification Reveals the Anticancer Mechanism of a Rhenium Isonitrile Complex

Elucidation of the molecular mechanism of therapeutic agents and potential candidates is in high demand. Interestingly, rhenium-based complexes have shown a highly selective anticancer effect, only on cancer cells, unlike platinum-based drugs, such as cisplatin and carboplatin. These differences might be attributed to their different molecular targets. We confirmed that the target of tricarbonyl rhenium isonitrile polypyridyl (TRIP) complex is a protein, not DNA, using ICP-MS analysis and identified heat shock protein 60 (HSP60) as its target protein using a label-free target identification method. The subsequent biological evaluation revealed that TRIP directly inhibits the chaperone function of HSP60 and induces the accumulation of misfolded proteins in mitochondria, thereby leading to the activation of mitochondrial unfolded protein response (mtUPR)-mediated JNK2/AP-1/CHOP apoptotic pathway.

Histone acetylome-wide associations in immune cells from individuals with active Mycobacterium tuberculosis infection

Host cell chromatin changes are thought to play an important role in the pathogenesis of infectious diseases. Here we describe a histone acetylome-wide association study (HAWAS) of an infectious disease, on the basis of genome-wide H3K27 acetylation profiling of peripheral blood granulocytes and monocytes from persons with active Mycobacterium tuberculosis (Mtb) infection and healthy controls. We detected >2,000 differentially acetylated loci in either cell type in a Singapore Chinese discovery cohort (n = 46), which were validated in a subsequent multi-ethnic Singapore cohort (n = 29), as well as a longitudinal cohort from South Africa (n = 26), thus demonstrating that HAWAS can be independently corroborated. Acetylation changes were correlated with differential gene expression. Differential acetylation was enriched near potassium channel genes, including KCNJ15, which modulates apoptosis and promotes Mtb clearance in vitro. We performed histone acetylation quantitative trait locus (haQTL) analysis on the dataset and identified 69 candidate causal variants for immune phenotypes among granulocyte haQTLs and 83 among monocyte haQTLs. Our study provides proof-of-principle for HAWAS to infer mechanisms of host response to pathogens.

Genome-wide histone acetylation profiling in cohorts of patients with active and latent tuberculosis reveals acetylation changes in host immune cells modulating potassium channel expression and apoptosis response.

Guaiazulene derivative 1,2,3,4-tetrahydroazuleno[1,2-b] tropone reduces the production of ATP by inhibiting electron transfer complex II

Molecularly targeted therapy has been used for treatment of various types of cancer. However, cancer cells often acquire resistance to molecularly targeted drugs that inhibit specific molecular abnormalities, such as constitutive activation of kinases. Even in cancer cells that have acquired resistance, enhanced anabolism, including the synthesis of nucleotides, amino acids and lipids, is common to normal cancer cells. Therefore, there is a renewed interest in effectively eliminating cancer cells by specifically targeting their abnormal energy metabolism. Multiple strategies are currently being developed for mitochondrial-targeted cancer therapy, with agents targeting oxidative phosphorylation, glycolysis, the tricarboxylic acid cycle and apoptosis. In this study, we found that one of the guaiazulene derivatives, namely, 1,2,3,4-tetrahydroazuleno[1,2-b] tropone (TAT), inhibited the proliferation of cancer cell lines stronger than that of normal cells. In addition, we showed that TAT inhibited energy production in cancer cell lines, resulting in apoptosis. Analyses done in cancer cell lines and in the animal model Caenorhabditis elegans suggested that TAT acts on the mitochondrial electron transfer complex II and suppresses cellular energy production by inhibiting oxidative phosphorylation across species. These results suggest that TAT could represent a novel anticancer agent that selectively targets mitochondria.

Evaluating the anticancer properties and real-time electrochemical extracellular bio-speciation of bis (1,10-phenanthroline) silver (I) acetate monohydrate in the presence of A549 lung cancer cells

According to the American Cancer Society report (2019-2021), the majority (63%) of stage III non-small cell lung cancer (NSCLC) patients are prescribed with chemo and/or radiation therapies, with 5-year relative survival rates of just 19%. Thus, directed drug development, toward personalised cancer treatment, is widely recognised as a necessary strategy in drug discovery research. However, broad generalisations on the modes of action of bioinorganic compounds are not conducive to tailored drug design, hence, fundamental mechanistic research is essential in realising personalised healthcare. In this work, anticancer properties of bis (1,10-phenanthroline) silver (I) acetate monohydrate (Ag-Phen), toward A549 lung cancer cells are presented. Biological assays were carried out to evaluate the effect of Ag-Phen on cell viability, reactive oxygen species generation and mitochondrial membrane potentials. In tandem with the biological assays, electrochemistry was employed to determine the real-time concentrations of intact Ag-Phen and dissociated Ag⁺ in the extracellular medium using platinum microelectrodes, as a function of cellular exposure time. Observations from the assays conducted include, Ag-Phen induced cytotoxicity (IC₅₀ 4.5 μM at 72 h) and 2-fold ROS generation, and a 50% decrease in mitochondrial membrane potentials with respect to equivalent concentrations of Ag⁺ and 1,10-phenanthroline. Bio-speciation studies, conducted electrochemically at platinum microelectrodes, revealed almost 50% of the Ag-Phen had dissociated after 2 h. Significant reductions in concentrations of dissociated Ag⁺ (from 67.7 μM to 6.7 μM), and the Ag-Phen complex (from 50.2 μM to 11.7 μM) between 4 and 24 h from the extracellular medium, indicate cellular uptake of both. This novel method facilitates the real-time identification and quantification of electroactive species, both the intact Ag-Phen and Ag⁺, in the presence of A549 cells.

Cytotoxic and Apoptotic Activity of Aglaforbesin Derivative Isolated from Aglaia loheri Merr. on HCT116 Human Colorectal Cancer Cells

Background:

The genus Aglaia (Meliaceae) is an established source of many anticancer compounds. The study evaluated the leaf extracts of Aglaia loheri, a tree native to the Philippines, as potential source of anticancer compounds.

Methods:

Using bioassay-guided fractionation, A. loheri leaf extract was subjected to various chromatographic techniques and step-wise application of MTT assay on human colorectal carcinoma cells, HCT116, to determine the cytotoxic fractions. The most cytotoxic HPLC isolate was structurally identified using 1D and 2D NMR and its apoptotic effect was assessed by JC-1 staining, caspase 3/7 assay and TUNEL assay.

Results:

After stepwise chromatography fractionation, an HPLC isolate, structurally identified as aglaforbesin derivative (AFD), demonstrated potent cytotoxicity against HCT116. AFD exhibited strong toxicity (IC₅₀ = 1.13 ±0.07 µg/mL) and high selectivity on HCT116 than normal human kidney cells (HK-2). AFD-induced toxicity to HCT116 is possibly through the stimulation of the apoptotic signaling pathway via caspase 3/7 activation and DNA fragmentation independent of mitochondrial membrane depolarization.

Conclusion:

AFD exhibited selective cytotoxicity and apoptotic activity to HCT116 and could be further developed as anticancer drug lead.

Downregulation of dihydrolipoyl dehydrogenase by UVA suppresses melanoma progression via triggering oxidative stress and altering energy metabolism

Melanoma, the most severe form of skin cancer, has poor prognosis and is resistant to chemotherapy. Targeting cancer metabolism is a promising approach in cancer therapeutics. Dihydrolipoyl dehydrogenase (DLD) is a mitochondrial enzyme with diaphorase activity. Here we report a pivotal role of DLD in melanoma cell progression and proliferation. Suppression DLD expression by low intensity UVA (125 mJ/cm²) increased intracellular ROS production and decreased mitochondrial membrane potential thereby inducing autophagy cell death which were confirmed by increased LC3BII and decreased p62 expression in melanoma cells. Knockdown of DLD in melanoma cells also showed similar results. More so, suppression of DLD significantly inhibits in vivo melanoma growth and tumor proliferation. In addition, suppression of DLD increased the NAD+/NADH ratio in melanoma cells and also inhibits TCA cycle related metabolites. DLD downregulation markedly increased α-ketoglutarate and decreased succinic acid suggesting that DLD suppression may have decreased TCA cycle downstream metabolites, resulting in the alteration of mitochondrial energy metabolism Thus the downregulation of DLD induced autophagic cell death in melanoma cells and inhibits in vivo tumor growth and proliferation by increasing ROS production and altering energy metabolism. Our findings suggest that DLD plays a pivotal role in melanoma progression and proliferation.

Pathological and Pharmacological Roles of Mitochondrial Reactive Oxygen Species in Malignant Neoplasms: Therapies Involving Chemical Compounds, Natural Products, and Photosensitizers

Oxidative stress plays an important role in cellular processes. Consequently, oxidative stress also affects etiology, progression, and response to therapeutics in various pathological conditions including malignant tumors. Oxidative stress and associated outcomes are often brought about by excessive generation of reactive oxygen species (ROS). Accumulation of ROS occurs due to dysregulation of homeostasis in an otherwise strictly controlled physiological condition. In fact, intracellular ROS levels are closely associated with the pathological status and outcome of numerous diseases. Notably, mitochondria are recognized as the critical regulator and primary source of ROS. Damage to mitochondria increases mitochondrial ROS (mROS) production, which leads to an increased level of total intracellular ROS. However, intracellular ROS level may not always reflect mROS levels, as ROS is not only produced by mitochondria but also by other organelles such as endoplasmic reticulum and peroxisomes. Thus, an evaluation of mROS would help us to recognize the biological and pathological characteristics and predictive markers of malignant tumors and develop efficient treatment strategies. In this review, we describe the pathological significance of mROS in malignant neoplasms. In particular, we show the association of mROS-related signaling in the molecular mechanisms of chemically synthesized and natural chemotherapeutic agents and photodynamic therapy.

Cellular and Molecular Aspects of Anti-Melanoma Effect of Minocycline-A Study of Cytotoxicity and Apoptosis on Human Melanotic Melanoma Cells

Minocycline is a tetracycline compound with pleiotropic pharmacological properties. In addition to its antibacterial action, it shows many non-antimicrobial effects, including an anti-cancer activity. The anti-cancer action was confirmed in studies on ovarian carcinoma cells, hepatocellular carcinoma cells, glioma cells, or acute myeloid leukemia cells. Malignant melanoma remains a serious medical problem despite the extensive knowledge of the disease. The low effectiveness of the standard treatment, as well as the resistance to therapy, result in high mortality rates. This work aimed to investigate the potential and mechanisms of anti-melanoma action of minocycline. Human skin melanotic melanoma cell line COLO 829 was used in the study. The obtained results showed that minocycline decreased cell viability and inhibited the growth of melanoma cells, proportional to the drug concentration as well as to the time of incubation. The EC50 values were calculated to be 78.6 µM, 31.7 µM, and 13.9 µM for 24 h, 48 h, and 72 h, respectively. It was observed that treated cells had a disturbed cell cycle and significantly changed morphology. Moreover, minocycline caused a decrease in mitochondrial membrane potential and an increase in cells with a low level of reduced thiols. Finally, it was found that the anti-melanoma effect of minocycline was related to the induction of apoptosis. The drug activated caspases 8, 9, and 3/7 as well as increased the number of annexin V-positive cells. The presented results show that minocycline possesses anti-melanoma potential.

Non-Thermal Plasma Couples Oxidative Stress to TRAIL Sensitization through DR5 Upregulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in various tumor cells without affecting most normal cells. Despite being in clinical testing, novel strategies to induce TRAIL-mediated apoptosis are in need to overcome cancer cell unresponsiveness and resistance. Plasma-activated medium (PAM) markedly stimulates reactive oxygen/nitrogen species (ROS/RNS)-dependent apoptosis in cancer cells. We investigate the capability of PAM and TRAIL (PAM/TRAIL) combination therapy to overcome TRAIL resistance and improve the anticancer efficacy of TRAIL. The combinatorial treatment of PAM and TRAIL shows synergistic effects on growth inhibition in TRAIL-resistant cancer cells via augmented apoptosis by two attributes. DR5 (TRAIL-R2) transcription by CHOP is upregulated in a PAM-generated ROS/RNS-dependent manner, and PAM itself upregulates PTEN expression mediated by suppression of miR-425 which is involved in Akt inactivation, leading to increased apoptosis induction. Treatment of cancer cell lines with the antioxidant N-acetylcysteine reduces the extent of membrane dysfunction and the expression of both CHOP-DR5 and miR-425-PTEN axes, attenuating PAM/TRAIL-induced cancer cell apoptosis. These data suggest that PAM/TRAIL treatment is a novel approach to sensitizing cancer cells to TRAIL-induced apoptosis and overcoming TRAIL resistance. PAM is a promising candidate for further investigations as a chemotherapeutic sensitizer in the treatment of cancer.

Aspirin Induces Mitochondrial Ca2+ Remodeling in Tumor Cells via ROS‒Depolarization‒Voltage-Gated Ca2+ Entry

Aspirin (acetylsalicylic acid) and its metabolite salicylate, have an anti-melanoma effect by evoking mitochondrial dysfunction through poorly understood mechanisms. Depolarization of the plasma membrane potential leads to voltage-gated Ca²⁺ entry (VGCE) and caspase-3 activation. In the present study, we investigated the role of depolarization and VGCE in aspirin’s anti-melanoma effect. Aspirin and to a lesser extent, salicylate (≥2.5 mM) induced a rapid (within seconds) depolarization, while they caused comparable levels of depolarization with a lag of 2~4 h. Reactive oxygen species (ROS) generation also occurred in the two-time points, and antioxidants abolished the early ROS generation and depolarization. At the same concentrations, the two drugs induced apoptotic and necrotic cell death in a caspase-independent manner, and antioxidants and Ca²⁺ channel blockers prevented cell death. Besides ROS generation, reduced mitochondrial Ca²⁺ (Ca²⁺_m) and mitochondrial membrane potential preceded cell death. Moreover, the cells expressed the Ca_v1.2 isoform of l-type Ca²⁺ channel, and knockdown of Ca_v1.2 abolished the decrease in Ca²⁺_m. Our findings suggest that aspirin and salicylate induce Ca²⁺_m remodeling, mitochondrial dysfunction, and cell death via ROS-dependent depolarization and VGCE activation.

Tannic Acid Promotes TRAIL-Induced Extrinsic Apoptosis by Regulating Mitochondrial ROS in Human Embryonic Carcinoma Cells

: Human embryonic carcinoma (EC; NCCIT) cells have self-renewal ability and pluripotency. Cancer stem cell markers are highly expressed in NCCIT cells, imparting them with the pluripotent nature to differentiate into other cancer types, including breast cancer. As one of the main cancer stem cell pathways, Wnt/β-catenin is also overexpressed in NCCIT cells. Thus, inhibition of these pathways defines the ability of a drug to target cancer stem cells. Tannic acid (TA) is a natural polyphenol present in foods, fruits, and vegetables that has anti-cancer activity. Through Western blotting and PCR, we demonstrate that TA inhibits cancer stem cell markers and the Wnt/β-catenin signaling pathway in NCCIT cells and through a fluorescence-activated cell sorting analysis we demonstrated that TA induces sub-G1 cell cycle arrest and apoptosis. The mechanism underlying this is the induction of mitochondrial reactive oxygen species (ROS) (mROS), which then induce the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated extrinsic apoptosis pathway instead of intrinsic mitochondrial apoptosis pathway. Moreover, ribonucleic acid sequencing data with TA in NCCIT cells show an elevation in TRAIL-induced extrinsic apoptosis, which we confirm by Western blotting and real-time PCR. The induction of human TRAIL also proves that TA can induce extrinsic apoptosis in NCCIT cells by regulating mROS.

The Mitochondrial Ca2+ Overload via Voltage-Gated Ca2+ Entry Contributes to an Anti-Melanoma Effect of Diallyl Trisulfide

Allium vegetables such as garlic (Allium sativum L.) are rich in organosulfur compounds that prevent human chronic diseases, including cancer. Of these, diallyl trisulfide (DATS) exhibits anticancer effects against a variety of tumors, including malignant melanoma. Although previous studies have shown that DATS increases intracellular calcium (Ca2+) in different cancer cell types, the role of Ca2+ in the anticancer effect is obscure. In the present study, we investigated the Ca2+ pathways involved in the anti-melanoma effect. We used melittin, the bee venom that can activate a store-operated Ca2+ entry (SOCE) and apoptosis, as a reference. DATS increased apoptosis in human melanoma cell lines in a Ca2+-dependent manner. It also induced mitochondrial Ca2+ (Ca2+mit) overload through intracellular and extracellular Ca2+ fluxes independently of SOCE. Strikingly, acidification augmented Ca2+mit overload, and Ca2+ channel blockers reduced the effect more significantly under acidic pH conditions. On the contrary, acidification mitigated SOCE and Ca2+mit overload caused by melittin. Finally, Ca2+ channel blockers entirely inhibited the anti-melanoma effect of DATS. Our findings suggest that DATS explicitly evokes Ca2+mit overload via a non-SOCE, thereby displaying the anti-melanoma effect.

Activation of Piezo1 sensitizes cells to TRAIL-mediated apoptosis through mitochondrial outer membrane permeability

TRAIL specifically induces apoptosis in cancer cells without affecting healthy cells. However, TRAIL’s cancer cytotoxicity was insufficient in clinical trials. Circulatory-shear stress is known to sensitize cancer cells to TRAIL. In this study, we examine the mechanism of this TRAIL sensitization with the goal of translating it to static conditions. GsMTx-4, a Piezo1 inhibitor, was found to reduce shear stress-related TRAIL sensitization, implicating Piezo1 activation as a potential TRAIL-sensitizer. The Piezo1 agonist Yoda1 recreated shear stress-induced TRAIL sensitization under static conditions. A significant increase in apoptosis occurred when PC3, COLO 205, or MDA-MB-231 cells were treated with Yoda1 and TRAIL in combination, but not in Bax-deficient DU145 cells. Calpastatin inhibited apoptosis in Yoda1-TRAIL treated cells, indicating that calpain activation is necessary for apoptosis by Yoda1 and TRAIL. Yoda1 and TRAIL treated PC3 cells showed increased mitochondrial outer membrane permeability (MOMP), mitochondrial depolarization, and activated Bax. This implies that Piezo1 activation sensitizes cancer cells to TRAIL through a calcium influx that activates calpains. The Calpains then induce MOMP by enhancing Bax activation. From these experiments a computational model was developed to simulate apoptosis for cells treated with TRAIL and increased calcium. The computational model elucidated the proapoptotic or antiapoptotic roles of Bax, Bcl-2, XIAP, and other proteins important in the mitochondrial-apoptotic signaling pathway.

Methylene Blue-Mediated Photodynamic Therapy Induces Macrophage Apoptosis via ROS and Reduces Bone Resorption in Periodontitis

Aim

To investigate whether methylene blue-mediated photodynamic therapy (MB-PDT) can affect the "fate" of macrophages in vitro or in periodontitis tissues and to explore the potential mechanism.

Methods

For in vitro treatments, THP-1 macrophages were divided into three experimental groups: C/control, no treatment; MB, methylene blue treatment; and MB-PDT, MB and laser irradiation treatment. Then, apoptosis and apoptosis-related proteins were detected in each group. For in vivo treatments, periodontitis was ligature-induced in the first molars of the bilateral maxilla in 12 Sprague Dawley (SD) rats. After six weeks, the ligatures were removed and all the induced molars underwent scaling and root planning (SRP). Then, the rats were divided into three groups according to the following treatments: SRP, saline solution; MB, phenothiazinium dye; and MB-PDT, MB and laser irradiation. Apoptotic macrophages, inflammation levels, and alveolar bone resorption in the periodontal tissues of rats were analyzed in each group.

Results

In vitro, flow cytometry analysis demonstrated that 10 μM MB and 40 J/cm² laser irradiation maximized the apoptosis rate (34.74%) in macrophages. Fluorescence probe and Western blot analyses showed that MB-PDT induced macrophage apoptosis via reactive oxygen species (ROS) and the mitochondrial-dependent apoptotic pathway. Conversely, the addition of exogenous antioxidant glutathione (GSH) and the pan-caspase inhibitor Z-VAD-FMK markedly reduced the apoptotic response in macrophages. In vivo, immunohistochemistry, histology, radiographic, and molecular biology experiments revealed fewer infiltrated macrophages, less bone loss, and lower IL-1β and TNF-α levels in the MB-PDT group than in the SRP and MB groups (P < 0.05). Immunohistochemistry analysis also detected apoptotic macrophages in the MB-PDT group.

Conclusion

MB-PDT could induce macrophage apoptosis in vitro and in rats with periodontitis. This may be another way for MB-PDT to relieve periodontitis in addition to its antimicrobial effect. Meanwhile, MB-PDT induced apoptosis in THP-1 macrophages via the mitochondrial caspase pathway.

MADD silencing enhances anti-tumor activity of TRAIL in anaplastic thyroid cancer

ATC is an aggressive disease with limited therapeutic options due to drug resistance. TRAIL is an attractive anti-cancer therapy that can trigger apoptosis in a cancer cell-selective manner. However, TRAIL resistance is a major clinical obstacle for its use as a therapeutic drug. Previously, we demonstrated that MADD is a cancer cell pro-survival factor that can modulate TRAIL resistance. However, its role, if any, in overcoming TRAIL resistance in ATC is unknown. First, we characterized ATC cell lines as either TRAIL resistant, TRAIL sensitive or moderately TRAIL sensitive and evaluated MADD expression/cellular localization. We determined the effect of MADD siRNA on cellular growth and investigated its effect on TRAIL treatment. We assessed the effect of combination treatment (MADD siRNA and TRAIL) on mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) levels. The effect of combination treatment on tumor growth was assessed in vivo. We found increased levels of MADD in ATC cells relative to Nthy-ori 3-1. MADD protein localizes in the cytosol (endoplasmic reticulum and Golgi body) and membrane. MADD knockdown resulted in spontaneous cell death that was synergistically enhanced when combined with TRAIL treatment in otherwise resistant ATC cells. Combination treatment resulted in a significant reduction in MMP and enhanced generation of ROS indicating the putative mechanism of action. In an orthotopic mouse model of TRAIL-resistant ATC, treatment with MADD siRNA alone reduced tumor growth that, when combined with TRAIL, resulted in significant tumor regressions. We demonstrated the potential clinical utility of MADD knockdown in sensitizing cells to TRAIL-induced apoptosis in ATC.

Daphnetin: A Novel Anti-Helicobacter pylori Agent

Background: Antibiotic-resistant H. pylori was increasingly found in infected individuals, which resulted in treatment failure and required alternative therapeutic strategies. Daphnetin, a coumarin-derivative compound, has multiple pharmacological activities. Methods: The mechanism of daphnetin on H. pylori was investigated focusing on its effect on cell morphologies, transcription of genes related to virulence, adhesion, and cytotoxicity to human gastric epithelial (GES-1) cell line. Results: Daphnetin showed good activities against multidrug resistant (MDR) H. pylori clinical isolates, with minimal inhibitory concentration (MIC) values ranging from 25 to 100 μg/mL. In addition, daphnetin exposure resulted in H. pylori morphological changes. Moreover, daphnetin caused increased translocation of phosphatidylserine (PS), DNA damage, and recA expression, and RecA protein production vs. control group. Of great importance, daphnetin significantly decreased H. pylori adhesion to GES-1 cell line vs. control group, which may be related to the reduced expression of colonization related genes (e.g., babA and ureI). Conclusions: These results suggested that daphnetin has good activity against MDR H. pylori. The mechanism(s) of daphnetin against H. pylori were related to change of membrane structure, increase of DNA damage and PS translocation, and decrease of H. pylori attachment to GES-1 cells.

PARK7 modulates autophagic proteolysis through binding to the N-terminally arginylated form of the molecular chaperone HSPA5

Macroautophagy is induced under various stresses to remove cytotoxic materials, including misfolded proteins and their aggregates. These protein cargoes are collected by specific autophagic receptors such as SQSTM1/p62 (sequestosome 1) and delivered to phagophores for lysosomal degradation. To date, little is known about how cells sense and react to diverse stresses by inducing the activity of SQSTM1. Here, we show that the peroxiredoxin-like redox sensor PARK7/DJ-1 modulates the activity of SQSTM1 and the targeting of ubiquitin (Ub)-conjugated proteins to macroautophagy under oxidative stress caused by TNFSF10/TRAIL (tumor necrosis factor [ligand] superfamily, member 10). In this mechanism, TNFSF10 induces the N-terminal arginylation (Nt-arginylation) of the endoplasmic reticulum (ER)-residing molecular chaperone HSPA5/BiP/GRP78, leading to cytosolic accumulation of Nt-arginylated HSPA5 (R-HSPA5). In parallel, TNFSF10 induces the oxidation of PARK7. Oxidized PARK7 acts as a co-chaperone-like protein that binds the ER-derived chaperone R-HSPA5, a member of the HSPA/HSP70 family. By forming a complex with PARK7 (and possibly misfolded protein cargoes), R-HSPA5 binds SQSTM1 through its Nt-Arg, facilitating self-polymerization of SQSTM1 and the targeting of SQSTM1-cargo complexes to phagophores. The 3-way interaction among PARK7, R-HSPA5, and SQSTM1 is stabilized by the Nt-Arg residue of R-HSPA5. PARK7-deficient cells are impaired in the targeting of R-HSPA5 and SQSTM1 to phagophores and the removal of Ub-conjugated cargoes. Our results suggest that PARK7 functions as a co-chaperone for R-HSPA5 to modulate autophagic removal of misfolded protein cargoes generated by oxidative stress.

Plasma-stimulated medium kills TRAIL-resistant human malignant cells by promoting caspase-independent cell death via membrane potential and calcium dynamics modulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and cold plasma-stimulated medium (PSM) have been shown to exhibit tumor-selective cytotoxicity and have emerged as promising new tools for cancer treatment. However, to date, at least to the best of our knowledge, no data are available as to which substance is more potent in killing cancer cells. Thus, in this study, we systematically compared their abilities to kill human malignant cells from different origins. We found that PSM dose-dependently killed TRAIL-resistant melanoma, osteosarcoma and neuroblastoma cells. Moreover, PSM had little cytotoxicity toward osteoblasts. PSM was more potent than TRAIL in inducing caspase-3/7 activation, mitochondrial network aberration and caspase-independent cell death. We also found that PSM was more potent in inducing plasma membrane depolarization (PMD) and disrupting endoplasmic-mitochondrial Ca²⁺ homeostasis. Moreover, persistent PMD was caused by different membrane-depolarizing agents; the use of the anti-type II diabetes drug, glibenclamide, alone caused mitochondrial fragmentation and enhanced TRAIL-induced Ca²⁺ modulation, mitochondrial network abnormalities and caspase-independent cell killing. These results demonstrate that PSM has a therapeutic advantage over TRAIL owing to its greater capacity to evoke caspase-independent cell death via mitochondrial network aberration by disrupting membrane potential and Ca²⁺ homeostasis. These findings may provide a strong rationale for developing PSM as a novel approach for the treatment of TRAIL-resistant malignant cells.

Stallion spermatozoa surviving freezing and thawing experience membrane depolarization and increased intracellular Na. Andrology 2017;5:1174-1182. [PMID: 28973824 DOI: 10.1111/andr.12419]

In order to gain insight of the modifications that freezing and thawing cause to the surviving population of spermatozoa, changes in the potential of the plasma membrane (Em) and intracellular Na⁺ content of stallion spermatozoa were investigated using flow cytometry. Moreover, caspase 3 activity was also investigated and the functionality of the Na⁺ -K⁺ ATPase pump was investigated before and after freezing and thawing. Cryopreservation caused a significant (p < 0.001) increase in the subpopulation of spermatozoa with depolarized sperm membranes, concomitantly with an increase (p < 0.05) in intracellular Na⁺ . These changes occurred in relation to activation of caspase 3 (p < 0.001). Cryopreservation reduced the activity of the Na-K⁺ pump and inhibition of the Na⁺ -K⁺ ATPase pump with ouabain-induced caspase 3 activation. It is concluded that inactivation of Na⁺ -K⁺ ATPase occurs during cryopreservation, an inhibition that could play a role explaining the accelerated senescence of the surviving population of spermatozoa.

Parkin functionally interacts with PGC-1α to preserve mitochondria and protect dopaminergic neurons

To understand the cause of Parkinson's disease (PD), it is important to determine the functional interactions between factors linked to the disease. Parkin is associated with autosomal recessive early-onset PD, and controls the transcription of PGC-1α, a master regulator of mitochondrial biogenesis. These two factors functionally interact to regulate the turnover and quality of mitochondria, by increasing both mitophagic activity and mitochondria biogenesis. In cortical neurons, co-expressing PGC-1α and Parkin increases the number of mitochondria, enhances maximal respiration, and accelerates the recovery of the mitochondrial membrane potential following mitochondrial uncoupling. PGC-1α enhances Mfn2 transcription, but also leads to increased degradation of the Mfn2 protein, a key ubiquitylation target of Parkin on mitochondria. In vivo, Parkin has significant protective effects on the survival and function of nigral dopaminergic neurons in which the chronic expression of PGC-1α is induced. Ultrastructural analysis shows that these two factors together control the density of mitochondria and their interaction with the endoplasmic reticulum. These results highlight the combined effects of Parkin and PGC-1α in the maintenance of mitochondrial homeostasis in dopaminergic neurons. These two factors synergistically control the quality and function of mitochondria, which is important for the survival of neurons in Parkinson's disease.

Disrupting mitochondrial Ca2+ homeostasis causes tumor-selective TRAIL sensitization through mitochondrial network abnormalities

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has emerged as a promising anticancer agent with high tumor-selective cytotoxicity. The congenital and acquired resistance of some cancer types including malignant melanoma and osteosarcoma impede the current TRAIL therapy of these cancers. Since fine tuning of the intracellular Ca2+ level is essential for cell function and survival, Ca2+ dynamics could be a promising target for cancer treatment. Recently, we demonstrated that mitochondrial Ca2+ removal increased TRAIL efficacy toward malignant melanoma and osteosarcoma cells. Here we report that mitochondrial Ca2+ overload leads to tumor-selective sensitization to TRAIL cytotoxicity. Treatment with the mitochondrial Na+/Ca2+ exchanger inhibitor CGP-37157 and oxidative phosphorylation inhibitor antimycin A and FCCP resulted in a rapid and persistent mitochondrial Ca2+ rise. These agents also increased TRAIL sensitivity in a tumor-selective manner with a switching from apoptosis to a nonapoptotic cell death. Moreover, we found that mitochondrial Ca2+ overload led to increased mitochondrial fragmentation, while mitochondrial Ca2+ removal resulted in mitochondrial hyperfusion. Regardless of their reciprocal actions on the mitochondrial dynamics, both interventions commonly exacerbated TRAIL-induced mitochondrial network abnormalities. These results expand our previous study and suggest that an appropriate level of mitochondrial Ca2+ is essential for maintaining the mitochondrial dynamics and the survival of these cells. Thus, disturbing mitochondrial Ca2+ homeostasis may serve as a promising approach to overcome the TRAIL resistance of these cancers with minimally compromising the tumor-selectivity.

Current and upcoming mitochondrial targets for cancer therapy

Mitochondria are essential intracellular organelles that regulate energy metabolism, cell death, and signaling pathways that are important for cell proliferation and differentiation. Therefore, mitochondria are fundamentally implicated in cancer biology, including initiation, growth, metastasis, relapse, and acquired drug resistance. Based on these implications, mitochondria have been proposed as a major therapeutic target for cancer treatment. In addition to classical view of mitochondria in cancer biology, recent studies found novel pathophysiological roles of mitochondria in cancer. In this review, we introduce recent concepts of mitochondrial roles in cancer biology including mitochondrial DNA mutation and epigenetic modulation, energy metabolism reprogramming, mitochondrial channels, involvement in metastasis and drug resistance, and cancer stem cells. We also discuss the role of mitochondria in emerging cancer therapeutic strategies, especially cancer immunotherapy and CRISPR-Cas9 system gene therapy.

Mitochondrial Ca2+ removal amplifies TRAIL cytotoxicity toward apoptosis-resistant tumor cells via promotion of multiple cell death modalities

Ca2+ has emerged as a new target for cancer treatment since tumor-specific traits in Ca2+ dynamics contributes to tumorigenesis, malignant phenotypes, drug resistance, and survival in different tumor types. However, Ca2+ has a dual (pro-death and pro-survival) function in tumor cells depending on the experimental conditions. Therefore, it is necessary to minimize the onset of the pro-survival Ca2+ signals caused by the therapy. For this purpose, a better understanding of pro-survival Ca2+ pathways in cancer cells is critical. Here we report that Ca2+ protects malignant melanoma (MM) and osteosarcoma (OS) cells from tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) cytotoxicity. Simultaneous measurements using the site-specific Ca2+ probes showed that acute TRAIL treatment rapidly and dose-dependently increased the cytosolic Ca2+ concentration ([Ca2+]cyt) and mitochondrial Ca2+ concentration ([Ca2+]mit) Pharmacological analyses revealed that the [Ca2+]mit remodeling was under control of mitochondrial Ca2+ uniporter (MCU), mitochondrial permeability transition pore (MPTP), and a Ca2+ transport pathway sensitive to capsazepine and AMG9810. Ca2+ chelators and the MCU inhibitor ruthenium 360, an MPTP opener atractyloside, capsazepine, and AMG9810 all decreased [Ca2+]mit and sensitized these tumor cells to TRAIL cytotoxicity. The Ca2+ modulation enhanced both apoptotic and non-apoptotic cell death. Although the [Ca2+]mit reduction potentiated TRAIL-induced caspase-3/7 activation and cell membrane damage within 24 h, this potentiation of cell death became pronounced at 72 h, and not blocked by caspase inhibition. Our findings suggest that in MM and OS cells mitochondrial Ca2+ removal can promote apoptosis and non-apoptotic cell death induction by TRAIL. Therefore, mitochondrial Ca2+ removal can be exploited to overcome the resistance of these cancers to TRAIL.

MICU1 drives glycolysis and chemoresistance in ovarian cancer

Cancer cells actively promote aerobic glycolysis to sustain their metabolic requirements through mechanisms not always clear. Here, we demonstrate that the gatekeeper of mitochondrial Ca2+ uptake, Mitochondrial Calcium Uptake 1 (MICU1/CBARA1) drives aerobic glycolysis in ovarian cancer. We show that MICU1 is overexpressed in a panel of ovarian cancer cell lines and that MICU1 overexpression correlates with poor overall survival (OS). Silencing MICU1 in vitro increases oxygen consumption, decreases lactate production, inhibits clonal growth, migration and invasion of ovarian cancer cells, whereas silencing in vivo inhibits tumour growth, increases cisplatin efficacy and OS. Mechanistically, silencing MICU1 activates pyruvate dehydrogenase (PDH) by stimulating the PDPhosphatase-phosphoPDH-PDH axis. Forced-expression of MICU1 in normal cells phenocopies the metabolic aberrations of malignant cells. Consistent with the in vitro and in vivo findings we observe a significant correlation between MICU1 and pPDH (inactive form of PDH) expression with poor prognosis. Thus, MICU1 could serve as an important therapeutic target to normalize metabolic aberrations responsible for poor prognosis in ovarian cancer.

Redox signaling and oxidative stress: Cross talk with TNF-related apoptosis inducing ligand activity

Redox regulation plays a key role in several physiopathological contexts and free radicals, from nitric oxide and superoxide anion up to other forms of reactive oxygen species (ROS), have been demonstrated to be involved in different biological and regulatory processes. The data reported in the current literature describe a link between ROS, inflammation and programmed cell death that is attracting interest as new pathways to be explored and targeted for therapeutic purposes. In this light, there is also growing attention to the involvement of this link in the activity of the TNF-related apoptosis inducing ligand (TRAIL). TRAIL is a member of the TNF ligands super family able to mediate multiple intracellular signals, with the potential to lead to a range of biological effects in different cell types. In particular, the hallmark of TRAIL is the ability to induce selective apoptosis in transformed cells leaving normal cells almost unaffected and this feature has already opened the door to several clinical studies for cancer treatment. Moreover, TRAIL plays a role in several physiological and pathological processes of both innate and adaptive immune systems and of the cardiovascular context, with a strong clinical potential. Nonetheless, several issues still need to be clarified about the signaling mediated by TRAIL to gain deeper insight into its therapeutic potential. In this light, the aim of this review is to summarize the main preclinical evidences about the interplay between TRAIL and redox signaling, with particular emphasis to the implications in vascular physiopathology and cancer.

Human mesenchymal stem cells enhance the systemic effects of radiotherapy

The outcome of radiotherapy treatment might be further improved by a better understanding of individual variations in tumor radiosensitivity and normal tissue reactions, including the bystander effect. For many tumors, however, a definitive cure cannot be achieved, despite the availablity of more and more effective cancer treatments. Therefore, any improvement in the efficacy of radiotherapy will undoubtedly benefit a significant number of patients. Many experimental studies measure a bystander component of tumor cell death after radiotherapy, which highlights the importance of confirming these observations in a preclinical situation. Mesenchymal stem cells (MSCs) have been investigated for use in the treatment of cancers as they are able to both preferentially home onto tumors and become incorporated into their stroma. This process increases after radiation therapy. In our study we show that in vitro MSCs, when activated with a low dose of radiation, are a source of anti-tumor cytokines that decrease the proliferative activity of tumor cells, producing a potent cytotoxic synergistic effect on tumor cells. In vivo administration of unirradiated mesenchymal cells together with radiation leads to an increased efficacy of radiotherapy, thus leading to an enhancement of short and long range bystander effects on primary-irradiated tumors and distant-non-irradiated tumors. Our experiments indicate an increased cell loss rate and the decrease in the tumor cell proliferation activity as the major mechanisms underlying the delayed tumor growth and are a strong indicator of the synergistic effect between RT and MSC when they are applied together for tumor treatment in this model.

Distinct effects of TRAIL on the mitochondrial network in human cancer cells and normal cells: role of plasma membrane depolarization

Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) is a promising anticancer drug due to its tumor-selective cytotoxicity. Here we report that TRAIL exhibits distinct effects on the mitochondrial networks in malignant cells and normal cells. Live-cell imaging revealed that multiple human cancer cell lines and normal cells exhibited two different modes of mitochondrial responses in response to TRAIL and death receptor agonists. Mitochondria within tumor cells became fragmented into punctate and clustered in response to toxic stimuli. The mitochondrial fragmentation was observed at 4 h, then became more pronounced over time, and associated with apoptotic cell death. In contrast, mitochondria within normal cells such as melanocytes and fibroblasts became only modestly truncated, even when they were treated with toxic stimuli. Although TRAIL activated dynamin-related protein 1 (Drp1)-dependent mitochondrial fission, inhibition of this process by Drp1 knockdown or with the Drp1 inhibitor mdivi-1, potentiated TRAIL-induced apoptosis, mitochondrial fragmentation, and clustering. Moreover, mitochondrial reactive oxygen species (ROS)-mediated depolarization accelerated mitochondrial network abnormalities in tumor cells, but not in normal cells, and TRAIL caused higher levels of mitochondrial ROS accumulation and depolarization in malignant cells than in normal cells. Our findings suggest that tumor cells are more prone than normal cells to oxidative stress and depolarization, thereby being more vulnerable to mitochondrial network abnormalities and that this vulnerability may be relevant to the tumor-targeting killing by TRAIL.

Vitamin C attenuates the toxic effect of aristolochic acid on renal tubular cells via decreasing oxidative stress‑mediated cell death pathways

Aristolochic acid (AA) is a component of Chinese medicinal herbs, including asarum and aristolochia and has been used in Traditional Chinese Medicine for a long time. Recent studies found that AA has a cytotoxic effect resulting in nephropathy. These studies indicated that AA‑induced cytotoxicity is associated with increases in oxidative stress and caspase‑3 activation. The present study further demonstrated that AA mainly elevates the H2O2 ratio, leading to increases in oxidative stress. Furthermore, the results indicated that AA induces cell death can via caspase‑dependent and ‑independent pathways. It is desirable to identify means of inhibiting AA‑induced renal damage; therefore, the present study applied an anti‑oxidative nutrient, vitamin C, to test whether it can be employed to reduce AA‑induced cell cytotoxicity. The results showed that vitamin C decreased AA‑induced H2O2 levels, caspase‑3 activity and cytotoxicity in renal tubular cells. In conclusion, the present study was the first to demonstrate that AA‑induced increases of the H2O2 ratio resulted in renal tubular cell death via caspase‑dependent and ‑independent pathways, and that vitamin C can decrease AA‑induced increases in H2O2 levels and caspase‑3 activity to attenuate AA‑induced cell cytotoxicity.

TRAIL-Based High Throughput Screening Reveals a Link between TRAIL-Mediated Apoptosis and Glutathione Reductase, a Key Component of Oxidative Stress Response

A high throughput screen for compounds that induce TRAIL-mediated apoptosis identified ML100 as an active chemical probe, which potentiated TRAIL activity in prostate carcinoma PPC-1 and melanoma MDA-MB-435 cells. Follow-up in silico modeling and profiling in cell-based assays allowed us to identify NSC130362, pharmacophore analog of ML100 that induced 65-95% cytotoxicity in cancer cells and did not affect the viability of human primary hepatocytes. In agreement with the activation of the apoptotic pathway, both ML100 and NSC130362 synergistically with TRAIL induced caspase-3/7 activity in MDA-MB-435 cells. Subsequent affinity chromatography and inhibition studies convincingly demonstrated that glutathione reductase (GSR), a key component of the oxidative stress response, is a target of NSC130362. In accordance with the role of GSR in the TRAIL pathway, GSR gene silencing potentiated TRAIL activity in MDA-MB-435 cells but not in human hepatocytes. Inhibition of GSR activity resulted in the induction of oxidative stress, as was evidenced by an increase in intracellular reactive oxygen species (ROS) and peroxidation of mitochondrial membrane after NSC130362 treatment in MDA-MB-435 cells but not in human hepatocytes. The antioxidant reduced glutathione (GSH) fully protected MDA-MB-435 cells from cell lysis induced by NSC130362 and TRAIL, thereby further confirming the interplay between GSR and TRAIL. As a consequence of activation of oxidative stress, combined treatment of different oxidative stress inducers and NSC130362 promoted cell death in a variety of cancer cells but not in hepatocytes in cell-based assays and in in vivo, in a mouse tumor xenograft model.

Epothilone B induces human ovarian cancer OV-90 cell apoptosis via external pathway

We evaluated molecular events associated with apoptosis induced by Epothilone B (EpoB, Patupilone) and paclitaxel (PTX) in human ovarian papillary serous adenocarcinoma cell line (OV-90). Epothilones are compounds of natural origin with mechanisms of action similar to taxanes, but with more potent antiproliferative activity. Apoptosis was one of the major forms of cell death induced by EpoB. The mode of cell death was assessed colorimetrically, fluorimetrically, cytometry, and by immunoblot analyses through measuring DNA fragmentation, the level of TRAIL, the cleavage of poly(ADP-ribose) polymerase (PARP) and the activation of caspase-9, -8 and -3. We measured also additional markers of apoptosis, like phosphatidylserine externalization and morphological changes. Moreover, we estimated glycoprotein P (P-gp) activity in OV-90 ovarian cancer cell line. The studies indicated that the extrinsic pathway of apoptosis, which is triggered by certain TNF family members and engages their respective receptors on the surface of the target cell, was predominant. We were the first to have demonstrated (using immunoassay) the release of TNF-related apoptosis-inducing ligand (TRAIL) after treatment with EpoB. EpoB and PTX mediate activation of both initiator caspases-8 and -9, leading to the appearance of caspase-3. In EpoB treated cells, DNA fragmentation was also detected. EpoB leads to the reduction in DNA repair capacity. In summary, we report that Epothilone B induces apoptosis in OV-90 cells via a TRAIL and caspase 8-dependent pathway. PTX leads to smaller apoptotic events in comparison to EpoB.

Decreased expression of APAF-1 and increased expression of cathepsin B in invasive pituitary adenoma

PURPOSE

Apoptotic protease-activating factor-1 (APAF-1) and cathepsin B are important functional proteins in apoptosis; the former is involved in the intrinsic (mitochondrial) pathway, while the latter is associated with both intrinsic and extrinsic pathways. Changes in the expression of apoptosome-related proteins could be useful indicators of tumor development since a priori defects in the mitochondrial pathway might facilitate the inception and progression of human neoplasms. Our aim was to evaluate the profiles of APAF-1 and cathepsin B in relation with other molecules involved in apoptosis/proliferation and to correlate them with the aggressive behavior of invasive pituitary adenomas.

MATERIALS AND METHODS

APAF-1 and cathepsin B were assessed in tissue samples from 30 patients with pituitary adenomas, of which 16 were functional adenomas and 22 were invasive adenomas.

RESULTS

A positive relationship between high proliferation and invasiveness was observed in invasive pituitary adenomas when compared to their noninvasive counterparts (Ki-67 labeling index - 4.72% versus 1.75%). Decreased expression of APAF-1 was recorded in most of the invasive adenomas with a high proliferation index, while the cathepsin B level was elevated in this group. We have noticed a negative correlation between the low level of APAF-1 and invasiveness (63.63%; P<0.01); at the same time, a positive correlation between cathepsin B expression and invasiveness (59.09%; P<0.01) was found. In all, 81.25% out of the total APAF-1-positive samples were cathepsin B negative (P<0.01); 76.92% out of the total cathepsin B-positive samples were APAF-1-negative (P<0.01). These results were reinforced by an apoptosis protein array examination, which showed inhibition of the extrinsic apoptotic pathway in an invasive pituitary adenoma.

CONCLUSION

A bidirectional-inverted relationship between APAF-1 and cathepsin B expressions was noticed. One might hypothesize that shifting the balance between mediators of cell death could result in changes in tumor behavior.

Mitochondrial division inhibitor-1 induces mitochondrial hyperfusion and sensitizes human cancer cells to TRAIL-induced apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising candidate for cancer treatment, but some cancer cell types are resistant to TRAIL cytotoxicity. Therefore, overcoming this resistance is necessary for effective TRAIL therapy. Mitochondrial morphology is important for the maintenance of cell function and survival, and is regulated by the delicate balance between fission and fusion. However, the role of mitochondrial morphology dynamics in TRAIL-induced apoptosis is unknown. Here we show that mitochondrial division inhibitor-1 (mdivi-1), an inhibitor of dynamin-related protein1 (Drp1), modulates mitochondrial morphology and TRAIL-induced apoptosis in human cancer cells. mdivi-1 treatment (≥12.5 µM) caused dose- and time‑dependent cell death in malignant melanoma, lung cancer and osteosarcoma cells, while sparing normal cells. mdivi-1 also sensitized cancer cells to TRAIL-induced apoptosis. This potentiation of apoptosis occurred through a caspase-depependent mechanism including the mitochondrial and endoplasmic reticulum (ER) stress pathways. Mdivi-1 potentiated mitochondrial oxidative stress, a major cause of mitochondrial and ER stresses, as evidenced by increases in mitochondrial reactive oxygen species levels, mitochondrial mass, and cardiolipin oxidation. Live cell fluorescence imaging using MitoTracker Red CMXRos revealed that Mdivi-1 caused substantial mitochondrial hyperfusion. Moreover, silencing of Drp1 expression also caused mitochondrial hyperfusion and sensitized cancer cells to TRAIL-induced apoptosis. Our results suggest that cancer cells are more vulnerable than normal cells to a perturbation in mitochondrial morphology dynamics and that this higher susceptibility can be exploited to selectively kill cancer cells and sensitize to TRAIL.

Depolarization Controls TRAIL-Sensitization and Tumor-Selective Killing of Cancer Cells: Crosstalk with ROS

Conventional genotoxic anti-cancer drugs target the proliferative advantage of tumor cells over normal cells. This kind of approach lacks the selectivity of treatment to cancer cells, because most of the targeted pathways are essential for the survival of normal cells. As a result, traditional cancer treatments are often limited by undesirable damage to normal cells (side-effects). Ideal anti-cancer drugs are expected to be highly effective against malignant tumor cells with minimal cytotoxicity toward normal cells. Such selective killing can be achieved by targeting pathways essential for the survival of cancer cells, but not normal cells. As cancer cells are characterized by their resistance to apoptosis, selective apoptosis induction is a promising approach for selective killing of cancer cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising tumor-selective anti-cancer drug. However, the congenital and acquired resistance of some cancer cell types, including malignant melanoma cells, currently impedes effective TRAIL therapy, and an innovative approach that can override TRAIL resistance is urgently required. Apoptosis is characterized by cell shrinkage caused by disruption of the maintenance of the normal physiological concentrations of K(+) and Na(+) and intracellular ion homeostasis. The disrupted ion homeostasis leads to depolarization and apoptosis. Recent evidence suggests that depolarization is an early and prerequisite event during TRAIL-induced apoptosis. Moreover, diverse natural products and synthetic chemicals capable of depolarizing the cell membrane exhibit tumor-selective killing and TRAIL-sensitizing effects. Here, we discuss the role of depolarization in selective killing of cancer cells in connection with the emerging concept that oxidative stress is a critical mediator of mitochondrial and endoplasmic reticulum dysfunctions and serves as a tumor-selective target in cancer treatment.