Lysosomal involvement in cell death and cancer

Goose parvovirus and the protein NS1 induce apoptosis through the AIF-mitochondrial pathway in goose embryo fibroblasts

In this study, the effects of Goose parvovirus (GPV) infection as well as the possible role of NS1 protein on apoptosis induction in goose embryo fibroblast (GEF) cells were examined. Flow cytometry analysis and TUNEL assays revealed that GPV infection and NS1 transfection induced significant apoptosis in GEF cells compared to what was observed in mock-infected cells. Interestingly, the increase in the rate of apoptosis detected in GPV-infected GEFs was accompanied by an increased viral load in the cells. In addition, the apoptotic pathway was mediated by apoptosis-inducing factors (AIFs) and internal factors that influence the release of AIFs. The results indicated that the mitochondrial membrane potential was decreased, and AIF expression was increased in the nucleus (P < 0.01). Reactive oxygen species (ROS) increased gradually within 48 h (P < 0.001). Cathepsin D activities were also increased (P < 0.05). The results demonstrated that the AIF-mediated pathway is a new mitochondrial apoptotic pathway and that mitochondrial depolarization, ROS content, and cathepsin D activities are the key factors influencing apoptosis in GEF cells.

Plasmon-enhanced fluorescence correlation spectroscopy for super-localized detection of nanoscale subcellular dynamics

In this report, we investigate plasmon-enhanced imaging fluorescence correlation spectroscopy (p-FCS). p-FCS takes advantage of extreme light confinement by localization at nanogap-based plasmonic nanodimer arrays (PNAs) for enhanced signal-to-noise ratio (SNR) and improved precision by registration with surface plasmon microscopy images. Theoretical results corroborate the enhancement by PNAs in the far-field. Near-field scanning optical microscopy was used to confirm near-field localization experimentally. Experimental confirmation was also conducted with fluorescent nanobeads. The concept was further applied to studying the diffusion dynamics of lysosomes in HEK293T cells stimulated by phorbol 12-myristate 13-acetate treatment. It was found that lysosomes demonstrate stronger super-diffusive behavior with relatively weaker sub-diffusion after stimulation. SNR measured of p-FCS was improved by 9.77 times over conventional FCS. This report is expected to serve as the foundation for an enhanced analytical tool to explore subcellular dynamics.

Reimagining dots and dashes: Visualizing structure and function of organelles for high-content imaging analysis

Organelles are responsible for biochemical and cellular processes that sustain life and their dysfunction causes diseases from cancer to neurodegeneration. While researchers are continuing to appreciate new roles of organelles in disease, the rapid development of specifically targeted fluorescent probes that report on the structure and function of organelles will be critical to accelerate drug discovery. Here, we highlight four organelles that collectively exemplify the progression of phenotypic discovery, starting with mitochondria, where many functional probes have been described, then continuing with lysosomes and Golgi and concluding with nascently described membraneless organelles. We introduce emerging probe designs to explore organelle-specific morphology and dynamics and highlight recent case studies using high-content analysis to stimulate further development of probes and approaches for organellar high-throughput screening.

Autophagy Triggers Tamoxifen Resistance in Human Breast Cancer Cells by Preventing Drug-Induced Lysosomal Damage

Simple Summary

Endocrine therapy with tamoxifen or other endocrine drugs represents the standard treatment for estrogen receptor-positive breast cancer. In spite of effectiveness of this therapy, onset of drug resistance worsens the prognosis of about 30% of patients. Autophagy has recently been proposed as a key player of drug resistance, but the underlying mechanisms are not completely understood. In this research, the authors investigate how autophagy triggers drug resistance in breast cancer cells. The results evidence that tamoxifen affects lysosome integrity, which suggests that this effect may contribute to the anticancer activity of this drug. Activation of autophagy and overexpression of iron-binding proteins synergize in protecting the lysosomal compartment, restraining drug effectiveness in breast cancer cells. According to these results, tamoxifen-resistant cells show an increased autophagic flux and overexpress iron-binding proteins. These findings indicate that screening for the level of iron-binding proteins may help to identify patients at risk for developing drug resistance.

Abstract

Endocrine resistance is a major complication during treatment of estrogen receptor-positive breast cancer. Although autophagy has recently gained increasing consideration among the causative factors, the link between autophagy and endocrine resistance remains elusive. Here, we investigate the autophagy-based mechanisms of tamoxifen resistance in MCF7 cells. Tamoxifen (Tam) triggers autophagy and affects the lysosomal compartment of MCF7 cells, such that activated autophagy supports disposal of tamoxifen-damaged lysosomes by lysophagy. MCF7 cells resistant to 5 µM tamoxifen (MCF7-TamR) have a higher autophagic flux and an enhanced resistance to Tam-induced lysosomal alterations compared to parental cells, which suggests a correlation between the two events. MCF7-TamR cells overexpress messenger RNAs (mRNAs) for metallothionein 2A and ferritin heavy chain, and they are re-sensitized to Tam by inhibition of autophagy. Overexpressing these proteins in parental MCF7 cells protects lysosomes from Tam-induced damage and preserves viability, while inhibiting autophagy abrogates lysosome protection. Consistently, we also demonstrate that other breast cancer cells that overexpress selected mRNAs encoding iron-binding proteins are less sensitive to Tam-induced lysosomal damage when autophagy is activated. Collectively, our data demonstrate that autophagy triggers Tam resistance in breast cancer cells by favoring the lysosomal relocation of overexpressed factors that restrain tamoxifen-induced lysosomal damage.

Overcoming Chemoresistance: Altering pH of Cellular Compartments by Chloroquine and Hydroxychloroquine

Resistance to the anti-cancer effects of chemotherapeutic agents (chemoresistance) is a major issue for people living with cancer and their providers. A diverse set of cellular and inter-organellar signaling changes have been implicated in chemoresistance, but it is still unclear what processes lead to chemoresistance and effective strategies to overcome chemoresistance are lacking. The anti-malaria drugs, chloroquine (CQ) and its derivative hydroxychloroquine (HCQ) are being used for the treatment of various cancers and CQ and HCQ are used in combination with chemotherapeutic drugs to enhance their anti-cancer effects. The widely accepted anti-cancer effect of CQ and HCQ is their ability to inhibit autophagic flux. As diprotic weak bases, CQ and HCQ preferentially accumulate in acidic organelles and neutralize their luminal pH. In addition, CQ and HCQ acidify the cytosolic and extracellular environments; processes implicated in tumorigenesis and cancer. Thus, the anti-cancer effects of CQ and HCQ extend beyond autophagy inhibition. The present review summarizes effects of CQ, HCQ and proton pump inhibitors on pH of various cellular compartments and discuss potential mechanisms underlying their pH-dependent anti-cancer effects. The mechanisms considered here include their ability to de-acidify lysosomes and inhibit autophagosome lysosome fusion, to de-acidify Golgi apparatus and secretory vesicles thus affecting secretion, and to acidify cytoplasm thus disturbing aerobic metabolism. Further, we review the ability of these agents to prevent chemotherapeutic drugs from accumulating in acidic organelles and altering their cytosolic concentrations.

Inhibition of JNK increases the sensitivity of hepatocellular carcinoma cells to lysosomotropic drugs via LAMP2A destabilization

Alteration of lysosomal homeostasis is common in cancer cells, which often feature an enlarged and peripheral distributed lysosomal compartment and the overexpression of cathepsins. These alterations accelerate the production of building blocks for the de novo synthesis of macromolecules and contribute to the degradation of the extracellular matrix, thus contributing to tumor growth and invasion. At the same time, they make lysosomes more fragile and more prone to lysosomal membrane permeabilization, a condition that can cause the release of proteases into the cytosol and the activation of cell death. Therefore, lysosomes represent a weak spot of cancer cells that can be targeted for therapeutic purposes. Here, we identify a novel role of the kinase JNK as keeper of lysosomal stability in hepatocellular carcinoma cells. JNK inhibition reduces the stability of LAMP2A, a lysosomal membrane protein responsible for the stability of the lysosomal membrane, promoting its degradation by the proteasome. LAMP2A decrease enhances the lysosomal damage induced by lysosomotropic agents, ultimately leading to cell death. The effect is cancer-specific, as JNK inhibition does not decrease LAMP2A in non-tumoral liver cells and does not alter their sensitivity to lysosomotropic drugs. Our finding on the new role of JNK as cancer-specific keeper of lysosomal homeostasis lays the ground for future evaluation of the efficacy of the combination of JNK inhibition and lysosomotropic agents as a potential therapeutic strategy in hepatocellular carcinoma.

SUMO pathway, blood coagulation and oxidative stress in SARS-CoV-2 infection

Severe Acute Respiratory Syndrome Corona Virus 2 (SARS CoV-2) is currently an international pandemic causing coronavirus disease 19 (COVID-19). Viral entry requires ACE2 and transmembrane protease serine 2 (TMPRSS2) for membrane fusion or through endosomal pathway. This Study aims to assess transcriptomic changes and differentially expressed genes (DFGs) in COVID-19.

Methods

Transcriptomic data of the publicly available dataset (GSE147507) was quantile normalized and analysed for DFGs, network analysis and pathway analysis.

Results

DFG sets showed that 8 genes (SAE1, AEBP2, ATP1A1, DKK3, MAFF, NUDC, TRAP1, and VAV1) were significantly dysregulated in all studied groups. Functional analysis revealed that negative regulation of glucocorticoid biosynthesis, protein SUMOylation (SAE1), blood coagulation (VAV1) and cellular response to stress were affected by SARS CoV-2 infection. Cell line transduction with ACE2 vector didn't show significant changes in the dysregulated pathways. Also, no significant change was observed in expression levels of ACE2 or TMPRSS2 in response to SARS CoV-2 infection. Further analysis showed dysregulation of several genes in the SUMOylation pathway and blood coagulation process in human and cell lines transcriptome. Also, several Cathepsins proteases were significantly dysregulated in case of SARS CoV-2 infection. Genes related to cellular response to stress such as TRAP-1 and NOX were dysregulated in cases of SARS CoV-2 infection.

Conclusion

Dysregulation in genes of protein SUMOylation, blood coagulation and response to oxidative stress pathways in SARS CoV-2 infection could be critical for disease progression. Drugs acting on SUMO pathway, VAV1, NOX genes could be studied for potential benefit to COVID-19 patients.

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Negative regulation of glucocorticoid biosynthesis was affected by SARS CoV-2.

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Protein SUMOylation was affected by SARS CoV-2 infection.

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Blood coagulation was affected by SARS CoV-2 infection.

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Cellular response to oxidative stress was affected by SARS CoV-2 infection.

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Cathepsins proteases were significantly dysregulated in SARS CoV-2 infection.

Endolysosomal TRPMLs in Cancer

Lysosomes, the degradative endpoints and sophisticated cellular signaling hubs, are emerging as intracellular Ca²⁺ stores that govern multiple cellular processes. Dys-homeostasis of lysosomal Ca²⁺ is intimately associated with a variety of human diseases including cancer. Recent studies have suggested that the Ca²⁺-permeable channels Transient Receptor Potential (TRP) Mucolipins (TRPMLs, TRPML1-3) integrate multiple processes of cell growth, division and metabolism. Dysregulation of TRPMLs activity has been implicated in cancer development. In this review, we provide a summary of the latest development of TRPMLs in cancer. The expression of TRPMLs in cancer, TRPMLs in cancer cell nutrient sensing, TRPMLs-mediated lysosomal exocytosis in cancer development, TRPMLs in TFEB-mediated gene transcription of cancer cells, TRPMLs in bacteria-related cancer development and TRPMLs-regulated antitumor immunity are discussed. We hope to guide readers toward a more in-depth discussion of the importance of lysosomal TRPMLs in cancer progression and other human diseases.

Lysosomes in acute myeloid leukemia: potential therapeutic targets?

Lysosomes, since their discovery, have been primarily known for degrading cellular macromolecules. However, in recent studies, they have begun to emerge as crucial regulators of cell homeostasis. They are at the crossroads of catabolic and anabolic pathways and are intricately involved in cellular trafficking, nutrient signaling, energy metabolism, and immune regulation. Their involvement in such essential cellular functions has renewed clinical interest in targeting the lysosome as a novel way to treat disease, particularly cancer. Acute myeloid leukemia (AML) is an aggressive blood cancer with a low survival probability, particularly in older patients. The genomic landscape of AML has been extensively characterized but few targeted therapies (with the exception of differentiation therapy) can achieve a long-term cure. Therefore, there is an unmet need for less intensive and more tolerable therapeutic interventions. In this review, we will give an overview on the myriad of functions performed by lysosomes and their importance in malignant disease. Furthermore, we will discuss their relevance in hematopoietic cells and different ways to potentially target them in AML.

Dual targeting of tumor cell energy metabolism and lysosomes as an anticancer strategy

To sustain their proliferative and metastatic capacity, tumor cells increase the activity of energy-producing pathways and lysosomal compartment, resorting to autophagolysosomal degradation when nutrients are scarce. Consequently, large fragile lysosomes and enhanced energy metabolism may serve as targets for anticancer therapy. A simultaneous induction of energy stress (by caloric restriction and inhibition of glycolysis, oxidative phosphorylation, Krebs cycle, or amino acid/fatty acid metabolism) and lysosomal stress (by lysosomotropic detergents, vacuolar ATPase inhibitors, or cationic amphiphilic drugs) is an efficient anti-cancer strategy demonstrated in a number of studies. However, the mechanisms of lysosomal/energy stress co-amplification, apart from the protective autophagy inhibition, are poorly understood. We here summarize the established and suggest potential mechanisms and candidates for anticancer therapy based on the dual targeting of lysosomes and energy metabolism.

Repurposing Cationic Amphiphilic Drugs and Derivatives to Engage Lysosomal Cell Death in Cancer Treatment

A major confounding issue in the successful treatment of cancer is the existence of tumor cell populations that resist therapeutic agents and regimens. While tremendous effort has gone into understanding the biochemical mechanisms underlying resistance to each traditional and targeted therapeutic, a broader approach to the problem may emerge from the recognition that existing anti-cancer agents elicit their cytotoxic effects almost exclusively through apoptosis. Considering the myriad mechanisms cancer cells employ to subvert apoptotic death, an attractive alternative approach would leverage programmed necrotic mechanisms to side-step therapeutic resistance to apoptosis-inducing agents. Lysosomal cell death (LCD) is a programmed necrotic cell death mechanism that is engaged upon the compromise of the limiting membrane of the lysosome, a process called lysosomal membrane permeabilization (LMP). The release of lysosomal components into the cytosol upon LMP triggers biochemical cascades that lead to plasma membrane rupture and necrotic cell death. Interestingly, the process of cellular transformation appears to render the limiting lysosomal membranes of tumor cells more fragile than non-transformed cells, offering a potential therapeutic window for drug development. Here we outline the concepts of LMP and LCD, and discuss strategies for the development of agents to engage these processes. Importantly, the potential exists for existing cationic amphiphilic drugs such as antidepressants, antibiotics, antiarrhythmics, and diuretics to be repurposed to engage LCD within therapy-resistant tumor cell populations.

Identification of Prognostic Genes and Pathways in Lung Adenocarcinoma Using a Bayesian Approach

Lung cancer is the leading cause of cancer-associated mortality in the United States and the world. Adenocarcinoma, the most common subtype of lung cancer, is generally diagnosed at the late stage with poor prognosis. In the past, extensive effort has been devoted to elucidating lung cancer pathogenesis and pinpointing genes associated with survival outcomes. As the progression of lung cancer is a complex process that involves coordinated actions of functionally associated genes from cancer-related pathways, there is a growing interest in simultaneous identification of both prognostic pathways and important genes within those pathways. In this study, we analyse The Cancer Genome Atlas lung adenocarcinoma data using a Bayesian approach incorporating the pathway information as well as the interconnections among genes. The top 11 pathways have been found to play significant roles in lung adenocarcinoma prognosis, including pathways in mitogen-activated protein kinase signalling, cytokine-cytokine receptor interaction, and ubiquitin-mediated proteolysis. We have also located key gene signatures such as RELB, MAP4K1, and UBE2C. These results indicate that the Bayesian approach may facilitate discovery of important genes and pathways that are tightly associated with the survival of patients with lung adenocarcinoma.

The role of lysosomes in cancer development and progression

Lysosomes are an important component of the inner membrane system and participate in numerous cell biological processes, such as macromolecular degradation, antigen presentation, intracellular pathogen destruction, plasma membrane repair, exosome release, cell adhesion/migration and apoptosis. Thus, lysosomes play important roles in cellular activity. In addition, previous studies have shown that lysosomes may play important roles in cancer development and progression through the abovementioned biological processes and that the functional status and spatial distribution of lysosomes are closely related to cancer cell proliferation, energy metabolism, invasion and metastasis, immune escape and tumor-associated angiogenesis. Therefore, identifying the factors and mechanisms that regulate the functional status and spatial distribution of lysosomes and elucidating the relationship between lysosomes and the development and progression of cancer can provide important information for cancer diagnosis and prognosis prediction and may yield new therapeutic targets. This study briefly reviews the above information and explores the potential value of lysosomes in cancer therapy.

Organelle-Directed Metabolic Glycan Labeling and Optical Tracking of Dysfunctional Lysosomes Thereof

Metabolic glycan labeling (MGL) has been employed for diverse purposes, such as cell surface glycan imaging and tumor surface engineering. We herein reported organelle-specific MGL (OMGL) for selective tagging of the inner limiting membrane of lysosomes over the cell surface. This is operated via acidity-promoted accumulation of optical probes in lysosomes and bioorthogonal ligation of the trapped probes with 9-azidosialic acid (AzSia) metabolically installed on lysosomal membrane proteins. Overcoming the limitation of classical organelle probes to dissipate from stressed organelles, OMGL enables optical tracking of pH-elevated lysosomes in exocytosis and membrane-permeabilized lysosomes in different cell death pathways. Thus, OMGL offers a new tool to study lysosome biology.

Pullulan based stimuli responsive and sub cellular targeted nanoplatforms for biomedical application: Synthesis, nanoformulations and toxicological perspective

With growing interest in polymers of natural origin, innumerable polysaccharides have gained attention for their biomedical application. Pullulan, one of the FDA approved nutraceuticals, possesses multiple unique properties which make them highly advantageous for biomedical applications. This present review encompasses the sources, production, properties and applications of pullulan. It highlights various pullulan based stimuli-responsive systems (temperature, pH, ultrasound, magnetic), subcellular targeted systems (mitochondria, Golgi apparatus/endoplasmic reticulum, lysosome, endosome), lipid-vesicular systems (solid-lipid nanoparticles, liposomes), polymeric nanofibres, micelles, inorganic (SPIONs, gold and silver nanoparticles), carbon-based nanoplatforms (carbon nanotubes, fullerenes, nanodiamonds) and quantum dots. This article also gives insight into different biomedical, therapeutic and diagnostic applications of pullulan viz., imaging, tumor targeting, stem cell therapy, gene therapy, vaccine delivery, cosmetic applications, protein delivery, tissue engineering, photodynamic therapy and chaperone-like activities. The review also includes the toxicological profile of pullulan which is helpful for the development of suitable delivery systems for clinical applications.

Amphiphilic mannose-6-phosphate glycopolypeptide-based bioactive and responsive self-assembled nanostructures for controlled and targeted lysosomal cargo delivery

Receptors of carbohydrate mannose-6-phosphate (M6P) are overexpressed in specific cancer cells (such as breast cancer) and are also involved in the trafficking of mannose-6-phosphate labeled proteins exclusively onto lysosomes via cell surface M6P receptor (CI-MPR) mediated endocytosis. Herein, for the first time, mannose-6-phosphate glycopolypeptide (^M6PGP)-based bioactive and stimuli-responsive nanocarriers are reported. They are selectively taken up via receptor-mediated endocytosis, and trafficked to lysosomes where they are subsequently degraded by pH or enzymes, leading to the release of the cargo inside the lysosomes. Two different amphiphilic M6P block copolymers ^M6PGP₁₅-^APPO₄₄ and ^M6PGP₁₅-(PCL₂₅)₂ were synthesized by click reaction of the alkyne end-functionalized ^M6PGP₁₅ with pH-responsive biocompatible azide end-functionalized acetal PPO and azide end-functionalized branched PCL, respectively. In water, the amphiphilic M6P-glycopolypeptide block copolymers self-assembled into micellar nanostructures, as was evidenced by DLS, TEM, AFM, and fluorescence spectroscopy techniques. These micellar systems were competent to encapsulate the hydrophobic dye rhodamine-B-octadecyl ester, which was used as the model drug. They were stable at physiological pH but were found to disassemble at acidic pH (for ^M6PGP₁₅-^APPO₄₄) or in the presence of esterase (for ^M6PGP₁₅-(PCL₂₅)₂). These ^M6PGP based micellar nanoparticles can selectively target lysosomes in cancerous cells such as MCF-7 and MDA-MB-231. Finally, we demonstrate the clathrin-mediated endocytic pathway of the native FL-^M6PGP polymer and RBOE loaded ^M6PGP micellar-nanocarriers, and selective trafficking of MCF-7 and MDA-MB-231 breast cancer cell lysosomes, demonstrating their potential applicability toward receptor-mediated lysosomal cargo delivery.

The Intracellular Number of Magnetic Nanoparticles Modulates the Apoptotic Death Pathway after Magnetic Hyperthermia Treatment

Magnetic hyperthermia is a cancer treatment based on the exposure of magnetic nanoparticles to an alternating magnetic field in order to generate local heat. In this work, 3D cell culture models were prepared to observe the effect that a different number of internalized particles had on the mechanisms of cell death triggered upon the magnetic hyperthermia treatment. Macrophages were selected by their high capacity to uptake nanoparticles. Intracellular nanoparticle concentrations up to 7.5 pg Fe/cell were measured both by elemental analysis and magnetic characterization techniques. Cell viability after the magnetic hyperthermia treatment was decreased to <25% for intracellular iron contents above 1 pg per cell. Theoretical calculations of the intracellular thermal effects that occurred during the alternating magnetic field application indicated a very low increase in the global cell temperature. Different apoptotic routes were triggered depending on the number of internalized particles. At low intracellular magnetic nanoparticle amounts (below 1 pg Fe/cell), the intrinsic route was the main mechanism to induce apoptosis, as observed by the high Bax/Bcl-2 mRNA ratio and low caspase-8 activity. In contrast, at higher concentrations of internalized magnetic nanoparticles (1-7.5 pg Fe/cell), the extrinsic route was observed through the increased activity of caspase-8. Nevertheless, both mechanisms may coexist at intermediate iron concentrations. Knowledge on the different mechanisms of cell death triggered after the magnetic hyperthermia treatment is fundamental to understand the biological events activated by this procedure and their role in its effectiveness.

Phosphatidylinositol 3-phosphate and Hsp70 protect Plasmodium falciparum from heat-induced cell death

Phosphatidylinositol 3-phosphate (PI(3)P) levels in Plasmodium falciparum correlate with tolerance to cellular stresses caused by artemisinin and environmental factors. However, PI(3)P function during the Plasmodium stress response was unknown. Here, we used PI3K inhibitors and antimalarial agents to examine the importance of PI(3)P under thermal conditions recapitulating malarial fever. Live cell microscopy using chemical and genetic reporters revealed that PI(3)P stabilizes the digestive vacuole (DV) under heat stress. We demonstrate that heat-induced DV destabilization in PI(3)P-deficient P. falciparum precedes cell death and is reversible after withdrawal of the stress condition and the PI3K inhibitor. A chemoproteomic approach identified PfHsp70-1 as a PI(3)P-binding protein. An Hsp70 inhibitor and knockdown of PfHsp70-1 phenocopy PI(3)P-deficient parasites under heat shock. Furthermore, PfHsp70-1 downregulation hypersensitizes parasites to heat shock and PI3K inhibitors. Our findings underscore a mechanistic link between PI(3)P and PfHsp70-1 and present a novel PI(3)P function in DV stabilization during heat stress.

Barriers and Strategies of Cationic Liposomes for Cancer Gene Therapy

Cationic liposomes (CLs) have been regarded as the most promising gene delivery vectors for decades with the advantages of excellent biodegradability, biocompatibility, and high nucleic acid encapsulation efficiency. However, the clinical use of CLs in cancer gene therapy is limited because of many uncertain factors in vivo. Extracellular barriers such as opsonization, rapid clearance by the reticuloendothelial system and poor tumor penetration, and intracellular barriers, including endosomal/lysosomal entrapped network and restricted diffusion to the nucleus, make CLs not the ideal vector for transferring extrinsic genes in the body. However, the obstacles in achieving productive therapeutic effects of nucleic acids can be addressed by tailoring the properties of CLs, which are influenced by lipid compositions and surface modification. This review focuses on the physiological barriers of CLs against cancer gene therapy and the effects of lipid compositions on governing transfection efficiency, and it briefly discusses the impacts of particle size, membrane charge density, and surface modification on the fate of CLs in vivo, which may provide guidance for their preclinical studies.

Mitochondrial Metabolism, Contact Sites and Cellular Calcium Signaling: Implications for Tumorigenesis

Mitochondria are organelles that are mainly involved in the generation of ATP by cellular respiration. In addition, they modulate several intracellular functions, ranging from cell proliferation and differentiation to cell death. Importantly, mitochondria are social and can interact with other organelles, such as the Endoplasmic Reticulum, lysosomes and peroxisomes. This symbiotic relationship gives advantages to both partners in regulating some of their functions related to several aspects of cell survival, metabolism, sensitivity to cell death and metastasis, which can all finally contribute to tumorigenesis. Moreover, growing evidence indicates that modulation of the length and/or numbers of these contacts, as well as of the distance between the two engaged organelles, impacts both on their function as well as on cellular signaling. In this review, we discuss recent advances in the field of contacts and communication between mitochondria and other intracellular organelles, focusing on how the tuning of mitochondrial function might impact on both the interaction with other organelles as well as on intracellular signaling in cancer development and progression, with a special focus on calcium signaling.

Shift in phagocytosis, lysosomal stability, lysozyme activity, apoptosis and cell cycle profile in the coelomocytes of earthworm of polluted soil near a tannery field of India

Calcutta Leather Complex of the state of West Bengal, India has been designated as an industrially active zone with around 400 active tannery units. This area spanning 4.5 km² is surrounded by human habitation. The soil of this region is contaminated with metal pollutants and exhibited an alteration in selected physicochemical parameters, namely cation exchange capacity, moisture content, pH, total nitrogen, total organic carbon and water holding capacity. Metaphire posthuma, a common variety of endogeic earthworm inhabiting this region is thus continuously exposed to these toxic metals. Coelomocytes, the chief immune effector cells of earthworm presented a shift in phagocytosis, lysosomal membrane stability, lysozyme and phosphatase activity, physiological apoptosis and cell cycle profile of M. posthuma sampled from the soil of tannery industry. Presence of high concentration of toxic metals and change in the physicochemical characteristics of soil led to a state of cellular stress and immunocompromisation in M. posthuma, a common inhabitant of soil of this region. Experimental endpoints bear ecotoxicological significance as biomarkers of physiological stress in earthworm for monitoring the health of soil around this tannery industrial zone.

Potent half-sandwich Ru(Ⅱ) N^N (aryl-BIAN) complexes: Lysosome-mediated apoptosis, in vitro and in vivo anticancer activities

Herein a new series of organometallic half-sandwich Ru(Ⅱ) complexes bearing aryl-BIAN chelating ligands with various electron-withdrawing and electron-donating substituents have been developed as theranostic agents. All the complexes display much higher anti-proliferative potency than the clinical chemotherapeutic drug cisplatin towards seven cancer cell lines. The anti-proliferative efficacy of these complexes is correlated to their electron-withdrawing ability. Interestingly, complex Ru1 also potently suppresses cancer cell migration in vitro and effectively inhibit tumor growth in vivo in a CT26 colon cancer mouse xenograft model. Mechanisms of action studies display that Ru1 can favorably accumulate in lysosome and exerts anti-cancer potency by inducing a series of events related to lysosomal dysfunction in CT26 cells. Interestingly, inhibition of lysosomal enzymes leads to suppression of cytotoxicity and apoptosis induced by Ru1. Our results elucidate that complex Ru1 can elicit cytotoxicity through lysosome-mediated apoptosis in vitro and suppress tumor growth in vivo.

Targeting Lysosomes in Cancer as Promising Strategy to Overcome Chemoresistance-A Mini Review

To date, cancer remains a worldwide leading cause of death, with a still rising incidence. This is essentially caused by the fact, that despite the abundance of therapeutic targets and treatment strategies, insufficient response and multidrug resistance frequently occur. Underlying mechanisms are multifaceted and extensively studied. In recent research, it became evident, that the lysosome is of importance in drug resistance phenotypes. While it has long been considered just as cellular waste bag, it is now widely known that lysosomes play an important role in important cellular signaling processes and are in the focus of cancer research. In that regard lysosomes are now considered as so-called "drug safe-houses" in which chemotherapeutics are trapped passively by diffusion or actively by lysosomal P-glycoprotein activity, which prevents them from reaching their intracellular targets. Furthermore, alterations in lysosome to nucleus signaling by the transcription factor EB (TFEB)-mTORC1 axis are implicated in development of chemoresistance. The identification of lysosomes as essential players in drug resistance has introduced novel strategies to overcome chemoresistance and led to innovate therapeutic approaches. This mini review gives an overview of the current state of research on the role of lysosomes in chemoresistance, summarizing underlying mechanisms and treatment strategies and critically discussing open questions and drawbacks.

Melatonin and alcohol-related disorders

This review concerns the current knowledge of melatonin and alcohol-related disorders. Chronobiological effects of ethanol are related to melatonin suppression and in relation to inflammation, stress, free radical scavenging, autophagy and cancer risk. It is postulated that both alcohol- and inflammation-induced production of reactive oxygen species (ROS) alters cell membrane properties leading to tissue dysfunction and, subsequent further ROS production. Lysosomal enzymes are often used to assess the relationships between intensified inflammation states caused by alcohol abuse and oxidative stress as well as level of tissue damage estimated by the increased release of cellular enzymes into the extracellular space. Studies have established a link between alcoholism and desynchronosis (circadian disruption). Desynchronosis results from the disorganization of the body's circadian time structure and is an aspect of the pathology of chronic alcohol intoxication. The inflammatory conditions and the activity of lysosomal enzymes in acute alcohol poisoning or chronic alcohol-dependent diseases are in most cases interrelated. Inflammation can increase the activity of lysosomal enzymes, which can be regarded as a marker of lysosomal dysfunction and abnormal cellular integrity. Studies show alcohol toxicity is modulated by the melatonin (Mel) circadian rhythm. This hormone, produced by the pineal gland, is the main regulator of 24 h (sleep-wake cycle) and seasonal biorhythms. Mel exhibits antioxidant properties and may be useful in the prevention of oxidative stress reactions known to be responsible for alcohol-related diseases. Naturally produced Mel and exogenous sources in food can act in free radical reactions and activate the endogenous defense system. Mel plays an important role in the normalization of the post-stress state by its influence on neurotransmitter systems and the synchronization of circadian rhythms. Acting simultaneously on the neuroendocrine and immune systems, Mel optimizes homeostasis and provides protection against stress. Abbreviations: ROS, reactive oxygen species; Mel, melatonin; SRV, resveratrol; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; ANT, arylalkylamine-N-acetyltransferase; EC cells, gastrointestinal enterochromaffin cells; MT1, melatonin high-affinity nanomolecular receptor site; MT2, melatonin low-affinity nanomolecular receptor site; ROR/RZR, orphan nuclear retinoid receptors; SOD, superoxide dismutase; CAT, catalase; GPx, glutathione peroxidase; GR, glutathione reductase; GSH, reduced form of glutathione; GSSG, oxidized form of glutathione; TAC, total antioxidant capacity; ONOO∙^-, peroxynitrite radical; NCAM, neural cell adhesion molecules; LPO, lipid peroxidation; α-KG, α-ketoglutarate, HIF-1α, Hypoxia-inducible factor 1-α, IL-2, interleukin-2; HPA axis, hypothalamic-pituitary-adrenal axis; Tph1, tryptophan hydroxylase 1; AA-NAT, arylalkylamine-N-acetyltransferase; AS-MT, acetylserotonin O-methyltransferase; NAG, N-acetyl-beta-D-glucosaminidase; HBA1c glycated hemoglobin; LPS, lipopolysaccharide; AAP, alanyl-aminopeptidase; β-GR, β-glucuronidase; β-GD, β-galactosidase; LAP, leucine aminopeptidase.

Intracellular cathepsin C levels determine sensitivity of cells to leucyl-leucine methyl ester-triggered apoptosis

L-leucyl-leucine methyl ester (LLOMe) is a lysosomotropic detergent, which was evaluated in clinical trials in graft-vs-host disease because it very efficiently killed monocytic cell lines. It was also shown to efficiently trigger apoptosis in cancer cells, suggesting that the drug might have potential in anticancer therapy. Using U-937 and THP-1 promonocytes as models for monocytic cells, U-87-MG and HeLa cells as models for cancer cells, and noncancerous HEK293 cells, we show that the drug triggers rapid cathepsin C-dependent lysosomal membrane permeabilization, followed by the release of other cysteine cathepsins into the cytosol and subsequent apoptosis. However, monocytes were found to be far more sensitive to the drug than the cancer and noncancer cells, which is most likely a consequence of the much higher intracellular levels of cathepsin C-the most upstream molecule in the pathway-in monocytic cell lines as compared to cancer cells. Overexpression of cathepsin C in HEK293 cells substantially enhances their sensitivity to the drug, consistent with the crucial role of cathepsin C. Major involvement of cysteine cathepsins B, S, and L in the downstream signaling pathway to mitochondrial cell death was confirmed in two gene ablation models, including the ablation of the major cytosolic inhibitor of cysteine cathepsins, stefin B, in primary mouse cancer cells, and simultaneous ablation of two major cathepsins, B and L, in mouse embryonic fibroblasts (MEFs). Deletion of stefin B resulted in sensitizing primary murine breast cancer cells to cell death without affecting the release of cathepsins, whereas simultaneous ablation of cathepsins B and L largely protected MEFs against cell death. However, due to the extreme sensitivity of monocytes to LLOMe, it appears that the drug may not be suitable for anticancer therapy due to risk of systemic toxicity.

Interactions of the Lysosomotropic Detergent O-Methyl-Serine Dodecylamide Hydrochloride (MSDH) with Lipid Bilayer Membranes-Implications for Cell Toxicity

O-methyl-serine dodecylamine hydrochloride (MSDH) is a detergent that accumulates selectively in lysosomes, a so-called lysosomotropic detergent, with unexpected chemical properties. At physiological pH, it spontaneously forms vesicles, which disassemble into small aggregates (probably micelles) below pH 6.4. In this study, we characterize the interaction between MSDH and liposomes at different pH and correlate the findings to toxicity in human fibroblasts. We find that the effect of MSDH on lipid membranes is highly pH-dependent. At neutral pH, the partitioning of MSDH into the liposome membrane is immediate and causes the leakage of small fluorophores, unless the ratio between MSDH and lipids is kept low. At pH 5, the partitioning of MSDH into the membrane is kinetically impeded since MSDH is charged and a high ratio between MSDH and the lipids is required to permeabilize the membrane. When transferred to cell culture conditions, the ratio between MSDH and plasma membrane lipids must therefore be low, at physiological pH, to maintain plasma membrane integrity. Transmission electron microscopy suggests that MSDH vesicles are taken up by endocytosis. As the pH of the endosomal compartment progressively drops, MSDH vesicles disassemble, leading to a high concentration of increasingly charged MSDH in small aggregates inside the lysosomes. At sufficiently high MSDH concentrations, the lysosome is permeabilized, the proteolytic content released to the cytosol and apoptotic cell death is induced.

Naringin Induces Lysosomal Permeabilization and Autophagy Cell Death in AGS Gastric Cancer Cells

Autophagy is a process of active programmed cell death, where a dying cell induces autophagosomes and subsequently regulated by degradative machinery. The aim of this study was to investigate the mechanism behind induction of autophagic cell death by Naringin flavonoid in AGS cancer cells. Growth inhibition of AGS cells showed downregulation of PI3K/Akt/mTOR signaling by Naringin treatment. Transmission electron microscopy observation showed swollen mitochondria and lysosome near peri-nuclear zone fused with autophagic vacuoles. Rapamycin pre-treatment with Naringin showed significant decrease in mTOR phosphorylation and increase in LC3B activation in AGS cells. Decrease in mTOR phosphorylation is associated with lysosomal function activation was observed by time-dependent treatment of Naringin. Induction of lysosomal membrane permeabilization (LMP) was observed by LAMP1 activation leading lysosomal cell death by releasing Cathepsin D from lysosomal lumen to cytosol. Naringin treated AGS cells showed up-regulating BH3 domain Bad, down-regulating Bcl-xL, and Bad phosphorylation and significant mitochondrial fluorescence intensity expression. Significant localization of mitochondria and LC3B activation was examined by person coefficient correlation. Activation of ERK1/2-p38 MAPKs and production of intracellular ROS has been observed over Naringin treatment. It has also been elucidated that pre-treatment with NAC inhibited mitochondria-LC3B colocalization, where ROS acted as upstream of ERK1/2-p38 MAPKs activation. Lysosomal cell death involvement has been evaluated by BAF A1 pre-treatment, inhibiting LAMP1, Cathepsin D, ROS, and blocking autophagolysosome in AGS cell death. Taken together, these findings show that, Naringin induced autophagy cell death involves LMP mediated lysosomal damage and BH3 protein Bad activation in AGS cancer cells.

Quercetin Triggers Induction of Apoptotic and Lysosomal Death of Sensitive and Multidrug Resistant Leukaemia HL60 Cells

Multidrug resistance (MDR) constitutes the major cause of the failure in anticancer therapy. One of the most important mechanisms leading to the occurrence of MDR is related to the modulation of cellular death pathways. The aim of this study was to determine the effect of quercetin (Q) on triggering the programed death of human promyelocytic leukemia sensitive cells HL60 as well as multidrug resistant HL60/VINC cells overexpressing P-glycoprotein and HL60/MX2 cells characterized by the presence of mutated α isoform of topoisomerase II and the absence of β isoform of this enzyme. Q exerted comparable cytotoxic activities toward sensitive HL60 cells and their MDR counterparts. It was also found that this compound modulated the cellular level of reactive oxygen species (ROS) and led to the marked decrease in cellular GSH level. Furthermore, it was demonstrated that Q used at IC₅₀ and IC₉₀ significantly increased the percentage of sub-G1 subpopulation of all studied leukemia cells causing oligonucleosomal DNA fragmentation. The present study also indicated that Q used at IC₉₀ triggers predominantly programed cell death of sensitive HL60 cells and their MDR counterparts by induction of apoptosis occurring with the involvement of caspase-3 and caspase-8 as well as by lysosome membrane permeabilization-dependent mechanisms.

Vulnerability of invasive glioblastoma cells to lysosomal membrane destabilization

The current clinical care of glioblastomas leaves behind invasive, radio‐ and chemo‐resistant cells. We recently identified mammary‐derived growth inhibitor (MDGI/FABP3) as a biomarker for invasive gliomas. Here, we demonstrate a novel function for MDGI in the maintenance of lysosomal membrane integrity, thus rendering invasive glioma cells unexpectedly vulnerable to lysosomal membrane destabilization. MDGI silencing impaired trafficking of polyunsaturated fatty acids into cells resulting in significant alterations in the lipid composition of lysosomal membranes, and subsequent death of the patient‐derived glioma cells via lysosomal membrane permeabilization (LMP). In a preclinical model, treatment of glioma‐bearing mice with an antihistaminergic LMP‐inducing drug efficiently eradicated invasive glioma cells and secondary tumours within the brain. This unexpected fragility of the aggressive infiltrating cells to LMP provides new opportunities for clinical interventions, such as re‐positioning of an established antihistamine drug, to eradicate the inoperable, invasive, and chemo‐resistant glioma cells from sustaining disease progression and recurrence.

Targeted crystallization of mixed-charge nanoparticles in lysosomes induces selective death of cancer cells

Lysosomes have become an important target for anticancer therapeutics because lysosomal cell death bypasses the classical caspase-dependent apoptosis pathway, enabling the targeting of apoptosis- and drug-resistant cancers. However, only a few small molecules-mostly repurposed drugs-have been tested so far, and these typically exhibit low cancer selectivity, making them suitable only for combination therapies. Here, we show that mixed-charge nanoparticles covered with certain ratios of positively and negatively charged ligands can selectively target lysosomes in cancerous cells while exhibiting only marginal cytotoxicity towards normal cells. This selectivity results from distinct pH-dependent aggregation events, starting from the formation of small, endocytosis-prone clusters at cell surfaces and ending with the formation of large and well-ordered nanoparticle assemblies and crystals inside cancer lysosomes. These assemblies cannot be cleared by exocytosis and cause lysosome swelling, which gradually disrupts the integrity of lysosomal membranes, ultimately impairing lysosomal functions and triggering cell death.

Dual-Targeted Phototherapeutic Agents as Magic Bullets for Cancer

Imagine the ideal cancer drug that only kills cancer cells and does not affect nearby noncancerous cells. In the words of Paul Ehrlich, the drug acts like a magic bullet. This Topical Review summarizes an emerging new strategy to achieve this audacious goal. The central concept is a dual-targeted phototherapeutic agent for photodynamic or photothermal therapy. The dual-targeted phototherapeutic agent promotes cancer cell specificity by leveraging three levels of selectivity. Cell death will only occur in the anatomical location that is illuminated with light (Selectivity Level 1) and in cancer cells within the illumination area that have selectively accumulated the agent (Selectivity Level 2). The cancer cell killing effect is highly localized if the agent accumulates in hypersensitive intracellular organelles (Selectivity Level 3). The common targeting units for cancer cells and organelles are described, along with recent examples of dual-targeted phototherapeutic agents that incorporate these two classes of targeting units.

The role of TFEB in tumor cell autophagy: Diagnostic and therapeutic opportunities

Autophagy is a conserved "self-eating" recycling process which removes aggregated or misfolded proteins, or defective organelles, to maintain cellular hemostasis. In the autophagy-lysosome pathway (ALP), clearance of unwanted debris and materials occurs through the generation of the autophagosome, a complex of double-membrane bounded vesicles that form around cytosolic cargos and catabolize their contents by fusion to lysosomes. In tumors, autophagy has dichotomous functions via preventing tumor initiation but promoting tumor progression. The basic helix-loop-helix leucine zipper transcription factor EB (TFEB) activates the promoters of genes encoding for proteins, which participate in this cellular degradative system by regulating lysosomal biogenesis, lysosomal acidification, lysosomal exocytosis and autophagy. In humans, disturbances of ALP are related to various pathological conditions. Recently, TFEB dysregulation was found to have a crucial pathogenic role in different tumors by modulating tumor cell autophagy. Notably, in renal cell carcinomas, different TFEB gene fusions were reported to promote oncogenic features. In this review, we discuss the role of TFEB in human cancers with a special focus on potential diagnostic and therapeutic implications.

Aggregatibacter actinomycetemcomitans LtxA Hijacks Endocytic Trafficking Pathways in Human Lymphocytes

Leukotoxin (LtxA), from oral pathogen Aggregatibacter actinomycetemcomitans, is a secreted membrane-damaging protein. LtxA is internalized by β2 integrin LFA-1 (CD11a/CD18)-expressing leukocytes and ultimately causes cell death; however, toxin localization in the host cell is poorly understood and these studies fill this void. We investigated LtxA trafficking using multi-fluor confocal imaging, flow cytometry and Rab5a knockdown in human T lymphocyte Jurkat cells. Planar lipid bilayers were used to characterize LtxA pore-forming activity at different pHs. Our results demonstrate that the LtxA/LFA-1 complex gains access to the cytosol of Jurkat cells without evidence of plasma membrane damage, utilizing dynamin-dependent and presumably clathrin-independent mechanisms. Upon internalization, LtxA follows the LFA-1 endocytic trafficking pathways, as identified by co-localization experiments with endosomal and lysosomal markers (Rab5, Rab11A, Rab7, and Lamp1) and CD11a. Knockdown of Rab5a resulted in the loss of susceptibility of Jurkat cells to LtxA cytotoxicity, suggesting that late events of LtxA endocytic trafficking are required for toxicity. Toxin trafficking via the degradative endocytic pathway may culminate in the delivery of the protein to lysosomes or its accumulation in Rab11A-dependent recycling endosomes. The ability of LtxA to form pores at acidic pH may result in permeabilization of the endosomal and lysosomal membranes.

DOX-loaded peptide dendritic copolymer nanoparticles for combating multidrug resistance by regulating the lysosomal pathway of apoptosis in breast cancer cells

Multidrug resistance (MDR) is a common phenomenon in clinical oncology and is a major obstacle to cancer chemotherapy. Many nanoparticle (NP)-based drug delivery systems have been developed to overcome MDR depending on increasing intracellular drug concentrations via increased cellular uptake and rapid drug release. The objective of this work was to investigate the performance and possible mechanisms of enzyme-sensitive mPEGylated dendron-GFLG-DOX conjugate based nanoparticles for blockading the MDR phenotype of MCF-7/ADR. In vitro, mPEGylated dendron-GFLG-DOX conjugate based nanoparticles could significantly promote cellular uptake and accumulation, potent cytotoxicity and apoptosis compared to free DOX in resistant cells. mPEGylated dendron-GFLG-DOX conjugate based nanoparticles were found to translocate across the membranes of resistant cells via active endocytic pathways leading to more DOX accumulating in the nuclei of MCF-7/ADR cells. Importantly, we found that mPEGylated dendron-GFLG-DOX conjugate based nanoparticles could induce cathepsin B in the cytoplasm and enhance lysosomal-mediated cell death compared to free DOX. Furthermore, mPEGylated dendron-GFLG-DOX conjugate based nanoparticles enhanced the drug's penetration, toxicity, and growth inhibition compared to free DOX in the three-dimensional multicellular tumor spheroid model. In vivo, mPEGylated dendron-GFLG-DOX conjugate based nanoparticles significantly improved the therapeutic efficacy against MDR xenograft tumors, and showed better biocompatibility than free DOX. These results indicated that mPEGylated dendron-GFLG-DOX conjugate based nanoparticles could be used as an alternative drug delivery system for MDR tumor treatment through initiating the lysosomal apoptosis pathway.

Lysosome as the Black Hole for Checkpoint Molecules

Lysosomes, as digestive organelles full of hydrolases, have complex functions and play an important role in cellular physiological and pathological processes. In normal physiological conditions, lysosomes can sense the nutritional state and be responsible for recycling raw materials to provide nutrients, affecting cell signaling pathways and regulating cell proliferation. Lysosomes are related to many diseases and associated with metastasis and drug resistance of tumors. In recent years, much attention has been paid to the tumor immunotherapy especially immune checkpoint blockade therapy. Accumulating data suggest that lysosomes may serve as a major destruction for immune checkpoint molecules, and secretory lysosomes can temporarily store immune checkpoint proteins. Once activated, the compounds contained in secretory lysosomes are released to the surface of cell membrane rapidly. Inhibitions of lysosomes can overcome the chemoresistance of some tumors and enhance the efficacy of immunotherapy.

Development of Activity-Based Reporter Gene Technology for Imaging of Protease Activity with an Exquisite Specificity in a Single Live Cell

Imaging of an active protease with an exquisite specificity in the presence of highly homologous proteins within a living cell is a very challenging task. Herein, we disclose a new method called "Activity-based Reporter Gene Technology" (AbRGT). This method provides an opportunity to study the function of "active protease" with an unprecedented specificity. As a proof-of-concept, we have applied this method to study the function of individual caspase protease in both intrinsic and extrinsic apoptosis signaling pathways. The versatility of this method is demonstrated by studying the function of both the initiator and effector caspases, independently. The modular fashion of this technology provides the opportunity to noninvasively image the function of cathepsin-B in a caspase-dependent cell death pathway. As a potential application, this method is used as a tool to screen compounds that are potent inhibitors of caspases and cathepsin-B proteases. The fact that this method can be readily applied to any protease of interest opens up huge opportunities for this technology in the area of target validation, high-throughput screening, in vivo imaging, diagnostics, and therapeutic intervention.

Lysosome imaging in cancer cells by pyrene-benzothiazolium dyes: An alternative imaging approach for LAMP-1 expression based visualization methods to avoid background interference

A series of pyrene-benzothiazolium dyes (1a-1d) were experimentally investigated to study their internalization mechanism into cellular lysosomes as well as their potential imaging applications for live cell imaging. The lysosome selectivity of the probes was further compared by using fluorescently tagged lysosome associated membrane protein-1 (LAMP-1) expression-dependent visualization in both normal (COS-7, HEK293) and cancer (A549, Huh 7.5) cell lines. These probes were successfully employed as reliable lysosome markers in tumor cell models, thus providing an attractive alternative to LAMP-1 expression-dependent visualization methods. One advantage of these probes is the elimination of significant background fluorescence arising from fluorescently tagged protein expression on the cell surface when cells were transfected with LAMP-1 expression plasmids. Probes exhibited remarkable ability to stain cellular lysosomes for long-term experiments (up to 24 h) and the highly lipophilic nature of the probe design allowed their accumulation in hydrophobic regions of the cellular lysosomes. Experimental evidences indicated that the probes are likely to be internalized into lysosomes via endocytosis and accumulated in the hydrophobic regions of the lysosomes rather than in the acidic lysosomal lumen. These probes also demonstrated significant stability and lysosome staining for fixed cell imaging applications as well. Lastly, the benzothiazolium moiety of the probes was identified as the key component for lysosome selectivity.

Therapeutic targeting of the PI4K2A/PKR lysosome network is critical for misfolded protein clearance and survival in cancer cells

The role of RNA-dependent protein kinase R (PKR) and its association with misfolded protein expression in cancer cells are unclear. Herein we report that PKR regulates misfolded protein clearance by preventing it release through exosomes and promoting lysosomal degradation of misfolded prion proteins in cancer cells. We demonstrated that PKR contributes to the lysosome function and regulates misfolded prion protein clearance. We hypothesized that PKR-associated lysosome function is critical for cancer but not normal cell survival, representing an effective approach for highly targeted cancer therapy. In screening a compound library, we identified two PKR-associated compounds 1 and 2 (Pac 1 and 2) did not affect normal cells but selectively induced cell death in cancer cells depending on their PKR expression status. Pac 1 significantly inhibited the growth of human lung and breast xenograft tumors in mice with no toxicity. Pac 1 binds to PI4K2A and disrupts the PKR/PI4K2A-associated lysosome complex, contributing to destabilization of cancer cell lysosomes and triggering cell death. We observed that PKR and PI4K2A play significant prognostic roles in breast cancer patients. These results demonstrate that targeting of a PI4K2A/PKR lysosome complex may be an effective approach for cancer therapy.

Cold Atmospheric Plasma induces accumulation of lysosomes and caspase-independent cell death in U373MG glioblastoma multiforme cells

Room temperature Cold Atmospheric Plasma (CAP) has shown promising efficacy for the treatment of cancer but the exact mechanisms of action remain unclear. Both apoptosis and necrosis have been implicated as the mode of cell death in various cancer cells. We have previously demonstrated a caspase-independent mechanism of cell death in p53-mutated glioblastoma multiforme (GBM) cells exposed to plasma. The purpose of this study was to elucidate the molecular mechanisms involved in caspase-independent cell death induced by plasma treatment. We demonstrate that plasma induces rapid cell death in GBM cells, independent of caspases. Accumulation of vesicles was observed in plasma treated cells that stained positive with acridine orange. Western immunoblotting confirmed that autophagy is not activated following plasma treatment. Acridine orange intensity correlates closely with the lysosomal marker Lyso TrackerTM Deep Red. Further investigation using isosurface visualisation of confocal imaging confirmed that lysosomal accumulation occurs in plasma treated cells. The accumulation of lysosomes was associated with concomitant cell death following plasma treatment. In conclusion, we observed rapid accumulation of acidic vesicles and cell death following CAP treatment in GBM cells. We found no evidence that either apoptosis or autophagy, however, determined that a rapid accumulation of late stage endosomes/lysosomes precedes membrane permeabilisation, mitochondrial membrane depolarisation and caspase independent cell death.

Dual lysosomal-mitochondrial targeting by antihistamines to eradicate leukaemic cells

Background

Despite great efforts to identify druggable molecular targets for AML, there remains an unmet need for more effective therapies.

Methods

An in silico screening was performed using Connectivity Maps to identify FDA-approved drugs that may revert an early leukaemic transformation gene signature. Hit compounds were validated in AML cell lines. Cytotoxic effects were assessed both in primary AML patient samples and healthy donor blood cells. Xenotransplantation assays were undertaken to determine the effect on engraftment of hit compounds. The mechanism of action responsible for the antileukaemic effect was studied focussing on lysosomes and mitochondria.

Findings

We identified a group of antihistamines (termed ANHAs) with distinct physicochemical properties associated with their cationic-amphiphilic nature, that selectively killed leukaemic cells. ANHAs behaved as antileukaemic agents against primary AML samples ex vivo, sparing healthy cells. Moreover, ANHAs severely impaired the in vivo leukaemia regeneration capacity. ANHAs' cytotoxicity relied on simultaneous mitochondrial and lysosomal disruption and induction of autophagy and apoptosis. The pharmacological effect was exerted based on their physicochemical properties that permitted the passive targeting of both organelles, without the involvement of active molecular recognition.

Interpretation

Dual targeting of lysosomes and mitochondria constitutes a new promising therapeutic approach for leukaemia treatment, supporting the further clinical development.

Fund

This work was funded by the Fundación Mutua Madrileña (RMR), CaixaImpulse (RMR), the Spanish Ministry of Economy (RMR), the Josep Carreras International Leukaemia Foundation (RMR), l'Obra Social “La Caixa” (RMR), and Generalitat de Catalunya (IJC).

The Role of Cysteine Cathepsins in Cancer Progression and Drug Resistance

Cysteine cathepsins are lysosomal enzymes belonging to the papain family. Their expression is misregulated in a wide variety of tumors, and ample data prove their involvement in cancer progression, angiogenesis, metastasis, and in the occurrence of drug resistance. However, while their overexpression is usually associated with highly aggressive tumor phenotypes, their mechanistic role in cancer progression is still to be determined to develop new therapeutic strategies. In this review, we highlight the literature related to the role of the cysteine cathepsins in cancer biology, with particular emphasis on their input into tumor biology.

Inhibition of Lung Cancer by 2-Methoxy-6-Acetyl-7-Methyljuglone Through Induction of Necroptosis by Targeting Receptor-Interacting Protein 1

Aims: Most chemotherapeutic agents exploit apoptotic signaling to trigger cancer cell death, which frequently results in drug resistance. Necroptosis, a nonapoptotic form of regulated cell death, offers an alternative strategy to eradicate apoptosis-resistant cancer cells. We previously reported a natural necroptosis inducer 2-methoxy-6-acetyl-7-methyljuglone (MAM) in A549 lung cancer cells. The current study is designed to investigate the detailed necroptotic signaling and its cytotoxicity on drug-resistant cancer cells. Furthermore, in vivo anticancer effects were also evaluated in nude mice model. Results: MAM directly targets receptor-interacting protein 1 (RIP1) kinase in A549 and H1299 cells, which is responsible for reactive oxygen species (ROS, mainly hydrogen peroxide) generation. A positive feedback loop between calcium (Ca²⁺) and c-Jun N-terminal kinase (JNK) occurred following ROS generation, leading to lysosomal membrane permeabilization and mitochondrial dysfunction. MAM showed similar cytotoxic potency toward cisplatin-resistant A549 (A549/Cis) cells by inducing necroptosis as confirmed by the protective effect of 7-Cl-O-Nec-1 (Nec-1s) and by the morphological characteristics obtained via transmission electron microscopy. Interestingly, tumor necrosis factor alpha (TNFα) was not involved in this process. Intraperitoneal injection of MAM significantly suppressed tumor growth in A549 tumor xenograft without significant body weight loss and multiorgan toxicities. Innovation and Conclusion: Our findings demonstrate that MAM induces necroptosis in A549 and H1299 lung cancer cells by targeting RIP1 kinase and ROS in a TNFα-independent manner. MAM kills A549/Cis cells with similar potency through induction of necroptosis. MAM shows anticancer effect in animal model. The present study raises the therapeutic possibility and strategy to combat cancer by the induction of necroptosis.

Genetic Aberrations Associated with Photodynamic Therapy in Colorectal Cancer Cells

Photodynamic therapy (PDT) is a cancer treatment modality that utilizes three components: light (λ 650-750 nm), a photosensitizer (PS) and molecular oxygen, which upon activation renders the modality effective. Colorectal cancer has one of the highest incident rates as well as a high mortality rate worldwide. In this study, a zinc (Zn) metal-based phthalocyanine (ZnPcSmix) PS was used to determine its efficacy for the treatment of colon adenocarcinoma cells (DLD-1 and Caco-2). Photoactivation of the PS was achieved by laser irradiation at a wavelength of 680 nm. Dose responses were performed to establish optimal PS concentration and irradiation fluence. A working combination of 20 µM ZnPcSmix and 5 J/cm² was used. Biochemical responses were determined after 1 or 24 h incubation post-treatment. Since ZnPcSmix is localized in lysosomes and mitochondria, mitochondrial destabilization analysis was performed monitoring mitochondrial membrane potential (MMP). Cytosolic acidification was determined measuring hydrogen peroxide (H₂O₂) levels in the cytoplasm. Having established apoptotic cell death induction, an apoptosis PCR array was performed to establish the apoptotic mechanism. In DLD-1 cells, expression of genes included 3 up-regulated and 20 down-regulated genes while in Caco-2 cells, there were 16 up-regulated and 22 down-regulated genes. In both cell lines, in up-regulated genes, there was a combination of pro- and anti-apoptotic genes that were significantly expressed. Gene expression results showed that more tumorigenic cells (DLD-1) went through apoptosis; however, they exhibit increased risk of resistance and recurrence, while less tumorigenic Caco-2 cells responded better to PDT, thus being suggestive of a better prognosis post-PDT treatment. In addition, the possible apoptotic mechanisms of cell death were deduced based on the genetic expression profiling of regulatory apoptotic inducing factors.

Synthesis, purification, and anticancer effect of magnetic Fe3O4-loaded poly (lactic-co-glycolic) nanoparticles of the natural drug tetrandrine

Here, we have successfully synthesised and purified multifunctional PLGA-based nanoparticles by the co-encapsulation of an anticancer drug (tetrandrine) and a magnetic material (Fe₃O₄). The obtained Tet-Fe₃O₄-PLGA NPs had a uniform spherical shape with a particle size of approximately 199 nm and a negative surface charge of -18.0 mV, displaying a high encapsulation efficiency. Furthermore, TEM studies provided representative images of the purification process of the magnetic nanoparticles with MACS^® technology. The MFM and VSM results indicated that both the Fe₃O₄ NPs and Tet-Fe₃O₄-PLGA NPs were superparamagnetic. The DSC spectrum demonstrated that Tet was successfully encapsulated within the PLGA-based nanoparticles. Significantly, the release studies revealed NPs had a relatively slower release rate than free Tet after 8 h's initial burst release, which had decreased from 98% to 65% after 24 h. In vitro cellular studies revealed that NPs could effectively penetrate into A549 cells and A549 multicellular spheroids to exert cytotoxicity, displaying a significantly high anti-proliferation effect. Moreover, western blot demonstrated that the co-loaded NPs had a higher anticancer activity by injuring lysosomes to activate the mitochondria pathway and induce A549 cell apoptosis. The magnetic characteristics and high anticancer activity support the use of Tet/Fe₃O₄ co-loaded PLGA-based nanoparticles as a promising strategy in the treatment of lung cancer.

'Patchiness' and basic cancer research: unravelling the proteases

The recent developments in Cathepsin protease research have unveiled a number of key observations which are fundamental to further our understanding of normal cellular homeostasis and disease. By far, the most interesting and promising area of Cathepsin biology stems from how these proteins are linked to the fate of living cells through the phenomenon of Lysosomal Leakage and Lysosomal Membrane Permeabilisation. While extracellular Cathepsins are generally believed to be of central importance in tumour progression, through their ability to modulate the architecture of the Extracellular Matrix, intracellular Cathepsins have been established as being of extreme significance in mediating cell death through Apoptosis. With these two juxtaposed key research areas in mind, the focus of this review highlights recent advancements in how this fast-paced area of Cathepsin research has recently evolved in the context of their mechanistic regulation in cancer research. Abbreviations : ECM, Extracellular Matrix; MMP, Matrix Metalloproteases; LL, Lysosomal Leakage; LMP, Lysosomal Membrane Permeabilisation; LMA, Lysosomorphic Agents; BC, Breast Cancer; ASM, Acid Sphingomyelinase; TNF-α, Tumor Necrosis Factor-alpha; LAMP, Lysosomal Associated membrane Protein; PCD, Programmed Cell Death; PDAC, Pancreatic Ductal Adenocarcinoma; ROS, Reactive Oxygen Species; aa, amino acids.

Dynamic Model of Protease State and Inhibitor Trafficking to Predict Protease Activity in Breast Cancer Cells

Introduction

Cysteine cathepsins are implicated in breast cancer progression, produced by both transformed epithelial cells and infiltrated stromal cells in tumors, but to date, no cathepsin inhibitor has been approved for clinical use due to unexpected side effects. This study explores cellular feedback to cathepsin inhibitors that might yield non-intuitive responses, and uses computational models to determine underlying cathepsin-inhibitor dynamics.

Methods

MDA-MB-231 cells treated with E64 were tested by multiplex cathepsin zymography and immunoblotting to quantify total, active, and inactive cathepsins S and L. This data was used to parameterize mathematical models of intracellular free and inhibited cathepsins, and then applied to a dynamic model predicting cathepsin responses to other classes of cathepsin inhibitors that have also failed clinical trials.

Results

E64 treated cells exhibited increased amounts of active cathepsin S and reduced amount of active cathepsin L, although E64 binds tightly to both. This inhibitor response was not unique to cancer cells or any one cell type, suggesting an underlying fundamental mechanism of E64 preserving activity of cathepsin S, but not cathepsin L. Computational models were able to predict and differentiate between inhibitor-bound, active, and inactive cathepsin species and demonstrate how different classes of cathepsin inhibitors can have drastically divergent effects on active cathepsins located in different intracellular compartments.

Conclusions

Together, this work has important implications for the development of mathematical model systems for protease inhibition in tissue destructive diseases, and consideration of preservation mechanisms by inhibitors that could alter perceived benefits of these treatment modalities.

Effects of Lysosomal-Mitochondrial Apoptotic Pathway on Tenderness in Post-Mortem Bovine Longissimus Muscle

The objective of this study was to investigate the mechanism underlying lysosome-mediated apoptosis, the cross-talk between the lysosomes and mitochondria, and the effect of the pathway on bovine longissimus muscle tenderness during 7 d post-mortem aging through the observation and analysis of longissimus dorsi (LD) muscles of six crossbred cattle. Results showed that an elevated reactive oxygen species level ( P < 0.05) can damage lysosomal membrane stability ( P < 0.05) through accumulating redox-active iron of bovine muscle during post-mortem aging. In addition, the activities of cathepsins B and D increased with post-mortem aging ( P < 0.05). Moreover, cathepsin B and D activated Bid and Bax in the mitochondria ( P < 0.05). Activated Bid and Bax triggered mitochondrial membrane permeability ( P < 0.05) and further activated caspase-9 and caspase-3 ( P < 0.05), leading to apoptosis. Ultimately, the tenderness of bovine muscle was improved during post-mortem aging ( P < 0.05). Importantly, cathepsin D plays a crucial role in the lysosomal-mitochondrial apoptotic pathway and tenderness in post-mortem muscle. These findings provide new insights into the apoptotic pathway of bovine muscle during post-mortem aging.

Red-emitting pyrene-benzothiazolium: unexpected selectivity to lysosomes for real-time cell imaging without alkalinizing effect

A series of pyrene-benzothiazolium probes were synthesized. By replacing the pyridinium with a benzothiazolium unit, the selectivity of pyrene-derivatives is found to switch from nuclear to cellular lysosomes. New probes do not require proton participation and exhibit high biocompatibility and long-term imaging ability.