Therapeutic potential of targeting mitochondrial dynamics in cancer

Emerging mechanistic insights of selective autophagy in hepatic diseases

Macroautophagy (hereafter referred to as autophagy), a highly conserved metabolic process, regulates cellular homeostasis by degrading dysfunctional cytosolic constituents and invading pathogens via the lysosomal system. In addition, autophagy selectively recycles specific organelles such as damaged mitochondria (via mitophagy), and lipid droplets (LDs; via lipophagy) or eliminates specialized intracellular pathogenic microorganisms such as hepatitis B virus (HBV) and coronaviruses (via virophagy). Selective autophagy, particularly mitophagy, plays a key role in the preservation of healthy liver physiology, and its dysfunction is connected to the pathogenesis of a wide variety of liver diseases. For example, lipophagy has emerged as a defensive mechanism against chronic liver diseases. There is a prominent role for mitophagy and lipophagy in hepatic pathologies including non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC), and drug-induced liver injury. Moreover, these selective autophagy pathways including virophagy are being investigated in the context of viral hepatitis and, more recently, the coronavirus disease 2019 (COVID-19)-associated hepatic pathologies. The interplay between diverse types of selective autophagy and its impact on liver diseases is briefly addressed. Thus, modulating selective autophagy (e.g., mitophagy) would seem to be effective in improving liver diseases. Considering the prominence of selective autophagy in liver physiology, this review summarizes the current understanding of the molecular mechanisms and functions of selective autophagy (mainly mitophagy and lipophagy) in liver physiology and pathophysiology. This may help in finding therapeutic interventions targeting hepatic diseases via manipulation of selective autophagy.

Advanced Bioinformatics Analysis and Genetic Technologies for Targeting Autophagy in Glioblastoma Multiforme

As the most malignant primary brain tumor in adults, a diagnosis of glioblastoma multiforme (GBM) continues to carry a poor prognosis. GBM is characterized by cytoprotective homeostatic processes such as the activation of autophagy, capability to confer therapeutic resistance, evasion of apoptosis, and survival strategy even in the hypoxic and nutrient-deprived tumor microenvironment. The current gold standard of therapy, which involves radiotherapy and concomitant and adjuvant chemotherapy with temozolomide (TMZ), has been a game-changer for patients with GBM, relatively improving both overall survival (OS) and progression-free survival (PFS); however, TMZ is now well-known to upregulate undesirable cytoprotective autophagy, limiting its therapeutic efficacy for induction of apoptosis in GBM cells. The identification of targets utilizing bioinformatics-driven approaches, advancement of modern molecular biology technologies such as clustered regularly interspaced short palindromic repeats (CRISPR)—CRISPR-associated protein (Cas9) or CRISPR-Cas9 genome editing, and usage of microRNA (miRNA)-mediated regulation of gene expression led to the selection of many novel targets for new therapeutic development and the creation of promising combination therapies. This review explores the current state of advanced bioinformatics analysis and genetic technologies and their utilization for synergistic combination with TMZ in the context of inhibition of autophagy for controlling the growth of GBM.

Constructing a novel mitochondrial-related gene signature for evaluating the tumor immune microenvironment and predicting survival in stomach adenocarcinoma

BACKGROUND

The incidence and mortality of gastric cancer ranks fifth and fourth worldwide among all malignancies, respectively. Accumulating evidences have revealed the close relationship between mitochondrial dysfunction and the initiation and progression of stomach cancer. However, rare prognostic models for mitochondrial-related gene risk have been built up in stomach cancer.

METHODS

In current study, the expression and prognostic value of mitochondrial-related genes in stomach adenocarcinoma (STAD) patients were systematically analyzed to establish a mitochondrial-related risk model based on available TCGA and GEO databases. The tumor microenvironment (TME), immune cell infiltration, tumor mutation burden, and drug sensitivity of gastric adenocarcinoma patients were also investigated using R language, GraphPad Prism 8 and online databases.

RESULTS

We established a mitochondrial-related risk prognostic model including NOX4, ALDH3A2, FKBP10 and MAOA and validated its predictive power. This risk model indicated that the immune cell infiltration in high-risk group was significantly different from that in the low-risk group. Besides, the risk score was closely related to TME signature genes and immune checkpoint molecules, suggesting that the immunosuppressive tumor microenvironment might lead to poor prognosis in high-risk groups. Moreover, TIDE analysis demonstrated that combined analysis of risk score and immune score, or stromal score, or microsatellite status could more effectively predict the benefit of immunotherapy in STAD patients with different stratifications. Finally, rapamycin, PD-0325901 and dasatinib were found to be more effective for patients in the high-risk group, whereas AZD7762, CEP-701 and methotrexate were predicted to be more effective for patients in the low-risk group.

CONCLUSIONS

Our results suggest that the mitochondrial-related risk model could be a reliable prognostic biomarker for personalized treatment of STAD patients.

Multi-omics and experimental analysis unveil theragnostic value and immunological roles of inner membrane mitochondrial protein (IMMT) in breast cancer

BACKGROUND

The inner membrane mitochondrial protein (IMMT) is a central unit of the mitochondrial contact site and cristae organizing system (MICOS). While researchers continue to demonstrate the physiological function of IMMT in regulating mitochondrial dynamics and preserving mitochondrial structural integrity, the roles of IMMT in clinicopathology, the tumor immune microenvironment (TIME), and precision oncology in breast cancer (BC) remain unclear.

METHODS

Multi-omics analysis was used here to evaluate the diagnostic and prognostic value of IMMT. Web applications aimed at analyzing the whole tumor tissue, single cells, and spatial transcriptomics were used to examine the relationship of IMMT with TIME. Gene set enrichment analysis (GSEA) was employed to determine the primary biological impact of IMMT. Experimental verification using siRNA knockdown and clinical specimens of BC patients confirmed the mechanisms behind IMMT on BC cells and the clinical significance, respectively. Potent drugs were identified by accessing the data repositories of CRISPR-based drug screenings.

RESULTS

High IMMT expression served as an independent diagnostic biomarker, correlated with advanced clinical status, and indicated a poor relapse-free survival (RFS) rate for patients with BC. Although, the contents of Th1, Th2, MSC, macrophages, basophil, CD4 + T cell and B cell, and TMB levels counteracted the prognostic significance. Single-cell level and whole-tissue level analyses revealed that high IMMT was associated with an immunosuppressive TIME. GSEA identified IMMT perturbation as involved in cell cycle progression and mitochondrial antioxidant defenses. Experimental knockdown of IMMT impeded the migration and viability of BC cells, arrested the cell cycle, disturbed mitochondrial function, and increased the ROS level and lipid peroxidation. The clinical values of IMMT were amenable to ethnic Chinese BC patients, and can be extrapolated to some other cancer types. Furthermore, we discovered that pyridostatin acted as a potent drug candidate in BC cells harboring an elevated IMMT expression.

CONCLUSION

This study combined a multi-omics survey with experimental verification to reveal the novel clinical significance of IMMT in BC, demonstrating its role in TIME, cancer cell growth and mitochondrial fitness, and identified pyridostatin as a promising drug candidate for the development of precision medicine.

CPNE1 regulates myogenesis through the PERK-eIF2α pathway mediated by endoplasmic reticulum stress

Sarcopenia is characterized by a progressive reduction in muscle mass or muscle physiological function associated with aging, but the relevant molecular mechanisms are not clear. Here, we identify the role of the myogenesis modifier CPNE1 in sarcopenia. CPNE1 is upregulated in aged skeletal muscles and young skeletal muscle satellite cells with palmitate-induced atrophy. The overexpression of CPNE1 hinders proliferation and differentiation and increases muscle atrophy characteristics in young skeletal muscle-derived satellite cells. In addition, CPNE1 overexpression disrupts the balance of mitochondrial fusion and division and causes endoplasmic reticulum stress. We found that the effects of CPNE1 on mitochondrial function are dependent on the PERK/eIF2α/ATF4 pathway. The overexpression of CPNE1 in young muscles alters membrane lipid composition, reduces skeletal muscle fibrosis regeneration, and exercise capacity in mice. These effects were reversed by PERK inhibitor GSK2606414. Moreover, immunoprecipitation indicates that CPNE1 overexpression greatly increased the acetylation of PERK. Therefore, CPNE1 is an important modifier that drives mitochondrial homeostasis to regulate myogenic cell proliferation and differentiation via the PERK-eIF2α pathway, which could be a valuable target for age-related sarcopenia.

Ovarian Cancer: A Landscape of Mitochondria with Emphasis on Mitochondrial Dynamics

Ovarian cancer (OC) represents the main cause of death from gynecological malignancies in western countries. Altered cellular and mitochondrial metabolism are considered hallmarks in cancer disease. Several mitochondrial aspects have been found altered in OC, such as the oxidative phosphorylation system, oxidative stress and mitochondrial dynamics. Mitochondrial dynamics includes cristae remodeling, fusion, and fission processes forming a dynamic mitochondrial network. Alteration of mitochondrial dynamics is associated with metabolic change in tumour development and, in particular, the mitochondrial shaping proteins appear also to be responsible for the chemosensitivity and/or chemoresistance in OC. In this review a focus on the mitochondrial dynamics in OC cells is presented.

The role of angiogenesis in melanoma: Clinical treatments and future expectations

The incidence of melanoma has increased rapidly over the past few decades, with mortality accounting for more than 75% of all skin cancers. The high metastatic potential of Melanoma is an essential factor in its high mortality. Vascular angiogenic system has been proved to be crucial for the metastasis of melanoma. An in-depth understanding of angiogenesis will be of great benefit to melanoma treatment and may promote the development of melanoma therapies. This review summarizes the recent advances and challenges of anti-angiogenic agents, including monoclonal antibodies, tyrosine kinase inhibitors, human recombinant Endostatin, and traditional Chinese herbal medicine. We hope to provide a better understanding of the mechanisms, clinical research progress, and future research directions of melanoma.

2-Methoxyestradiol Damages DNA in Glioblastoma Cells by Regulating nNOS and Heat Shock Proteins

Gliomas are the most prevalent primary tumors of the central nervous system (CNS), accounting for over fifty percent of all primary intracranial neoplasms. Glioblastoma (GBM) is the most prevalent form of malignant glioma and is often incurable. The main distinguishing trait of GBM is the presence of hypoxic regions accompanied by enhanced angiogenesis. 2-Methoxyestradiol (2-ME) is a well-established antiangiogenic and antiproliferative drug. In current clinical studies, 2-ME, known as Panzem, was examined for breast, ovarian, prostate, and multiple myeloma. The SW1088 grade III glioma cell line was treated with pharmacological and physiological doses of 2-ME. The induction of apoptosis and necrosis, oxidative stress, cell cycle arrest, and mitochondrial membrane potential were established by flow cytometry. Confocal microscopy was used to detect DNA damage. The Western blot technique determined the level of nitric oxide synthase and heat shock proteins. Here, for the first time, 2-ME is shown to induce nitro-oxidative stress with the concomitant modulation of heat shock proteins (HSPs) in the SW1088 grade III glioma cell line. Crucial therapeutic strategies for GMB should address both cell proliferation and angiogenesis, and due to the above, 2-ME seems to be a perfect candidate for GBM therapy.

Prognostic impact of mitofusin 2 expression in colon cancer

BACKGROUND

Mitofusin 2 (MFN2) is involved in several biological processes, including cancer. MFN2 is downregulated in some types of cancer and inhibits cancer cell proliferation, migration, and invasion. However, the relationship between MFN2 and colon cancer remains unknown.

METHODS

In this study, MFN2 expression was investigated using The Cancer Genome Atlas (TCGA) and the Human Protein Atlas (HPA), and the associations between prognostic factors and survival outcomes were assessed via univariate and multivariate analyses. Functional enrichment analyses based on Kyoto Encyclopedia of Genes and Genomes (KEGG) resource and Gene Set Enrichment Analysis (GSEA) were carried out.

RESULTS

MFN2 was downregulated in colon cancer tissues compared with paracancerous colon tissues (P<0.001), and low MFN2 expression was associated with an advanced tumor stage (stage IV vs. stage I, P=0.03; stage I-III vs. stage IV, P=0.003). MFN2 immunohistochemistry (IHC) staining was medium to high in colon normal tissues, but MFN2 IHC staining was faint or not identified in colorectal cancer (CRC) tumor tissues. MFN2 expression was either low or non-existent in colon cancer distinct cell clusters, according to differential gene analysis. Univariate analysis revealed that MFN2 expression in colon cancer patients was significantly associated with the stage [odds ratio (OR) =0.29 for stage IV vs. stage I, P=0.001], T-stage (OR =0.20 for T4 vs. T1, P=0.033), and distant metastasis (OR =0.31 for M1 vs. M0, P=0.000). Furthermore, Kaplan-Meier survival analysis revealed that patients with colon cancer and high MFN2 expression have a better prognosis than those with low MFN2 expression (P=0.002). MFN2 (hazard ratio =0.95, 95% confidence interval: 0.92-0.99, P=0.007) was an independent predictor of colon cancer according to univariate and multivariate Cox models. Finally, GSEA results showed that the KEGG GALACTOSE METABOLISM, APOPTOSIS, and VEGF SIGNALING pathways were activated in the high MFN2 mRNA expression group, whereas the KEGG RIBOSOME pathway was inhibited in the low MFN2 expression group.

CONCLUSIONS

Our research revealed MFN2 to be a promising predictive biomarker and therapeutic target for colon cancer.

Targeting Ca2+ and Mitochondrial Homeostasis by Antipsychotic Thioridazine in Leukemia Cells

Mitochondria have pivotal roles in cellular physiology including energy metabolism, reactive oxygen species production, Ca2+ homeostasis, and apoptosis. Altered mitochondrial morphology and function is a common feature of cancer cells and the regulation of mitochondrial homeostasis has been identified as a key to the response to chemotherapeutic agents in human leukemias. Here, we explore the mechanistic aspects of cytotoxicity produced by thioridazine (TR), an antipsychotic drug that has been investigated for its anticancer potential in human leukemia cellular models. TR exerts selective cytotoxicity against human leukemia cells in vitro. A PCR array provided a general view of the expression of genes involved in cell death pathways. TR immediately produced a pulse of cytosolic Ca2+, followed by mitochondrial uptake, resulting in mitochondrial permeabilization, caspase 9/3 activation, endoplasmic reticulum stress, and apoptosis. Ca2+ chelators, thiol reducer dithiothreitol, or CHOP knockdown prevented TR-induced cell death. TR also exhibited potent cytotoxicity against BCL-2/BCL-xL-overexpressing leukemia cells. Additionally, previous studies have shown that TR exhibits potent antitumor activity in vivo in different solid tumor models. These findings show that TR induces a Ca2+-mediated apoptosis with involvement of mitochondrial permeabilization and ER stress in leukemia and it emphasizes the pharmacological potential of TR as an adjuvant in antitumor chemotherapy.

m6A RNA methylation-mediated NDUFA4 promotes cell proliferation and metabolism in gastric cancer

Gastric cancer (GC) is a malignancy with poor prognosis. NDUFA4 is reported to correlate with the progression of GC. However, its underlying mechanism in GC is unknown. Our study was to reveal the pathogenic mechanism of NDUFA4 in GC. NDUFA4 expression was explored in single-cell and bulk RNA-seq data as well as GC tissue microarray. Mitochondrial respiration and glycolysis were estimated by oxygen consumption rate and extracellular acidification rate, respectively. The interaction between NDUFA4 and METTL3 was validated by RNA immunoprecipitation. Flow cytometry was used to estimate cell cycle, apoptosis and mitochondrial activities. NDUFA4 was highly expressed in GC and its high expression indicated a poor prognosis. The knockdown of NDUFA4 could reduce cell proliferation and inhibit tumor growth. Meanwhile, NDUFA4 could promote glycolytic and oxidative metabolism in GC cells, whereas the inhibition of glycolysis suppressed the proliferation and tumor growth of GC. Besides, NDUFA4 inhibited ROS level and promoted MMP level in GC cells, whereas the inhibition of mitochondrial fission could reverse NDUFA4-induced glycolytic and oxidative metabolism and tumor growth of GC. Additionally, METTL3 could increase the m6A level of NDUFA4 mRNA via the m6A reader IGF2BP1 to promote NDUFA4 expression in GC cells. Our study revealed that NDUFA4 was increased by m6A methylation and could promote GC development via enhancing cell glycolysis and mitochondrial fission. NDUFA4 was a potential target for GC treatment.

Mitochondrial Dysfunction and Chronic Liver Disease

Mitochondria are generally considered the powerhouse of the cell, a small subcellular organelle that produces most of the cellular energy in the form of adenosine triphosphate (ATP). In addition, mitochondria are involved in various biological functions, such as biosynthesis, lipid metabolism, oxidative phosphorylation, cell signal transduction, and apoptosis. Mitochondrial dysfunction is manifested in different aspects, like increased mitochondrial reactive oxygen species (ROS), mitochondrial DNA (mtDNA) damage, adenosine triphosphate (ATP) synthesis disorder, abnormal mitophagy, as well as changes in mitochondrial morphology and structure. Mitochondrial dysfunction is related to the occurrence and development of various chronic liver diseases, including hepatocellular carcinoma (HCC), viral hepatitis, drug-induced liver injury (DILI), alcoholic fatty liver (AFL), and non-alcoholic fatty liver (NAFL). In this review, we summarize and discuss the role and mechanisms of mitochondrial dysfunction in chronic liver disease, focusing on and discussing some of the latest studies on mitochondria and chronic liver disease.

Mitochondrial Dysfunction in Parkinson’s Disease: From Mechanistic Insights to Therapy

Parkinson’s disease (PD) is one of the most common neurodegenerative movement disorders worldwide. There are currently no cures or preventative treatments for PD. Emerging evidence indicates that mitochondrial dysfunction is closely associated with pathogenesis of sporadic and familial PD. Because dopaminergic neurons have high energy demand, cells affected by PD exhibit mitochondrial dysfunction that promotes the disease-defining the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The mitochondrion has a particularly important role as the cellular “powerhouse” of dopaminergic neurons. Therefore, mitochondria have become a promising therapeutic target for PD treatments. This review aims to describe mitochondrial dysfunction in the pathology of PD, outline the genes associated with familial PD and the factors related to sporadic PD, summarize current knowledge on mitochondrial quality control in PD, and give an overview of therapeutic strategies for targeting mitochondria in neuroprotective interventions in PD.

Mfn2-mediated mitochondrial fusion alleviates doxorubicin-induced cardiotoxicity with enhancing its anticancer activity through metabolic switch

Imbalanced mitochondrial dynamics including inhibited mitochondrial fusion is associated with cardiac dysfunction as well as tumorigenesis. This study sought to explore the effects of promoting mitochondrial fusion on doxorubicin(Dox)-induced cardiotoxicity and its antitumor efficacy, with a focus on the underlying metabolic mechanisms. Herein, the inhibition of Mfn2-mediated mitochondrial fusion was identified as a key phenotype in Dox-induced cardiotoxicity. Restoration of Mfn2-mediated mitochondrial fusion enhanced mitochondrial oxidative metabolism, reduced cellular injury/apoptosis and inhibited mitochondria-derived oxidative stress in the Dox-treated cardiomyocytes. Application of lentivirus expressing Drp1 (mitochondrial fusion inhibitor) or Rote/Anti A (mitochondrial complex I/III inhibitors) blunted the above protective effects of Mfn2. Cardiac-specific Mfn2 transgenic mice showed preserved mitochondrial fusion and attenuated myocardial injury upon Dox exposure in vivo. The suppression of Mfn2-mediated mitochondrial fusion was induced by Dox-elicited upregulation of FoxO1, which inhibited the transcription of Mfn2 by binding to its promoter sites. In the B16 melanoma, Mfn2 upregulation not only attenuated tumor growth alone but also further delayed tumor growth in the presence of Dox. Mechanistically, Mfn2 synergized with the inhibitory action of Dox on glycolysis metabolism in the tumor cells. One common feature in both cardiomyocytes and tumor cells was that Mfn2 increased the ratio of oxygen consumption rate to extracellular acidification rate, suggesting Mfn2 triggered a shift from aerobic glycolysis to mitochondrial oxidative metabolism. In conclusion, targeting Mfn2-mediated mitochondrial fusion may provide a dual therapeutic advantage in Dox-based chemotherapy by simultaneously defending against Dox-induced cardiotoxicity and boosting its antitumor potency via metabolic shift.

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Dox exposure inhibits Mfn2-mediated mitochondrial fusion in the hearts.

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The reduction of Mfn2 is mediated by FoxO1 in a transcriptional manner.

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Mfn2 overexpression reduces Dox-induced injury and enhances its anticancer action.

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Mfn2 induces a shift from aerobic glycolysis to mitochondrial oxidative metabolism.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Targeting Mitochondrial COX-2 Enhances Chemosensitivity via Drp1-Dependent Remodeling of Mitochondrial Dynamics in Hepatocellular Carcinoma

Simple Summary

New therapeutic strategies are urgently needed to improve the anti-cancer effect for hepatocellular carcinoma (HCC). Overexpression of cyclooxygenase-2 (COX-2) is found in several types of cancers and correlates with a poor prognosis. However, it remains unclear how the mitochondrial translocation of COX-2 is involved in mitochondrial dynamics and sensitizes HCC cells to multipattern anti-tumor therapy. We explored the impact of targeting mitochondrial COX-2 (mito-COX-2) intervention toward mitochondrial dynamics on platinum-based chemotherapeutics in HCC cells and xenograft nude mouse models. Our study indicates that the mito-COX-2 represents a candidate predictive biomarker and potential target to regulate anti-cancer sensitization of HCC, and possibly for other types of COX-2-high-expression cancers.

Abstract

Mitochondria are highly dynamic organelles and undergo constant fission and fusion, which are both essential for the maintenance of cell physiological functions. Dysregulation of dynamin-related protein 1 (Drp1)-dependent mitochondrial dynamics is associated with tumorigenesis and the chemotherapeutic response in hepatocellular carcinoma (HCC). The enzyme cyclooxygenase-2 (COX-2) is overexpressed in most cancer types and correlates with a poor prognosis. However, the roles played by the translocation of mitochondrial COX-2 (mito-COX-2) and the interaction between mito-COX-2 and Drp1 in chemotherapeutic responses remain to be elucidated in the context of HCC. Bioinformatics analysis, paired HCC patient specimens, xenograft nude mice, immunofluorescence, transmission electron microscopy, molecular docking, CRISPR/Cas9 gene editing, proximity ligation assay, cytoplasmic and mitochondrial fractions, mitochondrial immunoprecipitation assay, and flow cytometry analysis were performed to evaluate the underlying mechanism of how mito-COX-2 and p-Drp1^Ser616 interaction regulates the chemotherapeutic response via mitochondrial dynamics in vitro and in vivo. We found that COX-2 and Drp1 were frequently upregulated and confer a poor prognosis in HCC. We also found that the proportion of mito-COX-2 and p-Drp1^Ser616 was increased in HCC cell lines. In vitro, we demonstrated that the enhanced mitochondrial translocation of COX-2 promotes its interaction with p-Drp1^Ser616 via PTEN-induced putative kinase 1 (PINK1)-mediated Drp1 phosphorylation activation. This increase was associated with higher colony formation, cell proliferation, and mitochondrial fission. These findings were confirmed by knocking down COX-2 in HCC cells using CRISPR/Cas9 technology. Furthermore, inhibition of Drp1 using pharmacologic inhibitors (Mdivi-1) or RNA interference (siDNM1L) decreased mito-COX-2/p-Drp1^Ser616 interaction-mediated mitochondrial fission, and increased apoptosis in HCC cells treated with platinum drugs. Moreover, inhibiting mito-COX-2 acetylation with the natural phytochemical resveratrol resulted in reducing cell proliferation and mitochondrial fission, occurring through upregulation of mitochondrial deacetylase sirtuin 3 (SIRT3), which, in turn, increased the chemosensitivity of HCC to platinum drugs in vitro and in vivo. Our results suggest that targeting interventions to PINK1-mediated mito-COX-2/p-Drp1^Ser616-dependent mitochondrial dynamics increases the chemosensitivity of HCC and might help us to understand how to use the SIRT3-modulated mito-COX-2/p-Drp1^Ser616 signaling axis to develop an effective clinical intervention in hepatocarcinogenesis.

Metabolic response to radiation therapy in cancer

Tumor metabolism has emerged as a hallmark of cancer and is involved in carcinogenesis and tumor growth. Reprogramming of tumor metabolism is necessary for cancer cells to sustain high proliferation rates and enhanced demands for nutrients. Recent studies suggest that metabolic plasticity in cancer cells can decrease the efficacy of anticancer therapies by enhancing antioxidant defenses and DNA repair mechanisms. Studying radiation-induced metabolic changes will lead to a better understanding of radiation response mechanisms as well as the identification of new therapeutic targets, but there are few robust studies characterizing the metabolic changes induced by radiation therapy in cancer. In this review, we will highlight studies that provide information on the metabolic changes induced by radiation and oxidative stress in cancer cells and the associated underlying mechanisms.

Mitochondrial fragmentation is crucial for c-Myc-driven hepatoblastoma-like liver tumor

Hepatoblastoma is the most common liver cancer in children, and the aggressive subtype often has a poor prognosis and lacks effective targeted therapy. Although aggressive hepatoblastoma (HB) is often accompanied by abnormally high expression of the transcription factor c-Myc, the underlying mechanism remains unclear. In this study, we found that mitochondrial fragmentation was enhanced by c-Myc overexpression in human aggressive HB tissues and was associated with poor prognosis. Then, a mouse model resembling human HB was established via hydrodynamic injection of c-Myc plasmids. We observed that liver-specific knockout of the mitochondrial fusion molecule MFN1 or overexpression of mitochondrial fission molecule DRP1 promoted the occurrence of c-Myc-driven liver cancer. In contrast, when MFN1 was overexpressed in the liver, tumor formation was delayed. In vitro experiments showed that c-Myc transcriptionally upregulated the expression of DRP1 and decreased MFN1 expression through upregulation of miR-373-3p. Moreover, enhanced mitochondrial fragmentation significantly promoted aerobic glycolysis and the proliferation of HB cells by significantly increasing reactive oxygen species (ROS) production and activating the RAC-alpha serine/threonine-protein kinase (AKT)/mammalian target of rapamycin (mTOR) and nuclear factor κB (NF-κB) pathways. Taken together, our results indicate that c-Myc-mediated mitochondrial fragmentation promotes the malignant transformation and progression of HB by activating ROS-mediated multi-oncogenic signaling.

USP53 activated by H3K27 acetylation regulates cell viability, apoptosis, and metabolism in esophageal carcinoma via the AMPK signaling pathway

Esophageal carcinoma (ESCA) is a leading cause of cancer death worldwide, despite an overall decline in the incidence of new cases. However, knowledge of gene expression signatures for risk and prognosis stratification of ESCA is inadequate. Thus, identifying novel molecular biomarkers and therapeutic targets for ESCA might improve its prognosis and treatment. The current study investigated the role of ubiquitin-specific peptidase 53 (USP53), a member of the USP family that exhibits deubiquitinating activity, in ESCA and showed that USP53 is downregulated in ESCA tissues, indicating poor prognosis. USP53 suppresses the proliferation and growth of ESCA cells in vitro and in vivo, whereas its knockdown exerts opposite effects. AMP-activated protein kinase inhibitor reverses the effects of USP53 knockdown. USP53 also inhibits glycolysis, oxidative metabolism, and mitochondrial dynamics. H3K27 acetylation increases USP53 expression by binding to its promoter region. Our study reveals that USP53 is activated by H3K27 acetylation and suppresses ESCA progression by regulating cell growth and metabolism. USP53 is therefore a promising target for ESCA treatment.

Mitochondrial Mechanisms of Apoptosis and Necroptosis in Liver Diseases

In addition to playing a pivotal role in cellular energetics and biosynthesis, mitochondrial components are key operators in the regulation of cell death. In addition to apoptosis, necrosis is a highly relevant form of programmed liver cell death. Differential activation of specific forms of programmed cell death may not only affect the outcome of liver disease but may also provide new opportunities for therapeutic intervention. This review describes the role of mitochondria in cell death and the mechanism that leads to chronic liver hepatitis and liver cirrhosis. We focus on mitochondrial-driven apoptosis and current knowledge of necroptosis and discuss therapeutic strategies for targeting mitochondrial-mediated cell death in liver diseases.

The multifaceted roles of mitochondria at the crossroads of cell life and death in cancer

Mitochondria are the cytoplasmic organelles mostly known as the "electric engine" of the cells; however, they also play pivotal roles in different biological processes, such as cell growth/apoptosis, Ca²⁺ and redox homeostasis, and cell stemness. In cancer cells, mitochondria undergo peculiar functional and structural dynamics involved in the survival/death fate of the cell. Cancer cells use glycolysis to support macromolecular biosynthesis and energy production ("Warburg effect"); however, mitochondrial OXPHOS has been shown to be still active during carcinogenesis and even exacerbated in drug-resistant and stem cancer cells. This metabolic rewiring is associated with mutations in genes encoding mitochondrial metabolic enzymes ("oncometabolites"), alterations of ROS production and redox biology, and a fine-tuned balance between anti-/proapoptotic proteins. In cancer cells, mitochondria also experience dynamic alterations from the structural point of view undergoing coordinated cycles of biogenesis, fusion/fission and mitophagy, and physically communicating with the endoplasmic reticulum (ER), through the Ca²⁺ flux, at the MAM (mitochondria-associated membranes) levels. This review addresses the peculiar mitochondrial metabolic and structural dynamics occurring in cancer cells and their role in coordinating the balance between cell survival and death. The role of mitochondrial dynamics as effective biomarkers of tumor progression and promising targets for anticancer strategies is also discussed.

Estrogen Receptor Beta (ERβ) Maintains Mitochondrial Network Regulating Invasiveness in an Obesity-Related Inflammation Condition in Breast Cancer

Obesity, a physiological situation where different proinflammatory cytokines and hormones are secreted, is a major risk factor for breast cancer. Mitochondrial functionality exhibits a relevant role in the tumorigenic potential of a cancer cell. In the present study, it has been examined the influence of an obesity-related inflammation ELIT treatment (17β-estradiol, leptin, IL-6, and TNFα), which aims to stimulate the hormonal conditions of a postmenopausal obese woman on the mitochondrial functionality and invasiveness of MCF7 and T47D breast cancer cell lines, which display a different ratio of both estrogen receptor isoforms, ERα and ERβ. The results showed a decrease in mitochondrial functionality, with an increase in oxidative stress and invasiveness and motility, in the MCF7 cell line (high ERα/ERβ ratio) compared to a maintained status in the T47D cell line (low ERα/ERβ ratio) after ELIT treatment. In addition, breast cancer biopsies were analyzed, showing that breast tumors of obese patients present a high positive correlation between IL-6 receptor and ERβ and have an increased expression of cytokines, antioxidant enzymes, and mitochondrial biogenesis and dynamics genes. Altogether, giving special importance to ERβ in the pathology of obese patients with breast cancer is necessary, approaching to personalized medicine.

Potential biomarkers and targets of mitochondrial dynamics

Mitochondrial dysfunction contributes to the imbalance of cellular homeostasis and the development of diseases, which is regulated by mitochondria-associated factors. The present review aims to explore the process of the mitochondrial quality control system as a new source of the potential diagnostic biomarkers and/or therapeutic targets for diseases, including mitophagy, mitochondrial dynamics, interactions between mitochondria and other organelles (lipid droplets, endoplasmic reticulum, endosomes, and lysosomes), as well as the regulation and posttranscriptional modifications of mitochondrial DNA/RNA (mtDNA/mtRNA). The direct and indirect influencing factors were especially illustrated in understanding the interactions among regulators of mitochondrial dynamics. In addition, mtDNA/mtRNAs and proteomic profiles of mitochondria in various lung diseases were also discussed as an example. Thus, alternations of mitochondria-associated regulators can be a new category of biomarkers and targets for disease diagnosis and therapy.

A Root in Synapsis and the Other One in the Gut Microbiome-Brain Axis: Are the Two Poles of Ketogenic Diet Enough to Challenge Glioblastoma?

Glioblastoma is the most frequent and aggressive brain cancer in adults. While precision medicine in oncology has produced remarkable progress in several malignancies, treatment of glioblastoma has still limited available options and a dismal prognosis. After first-line treatment with surgery followed by radiochemotherapy based on the 2005 STUPP trial, no significant therapeutic advancements have been registered. While waiting that genomic characterization moves from a prognostic/predictive value into therapeutic applications, practical and easy-to-use approaches are eagerly awaited. Medical reports on the role of the ketogenic diet in adult neurological disorders and in glioblastoma suggest that nutritional interventions may condition outcomes and be associated with standard therapies. The acceptable macronutrient distribution of daily calories in a regular diet are 45-65% of daily calories from carbohydrates, 20-35% from fats, and 10-35% from protein. Basically, the ketogenic diet follows an approach based on low carbohydrates/high fat intake. In carbohydrates starvation, body energy derives from fat storage which is used to produce ketones and act as glucose surrogates. The ketogenic diet has several effects: metabolic interference with glucose and insulin and IGF-1 pathways, influence on neurotransmission, reduction of oxidative stress and inflammation, direct effect on gene expression through epigenetic mechanisms. Apart from these central effects working at the synapsis level, recent evidence also suggests a role for microbiome and gut-brain axis induced by a ketogenic diet. This review focuses on rationales supporting the ketogenic diet and clinical studies will be reported, looking at future possible perspectives.

Metabolic Response to the Mitochondrial Toxin 1-Methyl-4-phenylpyridinium (MPP+) in LDH-A/B Double-knockout LS174T Colon Cancer Cells

BACKGROUND/AIM

Rapid glycolytic substrate-level phosphorylation (SLP) and accumulation of lactic acid are characteristics of diverse cancers. Recent advances in drug discovery have included the use of glycolytic inhibitors with mitochondrial targeting drugs to attempt to invoke an energy crisis in aggressive metabolically active chemo-resistant cancers. In this work, we examine the consequences of inhibiting mitochondrial oxidative phosphorylation (OXPHOS) with 1-methyl-4-phenylpyridinium (MPP+) in LS14T colon cancer cells containing a genetic double knock out (DKO) of lactic acid dehydrogenase (LDHA and LDHB).

MATERIALS AND METHODS

Several metabolic parameters were evaluated concomitant to whole transcriptomic (WT) mRNA, microRNA, and long intergenic non-coding RNAs using Affymetrix 2.1 human ST arrays.

RESULTS

MPP+ effectively blocked OXPHOS where a compensatory shift toward anaerobic SLP was only observed in the control vector (CV), and not observed in the LDH-A/B DKOs (lacking the ability to produce lactic acid). Despite this, there was an unexpected resilience to MPP+ in the latter in terms of energy, which displayed significantly higher resting baseline respiratory OXPHOS capacity relative to controls. At the transcriptome level, MPP+ invoked 1738 differential expressed genes (DEGs) out of 48,226; LDH-A/B DKO resulted in 855 DEGs while 349 DEGs were found to be overlapping in both groups versus respective controls, including loss of mitochondrial complex I (subunits 3 and 6), cell cycle transcripts and fluctuations in epigenetic chromatin remodeling systems. In terms of energy, the effects of MPP+ in the CV transcripts reflect the funneling of carbon intermediates toward glycolysis. The LDH-A/B DKO transcripts reflect a flow of carbons away from glycolysis toward the production of acetyl-CoA.

CONCLUSION

The findings from this study suggest a metabolic resilience to MPP+ in cancer cells devoid of LDH-A/B, explainable in-part by higher baseline OXPHOS respiratory ATP production, necessitating more toxin to suppress the electron transport chain.

Mitochondria: Insights into Crucial Features to Overcome Cancer Chemoresistance

Mitochondria are key regulators of cell survival and are involved in a plethora of mechanisms, such as metabolism, Ca²⁺ signaling, reactive oxygen species (ROS) production, mitophagy and mitochondrial transfer, fusion, and fission (known as mitochondrial dynamics). The tuning of these processes in pathophysiological conditions is fundamental to the balance between cell death and survival. Indeed, ROS overproduction and mitochondrial Ca²⁺ overload are linked to the induction of apoptosis, while the impairment of mitochondrial dynamics and metabolism can have a double-faceted role in the decision between cell survival and death. Tumorigenesis involves an intricate series of cellular impairments not yet completely clarified, and a further level of complexity is added by the onset of apoptosis resistance mechanisms in cancer cells. In the majority of cases, cancer relapse or lack of responsiveness is related to the emergence of chemoresistance, which may be due to the cooperation of several cellular protection mechanisms, often mitochondria-related. With this review, we aim to critically report the current evidence on the relationship between mitochondria and cancer chemoresistance with a particular focus on the involvement of mitochondrial dynamics, mitochondrial Ca²⁺ signaling, oxidative stress, and metabolism to possibly identify new approaches or targets for overcoming cancer resistance.

The anti-cancer effect of betulinic acid in u937 human leukemia cells is mediated through ROS-dependent cell cycle arrest and apoptosis

Although previous studies have shown anti-cancer activity of betulinic acid (BA), a pentacyclic triterpenoid, against various cancer lines, the underlying molecular mechanisms are not well elucidated. In this study, we evaluated the mechanisms involved in the anti-cancer efficacy of BA in U937 human myeloid leukemia cells. BA exerted a significant cytotoxic effect on U937 cells through blocking cell cycle arrest at the G2/M phase and inducing apoptosis, and that the intracellular reactive oxygen species (ROS) levels increased after treatment with BA. The down-regulation of cyclin A and cyclin B1, and up-regulation of cyclin-dependent kinase inhibitor p21WAF1/CIP1 revealed the G2/M phase arrest mechanism of BA. In addition, BA induced the cytosolic release of cytochrome c by reducing the mitochondrial membrane potential with an increasing Bax/Bcl-2 expression ratio. BA also increased the activity of caspase-9 and -3, and subsequent degradation of the poly (ADP-ribose) polymerase. However, quenching of ROS by N-acetyl-cysteine, an ROS scavenger, markedly abolished BA-induced G2/M arrest and apoptosis, indicating that the generation of ROS plays a key role in inhibiting the proliferation of U937 cells by BA treatment. Taken together, our results provide a mechanistic rationale that BA exhibits anti-cancer properties in U937 leukemia cells through ROS-dependent induction of cell cycle arrest at G2/M phase and apoptosis.

Advances in Understanding Mitochondrial MicroRNAs (mitomiRs) on the Pathogenesis of Triple-Negative Breast Cancer (TNBC)

Triple-negative breast cancer (TNBC) is characterized by poor outcome and the most challenging breast cancer type to treat worldwide. TNBC manifests distinct profile of mitochondrial functions, which dictates reprogrammed metabolism, fosters tumor progression, and notably serves as therapeutic targets. Mitochondrial microRNAs (mitomiRs) are a group of microRNAs that critically modulate mitochondrial homeostasis. By a pathway-centric manner, mitomiRs tightly orchestrate metabolic reprogramming, redox status, cell apoptosis, mitochondrial dynamics, mitophagy, mitochondrial DNA (mtDNA) maintenance, and calcium balance, leading to an emerging field of study in various cancer types, including TNBC. We herein review the recent insights into the roles and mechanism of mitomiRs in TNBC and highlight its clinical value in diagnosis and prognosis as well as vital advances on therapeutics of preclinical and clinical studies.

Dual Specificity Kinase DYRK3 Promotes Aggressiveness of Glioblastoma by Altering Mitochondrial Morphology and Function

Glioblastoma multiforme (GBM) is a malignant primary brain tumor with poor patient prognosis. Although the standard treatment of GBM is surgery followed by chemotherapy and radiotherapy, often a small portion of surviving tumor cells acquire therapeutic resistance and become more aggressive. Recently, altered kinase expression and activity have been shown to determine metabolic flux in tumor cells and metabolic reprogramming has emerged as a tumor progression regulatory mechanism. Here we investigated novel kinase-mediated metabolic alterations that lead to acquired GBM radioresistance and malignancy. We utilized transcriptomic analyses within a radioresistant GBM orthotopic xenograft mouse model that overexpresses the dual specificity tyrosine-phosphorylation-regulated kinase 3 (DYRK3). We find that within GBM cells, radiation exposure induces DYRK3 expression and DYRK3 regulates mammalian target of rapamycin complex 1 (mTORC1) activity through phosphorylation of proline-rich AKT1 substrate 1 (PRAS40). We also find that DYRK3 knockdown inhibits dynamin-related protein 1 (DRP1)-mediated mitochondrial fission, leading to increased oxidative phosphorylation (OXPHOS) and reduced glycolysis. Importantly, enforced DYRK3 downregulation following irradiation significantly impaired GBM cell migration and invasion. Collectively, we suggest DYRK3 suppression may be a novel strategy for preventing GBM malignancy through regulating mitochondrial metabolism.

The first copper(I) complex of anthrahydrazone with potential ROS scavenging activity showed significant in vitro anticancer activity by inducing apoptosis and autophagy

Based on the anticancer pharmacophore of anthrahydrazone and quinoline, a new quinolylanthrahydrazone ligand, 9-AQH (anthracene-9-quinolylhydrazone), was synthesized to further afford four metal complexes, [Co^II(9-AQH)(NO₃)₂(H₂O)] (1), [Ni^II(9-AQH)₂(H₂O)₂]·2NO₃ (2), [Cu^I(9-AQH)₂]·NO₃ (3), [Zn^II(9-AQH)₂(NO₃)]·NO₃ (4), determined by X-ray single crystal diffraction analysis. The reaction of Cu(NO₃)₂ with 9-AQH formed the stable and repeatable copper(I) complex 3. In vitro screening demonstrated only 3 showed significant and broad-spectrum anticancer activity, indicating that Cu(I) played a key role in exerting the anticancer activity. In solution, Cu(I) was not naturally oxidized to Cu(II) suggested by ¹H-NMR (Nuclear Magnetic Resonance) and EPR (Electron Paramagnetic Resonance) analysis. The presence of 3 could also catalyze the H₂O₂ system to give hydroxyl free radicals, suggested by further EPR and electrophoresis assay. At the cellular level, although no obvious Cu(II) signals were detected and the total ROS (Reactive Oxygen Species) scavenging in the tumor cells treated with 3, the potential redox property between Cu(I)/Cu(II), as a key role, should not be denied for the significant anticancer activity of 3, considering the much complicated circumstance and other reductive substances in cells. The anticancer mechanism of 3 on the most sensitive MGC-803 cells pointed to significant cell apoptosis through mitochondrial pathway, rather than cell cycle arrest. While the autophagy observed in tumor cells treated by 3 suggested its complicated anticancer mechanism, and whether there was an intrinsic correlation still needed to be further investigated.