Mitochondrial Dysfunction at the Center of Cancer Therapy

PBI-05204, a supercritical CO2 extract of Nerium oleander, suppresses glioblastoma stem cells by inhibiting GRP78 and inducing programmed necroptotic cell death

Successful treatment of glioblastoma multiforme (GBM), an aggressive form of primary brain neoplasm, mandates the need to develop new therapeutic strategies. In this study, we investigated the potential of PBI-05204 in targeting GBM stem cells (GSCs) and the underlying mechanisms. Treatment with PBI-05204 significantly reduced both the number and size of tumor spheres derived from patient-derived GSCs (GBM9, GSC28 and TS543), and suppressed the tumorigenesis of GBM9 xenografts. Moreover, PBI-05204 treatment led to a significant decrease in the expression of CD44 and NANOG, crucial markers of progenitor stem cells, in GBM9 and GSC28 GSCs. This treatment also down-regulated GRP78 expression in both GSC types. Knocking down GRP78 expression through GRP78 siRNA transfection in GBM9 and GSC28 GSCs also resulted in reduced spheroid size and CD44 expression. Combining PBI-05204 with GRP78 siRNA further decreased spheroid numbers compared to GRP78 siRNA treatment alone. PBI-05204 treatment led to increased expression of pRIP1K and pRIP3K, along with enhanced binding of RIPK1/RIPK3 in GBM9 and GSC28 cells, resembling the effects observed in GRP78-silenced GSCs, suggesting that PBI-05204 induced necroptosis in these cells. Furthermore, oleandrin, a principle active cardiac glycoside component of PBI-05204, showed the ability to inhibit the self-renewal capacity in GSCs. These findings highlight the potential of PBI-05204 as a promising candidate for the development of novel therapies that target GBM stem cells.

Marine-derived antimicrobial peptide piscidin-1 triggers extrinsic and intrinsic apoptosis in oral squamous cell carcinoma through reactive oxygen species production and inhibits angiogenesis

Cancer of the head and neck encompasses a wide range of cancers, including oral and oropharyngeal cancers. Oral cancer is often diagnosed at advanced stages and has a dismal prognosis. Piscidin-1, a marine antimicrobial peptide (AMP) containing approximately 22 amino acids, also exhibits significant anticancer properties. We investigated the possible anti-oral cancer effects of piscidin-1 and clarified the mechanisms underlying these effects. We treated the oral squamous cell carcinoma cell lines OC2 and SCC4 with piscidin-1. Cell viability and the expression of different hallmark apoptotic molecules, including reactive oxygen species (ROS), were tested using the appropriate MTT assay, flow cytometry and western blotting assays, and human umbilical vein endothelial cell (HUVEC) wound healing, migration, and tube formation (angiogenesis) assays. Piscidin-1 increases cleaved caspase 3 levels to induce apoptosis. Piscidin-1 also increases ROS levels and intensifies oxidative stress in the endoplasmic reticulum and mitochondria, causing mitochondrial dysfunction. Additionally, it decreases the oxygen consumption rates and activity of mitochondrial complexes I-V. As expected, the antioxidants MitoTEMPOL and N-acetylcysteine reduce piscidin-1-induced ROS generation and intracellular calcium accumulation. Piscidin-1 also inhibits matrix metalloproteinase (MMP)-2/-9 expression in HUVECs, affecting migration and tube formation angiogenesis. We demonstrated that piscidin-1 can promote apoptosis via both intrinsic and extrinsic apoptotic pathways and findings indicate that piscidin-1 has anti-proliferative and anti-angiogenic properties in oral cancer treatment. Our study on piscidin-1 thus provides a basis for future translational anti-oral cancer drug research and a new theoretical approach for anti-oral cancer clinical research.

Targeting ROS in cancer: rationale and strategies

Reactive oxygen species (ROS) in biological systems are transient but essential molecules that are generated and eliminated by a complex set of delicately balanced molecular machineries. Disruption of redox homeostasis has been associated with various human diseases, especially cancer, in which increased ROS levels are thought to have a major role in tumour development and progression. As such, modulation of cellular redox status by targeting ROS and their regulatory machineries is considered a promising therapeutic strategy for cancer treatment. Recently, there has been major progress in this field, including the discovery of novel redox signalling pathways that affect the metabolism of tumour cells as well as immune cells in the tumour microenvironment, and the intriguing ROS regulation of biomolecular phase separation. Progress has also been made in exploring redox regulation in cancer stem cells, the role of ROS in determining cell fate and new anticancer agents that target ROS. This Review discusses these research developments and their implications for cancer therapy and drug discovery, as well as emerging concepts, paradoxes and future perspectives.

Mitochondria: A source of potential biomarkers for non-communicable diseases

Mitochondria, as an endosymbiont of eukaryotic cells, controls multiple cellular activities, including respiration, reactive oxygen species production, fatty acid synthesis, and death. Though the majority of functional mitochondrial proteins are translated through a nucleus-controlled process, very few of them (∼10%) are translated within mitochondria through their own machinery. Germline and somatic mutations in mitochondrial and nuclear DNA significantly impact mitochondrial homeostasis and function. Such modifications disturbing mitochondrial biogenesis, metabolism, or mitophagy eventually resulted in cellular pathophysiology. In this chapter, we discussed the impact of mitochondria and its dysfunction on several non-communicable diseases like cancer, diabetes, neurodegenerative, and cardiovascular problems. Mitochondrial dysfunction and its outcome could be screened by currently available omics-based techniques, flow cytometry, and high-resolution imaging. Such characterization could be evaluated as potential biomarkers to assess the disease burden and prognosis.

Up-regulation of MIC19 promotes growth and metastasis of hepatocellular carcinoma by activating ROS/NF-κB signaling

BACKGROUND

Mitochondrial malfunction has been well-recognized as a critical step in the pathogenesis of many types of diseases, including cancer. MIC19 is a core a subunit of the MICOS complex that plays a critical role in maintaining the normal function of mitochondria. However, the biological functions of MIC19 in human hepatocellular carcinoma (HCC) remain unclear.

METHODS

The expression level of MIC19 in HCC was evaluated by bioinformatics analysis, quantitative real-time PCR and immunohistochemistry staining assays. Cell growth and metastasis experiments were used to assess the biological functions of MIC19 in HCC cells.

FINDINGS

MIC19 expression was frequently upregulated in both human HCC specimens and cell lines, and its upregulation is closely associated with patients' survival. Results from loss-of-function and gain-of-function experiments demonstrated that knockdown of MIC19 significantly attenuated, while overexpression of MIC19 enhanced, the proliferation, colony formation, migration and invasion abilities of HCC cells. Mechanistically, we found that MIC19 has no effect on mitochondrial energy production, while activated ROS/NF-κB signaling, which was required for MIC19-promoted HCC growth and metastasis.

INTERPRETATION

Our findings suggest that MIC19 play a critical oncogenic role in HCC, implying that MIC19 may serve as a potential therapeutic target in the treatment of HCC.

A novel NIR fluorescent probe inhibits melanoma progression through apoptosis and ERK/DRP1-mediated mitochondrial fission

Melanoma, a highly metastatic malignant tumour, necessitated early detection and intervention. This study focuses on a hemicyanine fluorescent probe activated by near-infrared (NIR) light for bioimaging and targeted mitochondrial action in melanoma cells. IR-418, our newly designed hemicyanine-based NIR fluorescent probe, demonstrated effective targeting of melanoma cell mitochondria for NIR imaging. In vitro and in vivo experiments revealed IR-418's inhibition of melanoma growth through the promotion of mitochondrial apoptosis (Bax/Bcl-2/Cleaved Caspase pathway). Moreover, IR-418 inhibited melanoma metastasis by inhibiting mitochondrial fission through the ERK/DRP1 pathway. Notably, IR-418 mitigated abnormal ATL and ASL elevations caused by tumours without inflicting significant organ damage, indicating its high biocompatibility. In conclusion, IR-418, a novel hemicyanine-based NIR fluorescent probe targeting the mitochondria, exhibits significant fluorescence imaging capability, anti-melanoma proliferation, anti-melanoma lung metastasis activities and high biosafety. Therefore, it has significant potential in the early diagnosis and treatment of melanoma.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

miR-128-3p alleviates airway inflammation in asthma by targeting SIX1 to regulate mitochondrial fission and fusion

Bronchial asthma is known for airway inflammation, hyperresponsiveness, and remodeling.MicroRNAs (MiRNAs) have been involved in the development of asthma, whereas, the mechanism of various MiRNAs in asthma remains to be elucidated. In this study, we aim to explore the mechanism of miR-128-3p in asthma-related airway inflammation by targeting sine oculis homeobox homolog 1 (SIX1) to regulate the mitochondrial function. In an ovalbumin (OVA) asthma mouse model, miR-128-3p levels were found to be significantly diminished. Administration of miR-128-3p agomir decreased peribronchial inflammatory cell infiltration and improved airway inflammation. Afterwards, we used the luciferase reporter assay to predict and confirmed that SIX1 is a target gene of miR-128-3p. Overexpression of miR-128-3p attenuated IL-13-induced cellular inflammation and ROS production in bronchial epithelial cells (BEAS-2B). In vitro, overexpression of miR-128-3p and SIX1 knockdown mitigated mitochondrial fragmentation, reduced Drp1-mediated mitochondrial division, and upregulated mitochondrial membrane potential. Moreover, led to decreased production of ROS/mitochondrial ROS, P-Drp1(616) and Fis1 expression, while enhancing P-Drp1(637), MFN1, caspase-3/9, and Bax-mediated apoptosis. Our findings demonstrated that miR-128-3p could alleviate airway inflammation by downregulating SIX1 and improving mitochondrial function, positioning the miR-128-3p/SIX1/Drp1 signaling as a potential therapeutic target for asthma.

The Multifaceted Roles of NRF2 in Cancer: Friend or Foe?

Physiological concentrations of reactive oxygen species (ROS) play vital roles in various normal cellular processes, whereas excessive ROS generation is central to disease pathogenesis. The nuclear factor erythroid 2-related factor 2 (NRF2) is a critical transcription factor that regulates the cellular antioxidant systems in response to oxidative stress by governing the expression of genes encoding antioxidant enzymes that shield cells from diverse oxidative alterations. NRF2 and its negative regulator Kelch-like ECH-associated protein 1 (KEAP1) have been the focus of numerous investigations in elucidating whether NRF2 suppresses tumor promotion or conversely exerts pro-oncogenic effects. NRF2 has been found to participate in various pathological processes, including dysregulated cell proliferation, metabolic remodeling, and resistance to apoptosis. Herein, this review article will examine the intriguing role of phase separation in activating the NRF2 transcriptional activity and explore the NRF2 dual impacts on tumor immunology, cancer stem cells, metastasis, and long non-coding RNAs (LncRNAs). Taken together, this review aims to discuss the NRF2 multifaceted roles in both cancer prevention and promotion while also addressing the advantages, disadvantages, and limitations associated with modulating NRF2 therapeutically in cancer treatment.

The iron chelator and OXPHOS inhibitor VLX600 induces mitophagy and an autophagy-dependent type of cell death in glioblastoma cells

Induction of alternative, non-apoptotic cell death programs such as cell-lethal autophagy and mitophagy represent possible strategies to combat glioblastoma (GBM). Here we report that VLX600, a novel iron chelator and oxidative phosphorylation (OXPHOS) inhibitor, induces a caspase-independent type of cell death that is partially rescued in adherent U251 ATG5/7 (autophagy related 5/7) knockout (KO) GBM cells and NCH644 ATG5/7 knockdown (KD) glioma stem-like cells (GSCs), suggesting that VLX600 induces an autophagy-dependent cell death (ADCD) in GBM. This ADCD is accompanied by decreased oxygen consumption, increased expression/mitochondrial localization of BNIP3 (BCL2 interacting protein 3) and BNIP3L (BCL2 interacting protein 3 like), the induction of mitophagy as demonstrated by diminished levels of mitochondrial marker proteins [e.g., COX4I1 (cytochrome c oxidase subunit 4I1)] and the mitoKeima assay as well as increased histone H3 and H4 lysine tri-methylation. Furthermore, the extracellular addition of iron is able to significantly rescue VLX600-induced cell death and mitophagy, pointing out an important role of iron metabolism for GBM cell homeostasis. Interestingly, VLX600 is also able to completely eliminate NCH644 GSC tumors in an organotypic brain slice transplantation model. Our data support the therapeutic concept of ADCD induction in GBM and suggest that VLX600 may be an interesting novel drug candidate for the treatment of this tumor.NEW & NOTEWORTHY Induction of cell-lethal autophagy represents a possible strategy to combat glioblastoma (GBM). Here, we demonstrate that the novel iron chelator and OXPHOS inhibitor VLX600 exerts pronounced tumor cell-killing effects in adherently cultured GBM cells and glioblastoma stem-like cell (GSC) spheroid cultures that depend on the iron-chelating function of VLX600 and on autophagy activation, underscoring the context-dependent role of autophagy in therapy responses. VLX600 represents an interesting novel drug candidate for the treatment of this tumor.

A novel mitochondria-targeting compound exerts therapeutic effects against melanoma by inducing mitochondria-mediated apoptosis and autophagy in vitro and in vivo

Melanoma is the most invasive skin cancer, with a high mortality rate. However, existing therapeutic drugs have side effects, low reactivity, and lead to drug resistance. As the power source in cells, mitochondria play an important role in the survival of cancer cells and are an important target for tumor therapy. This study aimed to develop a new anti-melanoma compound that targets mitochondria, evaluate its effect on the proliferation and metastasis of melanoma cells, and explore its mechanism of action. The novel mitochondria-targeting compound, SCZ0148, was synthesized by modifying the structure of cyanine. Then, A375 and B16 cells were incubated with different concentrations of SCZ0148, and different doses of SCZ0148 were administered to A375 and B16 xenograft zebrafish. The results showed that SCZ0148 targeted mitochondria, had dose- and time-dependent effects on the proliferation of melanoma cell lines, and had no obvious side effects on normal cells. In addition, SCZ0148 induced melanoma cell apoptosis through the reactive oxygen species-mediated mitochondrial pathway of apoptosis and promoted autophagy. SCZ0148 significantly inhibited the migration of melanoma cells via a matrix metalloprotein 9-mediated pathway. Similarly, SCZ0148 inhibited melanoma cell proliferation in a concentration-dependent manner in vivo. In summary, SCZ0148 may be a novel anti-melanoma compound that targets mitochondria.

ABBV-744 induces autophagy in gastric cancer cells by regulating PI3K/AKT/mTOR/p70S6k and MAPK signaling pathways

The mortality rates of gastric cancer remain high due to limited therapeutic strategies. As a highly selective inhibitor of the BD2 domain of BET family proteins, ABBV-744 has potent chemotherapeutic activity against various human solid tumors. However, whether ABBV-744 has potential anti-tumor effects in gastric cancer remain largely unknown. In this study, we evaluated the effect of ABBV-744 on gastric cancer cells and explored the possible underlying mechanisms. We found that ABBV-744 inhibited the growth of gastric cancer cells and patient-derived tumor organoids in a dose-dependent manner. Cellular experiments revealed that ABBV-744 induced mitochondria damage, reactive oxygen species accumulation, cell cycle arrest and apoptotic cell death in gastric cancer cells. Transcriptomic analysis using RNA-sequencing data identified autophagy as a crucial pathway involved in the cell death caused by ABBV-744. Mechanically, further studies showed that ABBV-744 induced autophagy flux in gastric cancer cells by inactivating PI3K/AKT/mTOR/p70S6k and activating the MAPK signaling pathways. In vivo mouse xenograft studies demonstrated that ABBV-744 significantly suppressed the growth of gastric cancer cells via inducing autophagy. Taken together, our results suggest that ABBV-744 is a novel drug candidate for gastric cancer.

Recent Advances in Targeted Drug Delivery Strategy for Enhancing Oncotherapy

Targeted drug delivery is a precise and effective strategy in oncotherapy that can accurately deliver drugs to tumor cells or tissues to enhance their therapeutic effect and, meanwhile, weaken their undesirable side effects on normal cells or tissues. In this research field, a large number of researchers have achieved significant breakthroughs and advances in oncotherapy. Typically, nanocarriers as a promising drug delivery strategy can effectively deliver drugs to the tumor site through enhanced permeability and retention (EPR) effect-mediated passive targeting and various types of receptor-mediated active targeting, respectively. Herein, we review recent targeted drug delivery strategies and technologies for enhancing oncotherapy. In addition, we also review two mainstream drug delivery strategies, passive and active targeting, based on various nanocarriers for enhancing tumor therapy. Meanwhile, a comparison and combination of passive and active targeting are also carried out. Furthermore, we discuss the associated challenges of passive and active targeted drug delivery strategies and the prospects for further study.

Cancer stem cell fate determination: mito-nuclear communication

Cancer stem cells (CSCs) are considered to be responsible for tumor recurrence and metastasis. Therefore, clarification of the mechanisms involved in CSC stemness maintenance and cell fate determination would provide a new strategy for cancer therapy. Unregulated cellular energetics has been accepted as one of the hallmarks of cancer cells, but recent studies have revealed that mitochondrial metabolism can also actively determine CSC fate by affecting nuclear stemness gene expression. Herein, from the perspective of mito-nuclear communication, we review recent progress on the influence of mitochondria on CSC potential from four aspects: metabolism, dynamics, mitochondrial homeostasis, and reactive oxygen species (ROS). Video Abstract.

In Response to Precision Medicine: Current Subcellular Targeting Strategies for Cancer Therapy

Emerging as a potent anticancer treatment, subcellular targeted cancer therapy has drawn increasing attention, bringing great opportunities for clinical application. Here, two targeting strategies for four main subcellular organelles (mitochondria, lysosome, endoplasmic reticulum, and nucleus), including molecule- and nanomaterial (inorganic nanoparticles, micelles, organic polymers, and others)-based targeted delivery or therapeutic strategies, are summarized. Phototherapy, chemotherapy, radiotherapy, immunotherapy, and "all-in-one" combination therapy are among the strategies covered in detail. Such materials are constructed based on the specific properties and relevant mechanisms of organelles, enabling the elimination of tumors by inducing dysfunction in the corresponding organelles or destroying specific structures. The challenges faced by organelle-targeting cancer therapies are also summarized. Looking forward, a paradigm for organelle-targeting therapy with enhanced therapeutic efficacy compared to current clinical approaches is envisioned.

Mitochondrial Dysfunction: A Cellular and Molecular Hub in Pathology of Metabolic Diseases and Infection

Mitochondria are semiautonomous doubly membraned intracellular components of cells. The organelle comprises of an external membrane, followed by coiled structures within the membrane called cristae, which are further surrounded by the matrix spaces followed by the space between the external and internal membrane of the organelle. A typical eukaryotic cell contains thousands of mitochondria within it, which make up 25% of the cytoplasm present in the cell. The organelle acts as a common point for the metabolism of glucose, lipids, and glutamine. Mitochondria chiefly regulate oxidative phosphorylation-mediated aerobic respiration and the TCA cycle and generate energy in the form of ATP to fulfil the cellular energy needs. The organelle possesses a unique supercoiled doubly stranded mitochondrial DNA (mtDNA) which encodes several proteins, including rRNA and tRNA crucial for the transport of electrons, oxidative phosphorylation, and initiating genetic repair processors. Defects in the components of mitochondria act as the principal factor for several chronic cellular diseases. The dysfunction of mitochondria can cause a malfunction in the TCA cycle and cause the leakage of the electron respiratory chain, leading to an increase in reactive oxygen species and the signaling of aberrant oncogenic and tumor suppressor proteins, which further alter the pathways involved in metabolism, disrupt redox balance, and induce endurance towards apoptosis and several treatments which play a major role in developing several chronic metabolic conditions. The current review presents the knowledge on the aspects of mitochondrial dysfunction and its role in cancer, diabetes mellitus, infections, and obesity.

Mitochondrial transplantation: Effects on chemotherapy in prostate and ovarian cancer cells in vitro and in vivo

Prostate and ovarian cancers affect the male and female reproductive organs and are among the most common cancers in developing countries. Previous studies have demonstrated that cancer cells have a high rate of aerobic glycolysis that is present in nearly all invasive human cancers and persists even under normoxic conditions. Aerobic glycolysis has been correlated with chemotherapeutic resistance and tumor aggressiveness. These data suggest that mitochondrial dysfunction may confer a significant proliferative advantage during the somatic evolution of cancer. In this study we investigated the effect of direct mitochondria transplantation on cancer cell proliferation and chemotherapeutic sensitivity in prostate and ovarian cancer models, both in vitro and in vivo. Our results show that the transplantation of viable, respiration competent mitochondria has no effect on cancer cell proliferation but significantly decreases migration and alters cell cycle checkpoints. Our results further demonstrate that mitochondrial transplantation significantly increases chemotherapeutic sensitivity, providing similar apoptotic levels with low-dose chemotherapy as that achieved with high-dose chemotherapy. These results suggest that mitochondria transplantation provides a novel approach for early prostate and ovarian cancer therapy, significantly increasing chemotherapeutic sensitivity in in vitro and in vivo murine models.

PINK1-Mediated Mitophagy Promotes Oxidative Phosphorylation and Redox Homeostasis to Induce Drug-Tolerant Persister Cancer Cells

The drug-tolerant persister (DTP) state enables cancer cells to evade cytotoxic stress from anticancer therapy. However, the mechanisms governing DTP generation remain poorly understood. Here, we observed that lung adenocarcinoma (LUAD) cells and organoids entered a quiescent DTP state to survive MAPK inhibitor treatment. DTP cells following MAPK inhibition underwent a metabolic switch from glycolysis to oxidative phosphorylation (OXPHOS). PTEN-induced kinase 1 (PINK1), a serine/threonine kinase that initiates mitophagy, was upregulated to maintain mitochondrial homeostasis during DTP generation. PINK1-mediated mitophagy supported DTP cell survival and contributed to poor prognosis. Mechanistically, MAPK pathway inhibition resulted in MYC-dependent transcriptional upregulation of PINK1, leading to mitophagy activation. Mitophagy inhibition using either clinically applicable chloroquine or depletion of PINK1 eradicated drug tolerance and allowed complete response to MAPK inhibitors. This study uncovers PINK1-mediated mitophagy as a novel tumor protective mechanism for DTP generation, providing a therapeutic opportunity to eradicate DTP and achieve complete responses.

SIGNIFICANCE

DTP cancer cells that cause relapse after anticancer therapy critically depend on PINK1-mediated mitophagy and metabolic reprogramming, providing a therapeutic opportunity to eradicate persister cells to prolong treatment efficacy.

Mitochondrial dysfunction-targeted nanosystems for precise tumor therapeutics

Mitochondria play critical roles in the regulation of the proliferation and apoptosis of cancerous cells. Targeted induction of mitochondrial dysfunction in cancer cells by multifunctional nanosystems for cancer treatment has attracted increasing attention in the past few years. Numerous therapeutic nanosystems have been designed for precise tumor therapy by inducing mitochondrial dysfunction, including reducing adenosine triphosphate, breaking redox homeostasis, inhibiting glycolysis, regulating proteins, membrane potential depolarization, mtDNA damage, mitophagy dysregulation and so on. Understanding the mechanisms of mitochondrial dysfunction would be helpful for efficient treatment of diseases and accelerating the translation of these therapeutic strategies into the clinic. Then, various strategies to construct mitochondria-targeted nanosystems and induce mitochondrial dysfunction are summarized, and the recent research progress regarding precise tumor therapeutics is highlighted. Finally, the major challenges and an outlook in this rapidly developing field are discussed. This review is expected to inspire further development of novel mitochondrial dysfunction-based strategies for precise treatments of cancer and other human diseases.

Mitochondrial Modulators: The Defender

Mitochondria are widely considered the "power hub" of the cell because of their pivotal roles in energy metabolism and oxidative phosphorylation. However, beyond the production of ATP, which is the major source of chemical energy supply in eukaryotes, mitochondria are also central to calcium homeostasis, reactive oxygen species (ROS) balance, and cell apoptosis. The mitochondria also perform crucial multifaceted roles in biosynthetic pathways, serving as an important source of building blocks for the biosynthesis of fatty acid, cholesterol, amino acid, glucose, and heme. Since mitochondria play multiple vital roles in the cell, it is not surprising that disruption of mitochondrial function has been linked to a myriad of diseases, including neurodegenerative diseases, cancer, and metabolic disorders. In this review, we discuss the key physiological and pathological functions of mitochondria and present bioactive compounds with protective effects on the mitochondria and their mechanisms of action. We highlight promising compounds and existing difficulties limiting the therapeutic use of these compounds and potential solutions. We also provide insights and perspectives into future research windows on mitochondrial modulators.

Crebanine induces ROS-dependent apoptosis in human hepatocellular carcinoma cells via the AKT/FoxO3a signaling pathway

Background: Hepatocellular carcinoma (HCC), as an aggressive cancer with a high mortality rate, needs high-efficiency and low-toxicity drug therapy. Natural products have great potential as candidate lead compounds for the development of new HCC drugs. Crebanine is an isoquinoline alkaloid derived from Stephania with various potential pharmacological effects such as anti-cancer. However, the molecular mechanism underlying crebanine-induced liver cancer cells apoptosis has not been reported. Here, we investigated the effect of crebanine on HCC and identified a potential mechanism of action. Methods: In this paper, we intend to detect the toxic effects of crebanine on hepatocellular carcinoma HepG2 cells through a series of in vitro experiments, including detecting the effects of crebanine on the proliferation of HepG2 cells using the CCK8 method and plate cloning assay, observing the growth status and morphological changes of crebanine on HepG2 cells by inverted microscopy; and using the Transwell method to determine the the effect of crebanine on the migration and invasion ability of HepG2 cells; using Hoechst 33258 assay to stain cancer cells, thus observing the effect of crebanine on the morphology of HepG2 apoptotic cells, and detecting the apoptotic state and level of HepG2 cells by flow cytometry; using ROS kit and JC-1 assay kit to detect the changes of reactive oxygen species and mitochondrial membrane potential of HepG2 The immunofluorescence assay was taken to verify whether crebanine had an effect on the expression of p-FoxO3a in cancer cells; the Wetern blot assay was also used to examine the effect of crebanine on proteins related to the mitochondrial apoptotic pathway and its effect on the regulation of the relative protein expression of AKT/FoxO3a axis; after this, NAC and AKT inhibitor LY294002 were used to cells were pretreated with NAC and AKT inhibitor LY294002, respectively, in order to further validate the inhibitory effect of crebanine. Results: It was shown that crebanine effectively inhibited the growth and capacity of HepG2 cells migration and invasion in a dose-dependent manner. Furthermore, the effect of crebanine on the morphology of HepG2 cells was observed through microscopy. Meanwhile, crebanine induced apoptosis by causing reactive oxygen species (ROS) burst and mitochondrial membrane potential (MMP) disrupt. We found that crebanine could down-regulate Bcl-2 and up-regulate Bax, cleaved-PARP, cleaved-caspase-3 and cleaved-caspase-9, but these effects were overturned by ROS inhibitor N-acetylcysteine (NAC). Crebanine also down-regulated p-AKT and p-FoxO3a, and the PI3K inhibitor LY294002 significantly enhances this effect. We also found that the expression of AKT/FoxO3a signaling pathway was ROS-dependent. As shown by Western blots, NAC could partially attenuate the inhibitory effect of crebanine on AKT and FoxO3a phosphorylation. Conclusion: Based on our results, our results suggest that crebanine, as a compound with potential anticancer activity, has significant cytotoxic effects on hepatocellular carcinoma,and it likely induces apoptosis via ROS in the mitochondrial pathway and simultaneously affects the biological function of HCC via the ROS-AKT-FoxO3a signaling axis.

Ivermectin and gemcitabine combination treatment induces apoptosis of pancreatic cancer cells via mitochondrial dysfunction

Pancreatic cancer is an aggressive cancer characterized by high mortality and poor prognosis, with a survival rate of less than 5 years in advanced stages. Ivermectin, an antiparasitic drug, exerts antitumor effects in various cancer types. This is the first study to evaluate the anticancer effects of the combination of ivermectin and gemcitabine in pancreatic cancer. We found that the ivermectin–gemcitabine combination treatment suppressed pancreatic cancer more effectively than gemcitabine alone treatment. The ivermectin–gemcitabine combination inhibited cell proliferation via G1 arrest of the cell cycle, as evidenced by the downregulation of cyclin D1 expression and the mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT-3) signaling pathway. Ivermectin–gemcitabine increased cell apoptosis by inducing mitochondrial dysfunction via the overproduction of reactive oxygen species and decreased the mitochondrial membrane potential. This combination treatment also decreased the oxygen consumption rate and inhibited mitophagy, which is important for cancer cell death. Moreover, in vivo experiments confirmed that the ivermectin–gemcitabine group had significantly suppressed tumor growth compared to the gemcitabine alone group. These results indicate that ivermectin exerts synergistic effects with gemcitabine, preventing pancreatic cancer progression, and could be a potential antitumor drug for the treatment of pancreatic cancer.

Mitochondrial dysfunction in heart failure and its therapeutic implications

The ATP consumption in heart is very intensive to support muscle contraction and relaxation. Mitochondrion is the power plant of the cell. Mitochondrial dysfunction has long been believed as the primary mechanism responsible for the inability of energy generation and utilization in heart failure. In addition, emerging evidence has demonstrated that mitochondrial dysfunction also contributes to calcium dysregulation, oxidative stress, proteotoxic insults and cardiomyocyte death. These elements interact with each other to form a vicious circle in failing heart. The role of mitochondrial dysfunction in the pathogenesis of heart failure has attracted increasing attention. The complex signaling of mitochondrial quality control provides multiple targets for maintaining mitochondrial function. Design of therapeutic strategies targeting mitochondrial dysfunction holds promise for the prevention and treatment of heart failure.

Protein phosphatase 2A-B56γ-Drp1-Rab7 signaling axis regulates mitochondria-lysosome crosstalk to sensitize the anti-cancer therapy of hepatocellular carcinoma

Mitochondria-lysosome crosstalk is an intercellular communication platform regulating mitochondrial quality control (MQC). Activated dynamin-related protein 1 (Drp1) with phosphorylation at serine 616 (p-Drp1^Ser616) plays a critical role in mitophagy-dependent cell survival and anti-cancer therapy for hepatocellular carcinoma (HCC). However, the underlying mechanisms that p-Drp1^Ser616 involved in regulating mitochondria-lysosome crosstalk and mediating anti-HCC therapy remain unknown. HCC cells and mouse xenograft models were conducted to evaluate the relationship between p-Drp1^Ser616 and Ras-associated protein 7 (Rab7) and the underlying mechanism by protein phosphatase 2A (PP2A)-B56γ regulating mitophagy via dephosphorylation of p-Drp1^Ser616 in HCC. Herein, we found that Drp1 was frequently upregulated and was associated with poor prognosis in HCC. Mitochondrial p-Drp1^Ser616 was a novel inter-organelle tethering protein localized to mitochondrion and lysosome membrane contact sites (MCSs) via interaction with Rab7 to trigger an increase in the mitochondria-lysosome crosstalk, resulting in PINK1-Parkin-dependent mitophagy and anti-apoptosis in HCC cells under the treatment of chemotherapy drugs. Moreover, we demonstrate that B56γ-mediated direct dephosphorylation of p-Drp1^Ser616 inhibited mitophagy and thus increased mitochondria-dependent apoptosis. Overall, our findings demonstrated that activation of B56γ sensitizes the anti-cancer effect of HCC chemoprevention via dephosphorylated regulation of p-Drp1^Ser616 in inhibiting the interaction between p-Drp1^Ser616 and Rab7, which may provide a novel mechanism underlying the theranostics for targeting intervention in HCC.

Hesperadin suppresses pancreatic cancer through ATF4/GADD45A axis at nanomolar concentrations

Pancreatic cancer (PC) is a fatal disease with poor survival and limited therapeutic strategies. In this study, we identified Hesperadin as a potent anti-cancer compound against PC, from a high-throughput screening of a commercial chemical library associated with cell death. Hesperadin induced potent growth inhibition in PC cell lines and patient-derived tumor organoids in a dose- and time-dependent manner, with IC50 values in the nanomolar range. Cellular studies showed that Hesperadin caused mitochondria damage in PC cells, resulting in reactive oxygen species production, ER stress and apoptotic cell death. Transcriptomic analysis using RNA-sequencing data identified GADD45A as a potential target of Hesperadin. Mechanistic studies showed that Hesperadin could increase GADD45A expression in PC cells via ATF4, leading to apoptosis. Moreover, immunohistochemical staining of 92 PC patient samples demonstrated the correlation between ATF4 and GADD45A expression. PC xenograft studies demonstrated that Hesperadin could effectively inhibit the growth of PC cells in vivo. Together, these findings suggest that Hesperadin is a novel drug candidate for PC.

Mitochondria-Targeted, Nanoparticle-Based Drug-Delivery Systems: Therapeutics for Mitochondrial Disorders

Apart from ATP generation, mitochondria are involved in a wide range of functions, making them one of the most prominent organelles of the human cell. Mitochondrial dysfunction is involved in the pathophysiology of several diseases, such as cancer, neurodegenerative diseases, cardiovascular diseases, and metabolic disorders. This makes it a target for a variety of therapeutics for the diagnosis and treatment of these diseases. The use of nanoparticles to target mitochondria has significant importance in modern times because they provide promising ways to deliver drug payloads to the mitochondria by overcoming challenges, such as low solubility and poor bioavailability, and also resolve the issues of the poor biodistribution of drugs and pharmacokinetics with increased specificity. This review assesses nanoparticle-based drug-delivery systems, such as liposomes, DQAsome, MITO-Porters, micelles, polymeric and metal nanocarriers, as well as quantum dots, as mitochondria-targeted strategies and discusses them as a treatment for mitochondrial disorders.

Mitochondrial calcium uptake regulates tumour progression in embryonal rhabdomyosarcoma

Embryonal rhabdomyosarcoma (ERMS) is characterised by a failure of cells to complete skeletal muscle differentiation. Although ERMS cells are vulnerable to oxidative stress, the relevance of mitochondrial calcium homoeostasis in oncogenesis is unclear. Here, we show that ERMS cell lines as well as primary tumours exhibit elevated expression of the mitochondrial calcium uniporter (MCU). MCU knockdown resulted in impaired mitochondrial calcium uptake and a reduction in mitochondrial reactive oxygen species (mROS) levels. Phenotypically, MCU knockdown cells exhibited reduced cellular proliferation and motility, with an increased propensity to differentiate in vitro and in vivo. RNA-sequencing of MCU knockdown cells revealed a significant reduction in genes involved in TGFβ signalling that play prominent roles in oncogenesis and inhibition of myogenic differentiation. Interestingly, modulation of mROS production impacted TGFβ signalling. Our study elucidates mechanisms by which mitochondrial calcium dysregulation promotes tumour progression and suggests that targeting the MCU complex to restore mitochondrial calcium homoeostasis could be a therapeutic avenue in ERMS.

Rhodamine 101 Conjugates of Triterpenoic Amides Are of Comparable Cytotoxicity as Their Rhodamine B Analogs

Pentacyclic triterpenoic acids (betulinic, oleanolic, ursolic, and platanic acid) were selected and subjected to acetylation followed by the formation of amides derived from either piperazine or homopiperazine. These amides were coupled with either rhodamine B or rhodamine 101. All of these compounds were screened for their cytotoxic activity in SRB assays. As a result, the cytotoxicity of the parent acids was low but increased slightly upon their acetylation while a significant increase in cytotoxicity was observed for piperazinyl and homopiperazinyl amides. A tremendous improvement in cytotoxicity was observed; however, for the rhodamine B and rhodamine 101 conjugates, and compound 27, an ursolic acid derived homopiperazinyl amide holding a rhodamine 101 residue showed an EC50 = 0.05 µM for A2780 ovarian cancer cells while being less cytotoxic for non-malignant fibroblasts. To date, the rhodamine 101 derivatives presented here are the first examples of triterpene derivatives holding a rhodamine residue different from rhodamine B.

ZWZ-3, a Fluorescent Probe Targeting Mitochondria for Melanoma Imaging and Therapy

The increased drug resistance and metastasis of melanoma resulted in poor prognosis of patients. Here, we designed and synthesized a novel hemicyanine-based fluorescent probe ZWZ-3, and investigated its application for melanoma imaging and treatment both in vitro and in vivo. ZWZ-3 preferentially accumulated in melanoma cells via a process that depended on the organic anion-transporting polypeptide (OATP), which targeted mitochondria on the hemicyanine cationic nitrogen. In addition, we investigated the effect and molecular mechanism of ZWZ-3 in melanoma. In vitro studies showed that ZWZ-3 promoted the generation of reactive oxygen species and induced mitochondrial-mediated cell apoptosis by upregulating Bax and activating caspase-3, caspase-9, and PARP. Importantly, ZWZ-3 also induced autophagy by upregulating LC-3II and Atg5 and downregulating P62. It significantly suppressed tumor growth of A375 xenograft tumor in mice without notable side effects. Histological and immunohistochemical analyses revealed that ZWZ-3 induced apoptosis and inhibited tumor cell proliferation. Thus, ZWZ-3 represents a novel theranostic agent that can be used to effectively targeting, detecting, and treating melanoma. It could also help monitoring disease progression and response to treatment.

Interfering with mitochondrial dynamics sensitizes glioblastoma multiforme to temozolomide chemotherapy

Glioblastoma multiforme (GBM) is a primary tumour of the central nervous system (CNS) that exhibits the highest degree of malignancy. Radiotherapy and chemotherapy are essential to prolong the survival time of patients. However, clinical work has demonstrated that sensitivity of GBM to chemotherapy decreases with time. The phenomenon of multi-drug resistance (MDR) reminds us that there may exist some fundamental mechanisms in the process of chemo-resistance. We tried to explore the mechanism of GBM chemo-resistance from the perspective of energy metabolism. First, we found that the oxidative phosphorylation (OXPHOS) level of SHG44 and U87 cells increased under TMZ treatment. In further studies, it was found that the expression of PINK1 and mitophagy flux downstream was downregulated in GBM cells, which were secondary to the upregulation of TP53 in tumour cells under TMZ treatment. At the same time, we examined the mitochondrial morphology in tumour cells and found that the size of mitochondria in tumour cells increased under the treatment of TMZ, which originated from the regulation of AMPK on the subcellular localization of Drp1 under the condition of unbalanced energy supply and demand in tumour cells. The accumulation of mitochondrial mass and the optimization of mitochondrial quality accounted for the increased oxidative phosphorylation, and interruption of the mitochondrial fusion process downregulated the efficiency of oxidative phosphorylation and sensitized GBM cells to TMZ, which was also confirmed in the in vivo experiment. What is more, interfering with this process is an innovative strategy to overcome the chemo-resistance of GBM cells.

Farrerol suppresses the progression of laryngeal squamous cell carcinoma via the mitochondria-mediated pathway

PURPOSE

In the context of well-known inhibitory effects of Farrerol on the invasion of lung squamous cell carcinoma cells, the unexplored effect and regulatory mechanism of Farrerol on laryngeal squamous cell carcinoma (LSCC) emerged as the target in this study.

METHODS

After treatment with Farrerol alone, or together with MitoTempo, the viability, apoptosis, cell cycle distribution, migration, and invasion of LSCC cells were measured using MTT, flow cytometry, wound-healing, and transwell assays, respectively. Meanwhile, the levels of cytochrome C (Cyt C), Cleaved caspase-3/9, Cyclin D1, E-cadherin, N-cadherin, and Vimentin in LSCC cells were evaluated by Western blot; the reactive oxygen species (ROS) formation intensity and the disruption of mitochondrial membrane potential (MMP) of LSCC cells were assessed using flow cytometry; and the effect of Farrerol on xenograft tumor formation was evaluated in animal experiment.

RESULTS

Farrerol (10, 20, 50 μM) inhibited the viability, proliferation, cell cycle progression, migration and invasion, but promoted apoptosis, ROS formation intensity and disruption of MMP of LSCC cells. Moreover, Farrerol up-regulated Cyt C (in the cytoplasm), Cleaved caspase-3/9 and E-cadherin levels, but down-regulated Cyclin D1, N-cadherin and Vimentin levels in LSCC cells. Additionally, we uncovered that MitoTempo reversed the promoting effects of Farrerol on ROS formation intensity, apoptosis, and Cyt C and Cleaved caspase-3/9 levels in LSCC cells, while improving the disruption of MMP in Farrerol-treated LSCC cells. Also, Farrerol lessened the volume and weight of mice tumors.

CONCLUSIONS

Farrerol suppressed the migration, invasion, and induced the apoptosis of LSCC cells via the mitochondria-mediated pathway.

N-Propargylglycine: a unique suicide inhibitor of proline dehydrogenase with anticancer activity and brain-enhancing mitohormesis properties

Proline dehydrogenase (PRODH) is a mitochondrial inner membrane flavoprotein critical for cancer cell survival under stress conditions and newly recognized as a potential target for cancer drug development. Reversible (competitive) and irreversible (suicide) inhibitors of PRODH have been shown in vivo to inhibit cancer cell growth with excellent host tolerance. Surprisingly, the PRODH suicide inhibitor N-propargylglycine (N-PPG) also induces rapid decay of PRODH with concordant upregulation of mitochondrial chaperones (HSP-60, GRP-75) and the inner membrane protease YME1L1, signifying activation of the mitochondrial unfolded protein response (UPRmt) independent of anticancer activity. The present study was undertaken to address two aims: (i) use PRODH overexpressing human cancer cells (ZR-75-1) to confirm the UPRmt inducing properties of N-PPG relative to another equipotent irreversible PRODH inhibitor, thiazolidine-2-carboxylate (T2C); and (ii) employ biochemical and transcriptomic approaches to determine if orally administered N-PPG can penetrate the blood-brain barrier, essential for its future use as a brain cancer therapeutic, and also potentially protect normal brain tissue by inducing mitohormesis. Oral daily treatments of N-PPG produced a dose-dependent decline in brain mitochondrial PRODH protein without detectable impairment in mouse health; furthermore, mice repeatedly dosed with 50 mg/kg N-PPG showed increased brain expression of the mitohormesis associated protease, YME1L1. Whole brain transcriptome (RNAseq) analyses of these mice revealed significant gene set enrichment in N-PPG stimulated neural processes (FDR p < 0.05). Given this in vivo evidence of brain bioavailability and neural mitohormesis induction, N-PPG appears to be unique among anticancer agents and should be evaluated for repurposing as a pharmaceutical capable of mitigating the proteotoxic mechanisms driving neurodegenerative disorders.

Hierarchical nanoclusters with programmed disassembly for mitochondria-targeted tumor therapy with MR imaging

Mitochondria are crucial metabolic organelles involved in tumorigenesis and tumor progression, and the induction of abnormal mitochondria metabolism is recognized as a strategy with strong potential for the exploration of advanced tumor therapeutics. Herein, hierarchical manganese silicate nanoclusters modified with triphenylphosphonium (MSNAs-TPP) were designed and synthesized for mitochondria-targeted tumor theranostics. The as-prepared MSNAs-TPP retains considerable dimensional and structural stability in the neutral physiological environment, favoring its accumulation at the tumor site. More interestingly, MSNAs-TPP may disassemble in a responsive manner to an acidic tumor microenvironment into ultrasmall manganese silicate nanocapsules (∼6 nm), enabling deep tumor penetration and mitochondria targeting. When reaching the mitochondria, the nanocapsules effectively deplete mitochondrial glutathione (GSH), and simultaneously release catalytic Mn²⁺ ions to induce amplified oxidative stress in the structure with the enriched CO₂ and H₂O₂ from mitochondria metabolism. As a result, MSNAs-TPP presents considerable antitumor effect without a clear side effect, both in vitro and in vivo. The study may provide an alternative concept in the development of intelligent nanotherapeutics for tumor treatment with high efficacy.

Engineered Cell-Penetrating Peptides for Mitochondrion-Targeted Drug Delivery in Cancer Therapy

Mitochondrion is a promising target in cancer therapy. However, gaining access to this organelle is difficult due to the obstacles to cross the complicated mitochondrial membrane. Cell-penetrating peptides (CPPs) with mitochondrion-targeting ability, named mitochondrion-targeting peptides (MTPs), are efficient tools to deliver exogenous therapeutics into mitochondria. Herein, we report several new MTPs, which can be readily synthesized via resin-based solid-phase peptide synthesis. In particular, MTP3 (compound 5), consisting of three positively charged arginines and two D- and L- alternating naphthylalanines, demonstrated excellent mitochondrion-targeting ability with high Pearson's correlation coefficient, suggesting that MTP3 has good potential for mitochondrion-targeted drug delivery. As proof-of-concept, the feasibility of MTP3 was validated by the preparation of a mitochondrion-targeting prodrug (compound 17, doxorubicin-based prodrug). This prodrug was subsequently confirmed to be specifically transported to the mitochondria of tumor cells, where it was able to release the native doxorubicin upon intracellular GSH activation, leading to mitochondrial depolarization and eventually cell death. Importantly, compound 17 showed good cytotoxicity against human tumor cells while negligible toxicity towards normal cells, indicating its potential as a potent mitochondrial medicine for targeted cancer therapy. Our study thus opens a way for engineered CPPs to be used to deliver bioactive cargos in mitochondrion-targeted cancer therapy.

New insights into mitophagy and stem cells

Mitophagy is a specific autophagic phenomenon in which damaged or redundant mitochondria are selectively cleared by autophagic lysosomes. A decrease in mitophagy can accelerate the aging process. Mitophagy is related to health and longevity and is the key to protecting stem cells from metabolic stress damage. Mitophagy decreases the metabolic level of stem cells by clearing active mitochondria, so mitophagy is becoming increasingly necessary to maintain the regenerative capacity of old stem cells. Stem cell senescence is the core problem of tissue aging, and tissue aging occurs not only in stem cells but also in transport amplifying cell chambers and the stem cell environment. The loss of the autophagic ability of stem cells can cause the accumulation of mitochondria and the activation of the metabolic state as well as damage the self-renewal ability and regeneration potential of stem cells. However, the claim remains controversial. Mitophagy is an important survival strategy against nutrient deficiency and starvation, and mitochondrial function and integrity may affect the viability, proliferation and differentiation potential, and longevity of normal stem cells. Mitophagy can affect the health and longevity of the human body, so the number of studies in this field has increased, but the mechanism by which mitophagy participates in stem cell development is still not fully understood. This review describes the potential significance of mitophagy in stem cell developmental processes, such as self-renewal, differentiation and aging. Through this work, we discovered the role and mechanism of mitophagy in different types of stem cells, identified novel targets for killing cancer stem cells and curing cancer, and provided new insights for future research in this field.

Ref-1 redox activity alters cancer cell metabolism in pancreatic cancer: exploiting this novel finding as a potential target

BACKGROUND

Pancreatic cancer is a complex disease with a desmoplastic stroma, extreme hypoxia, and inherent resistance to therapy. Understanding the signaling and adaptive response of such an aggressive cancer is key to making advances in therapeutic efficacy. Redox factor-1 (Ref-1), a redox signaling protein, regulates the conversion of several transcription factors (TFs), including HIF-1α, STAT3 and NFκB from an oxidized to reduced state leading to enhancement of their DNA binding. In our previously published work, knockdown of Ref-1 under normoxia resulted in altered gene expression patterns on pathways including EIF2, protein kinase A, and mTOR. In this study, single cell RNA sequencing (scRNA-seq) and proteomics were used to explore the effects of Ref-1 on metabolic pathways under hypoxia.

METHODS

scRNA-seq comparing pancreatic cancer cells expressing less than 20% of the Ref-1 protein was analyzed using left truncated mixture Gaussian model and validated using proteomics and qRT-PCR. The identified Ref-1's role in mitochondrial function was confirmed using mitochondrial function assays, qRT-PCR, western blotting and NADP assay. Further, the effect of Ref-1 redox function inhibition against pancreatic cancer metabolism was assayed using 3D co-culture in vitro and xenograft studies in vivo.

RESULTS

Distinct transcriptional variation in central metabolism, cell cycle, apoptosis, immune response, and genes downstream of a series of signaling pathways and transcriptional regulatory factors were identified in Ref-1 knockdown vs Scrambled control from the scRNA-seq data. Mitochondrial DEG subsets downregulated with Ref-1 knockdown were significantly reduced following Ref-1 redox inhibition and more dramatically in combination with Devimistat in vitro. Mitochondrial function assays demonstrated that Ref-1 knockdown and Ref-1 redox signaling inhibition decreased utilization of TCA cycle substrates and slowed the growth of pancreatic cancer co-culture spheroids. In Ref-1 knockdown cells, a higher flux rate of NADP + consuming reactions was observed suggesting the less availability of NADP + and a higher level of oxidative stress in these cells. In vivo xenograft studies demonstrated that tumor reduction was potent with Ref-1 redox inhibitor similar to Devimistat.

CONCLUSION

Ref-1 redox signaling inhibition conclusively alters cancer cell metabolism by causing TCA cycle dysfunction while also reducing the pancreatic tumor growth in vitro as well as in vivo.

Pink1/PARK2/mROS-Dependent Mitophagy Initiates the Sensitization of Cancer Cells to Radiation

Autophagy plays a double-edged sword for cancer; particularly, mitophagy plays important roles in the selective degradation of damaged mitochondria. However, whether mitophagy is involved in killing effects of tumor cells by ionizing radiation (IR) and its underlying mechanism remain elusive. The purpose is to evaluate the effects of mitochondrial ROS (mROS) on autophagy after IR; furthermore, we hypothesized that KillerRed (KR) targeting mitochondria could induce mROS generation, subsequent mitochondrial depolarization, accumulation of Pink1, and recruitment of PARK2 to promote the mitophagy. Thereby, we would achieve a new strategy to enhance mROS accumulation and clarify the roles and mechanisms of radiosensitization by KR and IR. Our data demonstrated that IR might cause autophagy of both MCF-7 and HeLa cells, which is related to mitochondria and mROS, and the ROS scavenger N-acetylcysteine (NAC) could reduce the effects. Based on the theory, mitochondrial targeting vector sterile α- and HEAT/armadillo motif-containing protein 1- (Sarm1-) mtKR has been successfully constructed, and we found that ROS levels have significantly increased after light exposure. Furthermore, mitochondrial depolarization of HeLa cells was triggered, such as the decrease of Na⁺K⁺ ATPase, Ca²⁺Mg²⁺ ATPase, and mitochondrial respiratory complex I and III activities, and mitochondrial membrane potential (MMP) has significantly decreased, and voltage-dependent anion channel 1 (VDAC1) protein has significantly increased in the mitochondria. Additionally, HeLa cell proliferation was obviously inhibited, and the cell autophagic rates dramatically increased, which referred to the regulation of the Pink1/PARK2 pathway. These results indicated that mitophagy induced by mROS can initiate the sensitization of cancer cells to IR and might be regulated by the Pink1/PARK2 pathway.

Multi-omics analyses of human colorectal cancer revealed three mitochondrial genes potentially associated with poor outcomes of patients

BACKGROUND

The identification of novel functional biomarkers is essential for recognizing high-risk patients, predicting recurrence, and searching for appropriate treatment. However, no prognostic biomarker has been applied for colorectal cancer (CRC) in the clinic.

METHODS

Integrated with transcriptomic data from public databases, multi-omics examinations were conducted to search prognostic biomarkers for CRC. Moreover, the potential biological functions and regulatory mechanism of these predictive genes were also explored.

RESULTS

In this study, we revealed that three mitochondrial genes were associated with the poor prognosis of CRC. Integrated analyses of transcriptome and proteome of CRC patients disclosed numerous down-regulated mitochondrial genes at both mRNA and protein levels, suggesting a vital role of mitochondria in carcinogenesis. Combined with the bioinformatics studies of transcriptomic datasets of 538 CRC patients, three mitochondrial prognostic genes were eventually selected out, including HIGD1A, SUCLG2, and SLC25A24. The expression of HIGD1A exhibited a significant reduction in two subtypes of adenoma and six subtypes of CRC, while the down-regulation of SUCLG2 and SLC25A24 showed more advantages in rectal mucinous adenocarcinoma. Moreover, we unveiled that these three genes had common expressions and might collaboratively participate in the synthesis of ribosomes. Our original multi-omics datasets, including DNA methylation, structural variants, chromatin accessibility, and phosphoproteome, further depicted the altered modifications on their potential transcriptional factors.

CONCLUSIONS

In summary, HIGD1A, SUCLG2, and SLC25A24 might serve as predictive biomarkers for CRC. The biological activities they involved in and their upstream regulators we uncovered would provide a functional context for the further-in-depth mechanism study.

Mitochondrial Ca2+ Signaling in Health, Disease and Therapy

The divalent cation calcium (Ca²⁺) is considered one of the main second messengers inside cells and acts as the most prominent signal in a plethora of biological processes. Its homeostasis is guaranteed by an intricate and complex system of channels, pumps, and exchangers. In this context, by regulating cellular Ca²⁺ levels, mitochondria control both the uptake and release of Ca²⁺. Therefore, at the mitochondrial level, Ca²⁺ plays a dual role, participating in both vital physiological processes (ATP production and regulation of mitochondrial metabolism) and pathophysiological processes (cell death, cancer progression and metastasis). Hence, it is not surprising that alterations in mitochondrial Ca²⁺ (mCa²⁺) pathways or mutations in Ca²⁺ transporters affect the activities and functions of the entire cell. Indeed, it is widely recognized that dysregulation of mCa²⁺ signaling leads to various pathological scenarios, including cancer, neurological defects and cardiovascular diseases (CVDs). This review summarizes the current knowledge on the regulation of mCa²⁺ homeostasis, the related mechanisms and the significance of this regulation in physiology and human diseases. We also highlight strategies aimed at remedying mCa²⁺ dysregulation as promising therapeutical approaches.

Exploiting S-nitrosylation for cancer therapy: facts and perspectives

S-nitrosylation, the post-translational modification of cysteines by nitric oxide, has been implicated in several cellular processes and tissue homeostasis. As a result, alterations in the mechanisms controlling the levels of S-nitrosylated proteins have been found in pathological states. In the last few years, a role in cancer has been proposed, supported by the evidence that various oncoproteins undergo gain- or loss-of-function modifications upon S-nitrosylation. Here, we aim at providing insight into the current knowledge about the role of S-nitrosylation in different aspects of cancer biology and report the main anticancer strategies based on: (i) reducing S-nitrosylation-mediated oncogenic effects, (ii) boosting S-nitrosylation to stimulate cell death, (iii) exploiting S-nitrosylation through synthetic lethality.

MAPK1/3 kinase-dependent ULK1 degradation attenuates mitophagy and promotes breast cancer bone metastasis

The function of mitophagy in cancer is controversial. ULK1 is critical for induction of macroautophagy/autophagy and has a more specific role in mitophagy in response to hypoxia. Here, we show that ULK1 deficiency induces an invasive phenotype of breast cancer cells under hypoxia and increases osteolytic bone metastasis. Mechanistically, ULK1 depletion attenuates mitophagy ability during hypoxia. As a result, the accumulation of damaged, ROS-generating mitochondria leads to activation of the NLRP3 inflammasome, which induces abnormal soluble cytokines secretion, then promotes the differentiation and maturation of osteoclasts, and ultimately results in bone metastasis. Notably, phosphorylation of ULK1 by MAPK1/ERK2-MAPK3/ERK1 kinase triggers its interaction with BTRC and subsequent K48-linked ubiquitination and proteasome degradation. Also, a clearly negative correlation between the expression levels of ULK1 and p-MAPK1/3 was observed in human breast cancer tissues. The MAP2K/MEK inhibitor trametinib is sufficient to restore mitophagy function via upregulation of ULK1, leading to inhibition of NLRP3 inflammasome activation, thereby reduces bone metastasis. These results indicate that ULK1 knockout-mediated mitophagy defect promotes breast cancer bone metastasis and provide evidence to explore MAP2K/MEK- MAPK1/3 pathway inhibitors for therapy, especially in cancers displaying low levels of ULK1.Abbreviations: ATG: autophagy-related; Baf A1: bafilomycin A₁; BTRC/β-TrCP: beta-transducin repeat containing E3 ubiquitin protein ligase; CHX: cycloheximide; CM: conditioned media; FBXW7/FBW7: F-box and WD repeat domain containing 7; MAPK1: mitogen-activated protein kinase 1; MTDR: MitoTracker Deep Red; mtROS: mitochondrial reactive oxygen species; microCT: micro-computed tomography; mtROS: mitochondrial reactive oxygen species; OCR: oxygen consumption rate; SQSTM1: sequestosome 1; ACP5/TRAP: acid phosphatase, tartrate resistant; ULK1: unc-51 like autophagy activating kinase 1.

Cell-free nucleic acid patterns in disease prediction and monitoring-hype or hope?

Interest in the use of cell-free nucleic acids (CFNAs) as clinical non-invasive biomarker panels for prediction and prevention of multiple diseases has greatly increased over the last decade. Indeed, circulating CFNAs are attributable to many physiological and pathological processes such as imbalanced stress conditions, physical activities, extensive apoptosis of different origin, systemic hypoxic-ischemic events and tumour progression, amongst others. This article highlights the involvement of circulating CFNAs in local and systemic processes dealing with the question, whether specific patterns of CFNAs in blood, their detection, quantity and quality (such as their methylation status) might be instrumental to predict a disease development/progression and could be further utilised for accompanying diagnostics, targeted prevention, creation of individualised therapy algorithms, therapy monitoring and prognosis. Presented considerations conform with principles of 3P medicine and serve for improving individual outcomes and cost efficacy of medical services provided to the population.

Mitocanic Di- and Triterpenoid Rhodamine B Conjugates

The combination of the “correct” triterpenoid, the “correct” spacer and rhodamine B (RhoB) seems to be decisive for the ability of the conjugate to accumulate in mitochondria. So far, several triterpenoid rhodamine B conjugates have been prepared and screened for their cytotoxic activity. To obtain cytotoxic compounds with EC₅₀ values in a low nano-molar range combined with good tumor/non-tumor selectivity, the Rho B unit has to be attached via an amine spacer to the terpenoid skeleton. To avoid spirolactamization, secondary amines have to be used. First results indicate that a homopiperazinyl spacer is superior to a piperazinyl spacer. Hybrids derived from maslinic acid or tormentic acid are superior to those from oleanolic, ursolic, glycyrrhetinic or euscaphic acid. Thus, a tormentic acid-derived RhoB conjugate 32, holding a homopiperazinyl spacer can be regarded, at present, as the most promising candidate for further biological studies.

Mitochondria as the decision makers for cancer cell fate: from signaling pathways to therapeutic strategies

As pivotal players in cellular metabolism, mitochondria have a double-faceted role in the final decision of cell fate. This is true for all cell types, but it is even more important and intriguing in the cancer setting. Mitochondria regulate cell fate in many diverse ways: through metabolism, by producing ATP and other metabolites deemed vital or detrimental for cancer cells; through the regulation of Ca²⁺ homeostasis, especially by the joint participation of the endoplasmic reticulum in a membranous tethering system for Ca²⁺ signaling called mitochondria-ER associated membranes (MAMs); and by regulating signaling pathways involved in the survival of cancer cells such as mitophagy. Recent studies have shown that mitochondria can also play a role in the regulation of inflammatory pathways in cancer cells, for example, through the release of mitochondrial DNA (mtDNA) involved in the activation of the cGAS-cGAMP-STING pathway. In this review, we aim to explore the role of mitochondria as decision makers in fostering cancer cell death or survival depending on the tumor cell stage and describe novel anticancer therapeutic strategies targeting mitochondria.

Receptor for Advanced Glycation End Products Acts as a Fuel to Colorectal Cancer Development

Receptor for advanced glycation end-products (RAGE) is a multiligand binding and single-pass transmembrane protein taken in diverse chronic inflammatory conditions. RAGE behaves as a pattern recognition receptor, which binds and is engaged in the cellular response to a variety of damage-associated molecular pattern molecules, as well as HMGB1, S100 proteins, and AGEs (advanced glycation end-products). The RAGE activation turns out to a formation of numerous intracellular signaling mechanisms, resulting in the progression and prolongation of colorectal carcinoma (CRC). The RAGE expression correlates well with the survival of colon cancer cells. RAGE is involved in the tumorigenesis, which increases and develops well in the stressed tumor microenvironment. In this review, we summarized downstream signaling cascade activated by the multiligand activation of RAGE, as well as RAGE ligands and their sources, clinical studies, and tumor markers related to RAGE particularly in the inflammatory tumor microenvironment in CRC. Furthermore, the role of RAGE signaling pathway in CRC patients with diabetic mellitus is investigated. RAGE has been reported to drive assorted signaling pathways, including activator protein 1, nuclear factor-κB, signal transducer and activator of transcription 3, SMAD family member 4 (Smad4), mitogen-activated protein kinases, mammalian target of rapamycin, phosphoinositide 3-kinases, reticular activating system, Wnt/β-catenin pathway, and Glycogen synthase kinase 3β, and even microRNAs.

Updated Understanding of Cancer as a Metabolic and Telomere-Driven Disease, and Proposal for Complex Personalized Treatment, a Hypothesis

In this review, we propose a holistic approach to understanding cancer as a metabolic disease. Our search for relevant studies in medical databases concludes that cancer cells do not evolve directly from normal healthy cells. We hypothesize that aberrant DNA damage accumulates over time-avoiding the natural DNA controls that otherwise repair or replace the rapidly replicating cells. DNA damage starts to accumulate in non-replicating cells, leading to senescence and aging. DNA damage is linked with genetic and epigenetic factors, but the development of cancer is favored by telomerase activity. Evidence indicates that telomere length is affected by chronic inflammations, alterations of mitochondrial DNA, and various environmental factors. Emotional stress also influences telomere length. Chronic inflammation can cause oxidative DNA damage. Oxidative stress, in turn, can trigger mitochondrial changes, which ultimately alter nuclear gene expression. This vicious cycle has led several scientists to view cancer as a metabolic disease. We have proposed complex personalized treatments that seek to correct multiple changes simultaneously using a psychological approach to reduce chronic stress, immune checkpoint therapy with reduced doses of chemo and radiotherapy, minimal surgical intervention, if any, and mitochondrial metabolic reprogramming protocols supplemented by intermittent fasting and personalized dietary plans without interfering with the other therapies.

Pharmacological Activity, Pharmacokinetics, and Toxicity of Timosaponin AIII, a Natural Product Isolated From Anemarrhena asphodeloides Bunge: A Review

Anemarrhena asphodeloides Bunge is a famous Chinese Materia Medica and has been used in traditional Chinese medicine for more than two thousand years. Steroidal saponins are important active components isolated from A. asphodeloides Bunge. Among which, the accumulation of numerous experimental studies involved in Timosaponin AIII (Timo AIII) draws our attention in the recent decades. In this review, we searched all the scientific literatures using the key word "timosaponin AIII" in the PubMed database update to March 2020. We comprehensively summarized the pharmacological activity, pharmacokinetics, and toxicity of Timo AIII. We found that Timo AIII presents multiple-pharmacological activities, such as anti-cancer, anti-neuronal disorders, anti-inflammation, anti-coagulant, and so on. And the anti-cancer effect of Timo AIII in various cancers, especially hepatocellular cancer and breast cancer, is supposed as its most potential activity. The anti-inflammatory activity of Timo AIII is also beneficial to many diseases. Moreover, VEGFR, X-linked inhibitor of apoptosis protein (XIAP), B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1), thromboxane (Tx) A2 receptor, mTOR, NF-κB, COX-2, MMPs, acetylcholinesterase (AChE), and so on are identified as the crucial pharmacological targets of Timo AIII. Furthermore, the hepatotoxicity of Timo AIII was most concerned, and the pharmacokinetics and toxicity of Timo AIII need further studies in diverse animal models. In conclusion, Timo AIII is potent as a compound or leading compound for further drug development while still needs in-depth studies.

Increase of mtDNA number and its mutant copies in rat brain after exposure to 150 MeV protons

Proton beam therapy is widely used for treating brain tumor. Despite the efficacy of treatment, the use of this therapy has met some limitations associated with possible damage to normal brain tissues located beyond the tumor site. In this context, the exploration of the harmful effects of protons on the normal brain tissues is of particular interest. We have investigated changes in the total mitochondrial DNA (mtDNA) copy number and identified mtDNA mutant copies in three brain regions (the hippocampus, cortex and cerebellum) of rats after irradiation their whole-head with 150 MeV protons at doses of 3 and 5 Gy. The study was performed in 2-months old male Spraque Dawley rats (n = 5 each group). The mtDNA copy numbers were determined by real-time PCR. The level of mtDNA heteroplasmy was estimated using Surveyor nuclease technology. Our results show that after head exposure to protons, levels of mtDNA copy number in three rat brain regions increase significantly as the levels of mtDNA mutant copies increase. The most significant elevation is observed in the hippocampus. In conclusion, an increase in mtDNA mutant copies may contribute to mitochondrial dysfunction accompanied by increased oxidative stress in different brain regions and promote the development of neurodegenerative diseases and the induction of carcinogenesis.