OPA1 downregulation is involved in sorafenib-induced apoptosis in hepatocellular carcinoma

Exploring the microRNA-mitochondrial nexus in hepatocellular carcinoma

MicroRNAs (miRNAs) are double-edged swords in hepatocellular carcinoma (HCC) that play a dual role in disease progression and suppression. The pivotal role of miRNAs in gene regulation emphasizes their potential to disrupt critical cellular processes, including mitochondrial function. Given the indispensable role of mitochondria in energy production, apoptosis, and metabolic control, all of which are central to HCC progression, understanding the miRNA-mitochondria axis is crucial. MiRNAs emerge as pivotal regulators of mitochondrial function, exerting profound influence over HCC progression. This comprehensive review delves into the multifaceted roles of miRNAs in modulating mitochondrial biogenesis, dynamics, and apoptosis. MiRNA impacts key metabolic pathways, including energy metabolism, fatty acid metabolism, and oxidative stress. The intricate interplay between miRNAs and mitochondrial function extends to the regulation of mitophagy and ferroptosis. By exploring the microRNA-mitochondrial axis, this review offers insights for identifying novel diagnostic and therapeutic targets.

Mitochondrial Dysfunction-Molecular Mechanisms and Potential Treatment approaches of Hepatocellular Carcinoma

Primary liver cancer (PLC), also known as hepatocellular carcinoma (HCC), is a common type of malignant tumor of the digestive system. Its pathological form has a significant negative impact on the patients' quality of life and ability to work, as well as a significant financial burden on society. Current researches had identified chronic hepatitis B virus infection, aflatoxin B1 exposure, and metabolic dysfunction-associated steatotic liver disease (MASLD) as the main causative factors of HCC. Numerous variables, including inflammatory ones, oxidative stress, apoptosis, autophagy, and others, have been linked to the pathophysiology of HCC. On the other hand, autoimmune regulation, inflammatory response, senescence of the hepatocytes, and mitochondrial dysfunction are all closely related to the pathogenesis of HCC. In fact, a growing number of studies have suggested that mitochondrial dysfunction in hepatocytes may be a key factor in the pathogenesis of HCC. In disorders linked to cancer, mitochondrial dysfunction has gained attention in recent 10 years. As the primary producer of adenosine triphosphate (ATP) in liver cells, mitochondria are essential for preserving cell viability and physiological processes. By influencing multiple pathological processes, including mitochondrial fission/fusion, mitophagy, cellular senescence, and cell death, mitochondrial dysfunction contributes to the development of HCC. We review the molecular mechanisms of HCC-associated mitochondrial dysfunction and discuss new directions for quality control of mitochondrial disorders as a treatment for HCC.

Targeting hyperactive mitochondria in activated HSCs and inhibition of liver fibrogenesis in mice using sorafenib complex micelles

Liver fibrosis is a pathological condition marked by the excessive buildup of extracellular matrix primarily resulting from the transformation of quiescent hepatic stellate cells (HSCs) to myofibroblastic (MF) phenotype and their resultant over-expansion. Activated HSCs completely rely on their hyperactive mitochondria to supply the energy and biomass for their rapid proliferation and collagen secretion, so an intervention targeting their mitochondria can effectively restrict their pathological amplification and contribution to liver fibrosis. Here we tried sorafenib, a drug that plays anticancer roles by inducing the disruption and loss of mitochondrial functions, to reach an antifibrotic goal. And a complex micellar system, VA-PEG-PCL/TPGS (VPP/TPGS), was specifically designed and fabricated to encapsulate and deliver sorafenib selectively to activated HSCs to overcome its application limitations in bioavailability, toxicity and intracellular stay, and eventually maximize its induction of mitochondrial dysfunction and therapeutically antifibrotic efficacy. The prepared sorafenib complex micelles not only exhibited a suitable particle size, uniform morphology, and nice stability, but also performed excellently in the biosafety and HSCs-targetability in vitro and in vivo. In human active HSC cell lines, they markedly attenuated mitochondrial hyperactivity, induced apoptosis, and downregulated fibrosis markers as expected; while in a CCl4-induced murine model of hepatic fibrosis, they effectively restricted the expansion of MF-HSCs, reduced collagen deposition, and promoted the healing of liver damage, showing a good potential in fibrosis curation. Collectively, our VPP/TPGS complex micelles provide an ideal drug delivery platform that has the potential to revolutionize the treatment of liver fibrosis via addressing its cellular and metabolic underpinnings and thus improve patient outcomes.

Assessment of the therapeutic potential of a novel phosphoramidate acyclic nucleoside on induced hepatocellular carcinoma in rat model

AIMS

Hepatocellular Carcinoma (HCC) is renowned as a deadly primary cancer of hepatic origin. Sorafenib is the drug-of-choice for targeted treatment of unresectable end-stage HCC. Unfortunately, great proportion of HCC patients showed intolerance or unresponsiveness to treatment. This study assesses potency of novel ProTide; SH-PAN-19 against N-Nitrosodiethylamine (DEN)-induced HCC in male Wistar rats, compared to Sorafenib.

MAIN METHODS

Structural entity of the synthesized compound was substantiated via FT-IR, UV-Vis, 1H NMR and 13C NMR spectroscopic analysis. In vitro, SH-PAN-19 cytotoxicity was tested against 3 human cell lines; hepatocellular carcinoma; HepG-2, colorectal carcinoma; HCT-116 and normal fibroblasts; MRC-5. In vivo, therapeutic efficacy of SH-PAN-19 (300 mg/kg b.w./day) against HCC could be revealed and compared to that of Sorafenib (15 mg/kg b.w./day) by evaluating the morphometric, biochemical, histopathological, immunohistochemical and molecular key markers.

KEY FINDINGS

SH-PAN-19 was relatively safe toward MRC-5 cells (IC50 = 307.6 μg/mL), highly cytotoxic to HepG-2 cells (IC50 = 24.9 μg/mL) and prominently hepato-selective (TSI = 12.35). Oral LD50 of SH-PAN-19 was >3000 mg/kg b.w. DEN-injected rats suffered hepatomegaly, oxidative stress, elevated liver enzymes, hypoalbuminemia, bilirubinemia and skyrocketed AFP plasma titre. SH-PAN-19 alleviated the DEN-induced alterations in apoptotic, angiogenic and inflammatory markers. SH-PAN-19 produced a 2.5-folds increase in Caspase-9 and downregulated VEGFR-2, IL-6, TNF-α, TGFβ-1, MMP-9 and CcnD-1 to levels comparable to that elicited by Sorafenib. SH-PAN-19 resulted in near-complete pathological response versus partial response achieved by Sorafenib.

SIGNIFICANCE

This research illustrated that SH-PAN-19 is a promising chemotherapeutic agent capable of restoring cellular plasticity and could stop HCC progression.

Mechanistic Insights about Sorafenib-, Valproic Acid- and Metformin-Induced Cell Death in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is among the main causes of death by cancer worldwide, representing about 80-90% of all liver cancers. Treatments available for advanced HCC include atezolizumab, bevacizumab, sorafenib, among others. Atezolizumab and bevacizumab are immunological options recently incorporated into first-line treatments, along with sorafenib, for which great treatment achievements have been reached. However, sorafenib resistance is developed in most patients, and therapeutical combinations targeting cancer hallmark mechanisms and intracellular signaling have been proposed. In this review, we compiled evidence of the mechanisms of cell death caused by sorafenib administered alone or in combination with valproic acid and metformin and discussed them from a molecular perspective.

OMA1 and YME1L as a Diagnostic Panel in Hepatocellular Carcinoma

Identifying new hepatocellular carcinoma (HCC)-driven signaling molecules and discovering their molecular mechanisms are crucial for efficient and better outcomes. Recently, OMA1 and YME1L, the inner mitochondrial proteases, were displayed to be associated with tumor progression in various cancers; however, their role in HCC has not yet been studied. Therefore, we evaluated the possible role of OMA1/YME1L in HCC staging and discussed their potential role in cellular apoptosis and proliferation. Our study was performed using four groups of male albino rats: a normal control and three diethyl nitrosamine-treated groups for 8, 16, and 24 weeks. The OMA1 and YME1L, matrix-metalloproteinase-9 (MMP-9), and cyclin D1 content were measured in liver tissues, while alpha-fetoprotein (AFP) level was assessed in serum. Additionally, Ki-67 expression was evaluated by immunohistochemistry. The relative hepatic expression of Bax, and tissue inhibitor matrix metalloproteinase (TIMP-3) was measured. Herein, we confirmed for the first time that OMA1 is down-regulated while YME1L is up-regulated in HCC in the three studied stages with subsequent inhibition of apoptosis and cell cycle progression. Furthermore, these proteases have a possible role in metastasis. These newly recognized results suggested OMA1 and YME1L as possible diagnostic tools and therapeutic targets for HCC management.

Multi-omics analysis of the oncogenic role of optic atrophy 1 in human cancer

OBJECTIVE

To investigate the prognostic significance of optic atrophy 1 (OPA1) in pan-cancer and analyze the relationship between OPA1 and immune infiltration in cancer.

RESULTS

OPA1 exhibited high expression levels or mutations in various types of tumor cells, and its expression levels were significantly correlated with the survival rate of tumor patients. In different tumor tissues, there was a notable positive correlation between OPA1 expression levels and the infiltration of cancer-associated fibroblasts in the immune microenvironment. Additionally, OPA1 and its related genes were found to be involved in several crucial biological processes, including protein phosphorylation, protein import into the nucleus, and protein binding.

CONCLUSION

OPA1 is highly expressed or mutated in numerous tumors and is strongly associated with protein phosphorylation, patient prognosis, and immune cell infiltration. OPA1 holds promise as a novel prognostic marker with potential clinical utility across various tumor types.

METHODS

We examined OPA1 expression in pan-cancer at both the gene and protein levels using various databases, including Tumor Immune Estimation Resource 2.0 (TIMER 2.0), Gene Expression Profiling Interactive Analysis (GEPIA2), UALCAN, and The Human Protein Atlas (HPA). We utilized the Kaplan-Meier plotter and GEPIA datasets to analyze the relationship between OPA1 expression levels and patient prognosis. Through the cBioPortal database, we detected OPA1 mutations in tumors and examined their relationship with patient prognosis. We employed the TIMER 2.0 database to explore the correlation between OPA1 expression levels in tumor tissue and the infiltration of cancer-associated fibroblasts in the immune microenvironment. Furthermore, we conducted a gene search associated with OPA1 and performed enrichment analysis to identify the main signaling pathways and biological processes linked to them.

FGD5-AS1/miR-5590-3p/PINK1 induces Lenvatinib resistance in hepatocellular carcinoma

BACKGROUND

Lenvatinib is a common systemic treatment for advanced hepatocellular carcinoma (HCC), the resistance to which presents a great challenge. However, the mechanism of lenvatinib resistance in HCC remains unclear. Therefore, elucidating the underlying and key regulatory molecular mechanisms of lenvatinib resistance is urgently needed.

METHODS

Bioinformatic enrichment analysis was used to investigate the gene associated with lenvatinib resistance. RT-PCR, Western blot, immunohistochemistry, and luciferase assays were used to explore the mechanisms of lenvatinib resistance. The effects of the FGD5-AS1/miR-5590-3p/PINK1 axis on lenvatinib resistance were evaluated by colony formation assay, cell viability, apoptosis, mitochondrial homeostasis, and morphology analyses.

RESULTS

Higher expression of PINK1 was observed in lenvatinib-resistant cells and tissues. PINK1 could be activated by increased FGD5-AS1 expression, thereby maintaining the mitochondrial structure and function and promoting the antioxidative stress response. FGD5-AS1/miR-5590-3p showed competitive regulation of PINK1, which affected lenvatinib sensitivity through regulation of mitochondrial structure and antioxidative stress.

CONCLUSIONS

PINK1 was identified as a key gene leading to lenvatinib resistance by maintaining the mitochondrial structure and function. The FGD5-AS1/miR-5590-3p/PINK1 axis may be a promising strategy to overcome lenvatinib resistance in treatment-negative patients.

Mechanisms of Modulation of Mitochondrial Architecture

Mitochondrial network architecture plays a critical role in cellular physiology. Indeed, alterations in the shape of mitochondria upon exposure to cellular stress can cause the dysfunction of these organelles. In this scenario, mitochondrial dynamics proteins and the phospholipid composition of the mitochondrial membrane are key for fine-tuning the modulation of mitochondrial architecture. In addition, several factors including post-translational modifications such as the phosphorylation, acetylation, SUMOylation, and o-GlcNAcylation of mitochondrial dynamics proteins contribute to shaping the plasticity of this architecture. In this regard, several studies have evidenced that, upon metabolic stress, mitochondrial dynamics proteins are post-translationally modified, leading to the alteration of mitochondrial architecture. Interestingly, several proteins that sustain the mitochondrial lipid composition also modulate mitochondrial morphology and organelle communication. In this context, pharmacological studies have revealed that the modulation of mitochondrial shape and function emerges as a potential therapeutic strategy for metabolic diseases. Here, we review the factors that modulate mitochondrial architecture.

Therapeutic efficacy of sorafenib and plant-derived phytochemicals in human colorectal cancer cells

BACKGROUND

The present study aimed to investigate the sequence-dependent anticancer effects of combined treatment with sorafenib (Sora), a Food and Drug Administration-approved multikinase inhibitor drug, and plant-derived phytochemicals (PPCs) on human colorectal cancer (CRC) cell growth, and proteins associated with the control of cell cycle and apoptosis.

METHODS

The cytotoxic effects of 14 PPCs on CRL1554 fibroblast cells were determined using an MTT assay. Moreover, the cytotoxicity of Sora, PPCs, and a combination of both on CRC cells were also investigated. Cell cycle analysis was performed using flow cytometry, and cell apoptosis was investigated using DNA fragmentation, Annexin V/propidium iodide double staining, and mitochondrial membrane potential analyses. The cell cycle- and apoptosis-associated protein expression levels were analysed using western blotting.

RESULTS

Based on their low levels of cytotoxicity in CRL1554 cells at ≤ 20%, curcumin, quercetin, kaempferol, and resveratrol were selected for use in subsequent experiments. The combined treatment of sora and PPCs caused levels of CRC cytotoxicity in a dose-, cell type-, and schedule-dependent manner. Moreover, the combined treatment of CRC cells arrested cell growth at the S and G2/M phases, induced apoptotic cell death, caused extensive mitochondrial membrane damage, and altered the expression of the cell cycle and apoptotic proteins.

CONCLUSIONS

Results of the present study highlighted a difference in the level of sora efficacy in CRC cells when combined with PPCs. Further in vivo and clinical studies using the combined treatment of sora and PPCs are required to determine their potential as a novel therapeutic strategy for CRCs.

Targeting mitochondria as a potential therapeutic strategy against chemoresistance in cancer

The importance of mitochondria is not only limited to energy generation but also in several physical and chemical processes critical for cell survival. Mitochondria play an essential role in cellular apoptosis, calcium ion transport and cellular metabolism. Mutation in the nuclear and mitochondrial genes, altered oncogenes/tumor suppressor genes, and deregulated signalling for cell viability are major reasons for cancer progression and chemoresistance. The development of drug resistance in cancer patients is a major challenge in cancer treatment as the resistant cells are often more aggressive. The drug resistant cells of numerous cancer types exhibit the deregulation of mitochondrial function. The increased biogenesis of mitochondria and its dynamic alteration contribute to developing resistance. Further, a small subpopulation of cancer stem cells in the heterogeneous tumor is primarily responsible for chemoresistance and has an attribute of mitochondrial dysfunction. This review highlights the critical role of mitochondrial dysfunction in chemoresistance in cancer cells through the processes of apoptosis, autophagy/mitophagy, and cancer stemness. Mitochondria-targeted therapeutic strategies might help reduce cancer progression and chemoresistance induced by various cancer drugs.

High-Dose Primaquine Induces Proximal Tubular Degeneration and Ventricular Cardiomyopathy Linked to Host Cells Mitochondrial Dysregulation

Primaquine (PQ) is the only antimalarial medication used to eradicate many species of Plasmodium gametocytes and prevent relapse in vivax and ovale malarias. PQ metabolites induce oxidative stress and impair parasitic mitochondria, leading to protozoal growth retardation and death. Collateral damage is also presented in mammalian host cells, particularly erythrocytes, resulting in hemolysis and tissue destruction. However, the underlying mechanisms of these complications, particularly the mitochondria-mediated cell death of the host, are poorly understood. In the present study, toxicopathological studies were conducted on a rat model to determine the effect of PQ on affected tissues and mitochondrial toxicity. The results indicated that the LD₅₀ for PQ is 200 mg/kg. A high dose of PQ induced hemolytic anemia, elevated a hepatic enzyme (SGPT), and induced proximal tubular degeneration, ventricular cardiomyopathy, and mitochondrial dysregulation. In addition, PQ induced the upregulation of apoptosis-related proteins Drp-1 and caspase-3, with a positive correlation, as well as the pro-apoptotic mitochondrial gene expression of Bax, reflecting the toxic effect of high doses of PQ on cellular damage and mitochondrial apoptosis in terms of hepatotoxicity, nephrotoxicity, and cardiotoxicity. Regarding the risk/benefit ratio of drug administration, our research provides caution for the use of PQ in the treatment of malaria based on its toxicopathological effects.

An autophagy-inducing stapled peptide promotes c-MET degradation and overrides adaptive resistance to sorafenib in c-MET+ hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) accounts for approximately 90% of primary liver cancer cases and ranks as the second leading cause of cancer related death. Multiple receptor tyrosine kinases such as EGFR, FGFR and c-MET have been shown to drive tumorigenesis and progression of HCC. However, tyrosine kinase inhibitors (TKIs) that target these kinases, including the FDA-approved sorafenib, only offer limited clinical success. Resistance to sorafenib and other TKIs also readily emerge in HCC patients, further limiting the usage of these drugs. Novel therapeutic strategies are needed to address the urgent unmet medical need for HCC patients.

Results

Autophagy is an evolutionally conserved lysosome-dependent degradation process that is also functionally implicated in HCC. We previously developed an autophagy-inducing stapled peptide (Tat-SP4) that induced autophagy and endolysosomal degradation of EGFR in lung cancer and breast cancer cells. Here we present data to show that Tat-SP4 also induced significant autophagic response in multiple HCC cell lines and promoted the endolysosomal degradation of c-MET to attenuate its downstream signaling activities although it didn't affect the intrinsically fast turnover of EGFR. Tat-SP4 also overrode adaptive resistance to sorafenib in c-MET⁺ HCC cells but employed the distinct mechanism of inducing non-apoptotic cell death.

Conclusion

With its distinct mechanism of promoting autophagy and endolysosomal degradation of c-MET, Tat-SP4 may serve as a novel therapeutic agent that complement and synergize with sorafenib to enhance its clinical efficacy in HCC patients.

Gankyrin and TIGAR cooperatively accelerate glucose metabolism toward the PPP and TCA cycle in hepatocellular carcinoma

Oncogene-derived metabolic reprogramming is important for anabolic growth of cancer cells, which is now considered to be not simply rely on glycolysis. Pentose phosphate pathway and tricarboxylic acid cycle also play pivotal roles in helping cancer cells to meet their anabolic and energy demands. The present work focused on gankyrin, a relatively specific oncogene in hepatocellular carcinoma (HCC), and its impact on glycolysis and mitochondrial homeostasis. Metabolomics, RNA-seq analysis, and subsequent conjoint analysis illustrated that gankyrin regulated the pentose phosphate pathway (PPP), tricarboxylic acid (TCA) cycle, and mitochondrial function and homeostasis, which play pivotal roles in tumor development. Mechanistically, gankyrin was found to modulate HCC metabolic reprogramming via TIGAR. Gankyrin positively regulated the transcription of TIGAR through Nrf2, which bound to the antioxidant response elements (AREs) in the promoter of TIGAR. Interestingly, TIGAR feedback regulated the transcription of Nrf2 and subsequently gankyrin by promoting nuclear importation of PGC1α. The loop between gankyrin, Nrf2, and TIGAR accelerated glucose metabolism toward the PPP and TCA cycle, which provided vital building blocks, such as NADPH, ATP, and ribose of tumor and further facilitated the progression of HCC.

Iron chelator deferasirox inhibits NF-κB activity in hepatoma cells and changes sorafenib-induced programmed cell deaths

OBJECTIVE

The improvements of antitumor effects and tolerability on chemotherapy for advanced hepatocellular carcinoma (HCC) are warranted. Here, we aimed to elucidate the mechanism of the combining effect of tyrosine kinase inhibitor sorafenib (SOR) and iron chelator deferasirox (DFX) in human hepatoma cell lines, HepG2 and Huh-7.

METHODS

The types of programmed cell deaths (PCDs); necrosis/necroptosis and apoptosis, were evaluated by flow cytometry and fluorescent microscopy. Human cleaved caspase-3 was analyzed by ELISA for apoptosis. GSH assay was used for ferroptosis. PCDs inhibition was analyzed by adding apoptosis inhibitor Z-VAD-FMK, ferroptosis inhibitor ferrostatin-1, necroptosis inhibitor necrosulfonamide, respectively. The expression of NF-κB was quantified by Western blotting.

RESULTS

In SOR monotherapy, cleaved caspase-3 expression was increased in all concentrations, confirming the result that SOR induces apoptosis. In SOR monotherapy, GSH/GSSG ratio was decreased on concentration-dependent, showing that SOR also induced ferroptosis. Lipid Peroxidation caused by SOR, corresponding to ferroptosis, was suppressed by DFX. In fluorescence microscopy of SOR monotherapy, apoptosis was observed at a constant rate on all concentrations, while necroptosis and ferroptosis were increased on high concentration. In sorafenib and deferasirox combinations, sub G1 phase increased additively. In SOR and DFX combinations, the cytotoxic effects were not suppressed by ferrostatin-1, but suppressed by Z-VAD-FMK and necrosulfonamide. In each monotherapy, and SOR + DFX combinations, the expression of NF-κB in nucleus was suppressed. Regarding PCD by SOR and DFX combination, ferroptosis was suppressed and both apoptosis and necroptosis became dominant.

CONCLUSION

Suppression of NF-κB is possibly involved in the effect of DFX. As a result, SOR and DFX combination showed additive antitumor effects for HCC through the mechanism of programed cell deaths and NF-kB signal modification.

Resina Draconis extract exerts anti-HCC effects through METTL3-m6A-Survivin axis

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. Herbal medicines have become an important treasure reservoir for anti-HCC drugs because of their high efficiency and low toxicity. Herein, we investigated whether a 75% ethanol extract from Resina Draconis (ERD) exhibited comprehensive anti-HCC effects both in vivo and in vitro. We revealed that ERD effectively inhibited proliferation and triggered apoptosis of HCC cells in a dose- and time-dependent maner, posing no apparent apoptotic toxicity to normal liver cells. Moreover, ERD significantly inhibited the migration, invasion and metastasis of HCC cells. Importantly, ERD treatment effectively inhibited the growth of xenograft HCC in nude mice with low toxicity and low side effects. Molecular mechanism analysis showed that ERD strongly reduced the expression of anti-apoptotic protein Survivin, ultimately leading to the cleavage activation of apoptosis executive proteins such as Caspase 3 and Poly (ADP-ribose) polymerase (PARP). Survivin gene silencing apparently sensitized the apoptotic effect induced by ERD. Further experiments revealed that ERD inhibited N6-methyladenosine (m⁶ A) modification in Survivin mRNA by downregulating Methyltransferase-like 3 (METTL3) expression and reducing the binding rate of METTL3 and Survivin mRNA. Together, our findings suggest that ERD can be severed as a novel anti-HCC natural product by targeting METTL3-m⁶ A-Survivin axis.

Inhibition of the mitochondrial protein Opa1 curtails breast cancer growth

BACKGROUND

Mitochondrial fusion and fission proteins have been nominated as druggable targets in cancer. Whether their inhibition is efficacious in triple negative breast cancer (TNBC) that almost invariably develops chemoresistance is unknown.

METHODS

We used a combination of bioinformatics analyses of cancer genomic databases, genetic and pharmacological Optic Atrophy 1 (OPA1) inhibition, mitochondrial function and morphology measurements, micro-RNA (miRNA) profiling and formal epistatic analyses to address the role of OPA1 in TNBC proliferation, migration, and invasion in vitro and in vivo.

RESULTS

We identified a signature of OPA1 upregulation in breast cancer that correlates with worse prognosis. Accordingly, OPA1 inhibition could reduce breast cancer cells proliferation, migration, and invasion in vitro and in vivo. Mechanistically, while OPA1 silencing did not reduce mitochondrial respiration, it increased levels of miRNAs of the 148/152 family known to inhibit tumor growth and invasiveness. Indeed, these miRNAs were epistatic to OPA1 in the regulation of TNBC cells growth and invasiveness.

CONCLUSIONS

Our data show that targeted inhibition of the mitochondrial fusion protein OPA1 curtails TNBC growth and nominate OPA1 as a druggable target in TNBC.

A Nanobody-Based Toolset to Monitor and Modify the Mitochondrial GTPase Miro1

The mitochondrial outer membrane (MOM)-anchored GTPase Miro1, is a central player in mitochondrial transport and homeostasis. The dysregulation of Miro1 in amyotrophic lateral sclerosis (ALS) and Parkinson’s disease (PD) suggests that Miro1 may be a potential biomarker or drug target in neuronal disorders. However, the molecular functionality of Miro1 under (patho-) physiological conditions is poorly known. For a more comprehensive understanding of the molecular functions of Miro1, we have developed Miro1-specific nanobodies (Nbs) as novel research tools. We identified seven Nbs that bind either the N- or C-terminal GTPase domain of Miro1 and demonstrate their application as research tools for proteomic and imaging approaches. To visualize the dynamics of Miro1 in real time, we selected intracellularly functional Nbs, which we reformatted into chromobodies (Cbs) for time-lapse imaging of Miro1. By genetic fusion to an Fbox domain, these Nbs were further converted into Miro1-specific degrons and applied for targeted degradation of Miro1 in live cells. In summary, this study presents a collection of novel Nbs that serve as a toolkit for advanced biochemical and intracellular studies and modulations of Miro1, thereby contributing to the understanding of the functional role of Miro1 in disease-derived model systems.

Recent advances in, and challenges of, designing OMA1 drug screens

The proteases of the mitochondrial inner membrane are challenging yet highly desirable drug targets for complex, multifactorial diseases prevalent mainly in the elderly. Among them, OMA1 with its substrates OPA1 and DELE1 safeguards mitochondrial homeostasis at the intersection of energy metabolism and apoptosis, which may have relevance for neurodegeneration, malignancy and heart failure, among other diseases. Little is known about OMA1. Its structure has not been solved and we are just beginning to understand the enzyme's context-dependent regulation. OMA1 appears dormant under physiological conditions as judged by OPA1's processing pattern. The protease is rapidly activated, however, when cells experience stress or undergo apoptosis. Intriguingly, genetic OMA1 ablation can delay or even prevent apoptosis in animal models for diseases that can be broadly categorized as ischemia-reperfusion related disorders. Three groups have reported their efforts implementing OMA1 drug screens. This article reviews some of the technical challenges encountered in these assays and highlights what can be learned for future screening campaigns, and about the OMA1 protease more broadly. OMA1 does not exists in a vacuum and potent OMA1 inhibitors are needed to tease apart OMA1's intricate interactions with the other mitochondrial proteases and enzymes. Furthermore, OMA1 inhibitors hold the promise of becoming a new class of cytoprotective medicines for disorders influenced by dysfunctional mitochondria, such as heart failure or Alzheimer's Disease.

Mitochondria-Shaping Proteins and Chemotherapy

The emergence, in recent decades, of an entirely new area of “Mitochondrial dynamics”, which consists principally of fission and fusion, reflects the recognition that mitochondria play a significant role in human tumorigenesis and response to therapeutics. Proteins that determine mitochondrial dynamics are referred to as “shaping proteins”. Marked heterogeneity has been observed in the response of tumor cells to chemotherapy, which is associated with imbalances in mitochondrial dynamics and function leading to adaptive and acquired resistance to chemotherapeutic agents. Therefore, targeting mitochondria-shaping proteins may prove to be a promising approach to treat chemotherapy resistant cancers. In this review, we summarize the alterations of mitochondrial dynamics in chemotherapeutic processing and the antitumor mechanisms by which chemotherapy drugs synergize with mitochondria-shaping proteins. These might shed light on new biomarkers for better prediction of cancer chemosensitivity and contribute to the exploitation of potent therapeutic strategies for the clinical treatment of cancers.

OMA1 High-Throughput Screen Reveals Protease Activation by Kinase Inhibitors

Mitochondrial proteases are interesting but challenging drug targets for multifactorial diseases, such as neurodegeneration and cancer. The mitochondrial inner membrane protease OMA1 is a bona fide drug target for heart failure supported by data from human linkage analysis and animal disease models, but presumably relevant for more indications. OMA1 acts at the intersection of energy metabolism and stress signaling. The protease cleaves the structural protein OPA1, which organizes the cristae, as well as the signaling peptide DELE1, which can stimulate the integrated stress response. OMA1 shows little activity under physiological conditions but hydrolyzes OPA1 in mitochondria destined for mitophagy and during apoptosis. Little is known about OMA1, its structure has not been solved, let alone its context-dependent regulation. Autocatalytic processing and the lack of OMA1 inhibitors are thereby creating the biggest roadblocks. This study introduces a scalable, cellular OMA1 protease assay suitable for high-throughput drug screening. The assay utilizes an engineered luciferase targeted to the inner membrane as artificial OMA1 substrate, whereby the reporter signal inversely correlates to OMA1 activity. Testing different screening protocols and sampling different compound collections validated the reporter and demonstrated that both OMA1 activators as well as OMA1 inhibitors can be identified with the assay. Ten kinase-targeted cancer drugs triggered OMA1 in the assays, which suggests─considering cardiotoxicity as a rather common side-effect of this class of drugs─cross-reactivity with the OMA1 pathway.

Mitochondrial Quality Control in Hepatocellular Carcinoma

Mitochondria participate in the progression of hepatocellular carcinoma (HCC) by modifying processes including but not limited to redox homeostasis, metabolism, and the cell death pathway. These processes depend on the health status of the mitochondria. Quality control processes in mitochondria can repair or eliminate “unhealthy mitochondria” at the molecular, organelle, or cellular level and form an efficient integrated network that plays an important role in HCC tumorigenesis, patient survival, and tumor progression. Here, we review the influence of mitochondria on the biological behavior of HCC. Based on this information, we further highlight the need for determining the role and mechanism of interaction between different levels of mitochondrial quality control in regulating HCC occurrence and progression as well as resistance development. This information may lead to the development of precision medicine approaches against targets involved in various mitochondrial quality control-related pathways.

Sorafenib for hepatocellular carcinoma: potential molecular targets and resistance mechanisms

Hepatocellular carcinoma (HCC) is the most widespread typical therapy-resistant, unresectable type of malignant solid tumour with a high death rate constituting huge medical concern. Sorafenib is a small molecule oral multi-target kinase potent inhibitor that acts by suppressing/blocking the multiplication of the tumour cells, angiogenesis, and encouraging apoptosis of the tumour cells. Though, the precise mechanism of tumour cell death induction by sorafenib is yet under exploration. Furthermore, genetic heterogeneity plays a critical role in developing sorafenib resistance, which leads the way to identify the need for predictive biomarkers responsible for drug resistance. Therefore, it is essential to find out the fundamental resistance mechanisms to expand therapeutic plans. The authors summarize the molecular concepts of resistance, progression, potential molecular targets, HCC management therapies, and discussion on the advancements expected in the coming future, inclusive of biomarker-driven treatment strategies, which may provide the prospects to design innovative therapeutically targeted strategies for the HCC treatment and the clinical implementation of emerging targeted agents.

Mitochondrial Dynamics and Liver Cancer

Simple Summary

Hepatocellular carcinoma is a leading cause of cancer-related death worldwide. Major risk factors in liver cancer development include chronic hepatitis B or C virus, autoimmune hepatitis, diabetes mellitus, alcohol abuse, and several metabolic diseases, among others. Standard therapy shows low efficacy, and there is an urgent need for novel therapies. Recent data permit to propose that proteins that control mitochondrial morphology through changes in mitochondrial fusion or mitochondrial fission, confer susceptibility or resistance to the development of liver cancer in mouse models. Here, we review the data that suggest mitochondrial dynamics to be involved in the development of liver tumors.

Abstract

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer. Due to its rising incidence and limited therapeutic options, HCC has become a leading cause of cancer-related death worldwide, accounting for 85% of all deaths due to primary liver cancers. Standard therapy for advanced-stage HCC is based on anti-angiogenic drugs such as sorafenib and, more recently, lenvatinib and regorafenib as a second line of treatment. The identification of novel therapeutic strategies is urgently required. Mitochondrial dynamics describes a group of processes that includes the movement of mitochondria along the cytoskeleton, the regulation of mitochondrial morphology and distribution, and connectivity mediated by tethering and fusion/fission events. In recent years, mitochondrial dynamic processes have emerged as key processes in the maintenance of liver mitochondrial homeostasis. In addition, some data are accumulating on the role played by mitochondrial dynamics during cancer development, and specifically on how such dynamics act directly on tumor cells or indirectly on cells responsible for tumor aggression and defense. Here, we review the data that suggest mitochondrial dynamics to be involved in the development of liver tumors.

A Comparison of Doxorubicin-Resistant Colon Cancer LoVo and Leukemia HL60 Cells: Common Features, Different Underlying Mechanisms

Chemoresistance causes cancer relapse and metastasis, thus remaining the major obstacle to cancer therapy. While some light has been shed on the underlying mechanisms, it is clear that chemoresistance is a multifaceted problem strictly interconnected with the high heterogeneity of neoplastic cells. We utilized two different human cell lines, i.e., LoVo colon cancer and promyelocytic leukemia HL60 cells sensitive and resistant to doxorubicin (DXR), largely used as a chemotherapeutic and frequently leading to chemoresistance. LoVo and HL60 resistant cells accumulate less reactive oxygen species by differently modulating the levels of some pro- and antioxidant proteins. Moreover, the content of intracellular magnesium, known to contribute to protect cells from oxidative stress, is increased in DXR-resistant LoVo through the upregulation of MagT1 and in DXR-resistant HL60 because of the overexpression of TRPM7. In addition, while no major differences in mitochondrial mass are observed in resistant HL60 and LoVo cells, fragmented mitochondria due to increased fission and decreased fusion are detected only in resistant LoVo cells. We conclude that DXR-resistant cells evolve adaptive mechanisms to survive DXR cytotoxicity by activating different molecular pathways.

Targeting Mitochondrial Metabolism in Clear Cell Carcinoma of the Ovaries

Ovarian clear cell carcinoma (OCCC) is a rare but chemorefractory tumor. About 50% of all OCCC patients have inactivating mutations of ARID1A, a member of the SWI/SNF chromatin-remodeling complex. Members of the SWI/SNF remodeling have emerged as regulators of the energetic metabolism of mammalian cells; however, the role of ARID1A as a modulator of the mitochondrial metabolism in OCCCs is yet to be defined. Here, we show that ARID1A loss results in increased mitochondrial metabolism and renders ARID1A-mutated cells increasingly and selectively dependent on it. The increase in mitochondrial activity following ARID1A loss is associated with increase in c-Myc expression and increased mitochondrial number and reduction of their size consistent with a higher mitochondrial cristae/outer membrane ratio. Significantly, preclinical testing of the complex I mitochondrial inhibitor IACS-010759 showed it extends overall survival in a preclinical model of ARID1A-mutated OCCC. These findings provide for the targeting mitochondrial activity in ARID1A-mutated OCCCs.

Remodeling of Mitochondrial Plasticity: The Key Switch from NAFLD/NASH to HCC

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and the third-leading cause of cancer-related mortality. Currently, the global burden of nonalcoholic fatty liver disease (NAFLD) has dramatically overcome both viral and alcohol hepatitis, thus becoming the main cause of HCC incidence. NAFLD pathogenesis is severely influenced by lifestyle and genetic predisposition. Mitochondria are highly dynamic organelles that may adapt in response to environment, genetics and epigenetics in the liver ("mitochondrial plasticity"). Mounting evidence highlights that mitochondrial dysfunction due to loss of mitochondrial flexibility may arise before overt NAFLD, and from the early stages of liver injury. Mitochondrial failure promotes not only hepatocellular damage, but also release signals (mito-DAMPs), which trigger inflammation and fibrosis, generating an adverse microenvironment in which several hepatocytes select anti-apoptotic programs and mutations that may allow survival and proliferation. Furthermore, one of the key events in malignant hepatocytes is represented by the remodeling of glucidic-lipidic metabolism combined with the reprogramming of mitochondrial functions, optimized to deal with energy demand. In sum, this review will discuss how mitochondrial defects may be translated into causative explanations of NAFLD-driven HCC, emphasizing future directions for research and for the development of potential preventive or curative strategies.

Mitochondrial dynamics and nonalcoholic fatty liver disease (NAFLD): new perspectives for a fairy-tale ending?

Nonalcoholic fatty liver disease (NAFLD) includes a broad spectrum of liver dysfunctions and it is predicted to become the primary cause of liver failure and hepatocellular carcinoma. Mitochondria are highly dynamic organelles involved in multiple metabolic/bioenergetic pathways in the liver. Emerging evidence outlined that hepatic mitochondria adapt in number and functionality in response to external cues, as high caloric intake and obesity, by modulating mitochondrial biogenesis, and maladaptive mitochondrial response has been described from the early stages of NAFLD. Indeed, mitochondrial plasticity is lost in progressive NAFLD and these organelles may assume an aberrant phenotype to drive or contribute to hepatocarcinogenesis. Severe alimentary regimen and physical exercise represent the cornerstone for NAFLD care, although the low patients' compliance is urging towards the discovery of novel pharmacological treatments. Mitochondrial-targeted drugs aimed to recover mitochondrial lifecycle and to modulate oxidative stress are becoming attractive molecules to be potentially introduced for NAFLD management. Although the path guiding the switch from bench to bedside remains tortuous, the study of mitochondrial dynamics is providing intriguing perspectives for future NAFLD healthcare.

Isobavachalcone inhibits acute myeloid leukemia: Potential role for ROS-dependent mitochondrial apoptosis and differentiation

Isobavachalcone (IBC) has been shown to induce apoptosis and differentiation of acute myeloid leukemia (AML) cells. However, the underlying molecular mechanisms are not fully understood. Herein, IBC exhibited significant inhibition on the cell viability, proliferation, and the colony formation ability of AML cells. Moreover, IBC induced mitochondrial apoptosis evidenced by reduced mitochondrial membrane potential, increased Bax level, decreased Bcl-2, Bcl-xL, and Mcl-1 levels, elevated cytochrome c level in the cytosol and increased cleavage of caspase-9, caspase-3, and PARP. Furthermore, IBC obviously promoted the differentiation of AML cells, accompanied by the increase of the phosphorylation of MEK and ERK and the C/EBPα expression as well as the C/EBPβ LAP/LIP isoform ratio, which was significantly reversed by U0126, a specific inhibitor of MEK. Notably, IBC enhanced the intracellular ROS level. More importantly, IBC-induced apoptosis and differentiation of HL-60 cells were significantly mitigated by NAC. In addition, IBC also exhibited an obvious anti-AML effect in NOD/SCID mice with the engraftment of HL-60 cells. Together, our study suggests that the ROS-medicated signaling pathway is highly involved in IBC-induced apoptosis and differentiation of AML cells.

"The Loss of Golden Touch": Mitochondria-Organelle Interactions, Metabolism, and Cancer

Mitochondria represent the energy hub of cells and their function is under the constant influence of their tethering with other subcellular organelles. Mitochondria interact with the endoplasmic reticulum, lysosomes, cytoskeleton, peroxisomes, and nucleus in several ways, ranging from signal transduction, vesicle transport, and membrane contact sites, to regulate energy metabolism, biosynthetic processes, apoptosis, and cell turnover. Tumorigenesis is often associated with mitochondrial dysfunction, which could likely be the result of an altered interaction with different cell organelles or structures. The purpose of the present review is to provide an updated overview of the links between inter-organellar communications and interactions and metabolism in cancer cells, with a focus on mitochondria. The very recent publication of several reviews on these aspects testifies the great interest in the area. Here, we aim at (1) summarizing recent evidence supporting that the metabolic rewiring and adaptation observed in tumors deeply affect organelle dynamics and cellular functions and vice versa; (2) discussing insights on the underlying mechanisms, when available; and (3) critically presenting the gaps in the field that need to be filled, for a comprehensive understanding of tumor cells’ biology. Chemo-resistance and druggable vulnerabilities of cancer cells related to the aspects mentioned above is also outlined.

OPA1-Exon4b Binds to mtDNA D-Loop for Transcriptional and Metabolic Modulation, Independent of Mitochondrial Fusion

Optic Atrophy 1 (OPA1) has well-established roles in both mitochondrial fusion and apoptotic crista remodeling and is required for the maintenance and distribution of mitochondrial DNA (mtDNA), which are essential for energy metabolism. However, the relationship between OPA1 and mitochondrial metabolism and the underlying mechanisms remain unclear. Here, we show that OPA1-Exon4b modulates mitochondrial respiration and rescues inner mitochondrial membrane potential (Δψm), independent of mitochondrial fusion. OPA1-Exon4b is required for the maintenance of normal TFAM distribution and enhances mtDNA transcription by binding the D-loop of mtDNA. Finally, we show that mRNA levels of OPA1 isoforms containing Exon4b are specifically downregulated in hepatocellular carcinoma (HCC), leading to a reduction in Δψm. Thus, our study demonstrates a novel mitochondrial functional self-recovery pathway involving enhanced mtDNA transcription-mediated recovery of mitochondrial respiratory chain proteins. This mitochondrial fusion-independent pathway may contribute to mitochondrial multi-functional switches in tumorigenesis.

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

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

Enhancement of sorafenib-mediated death of Hepatocellular carcinoma cells by Carnosic acid and Vitamin D2 analog combination

Hepatocellular carcinoma (HCC) is the most common form of liver cancer and it is the third leading cause of global cancer mortality. Sorafenib (Sf) is the first oral multi-kinase inhibitor approved for systemic treatment of advanced HCC, and can prolong survival, although only for three months longer than placebo treated patients. Preclinical studies showed that active forms of vitamin D can induce cell differentiation and regulate cell survival in several cell types, and epidemiological data link vitamin D insufficiency to an increased risk of neoplastic diseases, suggesting a potentially important role of vitamin D in cancer therapy. Other studies showed that the effect of vitamin D analogs on human neoplastic cells is potentiated by carnosic acid (CA), a plant polyphenol with anti-oxidant properties. Here we tested if the addition of the vitamin D2 analog Doxercalciferol (D2) together with CA can enhance the cytotoxic effect of Sf on HCC cell lines Huh7 (Sf-sensitive) and HCO2 (Sf-resistant). Indeed, this combination increased HCC cell death in cell lines, enhancing autophagy as well as apoptosis. Autophagy was confirmed by increased cytoplasmic vacuolation, perinuclear aggregation of LC3, and elevated protein levels of autophagy markers Beclin1, Atg3, and LC3. These results suggest that a regimen which combines a vitamin D2 analog/CA mixture with Sf can be a novel and promising therapeutic option for the treatment of HCC.

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

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

The disturbance of autophagy and apoptosis in the gizzard caused by copper and/or arsenic are related to mitochondrial kinetics

As toxic elements when excessive, arsenic (As) and copper (Cu) are two naturally occurring elements that may be ingested by the organism at the same time. However, the precise damaged mechanism and the pathways that are activated by As and/or Cu is rarely researched in gizzard, a unique organ of birds. In this study, ultrastructural observations, TdT-mediated dUTP Nick-End Labeling, real-time quantitative PCR and Western blotting were performed to evaluate the toxic effects of chronic exposure to Cu²⁺ and/or arsenite on chicken gizzard. The results revealed that increased apoptosis and autophagy levels induced by Cu²⁺ and arsenite appeared to be independent of oxidative stress, which didn't have significant changes in different treatment groups at the same time point. Nevertheless, the redox balance gradually deviated with the extension of time. And increased mitochondrial division and decreased fusion were also caused by Cu²⁺ and arsenite. In conclusion, apoptosis and autophagy in gizzard induced by Cu²⁺ and/or arsenite, at least, strongly linked with the disruption of mitochondrial homeostasis. Our study showed that the combination of Cu²⁺ and arsenite produces stronger toxicity. The results of this study can serve as a reference for agicultural feeding and environmental protection, that is, to avoid the combined exposure of Cu²⁺ and arsenite to prevent greater economic losses and health risks.

Sorafenib kills liver cancer cells by disrupting SCD1-mediated synthesis of monounsaturated fatty acids via the ATP-AMPK-mTOR-SREBP1 signaling pathway

Sorafenib is a multikinase inhibitor that is effective in treating advanced liver cancer. Although its mechanism of action through several established cancer-related protein kinase targets is well-characterized, sorafenib induces variable responses among human tumors, and the cause for this variation is yet unknown. To investigate the underlying mechanisms, we applied mass spectrometry-based proteomic analysis to Huh7.5 human liver cancer cells and found that sorafenib significantly affected the expression of the key lipogenic enzymes, especially stearoyl coenzyme A desaturase 1 (SCD1), in these cells. Given that SCD1 catalyzes the most crucial and rate-limiting step in the synthesis of monounsaturated fatty acids (FAs), we performed a lipidomic analysis, which showed a dramatically altered lipid profile in sorafenib-treated cells. Detection and analysis of free FAs showed that the levels of monounsaturated FAs, including oleate, were significantly decreased in those cells treated by sorafenib. Addition of oleate protected liver cancer cells from sorafenib-induced death and alleviated the abnormalities of mitochondrial morphology and function caused by the drug. Treatment with sorafenib suppressed ATP production, resulting in AMPK activation via phosphorylation. Further secondary effects included reduction of the levels of sterol regulatory element-binding protein 1 (SREBP1) and the phosphorylation of mammalian target of rapamycin (mTOR) in liver cancer cells. These effects were partly abolished in the presence of compound C (an AMPK inhibitor) and ATP and adenosine, and SREBP1c overexpression also could be resistant to the effects of sorafenib, suggesting that the sorafenib-induced reduction in cell viability was mediated by the ATP-AMPK-mTOR-SREBP1 signaling pathway. Taken together, our results suggest that sorafenib's anticancer activity in liver cancer cells is based on the inhibition of ATP production, SCD1 expression, and monounsaturated FA synthesis. In addition, the decreased monounsaturated FA synthesis further triggered the more serious reduction of ATP production in sorafenib-treated cells. To our knowledge, this is the first evidence that sorafenib disrupts lipogenesis and triggers liver cancer cell death by targeting SCD1 through the ATP-AMPK-mTOR-SREBP1 pathway.-Liu, G., Kuang, S., Cao, R., Wang, J., Peng, Q., Sun, C. Sorafenib kills liver cancer cells by disrupting SCD1-mediated synthesis of monounsaturated fatty acids via the ATP-AMPK-mTOR- SREBP1 signaling pathway.

Mitophagy in Cancer: A Tale of Adaptation

：In the past years, we have learnt that tumors co-evolve with their microenvironment, and that the active interaction between cancer cells and stromal cells plays a pivotal role in cancer initiation, progression and treatment response. Among the players involved, the pathways regulating mitochondrial functions have been shown to be crucial for both cancer and stromal cells. This is perhaps not surprising, considering that mitochondria in both cancerous and non-cancerous cells are decisive for vital metabolic and bioenergetic functions and to elicit cell death. The central part played by mitochondria also implies the existence of stringent mitochondrial quality control mechanisms, where a specialized autophagy pathway (mitophagy) ensures the selective removal of damaged or dysfunctional mitochondria. Although the molecular underpinnings of mitophagy regulation in mammalian cells remain incomplete, it is becoming clear that mitophagy pathways are intricately linked to the metabolic rewiring of cancer cells to support the high bioenergetic demand of the tumor. In this review, after a brief introduction of the main mitophagy regulators operating in mammalian cells, we discuss emerging cell autonomous roles of mitochondria quality control in cancer onset and progression. We also discuss the relevance of mitophagy in the cellular crosstalk with the tumor microenvironment and in anti-cancer therapy responses.

Copper-Mediated Mitochondrial Fission/Fusion Is Associated with Intrinsic Apoptosis and Autophagy in the Testis Tissues of Chicken

The aim of this study is to investigate whether copper (Cu) could induce testicular poisoning and influence the mitochondrial dynamics, apoptosis, and autophagy in chickens. For this purpose, thirty-six 1-day-old male Hy-line chickens were divided into control group (C group) and test group (Cu group). The chickens were exposed to 0 (C group) or 300 mg/kg (Cu group) of copper sulfate (CuSO₄) for 30, 60, and 90 days. CuSO₄ was added into the basal diet to make supplements. Testis tissues were subjected to observation of ultrastructure and detection of testis-related indexes. The results indicated that in the test group, the levels of the pro-apoptotic genes were up-regulated and the levels of the anti-apoptotic genes were down-regulated; the levels of mitochondrial fission-related genes markedly increased, and the levels of mitochondrial fusion-related genes were highly decreased; autophagy-related gene (autophagy-associated gene 4B (ATG4B), dynein, microtubule-associated protein 1 light chain 3 beta (LC3-II), ATG5, and beclin-1) levels were increased, while mammalian target of rapamycin (mTOR) and LC3-I levels were declined. The results of transmission electron microscopy (TEM) demonstrated that Cu induced mitochondrial fragmentation, which induced autophagy and apoptosis in chicken testes. In conclusion, CuSO₄ exposure can influence the mitochondrial dynamics balance and lead to mitochondria-initiated intrinsic pathway of apoptosis and autophagy, which triggers the testicular poisoning in chickens. What is more, there is a correlation among mitochondrial dynamics, apoptosis, and autophagy.

Targeted OMA1 therapies for cancer

The mitochondrial inner membrane proteins OMA1 and OPA1 belong to the BAX/BAK1-dependent apoptotic signaling pathway, which can be regulated by tumor protein p53 and the prohibitins PHB and PHB2 in the context of neoplastic disease. For the most part these proteins have been studied separate from each other. Here, I argue that the OMA1 mechanism of action represents the missing link between p53 and cytochrome c release. The mitochondrial fusion protein OPA1 is cleaved by OMA1 in a stress-dependent manner generating S-OPA1. Excessive S-OPA1 can facilitate outer membrane permeabilization upon BAX/BAK1 activation through its membrane shaping properties. p53 helps outer membrane permeabilization in a 2-step process. First, cytosolic p53 activates BAX/BAK1 at the mitochondrial surface. Then, in a second step, p53 binds to prohibitin thereby releasing the restraint on OMA1. This activates OMA1, which cleaves OPA1 and promotes cytochrome c release. Clearly, OMA1 and OPA1 are not root causes for cancer. Yet many cancer cells rely on this pathway for survival, which can explain why loss of p53 function promotes tumor growth and confers resistance to chemotherapies.

Actinidia arguta (Hardy Kiwi) Root Extract Exerts Anti-cancer Effects via Mcl-1-Mediated Apoptosis in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly aggressive and chemoresistant liver malignancy. Thus, identification of strategies to overcome insensitivity to apoptosis and growth inhibition is a growing focus of research in this malignancy. This study evaluated the potential anti-cancer effects of an ethanol extract from the Actinidia arguta (Hardy Kiwi) root (RAE) on CCA. Our data demonstrated that RAE decreased cell viability and induced apoptosis by activation of Caspase 3, Caspase 8, and Poly (ADP-ribose) polymerase (PARP) in two CCA cell lines. RAE induced a decrease in Mcl-1 in cultured CCA cells and in xenograft CCA tumors. Administration of RAE every other day led to significant growth inhibition in tumor burden xenograft CCA mice. Western blotting analysis of paired human CCA and normal adjacent tissues from the same patient revealed that CCA tissues exhibited significantly higher Mcl-1 expression than normal tissues. Taken together, our findings demonstrated the anti-cancer effects of RAE on CCA both in vitro and in vivo. These data suggest that RAE may be a promising anti-CCA agent and could be beneficial in the treatment of CCA through the targeting of Mcl-1.

Dysregulated Mitochondrial Dynamics and Metabolism in Obesity, Diabetes, and Cancer

Metabolism describes the life-sustaining chemical reactions in organisms that provide both energy and building blocks for cellular survival and proliferation. Dysregulated metabolism leads to many life-threatening diseases including obesity, diabetes, and cancer. Mitochondria, subcellular organelles, contain the central energy-producing metabolic pathway, the tricarboxylic acid (TCA) cycle. Also, mitochondria exist in a dynamic network orchestrated by extracellular nutrient levels and intracellular energy needs. Upon stimulation, mitochondria undergo consistent interchange through fusion (small to big) and fission (big to small) processes. Mitochondrial fusion is primarily controlled by three GTPases, mitofusin 1 (Mfn1), Mfn2, and optic atrophy 1 (Opa1), while mitochondrial fission is primarily regulated by GTPase dynamin-related protein 1 (Drp1). Dysregulated activity of these GTPases results in disrupted mitochondrial dynamics and cellular metabolism. This review will update the metabolic roles of these GTPases in obesity, diabetes, and cancer.

Possible Roles of Mitochondrial Dynamics and the Effects of Pharmacological Interventions in Chemoresistant Ovarian Cancer

Ovarian cancer is the major cause of death out of all the gynecologic cancers. The prognosis of this cancer is quite poor since patients only seek treatment when it is at an advanced stage. Any early biomarkers for this cancer are still unknown. Dysregulation of mitochondrial dynamics with associated resistance to apoptosis plays a crucial role in several types of human carcinogenesis, including ovarian cancers. Previous studies showed that increased mitochondrial fission occurred in ovarian cancer cells. However, several pharmacological interventions and therapeutic strategies, which modify the mitochondrial dynamics through the promotion of mitochondrial fission and apoptosis of cancer cells, have been shown to potentially provide beneficial effects in ovarian cancer treatment. Therefore the aim of the present review is to summarize and discuss the current findings from in vitro, in vivo and clinical studies associated with the alteration of mitochondrial dynamics and ovarian cancers with and without interventions.

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Dysregulation of mitochondrial dynamics occurred in ovarian cancer.

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Increased mitochondrial dysregulation may correlate with the increasing degree of chemoresistance in ovarian cancers.

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Drugs-induced mitochondrial fission and apoptosis will be beneficial effect in ovarian cancer therapy.

Interplay between elemental imbalance-related PI3K/Akt/mTOR-regulated apoptosis and autophagy in arsenic (III)-induced jejunum toxicity of chicken

Arsenic trioxide (As₂O₃), the most toxic form of arsenic found in foodstuffs, is considered a carcinogen for human and animal. But many of the events that occur during its passage through the gastrointestinal tract are uncharted in birds. This study assesses the toxic effect on the jejunum of chicken which subchronically exposed to diets that contain As₂O₃ (0, 0.625, 1.25, 2.5 mg/kg body weight) for 90 days. Electron microscopy, TdT-mediated dUTP nick-end labeling (TUNEL), qPCR, and Western blot were performed. The results showed that mitochondrial fusion and apoptosis inhibiting genes had degressive trends, whereas mitochondrial fission and apoptosis activating genes presented heightened expressions in the treatment group compared with the control (P < 0.05). Subsequently, significant inhibition in PI3K/AKT/mTOR signaling was observed. Moreover, the expression of autophagy markers (LC3-II/LC3-I, Beclin-1) increased time and dose-dependently. Additionally, metabolic disorders of trace elements were detected evidenced by their significant decreases (aluminum, silicon, calcium, manganese, strontium, titanium, lithium, boron, cobalt, mercury, chromium) and increases (arsenic, cadmium, selenium, lead, nickel) on 90 days using inductively coupled plasma mass spectrometer (ICP-MS). It is possible that the changes of trace elements have a hand in the come on and development of arsenism. Taken together, we conjectured that, in chicken jejunum, arsenic led to redistribution of trace elements, promoting apoptosis via regulating mitochondrial dynamics, leading to autophagy through PI3K/AKT/mTOR signal pathways.

Sequence‑dependent effect of sorafenib in combination with natural phenolic compounds on hepatic cancer cells and the possible mechanism of action

Sorafenib (Nexavar, BAY43-9006 or Sora) is the first molecular targeted agent that has exhibited significant therapeutic benefits in advanced hepatocellular carcinoma (HCC). However, not all HCC patients respond well to Sora and novel therapeutic strategies to optimize the efficacy of Sora are urgently required. Plant-based drugs have received increasing attention owing to their excellent chemotherapeutic and chemopreventive activities; they are also well tolerated, non-toxic, easily available and inexpensive. It is well known that certain biologically active natural products act synergistically with synthetic drugs used in clinical applications. The present study aimed to investigate whether a combination therapy with natural phenolic compounds (NPCs), including curcumin (Cur), quercetin (Que), kaempherol (Kmf) and resveratrol (Rsv), would allow a dose reduction of Sora without concomitant loss of its effectiveness. Furthermore, the possible molecular mechanisms of this synergy were assessed. The hepatic cancer cell lines Hep3b and HepG2 were treated with Sora alone or in combination with NPCs in concomitant, sequential, and inverted sequential regimens. Cell proliferation, cell cycle, apoptosis and expression of proteins associated with the cell cycle and apoptosis were investigated. NPCs markedly potentiated the therapeutic efficacy of Sora in a sequence-, type-, NPC dose- and cell line-dependent manner. Concomitant treatment with Sora and Cur [sensitization ratio (SR)=28], Kmf (SR=18) or Que (SR=8) was associated with the highest SRs in Hep3b cells. Rsv markedly potentiated the effect of Sora (SR=17) on Hep3b cells when administered in a reverse sequential manner. By contrast, Rsv and Que did not improve the efficacy of Sora against HepG2 cells, while concomitant treatment with Cur (SR=10) or Kmf (SR=4.01) potentiated the cytotoxicity of Sora. Concomitant treatment with Sora and Cur or Kmf caused S-phase and G2/M phase arrest of liver cancer cells and markedly induced apoptosis compared with mono-treatment with Sora, Cur or Kmf. Concomitant treatment with Sora and Cur reduced the protein levels of cyclins A, B2 and D1, phosphorylated retinoblastoma and B-cell lymphoma (Bcl) extra-large protein. By contrast, Sora and Cur co-treatment increased the protein levels of Bcl-2-associated X protein, cleaved caspase-3 and cleaved caspase-9 in a dose-dependent manner. In conclusion, concomitant treatment with Sora and Cur or Kmf appears to be a potent and promising therapeutic approach that may control hepatic cancer by triggering cell cycle arrest and apoptosis. Additional studies are required to examine the potential of combined treatment with Sora and NPCs in human hepatic cancer and other solid tumor types in vivo.

Distinct functions of dynamin isoforms in tumorigenesis and their potential as therapeutic targets in cancer

Dynamins and their related proteins participate in the regulation of neurotransmission, antigen presentation, receptor internalization, growth factor signalling, nutrient uptake, and pathogen infection. Recently, emerging findings have shown dynamin proteins can also contribute to the genesis of cancer. This up-to-date review herein focuses on the functionality of dynamin in cancer development. Dynamin 1 and 2 both enhance cancer cell proliferation, tumor invasion and metastasis, whereas dynamin 3 has tumor suppression role. Antisense RNAs encoded on the DNA strand opposite a dynamin gene regulate the function of dynamin, and manipulate oncogenes and tumor suppressor genes. Certain dynamin-related proteins are also upregulated in distinct cancer conditions, resulting in apoptotic resistance, cell migration and poor prognosis. Altogether, dynamins are potential biomarkers as well as representing promising novel therapeutic targets for cancer treatment. This study also summarizes the current available dynamin-targeted therapeutics and suggests the potential strategy based on signalling pathways involved, providing important information to aid the future development of novel cancer therapeutics by targeting these dynamin family members.

The antagonistic effect of selenium on lead-induced apoptosis via mitochondrial dynamics pathway in the chicken kidney

Selenium (Se) is known to have antagonistic effects against lead (Pb) toxicity in animal. The aim of this study was to evaluate the roles of mitochondrial dynamics on Pb-induced apoptosis in the chicken kidney and investigate the antagonistic effect of Se. In the present study, brown layer chickens were randomly allocated to four groups, and each group were exposed to a basic diet (0.2 mg kg^-1 Se and 0.5 mg kg^-1 Pb), a Se-adequate diet (1 mg kg^-1 Se and 0.5 mg kg^-1 Pb), a Se and Pb compound diet (1 mg kg^-1 Se and 350 mg kg^-1 Pb) or a Pb supplemented diet (0.2 mg kg^-1 Se and 350 mg kg^-1 Pb). On the 90^th day, the kidney was removed to determine the activities of mitochondrial respiratory chain complexes, ATPases and oxidative indexes. The expression levels of mitochondrial dynamics and apoptosis-related genes were also determined. The results showed that Pb treatment significantly decreased the activities of mitochondrial complexes and ATPases, and increased oxidative stress, and mitochondrial dynamics and anti-apoptosis-related genes had a lower expression, whereas mitochondrial pro-apoptosis related genes presented higher expressions in the Pb group compared with control group (P < 0.05). However, the co-treatment of Se and Pb significantly alleviated those changes compared with the Pb group (P < 0.05). In conclusion, we speculated that Pb could increase the oxidative stress and promote the apoptosis via regulating mitochondrial dynamics and apoptosis-related genes, and Se exhibited antagonistic roles against the Pb-induced apoptosis in the kidney of chickens.

The protective effects of polysaccharide of Atractylodes macrocephala Koidz (PAMK) on the chicken spleen under heat stress via antagonizing apoptosis and restoring the immune function

Heat stress can cause immune organ dysfunction and apoptosis. Polysaccharide of Atractylodes macrocephala Koidz may have protective effects on immune organs. In this study, we established chicken models of Polysaccharide of Atractylodes macrocephala Koidz-heat stress interaction and detected the oxidative index, activities of mitochondrial complexes and ATPases as well as the ultrastructure in chicken spleens. Expression levels of cytokines, mitochondrial dynamics- and apoptosis-related genes were also measured. In the result, heat stress increased the expression of interleukin 1 and tumour necrosis factor-alpha and decreased that of interleukin 2 and interferon gamma. The activities of mitochondrial complexes and ATPases were decreased and oxidative stress was induced by heat stress. Besides, expressions of the mitochondrial dynamics- and anti-apoptosis-related genes were decreased and those of pro-apoptosis-related genes were increased by heat stress. HS induced pathological changes of mitochondria and triggered apoptosis in chicken spleens. However, these adverse effects triggered by HS were remarkably alleviated in Polysaccharide of Atractylodes macrocephala Koidz + heat stress group. This study confirmed the protective effects of Polysaccharide of Atractylodes macrocephala Koidz on the chicken spleen against the heat stress and revealed its mechanism, which is that Polysaccharide of Atractylodes macrocephala Koidz could relieve the heat stress-induced immune dysfunction of chicken spleens via reducing oxidative stress, enhancing the mitochondria function and inhibiting apoptosis.

The Interplay between Oncogenic Signaling Networks and Mitochondrial Dynamics

Mitochondria are dynamic organelles that alter their organization in response to a variety of cellular cues. Mitochondria are central in many biologic processes, such as cellular bioenergetics and apoptosis, and mitochondrial network morphology can contribute to those physiologic processes. Some of the biologic processes that are in part governed by mitochondria are also commonly deregulated in cancers. Furthermore, patient tumor samples from a variety of cancers have revealed that mitochondrial dynamics machinery may be deregulated in tumors. In this review, we will discuss how commonly mutated oncogenes and their downstream effector pathways regulate the mitochondrial dynamics machinery to promote changes in mitochondrial morphology as well as the physiologic consequences of altered mitochondrial morphology for tumorigenic growth.