Mitochondria and the hallmarks of cancer

Mitochondrial dysfunction route as a possible biomarker and therapy target for human cancer

Mitochondria are vital organelles found within living cells and have signalling, biosynthetic, and bioenergetic functions. Mitochondria play a crucial role in metabolic reprogramming, which is a characteristic of cancer cells and allows them to assure a steady supply of proteins, nucleotides, and lipids to enable rapid proliferation and development. Their dysregulated activities have been associated with the growth and metastasis of different kinds of human cancer, particularly ovarian carcinoma. In this review, we briefly demonstrated the modified mitochondrial function in cancer, including mutations in mtDNA, reactive oxygen species production, dynamics, apoptosis of cells, autophagy, and calcium excess to maintain cancer genesis, progression, and metastasis. Furthermore, the mitochondrial dysfunction pathway for some genomic, proteomic, and metabolomics modifications in ovarian cancer has been studied. Additionally, ovarian cancer has been linked to targeted therapies and biomarkers found through various alteration processes underlying mitochondrial dysfunction, notably targeting reactive oxygen species, metabolites, rewind metabolic pathways, and chemo-resistant ovarian carcinoma cells.

Chondroitin sulfate-modified antiangiogenic peptide conjugate induces cell apoptosis via the mitochondria-mediated pathway to perform antitumor activity

Tumor growth and metastasis heavily rely on angiogenesis, crucial for solid tumor development. Inhibiting angiogenesis associated with tumors emerges as a potent therapeutic approach. Our previous work synthesized the chondroitin sulfate-modified antiangiogenic peptide CS-ES2-AF (CS-EA), which exhibited better antiangiogenic activity, longer half-life, and more robust targeting. In this work, we further evaluated the stability in vitro, cellular uptake mechanism, cell apoptosis mechanism, antitumor activity in vivo, and safety of CS-EA. The stability of CS-EA was consistently superior to that of EA at different temperatures and in different pH ranges. Furthermore, CS-EA mainly entered EAhy926 cells through the clathrin-mediated endocytosis pathway. CS-EA inhibited endothelial cell proliferation, and induced cell apoptosis through downregulating the Bcl-2, reducing mitochondria membrane potential, upregulating cytochrome c, Caspase 3, and reactive oxygen species levels. CS-EA showed better antitumor activity in the B16 xenografted tumor model, with a tumor inhibition rate 1.92 times higher than EA. Simultaneously, it was observed that CS-EA did not cause any harmful effects on the vital organs of the mice. These findings indicate that CS-EA holds significant promise for the treatment of tumors.

Different impact of vitamin D on mitochondrial activity and morphology in normal and malignant keratinocytes, the role of genomic pathway

Deregulation of mitochondria activity is one of the hallmarks of cancerogenesis and an important target for cancer therapy. Therefore, we compared the impact of an active form of vitamin D3 (1,25(OH)2D3) on mitochondrial morphology and bioenergetics in human squamous cell carcinoma (A431) and immortalized HaCaT keratinocytes. It was shown that mitochondria of cancerous A431 cells differ from that observed in HaCaT keratinocytes in terms of network, morphology, bioenergetics, glycolysis, and mitochondrial DNA copy number, while treatment of A431 with 1,25(OH)2D3 partially eliminates these differences. Furthermore, mitochondrial membrane potential, basal respiration, and mitochondrial reactive oxygen species production were decreased in A431 cells treated with 1,25(OH)2D3. Additionally, the expression and protein level of mitophagy marker PINK1 was significantly increased in A431 1,25(OH)2D3 treated cells, but not observed in treated HaCaT cells. Knockout of VDR (vitamin D receptor) or RXRA (binding partner retinoid X receptor) partially altered mitochondrial morphology and function as well as mitochondrial response to 1,25(OH)2D3. Transcriptomic analysis on A431 cells treated with 1,25(OH)2D3 revealed modulation of expression of several mitochondrial-related genes involved in mitochondrial depolarization, mitochondrial protein translation (i.e. LYRM9, MARS2), and fusion-fission (OPA1, FIS1, MFN1 and 2), however, none of the genes coded by mitochondrial DNA was affected. Interestingly, in silico analyses of nuclear-encoded mitochondrial genes revealed that they are rather activated by the secondary genomic response to 1,25(OH)2D3. Taken together, 1,25(OH)2D3 remodels mitochondrial architecture and bioenergetics through VDR-dependent and only partially RXRA-dependent activation of the genomic pathway, thus outlining a new perspective for anticancer properties of vitamin D3 in relation to mitochondria in squamous cell carcinoma.

Tumor Microenvironment Heterogeneity, Potential Therapeutic Avenues, and Emerging Therapies

OBJECTIVE

This review describes the comprehensive portrait of tumor microenvironment (TME). Additionally, we provided a panoramic perspective on the transformation and functions of the diverse constituents in TME, and the underlying mechanisms of drug resistance, beginning with the immune cells and metabolic dynamics within TME. Lastly, we summarized the most auspicious potential therapeutic strategies.

RESULTS

TME is a unique realm crafted by malignant cells to withstand the onslaught of endogenous and exogenous therapies. Recent research has revealed many small-molecule immunotherapies exhibiting auspicious outcomes in preclinical investigations. Furthermore, some pro-immune mechanisms have emerged as a potential avenue. With the advent of nanosystems and precision targeting, targeted therapy has now transcended the "comfort zone" erected by cancer cells within TME.

CONCLUSION

The ceaseless metamorphosis of TME fosters the intransigent resilience and proliferation of tumors. However, existing therapies have yet to surmount the formidable obstacles posed by TME. Therefore, scientists should investigate potential avenues for therapeutic intervention and design innovative pharmacological and clinical technologies.

Extracellular pyruvate kinase M2 induces cell migration through p-Tyr42 RhoA-mediated superoxide generation and epithelial-mesenchymal transition

In the tumor microenvironment (TME), communication between cancer cells and tumor-associated macrophages (TAMs) through secreted extracellular proteins promotes cancer progression. Here, we observed that co-culturing cancer cells (4T1) and macrophage cells (Raw264.7) significantly enhanced superoxide production in both cell types. Using MALDI-TOF, we identified PKM2 as a highly secreted protein by Raw264.7 cells and bone marrow-derived monocytes. The extracellular recombinant PKM2 protein not only enhanced cancer cell migration and invasion but also increased superoxide production. Additionally, PKM2 was found to associate with the cell surface, and its binding to integrin α5/β1 receptor was inhibited by antibodies specifically targeting it. Furthermore, we investigated downstream signaling pathways involved in PKM2-induced superoxide production. We found that knock-down of RhoA and p47phox using siRNAs effectively abolished superoxide generation in response to extracellular PKM2. Notably, extracellular PKM2 triggered the phosphorylation of p47phox at Ser345 residue and RhoA at Tyr42 residue (p-Tyr42 RhoA). Moreover, extracellular PKM2 exerted regulatory control over the expression of key epithelial-mesenchymal transition (EMT) markers, including ZEB1, Snail1, vimentin, and E-cadherin. Interestingly, p-Tyr42 RhoA translocated to the nucleus, where it bound to the ZEB1 promoter region. In light of these findings, we propose that extracellular PKM2 within the TME plays a critical role in tumorigenesis by promoting cancer cell migration and invasion through RhoA/p47phox signaling pathway.

Sustainable Nanoparticles from Stephania glabra and Analysis of Their Anticancer Potential on 2D and 3D Models of Prostate Cancer

In pursuit of a novel effective treatment for prostate cancer, methanolic extract of Stephania glabra tubers (Sg-ME) was utilized to fabricate silver (Sg-AgNP), copper oxide (Sg-CuONP), and silver-copper bimetallic nanoparticles (Sg-BNP). The characterization of the nanoparticles confirmed spherical shape with average diameters of 30.72, 32.19, and 25.59 nm of Sg-AgNP, Sg-CuONP, and Sg-BNP, respectively. Interestingly, these nanoparticles exhibited significant cytotoxicity toward the prostate cancer (PC3) cell line while being non-toxic toward normal cells. The nanoparticles were capable of inducing apoptosis in PC3 cells by enhancing reactive oxygen species (ROS) generation and mitochondrial depolarization. Furthermore, the shrinkage of 3D prostate tumor spheroids was observed after 4 days of treatment with these green nanoparticles. The 3D model system was less susceptible to nanoparticles as compared to the 2D model system. Sg-BNP showed the highest anticancer potential on 2D and 3D prostate cancer models.

Mutations in Structural Genes of the Mitochondrial Complex IV May Influence Breast Cancer

Although it has gained more attention in recent years, the relationship between breast cancer (BC) and mitochondrial oxidative phosphorylation (OXPHOS) is still not well understood. Importantly, Complex IV or Cytochrome C Oxidase (COX) of OXPHOS is one of the key players in mitochondrial balance. An in silico investigation of mutations in structural genes of Complex IV was conducted in BC, comprising 2107 samples. Our findings show four variants (rs267606614, rs753969142, rs199476128 and rs267606884) with significant pathogenic potential. Moreover, we highlight nine genes (MT-CO1, MT-CO2, MT-CO3, CO4I2, COX5A, COX5B, COX6A2, COX6C and COX7B2) with a potential impact on BC.

Plant-derived extracts and metabolic modulation in leukemia: a promising approach to overcome treatment resistance

Leukemic cells acquire complex and often multifactorial mechanisms of resistance to treatment, including various metabolic alterations. Although the use of metabolic modulators has been proposed for several decades, their use in clinical practice has not been established. Natural products, the so-called botanical drugs, are capable of regulating tumor metabolism, particularly in hematopoietic tumors, which could partly explain the biological activity attributed to them for a long time. This review addresses the most recent findings relating to metabolic reprogramming-Mainly in the glycolytic pathway and mitochondrial activity-Of leukemic cells and its role in the generation of resistance to conventional treatments, the modulation of the tumor microenvironment, and the evasion of immune response. In turn, it describes how the modulation of metabolism by plant-derived extracts can counteract resistance to chemotherapy in this tumor model and contribute to the activation of the antitumor immune system.

Mitochondrial Deoxyribonucleic Acid (mtDNA), Maternal Inheritance, and Their Role in the Development of Cancers: A Scoping Review

Mitochondrial DNA (mtDNA) is a small, circular, double-stranded DNA inherited from the mother during fertilization. Evolutionary evidence supported by the endosymbiotic theory identifies mitochondria as an organelle that could have descended from prokaryotes. This may be the reason for the independent function and inheritance pattern shown by mtDNA. The unstable nature of mtDNA due to the lack of protective histones, and effective repair systems make it more vulnerable to mutations. The mtDNA and its mutations could be maternally inherited thereby predisposing the offspring to various cancers like breast and ovarian cancers among others. Although mitochondria are considered heteroplasmic wherein variations among the multiple mtDNA genomes are noticed, mothers can have mitochondrial populations that are homoplasmic for a given mitochondrial mutation. Homoplasmic mitochondrial mutations may be transmitted to all maternal offspring. However, due to the complex interplay between the mitochondrial and nuclear genomes, it is often difficult to predict disease outcomes, even with homoplasmic mitochondrial populations. Heteroplasmic mtDNA mutations can be maternally inherited, but the proportion of mutated alleles differs markedly between offspring within one generation. This led to the genetic bottleneck hypothesis, explaining the rapid changes in allele frequency witnessed during the transmission of mtDNA from one generation to the next. Although a physical reduction in mtDNA has been demonstrated in several species, a comprehensive understanding of the molecular mechanisms is yet to be demonstrated. Despite initially thought to be limited to the germline, there is evidence that blockages exist in different cell types during development, perhaps explaining why different tissues in the same organism contain different levels of mutated mtDNA. In this review, we comprehensively discuss the potential mechanisms through which mtDNA undergoes mutations and the maternal mode of transmission that contributes to the development of tumors, especially breast and ovarian cancers.

Inhibition of pyruvate carboxylase reverses metformin resistance by activating AMPK in pancreatic cancer

AIMS

Pyruvate carboxylase (PC) plays a key role in cancer cell metabolic reprogramming. Whether metabolic reprogramming and PC are related in PDAC is unclear. Here, the effect of PC expression on PDAC tumorigenesis and metabolic reprogramming were evaluated.

MATERIALS AND METHODS

PC protein expression in PDAC and precancerous tissues was measured through immunohistochemistry. The maximum standardized uptake (SUVmax) of ¹⁸F-fluoro-2-deoxy-2-d-glucose (¹⁸F-FDG) in PDAC patient PET/CT scans before surgical resection was retrospectively determined. Stable PC-knockdown and PC-overexpressing cells were established using lentiviruses, and PDAC progression was assessed in vivo and in vitro. Lactate content, ¹⁸F-FDG cell uptake rate, mitochondrial oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured in cells. RNA sequencing revealed and qPCR verified differentially expressed genes (DEGs) after PC knockdown. The signaling pathways involved were determined by Western blotting.

KEY FINDINGS

PC was significantly upregulated in PDAC tissues vs. precancerous tissues. A high SUVmax correlated with PC upregulation. PC knockdown significantly inhibited PDAC progression. Lactate content, SUVmax, and ECAR significantly decreased after PC knockdown. Peroxisome proliferator-activated receptor gamma coactivator-one alpha (PGC-1α) was upregulated after PC knockdown; and PGC1a expression promoted AMPK phosphorylation to activate mitochondrial metabolism. Metformin significantly inhibited mitochondrial respiration after PC knockdown, further activated AMPK and downstream carnitine palmitoyltransferase 1A (CPT1A)-regulated fatty acid oxidation (FAO), and inhibited PDAC cells progression.

SIGNIFICANCE

PDAC cell uptake of FDG was positively correlated with PC expression. PC promotes PDAC glycolysis, and reducing PC expression can increase PGC1a expression, activate AMPK, and restore metformin sensitivity.

Evolving strategies and application of proteins and peptide therapeutics in cancer treatment

Several proteins and peptides have therapeutic potential and can be used for cancer therapy. By binding to cell surface receptors and other indicators uniquely linked with or overexpressed on tumors compared to healthy tissue, protein biologics enhance the active targeting of cancer cells, as opposed to the passive targeting of cells by conventional small-molecule chemotherapeutics. This study focuses on peptide medications that exist to slow or stop tumor growth and the spread of cancer, demonstrating the therapeutic potential of peptides in cancer treatment. As an alternative to standard chemotherapy, peptides that selectively kill cancer cells while sparing healthy tissue are developing. A mountain of clinical evidence supports the efficacy of peptide-based cancer vaccines. Since a single treatment technique may not be sufficient to produce favourable results in the fight against cancer, combination therapy is emerging as an effective option to generate synergistic benefits. One example of this new area is the use of anticancer peptides in combination with nonpeptidic cytotoxic drugs or the combination of immunotherapy with conventional therapies like radiation and chemotherapy. This review focuses on the different natural and synthetic peptides obtained and researched. Discoveries, manufacture, and modifications of peptide drugs, as well as their contemporary applications, are summarized in this review. We also discuss the benefits and difficulties of potential advances in therapeutic peptides.

A novel mitochondria-related gene signature in esophageal carcinoma: prognostic, immune, and therapeutic features

Esophageal carcinoma (ESCA) is a common and lethal malignant tumor worldwide. The mitochondrial biomarkers were useful in finding significant prognostic gene modules associated with ESCA owing to the role of mitochondria in tumorigenesis and progression. In the present work, we obtained the transcriptome expression profiles and corresponding clinical information of ESCA from The Cancer Genome Atlas (TCGA) database. Differential expressed genes (DEGs) were overlapped with 2030 mitochondria-related genes to get mitochondria-related DEGs. The univariate cox regression, Least Absolute Shrinkage and Selection Operator (LASSO) regression, and multivariate cox regression were sequentially used to define the risk scoring model for mitochondria-related DEGs, and its prognostic value was verified in the external datasets GSE53624. Based on the risk score, ESCA patients were divided into high- and low-risk groups. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were performed to further investigate the difference between low- and high-risk groups at the gene pathway level. CIBERSORT was used to evaluate immune cell infiltration. The mutation difference between high- and low-risk groups was compared by using the R package "Maftools". Cellminer was used to assess the association between the risk scoring model and drug sensitivity. As the most important outcome of the study, a 6-gene risk scoring model (APOOL, HIGD1A, MAOB, BCAP31, SLC44A2, and CHPT1) was constructed from 306 mitochondria-related DEGs. Pathways including the "hippo signaling pathway" and "cell-cell junction" were enriched in the DEGs between high and low groups. According to CIBERSORT, samples with high-risk scores demonstrated a higher abundance of CD4⁺ T cells, NK cells, M0 and M2 macrophages, and a lower abundance of M1 macrophages. The immune cell marker genes were correlated with the risk score. In mutation analysis, the mutation rate of TP53 was significantly different between the high- and low-risk groups. Drugs with a strong correlation with the risk model were selected. In conclusion, we focused on the role of mitochondria-related genes in cancer development and proposed a prognostic signature for individualized integrative assessment.

MARS2 drives metabolic switch of non-small-cell lung cancer cells via interaction with MCU

Mitochondrial methionyl-tRNA synthetase (MARS2) canonically mediates the formation of fMet-tRNA_i^fMet for mitochondrial translation initiation. Mitochondrial calcium uniporter (MCU) is a major gate of Ca²⁺ flux from cytosol into the mitochondrial matrix. We found that MARS2 interacts with MCU and stimulates mitochondrial Ca²⁺ influx. Methionine binding to MARS2 would act as a molecular switch that regulates MARS2-MCU interaction. Endogenous knockdown of MARS2 attenuates mitochondrial Ca²⁺ influx and induces p53 upregulation through the Ca²⁺-dependent CaMKII/CREB signaling. Subsequently, metabolic rewiring from glycolysis into pentose phosphate pathway is triggered and cellular reactive oxygen species level decreases. This metabolic switch induces inhibition of epithelial-mesenchymal transition (EMT) via cellular redox regulation. Expression of MARS2 is regulated by ZEB1 transcription factor in response to Wnt signaling. Our results suggest the mechanisms of mitochondrial Ca²⁺ uptake and metabolic control of cancer that are exerted by the key factors of the mitochondrial translational machinery and Ca²⁺ homeostasis.

The Prime and Integral Cause of Cancer in the Post-Warburg Era

Back to beginnings. A century ago, Otto Warburg published that aerobic glycolysis and the respiratory impairment of cells were the prime cause of cancer, a phenomenon that since then has been known as "the Warburg effect". In his early studies, Warburg looked at the effects of hydrogen ions (H⁺), on glycolysis in anaerobic conditions, as well as of bicarbonate and glucose. He found that gassing with CO₂ led to the acidification of the solutions, resulting in decreased rates of glycolysis. It appears that Warburg first interpreted the role of pH on glycolysis as a secondary phenomenon, a side effect that was there just to compensate for the effect of bicarbonate. However, later on, while talking about glycolysis in a seminar at the Rockefeller Foundation, he said: "Special attention should be drawn to the remarkable influence of the bicarbonate…". Departing from the very beginnings of this metabolic cancer research in the 1920s, our perspective advances an analytic as well as the synthetic approach to the new "pH-related paradigm of cancer", while at the same time addressing the most fundamental and recent changing concepts in cancer metabolic etiology and its potential therapeutic implications.

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

Phytochemical Targeting of Mitochondria for Breast Cancer Chemoprevention, Therapy, and Sensitization

Breast cancer is a common and deadly disease that causes tremendous physical, emotional, and financial burden on patients and society. Early-stage breast cancer and less aggressive subtypes have promising prognosis for patients, but in aggressive subtypes, and as cancers progress, treatment options and responses diminish, dramatically decreasing survival. Plants are nutritionally rich and biologically diverse organisms containing thousands of metabolites, some of which have chemopreventive, therapeutic, and sensitizing properties, providing a rich source for drug discovery. In this study we review the current landscape of breast cancer with a central focus on the potential role of phytochemicals for treatment, management, and disease prevention. We discuss the relevance of phytochemical targeting of mitochondria for improved anti-breast cancer efficacy. We highlight current applications of phytochemicals and derivative structures that display anti-cancer properties and modulate cancer mitochondria, while describing future applicability and identifying areas of promise.

Effect of pre-low-dose irradiation on anticancer activities of gallic acid in leukemic K562 and K562/Dox cells: cell viability and cellular energetic state studies

The aim of this study was to determine the effects of pre-low-dose irradiation followed by gallic acid (GA) on cell viability and cellular energetic state of leukemic K562 and K562/Dox cells. The cells were irradiated with 0.02, 0.05, and 0.1 Gy of X-rays. For determining cell viability, pre-low-dose irradiation was followed by 10 or 100 µM GA at 24 h post-irradiation, and the cell viability was then determined at 48 h post-irradiation. For cellular energetic state, pre-low-dose irradiation was followed by 10 or 100 µM GA at 1.5 h post-irradiation and the mitochondrial activity, mitochondrial membrane potential (ΔΨm), and ATP level were determined at 3 h post-irradiation. The % cell viability was significantly decreased in both cells that were irradiated with X-rays followed by treatment with 10 or 100 µM GA at 24 h post-irradiation, when compared with control group. However, this did not happen when compared with GA alone without any pre-low-dose irradiation. The mitochondrial activity had significantly decreased in 10 µM GA-treated K562 cells and the mitochondrial activity, ΔΨm, and ATP levels had significantly decreased in 10 µM GA-treated K562/Dox cells after irradiation to X-rays when compared with GA alone group. In addition, the ΔΨm and ATP levels was significantly decreased in only 100 µM GA-treated K562/Dox cells, but was not decreased in 100 µM GA-treated K562 cells after exposure to X-rays. These findings suggest that pre-low-dose irradiation followed by GA could not kill K562 and K562/Dox cells, but could improve cellular energetic damage of GA effects possibly through mitochondrial impairment.

Unraveling Mitochondrial Determinants of Tumor Response to Radiation Therapy

Radiotherapy represents a highly targeted and efficient treatment choice in many cancer types, both with curative and palliative intents. Nevertheless, radioresistance, consisting in the adaptive response of the tumor to radiation-induced damage, represents a major clinical problem. A growing body of the literature suggests that mechanisms related to mitochondrial changes and metabolic remodeling might play a major role in radioresistance development. In this work, the main contributors to the acquired cellular radioresistance and their relation with mitochondrial changes in terms of reactive oxygen species, hypoxia, and epigenetic alterations have been discussed. We focused on recent findings pointing to a major role of mitochondria in response to radiotherapy, along with their implication in the mechanisms underlying radioresistance and radiosensitivity, and briefly summarized some of the recently proposed mitochondria-targeting strategies to overcome the radioresistant phenotype in cancer.

Prediction of CIAPIN1 (Cytokine-Induced Apoptosis Inhibitor 1) Signaling Pathway and Its Role in Cholangiocarcinoma Metastasis

Cholangiocarcinoma (CCA), a malignancy of the biliary epithelium, can arise at any point in the biliary system. We previously reported that CIAPIN1 is detectable in the sera and that its overexpression was associated with poor prognosis and metastasis of CCA patients. In this study, we investigated further its expression in CCA tissues, biological functions, and related signaling pathways in CCA cells. First, we examined CIAPIN1 expression in CCA tissues of 39 CCA patients using immunohistochemistry (IHC). Then, CIAPIN1-related proteins expressed in CCA cells were identified using RNA interference (siRNA) and liquid chromatography–mass spectrometry (LC–MS/MS). To predict the functions and signaling pathways of CIAPIN1 in CCA cells, the identified proteins were analyzed using bioinformatics tools. Then, to validate the biological functions of CIAPIN1 in the CCA cell line, transwell migration/invasion assays were used. CIAPIN1 was overexpressed in CCA tissues compared with adjacent noncancerous tissues. Its overexpression was correlated with lymph node metastasis. Bioinformatic analyses predicted that CIAPIN1 is connected to the TGF-β/SMADs signaling pathway via nitric oxide synthase 1 (NOS1) and is involved in the metastasis of CCA cells. In fact, cell migration and invasion activities of the KKU-100 CCA cell line were significantly suppressed by CIAPIN1 gene silencing. Our results unravel its novel function and potential signaling pathway in metastasis of CCA cells. CIAPIN1 can be a poor prognostic factor and can be a promising target molecule for CCA chemotherapy.

The Regulatory Roles of Mitochondrial Calcium and the Mitochondrial Calcium Uniporter in Tumor Cells

Mitochondria, as the main site of cellular energy metabolism and the generation of oxygen free radicals, are the key switch for mitochondria-mediated endogenous apoptosis. Ca²⁺ is not only an important messenger for cell proliferation, but it is also an indispensable signal for cell death. Ca²⁺ participates in and plays a crucial role in the energy metabolism, physiology, and pathology of mitochondria. Mitochondria control the uptake and release of Ca²⁺ through channels/transporters, such as the mitochondrial calcium uniporter (MCU), and influence the concentration of Ca²⁺ in both mitochondria and cytoplasm, thereby regulating cellular Ca²⁺ homeostasis. Mitochondrial Ca²⁺ transport-related processes are involved in important biological processes of tumor cells including proliferation, metabolism, and apoptosis. In particular, MCU and its regulatory proteins represent a new era in the study of MCU-mediated mitochondrial Ca²⁺ homeostasis in tumors. Through an in-depth analysis of the close correlation between mitochondrial Ca²⁺ and energy metabolism, autophagy, and apoptosis of tumor cells, we can provide a valuable reference for further understanding of how mitochondrial Ca²⁺ regulation helps diagnosis and therapy.

Mitochondrial dynamics regulate genome stability via control of caspase-dependent DNA damage

Mitochondrial dysfunction is interconnected with cancer. Nevertheless, how defective mitochondria promote cancer is poorly understood. We find that mitochondrial dysfunction promotes DNA damage under conditions of increased apoptotic priming. Underlying this process, we reveal a key role for mitochondrial dynamics in the regulation of DNA damage and genome instability. The ability of mitochondrial dynamics to regulate oncogenic DNA damage centers upon the control of minority mitochondrial outer membrane permeabilization (MOMP), a process that enables non-lethal caspase activation leading to DNA damage. Mitochondrial fusion suppresses minority MOMP and its associated DNA damage by enabling homogeneous mitochondrial expression of anti-apoptotic BCL-2 proteins. Finally, we find that mitochondrial dysfunction inhibits pro-apoptotic BAX retrotranslocation, causing BAX mitochondrial localization and thereby promoting minority MOMP. Unexpectedly, these data reveal oncogenic effects of mitochondrial dysfunction that are mediated via mitochondrial dynamics and caspase-dependent DNA damage.

The Search for Cancer Biomarkers: Assessing the Distribution of INDEL Markers in Different Genetic Ancestries

Cancer is a multifactorial group of diseases, being highly incident and one of the leading causes of death worldwide. In Brazil, there is a great variation in cancer incidence and impact among the different geographic regions, partly due to the genetic heterogeneity of the population in this country, composed mainly by European (EUR), Native American (NAM), African (AFR), and Asian (ASN) ancestries. Among different populations, genetic markers commonly present diverse allelic frequencies, but in admixed populations, such as the Brazilian population, data is still limited, which is an issue that might influence cancer incidence. Therefore, we analyzed the allelic and genotypic distribution of 12 INDEL polymorphisms of interest in populations from the five Brazilian geographic regions and in populations representing EUR, NAM, AFR, and ASN, as well as tissue expression in silico. Genotypes were obtained by multiplex PCR and the statistical analyses were done using R, while data of tissue expression for each marker was extracted from GTEx portal. We highlight that all analyzed markers presented statistical differences in at least one of the population comparisons, and that we found 39 tissues to be differentially expressed depending on the genotype. Here, we point out the differences in genotype distribution and gene expression of potential biomarkers for risk of cancer development and we reinforce the importance of this type of study in populations with different genetic backgrounds.

Mitochondrial Dysfunction Pathway Alterations Offer Potential Biomarkers and Therapeutic Targets for Ovarian Cancer

The mitochondrion is a very versatile organelle that participates in some important cancer-associated biological processes, including energy metabolism, oxidative stress, mitochondrial DNA (mtDNA) mutation, cell apoptosis, mitochondria-nuclear communication, dynamics, autophagy, calcium overload, immunity, and drug resistance in ovarian cancer. Multiomics studies have found that mitochondrial dysfunction, oxidative stress, and apoptosis signaling pathways act in human ovarian cancer, which demonstrates that mitochondria play critical roles in ovarian cancer. Many molecular targeted drugs have been developed against mitochondrial dysfunction pathways in ovarian cancer, including olive leaf extract, nilotinib, salinomycin, Sambucus nigra agglutinin, tigecycline, and eupatilin. This review article focuses on the underlying biological roles of mitochondrial dysfunction in ovarian cancer progression based on omics data, potential molecular relationship between mitochondrial dysfunction and oxidative stress, and future perspectives of promising biomarkers and therapeutic targets based on the mitochondrial dysfunction pathway for ovarian cancer.

Parkinson's disease and cancer: a systematic review and meta-analysis on the influence of lifestyle habits, genetic variants, and gender

PURPOSE

The relationship between Parkinson's disease (PD) and cancer has been debated. Gender and genetic influences on cancer development in PD is unclear.

METHODS

Using QUOROM guidelines, we conducted a systematic review and meta-analysis on potential clinical and genetic factors influencing the PD and subsequent cancer relationship. English articles published in PubMed, Web of Science, and SCOPUS from 2010 to 30 August 2020 were considered for suitability.

RESULTS

Of 46 studies identified, fourteen satisfied the inclusion criteria and were further analysed. Unadjusted risk ratios (RR) and 95% confidence intervals were computed to determine the PD and cancer relationship. PD patients have decreased subsequent cancer risks (RR = 0.87, 95% CI = 0.81-0.93), reduced risks of colon, rectal, and colorectal cancer (RR = 0.77, 95% CI = 0.63-0.94), lung cancer (RR = 0.62, 95% CI = 0.48-0.80), and increased brain cancer (R = 1.48, 95% CI = 1.02-2.13) and melanoma risk (R = 1.76, 95% CI = 1.23-2.50). Compared to idiopathic PD, LRRK2-G2019S carriers had increased general cancer risks (RR = 1.26, 95% CI = 1.09-1.46), particularly brain (RR = 2.41, 95% CI = 1.06-5.50), breast (RR = 2.57, 95% CI = 1.19-5.58), colon (RR = 1.83, 95% CI = 1.13-2.99), and haematological cancers (RR = 2.05, 95% CI = 1.07-3.92). Female PD patients have decreased general cancer risks compared to male PD patients in this analysis (RR = 0.83, 95% CI = 0.69-0.98).

CONCLUSION

PD patients have reduced risks of colon, rectal, colorectal cancer and lung cancers and increased risks of brain cancer and melanoma. LRRK2-G2019S carriers have increased cancer risks, particularly brain, breast, colon and blood cancers. Female gender was associated with reduced risks. The role of ethnicity, comorbidities, and lifestyle habits on PD patients' subsequent cancer risk should be further investigated.

Characterization of Mitochondrial Proteome and Function in Luminal A and Basal-like Breast Cancer Subtypes Reveals Alteration in Mitochondrial Dynamics and Bioenergetics Relevant to Their Diagnosis

Breast cancer (BC) is the most prevalent cancer and the one with the highest mortality among women worldwide. Although the molecular classification of BC has been a helpful tool for diagnosing and predicting the treatment of BC, developments are still being made to improve the diagnosis and find new therapeutic targets. Mitochondrial dysfunction is a crucial feature of cancer, which can be associated with cancer aggressiveness. Although the importance of mitochondrial dynamics in cancer is well recognized, its involvement in the mitochondrial function and bioenergetics context in BC molecular subtypes has been scantly explored. In this study, we combined mitochondrial function and bioenergetics experiments in MCF7 and MDA-MB-231 cell lines with statistical and bioinformatics analyses of the mitochondrial proteome of luminal A and basal-like tumors. We demonstrate that basal-like tumors exhibit a vicious cycle between mitochondrial fusion and fission; impaired but not completely inactive mitochondrial function; and the Warburg effect, associated with decreased oxidative phosphorylation (OXPHOS) complexes I and III. Together with the results obtained in the cell lines and the mitochondrial proteome analysis, two mitochondrial signatures were proposed: one signature reflecting alterations in mitochondrial functions and a second signature exclusively of OXPHOS, which allow us to distinguish between luminal A and basal-like tumors.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

Xanthohumol reduces inflammation and cell metabolism in HT29 primary colon cancer cells

Xanthohumol (XN) is a prenylated flavonoid known for its antioxidant and anti-inflammatory effects and has been studied as an anti-cancer agent. In this study, we aimed at analysing the effect of XN on a primary colorectal adenocarcinoma cell line, HT29, on cell viability, inflammatory and antioxidant gene expression, and metabolism. For this purpose, cells were treated with 10 nM and 10 µM XN, and cell viability, H₂O₂ production, lipid peroxidation and gene expression of inflammatory, antioxidant, and mitochondrial-related genes, as well as protein levels of metabolic enzymes, were determined. Results showed no significant effects on cell viability and a general decrease in pro-inflammatory, antioxidant and mitochondrial biogenesis gene expression with the lower concentration of XN. Furthermore, glucose and oxidative metabolism enzymes were also reduced. These results suggest that XN treatment, at low doses, could stop the proliferation and progression of HT29 cells by downregulating inflammatory signals and cell metabolism.

YAP1-mediated regulation of mitochondrial dynamics in IDH1 mutant gliomas

Mutation of the isocitrate dehydrogenase 1 (IDH1) gene leads to the production of oncometabolite D-2-hydroxyglutarate (2-HG) from α-ketoglutarate and is associated with better prognosis in glioma. As Yes-associated protein 1 (YAP1) is an important regulator of tumor progression, its role in glioma expressing IDH1 with an R132H mutation was investigated. Diminished nuclear levels of YAP1 in IDH1 mutant glioma tissues and cell lines were accompanied by decreased levels of mitochondrial transcription factor A (TFAM). Luciferase reporter assays and chromatin immunoprecipitation were used to investigate the functionality of the TEAD2-binding site on the TFAM promoter in mediating its YAP1-dependent expression. YAP1-dependent mitochondrial fragmentation and ROS generation were accompanied by decreased telomerase reverse transcriptase (TERT) levels and increased mitochondrial TERT localization in IDH1 R132H cells. Treatment with the Src kinase inhibitor bosutinib, which prevents extranuclear shuttling of TERT, further elevated ROS in IDH1 R132H cells and triggered apoptosis. Importantly, bosutinib treatment also increased ROS levels and induced apoptosis in IDH1 wild-type cells when YAP1 was concurrently depleted. These findings highlight the involvement of YAP1 in coupling mitochondrial dysfunction with mitochondrial shuttling of TERT to constitute an essential non-canonical function of YAP1 in the regulation of redox homeostasis. This article has an associated First Person interview with the first author of the paper.

Overexpression of NREP Promotes Migration and Invasion in Gastric Cancer Through Facilitating Epithelial-Mesenchymal Transition

The identification of biomarkers and effective therapeutic targets for gastric cancer (GC), the most common cause of cancer-related deaths around the world, is currently a major focus area in research. Here, we examined the utility of Neuronal Regeneration Related Protein (NREP) as a prognostic biomarker and therapeutic target for GC. We assessed the clinical relevance, function, and molecular role of NREP in GC using bioinformatics analysis and experimental validation. Our results showed that in GC, NREP overexpression was significantly associated with a poor prognosis. Our findings also suggested that NREP may be involved in the activation of cancer-associated fibroblasts and the epithelial-mesenchymal transition (EMT), with transforming growth factor β1 mediating both processes. In addition, NREP expression showed a positive correlation with the abundance of M2 macrophages, which are potent immunosuppressors. Together, these results indicate that NREP is overexpressed in GC and affects GC prognosis. Thus, NREP could be a prognostic biomarker and therapeutic target for GC.

TEOA Promotes Autophagic Cell Death via ROS-Mediated Inhibition of mTOR/p70S6k Signaling Pathway in Pancreatic Cancer Cells

Pancreatic cancer is a common malignant tumor with high mortality, and novel therapeutic options have focused on ameliorating its poor prognosis. TEOA, a traditional Chinese herbal medicine, exhibits anti-inflammatory and anti-cancer activities. Our recent study has shown that TEOA inhibits proliferation and induces DNA damage in diffuse large B-cell lymphoma cells by activating the ROS-mediated p38 MAPK pathway. However, its effects on pancreatic cancer cells remain unknown. In the present study, we evaluated the effects of TEOA on the proliferation, migration of pancreatic cancer cells and explored the possible underlying mechanism of action. We found that TEOA significantly inhibited the proliferation and migration of pancreatic cancer cells in a time- and dose-dependent manner. Mechanistically, TEOA significantly induced mitochondrial dysfunction in PANC1 and SW1990 cells, as evidenced by the collapse of the mitochondrial membrane potential, exhausted ATP level, and excessive accumulation of intracellular ROS. Notably, our further experiments showed that TEOA induced autophagic cell death in pancreatic ductal adenocarcinoma cells by inactivating the ROS-dependent mTOR/p70S6k signaling pathway. More importantly, both pharmacological or genetic blocking of the autophagic flux signal could partly restore the cytotoxicity of TEOA, whereas activation of autophagy by rapamycin or EBSS induced starvation facilitated the cytotoxicity of TEOA. Concomitantly, N-acetylcysteine, a ROS scavenger, abolished the inhibition of the mTOR signaling pathway, thus preventing autophagy and restoring cell viability. Taken together, our results reveal that TEOA can lead to ROS-dependent autophagic cell death of pancreatic cancer cells by inducing mitochondrial dysfunction, which might be a promising therapeutic agent for pancreatic cancer.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

Antimony exposure promotes bladder tumor cell growth by inhibiting PINK1-Parkin-mediated mitophagy

Antimony is one of the heavier pnictogens and is widely found in human food chains, water sources, and as an air pollutant. Recent years have seen steadily increasing concentrations of antimony in the ecological environment; critically, several studies have indicated that antimony might pose a tumorigenic risk factor in several cancers. Therefore, antimony toxicity has attracted increasing research attention, with the molecular mechanisms underlying suspected antimony-mediated tumor transformation of greatest interest. Our results showed that the serum concentration of antimony was higher in bladder tumor patients relative to levels in non-tumor patients. Moreover, that such high antimony serum concentration were closely associated with poorer outcome in bladder tumor patients. Additionally, we demonstrated that the presence of antimony promoted both in vitro and in vivo bladder tumor cell growth. Our results also indicated that low-dose antimony resulted in significantly decreased mitochondrial membrane potential, mitochondrial respiratory enzyme complex I/II/III/IV activity, ATP/ADP ratio, and ATP concentration relative to the control group. These findings suggested that antimony caused mitochondrial damage. Finally, we found that low-dose antimony(0.8uM) inhibited mitophagy by deregulating expression of PINK1, Parkin, and p(ser65)-Parkin, and activation of PINK1-Parkin pathway by CCCP could inhibit antimony-induced tumor cell growth. Collectively, this inhibited the proliferation of bladder tumor cells. Overall, our study suggested that antimony promoted bladder tumor cell growth by inhibiting PINK1-Parkin-mediated mitophagy. These findings highlight the therapeutic potential in targeting molecules within this antimony induced-PINK1/Parkin signaling pathway and may offer a new approach for the treatment of bladder cancer.

The Translocator Protein (TSPO) Genetic Polymorphism A147T Is Associated with Worse Survival in Male Glioblastoma Patients

Simple Summary

The translocator protein 18 kDa (TSPO) gene is highly expressed in glioblastoma (GBM), the most common primary malignant brain tumor, which remains one of the most difficult tumors to treat. TSPO is located in the outer mitochondrial membrane and binds cholesterol through its C-terminal domain. One frequent single-nucleotide polymorphism (SNP) rs6971, which changes the alanine 147 into threonine (Ala147Thr), has been found in the C-terminal domain of the TSPO region and dramatically alters the affinity with which TSPO binds drug ligands. However, the potential association between the TSPO genetic variants and GBM clinical outcomes is not known. Here, we evaluated the effects of the Ala147Thr SNP localized in this TSPO region on biological, sex-specific, overall, and progression-free GBM survival. Our findings suggest an association between the TSPO rs6971 variant and adverse outcomes in male GBM patients but not in females. These findings also suggest that the TSPO rs6971 SNP could be used as a prognostic marker of survival in GBM patients.

Abstract

Glioblastoma (GBM) is the most common primary brain tumor in adults, with few available therapies and a five-year survival rate of 7.2%. Hence, strategies for improving GBM prognosis are urgently needed. The translocator protein 18kDa (TSPO) plays crucial roles in essential mitochondria-based physiological processes and is a validated biomarker of neuroinflammation, which is implicated in GBM progression. The TSPO gene has a germline single nucleotide polymorphism, rs6971, which is the most common SNP in the Caucasian population. High TSPO gene expression is associated with reduced survival in GBM patients; however, the relation between the most frequent TSPO genetic variant and GBM pathogenesis is not known. The present study retrospectively analyzed the correlation of the TSPO polymorphic variant rs6971 with overall and progression-free survival in GBM patients using three independent cohorts. TSPO rs6971 polymorphism was significantly associated with shorter overall survival and progression-free survival in male GBM patients but not in females in one large cohort of 441 patients. We observed similar trends in two other independent cohorts. These observations suggest that the TSPO rs6971 polymorphism could be a significant predictor of poor prognosis in GBM, with a potential for use as a prognosis biomarker in GBM patients. These results reveal for the first time a biological sex-specific relation between rs6971 TSPO polymorphism and GBM.

Calotropis gigantea stem bark extract induced apoptosis related to ROS and ATP production in colon cancer cells

Conventional chemotherapeutic agents for colorectal cancer (CRC) cause systemic side effects and eventually become less efficacious owing to the development of drug resistance in cancer cells. Therefore, new therapeutic regimens have focused on the use of natural products. The anticancer activity of several parts of Calotropis gigantea has been reported; however, the effects of its stem bark extract on inhibition of cancer cell proliferation have not yet been examined. In this study, the anticancer activity of C. gigantea stem bark extract, both alone and in combination with 5-fluorouracil (5-FU), was evaluated. A crude ethanolic extract was prepared from dry, powdered C. gigantea barks using 95% ethanol. This was then partitioned to obtain dichloromethane (CGDCM), ethyl acetate, and water fractions. Quantitative analysis of the constituent secondary metabolites and calotropin was performed. These fractions exhibited cytotoxicity in HCT116 and HT-29 cells, with CGDCM showing the highest potency in both the cell lines. A combination of CGDCM and 5-FU significantly enhanced the cytotoxic effect. Moreover, the resistance of normal fibroblast, HFF-1, cells to this combination demonstrated its safety in normal cells. The combination significantly enhanced apoptosis through the mitochondria-dependent pathway. Additionally, the combination reduced adenosine triphosphate production and increased the production of reactive oxygen species, demonstrating the mechanisms involved in the induction of apoptosis. Our results suggest that CGDCM is a promising anti-cancer agent and may enhance apoptosis induction by 5-FU in the treatment of CRC, while minimizing toxicity toward healthy cells.

Apoptosis - Fueling the oncogenic fire

Apoptosis, the most extensively studied form of programmed cell death, is essential for organismal homeostasis. Apoptotic cell death has widely been reported as a tumor suppressor mechanism. However, recent studies have shown that apoptosis exerts noncanonical functions and may paradoxically promote tumor growth and metastasis. The hijacking of apoptosis by cancer cells may arise at different levels, either via the interaction of apoptotic cells with their local or distant microenvironment, or through the abnormal pro-oncogenic roles of the main apoptosis effectors, namely caspases and mitochondria, particularly upon failed apoptosis. In this review, we highlight some of the recently described mechanisms by which apoptosis and these effectors may promote cancer aggressiveness. We believe that a better understanding of the noncanonical roles of apoptosis may be crucial for developing more efficient cancer therapies.

Metabolic Reprogramming: A Friend or Foe to Cancer Therapy?

Drug resistance is a major cause of cancer treatment failure, effectively driven by processes that promote escape from therapy-induced cell death. The mechanisms driving evasion of apoptosis have been widely studied across multiple cancer types, and have facilitated new and exciting therapeutic discoveries with the potential to improve cancer patient care. However, an increasing understanding of the crosstalk between cancer hallmarks has highlighted the complexity of the mechanisms of drug resistance, co-opting pathways outside of the canonical "cell death" machinery to facilitate cell survival in the face of cytotoxic stress. Rewiring of cellular metabolism is vital to drive and support increased proliferative demands in cancer cells, and recent discoveries in the field of cancer metabolism have uncovered a novel role for these programs in facilitating drug resistance. As a key organelle in both metabolic and apoptotic homeostasis, the mitochondria are at the forefront of these mechanisms of resistance, coordinating crosstalk in the event of cellular stress, and promoting cellular survival. Importantly, the appreciation of this role metabolism plays in the cytotoxic response to therapy, and the ability to profile metabolic adaptions in response to treatment, has encouraged new avenues of investigation into the potential of exploiting metabolic addictions to improve therapeutic efficacy and overcome drug resistance in cancer. Here, we review the role cancer metabolism can play in mediating drug resistance, and the exciting opportunities presented by imposed metabolic vulnerabilities.

Metabolic reprogramming by traditional Chinese medicine and its role in effective cancer therapy

Metabolic reprogramming, characterized by alterations of cellular metabolic patterns, is fundamentally important in supporting the malignant behaviors of cancer cells. It is considered as a promising therapeutic target against cancer. Traditional Chinese medicine (TCM) and its bioactive components have been used in cancer therapy for an extended period, and they are well-known for their multi-target pharmacological functions and fewer side effects. However, the detailed and advanced mechanisms underlying the anticancer activities of TCM remain obscure. In this review, we summarized the critical processes of cancer cell metabolic reprogramming, including glycolysis, mitochondrial oxidative phosphorylation, glutaminolysis, and fatty acid biosynthesis. Moreover, we systemically reviewed the regulatory effects of TCM and its bioactive ingredients on metabolic enzymes and/or signal pathways that may impede cancer progress. A total of 46 kinds of TCMs was reported to exert antitumor effects and/or act as chemosensitizers via regulating metabolic processes of cancer cells, and multiple targets and signaling pathways were revealed to contribute to the metabolic-modulating functions of TCM. In conclusion, TCM has its advantages in ameliorating cancer cell metabolic reprogramming by its poly-pharmacological actions. This review may shed some new light on the explicit recognition of the mechanisms of anticancer actions of TCM, leading to the development of natural antitumor drugs based on reshaping cancer cell metabolism.

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.

Betulinic Acid Affects the Energy-Related Proteomic Profiling in Pancreatic Ductal Adenocarcinoma Cells

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a 5-year survival rate of <8%. Therefore, finding new treatment strategies against PDAC cells is an imperative issue. Betulinic acid (BA), a plant-derived natural compound, has shown great potential to combat cancer owing to its versatile physiological functions. In this study, we observed the impacts of BA on the cell viability and migratory ability of PDAC cell lines, and screened differentially expressed proteins (DEPs) by an LC-MS/MS-based proteomics analysis. Our results showed that BA significantly inhibited the viability and migratory ability of PDAC cells under a relatively low dosage without affecting normal pancreatic cells. Moreover, a functional analysis revealed that BA-induced downregulation of protein clusters that participate in mitochondrial complex 1 activity and oxidative phosphorylation, which was related to decreased expressions of RNA polymerase mitochondrial (POLRMT) and translational activator of cytochrome c oxidase (TACO1), suggesting that the influence on mitochondrial function explains the effect of BA on PDAC cell growth and migration. In addition, BA also dramatically increased Apolipoprotein A1 (APOA1) expression and decreased NLR family CARD domain-containing protein 4 (NLRC4) expression, which may be involved in the dampening of PDAC migration. Notably, altered expression patterns of APOA1 and NLRC4 indicated a favorable clinical prognosis of PDAC. Based on these findings, we identified potential proteins and pathways regulated by BA from a proteomics perspective, which provides a therapeutic window for PDAC.

Autophagy and organelle homeostasis in cancer

Beginning with the earliest studies of autophagy in cancer, there have been indications that autophagy can both promote and inhibit cancer growth and progression; autophagy regulation of organelle homeostasis is similarly complicated. In this review we discuss pro- and antitumor effects of organelle-targeted autophagy and how this contributes to several hallmarks of cancer, such as evading cell death, genomic instability, and altered metabolism. Typically, the removal of damaged or dysfunctional organelles prevents tumor development but can also aid in proliferation or drug resistance in established tumors. By better understanding how organelle-specific autophagy takes place and can be manipulated, it may be possible to go beyond the brute-force approach of trying to manipulate all autophagy in order to improve therapeutic targeting of this process in cancer.

Dual laser activatable brominated hemicyanine as a highly efficient and photostable multimodal phototherapy agent

Dual phototherapy agents have attracted great interest in recent years as they offer enhanced cytotoxicity on cancer cells due to the synergistic effect of photodynamic and photothermal therapies (PDT/PTT). In this study, we demonstrate a brominated hemicyanine (HC-1), which is previously shown as mitochondria targeting PDT agent, can also serve as an effective photosensitizer for PTT for the first time under a single (640 nm or 808 nm) and dual laser (640 nm + 808 nm) irradiation. Generation of reactive oxygen species and photothermal conversion as a function of irradiation wavelength and power were studied. Both single wavelength irradiations caused significant phototoxicity in colon and cervical cancer cells after 5 min of irradiation. However, co-irradiation provided near-complete elimination of cancer cells due to synergistic action. This work introduces an easily accessible small molecule-based synergistic phototherapy agent, which holds a great promise towards the realization of local, rapid and highly efficient treatment modalities against cancer.

Nobiletin Exhibits Neuroprotective Effects against Mitochondrial Complex I Inhibition via Regulating Apoptotic Signaling

Nobiletin, a polymethoxylated flavonoid found in citrus, has been studied because of its modulatory functions in cellular signaling cascades, and effects to prevent mitochondrial calcium overload and neuronal cell death. Particularly, we previously reported that nobiletin induced changes in the mitochondrial membrane potential through K⁺ channel regulation, suggesting that nobiletin might exert neuroprotective effects via regulating mitochondrial functions associated with the electron transport chain (ETC) system. This study investigated whether nobiletin regulated mitochondrial dysfunction mediated by ETC system downregulation by inhibiting complex I (CI) and complex III (CIII) in pure mitochondria and the cortical neurons of rats. The results showed that nobiletin significantly reduced mitochondrial reactive oxygen species (ROS) production, inhibited apoptotic signaling, enhanced ATP production and then restored neuronal viability under conditions of CI inhibition, but not CIII inhibition. These effects were attributed to the downregulation of translocation of apoptosis-induced factor (AIF), and the upregulation of CI activity and the expression of antioxidant enzymes such as Nrf2 and HO-1. Together with our previous study, these results indicate that the neuroprotective effects of nobiletin under mitochondrial dysfunction may be associated with its function to activate antioxidant signaling cascades. Our findings suggest the possibility that nobiletin has therapeutic potential in treating oxidative neurological and neurodegenerative diseases mediated by mitochondrial dysfunction.

LONP1 and ClpP cooperatively regulate mitochondrial proteostasis for cancer cell survival

Mitochondrial proteases are key components in mitochondrial stress responses that maintain proteostasis and mitochondrial integrity in harsh environmental conditions, which leads to the acquisition of aggressive phenotypes, including chemoresistance and metastasis. However, the molecular mechanisms and exact role of mitochondrial proteases in cancer remain largely unexplored. Here, we identified functional crosstalk between LONP1 and ClpP, which are two mitochondrial matrix proteases that cooperate to attenuate proteotoxic stress and protect mitochondrial functions for cancer cell survival. LONP1 and ClpP genes closely localized on chromosome 19 and were co-expressed at high levels in most human cancers. Depletion of both genes synergistically attenuated cancer cell growth and induced cell death due to impaired mitochondrial functions and increased oxidative stress. Using mitochondrial matrix proteomic analysis with an engineered peroxidase (APEX)-mediated proximity biotinylation method, we identified the specific target substrates of these proteases, which were crucial components of mitochondrial functions, including oxidative phosphorylation, the TCA cycle, and amino acid and lipid metabolism. Furthermore, we found that LONP1 and ClpP shared many substrates, including serine hydroxymethyltransferase 2 (SHMT2). Inhibition of both LONP1 and ClpP additively increased the amount of unfolded SHMT2 protein and enhanced sensitivity to SHMT2 inhibitor, resulting in significantly reduced cell growth and increased cell death under metabolic stress. Additionally, prostate cancer patients with higher LONP1 and ClpP expression exhibited poorer survival. These results suggest that interventions targeting the mitochondrial proteostasis network via LONP1 and ClpP could be potential therapeutic strategies for cancer.

Emerging insights into mitochondria-specific targeting and drug delivering strategies: Recent milestones and therapeutic implications

Mitochondria are a major intracellular organelle for drug targeting due to its functional roles in cellular metabolism and cell signaling for proliferation and cell death. Mitochondria-targeted treatment strategy could be promising to improve the therapeutic efficacy of cancer while minimizing the adverse side effects. Over the last decades, several studies have explored and focused on mitochondrial functions, which has led to the emergence of mitochondria-specific therapies. Molecules in the mitochondria are considered to be prime targets, and a wide range of molecular strategies have been designed for targeting mitochondria compared with that of the cytosol. In this review, we focused on the molecular mechanisms of mitochondria-specific ligand targeting and selective drug action strategies for targeting mitochondria, including those premised on mitochondrial targeting of signal peptides (MTS), cell-penetrating peptides (CPPs), and use of lipophilic cations. Furthermore, most research has concentrated on specific conjugation of ligands to therapeutic molecules to enhance their effectiveness. There are several variations for the ideal design and development for mitochondrial-targeted drugs, such as selecting a suitable ligand and linker targets. However, some challenges related to drug solubility and selectivity could be resolved using the nanocarrier system. Nanoparticles yield excellent advantages for targeting and transmitting therapeutic drugs, and they offer elegant platforms for mitochondria-specific drug delivery. We explain many of the advanced and proven strategies for multifunctional mitochondria-specific targets, which should contribute to achieving better anticancer therapies in a promising future.

miR-23b-3p Plays an Oncogenic Role in Hepatocellular Carcinoma

BACKGROUND

Reports show miR-23b to be a cancer-related biomarker in various cancer types. Interestingly, it has a dual role of oncogenic and tumor-suppressive functions, depending on the cancer type. This study focused on the unknown association of miR-23b-3p with hepatocellular carcinoma (HCC).

METHODS

Expression of miR-23b-3p was measured in nine HCC cell lines and 125 resected human HCC samples by TaqMan microRNA assays. To detect its downstream target, miR-23b-3p mimic and inhibitor constructs were transfected and analyzed.

RESULTS

HepG2, a high miR-23b-3p-expressing cell line, was transfected with a miR-23b-3p inhibitor construct, whereas SK-Hep1, a low miR-23b-3p-expressing cell line, was transfected with a mimic construct. Proliferation of HCC cells was activated by miR-23b-3p overexpression and diminished by its knockdown. Then, 125 clinical HCC samples were examined to measure miR-23b-3p expression. Tumor expression of miR-23b-3p was upregulated in 48 cases (38%) and downregulated in 77 cases (62%). The upregulated cases were correlated with elderly patients (P = 0.015). These patients also showed significantly poor overall survival [hazard ratio (HR), 3.10; 95% conflidence interval (CI), 1.57-6.29; P = 0.001] in a multivariate analysis. Furthermore, mitochondrial metabolism-related genes (MICU3 and AUH) were detected as specific binding targets.

CONCLUSION

The study showed that miR-23b-3p functions as an oncogenic microRNA in HCC cell lines. Its overexpression in resected HCC tissues was a significant prognostic factor of overall survival. Both MICU3 and AUH may be candidate gene targets of miR-23b-3p.

The Role of Translocator Protein TSPO in Hallmarks of Glioblastoma

Simple Summary

The translocator protein (TSPO) has been under extensive investigation as a specific marker in positron emission tomography (PET) to visualize brain lesions following injury or disease. In recent years, TSPO is increasingly appreciated as a potential novel therapeutic target in cancer. In Glioblastoma (GBM), the most malignant primary brain tumor, TSPO expression levels are strongly elevated and scientific evidence accumulates, hinting at a pivotal role of TSPO in tumorigenesis and glioma progression. The aim of this review is to summarize the current literature on TSPO with respect to its role both in diagnostics and especially with regard to the critical hallmarks of cancer postulated by Hanahan and Weinberg. Overall, our review contributes to a better understanding of the functional significance of TSPO in Glioblastoma and draws attention to TSPO as a potential modulator of treatment response and thus an important factor that may influence the clinical outcome of GBM.

Abstract

Glioblastoma (GBM) is the most fatal primary brain cancer in adults. Despite extensive treatment, tumors inevitably recur, leading to an average survival time shorter than 1.5 years. The 18 kDa translocator protein (TSPO) is abundantly expressed throughout the body including the central nervous system. The expression of TSPO increases in states of inflammation and brain injury due to microglia activation. Not least due to its location in the outer mitochondrial membrane, TSPO has been implicated with a broad spectrum of functions. These include the regulation of proliferation, apoptosis, migration, as well as mitochondrial functions such as mitochondrial respiration and oxidative stress regulation. TSPO is frequently overexpressed in GBM. Its expression level has been positively correlated to WHO grade, glioma cell proliferation, and poor prognosis of patients. Several lines of evidence indicate that TSPO plays a functional part in glioma hallmark features such as resistance to apoptosis, invasiveness, and proliferation. This review provides a critical overview of how TSPO could regulate several aspects of tumorigenesis in GBM, particularly in the context of the hallmarks of cancer proposed by Hanahan and Weinberg in 2011.

Involvement of Mitochondrial Mechanisms in the Cytostatic Effect of Desethylamiodarone in B16F10 Melanoma Cells

Previously, we showed that desethylamiodarone (DEA), a major metabolite of the widely used antiarrhythmic drug amiodarone, has direct mitochondrial effects. We hypothesized that these effects account for its observed cytotoxic properties and ability to limit in vivo metastasis. Accordingly, we examined DEA’s rapid (3–12 h) cytotoxicity and its early (3–6 h) effects on various mitochondrial processes in B16F10 melanoma cells. DEA did not affect cellular oxygen radical formation, as determined using two fluorescent dyes. However, it did decrease the mitochondrial transmembrane potential, as assessed by JC-1 dye and fluorescence microscopy. It also induced mitochondrial fragmentation, as visualized by confocal fluorescence microscopy. DEA decreased maximal respiration, ATP production, coupling efficiency, glycolysis, and non-mitochondrial oxygen consumption measured by a Seahorse cellular energy metabolism analyzer. In addition, it induced a cyclosporine A–independent mitochondrial permeability transition, as determined by Co²⁺-mediated calcein fluorescence quenching measured using a high-content imaging system. DEA also caused outer mitochondrial membrane permeabilization, as assessed by the immunoblot analysis of cytochrome C, apoptosis inducing factor, Akt, phospho-Akt, Bad, and phospho-Bad. All of these data supported our initial hypothesis.

Metabolic characterization of aggressive breast cancer cells exhibiting invasive phenotype: impact of non-cytotoxic doses of 2-DG on diminishing invasiveness

Background

Metabolic reprogramming is being recognized as a fundamental hallmark of cancer, and efforts to identify drugs that can target cancer metabolism are underway. In this study, we used human breast cancer (BC) cell lines and established their invading phenotype (INV) collected from transwell inserts to compare metabolome differences and evaluate prognostic significance of the metabolome in aggressive BC invasiveness.

Methods

The invasiveness of seven human BC cell lines were compared using the transwell invasion assay. Among these, INV was collected from SUM149, which exhibited the highest invasiveness. Levels of metabolites in INV were compared with those of whole cultured SUM149 cells (WCC) using CE-TOFMS. The impact of glycolysis in INV was determined by glucose uptake assay using fluorescent derivative of glucose (2-NBDG), and significance of glycolysis, or tricarboxylic acid cycle (TCA) and electron transport chain (ETC) in the invasive process were further determined in aggressive BC cell lines, SUM149, MDA-MB-231, HCC1937, using invasion assays in the presence or absence of inhibitors of glycolysis, TCA cycle or ETC.

Results

SUM149 INV sub-population exhibited a persistent hyperinvasive phenotype. INV were hyper-glycolytic with increased glucose (2-NBDG) uptake; diminished glucose-6-phosphate (G6P) levels but elevated pyruvate and lactate, along with higher expression of phosphorylated-pyruvate dehydrogenase (pPDH) compared to WCC. Notably, inhibiting of glycolysis with lower doses of 2-DG (1 mM), non-cytotoxic to MDA-MB-231 and HCC1937, was effective in diminishing invasiveness of aggressive BC cell lines. In contrast, 3-Nitropropionic acid (3-NA), an inhibitor of succinate dehydrogenase, the enzyme that oxidizes succinate to fumarate in TCA cycle, and functions as complex II of ETC, had no significant effect on their invasiveness, although levels of TCA metabolites or detection of mitochondrial membrane potential with JC-1 staining, indicated that INV cells originally had functional TCA cycles and membrane potential.

Conclusions

Hyper-glycolytic phenotype of invading cells caters to rapid energy production required for invasion while TCA cycle/ETC cater to cellular energy needs for sustenance in aggressive BC. Lower, non-cytotoxic doses of 2-DG can hamper invasion and can potentially be used as an adjuvant with other anti-cancer therapies without the usual side-effects associated with cytotoxic doses.

The Regulatory Role of Mitochondrial MicroRNAs (MitomiRs) in Breast Cancer: Translational Implications Present and Future

Simple Summary

Mitochondrial microRNAs (mitomiRs) are an emerging field of study in a wide range of tumours including breast cancer. By targeting mitochondrial, or non-mitochondrial products, mitomiRs are able to regulate the functions of this organelle, thus controlling multiple carcinogenic processes. The knowledge of this system may provide a novel approach for targeted therapies, as potential biomarkers or helping in the diagnosis of such a complex malignancy.

Abstract

Breast cancer is the most prevalent and incident female neoplasm worldwide. Although survival rates have considerably improved, it is still the leading cause of cancer-related mortality in women. MicroRNAs are small non-coding RNA molecules that regulate the posttranscriptional expression of a wide variety of genes. Although it is usually located in the cytoplasm, several studies have detected a regulatory role of microRNAs in other cell compartments such as the nucleus or mitochondrion, known as “mitomiRs”. MitomiRs are essential modulators of mitochondrion tasks and their abnormal expression has been linked to the aetiology of several human diseases related to mitochondrial dysfunction, including breast cancer. This review aims to examine basic knowledge of the role of mitomiRs in breast cancer and discusses their prospects as biomarkers or therapeutic targets.