Mitochondrial dynamics and cancer

Bridging the divide: unveiling mutual immunological pathways of cancer and pregnancy

The juxtaposition of two seemingly disparate physiological phenomena within the human body-namely, cancer and pregnancy-may offer profound insights into the intricate interplay between malignancies and the immune system. Recent investigations have unveiled striking similarities between the pivotal processes underpinning fetal implantation and successful gestation and those governing tumor initiation and progression. Notably, a confluence of features has emerged, underscoring parallels between the microenvironment of tumors and the maternal-fetal interface. These shared attributes encompass establishing vascular networks, cellular mobilization, recruitment of auxiliary tissue components to facilitate continued growth, and, most significantly, the orchestration of immune-suppressive mechanisms.Our particular focus herein centers on the phenomenon of immune suppression and its protective utility in both of these contexts. In the context of pregnancy, immune suppression assumes a paramount role in shielding the semi-allogeneic fetus from the potentially hostile immune responses of the maternal host. In stark contrast, in the milieu of cancer, this very same immunological suppression fosters the transformation of the tumor microenvironment into a sanctuary personalized for the neoplastic cells.Thus, the striking parallels between the immunosuppressive strategies deployed during pregnancy and those co-opted by malignancies offer a tantalizing reservoir of insights. These insights promise to inform novel avenues in the realm of cancer immunotherapy. By harnessing our understanding of the immunological events that detrimentally impact fetal development, a knowledge grounded in the context of conditions such as preeclampsia or miscarriage, we may uncover innovative immunotherapeutic strategies to combat cancer.

Constructing and Evaluating a Mitophagy-Related Gene Prognostic Model: Implications for Immune Landscape and Tumor Biology in Lung Adenocarcinoma

Mitophagy, a conserved cellular mechanism, is crucial for cellular homeostasis through the selective clearance of impaired mitochondria. Its emerging role in cancer development has sparked interest, particularly in lung adenocarcinoma (LUAD). Our study aimed to construct a risk model based on mitophagy-related genes (MRGs) to predict survival outcomes, immune response, and chemotherapy sensitivity in LUAD patients. We mined the GeneCards database to identify MRGs and applied LASSO/Cox regression to formulate a prognostic model. Validation was performed using two independent Gene Expression Omnibus (GEO) cohorts. Patients were divided into high- and low-risk categories according to the median risk score. The high-risk group demonstrated significantly reduced survival. Multivariate Cox analysis confirmed the risk score as an independent predictor of prognosis, and a corresponding nomogram was developed to facilitate clinical assessments. Intriguingly, the risk score correlated with immune infiltration levels, oncogenic expression profiles, and sensitivity to anticancer agents. Enrichment analyses linked the risk score with key oncological pathways and biological processes. Within the model, MTERF3 emerged as a critical regulator of lung cancer progression. Functional studies indicated that the MTERF3 knockdown suppressed the lung cancer cell proliferation and migration, enhanced mitophagy, and increased the mitochondrial superoxide production. Our novel prognostic model, grounded in MRGs, promises to refine therapeutic strategies and prognostication in lung cancer management.

Combination Organelle Mitochondrial Endoplasmic Reticulum Therapy (COMET) for Multidrug Resistant Breast Cancer

It is time for the story of mitochondria and intracellular communication in multidrug resistant cancer to be rewritten. Herein we characterize the extent and cellular advantages of mitochondrial network fusion in multidrug resistant (MDR) breast cancer and have designed a novel nanomedicine that disrupts mitochondrial network fusion and systematically manipulates organelle fusion and function. Combination Organelle Mitochondrial Endoplasmic reticulum Therapy (COMET) is an innovative translational nanomedicine for treating MDR triple negative breast cancer (TNBC) that has superior safety and equivalent efficacy to the current standard of care (paclitaxel). Our study has demonstrated that the increased mitochondrial networks in MDR TNBC contribute to apoptotic resistance and network fusion is mediated by mitofusin2 (MFN2) on the outer mitochondrial membrane. COMET consists of three components; Mitochondrial Network Disrupting (MiND) nanoparticles (NPs) that are loaded with an anti-MFN2 peptide, tunicamycin, and Bam7. The therapeutic rationale of COMET is to reduce the apoptotic threshold in MDR cells with MiND NPs, followed by inducing the endoplasmic reticulum mediated unfolded protein response (UPR) by stressing MDR cells with tunicamycin, and finally, directly inducing mitochondrial apoptosis with Bam7 which is a specific bcl-2 Bax activator. MiND NPs are PEGylated liposomes with the 21 amino acid (2577.98 MW) anti-MFN2 peptide compartmentalized in the aqueous core. Hypoxia (0.5% oxygen) was used to create MDR derivatives of MDA-MB-231 cells and BT-549 cells. Mitochondrial networks were quantified using 3D analysis of 60× live cell images acquired with a Keyence BZ-X710 microscope and MiND NPs effectively fragmented mitochondrial networks in drug sensitive and MDR TNBC cells. The IC50 values, combination index, and dose reduction index derived from dose response studies demonstrate that MiND NPs decrease the apoptotic threshold of both drug sensitive and MDR TNBC cells and COMET is a synergistic drug combination. Complex V (ATP synthase) extracted from bovine cardiac mitochondria was used to assess the effect of MiND NPs on OXPHOS; both MiND NPs and anti-MFN2 peptide solution significantly decrease the activity of mitochondrial complex V and decrease the capacity of OXPHOS. A BacMam viral vector based fluorescent biosensor was used to quantify the unfolded protein response (UPR) at the level of the endoplasmic reticulum and tunicamycin specifically induces the UPR in drug sensitive and MDR TNBC cells. A caspase 3 colorimetric assay demonstrated that the synergistic triple drug combination of COMET increases the ability of Bam7 to specifically induce apoptosis. Dose limiting toxicity and off target effects are a significant challenge for current chemotherapy regimens including paclitaxel. COMET has significantly lower cytotoxicity than paclitaxel in human embryonic kidney epithelial cells and has the potential to fulfill the clinical need for safer cancer therapeutics. COMET is a promising early stage translational nanomedicine for treating MDR TNBC. Manipulating intracellular communication and organelle fusion is a novel approach to treating MDR cancer. The data from this study has rewritten the story of mitochondria, organelle fusion, and intracellular communication and by targeting this intersection, COMET is an exciting new chapter in cancer therapeutics that could transform the clinical outcome of MDR TNBC.

Therapeutic Targeting of Mitochondrial Plasticity and Redox Control to Overcome Cancer Chemoresistance

Significance: Mitochondria are subcellular organelles performing essential metabolic functions contributing to cellular bioenergetics and regulation of cell growth or death. The basic mitochondrial function in fulfilling the need for cell growth and vitality is evidenced whereby cancer cells with depleted mitochondrial DNA (rho zero, p0 cells) no longer form tumors until newly recruited mitochondria are internalized into the rho zero cells. Herein lies the absolute dependency on mitochondria for tumor growth. Hence, mitochondria are key regulators of cell death (by apoptosis, necroptosis, or other forms of cell death) and are, therefore, important targets for anticancer therapy. Recent Advances: Mitochondrial plasticity regulating their state of fusion or fission is key to the chemoresistance properties of cancer cells by promoting pro-survival pathways, enabling the mitochondria to mitigate against the cellular stresses and extreme conditions within the tumor microenvironment caused by chemotherapy, hypoxia, or oxidative stress. Critical Issues: This review discusses many characteristics of mitochondria, the processes and pathways controlling the dynamic changes occurring in the morphology of mitochondria, the roles of reactive oxygen species, and their relationship with mitochondrial fission or fusion. It also examines the relationship of redox to mitophagy when mitochondria become compromised and its effect on cancer cell survival, stemness, and the changes accompanying malignant progression from primary tumors to metastatic disease. Future Directions: A challenging question that arises is whether the changes in mitochondrial dynamics and their regulation can provide opportunities for improving drug targeting during cancer treatment and enhancing survival outcomes. Antioxid. Redox Signal. 39, 591-619.

Photochemical Targeting of Mitochondria to Overcome Chemoresistance in Ovarian Cancer †

Ovarian cancer is the most lethal gynecologic malignancy with a stubborn mortality rate of ~65%. The persistent failure of multiline chemotherapy, and significant tumor heterogeneity, has made it challenging to improve outcomes. A target of increasing interest is the mitochondrion because of its essential role in critical cellular functions, and the significance of metabolic adaptation in chemoresistance. This review describes mitochondrial processes, including metabolic reprogramming, mitochondrial transfer and mitochondrial dynamics in ovarian cancer progression and chemoresistance. The effect of malignant ascites, or excess peritoneal fluid, on mitochondrial function is discussed. The role of photodynamic therapy (PDT) in overcoming mitochondria-mediated resistance is presented. PDT, a photochemistry-based modality, involves the light-based activation of a photosensitizer leading to the production of short-lived reactive molecular species and spatiotemporally confined photodamage to nearby organelles and biological targets. The consequential effects range from subcytotoxic priming of target cells for increased sensitivity to subsequent treatments, such as chemotherapy, to direct cell killing. This review discusses how PDT-based approaches can address key limitations of current treatments. Specifically, an overview of the mechanisms by which PDT alters mitochondrial function, and a summary of preclinical advancements and clinical PDT experience in ovarian cancer are provided.

Super-Resolution Quantification of T2DM-Induced Mitochondrial Morphology Changes and Their Implications in Pharmacodynamics of Metformin and Sorafenib

Mitochondria, as the powerhouse of cells, are involved in various processes of cellular homeostasis, especially energy metabolism. The morphology of mitochondria is a critical indicator for their functions, referring to mitochondrial fusion and fission. Here, we performed structured illumination microscopy (SIM) to measure the mitochondrial morphology in living cells. Benefitting from its nano-scale resolution, this SIM-based strategy can quantify the fusion and fission of mitochondria with high sensitivity. Furthermore, as type 2 diabetes mellitus (T2DM) is caused by a disorder of energy substrate utilization, this strategy has the potential to study T2DM by analyzing the mitochondrial morphology of insulin-resistant (IR) cells. With SIM, we found that mitochondrial fission was increased in IR MRC-5, LO2, FHs 74 Int, and HepG2 cells but not in IR Huh7 cells with high-invasiveness ability. Furthermore, we found that metformin could inhibit mitochondrial fission in IR cells, and sorafenib could promote mitochondrial fusion in HepG2 cancer cells, especially in those IR cells. To conclude, mitochondrial fission is involved in T2DM, and cancer cells with high-invasiveness ability may be equipped with stronger resistance to energy metabolism disorder. In addition, the pharmacodynamics of metformin and sorafenib in cancer may be related to the inhibition of mitochondrial fission, especially for patients with T2DM.

The functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination

Ubiquitination of substrates usually have two fates: one is degraded by 26S proteasome, and the other is non-degradative ubiquitination modification which is associated with cell cycle regulation, chromosome inactivation, protein transportation, tumorigenesis, achondroplasia, and neurological diseases. Cullin3 (CUL3), a scaffold protein, binding with the Bric-a-Brac-Tramtrack-Broad-complex (BTB) domain of substrates recognition adaptor and RING-finger protein 1 (RBX1) form ubiquitin ligases (E3). Based on the current researches, this review has summarized the functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination.

The Synergistic Cytotoxic Effects of GW5074 and Sorafenib by Impacting Mitochondrial Functions in Human Colorectal Cancer Cell Lines

Colorectal cancer (CRC) ranks third in the United States for incidence or mortality. Surgical resection is the primary treatment for patients at an early stage, while patients with advanced and metastatic CRC receive combined treatment with chemotherapy, radiotherapy, or targeted therapy. C-RAF plays a key role in maintaining clonogenic and tumorigenic capacity in CRC cells and it might be a potential therapeutic target for CRC. Sorafenib is a popular oral multi-kinase inhibitor, including a B-RAF inhibitor that targets the RAF-MEK-ERK pathway. Sorafenib, as a single agent, has tumor-suppressing efficacy, but its clinical application is limited due to many complex drug resistance mechanisms and side effects. GW5074 is one of the C-RAF inhibitors and has the potential to enhance the efficacy of existing cancer chemotherapies. In this study, we investigated whether the combination of sorafenib with GW5074 could reduce the dosage of sorafenib and enhance its tumor-suppressive effect in two CRC cell lines, HCT116 and LoVo cells. Our findings demonstrate that GW5074 can potentiate the cytotoxicity of sorafenib and dramatically reduce the half-maximal inhibitory concentration (IC50) dose of sorafenib from 17 and 31 µM to 0.14 and 0.01 µM in HCT116 and LoVo cells, respectively. GW5074, similar to sorafenib, suppressed the cellular proliferation and induced cellular apoptosis and cytosolic ROS, but had no further enhancement on the above-mentioned effects when combined with sorafenib. The synergistic effects of GW5074 and sorafenib were mainly found in mitochondrial functions, including ROS generation, membrane potential disruption, and fission–fusion dynamics, which were examined by using the flow cytometry analysis. In summary, the C-RAF inhibitor GW5074 might potentiate the cytotoxicity of the B-RAF inhibitor sorafenib mediated through mitochondrial dysfunctions, suggesting that GW5074 potentially serves as a sensitizer for sorafenib application to reduce the risk of drug resistance of CRC treatment. Our findings also provide novel insights on using C-RAF inhibitors combined with sorafenib, the current CRC therapeutic drug choice, in CRC treatment.

DRP1 contributes to head and neck cancer progression and induces glycolysis through modulated FOXM1/MMP12 axis

Abnormal DRP1 expression has been identified in a variety of human cancers. However, the prognostic potential and mechanistic role of DRP1 in head and neck cancer (HNC) are currently poorly understood. Here, we demonstrated a significant upregulation of DRP1 in HNC tissues, and that DRP1 expression correlates with poor survival of HNC patients. Diminished DRP1 expression suppressed tumor growth and metastasis in both in vitro and in vivo models. DRP1 expression was positively correlated with FOXM1 and MMP12 expression in HNC patient samples, suggesting pathological relevance in the context of HNC development. Moreover, DRP1 depletion affected aerobic glycolysis through the downregulation of glycolytic genes, and overexpression of MMP12 in DRP1‐depleted cells could help restore glucose consumption and lactate production. Using ChIP‐qPCR, we showed that DRP1 modulates FOXM1 expression, which can enhance MMP12 transcription by binding to its promoter. We also showed that miR‐575 could target 3’UTR of DRP1 mRNA and suppress DRP1 expression. Collectively, our study provides mechanistic insights into the role of DRP1 in HNC and highlights the potential of targeting the miR‐575/DRP1/FOXM1/MMP12 axis as a novel therapy for the prevention of HNC progression.

L22 ribosomal protein is involved in dynamin-related protein 1-mediated gastric carcinoma progression

Mitochondrial fission depends on dynamin-related protein 1 (Drp1) guanosine triphosphatase activity. Although there is some association between Drp1 and gastric cancer, the detailed mechanism remains largely unknown. In this study, the elevation of Drp1 was observed in human gastric carcinoma specimens including gastric mixed adenocarcinoma tissues, gastric intestinal-type adenocarcinoma tissues, and human gastric cancer cells compared to normal control, but not in diffuse gastric adenocarcinoma tissues. Gastric cancer patients with high Drp1 harbored advanced pathological stages and poor progression-free survival probability compared to those with low Drp1. Mdivi-1-mediated inactivation of Drp1 robustly inhibited cell viability and tumor growth but conversely induced cell apoptotic events in vitro and in vivo. Based on the Encyclopedia of RNA Interactomes Starbase, L22 ribosomal protein (RPL22) was recognized as the potential downstream oncogene of Drp1. Clinically, the significant correlation of Drp1 and RPL22 was also verified. Mechanistically, Drp1 inactivation did not affect the accumulation of RPL22 in gastric carcinoma. However, the intracellular distribution of RPL22 had an endonuclear location in Drp1-inactivated tumors. Of note, Drp1 inactivation notably reduced the expression of cytoplasmic RPL22 and increased its nuclear level in gastric cancer cells. Collectively, Drp1 had high levels in human gastric carcinoma specimens and could serve as a potential diagnostic and prognostic biomarker in gastric carcinoma. The Drp1 inactivation-mediated anti-proliferative and pro-apoptosis effects on gastric cancer were possibly associated with nuclear import of RPL22. This knowledge may provide new therapeutic tools for treating gastric carcinoma via targeting mitochondria-related ribosome pathway.

Mitochondrial Dynamics Mediated by DRP1 and MFN2 Contributes to Cisplatin Chemoresistance in Human Ovarian Cancer SKOV3 cells

Cisplatin (DDP) is the first-line chemotherapeutic agent for ovarian cancer. However, the development of DDP resistance seriously influences the chemotherapeutic effect and prognosis of ovarian cancer. It was reported that DDP can directly impinge on the mitochondria and activate the intrinsic apoptotic pathway. Herein, the role of mitochondrial dynamics in DDP chemoresistance in human ovarian cancer SKOV3 cells was investigated. In DDP-resistant SKOV3/DDP cells, mitochondrial fission protein DRP1 was down-regulated, while mitochondrial fusion protein MFN2 was up-regulated. In accordance with the expression of DRP1 and MFN2, the average mitochondrial length was significantly increased in SKOV3/DDP cells. In DDP-sensitive parental SKOV3 cells, downregulation of DRP1 and upregulation of mitochondrial fusion proteins including MFN1,2 and OPA1 occurred at day 2~6 under cisplatin stress. Knockdown of DRP1 or overexpression of MFN2 promoted the resistance of SKOV3 cells to cisplatin. Intriguingly, weaker migration capability and lower ATP level were detected in SKOV3/DDP cells. Respective knockdown of DRP1 in parental SKOV3 cells or MFN2 in SKOV3/DDP cells using siRNA efficiently reversed mitochondrial dynamics, migration capability and ATP level. Moreover, MFN2 siRNA significantly aggravated the DDP-induced ROS production, mitochondrial membrane potential disruption, expression of pro-apoptotic protein BAX and Cleaved Caspase-3/9 in SKOV3/DDP cells. In contrast, DRP1 siRNA alleviated DDP-induced ROS production, mitochondrial membrane potential disruption, expression of pro-apoptotic protein BAX and Cleaved Caspase-3/9 in SKOV3 cells. Thus, these results indicate that mitochondrial dynamics mediated by DRP1 and MFN2 contributes to the development of DDP resistance in ovarian cancer cells, and will also provide a new strategy to prevent chemoresistance in ovarian cancer by targeting mitochondrial dynamics.

Identification of miRNAs That Mediate Protective Functions of Anti-Cancer Drugs During White Matter Ischemic Injury

We have previously shown that two anti-cancer drugs, CX-4945 and MS-275, protect and preserve white matter (WM) architecture and improve functional recovery in a model of WM ischemic injury. While both compounds promote recovery, CX-4945 is a selective Casein kinase 2 (CK2) inhibitor and MS-275 is a selective Class I histone deacetylase (HDAC) inhibitor. Alterations in microRNAs (miRNAs) mediate some of the protective actions of these drugs. In this study, we aimed to (1) identify miRNAs expressed in mouse optic nerves (MONs); (2) determine which miRNAs are regulated by oxygen glucose deprivation (OGD); and (3) determine the effects of CX-4945 and MS-275 treatment on miRNA expression. RNA isolated from MONs from control and OGD-treated animals with and without CX-4945 or MS-275 treatment were quantified using NanoString nCounter^® miRNA expression profiling. Comparative analysis of experimental groups revealed that 12 miRNAs were expressed at high levels in MONs. OGD upregulated five miRNAs (miR-1959, miR-501-3p, miR-146b, miR-201, and miR-335-3p) and downregulated two miRNAs (miR-1937a and miR-1937b) compared to controls. OGD with CX-4945 upregulated miR-1937a and miR-1937b, and downregulated miR-501-3p, miR-200a, miR-1959, and miR-654-3p compared to OGD alone. OGD with MS-275 upregulated miR-2134, miR-2141, miR-2133, miR-34b-5p, miR-153, miR-487b, miR-376b, and downregulated miR-717, miR-190, miR-27a, miR-1959, miR-200a, miR-501-3p, and miR-200c compared to OGD alone. Interestingly, miR-501-3p and miR-1959 were the only miRNAs upregulated by OGD, and downregulated by OGD plus CX-4945 and MS-275. Therefore, we suggest that protective functions of CX-4945 or MS-275 against WM injury maybe mediated, in part, through miRNA expression.

Nanotherapeutic approaches to target mitochondria in cancer

Treatment of cancer cells exemplifies a difficult test in the light of challenges associated with the nature of cancer cells and the severe side effects too. After making a large number of trials using both traditional and advanced therapies (immunotherapy and hormone therapy), approaches to design new therapies have reached a saturation level. However, nanotechnology-based approaches exhibit higher efficacy and great potential to bypass many of such therapeutic limitations. Because of their higher target specificity, the use of nanoparticles offers incredible potential in cancer therapeutics. Mitochondria, acting as a factory of energy production in cells, reveal an important role in the death as well as the survival of cells. Because of its significant involvement in the proliferation of cancer cells, it is being regarded as an important target for cancer therapeutics. Numerous studies reveal that nanotechnology-based approaches to directly target the mitochondria may help in improving the survival rate of cancer patients. In the current study, we have detailed the significance of mitochondria in the development of cancer phenotype, as well as indicated it as the potential targets for cancer therapy. Our study further highlights the importance of different nanoparticle-based approaches to target mitochondria of cancer cells and the associated outcomes of different studies. Though, nanotechnology-based approaches to target mitochondria of cancer cells demonstrate a potential and efficient way in cancer therapeutics. Yet, further study is needed to overcome the linked limitations.

Mitochondrial nanomedicine: Subcellular organelle-specific delivery of molecular medicines

As mitochondria network together to act as the master sensors and effectors of apoptosis, ATP production, reactive oxygen species management, mitophagy/autophagy, and homeostasis; this organelle is an ideal target for pharmaceutical manipulation. Mitochondrial dysfunction contributes to many diseases, for example, β-amyloid has been shown to interfere with mitochondrial protein import and induce apoptosis in Alzheimer's Disease while some forms of Parkinson's Disease are associated with dysfunctional mitochondrial PINK1 and Parkin proteins. Mitochondrial medicine has applications in the treatment of an array of pathologies from cancer to cardiovascular disease. A challenge of mitochondrial medicine is directing therapies to a subcellular target. Nanotechnology based approaches combined with mitochondrial targeting strategies can greatly improve the clinical translation and effectiveness of mitochondrial medicine. This review discusses mitochondrial drug delivery approaches and applications of mitochondrial nanomedicines. Nanomedicine approaches have the potential to drive the success of mitochondrial therapies into the clinic.

Novel Strategies for Disrupting Cancer-Cell Functions with Mitochondria-Targeted Antitumor Drug-Loaded Nanoformulations

Any variation in normal cellular function results in mitochondrial dysregulation that occurs in several diseases, including cancer. Such processes as oxidative stress, metabolism, signaling, and biogenesis play significant roles in cancer initiation and progression. Due to their central role in cellular metabolism, mitochondria are favorable therapeutic targets for the prevention and treatment of conditions like neurodegenerative diseases, diabetes, and cancer. Subcellular mitochondria-specific theranostic nanoformulations for simultaneous targeting, drug delivery, and imaging of these organelles are of immense interest in cancer therapy. It is a challenging task to cross multiple barriers to target mitochondria in diseased cells. To overcome these multiple barriers, several mitochondriotropic nanoformulations have been engineered for the transportation of mitochondria-specific drugs. These nanoformulations include liposomes, dendrimers, carbon nanotubes, polymeric nanoparticles (NPs), and inorganic NPs. These nanoformulations are made mitochondriotropic by conjugating them with moieties like dequalinium, Mito-Porter, triphenylphosphonium, and Mitochondria-penetrating peptides. Most of these nanoformulations are meticulously tailored to control their size, charge, shape, mitochondriotropic drug loading, and specific cell-membrane interactions. Recently, some novel mitochondria-selective antitumor compounds known as mitocans have shown high toxicity against cancer cells. These selective compounds form vicious oxidative stress and reactive oxygen species cycles within cancer cells and ultimately push them to cell death. Nanoformulations approved by the FDA and EMA for clinical applications in cancer patients include Doxil, NK105, and Abraxane. The novel use of these NPs still faces tremendous challenges and an immense amount of research is needed to understand the proper mechanisms of cancer progression and control by these NPs. Here in this review, we summarize current advancements and novel strategies of delivering different anticancer therapeutic agents to mitochondria with the help of various nanoformulations.

Neuroglobin and mitochondria: The impact on neurodegenerative diseases

Dysfunctional mitochondria have severe consequences on cell functions including Reactive Oxygen Specie (ROS) generation, alteration of mitochondrial signaling, Ca²⁺ buffering, and activation of apoptotic pathway. These dysfunctions are closely linked with degenerative diseases including neurodegeneration. The discovery of neuroglobin (NGB) as an endogenous neuroprotective protein, which effects seem to depend on its mitochondrial localization, could drive new therapeutic strategies against aged-related neurodegenerative diseases. Indeed, high levels of NGB are active against several brain injuries, including neurodegeneration, hypoxia, ischemia, toxicity, and nutrient deprivation opening a new scenario in the comprehension of the relationship between neural pathologies and mitochondrial homeostasis. In this review, we provide the current understanding of the role of mitochondria in neurodegeneration and discuss structural and functional connection between NGB and mitochondria with the purpose of defining a novel mitochondrial-based neuroprotective mechanism(s).

Mechanisms of Cisplatin in Combination with Repurposed Drugs against Human Endometrial Carcinoma Cells

Although endometrial carcinoma is one of the most common gynecological malignancies worldwide, its precise etiology remains unknown. Moreover, no novel adjuvant and/or targeted therapies are currently being developed to achieve greater efficacy for endometrial cancer patients who develop chemotherapeutic drug resistance. In this study, we used three human endometrial cancer cell lines, RL95-2, HEC-1-A, and KLE, to investigate the responsiveness of cisplatin alone and in combination with potential repurposed drugs. We first found that RL95-2 cells were more sensitive to cisplatin than HEC-1-A or KLE cells. The cytotoxicity of cisplatin in RL95-2 cells may reflect its ability to perturb the cell cycle, reactive oxygen species production and autophagy as well as to induce senescence and DNA damage. Similar effects, although not DNA damage, were also observed in HEC-1-A and KLE cells. In addition, downregulation of p53 and/or cyclin D1 may also impact the responsiveness of HEC-1-A and KLE cells to cisplatin. We also observed that resveratrol, trichostatin A (TSA), caffeine, or digoxin increased the apoptotic process of cisplatin toward RL95-2 cells, while amiodarone or TSA increased its apoptotic process toward HEC-1-A cells. The combination index supported the assertion that the combination of cisplatin with caffeine, amiodarone, resveratrol, metformin, digoxin, or TSA increases the cytotoxicity of cisplatin in HEC-1-A cells. These findings suggest potential strategies for enhancing the efficacy of cisplatin to overcome drug resistance in endometrial carcinoma patients.

Bloom syndrome DNA helicase deficiency is associated with oxidative stress and mitochondrial network changes

Bloom Syndrome (BS; OMIM #210900; ORPHA #125) is a rare genetic disorder that is associated with growth deficits, compromised immune system, insulin resistance, genome instability and extraordinary predisposition to cancer. Most efforts thus far have focused on understanding the role of the Bloom syndrome DNA helicase BLM as a recombination factor in maintaining genome stability and suppressing cancer. Here, we observed increased levels of reactive oxygen species (ROS) and DNA base damage in BLM-deficient cells, as well as oxidative-stress-dependent reduction in DNA replication speed. BLM-deficient cells exhibited increased mitochondrial mass, upregulation of mitochondrial transcription factor A (TFAM), higher ATP levels and increased respiratory reserve capacity. Cyclin B1, which acts in complex with cyclin-dependent kinase CDK1 to regulate mitotic entry and associated mitochondrial fission by phosphorylating mitochondrial fission protein Drp1, fails to be fully degraded in BLM-deficient cells and shows unscheduled expression in G1 phase cells. This failure to degrade cyclin B1 is accompanied by increased levels and persistent activation of Drp1 throughout mitosis and into G1 phase as well as mitochondrial fragmentation. This study identifies mitochondria-associated abnormalities in Bloom syndrome patient-derived and BLM-knockout cells and we discuss how these abnormalities may contribute to Bloom syndrome.

Revisiting Mitochondria Scored Cancer Progression and Metastasis

Simple Summary

The indispensible role of mitochondria has been described over a century ago by Otto Warburg which has been serving the fields of cell biology and cancer biology immensely. Mitochondria are the principal site for vital mechanisms which vastly dictate the physiology. The intricacy of mitochondria’s role cancer have been noticed and well addressed in recent times. The underlying mechanisms are surfacing to unveil the nature of mitochondria and its participation in tumor cell motility and metastasis. This addressing may unravel novel therapeutic options. This review summarizes and reweighs the key aspects like underlying and emerging mechanisms which might be useful in designing novel chemotherapy.

Abstract

The Warburg effect has immensely succored the study of cancer biology, especially in highlighting the role of mitochondria in cancer stemness and their benefaction to the malignancy of oxidative and glycolytic cancer cells. Mitochondrial genetics have represented a focal point in cancer therapeutics due to the involvement of mitochondria in programmed cell death. The mitochondrion has been well established as a switch in cell death decisions. The mitochondrion’s instrumental role in central bioenergetics, calcium homeostasis, and translational regulation has earned it its fame in metastatic dissemination in cancer cells. Here, we revisit and review mechanisms through which mitochondria influence oncogenesis and metastasis by underscoring the oncogenic mitochondrion that is capable of transferring malignant capacities to recipient cells.

Marf-mediated mitochondrial fusion is imperative for the development and functioning of indirect flight muscles (IFMs) in drosophila

Dynamic changes in mitochondrial shape and size are vital for mitochondrial health and for tissue development and function. Adult Drosophila indirect flight muscles contain densely packed mitochondria. We show here that mitochondrial fusion is critical during early muscle development (in pupa) and that silencing of the outer mitochondrial membrane fusion gene, Marf, in muscles results in smaller mitochondria that are functionally defective. This leads to abnormal muscle development resulting in muscle dysfunction in adult flies. However, post-developmental silencing of Marf has no obvious effects on mitochondrial and muscle phenotype in adult flies, indicating the importance of mitochondrial fusion during early muscle development.

PINCH-1 regulates mitochondrial dynamics to promote proline synthesis and tumor growth

Reprograming of proline metabolism is critical for tumor growth. Here we show that PINCH-1 is highly expressed in lung adenocarcinoma and promotes proline synthesis through regulation of mitochondrial dynamics. Knockout (KO) of PINCH-1 increases dynamin-related protein 1 (DRP1) expression and mitochondrial fragmentation, which suppresses kindlin-2 mitochondrial translocation and interaction with pyrroline-5-carboxylate reductase 1 (PYCR1), resulting in inhibition of proline synthesis and cell proliferation. Depletion of DRP1 reverses PINCH-1 deficiency-induced defects on mitochondrial dynamics, proline synthesis and cell proliferation. Furthermore, overexpression of PYCR1 in PINCH-1 KO cells restores proline synthesis and cell proliferation, and suppresses DRP1 expression and mitochondrial fragmentation. Finally, ablation of PINCH-1 from lung adenocarcinoma in mouse increases DRP1 expression and inhibits PYCR1 expression, proline synthesis, fibrosis and tumor growth. Our results identify a signaling axis consisting of PINCH-1, DRP1 and PYCR1 that regulates mitochondrial dynamics and proline synthesis, and suggest an attractive strategy for alleviation of tumor growth.

The role of mitochondria in redox signaling of muscle homeostasis

In the past, contraction-induced production of reactive oxygen species (ROS) has been implicated in oxidative stress to skeletal muscle. As research advances, clear evidence has revealed a more complete role of ROS under both physiologic and pathologic conditions. Central to the role of ROS is the redox signaling pathways that control exercise-induced major physiologic and cellular responses and adaptations, such as mitochondrial biogenesis, mitophagy, mitochondrial morphologic dynamics, antioxidant defense, and inflammation. The current review focuses on how muscle contraction and immobilization may activate or inhibit redox signalings and their impact on muscle mitochondrial homeostasis and physiologic implications.

Targeting the Mitochondrial Metabolic Network: A Promising Strategy in Cancer Treatment

Metabolic reprogramming is a hallmark of cancer, which implements a profound metabolic rewiring in order to support a high proliferation rate and to ensure cell survival in its complex microenvironment. Although initial studies considered glycolysis as a crucial metabolic pathway in tumor metabolism reprogramming (i.e., the Warburg effect), recently, the critical role of mitochondria in oncogenesis, tumor progression, and neoplastic dissemination has emerged. In this report, we examined the main mitochondrial metabolic pathways that are altered in cancer, which play key roles in the different stages of tumor progression. Furthermore, we reviewed the function of important molecules inhibiting the main mitochondrial metabolic processes, which have been proven to be promising anticancer candidates in recent years. In particular, inhibitors of oxidative phosphorylation (OXPHOS), heme flux, the tricarboxylic acid cycle (TCA), glutaminolysis, mitochondrial dynamics, and biogenesis are discussed. The examined mitochondrial metabolic network inhibitors have produced interesting results in both preclinical and clinical studies, advancing cancer research and emphasizing that mitochondrial targeting may represent an effective anticancer strategy.

Mitochondria Targeting as an Effective Strategy for Cancer Therapy

Mitochondria are well known for their role in ATP production and biosynthesis of macromolecules. Importantly, increasing experimental evidence points to the roles of mitochondrial bioenergetics, dynamics, and signaling in tumorigenesis. Recent studies have shown that many types of cancer cells, including metastatic tumor cells, therapy-resistant tumor cells, and cancer stem cells, are reliant on mitochondrial respiration, and upregulate oxidative phosphorylation (OXPHOS) activity to fuel tumorigenesis. Mitochondrial metabolism is crucial for tumor proliferation, tumor survival, and metastasis. Mitochondrial OXPHOS dependency of cancer has been shown to underlie the development of resistance to chemotherapy and radiotherapy. Furthermore, recent studies have demonstrated that elevated heme synthesis and uptake leads to intensified mitochondrial respiration and ATP generation, thereby promoting tumorigenic functions in non-small cell lung cancer (NSCLC) cells. Also, lowering heme uptake/synthesis inhibits mitochondrial OXPHOS and effectively reduces oxygen consumption, thereby inhibiting cancer cell proliferation, migration, and tumor growth in NSCLC. Besides metabolic changes, mitochondrial dynamics such as fission and fusion are also altered in cancer cells. These alterations render mitochondria a vulnerable target for cancer therapy. This review summarizes recent advances in the understanding of mitochondrial alterations in cancer cells that contribute to tumorigenesis and the development of drug resistance. It highlights novel approaches involving mitochondria targeting in cancer therapy.

Muscle Disuse Atrophy Caused by Discord of Intracellular Signaling

Significance: Regular contractile activity plays a critical role in maintaining skeletal muscle morphological integrity and physiological function. If the muscle is forced to stop contraction, such as during limb immobilization (IM), the IGF/Akt/mTOR signaling pathway that normally stimulates protein synthesis and inhibits proteolysis will be suppressed, whereas the FoxO-controlled catabolic pathways such as ubiquitin-proteolysis and autophagy/mitophagy will be activated and dominate, resulting in muscle fiber atrophy. Recent Advances: Mitochondria occupy a central position in the regulation of both protein synthesis and degradation through several redox-sensitive pathways, including peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), mitochondrial fusion and fission proteins, mitophagy, and sirtuins. Prolonged IM downregulates PGC-1α due to AMPK (5'-AMP-activated protein kinase) and FoxO activation, thus decreasing mitochondrial biogenesis and causing oxidative damage. Decrease of mitochondrial inner membrane potential and increase of mitochondrial fission can trigger cascades of mitophagy leading to loss of mitochondrial homeostasis (mitostasis), inflammation, and apoptosis. The phenotypic outcomes of these disorders are compromised muscle function and fiber atrophy. Critical Issues: Given the molecular mechanism of the pathogenesis, it is imperative that the integrity of intracellular signaling be restored to prevent the deterioration. So far, overexpression of PGC-1α via transgene and in vivo DNA transfection has been found to be effective in ameliorating mitostasis and reduces IM-induced muscle atrophy. Nutritional supplementation of select amino acids and phytochemicals also provides mechanistic and practical insights into the prevention of muscle disuse atrophy. Future Directions: In light of the importance of mitochondria in regulating the various critical signaling pathways, future work should focus on exploring new epigenetic strategies to restore mitostasis and redox balance.

Acid Sphingomyelinase Downregulation Enhances Mitochondrial Fusion and Promotes Oxidative Metabolism in a Mouse Model of Melanoma

Melanoma is the most severe type of skin cancer. Its unique and heterogeneous metabolism, relying on both glycolysis and oxidative phosphorylation, allows it to adapt to disparate conditions. Mitochondrial function is strictly interconnected with mitochondrial dynamics and both are fundamental in tumour progression and metastasis. The malignant phenotype of melanoma is also regulated by the expression levels of the enzyme acid sphingomyelinase (A-SMase). By modulating at transcriptional level A-SMase in the melanoma cell line B16-F1 cells, we assessed the effect of enzyme downregulation on mitochondrial dynamics and function. Our results demonstrate that A-SMase influences mitochondrial morphology by affecting the expression of mitofusin 1 and OPA1. The enhanced expression of the two mitochondrial fusion proteins, observed when A-SMase is expressed at low levels, correlates with the increase of mitochondrial function via the stimulation of the genes PGC-1alpha and TFAM, two genes that preside over mitochondrial biogenesis. Thus, the reduction of A-SMase expression, observed in malignant melanomas, may determine their metastatic behaviour through the stimulation of mitochondrial fusion, activity and biogenesis, conferring a metabolic advantage to melanoma cells.

Clinico-pathological significance of Drp1 dysregulation and its correlation to apoptosis in oral cancer patients

Dysregulation in mitochondrial dynamics has been associated with several diseases including cancer. Present study assessed the alteration in mitochondrial fission protein (Drp1) in oral epithelial cells collected from clinically confirmed pre-cancer and cancer patients and further correlates it with the cellular apoptosis signaling. Results indicate the ROS accumulation in OSCC patients is accompanied by several changes including increase in mitochondrial mass, expression of mitochondrial fission protein (Drp1) and alteration in apoptotic signaling. The positive co-relation has been observed between the expressions of anti-apoptotic Bcl-2proteinswith mitochondrial fission protein Drp1. Higher mitochondrial fission in oral cancer cells was also correlated with the increased expression of cell cycle marker CyclinD1 indicating highly proliferative stage of oral cancer cells. The clinical correlation can be extended to develop biomarker for diagram and program in oral cancer management.

Drp1-mediated mitochondrial fission contributes to baicalein-induced apoptosis and autophagy in lung cancer via activation of AMPK signaling pathway

Baicalein (BA), a natural compound extracted from Scutellaria baicalensis Georgi, has been reported to exert antitumor effect in various cancers. However, the underlying mechanisms have not been well demonstrated. In the present study, we focused on the relationship between mitochondrial fission and BA-induced apoptosis and autophagy. We showed that BA inhibited cell viability and induced mitochondrial apoptosis in A549 and H1299 lung cancer cells. BA induced the loss of mitochondrial membrane potential (MMP) and the release of cytochrome c and apoptosis inducing factor (Aif) from mitochondria to cytoplasm. Meanwhile, BA induced autophagy and activated autophagic flux. Furthermore, we found that BA induced mitochondrial fission and mitochondrial impairment. Blocking mitochondrial fission by mdivi-1 attenuated BA-induced apoptosis and autophagy. Moreover, BA activated AMP-activated protein kinase (AMPK) pathway. Knockdown of AMPK with lentivirus encoded AMPKα also attenuated BA-induced mitochondrial fission, apoptosis and autophagy. Our in vivo data confirmed that BA inhibited tumor growth and induced apoptosis and autophagy in a Lewis lung carcinoma (LLC) xenograft model via activation of AMPK/mitochondrial fission pathway. Our study highlights the critical role of AMPK/mitochondrial fission pathway in the regulation of BA-induced apoptosis and autophagy. These results revealed the molecular mechanism of the anti-lung cancer property of BA and provided novel perspectives for the application of BA in the treatment of lung cancer.

Drp1 mediates high glucose-induced mitochondrial dysfunction and epithelial-mesenchymal transition in endometrial cancer cells

This study aims to clarify the role and molecular mechanism of dynamin-related protein 1 (Drp1)-mediated mitochondrial homeostasis in high glucose (HG)-induced endometrial cancer (EC). Normal endometrium and tumor tissues of EC patients with normal and HG levels were collected, and Drp1 and p-Drp1 expression levels were detected by immunohistochemistry. Human EC cells were cultured with different glucose concentrations, and Drp1 and p-Drp1 expression levels were evaluated by Western blotting. Cell models of control and siDrp1 groups under normal and HG conditions were established, and subsequent functional experiments were conducted. Histology and in vitro experiments showed that the HG environment increased Drp1 activation, which could lead to mitochondrial dysfunction. Moreover, the imbalance of mitochondrial homeostasis mediated by Drp1 resulted in cell dysfunction, including altered glucose metabolism and increased epithelial-mesenchymal transition (EMT), migration and invasion. All these changes caused by HG could be partially alleviated by Drp1 knockdown. This study revealed that Drp1 was involved in the progression of EC associated with HG, and Drp1 might be a new potential therapeutic target for EC patients with diabetes.

Mitochondrial Fusion Via OPA1 and MFN1 Supports Liver Tumor Cell Metabolism and Growth

Metabolic reprogramming universally occurs in cancer. Mitochondria act as the hubs of bioenergetics and metabolism. The morphodynamics of mitochondria, comprised of fusion and fission processes, are closely associated with mitochondrial functions and are often dysregulated in cancer. In this study, we aim to investigate the mitochondrial morphodynamics and its functional consequences in human liver cancer. We observed excessive activation of mitochondrial fusion in tumor tissues from hepatocellular carcinoma (HCC) patients and in vitro cultured tumor organoids from cholangiocarcinoma (CCA). The knockdown of the fusion regulator genes, OPA1 (Optic atrophy 1) or MFN1 (Mitofusin 1), inhibited the fusion process in HCC cell lines and CCA tumor organoids. This resulted in inhibition of cell growth in vitro and tumor formation in vivo, after tumor cell engraftment in mice. This inhibitory effect is associated with the induction of cell apoptosis, but not related to cell cycle arrest. Genome-wide transcriptomic profiling revealed that the inhibition of fusion predominately affected cellular metabolic pathways. This was further confirmed by the blocking of mitochondrial fusion which attenuated oxygen consumption and cellular ATP production of tumor cells. In conclusion, increased mitochondrial fusion in liver cancer alters metabolism and fuels tumor cell growth.

MTFP1 overexpression promotes the growth of oral squamous cell carcinoma by inducing ROS production

Mitochondrial fission process 1 (MTFP1) is a novel nuclear-encoded protein that promotes mitochondrial fission. Increasing lines of evidence indicate that increased mitochondrial fission is involved in carcinogenesis and tumor progression. However, the expression and biological effects of MTFP1 in cancer development is still unclear, especially in oral squamous cell carcinoma (OSCC). In this study, we first evaluated the expression of MTFP1 in 12-paired OSCC tumor and peritumor tissues. We then explored the effects of MTFP1 knockdown or overexpression on cell growth by cell proliferation, colony formation, cell cycle, and cell apoptosis assays. Furthermore, the mechanisms by which MTFP1 promoted OSCC cell growth were explored. Our results showed that MTFP1 is frequently overexpressed in OSCC tissues. Functional experiments revealed that MTFP1 promoted the growth of OSCC cells by inducing the progression of cell cycle and suppressing cell apoptosis. Mechanistically, MTFP1 overexpression-mediated mitochondrial fragmentation and subsequent ROS production was found to be involved in the promotion of OSCC cell growth. Collectively, our study demonstrates that MTFP1 plays a critical oncogenic role in OSCC carcinogenesis, which may serve as a potential therapeutic target in the treatment of this malignance.

Mitochondrial fragmentation and network architecture in degenerative diseases

Fragmentation of mitochondrial network has been implicated in many neurodegenerative, renal, and metabolic diseases. However, a quantitative measure of the microscopic parameters resulting in the impaired balance between fission and fusion of mitochondria and consequently the fragmented networks in a wide range of pathological conditions does not exist. Here we present a comprehensive analysis of mitochondrial networks in cells with Alzheimer's disease (AD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), optic neuropathy (OPA), diabetes/cancer, acute kidney injury, Ca2+ overload, and Down Syndrome (DS) pathologies that indicates significant network fragmentation in all these conditions. Furthermore, we found key differences in the way the microscopic rates of fission and fusion are affected in different conditions. The observed fragmentation in cells with AD, HD, DS, kidney injury, Ca2+ overload, and diabetes/cancer pathologies results from the imbalance between the fission and fusion through lateral interactions, whereas that in OPA, PD, and ALS results from impaired balance between fission and fusion arising from longitudinal interactions of mitochondria. Such microscopic difference leads to major disparities in the fine structure and topology of the network that could have significant implications for the way fragmentation affects various cell functions in different diseases.

Mitochondrial Involvement in Cisplatin Resistance

Cisplatin is one of the worldwide anticancer drugs and, despite its toxicity and frequent recurrence of resistance phenomena, it still remains the only therapeutic option for several tumors. Circumventing cisplatin resistance remains, therefore, a major goal for clinical therapy and represents a challenge for scientific research. Recent studies have brought to light the fundamental role of mitochondria in onset, progression, and metastasis of cancer, as well as its importance in the resistance to chemotherapy. The aim of this review is to give an overview of the current knowledge about the implication of mitochondria in cisplatin resistance and on the recent development in this research field. Recent studies have highlighted the role of mitochondrial DNA alterations in onset of resistance phenomena, being related both to redox balance alterations and to signal crosstalk with the nucleus, allowing a rewiring of cell metabolism. Moreover, an important role of the mitochondrial dynamics in the adaptation mechanism of cancer cells to challenging environment has been revealed. Giving bioenergetic plasticity to tumor cells, mitochondria allow cells to evade death pathways in stressful conditions, including chemotherapy. So far, even if the central role of mitochondria is recognized, little is known about the specific mechanisms implicated in the resistance. Nevertheless, mitochondria appear to be promising pharmacological targets for overcoming cisplatin resistance, but further studies are necessary.

Effects of Dynamin-related Protein 1 Regulated Mitochondrial Dynamic Changes on Invasion and Metastasis of Lung Cancer Cells

Objective: Mitochondrial imbalance of division and fusion will lead to uncontrolled cell growth. This study investigated the effects of mitochondrial dynamics regulated by dynamin-related protein 1 (Drp1) on the invasion and metastasis of lung cancer cells at the cellular level.

Methods: Lentivirus-mediated RNAi and gene overexpression vectors containing shDrp1 and Lv-Drp1 were transfected into lung adenocarcinoma cell lines 95D and A549, respectively. An MTT assay was used to assess cell viability and a cell clone assay was used to evaluate the tumorigenic ability of lentivirus-infected cells. Cell invasion and wound healing assays were used to assess cell invasiveness and the migration rate after lentivirus infection. Annexin V-APC staining was used to determine the cell apoptosis rate.

Results: In 95D cells, when the Drp1 gene is overexpressed (OE) the proliferation rate and apoptosis rate were significantly higher than those in the control group (NC_OE) (P < 0. 05). There was no significant difference in clone number, invasion rate, and migration rate between the two groups (P > 0. 05). The proliferation rate and clone number in the shDrp1 infected 95D cell group (KD) were significantly lower than those in the control group (NC_KD) (P < 0. 05). There was no difference in apoptosis rate, invasion rate, and migration rate between h (P > 0.05). In A549 cells, unlike in 95D cells, the invasion rate of the KD group was 25% lower than that of the NC_KD group (P < 0.05). After 8 hours, the cell migration rates of the two groups were basically the same, but after 24 hours, the migration rate of the KD group was 10% lower than that of the NC_KD group (P < 0.05). Compared with the NC_OE group, the migration rate of the OE group increased significantly (P < 0.05).

Conclusion: Mitochondrial Drp1 is associated with the proliferation, invasion, and metastasis of lung adenocarcinoma cells. Inhibition of Drp1 expression may contribute to anti-tumor therapy for lung cancer.

The 3PAs: An Update on the Association of Pheochromocytomas, Paragangliomas, and Pituitary Tumors

Pituitary adenomas (PA) and pheochromocytomas/paragangliomas (PHEO/PGL) are rare tumors. Although they may co-exist by coincidence, there is mounting evidence that genes predisposing in PHEO/PGL development, may play a role in pituitary tumorigenesis. In 2012, we described a GH-secreting PA caused by an SDHD mutation in a patient with familial PGLs and found loss of heterozygosity at the SDHD locus in the pituitary tumor, along with increased hypoxia-inducible factor 1α (HIF-1α) levels. Additional patients with PAs and SDHx defects have since been reported. Overall, prevalence of SDHx mutations in PA is very rare (0.3-1.8% in unselected cases) but we and others have identified several cases of PAs with PHEOs/PGLs, like our original report, a condition which we termed the 3 P association (3PAs). Interestingly, when 3PAs is found in the sporadic setting, no SDHx defects were identified, whereas in familial PGLs, SDHx mutations were identified in 62.5-75% of the reported cases. Hence, pituitary surveillance is recommended among patients with SDHx defects. It is possible that the SDHx germline mutation-negative 3PAs cases may be due to another gene, epigenetic changes, mutations in modifier genes, mosaicism, somatic mutations, pituitary hyperplasia due to ectopic hypothalamic hormone secretion or a coincidence. PA in 3PAs are mainly macroadenomas, more aggressive, more resistant to somatostatin analogues, and often require surgery. Using the Sdhb ^+/- mouse model, we showed that hyperplasia may be the first abnormality in tumorigenesis as initial response to pseudohypoxia. We also propose surveillance and follow-up approach of patients presenting with this association.

Entrapment of N-Hydroxyphthalimide Carbon Dots in Different Topical Gel Formulations: New Composites with Anticancer Activity

In the present study, the antitumoral potential of three gel formulations loaded with carbon dots prepared from N-hydroxyphthalimide (CD-NHF) was examined and the influence of the gels on two types of skin melanoma cell lines and two types of breast cancer cell lines in 2D (cultured cells in normal plastic plates) and 3D (Matrigel) models was investigated. Antitumoral gels based on sodium alginate (AS), carboxymethyl cellulose (CMC), and the carbomer Ultrez 10 (CARB) loaded with CD-NHF were developed according to an adapted method reported by Hellerbach. Viscoelastic properties of CD-NHF-loaded gels were analyzed by rheological analysis. Also, for both CD-NHF and CD-NHF-loaded gels, the fluorescence properties were analyzed. Cell proliferation, apoptosis, and mitochondrial activity were analyzed according to basic methods used to evaluate modulatory activities of putative anticancer agents, which include reference cancer cell line culture assays in both classic 2D and 3D cultures. Using the rheological measurements, the mechanical properties of gel formulations were analyzed; all samples presented gel-like rheological characteristics. The presence of CD-NHF within the gels induces a slight decrease of the dynamic moduli, indicating a flexible gel structure. The fluorescence investigations showed that for the gel-loaded CD-NHF, the most intense emission peak was located at 370 nm (upon excitation at 330 nm). 3D cell cultures displayed visibly larger structure of tumor cells with less active phenotype appearance. The in vitro results for tested CD-NHF-loaded gel formulations revealed that the new composites are able to affect the number, size, and cellular organization of spheroids and impact individual tumor cell ability to proliferate and aggregate in spheroids.

Withaferin A-mediated apoptosis in breast cancer cells is associated with alterations in mitochondrial dynamics

Withaferin A (WA), a steroidal lactone derived from a medicinal plant (Withania somnifera), inhibits cancer development in transgenic and chemically-induced rodent models of breast cancer but the underlying mechanism is not fully grasped. We have shown previously that WA treatment causes apoptotic cell death in human breast cancer cells that is preceded by inhibition of complex III of the mitochondrial electron transport chain. This study extends these observations to now demonstrate alterations in mitochondrial dynamics in WA-induced apoptosis. Assembly of complex III was decreased in MCF-7 and SUM159 cells but not in MDA-MB-231 as determined by native blue gel electrophoresis. Because WA is a Michael acceptor (electrophile), we explored the possibility of whether it covalently modifies cysteine residue(s) in ubiquinol-cytochrome c reductase, Rieske iron-sulfur polypeptide 1 (UQCRFS1). Covalent modification of cysteine in UQCRFS1 was not observed after WA treatment. Instead, WA treatment inhibited chemically-induced mitochondrial fusion and decreased the mitochondrial volume, and this effect was accompanied by a decrease in the expression of proteins involved in fusion process, including mitofusin1, mitofusin2, and full-length optic atrophy protein 1 (OPA1). A loss of volume in fragmented mitochondria also occurred in WA-exposed cells when compared to vehicle-treated control. WA treatment also caused a decrease in protein level of mitochondrial fission-regulating protein dynamin-related protein 1 (DRP1). Functional studies revealed that DRP1 deficiency and OPA1 knockdown attenuated apoptotic potential of WA. Taken together, these results indicate that WA not only alters Complex III assembly but also inhibits mitochondrial dynamics in breast cancer cells.

Energetic costs of cellular and therapeutic control of stochastic mitochondrial DNA populations

The dynamics of the cellular proportion of mutant mtDNA molecules is crucial for mitochondrial diseases. Cellular populations of mitochondria are under homeostatic control, but the details of the control mechanisms involved remain elusive. Here, we use stochastic modelling to derive general results for the impact of cellular control on mtDNA populations, the cost to the cell of different mtDNA states, and the optimisation of therapeutic control of mtDNA populations. This formalism yields a wealth of biological results, including that an increasing mtDNA variance can increase the energetic cost of maintaining a tissue, that intermediate levels of heteroplasmy can be more detrimental than homoplasmy even for a dysfunctional mutant, that heteroplasmy distribution (not mean alone) is crucial for the success of gene therapies, and that long-term rather than short intense gene therapies are more likely to beneficially impact mtDNA populations.

MicroRNA-Mediated Health-Promoting Effects of Phytochemicals

Phytochemicals are known to benefit human health by modulating various cellular processes, including cell proliferation, apoptosis, and inflammation. Due to the potential use of phytochemicals as therapeutic agents against human diseases such as cancer, studies are ongoing to elucidate the molecular mechanisms by which phytochemicals affect cellular functions. It has recently been shown that phytochemicals may regulate the expression of microRNAs (miRNAs). MiRNAs are responsible for the fine-tuning of gene expression by controlling the expression of their target mRNAs in both normal and pathological cells. This review summarizes the recent findings regarding phytochemicals that modulate miRNA expression and promote human health by exerting anticancer, photoprotective, and anti-hepatosteatosis effects. Identifying miRNAs modulated by phytochemicals and understanding the regulatory mechanisms mediated by their target mRNAs will facilitate the efforts to maximize the therapeutic benefits of phytochemicals.

Inhibiting neddylation modification alters mitochondrial morphology and reprograms energy metabolism in cancer cells

Abnormal activation of neddylation modification and dysregulated energy metabolism are frequently seen in many types of cancer cells. Whether and how neddylation modification affects cellular metabolism remains largely unknown. Here, we showed that MLN4924, a small-molecule inhibitor of neddylation modification, induces mitochondrial fission-to-fusion conversion in breast cancer cells via inhibiting ubiquitylation and degradation of fusion-promoting protein mitofusin 1 (MFN1) by SCFβ-TrCP E3 ligase and blocking the mitochondrial translocation of fusion-inhibiting protein DRP1. Importantly, MLN4924-induced mitochondrial fusion is independent of cell cycle progression, but confers cellular survival. Mass-spectrometry-based metabolic profiling and mitochondrial functional assays reveal that MLN4924 inhibits the TCA cycle but promotes mitochondrial OXPHOS. MLN4924 also increases glycolysis by activating PKM2 via promoting its tetramerization. Biologically, MLN4924 coupled with the OXPHOS inhibitor metformin, or the glycolysis inhibitor shikonin, significantly inhibits cancer cell growth both in vitro and in vivo. Together, our study links neddylation modification and energy metabolism, and provides sound strategies for effective combined cancer therapies.

Dynamin-related protein 1: A critical protein in the pathogenesis of neural system dysfunctions and neurodegenerative diseases

Mitochondria play a key role in the maintenance of neuronal function by continuously providing energy. Here, we will give a detailed review about the recent developments in regards to dynamin-related protein 1 (Drp1) induced unbalanced mitochondrial dynamics, excessive mitochondrial division, and neuronal injury in neural system dysfunctions and neurodegenerative diseases, including the Drp1 knockout induced mice embryonic death, the dysfunction of the Drp1-dependent mitochondrial division induced neuronal cell apoptosis and impaired neuronal axonal transportation, the abnormal interaction between Drp1 and amyloid β (Aβ) in Alzheimer's disease (AD), the mutant Huntingtin (Htt) in Huntington's disease (HD), and the Drp1-associated pathogenesis of other neurodegenerative diseases such as Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Drp1 is required for mitochondrial division determining the size, shape, distribution, and remodeling as well as maintaining of mitochondrial integrity in mammalian cells. In addition, increasing reports indicate that the Drp1 is involved in some cellular events of neuronal cells causing some neural system dysfunctions and neurodegenerative diseases, including impaired mitochondrial dynamics, apoptosis, and several posttranslational modification induced increased mitochondrial divisions. Recent studies also revealed that the Drp1 can interact with Aβ, phosphorylated τ, and mutant Htt affecting the mitochondrial shape, size, distribution, axonal transportation, and energy production in the AD and HD neuronal cells. These changes can affect the health of mitochondria and the function of synapses causing neuronal injury and eventually leading to the dysfunction of memory, cognitive impairment, resting tremor, posture instability, involuntary movements, and progressive muscle atrophy and paralysis in patients.

Positive feedback loop between mitochondrial fission and Notch signaling promotes survivin-mediated survival of TNBC cells

Mitochondrial morphology is remodeled by continuous dynamic cycles of fission and fusion. Emerging data have shown that the disturbance of balance between mitochondrial fission and fusion is involved in the progression of several types of neoplasms. However, the status of mitochondrial dynamics and its potential biological roles in breast cancer (BC), particularly in triple negative BC (TNBC) are not fully clear. Here, we reported that the mitochondrial fission was significantly increased in BC tissues, especially in the TNBC tissues, when compared with that in the corresponding peritumor tissues. Meanwhile, our data showed that Drp1 was upregulated, while Mfn1 was downregulated in TNBC. Moreover, elevated mitochondrial fission was associated with poorer prognosis in TNBC patients. Mitochondrial fission promoted the survival of TNBC cells both in vitro and in vivo. Furthermore, we identified a positive feedback loop between mitochondrial fission and Notch signaling pathway in TNBC cells, as proved by the experimental evidence that the activation of Notch signaling enhanced Drp1-mediated mitochondrial fission and Drp1-mediated mitochondrial fission in turn promoted the activation of Notch signaling, which ultimately promoted the cell survival of TNBC via increasing survivin expression level. Inhibition of either Notch1 or Drp1 significantly impaired the activation of the other, leading to the suppression of TNBC cell survival and proliferation. Collectively, our data reveal a novel mechanism that the positive feedback loop between mitochondrial fission and Notch signaling promotes the survival, proliferation and apoptotic resistance of TNBC cells via increasing survivin expression and thus favors cancer progression.

HMGB1 promotes ERK-mediated mitochondrial Drp1 phosphorylation for chemoresistance through RAGE in colorectal cancer

Dysfunctional mitochondria have been shown to enhance cancer cell proliferation, reduce apoptosis, and increase chemoresistance. Chemoresistance develops in nearly all patients with colorectal cancer, leading to a decrease in the therapeutic efficacies of anticancer agents. However, the effect of dynamin-related protein 1 (Drp1)-mediated mitochondrial fission on chemoresistance in colorectal cancer is unclear. Here, we found that the release of high-mobility group box 1 protein (HMGB1) in conditioned medium from dying cells by chemotherapeutic drugs and resistant cells, which triggered Drp1 phosphorylation via its receptor for advanced glycation end product (RAGE). RAGE signals ERK1/2 activation to phosphorylate Drp1 at residue S616 triggerring autophagy for chemoresistance and regrowth in the surviving cancer cells. Abolishment of Drp1 phosphorylation by HMGB1 inhibitor and RAGE blocker significantly enhance sensitivity to the chemotherapeutic treatment by suppressing autophagy. Furthermore, patients with high phospho-Drp1^Ser616 are associated with high risk on developing tumor relapse, poor 5-year disease-free survival (DFS) and 5-year overall survival (OS) after neoadjuvant chemoradiotherapy (neoCRT) treatment in locally advanced rectal cancer (LARC). Moreover, patients with RAGE-G82S polymorphism (rs2070600) are associated with high phospho-Drp1^Ser616 within tumor microenvironment. These findings suggest that the release of HMGB1 from dying cancer cells enhances chemoresistance and regrowth via RAGE-mediated ERK/Drp1 phosphorylation.

Dynamin-related protein 1-mediated mitochondrial fission contributes to IR-783-induced apoptosis in human breast cancer cells

IR‐783 is a kind of heptamethine cyanine dye that exhibits imaging, cancer targeting and anticancer properties. A previous study reported that its imaging and targeting properties were related to mitochondria. However, the molecular mechanism behind the anticancer activity of IR‐783 has not been well demonstrated. In this study, we showed that IR‐783 inhibits cell viability and induces mitochondrial apoptosis in human breast cancer cells. Exposure of MDA‐MB‐231 cells to IR‐783 resulted in the loss of mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) depletion, mitochondrial permeability transition pore (mPTP) opening and cytochrome c (Cyto C) release. Furthermore, we found that IR‐783 induced dynamin‐related protein 1 (Drp1) translocation from the cytosol to the mitochondria, increased the expression of mitochondrial fission proteins mitochondrial fission factor (MFF) and fission‐1 (Fis1), and decreased the expression of mitochondrial fusion proteins mitofusin1 (Mfn1) and optic atrophy 1 (OPA1). Moreover, knockdown of Drp1 markedly blocked IR‐783‐mediated mitochondrial fission, loss of MMP, ATP depletion, mPTP opening and apoptosis. Our in vivo study confirmed that IR‐783 markedly inhibited tumour growth and induced apoptosis in an MDA‐MB‐231 xenograft model in association with the mitochondrial translocation of Drp1. Taken together, these findings suggest that IR‐783 induces apoptosis in human breast cancer cells by increasing Drp1‐mediated mitochondrial fission. Our study uncovered the molecular mechanism of the anti‐breast cancer effects of IR‐783 and provided novel perspectives for the application of IR‐783 in the treatment of breast cancer.

Tumor metabolism regulating chemosensitivity in ovarian cancer

Elevated metabolism is a key hallmark of multiple cancers, serving to fulfill high anabolic demands. Ovarian cancer (OVCA) is the fifth leading cause of cancer deaths in women with a high mortality rate (45%). Chemoresistance is a major hurdle for OVCA treatment. Although substantial evidence suggests that metabolic reprogramming contributes to anti-apoptosis and the metastasis of multiple cancers, the link between tumor metabolism and chemoresistance in OVCA remains unknown. While clinical trials targeting metabolic reprogramming alone have been met with limited success, the synergistic effect of inhibiting tumor-specific metabolism with traditional chemotherapy warrants further examination, particularly in OVCA. This review summarizes the role of key glycolytic enzymes and other metabolic synthesis pathways in the progression of cancer and chemoresistance in OVCA. Within this context, mitochondrial dynamics (fission, fusion and cristae structure) are addressed regarding their roles in controlling metabolism and apoptosis, closely associated with chemosensitivity. The roles of multiple key oncogenes (Akt, HIF-1α) and tumor suppressors (p53, PTEN) in metabolic regulation are also described. Next, this review summarizes recent research of metabolism and future direction. Finally, we examine clinical drugs and inhibitors to target glycolytic metabolism, as well as the rationale for such strategies as potential therapeutics to overcome chemoresistant OVCA.

Dysregulation of mitochondrial dynamics proteins are a targetable feature of human tumors

Altered mitochondrial dynamics can broadly impact tumor cell physiology. Using genetic and pharmacological profiling of cancer cell lines and human tumors, we here establish that perturbations to the mitochondrial dynamics network also result in specific therapeutic vulnerabilities. In particular, through distinct mechanisms, tumors with increased mitochondrial fragmentation or connectivity are hypersensitive to SMAC mimetics, a class of compounds that induce apoptosis through inhibition of IAPs and for which robust sensitivity biomarkers remain to be identified. Further, because driver oncogenes exert dominant control over mitochondrial dynamics, oncogene-targeted therapies can be used to sensitize tumors to SMAC mimetics via their effects on fission/fusion dynamics. Collectively, these data demonstrate that perturbations to the mitochondrial dynamics network induce targetable vulnerabilities across diverse human tumors and, more broadly, suggest that the altered structures, activities, and trafficking of cellular organelles may facilitate additional cancer therapeutic opportunities.