Cardiolipin and electron transport chain abnormalities in mouse brain tumor mitochondria: lipidomic evidence supporting the Warburg theory of cancer

The role of cardiolipin and cytochrome c in mitochondrial metabolism of cancer cells determined by Raman imaging: in vitro study on the brain glioblastoma U-87 MG cell line

In this paper, we present Raman imaging as a non-invasive approach for studying changes in mitochondrial metabolism caused by cardiolipin-cytochrome c interactions. We investigated the effect of mitochondrial dysregulation on cardiolipin (CL) and cytochrome c (Cyt c) interactions for a brain cancer cell line (U-87 MG). Mitochondrial metabolism was monitored by checking the intensities of the Raman bands at 750 cm-1, 1126 cm-1, 1310 cm-1, 1337 cm-1, 1444 cm-1 and 1584 cm-1. The presented results indicate that under pathological conditions, the content and redox status of Cyt c in mitochondria can be used as a Raman marker to characterize changes in cellular metabolism. This work provides evidence that cardiolipin-cytochrome c interactions are crucial for mitochondrial energy homeostasis by controlling the redox status of Cyt c in the electron transport chain, switching from disabling Cyt c reduction and enabling peroxidase activity. This paper provides experimental support for the hypothesis of how cardiolipin-cytochrome c interactions regulate electron transfer in the respiratory chain, apoptosis and mROS production in mitochondria.

Decreased pyruvate dehydrogenase activity in Tafazzin-deficient cells is caused by dysregulation of pyruvate dehydrogenase phosphatase 1 (PDP1)

Cardiolipin (CL), the signature lipid of the mitochondrial inner membrane, is critical for maintaining optimal mitochondrial function and bioenergetics. Disruption of CL metabolism, caused by mutations in the CL remodeling enzyme TAFAZZIN, results in the life-threatening disorder Barth syndrome (BTHS). While the clinical manifestations of BTHS, such as dilated cardiomyopathy and skeletal myopathy, point to defects in mitochondrial bioenergetics, the disorder is also characterized by broad metabolic dysregulation, including abnormal levels of metabolites associated with the tricarboxylic acid (TCA) cycle. Recent studies have identified the inhibition of pyruvate dehydrogenase (PDH), the gatekeeper enzyme for TCA cycle carbon influx, as a key deficiency in various BTHS model systems. However, the molecular mechanisms linking aberrant CL remodeling, particularly the primary, direct consequence of reduced tetralinoleoyl-CL (TLCL) levels, to PDH activity deficiency are not yet understood. In the current study, we found that remodeled TLCL promotes PDH function by directly binding to and enhancing the activity of PDH phosphatase 1 (PDP1). This is supported by our findings that TLCL uniquely activates PDH in a dose-dependent manner, TLCL binds to PDP1 in vitro, TLCL-mediated PDH activation is attenuated in the presence of phosphatase inhibitor, and PDP1 activity is decreased in Tafazzin-knockout (TAZ-KO) C2C12 myoblasts. Additionally, we observed decreased mitochondrial calcium levels in TAZ-KO cells and treating TAZ-KO cells with calcium lactate (CaLac) increases mitochondrial calcium and restores PDH activity and mitochondrial oxygen consumption rate. Based on our findings, we conclude that reduced mitochondrial calcium levels and decreased binding of PDP1 to TLCL contribute to decreased PDP1 activity in TAZ-KO cells.

Novel Antineoplastic Inducers of Mitochondrial Apoptosis in Human Cancer Cells

I propose a new strategy to suppress human cancer completely with two entirely new drug compounds exploiting cancer's Warburg effect characterized by a defective mitochondrial aerobic respiration, substituted by cytosolic aerobic fermentation/glycolysis of D-(+)-glucose into L-(+)-lactic acid. The two essentially new drugs, compound 1 [P(op)T(est)162] and compound 3 (PT167), represent new highly symmetric, four-bladed propeller-shaped polyammonium cations. The in vitro antineoplastic highly efficacious drug compound 3 represents a covalent combination of compound 1 and compound 2 (PT166). The intermediate drug compound 2 is an entirely new colchic(in)oid derivative synthesized from colchicine. Compound 2's structure was determined using X-ray crystallography. Compound 1 and compound 3 were active in vitro versus 60 human cancer cell lines of the National Cancer Institute (NCI) Developmental Therapeutics Program (DTP) 60-cancer cell testing. Compound 1 and compound 3 not only stop the growth of cancer cells to ±0% (cancerostatic effect) but completely kill nearly all 60 cancer cells to a level of almost -100% (tumoricidal effect). Compound 1 and compound 3 induce mitochondrial apoptosis (under cytochrome c release) in all cancer cells tested by (re)activating (in most cancers impaired) p53 function, which results in a decrease in cancer's dysregulated cyclin D1 and an induction of the cell cycle-halting cyclin-dependent kinase inhibitor p21Waf1/p21Cip1.

Lipid alterations play a role in the integration of PD-1/PD-L1 inhibitors and anlotinib for the treatment of advanced non-small-cell lung cancer

BACKGROUND

Studies have shown that integrating anlotinib with programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors enhances survival rates among progressive non-small-cell lung cancer (NSCLC) patients lacking driver mutations. However, not all individuals experience clinical benefits from this therapy. As a result, it is critical to investigate the factors that contribute to the inconsistent response of patients. Recent investigations have emphasized the importance of lipid metabolic reprogramming in the development and progression of NSCLC.

METHODS

The objective of this investigation was to examine the correlation between lipid variations and observed treatment outcomes in advanced NSCLC patients who were administered PD-1/PD-L1 inhibitors alongside anlotinib. A cohort composed of 30 individuals diagnosed with advanced NSCLC without any driver mutations was divided into three distinct groups based on the clinical response to the combination treatment, namely, a group exhibiting partial responses, a group manifesting progressive disease, and a group demonstrating stable disease. The lipid composition of patients in these groups was assessed both before and after treatment.

RESULTS

Significant differences in lipid composition among the three groups were observed. Further analysis revealed 19 differential lipids, including 2 phosphatidylglycerols and 17 phosphoinositides.

CONCLUSION

This preliminary study aimed to explore the specific impact of anlotinib in combination with PD-1/PD-L1 inhibitors on lipid metabolism in patients with advanced NSCLC. By investigating the effects of using both anlotinib and PD-1/PD-L1 inhibitors, this study enhances our understanding of lipid metabolism in lung cancer treatment. The findings from this research provide valuable insights into potential therapeutic approaches and the identification of new therapeutic biomarkers.

Anti-Cancer Properties of Resveratrol: A Focus on Its Impact on Mitochondrial Functions

Cancer is one of the most serious public health issues worldwide, demanding ongoing efforts to find novel therapeutic agents and approaches. Amid growing interest in the oncological applications of phytochemicals, particularly polyphenols, resveratrol-a naturally occurring polyphenolic stilbene derivative-has emerged as a candidate of interest. This review analyzes the pleiotropic anti-cancer effects of resveratrol, including its modulation of apoptotic pathways, cell cycle regulation, inflammation, angiogenesis, and metastasis, its interaction with cancer stem cells and the tumor microenvironment. The effects of resveratrol on mitochondrial functions, which are crucial to cancer development, are also discussed. Future research directions are identified, including the elucidation of specific molecular targets, to facilitate the clinical translation of resveratrol in cancer prevention and therapy.

Phenolic Compounds of Rhodiola rosea L. as the Potential Alternative Therapy in the Treatment of Chronic Diseases

The roots and rhizomes of Rhodiola rosea L. (Crassulaceae), which is widely growing in Northern Europe, North America, and Siberia, have been used since ancient times to alleviate stress, fatigue, and mental and physical disorders. Phenolic compounds: phenylpropanoids rosavin, rosarin, and rosin, tyrosol glucoside salidroside, and tyrosol, are responsible for the biological action of R. rosea, exerting antioxidant, immunomodulatory, anti-aging, anti-fatigue activities. R. rosea extract formulations are used as alternative remedies to enhance mental and cognitive functions and protect the central nervous system and heart during stress. Recent studies indicate that R. rosea may be used to treat diabetes, cancer, and a variety of cardiovascular and neurological disorders such as Alzheimer's and Parkinson's diseases. This paper reviews the beneficial effects of the extract of R. rosea, its key active components, and their possible use in the treatment of chronic diseases. R. rosea represents an excellent natural remedy to address situations involving decreased performance, such as fatigue and a sense of weakness, particularly in the context of chronic diseases. Given the significance of mitochondria in cellular energy metabolism and their vulnerability to reactive oxygen species, future research should prioritize investigating the potential effects of R. rosea main bioactive phenolic compounds on mitochondria, thus targeting cellular energy supply and countering oxidative stress-related effects.

Apoptosis and Autophagy, Different Modes of Cell Death: How to Utilize Them to Fight Diseases?

A careful balance between cell death and survival is of key importance when it comes to the maintenance of cellular homeostasis [...].

Croix CM, Mao G, Kapralov A, Bayir H, Kagan VE, Yang D. Visualizing Cardiolipin In Situ with HKCL-1M, a Highly Selective and Sensitive Fluorescent Probe

Reliable probing of cardiolipin (CL) content in dynamic cellular milieux presents significant challenges and great opportunities for understanding mitochondria-related diseases, including cancer, neurodegeneration, and diabetes mellitus. In intact respiring cells, selectivity and sensitivity for CL detection are technically demanding due to structural similarities among phospholipids and compartmental secludedness of the inner mitochondrial membrane. Here, we report a novel "turn-on" fluorescent probe HKCL-1M for detecting CL in situ. HKCL-1M displays outstanding sensitivity and selectivity toward CL through specific noncovalent interactions. In live-cell imaging, its hydrolyzed product HKCL-1 efficiently retained itself in intact cells independent of mitochondrial membrane potential (Δψm). The probe robustly co-localizes with mitochondria and outperforms 10-N-nonyl acridine orange (NAO) and Δψm-dependent dyes with superior photostability and negligible phototoxicity. Our work thus opens up new opportunities for studying mitochondrial biology through efficient and reliable visualization of CL in situ.

LPGAT1/LPLAT7 regulates acyl chain profiles at the sn-1 position of phospholipids in murine skeletal muscles

Skeletal muscle consists of both fast- and slow-twitch fibers. Phospholipids are important structural components of cellular membranes, and the diversity of their fatty acid composition affects membrane fluidity and permeability. Although some studies have shown that acyl chain species in phospholipids differ among various muscle fiber types, the mechanisms underlying these differences are unclear. To investigate this, we analyzed phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecules in the murine extensor digitorum longus (EDL; fast-twitch) and soleus (slow-twitch) muscles. In the EDL muscle, the vast majority (93.6%) of PC molecules was palmitate-containing PC (16:0-PC), whereas in the soleus muscle, in addition to 16:0-PC, 27.9% of PC molecules was stearate-containing PC (18:0-PC). Most palmitate and stearate were bound at the sn-1 position of 16:0- and 18:0-PC, respectively, and 18:0-PC was found in type I and IIa fibers. The amount of 18:0-PE was higher in the soleus than in the EDL muscle. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) increased the amount of 18:0-PC in the EDL. Lysophosphatidylglycerol acyltransferase 1 (LPGAT1) was highly expressed in the soleus compared with that in the EDL muscle and was upregulated by PGC-1α. LPGAT1 knockout decreased the incorporation of stearate into PC and PE in vitro and ex vivo and the amount of 18:0-PC and 18:0-PE in murine skeletal muscle with an increase in the level of 16:0-PC and 16:0-PE. Moreover, knocking out LPGAT1 decreased the amount of stearate-containing-phosphatidylserine (18:0-PS), suggesting that LPGAT1 regulated the acyl chain profiles of phospholipids, namely PC, PE, and PS, in the skeletal muscle.

Mass Spectrometry Imaging Reveals Abnormalities in Cardiolipin Composition and Distribution in Astrocytoma Tumor Tissues

Cardiolipin (CL) is a mitochondrial lipid with diverse roles in cellular respiration, signaling, and organelle membrane structure. CL content and composition are essential for proper mitochondrial function. Deranged mitochondrial energy production and signaling are key components of glial cell cancers and altered CL molecular species have been observed in mouse brain glial cell xenograft tumors. The objective of this study was to describe CL structural diversity trends in human astrocytoma tumors of varying grades and correlate these trends with histological regions within the heterogeneous astrocytoma microenvironment. To this aim, we applied desorption electrospray ionization coupled with high field asymmetric ion mobility mass spectrometry (DESI-FAIMS-MS) to map CL molecular species in human normal cortex (N = 29), lower-grade astrocytoma (N = 19), and glioblastoma (N = 28) tissues. With this platform, we detected 46 CL species and 12 monolysocardiolipin species from normal cortex samples. CL profiles detected from glioblastoma tissues lacked diversity and abundance of longer chain polyunsaturated fatty acid containing CL species when compared to CL detected from normal and lower-grade tumors. CL profiles correlated with trends in tumor viability and tumor infiltration. Structural characterization of the CL species by tandem MS experiments revealed differences in fatty acid and double bond isomer composition among astrocytoma tissues compared with normal cortex and glioblastoma tissues. The GlioVis platform was used to analyze astrocytoma gene expression data from the CGGA dataset. Decreased expression of several mitochondrial respiratory enzyme encoding-genes was observed for higher-grade versus lower-grade tumors, however no significant difference was observed for cardiolipin synthesis enzyme CRLS1.

Restoring mitochondrial cardiolipin homeostasis reduces cell death and promotes recovery after spinal cord injury

Alterations in phospholipids have long been associated with spinal cord injury (SCI). However, their specific roles and signaling cascades in mediating cell death and tissue repair remain unclear. Here we investigated whether alterations of cardiolipin (CL), a family of mitochondrion-specific phospholipids, play a crucial role in mitochondrial dysfunction and neuronal death following SCI. Lipidomic analysis was used to determine the profile of CL alteration in the adult rat spinal cord following a moderate contusive SCI at the 10th thoracic (T10) level. Cellular, molecular, and genetic assessments were performed to determine whether CL alterations mediate mitochondrial dysfunction and neuronal death after SCI, and, if so, whether reversing CL alteration leads to neuroprotection after SCI. Using lipidomic analysis, we uncovered CL alterations at an early stage of SCI. Over 50 distinct CL species were identified, of which 50% showed significantly decreased abundance after SCI. The decreased CL species contained mainly polyunsaturated fatty acids that are highly susceptible to peroxidation. In parallel, 4-HNE, a lipid peroxidation marker, significantly increased after SCI. We found that mitochondrial oxidative stress not only induced CL oxidation, but also resulted in CL loss by activating cPLA₂ to hydrolyze CL. CL alterations induced mitochondrial dysfunction and neuronal death. Remarkably, pharmacologic inhibition of CL alterations with XJB-5-131, a novel mitochondria-targeted electron and reactive oxygen species scavenger, reduced cell death, tissue damage and ameliorated motor deficits after SCI in adult rats. These findings suggest that CL alteration could be a novel mechanism that mediates injury-induced neuronal death, and a potential therapeutic target for ameliorating secondary SCI.

Barth Syndrome: Psychosocial Impact and Quality of Life Assessment

BACKGROUND

Barth syndrome (BTHS) is a rare X-linked genetic disease that affects multiple systems and leads to complex clinical manifestations. Although a considerable amount of research has focused on the physical aspects of the disease, less has focused on the psychosocial impact and quality of life (QoL) in BTHS.

METHODS

The current study investigated caregiver- (n = 10) and self-reported (n = 16) psychological well-being and QoL in a cohort of BTHS-affected patients and families. Participants completed the depression and anxiety components of the Patient-Reported Outcomes Information System (PROMIS) Short Form 8A and Health-related quality of life (HRQoL) surveys at enrollment and again during a follow-up period ranging from 6 to 36 months after baseline.

RESULTS

Quality of life changed significantly over time and the various domains with some improvement and some decline. Among the available caregiver-patient dyad data, there was a trend toward discordance between caregiver and self-reported outcomes. Most notably, patients reported improvement in HRQoL, while caregivers reported declines. This suggests that there may be differences in perceived quality of life between the patients and parents, though our study is limited by small sample size.

CONCLUSION

Our study provides valuable insights into the impacts of psychosocial and mental health aspects of BTHS. Implications of these findings include incorporating longitudinal assessment of QoL and screening for psychological symptoms in BTHS care to identify interventions that may drastically impact health status and the course of the disease.

ER-mitochondria contact sites; a multifaceted factory for Ca2+ signaling and lipid transport

Membrane contact sites (MCS) between organelles of eukaryotic cells provide structural integrity and promote organelle homeostasis by facilitating intracellular signaling, exchange of ions, metabolites and lipids and membrane dynamics. Cataloguing MCS revolutionized our understanding of the structural organization of a eukaryotic cell, but the functional role of MSCs and their role in complex diseases, such as cancer, are only gradually emerging. In particular, the endoplasmic reticulum (ER)-mitochondria contacts (EMCS) are key effectors of non-vesicular lipid trafficking, thereby regulating the lipid composition of cellular membranes and organelles, their physiological functions and lipid-mediated signaling pathways both in physiological and diseased conditions. In this short review, we discuss key aspects of the functional complexity of EMCS in mammalian cells, with particular emphasis on their role as central hubs for lipid transport between these organelles and how perturbations of these pathways may favor key traits of cancer cells.

In Search of the Holy Grail: Toward a Unified Hypothesis on Mitochondrial Dysfunction in Age-Related Diseases

Cardiolipin (CL) is a mitochondrial signature phospholipid that plays a pivotal role in mitochondrial dynamics, membrane structure, oxidative phosphorylation, mtDNA bioenergetics, and mitophagy. The depletion or abnormal acyl composition of CL causes mitochondrial dysfunction, which is implicated in the pathogenesis of aging and age-related disorders. However, the molecular mechanisms by which mitochondrial dysfunction causes age-related diseases remain poorly understood. Recent development in the field has identified acyl-CoA:lysocardiolipin acyltransferase 1 (ALCAT1), an acyltransferase upregulated by oxidative stress, as a key enzyme that promotes mitochondrial dysfunction in age-related diseases. ALCAT1 catalyzes CL remodeling with very-long-chain polyunsaturated fatty acids, such as docosahexaenoic acid (DHA). Enrichment of DHA renders CL highly sensitive to oxidative damage by reactive oxygen species (ROS). Oxidized CL becomes a new source of ROS in the form of lipid peroxides, leading to a vicious cycle of oxidative stress, CL depletion, and mitochondrial dysfunction. Consequently, ablation or the pharmacological inhibition of ALCAT1 have been shown to mitigate obesity, type 2 diabetes, heart failure, cardiomyopathy, fatty liver diseases, neurodegenerative diseases, and cancer. The findings suggest that age-related disorders are one disease (aging) manifested by different mitochondrion-sensitive tissues, and therefore should be treated as one disease. This review will discuss a unified hypothesis on CL remodeling by ALCAT1 as the common denominator of mitochondrial dysfunction, linking mitochondrial dysfunction to the development of age-related diseases.

Probing the Link between Pancratistatin and Mitochondrial Apoptosis through Changes in the Membrane Dynamics on the Nanoscale

Pancratistatin (PST) is a natural antiviral alkaloid that has demonstrated specificity toward cancerous cells and explicitly targets the mitochondria. PST initiates apoptosis while leaving healthy, noncancerous cells unscathed. However, the manner by which PST induces apoptosis remains elusive and impedes the advancement of PST as a natural anticancer therapeutic agent. Herein, we use neutron spin-echo (NSE) spectroscopy, molecular dynamics (MD) simulations, and supporting small angle scattering techniques to study PST's effect on membrane dynamics using biologically representative model membranes. Our data suggests that PST stiffens the inner mitochondrial membrane (IMM) by being preferentially associated with cardiolipin, which would lead to the relocation and release of cytochrome c. Second, PST has an ordering effect on the lipids and disrupts their distribution within the IMM, which would interfere with the maintenance and functionality of the active forms of proteins in the electron transport chain. These previously unreported findings implicate PST's effect on mitochondrial apoptosis.

Mitochondrial Lipids: From Membrane Organization to Apoptotic Facilitation

Mitochondria are the most complex intracellular organelles, their function combining energy production for survival and apoptosis facilitation for death. Such a multivariate physiology is structurally and functionally reflected upon their membrane configuration and lipid composition. Mitochondrial double membrane lipids, with cardiolipin as the protagonist, show an impressive level of complexity that is mandatory for maintenance of mitochondrial health and protection from apoptosis. Given that lipidomics is an emerging field in cancer research and that mitochondria are the organelles with the most important role in malignant maintenance knowledge of the mitochondrial membrane, lipid physiology in health is mandatory. In this review, we will thus describe the delicate nature of the healthy mitochondrial double membrane and its role in apoptosis. Emphasis will be given on mitochondrial membrane lipids and the changes that they undergo during apoptosis induction and progression.

Glucose fluxes in glycolytic and oxidative pathways detected in vivo by deuterium magnetic resonance spectroscopy reflect proliferation in mouse glioblastoma

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We performed dynamic glucose enhanced (DGE) ²H-MRS in mouse GBM tumors.

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Marchenko-Pastur PCA denoising of ²H-MRS spectra improved kinetic quantification.

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Metabolic kinetics revealed differential glucose pathway fluxes in non-necrotic tumors.

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Modulation of glucose metabolism reflected tumor heterogeneity (proliferation).

Objectives

Glioblastoma multiforme (GBM), the most aggressive glial brain tumors, can metabolize glucose through glycolysis and mitochondrial oxidation pathways. While specific dependencies on those pathways are increasingly associated with treatment response, detecting such GBM subtypes in vivo remains elusive. Here, we develop a dynamic glucose-enhanced deuterium spectroscopy (DGE ²H-MRS) approach for differentially assessing glucose turnover rates through glycolysis and mitochondrial oxidation in mouse GBM and explore their association with histologic features of the tumor and its microenvironment.

Materials and methods

GL261 and CT2A glioma allografts were induced in immunocompetent mice and scanned in vivo at 9.4 Tesla, harnessing DGE ²H-MRS with volume selection and Marchenko-Pastur PCA (MP-PCA) denoising to achieve high temporal resolution. Each tumor was also classified by histopathologic analysis and assessed for cell proliferation (Ki67 immunostaining), while the respective cell lines underwent in situ extracellular flux analysis to assess mitochondrial function.

Results

MP-PCA denoising of in vivo DGE ²H-MRS data significantly improved the time-course detection (~2-fold increased Signal-to-Noise Ratio) and fitting precision (−19 ± 1 % Cramér-Rao Lower Bounds) of ²H-labelled glucose, and glucose-derived glutamate-glutamine (Glx) and lactate pools in GL261 and CT2A orthotopic tumors. Kinetic modeling further indicated inter-tumor heterogeneity of glucose consumption rate for glycolysis and oxidation during a defined epoch of active proliferation in both cohorts (19 ± 1 days post-induction), with consistent volumes (38.3 ± 3.4 mm³) and perfusion properties prior to marked necrosis. Histopathologic analysis of these tumors revealed clear differences in tumor heterogeneity between the two GBM models, aligned with metabolic differences of the respective cell lines monitored in situ. Importantly, glucose oxidation (i.e. Glx synthesis and elimination rates: 0.40 ± 0.08 and 0.12 ± 0.03 mM min⁻¹, respectively) strongly correlated with cell proliferation across the pooled cohorts (R = 0.82, p = 0.001; and R = 0.80, p = 0.002, respectively), regardless of tumor morphologic features or in situ metabolic characteristics of each GBM model.

Conclusions

Our fast DGE ²H-MRS enables the quantification of glucose consumption rates through glycolysis and mitochondrial oxidation in mouse GBM, which is relevant for assessing their modulation in vivo according to tumor microenvironment features such as cell proliferation. This novel application augurs well for non-invasive metabolic characterization of glioma or other cancers with mitochondrial oxidation dependencies.

Phosphatidylserine Synthase PTDSS1 Shapes the Tumor Lipidome to Maintain Tumor-Promoting Inflammation

Significance:

This study shows that inhibiting the production of ether-phosphatidylserine by targeting phosphatidylserine synthase PTDSS1 limits tumor-associated macrophage expansion and breast tumor growth.

Enhanced Characterization of Cardiolipins via Hybrid 193 nm Ultraviolet Photodissociation Mass Spectrometry

Cardiolipins (CLs) constitute a structurally complex class of glycerophospholipids with a unique tetraacylated structure accompanied by distinctive functional roles. Aberrations in the composition of this lipid class have been associated with disease states, spurring interest in the development of new approaches to differentiate the structures of diverse CLs in complex mixtures. The structural characterization of these complex lipids using conventional methods, however, suffers from limited resolution and frequently proves unable to discern subtle yet biologically significant features such as unsaturation sites or acyl chain position assignments. Here, we describe the synergistic use of chemical derivatization and hybrid dissociation techniques to characterize CL from complex biological mixtures with both double bond and sn positional isomer resolution in a shotgun mass spectrometry strategy. Utilizing (trimethylsilyl)diazomethane (TMSD), CL phosphate groups were methylated to promote positive-mode ionization by the production of metal-cationized lipids, enabling structural interrogation via hybrid higher-energy collisional activation/ultraviolet photodissociation (HCD/UVPD). This combination of TMSD derivatization and HCD/UVPD fragmentation results in diagnostic product ions that permit distinction and relative quantitation of sn-stereoisomers and the localization of double bonds. Applying this strategy to a total lipid extract from a thyroid carcinoma revealed a previously unreported 18:2/18:1 motif, elucidating a structural feature unique to the lipid class.

Targeting the Interplay between Cancer Metabolic Reprogramming and Cell Death Pathways as a Viable Therapeutic Path

In cancer cells, metabolic adaptations are often observed in terms of nutrient absorption, biosynthesis of macromolecules, and production of energy necessary to meet the needs of the tumor cell such as uncontrolled proliferation, dissemination, and acquisition of resistance to death processes induced by both unfavorable environmental conditions and therapeutic drugs. Many oncogenes and tumor suppressor genes have a significant effect on cellular metabolism, as there is a close relationship between the pathways activated by these genes and the various metabolic options. The metabolic adaptations observed in cancer cells not only promote their proliferation and invasion, but also their survival by inducing intrinsic and acquired resistance to various anticancer agents and to various forms of cell death, such as apoptosis, necroptosis, autophagy, and ferroptosis. In this review we analyze the main metabolic differences between cancer and non-cancer cells and how these can affect the various cell death pathways, effectively determining the susceptibility of cancer cells to therapy-induced death. Targeting the metabolic peculiarities of cancer could represent in the near future an innovative therapeutic strategy for the treatment of those tumors whose metabolic characteristics are known.

Metabolic therapy and bioenergetic analysis: The missing piece of the puzzle

BACKGROUND

Aberrant metabolism is recognized as a hallmark of cancer, a pillar necessary for cellular proliferation. Regarding bioenergetics (ATP generation), most cancers display a preference not only toward aerobic glycolysis ("Warburg effect") and glutaminolysis (mitochondrial substrate level-phosphorylation) but also toward other metabolites such as lactate, pyruvate, and fat-derived sources. These secondary metabolites can assist in proliferation but cannot fully cover ATP demands.

SCOPE OF REVIEW

The concept of a static metabolic profile is challenged by instances of heterogeneity and flexibility to meet fuel/anaplerotic demands. Although metabolic therapies are a promising tool to improve therapeutic outcomes, either via pharmacological targets or press-pulse interventions, metabolic plasticity is rarely considered. Lack of bioenergetic analysis in vitro and patient-derived models is hindering translational potential. Here, we review the bioenergetics of cancer and propose a simple analysis of major metabolic pathways, encompassing both affordable and advanced techniques. A comprehensive compendium of Seahorse XF bioenergetic measurements is presented for the first time.

MAJOR CONCLUSIONS

Standardization of principal readouts might help researchers to collect a complete metabolic picture of cancer using the most appropriate methods depending on the sample of interest.

Discovering Essential Multiple Gene Effects Through Large Scale Optimization: An Application to Human Cancer Metabolism

Computational modelling of metabolic processes has proven to be a useful approach to formulate our knowledge and improve our understanding of core biochemical systems that are crucial to maintaining cellular functions. Towards understanding the broader role of metabolism on cellular decision-making in health and disease conditions, it is important to integrate the study of metabolism with other core regulatory systems and omics within the cell, including gene expression patterns. After quantitatively integrating gene expression profiles with a genome-scale reconstruction of human metabolism, we propose a set of combinatorial methods to reverse engineer gene expression profiles and to find pairs and higher-order combinations of genetic modifications that simultaneously optimize multi-objective cellular goals. This enables us to suggest classes of transcriptomic profiles that are most suitable to achieve given metabolic phenotypes. We demonstrate how our techniques are able to compute beneficial, neutral or "toxic" combinations of gene expression levels. We test our methods on nine tissue-specific cancer models, comparing our outcomes with the corresponding normal cells, identifying genes as targets for potential therapies. Our methods open the way to a broad class of applications that require an understanding of the interplay among genotype, metabolism, and cellular behaviour, at scale.

Can the Mitochondrial Metabolic Theory Explain Better the Origin and Management of Cancer than Can the Somatic Mutation Theory?

A theory that can best explain the facts of a phenomenon is more likely to advance knowledge than a theory that is less able to explain the facts. Cancer is generally considered a genetic disease based on the somatic mutation theory (SMT) where mutations in proto-oncogenes and tumor suppressor genes cause dysregulated cell growth. Evidence is reviewed showing that the mitochondrial metabolic theory (MMT) can better account for the hallmarks of cancer than can the SMT. Proliferating cancer cells cannot survive or grow without carbons and nitrogen for the synthesis of metabolites and ATP (Adenosine Triphosphate). Glucose carbons are essential for metabolite synthesis through the glycolysis and pentose phosphate pathways while glutamine nitrogen and carbons are essential for the synthesis of nitrogen-containing metabolites and ATP through the glutaminolysis pathway. Glutamine-dependent mitochondrial substrate level phosphorylation becomes essential for ATP synthesis in cancer cells that over-express the glycolytic pyruvate kinase M2 isoform (PKM2), that have deficient OxPhos, and that can grow in either hypoxia (0.1% oxygen) or in cyanide. The simultaneous targeting of glucose and glutamine, while elevating levels of non-fermentable ketone bodies, offers a simple and parsimonious therapeutic strategy for managing most cancers.

Lipidomic profiling of clinical prostate cancer reveals targetable alterations in membrane lipid composition

Dysregulated lipid metabolism is a prominent feature of prostate cancer that is driven by androgen receptor (AR) signaling. Here we used quantitative mass spectrometry to define the "lipidome" in prostate tumors with matched benign tissues (n=21), independent unmatched tissues (n=47), and primary prostate explants cultured with the clinical AR antagonist enzalutamide (n=43). Significant differences in lipid composition were detected and spatially visualized in tumors compared to matched benign samples. Notably, tumors featured higher proportions of monounsaturated lipids overall and elongated fatty acid chains in phosphatidylinositol and phosphatidylserine lipids. Significant associations between lipid profile and malignancy were validated in unmatched samples, and phospholipid composition was characteristically altered in patient tissues that responded to AR inhibition. Importantly, targeting tumor-related lipid features via inhibition of acetyl-CoA carboxylase 1 significantly reduced cellular proliferation and induced apoptosis in tissue explants. This first characterization of the prostate cancer lipidome in clinical tissues reveals enhanced fatty acid synthesis, elongation, and desaturation as tumor-defining features, with potential for therapeutic targeting.

High-resolution mass spectrometric analysis of cardiolipin profiles in Barth syndrome

Barth syndrome is an X-linked recessive disorder caused by pathogenic variants in TAZ, which leads to a reduction in cardiolipin with a concomitant elevation of monolysocardiolipins. There is a paucity of studies characterizing changes in individual species of monolysocardiolipins, dilysocardiolipins and cardiolipin in Barth syndrome using high resolution untargeted lipidomics that can accurately annotate and quantify diverse lipids. We confirmed the structural diversity monolysocardiolipins, dilysocardiolipins and cardiolipin and identified individual species that showed previously unreported alterations in BTHS. Development of mass spectrometry-based targeted assays for these lipid biomarkers should provide an important tool for clinical diagnosis of Barth syndrome.

Ketogenic Metabolic Therapy, Without Chemo or Radiation, for the Long-Term Management of IDH1-Mutant Glioblastoma: An 80-Month Follow-Up Case Report

Background: Successful treatment of glioblastoma (GBM) remains futile despite decades of intense research. GBM is similar to most other malignant cancers in requiring glucose and glutamine for growth, regardless of histological or genetic heterogeneity. Ketogenic metabolic therapy (KMT) is a non-toxic nutritional intervention for cancer management. We report the case of a 32-year-old man who presented in 2014 with seizures and a right frontal lobe tumor on MRI. The tumor cells were immunoreactive with antibodies to the IDH1 (R132H) mutation, P53 (patchy), MIB-1 index (4–6%), and absent ATRX protein expression. DNA analysis showed no evidence of methylation of the MGMT gene promoter. The presence of prominent microvascular proliferation and areas of necrosis were consistent with an IDH-mutant glioblastoma (WHO Grade 4).

Methods: The patient refused standard of care (SOC) and steroid medication after initial diagnosis, but was knowledgeable and self-motivated enough to consume a low-carbohydrate ketogenic diet consisting mostly of saturated fats, minimal vegetables, and a variety of meats. The patient used the glucose ketone index calculator to maintain his Glucose Ketone Index (GKI) near 2.0 without body weight loss.

Results: The tumor continued to grow slowly without expected vasogenic edema until 2017, when the patient opted for surgical debulking. The enhancing area, centered in the inferior frontal gyrus, was surgically excised. The pathology specimen confirmed IDH1-mutant GBM. Following surgery, the patient continued with a self-administered ketogenic diet to maintain low GKI values, indicative of therapeutic ketosis. At the time of this report (May 2021), the patient remains alive with a good quality of life, except for occasional seizures. MRI continues to show slow interval progression of the tumor.

Conclusion: This is the first report of confirmed IDH1-mutant GBM treated with KMT and surgical debulking without chemo- or radiotherapy. The long-term survival of this patient, now at 80 months, could be due in part to a therapeutic metabolic synergy between KMT and the IDH1 mutation that simultaneously target the glycolysis and glutaminolysis pathways that are essential for GBM growth. Further studies are needed to determine if this non-toxic therapeutic strategy could be effective in providing long-term management for other GBM patients with or without IDH mutations.

Ketogenic diet treatment in diffuse intrinsic pontine glioma in children: Retrospective analysis of feasibility, safety, and survival data

Background

Diffuse intrinsic pontine glioma (DIPG) is one of the most devastating diseases among children with cancer, thus novel strategies are urgently needed.

Aims

We retrospectively evaluated DIPG patients exposed to the carbohydrate restricted ketogenic diet (KD) with regard of feasibility, safety, and overall survival (OS).

Methods and results

Searches of MEDLINE and Embase identified five hits meeting the search criteria (diagnosis of DIPG and exposure to KD). One additional case was identified by contact with experts. Individual patient data were extracted from publications or obtained from investigators. The inclusion criteria for analysis of the data were defined as DIPG patients who were exposed to the KD for ≥3 months. Feasibility, as described in the literature, was the number of patients able to follow the KD for 3 months out of all DIPG patients identified. OS was estimated by the Kaplan‐Meier method.

Five DIPG patients (males, n = 3; median age 4.4 years; range, 2.5‐15 years) meeting the inclusion criteria were identified. Analysis of the available data suggested that the KD is generally relatively well tolerated. Only mild gastro‐intestinal complaints, one borderline hypoglycemia (2.4 mmol/L) and one hyperketosis (max 7.2 mmol/L) were observed. Five out of six DIPG patients identified adhered for ≥3 months (median KD duration, 6.5 months; range, 0.25‐2 years) to the diet. The median OS was 18.7 months.

Conclusion

Our study provides evidence that it may be feasible for pediatric DIPG patients to adhere for at least 3 months to KD. In particular cases, diet modifications were done. The clinical outcome and OS appear not to be impacted in a negative way. KD might be proposed as adjuvant therapy when large prospective studies have shown feasibility and safety. Future studies might ideally assess the impact of KD on clinical outcome, quality of life, and efficacy.

Antioxidant Synergy of Mitochondrial Phospholipase PNPLA8/iPLA2γ with Fatty Acid-Conducting SLC25 Gene Family Transporters

Patatin-like phospholipase domain-containing protein PNPLA8, also termed Ca²⁺-independent phospholipase A2γ (iPLA2γ), is addressed to the mitochondrial matrix (or peroxisomes), where it may manifest its unique activity to cleave phospholipid side-chains from both sn-1 and sn-2 positions, consequently releasing either saturated or unsaturated fatty acids (FAs), including oxidized FAs. Moreover, iPLA2γ is directly stimulated by H₂O₂ and, hence, is activated by redox signaling or oxidative stress. This redox activation permits the antioxidant synergy with mitochondrial uncoupling proteins (UCPs) or other SLC25 mitochondrial carrier family members by FA-mediated protonophoretic activity, termed mild uncoupling, that leads to diminishing of mitochondrial superoxide formation. This mechanism allows for the maintenance of the steady-state redox status of the cell. Besides the antioxidant role, we review the relations of iPLA2γ to lipid peroxidation since iPLA2γ is alternatively activated by cardiolipin hydroperoxides and hypothetically by structural alterations of lipid bilayer due to lipid peroxidation. Other iPLA2γ roles include the remodeling of mitochondrial (or peroxisomal) membranes and the generation of specific lipid second messengers. Thus, for example, during FA β-oxidation in pancreatic β-cells, H₂O₂-activated iPLA2γ supplies the GPR40 metabotropic FA receptor to amplify FA-stimulated insulin secretion. Cytoprotective roles of iPLA2γ in the heart and brain are also discussed.

Phospholipid Acyl Chain Diversity Controls the Tissue-Specific Assembly of Mitochondrial Cardiolipins

Cardiolipin (CL) is a phospholipid specific for mitochondrial membranes and crucial for many core tasks of this organelle. Its acyl chain configurations are tissue specific, functionally important, and generated via post-biosynthetic remodeling. However, this process lacks the necessary specificity to explain CL diversity, which is especially evident for highly specific CL compositions in mammalian tissues. To investigate the so far elusive regulatory origin of CL homeostasis in mice, we combine lipidomics, integrative transcriptomics, and data-driven machine learning. We demonstrate that not transcriptional regulation, but cellular phospholipid compositions are closely linked to the tissue specificity of CL patterns allowing artificial neural networks to precisely predict cross-tissue CL compositions in a consistent mechanistic specificity rationale. This is especially relevant for the interpretation of disease-related perturbations of CL homeostasis, by allowing differentiation between specific aberrations in CL metabolism and changes caused by global alterations in cellular (phospho-)lipid metabolism.

Deciphering the dual role and prognostic potential of PINK1 across cancer types

Metabolic rewiring and deregulation of the cell cycle are hallmarks shared by many cancers. Concerted mutations in key tumor suppressor genes, such as PTEN, and oncogenes predispose cancer cells for marked utilization of resources to fuel accelerated cell proliferation and chemotherapeutic resistance. Mounting research has demonstrated that PTEN-induced putative kinase 1 (PINK1) acts as a pivotal regulator of mitochondrial homeostasis in several cancer types, a function that also extends to the regulation of tumor cell proliferative capacity. In addition, involvement of PINK1 in modulating inflammatory responses has been highlighted by recent studies, further expounding PINK1's multifunctional nature. This review discusses the oncogenic roles of PINK1 in multiple tumor cell types, with an emphasis on maintenance of mitochondrial homeostasis, while also evaluating literature suggesting a dual oncolytic mechanism based on PINK1's modulation of the Warburg effect. From a clinical standpoint, its expression may also dictate the response to genotoxic stressors commonly used to treat multiple malignancies. By detailing the evidence suggesting that PINK1 possesses distinct prognostic value in the clinical setting and reviewing the duality of PINK1 function in a context-dependent manner, we present avenues for future studies of this dynamic protein.

Phospholipid ebb and flow makes mitochondria go

Mitochondria, so much more than just being energy factories, also have the capacity to synthesize macromolecules including phospholipids, particularly cardiolipin (CL) and phosphatidylethanolamine (PE). Phospholipids are vital constituents of mitochondrial membranes, impacting the plethora of functions performed by this organelle. Hence, the orchestrated movement of phospholipids to and from the mitochondrion is essential for cellular integrity. In this review, we capture recent advances in the field of mitochondrial phospholipid biosynthesis and trafficking, highlighting the significance of interorganellar communication, intramitochondrial contact sites, and lipid transfer proteins in maintaining membrane homeostasis. We then discuss the physiological functions of CL and PE, specifically how they associate with protein complexes in mitochondrial membranes to support bioenergetics and maintain mitochondrial architecture.

Targeting Mitochondria by SS-31 Ameliorates the Whole Body Energy Status in Cancer- and Chemotherapy-Induced Cachexia

Simple Summary

Cancer cachexia is a debilitating syndrome, caused by both tumor growth and chemotherapy. The skeletal muscle is one of the main tissues affected during cachexia, presenting with altered metabolism and function, leading to progressive tissue wasting. In the current study we aimed at counteracting cachexia by pharmacologically improving metabolic function with the mitochondria-targeted compound SS-31. Experimental cancer cachexia was obtained using C26-bearing mice either receiving chemotherapy (oxaliplatin plus 5-fluorouracil) or not. SS-31 proved effective in rescuing some of the metabolic impairments imposed by both tumor and chemotherapy in the skeletal muscle and the liver, improving systemic energy control. Unfortunately, such effects were no longer present at late disease stages when refractory cachexia ensued. Overall, we provide evidence of potential new treatments targeting mitochondrial function in order to counteract or delay cancer cachexia.

Abstract

Objective: Cachexia is a complex metabolic syndrome frequently occurring in cancer patients and exacerbated by chemotherapy. In skeletal muscle of cancer hosts, reduced oxidative capacity and low intracellular ATP resulting from abnormal mitochondrial function were described. Methods: The present study aimed at evaluating the ability of the mitochondria-targeted compound SS-31 to counteract muscle wasting and altered metabolism in C26-bearing (C26) mice either receiving chemotherapy (OXFU: oxaliplatin plus 5-fluorouracil) or not. Results: Mitochondrial dysfunction in C26-bearing (C26) mice associated with alterations of cardiolipin fatty acid chains. Selectively targeting cardiolipin with SS-31 partially counteracted body wasting and prevented the reduction of glycolytic myofiber area. SS-31 prompted muscle mitochondrial succinate dehydrogenase (SDH) activity and rescued intracellular ATP levels, although it was unable to counteract mitochondrial protein loss. Progressively increased dosing of SS-31 to C26 OXFU mice showed transient (21 days) beneficial effects on body and muscle weight loss before the onset of a refractory end-stage condition (28 days). At day 21, SS-31 prevented mitochondrial loss and abnormal autophagy/mitophagy. Skeletal muscle, liver and plasma metabolomes were analyzed, showing marked energy and protein metabolism alterations in tumor hosts. SS-31 partially modulated skeletal muscle and liver metabolome, likely reflecting an improved systemic energy homeostasis. Conclusions: The results suggest that targeting mitochondrial function may be as important as targeting protein anabolism/catabolism for the prevention of cancer cachexia. With this in mind, prospective multi-modal therapies including SS-31 are warranted.

Mass spectrometry-based phospholipid imaging: methods and findings

Introduction: Imaging is a technique used for direct visualization of the internal structure or distribution of biomolecules of a living system in a two-dimensional or three-dimensional fashion. Phospholipids are important structural components of biological membranes and have been reported to be associated with various human diseases. Therefore, the visualization of phospholipids is crucial to understand the underlying mechanism of cellular and molecular processes in normal and diseased conditions. Areas covered: Mass spectrometry imaging (MSI) has enabled the label-free imaging of individual phospholipids in biological tissues and cells. The commonly used MSI techniques include matrix-assisted laser desorption ionization-MSI (MALDI-MSI), desorption electrospray ionization-MSI (DESI-MSI), and secondary ion mass spectrometry (SIMS) imaging. This special report described those methods, summarized the findings, and discussed the future development for the imaging of phospholipids. Expert opinion: Phospholipids imaging in complex biological samples has been significantly benefited from the development of MSI methods. In MALDI-MSI, novel matrix that produces homogenous crystals exclusively with polar lipids is important for phospholipids imaging with greater efficiency and higher spatial resolution. DESI-MSI has the potential of live imaging of the biological surface while SIMS is expected to image at the subcellular level in the near future.

Evaluation of immunohistopathological profile of tubular and solid canine mammary carcinomas

Breast cancer is the most common cancer in women, but the incidence of mammary carcinoma in female dogs is even higher than in humans. These two tumors have similarities that can be seen by its biological behavior, molecular genetic alterations, and histology. This suggest that female dogs can be an excellent model for preclinical oncological studies. And the mammary carcinoma most frequently found in this species is the tubular and solid carcinomas. The extracellular matrix (ECM) has an important role in the progression of these tumors. Because of that we proposed to evaluate the ECM components of these carcinomas through histology with specific stains such as Masson's Trichrome, Picrosirius Red and the technique of scanning electron microscopy. With that, we found the presence of collagen fibers in the tubular carcinoma and around its parenchyma. On the other hand, the solid carcinoma presented collagen fibers throughout the parenchyma and around each tumor cell. With the transmission electron microscopy, we observed the presence of mitochondrias and rough endoplasmic reticulum in both tumors. And finally, we evaluated the expression of proteins through the immunohistochemistry, in which we found a high expression of VEGF, PCNA, CK-18 and vimentin in solid carcinoma, and a positive mark in the tubular and solid carcinoma for collagen I, III and fibronectin. Thus, we demonstrated some differences in the ECM of these mammary carcinomas, allowing a better understanding of its histological characteristics, and these data may contribute to future studies about therapies focused on tumors ECM.

Localization of Carbon-Carbon Double Bond and Cyclopropane Sites in Cardiolipins via Gas-Phase Charge Inversion Reactions

Cardiolipins (CLs) are comprised of two phosphatic acid moieties bound to a central glycerol backbone and are substituted with four acyl chains. Consequently, a vast number of distinct CL structures are possible in different biological contexts, representing a significant analytical challenge. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) has become a widely used approach for the detection, characterization, and quantitation of complex lipids, including CLs. Central to this approach is fragmentation of the [CLs - H]- or [CL - 2H]2- anions by collision-induced dissociation (CID). Product ions in the resulting tandem mass spectra confirm the CL subclass assignment and reveal the numbers of carbons and degrees of unsaturation in each of the acyl chains. Conventional CID, however, affords limited structural elucidation of the fatty acyl chains, failing to discriminate isomers arising from different site(s) of unsaturation or cyclopropanation and potentially obscuring their metabolic origins. Here, we report the application of charge inversion ion/ion chemistry in the gas phase to enhance the structural elucidation of CLs. Briefly, CID of [CL - H]2- anions generated via negative ion ESI allowed for the assignment of individual fatty acyl substituents and phosphatidic acid moieties. Next, gas-phase derivatization of the resulting CL product ions, including fatty acyl carboxylate anions, was effected with gas-phase ion/ion charge inversion reactions with tris-phenanthroline magnesium reagent dications. Subsequent isolation and activation of the charge-inverted fatty acyl complex cations permitted the localization of both carbon-carbon double bond and cyclopropane motifs within each of the four acyl chains of CLs. This approach was applied to the de novo elucidation of unknown CLs in a biological extract revealing distinct isomeric populations and regiochemical relationships between double bonds and carbocyles.

Mass Spectrometry-Based Shotgun Lipidomics for Cancer Research

Shotgun lipidomics is an analytical approach for large-scale and systematic analysis of the composition, structure, and quantity of cellular lipids directly from lipid extracts of biological samples by mass spectrometry. This approach possesses advantages of high throughput and quantitative accuracy, especially in absolute quantification. As cancer research deepens at the level of quantitative biology and metabolomics, the demand for lipidomics approaches such as shotgun lipidomics is becoming greater. In this chapter, the principles, approaches, and some applications of shotgun lipidomics for cancer research are overviewed.

On the Origin of ATP Synthesis in Cancer

ATP is required for mammalian cells to remain viable and to perform genetically programmed functions. Maintenance of the ΔG′_ATP hydrolysis of −56 kJ/mole is the endpoint of both genetic and metabolic processes required for life. Various anomalies in mitochondrial structure and function prevent maximal ATP synthesis through OxPhos in cancer cells. Little ATP synthesis would occur through glycolysis in cancer cells that express the dimeric form of pyruvate kinase M2. Mitochondrial substrate level phosphorylation (mSLP) in the glutamine-driven glutaminolysis pathway, substantiated by the succinate-CoA ligase reaction in the TCA cycle, can partially compensate for reduced ATP synthesis through both OxPhos and glycolysis. A protracted insufficiency of OxPhos coupled with elevated glycolysis and an auxiliary, fully operational mSLP, would cause a cell to enter its default state of unbridled proliferation with consequent dedifferentiation and apoptotic resistance, i.e., cancer. The simultaneous restriction of glucose and glutamine offers a therapeutic strategy for managing cancer.

Cardiolipin, the Mitochondrial Signature Lipid: Implication in Cancer

Cardiolipins (CLs) are specific phospholipids of the mitochondria composing about 20% of the inner mitochondria membrane (IMM) phospholipid mass. Dysregulation of CL metabolism has been observed in several types of cancer. In most cases, the evidence for a role for CL in cancer is merely correlative, suggestive, ambiguous, and cancer-type dependent. In addition, CLs could play a pivotal role in several mitochondrial functions/parameters such as bioenergetics, dynamics, mitophagy, and apoptosis, which are involved in key steps of cancer aggressiveness (i.e., migration/invasion and resistance to treatment). Therefore, this review focuses on studies suggesting that changes in CL content and/or composition, as well as CL metabolism enzyme levels, may be linked with the progression and the aggressiveness of some types of cancer. Finally, we also introduce the main mitochondrial function in which CL could play a pivotal role with a special focus on its implication in cancer development and therapy.

Enhancing detection and characterization of lipids using charge manipulation in electrospray ionization-tandem mass spectrometry

Heightened awareness regarding the implication of disturbances in lipid metabolism with respect to prevalent human-related pathologies demands analytical techniques that provide unambiguous structural characterization and accurate quantitation of lipids in complex biological samples. The diversity in molecular structures of lipids along with their wide range of concentrations in biological matrices present formidable analytical challenges. Modern mass spectrometry (MS) offers an unprecedented level of analytical power in lipid analysis, as many advancements in the field of lipidomics have been facilitated through novel applications of and developments in electrospray ionization tandem mass spectrometry (ESI-MS/MS). ESI allows for the formation of intact lipid ions with little to no fragmentation and has become widely used in contemporary lipidomics experiments due to its sensitivity, reproducibility, and compatibility with condensed-phase modes of separation, such as liquid chromatography (LC). Owing to variations in lipid functional groups, ESI enables partial chemical separation of the lipidome, yet the preferred ion-type is not always formed, impacting lipid detection, characterization, and quantitation. Moreover, conventional ESI-MS/MS approaches often fail to expose diverse subtle structural features like the sites of unsaturation in fatty acyl constituents or acyl chain regiochemistry along the glycerol backbone, representing a significant challenge for ESI-MS/MS. To overcome these shortcomings, various charge manipulation strategies, including charge-switching, have been developed to transform ion-type and charge state, with aims of increasing sensitivity and selectivity of ESI-MS/MS approaches. Importantly, charge manipulation approaches afford enhanced ionization efficiency, improved mixture analysis performance, and access to informative fragmentation channels. Herein, we present a critical review of the current suite of solution-based and gas-phase strategies for the manipulation of lipid ion charge and type relevant to ESI-MS/MS.

The Warburg Effect 97 Years after Its Discovery

The deregulation of the oxidative metabolism in cancer, as shown by the increased aerobic glycolysis and impaired oxidative phosphorylation (Warburg effect), is coordinated by genetic changes leading to the activation of oncogenes and the loss of oncosuppressor genes. The understanding of the metabolic deregulation of cancer cells is necessary to prevent and cure cancer. In this review, we illustrate and comment the principal metabolic and molecular variations of cancer cells, involved in their anomalous behavior, that include modifications of oxidative metabolism, the activation of oncogenes that promote glycolysis and a decrease of oxygen consumption in cancer cells, the genetic susceptibility to cancer, the molecular correlations involved in the metabolic deregulation in cancer, the defective cancer mitochondria, the relationships between the Warburg effect and tumor therapy, and recent studies that reevaluate the Warburg effect. Taken together, these observations indicate that the Warburg effect is an epiphenomenon of the transformation process essential for the development of malignancy.

Carnitine Traffic in Cells. Link With Cancer

Metabolic flexibility is a peculiar hallmark of cancer cells. A growing number of observations reveal that tumors can utilize a wide range of substrates to sustain cell survival and proliferation. The diversity of carbon sources is indicative of metabolic heterogeneity not only across different types of cancer but also within those sharing a common origin. Apart from the well-assessed alteration in glucose and amino acid metabolisms, there are pieces of evidence that cancer cells display alterations of lipid metabolism as well; indeed, some tumors use fatty acid oxidation (FAO) as the main source of energy and express high levels of FAO enzymes. In this metabolic pathway, the cofactor carnitine is crucial since it serves as a “shuttle-molecule” to allow fatty acid acyl moieties entering the mitochondrial matrix where these molecules are oxidized via the β-oxidation pathway. This role, together with others played by carnitine in cell metabolism, underlies the fine regulation of carnitine traffic among different tissues and, within a cell, among different subcellular compartments. Specific membrane transporters mediate carnitine and carnitine derivatives flux across the cell membranes. Among the SLCs, the plasma membrane transporters OCTN2 (Organic cation transport novel 2 or SLC22A5), CT2 (Carnitine transporter 2 or SLC22A16), MCT9 (Monocarboxylate transporter 9 or SLC16A9) and ATB^{0, +} [Sodium- and chloride-dependent neutral and basic amino acid transporter B(0+) or SLC6A14] together with the mitochondrial membrane transporter CAC (Mitochondrial carnitine/acylcarnitine carrier or SLC25A20) are the most acknowledged to mediate the flux of carnitine. The concerted action of these proteins creates a carnitine network that becomes relevant in the context of cancer metabolic rewiring. Therefore, molecular mechanisms underlying modulation of function and expression of carnitine transporters are dealt with furnishing some perspective for cancer treatment.

Mitochondria membrane transformations in colon and prostate cancer and their biological implications

Mitochondria have emerged as important determinants in cancer progression and malignancy. However, the role of mitochondrial membranes in cancer onset and progression has not been thoroughly investigated. This study compares the structural and functional properties of mitochondrial membranes in prostate and colon cancer cells in comparison to normal mitochondria, and possible therapeutic implications of these membrane changes. Specifically, isolation of cell mitochondria and preparation of inverted sub-mitochondrial particles (SMPs) illuminated significant cancer-induced modulations of membrane lipid compositions, fluidity, and activity of cytochrome c oxidase, one of the key mitochondrial enzymes. The experimental data further show that cancer-associated membrane transformations may account for mitochondria targeting by betulinic acid and resveratrol, known anti-cancer molecules. Overall, this study probes the relationship between cancer and mitochondrial membrane transformations, underlying a potential therapeutic significance for mitochondrial membrane targeting in cancer.

Free-Radical-Mediated Formation of Trans-Cardiolipin Isomers, Analytical Approaches for Lipidomics and Consequences of the Structural Organization of Membranes

Free-radical-mediated processes, such as peroxidation, isomerization and hydrogenation affecting fatty acid integrity and biological functions, have a trans-disciplinary relevance. Cardiolipins (CL, (1,3-diphosphatidyl-sn-glycerol)) and tetra-linoleoyl-CL are complex phospholipids, exclusively present in the Inner Mitochondrial Membrane (IMM) lipids, where they maintain membrane integrity and regulate enzyme functionalities. Peroxidation pathways and fatty acid remodeling are known causes of mitochondrial disfunctions and pathologies, including cancer. Free-radical-mediated isomerization with the change of the cis CL into geometrical trans isomers is an unknown process with possible consequences on the supramolecular membrane lipid organization. Here, the formation of mono-trans CL (MT-CL) and other trans CL isomers (T-CL) is reported using CL from bovine heart mitochondria and thiyl radicals generated by UV-photolysis from 2-mercaptoethanol. Analytical approaches for CL isomer separation and identification via ¹H/¹³C NMR are provided, together with the chemical study of CL derivatization to fatty acid methyl esters (FAME), useful for lipidomics and metabolomics research. Kinetics information of the radical chain isomerization process was obtained using γ-irradiation conditions. The CL isomerization affected the structural organization of membranes, as tested by the reduction in unilamellar liposome diameter, and accompanied the well-known process of oxidative consumption induced by Fenton reagents. These results highlight a potential new molecular modification pathway of mitochondrial lipids with wide applications to membrane functions and biological consequences.

Proton Transfer Reactions for the Gas-Phase Separation, Concentration, and Identification of Cardiolipins

Cardiolipin (CL) analysis demands high specificity, due to the extensive diversity of CL structures, and high sensitivity, due to their low relative abundance within the lipidome. While electrospray ionization mass spectrometry (ESI-MS) is the most widely used technology in lipidomics, the potential for multiple charging presents unique challenges for CL identification and quantification. Depending on the conditions, ESI-MS of lipid extracts in negative ion mode can give rise to cardiolipins ionized as both singly and doubly deprotonated anions. This signal degeneracy diminishes the signal-to-noise ratio, while in addition (for direct infusion), the dianion population falls within a m/z range already heavily congested with monoanions from more abundant glycerophospholipid subclasses. Herein, we describe a direct infusion strategy for CL profiling from total lipid extracts utilizing gas-phase proton-transfer ion/ion reactions. In this approach, lipid extracts are ionized by negative ion ESI generating both singly deprotonated phospholipids and doubly deprotonated CL anions. Charge reduction of the negative ion population by ion/ion reactions leads to an enhancement in singly deprotonated [CL - H]- species via proton transfer to the corresponding [CL - 2H]2-̅ dianions. To concentrate the [CL - H]- anion signal, multiple iterations of ion accumulation and proton-transfer ion/ion reaction can be performed prior to subsequent interrogation. Mass selection and collisional activation of the enriched population of [CL - H]- anions facilitates the assignment of individual fatty acyl substituents and phosphatidic acid moieties. Demonstrated advantages of this new approach derive from the improved performance in complex mixture analysis affording detailed characterization of low abundant CLs directly from a total biological extract.

Lysocardiolipin acyltransferase regulates NSCLC cell proliferation and migration by modulating mitochondrial dynamics

Lysocardiolipin acyltransferase (LYCAT), a cardiolipin (CL)-remodeling enzyme, is crucial for maintaining normal mitochondrial function and vascular development. Despite the well-characterized role for LYCAT in the regulation of mitochondrial dynamics, its involvement in lung cancer, if any, remains incompletely understood. In this study, in silico analysis of TCGA lung cancer data sets revealed a significant increase in LYCAT expression, which was later corroborated in human lung cancer tissues and immortalized lung cancer cell lines via indirect immunofluorescence and immunoblotting, respectively. Stable knockdown of LYCAT in NSCLC cell lines not only reduced CL and increased monolyso-CL levels but also reduced in vivo tumor growth, as determined by xenograft studies in athymic nude mice. Furthermore, blocking LYCAT activity using a LYCAT mimetic peptide attenuated cell migration, suggesting a novel role for LYCAT activity in promoting NSCLC. Mechanistically, the pro-proliferative effects of LYCAT were mediated by an increase in mitochondrial fusion and a G₁/S cell cycle transition, both of which are linked to increased cell proliferation. Taken together, these results demonstrate a novel role for LYCAT in promoting NSCLC and suggest that targeting LYCAT expression or activity in NSCLC may provide new avenues for the therapeutic treatment of lung cancer.

De Novo Lipogenesis Alters the Phospholipidome of Esophageal Adenocarcinoma

The incidence of esophageal adenocarcinoma is rising, survival remains poor, and new tools to improve early diagnosis and precise treatment are needed. Cancer phospholipidomes quantified with mass spectrometry imaging (MSI) can support objective diagnosis in minutes using a routine frozen tissue section. However, whether MSI can objectively identify primary esophageal adenocarcinoma is currently unknown and represents a significant challenge, as this microenvironment is complex with phenotypically similar tissue-types. Here, we used desorption electrospray ionization-MSI (DESI-MSI) and bespoke chemometrics to assess the phospholipidomes of esophageal adenocarcinoma and relevant control tissues. Multivariate models derived from phospholipid profiles of 117 patients were highly discriminant for esophageal adenocarcinoma both in discovery (AUC = 0.97) and validation cohorts (AUC = 1). Among many other changes, esophageal adenocarcinoma samples were markedly enriched for polyunsaturated phosphatidylglycerols with longer acyl chains, with stepwise enrichment in premalignant tissues. Expression of fatty acid and glycerophospholipid synthesis genes was significantly upregulated, and characteristics of fatty acid acyls matched glycerophospholipid acyls. Mechanistically, silencing the carbon switch ACLY in esophageal adenocarcinoma cells shortened glycerophospholipid chains, linking de novo lipogenesis to the phospholipidome. Thus, DESI-MSI can objectively identify invasive esophageal adenocarcinoma from a number of premalignant tissues and unveils mechanisms of phospholipidomic reprogramming. SIGNIFICANCE: These results call for accelerated diagnosis studies using DESI-MSI in the upper gastrointestinal endoscopy suite, as well as functional studies to determine how polyunsaturated phosphatidylglycerols contribute to esophageal carcinogenesis.

Monolysocardiolipin (MLCL) interactions with mitochondrial membrane proteins

Monolysocardiolipin (MLCL) is a three-tailed variant of cardiolipin (CL), the signature lipid of mitochondria. MLCL is not normally found in healthy tissue but accumulates in mitochondria of people with Barth syndrome (BTHS), with an overall increase in the MLCL:CL ratio. The reason for MLCL accumulation remains to be fully understood. The effect of MLCL build-up and decreased CL content in causing the characteristics of BTHS are also unclear. In both cases, an understanding of the nature of MLCL interaction with mitochondrial proteins will be key. Recent work has shown that MLCL associates less tightly than CL with proteins in the mitochondrial inner membrane, suggesting that MLCL accumulation is a result of CL degradation, and that the lack of MLCL–protein interactions compromises the stability of the protein-dense mitochondrial inner membrane, leading to a decrease in optimal respiration. There is some data on MLCL–protein interactions for proteins involved in the respiratory chain and in apoptosis, but there remains much to be understood regarding the nature of MLCL–protein interactions. Recent developments in structural, analytical and computational approaches mean that these investigations are now possible. Such an understanding will be key to further insights into how MLCL accumulation impacts mitochondrial membranes. In turn, these insights will help to support the development of therapies for people with BTHS and give a broader understanding of other diseases involving defective CL content.

The Warburg Effect, Lactate, and Nearly a Century of Trying to Cure Cancer

Nearly 100 years ago, Otto Warburg undertook a study of tumor metabolism, and discovered increased lactate caused by increased glycolysis in cancer cells. His experiments were conducted in the presence of excess oxygen, but today tumor tissue is known to be a hypoxic environment. However, an increase of glycolysis and lactate production is still a valid observation. Numerous abnormalities and mutations of metabolic enzymes have been found in many cancers. For example, pyruvate kinase M2 has been associated with many cancers and is a major contributor to directing glycolysis into fermentation, forming lactate. Increases in several enzymes, including glucose 6-phosphate dehydrogenase, pyruvate kinase M2, Rad6, or deficiency of other enzymes such as succinate dehydrogenase, all may contribute directly or indirectly to increases in lactate associated with the Warburg effect. In addition, the increased lactate and acid-base changes are modified further by monocarboxylate transporters and carbonic anhydrase, which contribute to alkalinizing tumor cells while acidifying the tumor extracellular environment. This acidification leads to cancer spread. Fully understanding the mechanisms underlying the Warburg effect should provide new approaches to cancer treatment.