Metabolic Rewiring by Oncogenic BRAF V600E Links Ketogenesis Pathway to BRAF-MEK1 Signaling.

Many human cancers share similar metabolic alterations, including the Warburg effect. However, it remains unclear whether oncogene-specific metabolic alterations are required for tumor development. Here we demonstrate a "synthetic lethal" interaction between oncogenic BRAF V600E and a ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA lyase (HMGCL). HMGCL expression is upregulated in BRAF V600E-expressing human primary melanoma and hairy cell leukemia cells. Suppression of HMGCL specifically attenuates proliferation and tumor growth potential of human melanoma cells expressing BRAF V600E. Mechanistically, active BRAF upregulates HMGCL through an octamer transcription factor Oct-1, leading to increased intracellular levels of HMGCL product, acetoacetate, which selectively enhances binding of BRAF V600E but not BRAF wild-type to MEK1 in V600E-positive cancer cells to promote activation of MEK-ERK signaling. These findings reveal a mutation-specific mechanism by which oncogenic BRAF V600E "rewires" metabolic and cell signaling networks and signals through the Oct-1-HMGCL-acetoacetate axis to selectively promote BRAF V600E-dependent tumor development.

Tyr phosphorylation of PDP1 toggles recruitment between ACAT1 and SIRT3 to regulate the pyruvate dehydrogenase complex.

Mitochondrial pyruvate dehydrogenase complex (PDC) is crucial for glucose homeostasis in mammalian cells. The current understanding of PDC regulation involves inhibitory serine phosphorylation of pyruvate dehydrogenase (PDH) by PDH kinase (PDK), whereas dephosphorylation of PDH by PDH phosphatase (PDP) activates PDC. Here, we report that lysine acetylation of PDHA1 and PDP1 is common in epidermal growth factor (EGF)-stimulated cells and diverse human cancer cells. K321 acetylation inhibits PDHA1 by recruiting PDK1, and K202 acetylation inhibits PDP1 by dissociating its substrate PDHA1, both of which are important in promoting glycolysis in cancer cells and consequent tumor growth. Moreover, we identified mitochondrial ACAT1 and SIRT3 as the upstream acetyltransferase and deacetylase, respectively, of PDHA1 and PDP1, while knockdown of ACAT1 attenuates tumor growth. Furthermore, Y381 phosphorylation of PDP1 dissociates SIRT3 and recruits ACAT1 to PDC. Together, hierarchical, distinct posttranslational modifications act in concert to control molecular composition of PDC and contribute to the Warburg effect.

Lysine acetylation activates 6-phosphogluconate dehydrogenase to promote tumor growth.

Although the oxidative pentose phosphate pathway is important for tumor growth, how 6-phosphogluconate dehydrogenase (6PGD) in this pathway is upregulated in human cancers is unknown. We found that 6PGD is commonly activated in EGF-stimulated cells and human cancer cells by lysine acetylation. Acetylation at K76 and K294 of 6PGD promotes NADP(+) binding to 6PGD and formation of active 6PGD dimers, respectively. Moreover, we identified DLAT and ACAT2 as upstream acetyltransferases of K76 and K294, respectively, and HDAC4 as the deacetylase of both sites. Expressing acetyl-deficient mutants of 6PGD in cancer cells significantly attenuated cell proliferation and tumor growth. This is due in part to reduced levels of 6PGD products ribulose-5-phosphate and NADPH, which led to reduced RNA and lipid biosynthesis as well as elevated ROS. Furthermore, 6PGD activity is upregulated with increased lysine acetylation in primary leukemia cells from human patients, providing mechanistic insights into 6PGD upregulation in cancer cells.

Prediction and Feature Importance Analysis for Severity of COVID-19 in South Korea Using Artificial Intelligence: Model Development and Validation.

BACKGROUND: The number of deaths from COVID-19 continues to surge worldwide. In particular, if a patient's condition is sufficiently severe to require invasive ventilation, it is more likely to lead to death than to recovery. OBJECTIVE: The goal of our study was to analyze the factors related to COVID-19 severity in patients and to develop an artificial intelligence (AI) model to predict the severity of COVID-19 at an early stage. METHODS: We developed an AI model that predicts severity based on data from 5601 COVID-19 patients from all national and regional hospitals across South Korea as of April 2020. The clinical severity of COVID-19 was divided into two categories: low and high severity. The condition of patients in the low-severity group corresponded to no limit of activity, oxygen support with nasal prong or facial mask, and noninvasive ventilation. The condition of patients in the high-severity group corresponded to invasive ventilation, multi-organ failure with extracorporeal membrane oxygenation required, and death. For the AI model input, we used 37 variables from the medical records, including basic patient information, a physical index, initial examination findings, clinical findings, comorbid diseases, and general blood test results at an early stage. Feature importance analysis was performed with AdaBoost, random forest, and eXtreme Gradient Boosting (XGBoost); the AI model for predicting COVID-19 severity among patients was developed with a 5-layer deep neural network (DNN) with the 20 most important features, which were selected based on ranked feature importance analysis of 37 features from the comprehensive data set. The selection procedure was performed using sensitivity, specificity, accuracy, balanced accuracy, and area under the curve (AUC). RESULTS: We found that age was the most important factor for predicting disease severity, followed by lymphocyte level, platelet count, and shortness of breath or dyspnea. Our proposed 5-layer DNN with the 20 most important features provided high sensitivity (90.2%), specificity (90.4%), accuracy (90.4%), balanced accuracy (90.3%), and AUC (0.96). CONCLUSIONS: Our proposed AI model with the selected features was able to predict the severity of COVID-19 accurately. We also made a web application so that anyone can access the model. We believe that sharing the AI model with the public will be helpful in validating and improving its performance.

Luteolin inhibits H2O2-induced cellular senescence via modulation of SIRT1 and p53.

Luteolin, a sort of flavonoid, has been reported to be involved in neuroprotective function via suppression of neuroinflammation. In this study, we investigated the protective effect of luteolin against oxidative stress-induced cellular senescence and its molecular mechanism using hydrogen peroxide (H2O2)-induced cellular senescence model in House Ear Institute-Organ of Corti 1 cells (HEI-OC1). Our results showed that luteolin attenuated senescent phenotypes including alterations of morphology, cell proliferation, senescence-associated ß-galactosidase expression, DNA damage, as well as related molecules expression such as p53 and p21 in the oxidant challenged model. Interestingly, we found that luteolin induces expression of sirtuin 1 in dose- and time-dependent manners and it has protective role against H2O2-induced cellular senescence by upregulation of sirtuin 1 (SIRT1). In contrast, the inhibitory effect of luteolin on cellular senescence under oxidative stress was abolished by silencing of SIRT1. This study indicates that luteolin effectively protects against oxidative stress-induced cellular senescence through p53 and SIRT1. These results suggest that luteolin possesses therapeutic potentials against age-related hearing loss that are induced by oxidative stress.

Myc-mediated transcriptional regulation of the mitochondrial chaperone TRAP1 controls primary and metastatic tumor growth.

The role of mitochondria in cancer continues to be debated, and whether exploitation of mitochondrial functions is a general hallmark of malignancy or a tumor- or context-specific response is still unknown. Using a variety of cancer cell lines and several technical approaches, including siRNA-mediated gene silencing, ChIP assays, global metabolomics and focused metabolite analyses, bioenergetics, and cell viability assays, we show that two oncogenic Myc proteins, c-Myc and N-Myc, transcriptionally control the expression of the mitochondrial chaperone TNFR-associated protein-1 (TRAP1) in cancer. In turn, this Myc-mediated regulation preserved the folding and function of mitochondrial oxidative phosphorylation (OXPHOS) complex II and IV subunits, dampened reactive oxygen species production, and enabled oxidative bioenergetics in tumor cells. Of note, we found that genetic or pharmacological targeting of this pathway shuts off tumor cell motility and invasion, kills Myc-expressing cells in a TRAP1-dependent manner, and suppresses primary and metastatic tumor growth in vivo We conclude that exploitation of mitochondrial functions is a general trait of tumorigenesis and that this reliance of cancer cells on mitochondrial OXPHOS pathways could offer an actionable therapeutic target in the clinic.

Lysyl oxidase-variant 2 (LOX-v2) colocalizes with promyelocytic leukemia-nuclear bodies in the nucleus.

Lysyl oxidase-variant 2 (LOX-v2) is a novel variant of LOX that functions as an amine oxidase for the formation of collagen and elastin fibrils in the extracellular matrix (ECM). LOX-v2 lacks the N-terminal prepropeptide region of LOX but contains the C-terminal domains required for amine oxidase activity. To study the cellular localization of LOX-v2, we generated a recombinant construct of LOX-v2 with an epitope tag at the C-terminus and then transfected the recombinant construct into HEK293 cells. Upon ectopic expression, LOX-v2 showed much higher expression in the nucleus than in the cytoplasm. In coimmunofluorescence staining with subnuclear structures, LOX-v2 colocalized with the promyelocytic leukemia-nuclear bodies (PML-NBs). Further, the ectopic expression of LOX-v2 increased global SUMOylation in the nucleus. PML-NBs have been implicated in various cellular activities, including transcriptional regulation, DNA repair, cell cycle control, anti-viral response, and apoptosis. Our findings strongly indicate that LOX-v2 may be subject to different cellular processing from what LOX undergoes, playing a distinct functional role in the PML-NBs, beyond the cross-linking of the structural proteins.

IDH2 reprograms mitochondrial dynamics in cancer through a HIF-1α-regulated pseudohypoxic state.

The role of mitochondria in cancer continues to be debated and paradoxically implicated in opposing functions in tumor growth and tumor suppression. To understand this dichotomy, we explored the function of mitochondrial isocitrate dehydrogenase (IDH)2, a tricarboxylic acid cycle enzyme mutated in subsets of acute leukemias and gliomas, in cancer. Silencing of IDH2 in prostate cancer cells impaired oxidative bioenergetics, elevated reactive oxygen species (ROS) production, and promoted exaggerated mitochondrial dynamics. This was associated with increased subcellular mitochondrial trafficking, turnover of membrane focal adhesion complexes, and enhanced tumor cell migration and invasion, without changes in cell cycle progression. Mechanistically, loss of IDH2 caused ROS-dependent stabilization of hypoxia-inducible factor-1α in normoxia, which was required for increased mitochondrial trafficking and tumor cell movements. Therefore, IDH2 is a dual regulator of cancer bioenergetics and tumor cell motility. This pathway may reprogram mitochondrial dynamics to differentially adjust energy production or promote tumor cell invasion in response to microenvironment conditions.-Wang, Y., Agarwal, E., Bertolini, I., Ghosh, J. C., Seo, J. H., Altieri, D. C. IDH2 reprograms mitochondrial dynamics in cancer through a HIF-1α-regulated pseudohypoxic state.

Latifolin Inhibits Oxidative Stress-Induced Senescence via Upregulation of SIRT1 in Human Dermal Fibroblasts.

Latifolin, a natural flavonoid found in Dalbergia odorifera T. Chen, has been reported to exhibit anti-inflammatory and anticarcinogenic activities in vitro. However, the anti-aging effects of latifolin are unknown. In this study, we selected a model in vitro system, hydrogen peroxide (H2O2)-induced senescence in human dermal fibroblasts (HDFs), to examine the protective effects of latifolin against senescence and the detailed molecular mechanisms involved. Latifolin reversed the senescence-like phenotypes of the oxidant-challenged model, including senescence-associated ß-galactosidase (SA-ß-gal) staining, cell proliferation, and the expression of senescence-related proteins, such as caveolin-1, ac-p53, p21Cip1/WAF1, p16Ink4α, pRb, and cyclinD1. We also found that latifolin induced the expression of silent information regulator 1 (SIRT1) in a concentration- and time-dependent manner, and the anti-senescence effect of latifolin was abrogated by SIRT1 inhibition. Latifolin also suppressed the activation of Akt and S6K1 and attenuated the increase in SA-ß-gal activity after H2O2 exposure. Our results indicate that latifolin exerts protective effects against senescence in HDFs and that induction of SIRT1 and inhibition of the mammalian target of rapamycin (mTOR) pathway are key mediators of its anti-aging effects.

An Artificial Intelligence Model to Predict the Mortality of COVID-19 Patients at Hospital Admission Time Using Routine Blood Samples: Development and Validation of an Ensemble Model.

BACKGROUND: COVID-19, which is accompanied by acute respiratory distress, multiple organ failure, and death, has spread worldwide much faster than previously thought. However, at present, it has limited treatments. OBJECTIVE: To overcome this issue, we developed an artificial intelligence (AI) model of COVID-19, named EDRnet (ensemble learning model based on deep neural network and random forest models), to predict in-hospital mortality using a routine blood sample at the time of hospital admission. METHODS: We selected 28 blood biomarkers and used the age and gender information of patients as model inputs. To improve the mortality prediction, we adopted an ensemble approach combining deep neural network and random forest models. We trained our model with a database of blood samples from 361 COVID-19 patients in Wuhan, China, and applied it to 106 COVID-19 patients in three Korean medical institutions. RESULTS: In the testing data sets, EDRnet provided high sensitivity (100%), specificity (91%), and accuracy (92%). To extend the number of patient data points, we developed a web application (BeatCOVID19) where anyone can access the model to predict mortality and can register his or her own blood laboratory results. CONCLUSIONS: Our new AI model, EDRnet, accurately predicts the mortality rate for COVID-19. It is publicly available and aims to help health care providers fight COVID-19 and improve patients' outcomes.

The Mitochondrial Unfoldase-Peptidase Complex ClpXP Controls Bioenergetics Stress and Metastasis.

Mitochondria must buffer the risk of proteotoxic stress to preserve bioenergetics, but the role of these mechanisms in disease is poorly understood. Using a proteomics screen, we now show that the mitochondrial unfoldase-peptidase complex ClpXP associates with the oncoprotein survivin and the respiratory chain Complex II subunit succinate dehydrogenase B (SDHB) in mitochondria of tumor cells. Knockdown of ClpXP subunits ClpP or ClpX induces the accumulation of misfolded SDHB, impairing oxidative phosphorylation and ATP production while activating "stress" signals of 5' adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and autophagy. Deregulated mitochondrial respiration induced by ClpXP targeting causes oxidative stress, which in turn reduces tumor cell proliferation, suppresses cell motility, and abolishes metastatic dissemination in vivo. ClpP is universally overexpressed in primary and metastatic human cancer, correlating with shortened patient survival. Therefore, tumors exploit ClpXP-directed proteostasis to maintain mitochondrial bioenergetics, buffer oxidative stress, and enable metastatic competence. This pathway may provide a "drugable" therapeutic target in cancer.

The prometastatic ribosomal S6 kinase 2-cAMP response element-binding protein (RSK2-CREB) signaling pathway up-regulates the actin-binding protein fascin-1 to promote tumor metastasis.

Metastasis is the leading cause of death in patients with breast, lung, and head and neck cancers. However, the molecular mechanisms underlying metastases in these cancers remain unclear. We found that the p90 ribosomal S6 kinase 2 (RSK2)-cAMP response element-binding protein (CREB) pathway is commonly activated in diverse metastatic human cancer cells, leading to up-regulation of a CREB transcription target Fascin-1. We also observed that the protein expression patterns of RSK2 and Fascin-1 correlate in primary human tumor tissue samples from head and neck squamous cell carcinoma patients. Moreover, knockdown of RSK2 disrupts filopodia formation and bundling in highly invasive cancer cells, leading to attenuated cancer cell invasion in vitro and tumor metastasis in vivo, whereas expression of Fascin-1 significantly rescues these phenotypes. Furthermore, targeting RSK2 with the small molecule RSK inhibitor FMK-MEA effectively attenuated the invasive and metastatic potential of cancer cells in vitro and in vivo, respectively. Taken together, our findings for the first time link RSK2-CREB signaling to filopodia formation and bundling through the up-regulation of Fascin-1, providing a proinvasive and prometastatic advantage to human cancers. Therefore, protein effectors of the RSK2-CREB-Fascin-1 pathway represent promising biomarkers and therapeutic targets in the clinical prognosis and treatment of metastatic human cancers.

Interplay between Solid Tumors and Tumor Microenvironment.

Over the past few decades, basic studies aimed at curing patients with cancer have been constantly evolving. A myriad of mechanistic studies on physiological changes and related factors in tumor growth and metastasis have been reported. Recently, several studies have been considerate to how tumors adapt to unfavorable environments, such as glucose deprivation, oxidative stress, hypoxic conditions, and immune responses. Tumors attempt to adapt to unfavorable environments with genetic or non-genetic changes, the alteration of metabolic signals, or the reconfiguration of their environment through migration to other organs. One of the distinct features in solid tumors is heterogeneity because their environments vary due to the characteristics of colony growth. For this reason, researchers are paying attention to the communication between growing tumors and neighboring environments, including stromal cells, immune cells, fibroblasts, and secreted molecules, such as proteins and RNAs. During cancer survival and progression, tumor cells undergo phenotype and molecular changes collectively referred to as cellular plasticity, which result from microenvironment signals, genetics and epigenetic alterations thereby contributing to tumor heterogeneity and therapy response. In this review, we herein discuss the adaptation process of tumors to adverse environments via communication with neighboring cells for overcoming unfavorable growth conditions. Understanding the physiology of these tumors and their communication with the tumor environment can help to develop promising tumor treatment strategies.

DRG2 Accelerates Senescence via Negative Regulation of SIRT1 in Human Diploid Fibroblasts.

Accumulating evidence suggests that developmentally regulated GTP-binding protein 2 (DRG2), an evolutionarily conserved GTP-binding protein, plays an important role in regulating cell growth, inflammation, and mitochondria dynamics. However, the effect of DRG2 in aging remains unclear. In this study, we found that endogenous DRG2 protein expression is upregulated in oxidative stress-induced premature senescence models and tissues of aged mice. Ectopic expression of DRG2 significantly promoted senescence-associated ß-galactosidase (SA-ß-gal) activity and inhibited cell growth, concomitant with increase in levels of acetyl (ac)-p53 (Lys382), ac-nuclear factor-kB (NF-κB) p65 (Lys310), p21 Waf1/Cip1 , and p16 Ink4a and a decrease in cyclin D1. In this process, reactive oxygen species (ROS) and phosphorylation of H2A histone family member X (H2A.X), forming γ-H2A.X, were enhanced. Mechanistically, ectopic expression of DRG2 downregulated Sirtuin-1 (SIRT1), resulting in augmented acetylation of p53 and NF-κB p65. Additionally, DRG2 knockdown significantly abolished oxidative stress-induced premature senescence. Our results provide a possible molecular mechanism for investigation of cellular senescence and aging regulated by DRG2.

Apigenin Alleviates Oxidative Stress-Induced Cellular Senescence via Modulation of the SIRT1-NAD[Formula: see text]-CD38 Axis.

Oxidative stress-induced cellular senescence is now regarded as an important driving mechanism in chronic lung diseases-particularly chronic obstructive pulmonary disease (COPD). 4[Formula: see text],5,7-trihydroxyflavone (Apigenin) is a natural flavonoid product abundantly present in fruits, vegetables, and Chinese medicinal herbs. It has been known that apigenin has anti-oxidant, anti-inflammatory and liver-protecting effects. The efficacy of apigenin for lung aging, however, has not been reported. In this study, we selected the hydrogen peroxide (H2O[Formula: see text]- or doxorubicin (DOXO)-induced senescence model in WI-38 human embryonic lung fibroblast cells to determine the potential anti-aging effects of apigenin in vitro and associated molecular mechanisms. We found that apigenin reduced senescence-associated [Formula: see text]-galactosidase (SA-[Formula: see text]-gal) activity and promoted cell growth, concomitant with a decrease in levels of Acetyl (ac)-p53, p21[Formula: see text], and p16[Formula: see text] and an increase in phospho (p)-Rb. Apigenin also increased the activation ratio of silent information regulator 1 (SIRT1), nicotinamide adenine dinucleotide (NAD[Formula: see text], and NAD[Formula: see text]/NADH and inhibited cluster of differentiation 38 (CD38) activity in a concentration-dependent manner. SIRT1 inhibition by SIRT1 siRNA abolished the anti-aging effect of apigenin. In addition, CD38 inhibition by CD38 siRNA or apigenin increased the SIRT1 level and reduced H2O2-induced senescence. Our findings suggest that apigenin is a promising phytochemical for reducing the impact of senescent cells in age-related lung diseases such as COPD.

Protective effects of Coenzyme Q10 against acute pancreatitis.

Acute pancreatitis (AP) refers to inflammation in the pancreas, which may lead to death in severe cases. Coenzyme Q10 (Q10), generally known to generate energy, plays an important role as an anti-oxidant and anti-inflammatory effector. Here, we showed the effect of Q10 on inflammatory response in murine AP model. For this study, we induced AP by injection of cerulein intraperitoneally or pancreatic duct ligation (PDL) in mice. The level of cytokines and digestive enzymes were measured in pancreas, and blood. All pancreatic tissues were excised for investigation such as histological changes, infiltration of immune cells. Administration of Q10 attenuated the severity of AP and its associated pulmonary complication as shown by reduction of acinar cell death, parenchymal edema, inflammatory cell infiltration and alveolar thickening in both cerulein-induced AP and PDL-induced AP. Moreover, reduction of the cytokines such as interleukin (IL)-1ß, IL-6 and tumor necrosis factor (TNF)-α were observed in pancreas and pancreatic acinar cells by Q10. Furthermore, Q10 reduced the infiltration of immune cells such as monocytes and neutrophils and augmentation of chemokines such as CC chemokine-2 (CCL2) and C-X-C chemokine-2 (CXCL2) in pancreas of AP mice. In addition, Q10 deactivates the phosphorylation of extracellular signal-regulated kinase (ERK) and c-jun NH2-terminal kinase (JNK) in pancreas. In conclusion, these observations suggest that Q10 could attenuate the pancreatic damage and its associated pulmonary complications via inhibition of inflammatory cytokines and inflammatory cell infiltration and that the deactivation of ERK and JNK by Q10 might contribute to the attenuation of AP.

The mitophagy effector FUNDC1 controls mitochondrial reprogramming and cellular plasticity in cancer cells.

Mitochondria are signaling hubs in eukaryotic cells. Here, we showed that the mitochondrial FUN14 domain-containing protein-1 (FUNDC1), an effector of Parkin-independent mitophagy, also participates in cellular plasticity by sustaining oxidative bioenergetics, buffering ROS production, and supporting cell proliferation. Targeting this pathway in cancer cells suppressed tumor growth but rendered transformed cells more motile and invasive in a manner dependent on ROS-mediated mitochondrial dynamics and mitochondrial repositioning to the cortical cytoskeleton. Global metabolomics and proteomics profiling identified a FUNDC1 interactome at the mitochondrial inner membrane, comprising the AAA+ protease, LonP1, and subunits of oxidative phosphorylation, complex V (ATP synthase). Independently of its previously identified role in mitophagy, FUNDC1 enabled LonP1 proteostasis, which in turn preserved complex V function and decreased ROS generation. Therefore, mitochondrial reprogramming by a FUNDC1-LonP1 axis controls tumor cell plasticity by switching between proliferative and invasive states in cancer.

Akt phosphorylation of mitochondrial Lonp1 protease enables oxidative metabolism and advanced tumor traits.

Tumor mitochondria have heightened protein folding quality control, but the regulators of this process and how they impact cancer traits are not completely understood. Here we show that the ATP-directed mitochondrial protease, LonP1 is upregulated by stress conditions, including hypoxia, in tumor, but not normal cells. In mitochondria, LonP1 is phosphorylated by Akt on Ser173 and Ser181, enhancing its protease activity. Interference with this pathway induces accumulation of misfolded subunits of electron transport chain complex II and complex V, resulting in impaired oxidative bioenergetics and heightened ROS production. Functionally, this suppresses mitochondrial trafficking to the cortical cytoskeleton, shuts off tumor cell migration and invasion, and inhibits primary and metastatic tumor growth, in vivo. These data identify LonP1 as a key effector of mitochondrial reprogramming in cancer and potential therapeutic target.

Mitochondrial fission factor is a novel Myc-dependent regulator of mitochondrial permeability in cancer.

BACKGROUND: Mitochondrial functions are exploited in cancer and provide a validated therapeutic target. However, how this process is regulated has remained mostly elusive and the identification of new pathways that control mitochondrial integrity in cancer is an urgent priority. METHODS: We studied clinically-annotated patient series of primary and metastatic prostate cancer, representative cases of multiple myeloma (MM) and publicly available genetic databases. Gene regulation studies involved chromatin immunoprecipitation, PCR amplification and Western blotting of conditional Myc-expressing cell lines. Transient or stable gene silencing was used to quantify mitochondrial functions in bioenergetics, outer membrane permeability, Ca2+ homeostasis, redox balance and cell death. Tumorigenicity was assessed by cell proliferation, colony formation and xenograft tumour growth. FINDINGS: We identified Mitochondrial Fission Factor (MFF) as a novel transcriptional target of oncogenic Myc overexpressed in primary and metastatic cancer, compared to normal tissues. Biochemically, MFF isoforms, MFF1 and MFF2 associate with the Voltage-Dependent Anion Channel-1 (VDAC1) at the mitochondrial outer membrane, in vivo. Disruption of this complex by MFF silencing induces general collapse of mitochondrial functions with increased outer membrane permeability, loss of inner membrane potential, Ca2+ unbalance, bioenergetics defects and activation of cell death pathways. In turn, this inhibits tumour cell proliferation, suppresses colony formation and reduces xenograft tumour growth in mice. INTERPRETATION: An MFF-VDAC1 complex is a novel regulator of mitochondrial integrity and actionable therapeutic target in cancer.

MFF Regulation of Mitochondrial Cell Death Is a Therapeutic Target in Cancer.

The regulators of mitochondrial cell death in cancer have remained elusive, hampering the development of new therapies. Here, we showed that protein isoforms of mitochondrial fission factor (MFF1 and MFF2), a molecule that controls mitochondrial size and shape, that is, mitochondrial dynamics, were overexpressed in patients with non-small cell lung cancer and formed homo- and heterodimeric complexes with the voltage-dependent anion channel-1 (VDAC1), a key regulator of mitochondrial outer membrane permeability. MFF inserted into the interior hole of the VDAC1 ring using Arg225, Arg236, and Gln241 as key contact sites. A cell-permeable MFF Ser223-Leu243 d-enantiomeric peptidomimetic disrupted the MFF-VDAC1 complex, acutely depolarized mitochondria, and triggered cell death in heterogeneous tumor types, including drug-resistant melanoma, but had no effect on normal cells. In preclinical models, treatment with the MFF peptidomimetic was well-tolerated and demonstrated anticancer activity in patient-derived xenografts, primary breast and lung adenocarcinoma 3D organoids, and glioblastoma neurospheres. These data identify the MFF-VDAC1 complex as a novel regulator of mitochondrial cell death and an actionable therapeutic target in cancer. SIGNIFICANCE: These findings describe mitochondrial fission regulation using a peptidomimetic agent that disturbs the MFF-VDAC complex and displays anticancer activity in multiple tumor models.See related commentary by Rao, p. 6074.