Metabolic rewiring in drug resistant cells exhibit higher OXPHOS and fatty acids as preferred major source to cellular energetics

DNA-PKcs-mediated transcriptional regulation of TOP2B drives chemoresistance in acute myeloid leukemia

Anthracyclines, topoisomerase II enzyme poisons that cause DNA damage, are the mainstay of acute myeloid leukemia (AML) treatment. However, acquired resistance to anthracyclines leads to relapse, which currently lacks effective treatment and is the cause of poor survival in individuals with AML. Therefore, the identification of the mechanisms underlying anthracycline resistance remains an unmet clinical need. Here, using patient-derived primary cultures and clinically relevant cellular models that recapitulate acquired anthracycline resistance in AML, we have found that GCN5 (also known as KAT2A) mediates transcriptional upregulation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in AML relapse, independently of the DNA-damage response. We demonstrate that anthracyclines fail to induce DNA damage in resistant cells, owing to the loss of expression of their target enzyme, TOP2B; this was caused by DNA-PKcs directly binding to its promoter upstream region as a transcriptional repressor. Importantly, DNA-PKcs kinase activity inhibition re-sensitized AML relapse primary cultures and cells resistant to mitoxantrone, and abrogated their tumorigenic potential in a xenograft mouse model. Taken together, our findings identify a GCN5-DNA-PKcs-TOP2B transcriptional regulatory axis as the mechanism underlying anthracycline resistance, and demonstrate the therapeutic potential of DNA-PKcs inhibition to re-sensitize resistant AML relapse cells to anthracycline.

Lipid metabolism as a target for cancer drug resistance: progress and prospects

Cancer is the world's leading cause of human death today, and the treatment process of cancer is highly complex. Chemotherapy and targeted therapy are commonly used in cancer treatment, and the emergence of drug resistance is a significant problem in cancer treatment. Therefore, the mechanism of drug resistance during cancer treatment has become a hot issue in current research. A series of studies have found that lipid metabolism is closely related to cancer drug resistance. This paper details the changes of lipid metabolism in drug resistance and how lipid metabolism affects drug resistance. More importantly, most studies have reported that combination therapy may lead to changes in lipid-related metabolic pathways, which may reverse the development of cancer drug resistance and enhance or rescue the sensitivity to therapeutic drugs. This paper summarizes the progress of drug design targeting lipid metabolism in improving drug resistance, and providing new ideas and strategies for future tumor treatment. Therefore, this paper reviews the issues of combining medications with lipid metabolism and drug resistance.

Rewiring of mitochondrial metabolism in therapy-resistant cancers: permanent and plastic adaptations

Deregulation of tumor cell metabolism is widely recognized as a "hallmark of cancer." Many of the selective pressures encountered by tumor cells, such as exposure to anticancer therapies, navigation of the metastatic cascade, and communication with the tumor microenvironment, can elicit further rewiring of tumor cell metabolism. Furthermore, phenotypic plasticity has been recently appreciated as an emerging "hallmark of cancer." Mitochondria are dynamic organelles and central hubs of metabolism whose roles in cancers have been a major focus of numerous studies. Importantly, therapeutic approaches targeting mitochondria are being developed. Interestingly, both plastic (i.e., reversible) and permanent (i.e., stable) metabolic adaptations have been observed following exposure to anticancer therapeutics. Understanding the plastic or permanent nature of these mechanisms is of crucial importance for devising the initiation, duration, and sequential nature of metabolism-targeting therapies. In this review, we compare permanent and plastic mitochondrial mechanisms driving therapy resistance. We also discuss experimental models of therapy-induced metabolic adaptation, therapeutic implications for targeting permanent and plastic metabolic states, and clinical implications of metabolic adaptations. While the plasticity of metabolic adaptations can make effective therapeutic treatment challenging, understanding the mechanisms behind these plastic phenotypes may lead to promising clinical interventions that will ultimately lead to better overall care for cancer patients.

Targeting metabolic vulnerabilities to overcome resistance to therapy in acute myeloid leukemia

Malignant hematopoietic cells gain metabolic plasticity, reorganize anabolic mechanisms to improve anabolic output and prevent oxidative damage, and bypass cell cycle checkpoints, eventually outcompeting normal hematopoietic cells. Current therapeutic strategies of acute myeloid leukemia (AML) are based on prognostic stratification that includes mutation profile as the closest surrogate to disease biology. Clinical efficacy of targeted therapies, e.g., agents targeting mutant FMS-like tyrosine kinase 3 (FLT3) and isocitrate dehydrogenase 1 or 2, are mostly limited to the presence of relevant mutations. Recent studies have not only demonstrated that specific mutations in AML create metabolic vulnerabilities but also highlighted the efficacy of targeting metabolic vulnerabilities in combination with inhibitors of these mutations. Therefore, delineating the functional relationships between genetic stratification, metabolic dependencies, and response to specific inhibitors of these vulnerabilities is crucial for identifying more effective therapeutic regimens, understanding resistance mechanisms, and identifying early response markers, ultimately improving the likelihood of cure. In addition, metabolic changes occurring in the tumor microenvironment have also been reported as therapeutic targets. The metabolic profiles of leukemia stem cells (LSCs) differ, and relapsed/refractory LSCs switch to alternative metabolic pathways, fueling oxidative phosphorylation (OXPHOS), rendering them therapeutically resistant. In this review, we discuss the role of cancer metabolic pathways that contribute to the metabolic plasticity of AML and confer resistance to standard therapy; we also highlight the latest promising developments in the field in translating these important findings to the clinic and discuss the tumor microenvironment that supports metabolic plasticity and interplay with AML cells.

A Handheld Visible Resonance Raman Analyzer Used in Intraoperative Detection of Human Glioma

There is still a lack of reliable intraoperative tools for glioma diagnosis and to guide the maximal safe resection of glioma. We report continuing work on the optical biopsy method to detect glioma grades and assess glioma boundaries intraoperatively using the VRR-LRRTM Raman analyzer, which is based on the visible resonance Raman spectroscopy (VRR) technique. A total of 2220 VRR spectra were collected during surgeries from 63 unprocessed fresh glioma tissues using the VRR-LRRTM Raman analyzer. After the VRR spectral analysis, we found differences in the native molecules in the fingerprint region and in the high-wavenumber region, and differences between normal (control) and different grades of glioma tissues. A principal component analysis–support vector machine (PCA-SVM) machine learning method was used to distinguish glioma tissues from normal tissues and different glioma grades. The accuracy in identifying glioma from normal tissue was over 80%, compared with the gold standard of histopathology reports of glioma. The VRR-LRRTM Raman analyzer may be a new label-free, real-time optical molecular pathology tool aiding in the intraoperative detection of glioma and identification of tumor boundaries, thus helping to guide maximal safe glioma removal and adjacent healthy tissue preservation.

Proteogenomic analysis of acute myeloid leukemia associates relapsed disease with reprogrammed energy metabolism both in adults and children

Despite improvement of current treatment strategies and novel targeted drugs, relapse and treatment resistance largely determine the outcome for acute myeloid leukemia (AML) patients. To identify the underlying molecular characteristics, numerous studies have been aimed to decipher the genomic- and transcriptomic landscape of AML. Nevertheless, further molecular changes allowing malignant cells to escape treatment remain to be elucidated. Mass spectrometry is a powerful tool enabling detailed insights into proteomic changes that could explain AML relapse and resistance. Here, we investigated AML samples from 47 adult and 22 pediatric patients at serial time-points during disease progression using mass spectrometry-based in-depth proteomics. We show that the proteomic profile at relapse is enriched for mitochondrial ribosomal proteins and subunits of the respiratory chain complex, indicative of reprogrammed energy metabolism from diagnosis to relapse. Further, higher levels of granzymes and lower levels of the anti-inflammatory protein CR1/CD35 suggest an inflammatory signature promoting disease progression. Finally, through a proteogenomic approach, we detected novel peptides, which present a promising repertoire in the search for biomarkers and tumor-specific druggable targets. Altogether, this study highlights the importance of proteomic studies in holistic approaches to improve treatment and survival of AML patients.

Unraveling the Peculiar Features of Mitochondrial Metabolism and Dynamics in Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among men in Western countries. Mitochondria, the "powerhouse" of cells, undergo distinctive metabolic and structural dynamics in different types of cancer. PCa cells experience peculiar metabolic changes during their progression from normal epithelial cells to early-stage and, progressively, to late-stage cancer cells. Specifically, healthy cells display a truncated tricarboxylic acid (TCA) cycle and inefficient oxidative phosphorylation (OXPHOS) due to the high accumulation of zinc that impairs the activity of m-aconitase, the enzyme of the TCA cycle responsible for the oxidation of citrate. During the early phase of cancer development, intracellular zinc levels decrease leading to the reactivation of m-aconitase, TCA cycle and OXPHOS. PCa cells change their metabolic features again when progressing to the late stage of cancer. In particular, the Warburg effect was consistently shown to be the main metabolic feature of late-stage PCa cells. However, accumulating evidence sustains that both the TCA cycle and the OXPHOS pathway are still present and active in these cells. The androgen receptor axis as well as mutations in mitochondrial genes involved in metabolic rewiring were shown to play a key role in PCa cell metabolic reprogramming. Mitochondrial structural dynamics, such as biogenesis, fusion/fission and mitophagy, were also observed in PCa cells. In this review, we focus on the mitochondrial metabolic and structural dynamics occurring in PCa during tumor development and progression; their role as effective molecular targets for novel therapeutic strategies in PCa patients is also discussed.

Lactic acid fermentation: A maladaptive mechanism and an evolutionary throwback boosting cancer drug resistance

After four decades of research primarily focused on tumour genetics, the importance of metabolism in tumour biology is receiving renewed attention. Cancer cells undergo energy, biosynthetic and metabolic rewiring, which involves several pathways with a prevalent change from oxidative phosphorylation (OXPHOS) to lactic acid fermentation, known as the Warburg effect. During carcinogenesis, microenvironmental changes can trigger the transition from OXPHOS to lactic acid fermentation, an ancient form of energy supply, mimicking the behaviour of certain anaerobic unicellular organisms according to "atavistic" models of cancer. However, the role of this transition as a mechanism of cancer drug resistance is unclear. Here, we hypothesise that the metabolic rewiring of cancer cells to fermentation can be triggered, enhanced, and sustained by exposure to chronic or high-dose chemotherapy, thereby conferring resistance to drug therapy. We try to expand on the idea that metabolic reprogramming from OXPHOS to lactate fermentation in drug-resistant tumour cells occurs as a general phenotypic mechanism in any type of cancer, regardless of tumour cell heterogeneity, biodiversity, and genetic characteristics. This metabolic response may therefore represent a common feature in cancer biology that could be exploited for therapeutic purposes to overcome chemotherapy resistance, which is currently a major challenge in cancer treatment.

Lipotoxicity as a Barrier for T Cell-Based Therapies

Nowadays, T-cell-based approaches play an increasing role in cancer treatment. In particular, the use of (genetically engineered) T-cells has heralded a novel era for various diseases with previously poor outcomes. Concurrently, the relationship between the functional behavior of immune cells and their metabolic state, known as immunometabolism, has been found to be an important determinant for the success of immunotherapy. In this context, immune cell metabolism is not only controlled by the expression of transcription factors, enzymes and transport proteins but also by nutrient availability and the presence of intermediate metabolites. The lack of as well as an oversupply of nutrients can be detrimental and lead to cellular dysfunction and damage, potentially resulting in reduced metabolic fitness and/or cell death. This review focusses on the detrimental effects of excessive exposure of T cells to fatty acids, known as lipotoxicity, in the context of an altered lipid tumor microenvironment. Furthermore, implications of T cell-related lipotoxicity for immunotherapy will be discussed, as well as potential therapeutic approaches.

Decreased Levels of GSH Are Associated with Platinum Resistance in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancer (HGSOC) is the most common and aggressive OC histotype. Although initially sensitive to standard platinum-based chemotherapy, most HGSOC patients relapse and become chemoresistant. We have previously demonstrated that platinum resistance is driven by a metabolic shift toward oxidative phosphorylation via activation of an inflammatory response, accompanied by reduced cholesterol biosynthesis and increased uptake of exogenous cholesterol. To better understand metabolic remodeling in OC, herein we performed an untargeted metabolomic analysis, which surprisingly showed decreased reduced glutathione (GSH) levels in resistant cells. Accordingly, we found reduced levels of enzymes involved in GSH synthesis and recycling, and compensatory increased expression of thioredoxin reductase. Cisplatin treatment caused an increase of reduced GSH, possibly due to direct binding hindering its oxidation, and consequent accumulation of reactive oxygen species. Notably, expression of the cysteine-glutamate antiporter xCT, which is crucial for GSH synthesis, directly correlates with post-progression survival of HGSOC patients, and is significantly reduced in patients not responding to platinum-based therapy. Overall, our data suggest that cisplatin treatment could positively select cancer cells which are independent from GSH for the maintenance of redox balance, and thus less sensitive to cisplatin-induced oxidative stress, opening new scenarios for the GSH pathway as a therapeutic target in HGSOC.

Lipids in cancer: a global view of the contribution of lipid pathways to metastatic formation and treatment resistance

Lipids are essential constituents for malignant tumors, as they are absolutely required for tumor growth and dissemination. Provided by the tumor microenvironment (TME) or by cancer cells themselves through activation of de novo synthesis pathways, they orchestrate a large variety of pro-tumorigenic functions. Importantly, TME cells, especially immune cells, cancer-associated fibroblasts (CAFs) and cancer-associated adipocytes (CAAs), are also prone to changes in their lipid content, which hinder or promote tumor aggressiveness. In this review, we address the significant findings for lipid contribution in tumor progression towards a metastatic disease and in the poor response to therapeutic treatments. We also highlight the benefits of targeting lipid pathways in preclinical models to slow down metastasis development and overcome chemo-and immunotherapy resistance.

Inhibition of LPAR6 overcomes sorafenib resistance by switching glycolysis into oxidative phosphorylation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most threatening tumours in the world today. Pharmacological treatments for HCC mainly rely on protein kinase inhibitors, such as sorafenib and regorafenib. Even so, these approaches exhibit side effects and acquired drug resistance, which is an obstacle to HCC treatment. We have previously shown that selective lysophosphatidic acid receptor 6 (LPAR6) chemical antagonists inhibit HCC growth. Here, we investigated whether LPAR6 mediates resistance to sorafenib by affecting energy metabolism in HCC. To uncover the role of LPAR6 in drug resistance and cancer energy metabolism, we used a gain-of-function and loss-of-function approach in 2D tissue and 3D spheroids. LPAR6 was ectopically expressed in HLE cells (HLE-LPAR6) and knocked down in HepG2 (HepG2 LPAR6-shRNA). Measurements of oxygen consumption and lactate and pyruvate production were performed to assess the energy metabolism response of HCC cells to sorafenib treatment. We found that LPAR6 mediates the resistance of HCC cells to sorafenib by promoting lactic acid fermentation at the expense of oxidative phosphorylation (OXPHOS) and that the selective LPAR6 antagonist 9-xanthenyl acetate (XAA) can effectively overcome this resistance. Our study shows for the first time that an LPAR6-mediated metabolic mechanism supports sorafenib resistance in HCC and proposes a pharmacological approach to overcome it.

Pitavastatin Is Anti-Leukemic in a Bone Marrow Microenvironment Model of B-Lineage Acute Lymphoblastic Leukemia

Simple Summary

Chemoresistance after chemotherapy is a negative prognostic indicator for B-cell acute lymphoblastic leukemia (ALL), necessitating the search for novel therapies. By growing ALL cells together with bone marrow stromal cells, we developed a chemoresistant ALL model. Using this model, we found that the lipid lowering drug pitavastatin had antileukemic activity in this chemoresistant co-culture model. Our data suggests that pitavastatin may be a novel treatment option for repurposing in chemoresistant, relapse ALL.

Abstract

The lack of complete therapeutic success in the treatment of B-cell acute lymphoblastic leukemia (ALL) has been attributed, in part, to a subset of cells within the bone marrow microenvironment that are drug resistant. Recently, the cholesterol synthesis inhibitor, pitavastatin (PIT), was shown to be active in acute myeloid leukemia, prompting us to evaluate it in our in vitro co-culture model, which supports a chemo-resistant ALL population. We used phospho-protein profiling to evaluate the use of lipid metabolic active compounds in these chemo-resistant cells, due to the up-regulation of multiple active survival signals. In a co-culture with stromal cells, a shift towards anabolic processes occurred, which was further confirmed by assays showing increased lipid content. The treatment of REH leukemia cells with pitavastatin in the co-culture model resulted in significantly higher leukemic cell death than exposure to the standard-of-care chemotherapeutic agent, cytarabine (Ara-C). Our data demonstrates the use of pitavastatin as a possible alternative treatment strategy to improve patient outcomes in chemo-resistant, relapsed ALL.

Chemoprevention of Lung Cancer with a Combination of Mitochondria-Targeted Compounds

Simple Summary

Previous reports showed that mitochondria-targeted honokiol and mitochondria-targeted lonidamine potently inhibit complex-I- and complexes-I/II-induced respiration and cancer cell proliferation. In this study, we investigated the efficacy of combining mitochondria-targeted honokiol and mitochondria-targeted lonidamine treatments for lung cancer prevention. We found that their combination exhibited striking tumor inhibition in the benzo[a]pyrene-induced murine lung tumor model without causing detectable side effects. Using single-cell RNA sequencing, we found combined treatment has a clear advantage in that it can significantly inhibit two oncogenic pathways—STAT3 signaling and AKT/mTOR/p70S6K signaling. Such dual inhibition may contribute to the greater efficacy of the combined drug treatment. Therefore, the combination provides a novel option for lung cancer chemoprevention.

Abstract

Combined treatment targeting mitochondria may improve the efficacy of lung cancer chemoprevention. Here, mitochondria-targeted honokiol (Mito-HNK), an inhibitor of mitochondrial complex I and STAT3 phosphorylation, and mitochondria-targeted lonidamine (Mito-LND), an inhibitor of mitochondrial complexes I/II and AKT/mTOR/p70S6K signaling, were evaluated for their combinational chemopreventive efficacy on mouse lung carcinogenesis. All chemopreventive treatments began one-week post-carcinogen treatment and continued daily for 24 weeks. No evidence of toxicity (including liver toxicity) was detected by monitoring serum levels of alanine aminotransferase and aspartate aminotransferase enzymes. Mito-HNK or Mito-LND treatment alone reduced tumor load by 56% and 48%, respectively, whereas the combination of Mito-HNK and Mito-LND reduced tumor load by 83%. To understand the potential mechanism(s) of action for the observed combinatorial effects, single-cell RNA sequencing was performed using mouse tumors treated with Mito-HNK, Mito-LND, and their combination. In lung tumor cells, Mito-HNK treatment blocked the expression of genes involved in mitochondrial complex ǀ, oxidative phosphorylation, glycolysis, and STAT3 signaling. Mito-LND inhibited the expression of genes for mitochondrial complexes I/II, oxidative phosphorylation, and AKT/mTOR/p70S6K signaling in lung tumor cells. In addition to these changes, a combination of Mito-HNK with Mito-LND decreased arginine and proline metabolism, N-glycan biosynthesis, and tryptophan metabolism in lung tumor cells. Our results demonstrate that Mito-LND enhanced the antitumor efficacy of Mito-HNK, where both compounds inhibited common targets (oxidative phosphorylation) as well as unique targets for each agent (STAT3 and mTOR signaling). Therefore, the combination of Mito-HNK with Mito-LND may present an effective strategy for lung cancer chemoprevention.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Lack of Adverse Effects of Cold Physical Plasma-Treated Blood from Leukemia Patients: A Proof-of-Concept Study

Chronic lymphocytic leukemia (CLL) is the most common blood malignancy with multiple therapeutic challenges. Cold physical plasma has been considered a promising approach in cancer therapy in recent years. In this study, we aimed to evaluate the cytotoxic effect of cold plasma or plasma-treated solutions (PTS) on hematologic parameters in the whole blood of CLL patients. The mean red blood cell count, white blood cell (WBC) count, platelet and hemoglobin counts, and peripheral blood smear images did not significantly differ between treated and untreated samples in either CLL or healthy individuals. However, both direct plasma and indirect PTS treatment increased lipid peroxidation and RNS deposition in the whole blood of CLL patients and in healthy subjects. In addition, the metabolic activity of WBCs was decreased with 120 s of cold plasma or PTS treatment after 24 h and 48 h. However, cold plasma and PTS treatment did not affect the prothrombin time, partial thromboplastin time, nor hemolysis in either CLL patients or in healthy individuals. The present study identifies the components of cold plasma to reach the blood without disturbing the basic parameters important in hematology, confirming the idea that the effect of cold plasma may not be limited to solid tumors and possibly extends to hematological disorders. Further cellular and molecular studies are needed to determine which cells in CLL patients are targeted by cold plasma or PTS.

Clinically Relevant Oxygraphic Assay to Assess Mitochondrial Energy Metabolism in Acute Myeloid Leukemia Patients

Resistant acute myeloid leukemia (AML) exhibits mitochondrial energy metabolism changes compared to newly diagnosed AML. This phenotype is often observed by evaluating the mitochondrial oxygen consumption of blasts, but most of the oximetry protocols were established from leukemia cell lines without validation on primary leukemia cells. Moreover, the cultures and storage conditions of blasts freshly extracted from patient blood or bone marrow cause stress, which must be evaluated before determining oxidative phosphorylation (OXPHOS). Herein, we evaluated different conditions to measure the oxygen consumption of blasts using extracellular flow analyzers. We first determined the minimum number of blasts required to measure OXPHOS. Next, we compared the OXPHOS of blasts cultured for 3 h and 18 h after collection and found that to maintain metabolic organization for 18 h, cytokine supplementation is necessary. Cytokines are also needed when measuring OXPHOS in cryopreserved, thawed and recultured blasts. Next, the concentrations of respiratory chain inhibitors and uncoupler FCCP were established. We found that the FCCP concentration required to reach the maximal respiration of blasts varied depending on the patient sample analyzed. These protocols provided can be used in future clinical studies to evaluate OXPHOS as a biomarker and assess the efficacy of treatments targeting mitochondria.

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

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

Lipid Catabolism and ROS in Cancer: A Bidirectional Liaison

Although cancer cell metabolism was mainly considered to rely on glycolysis, with the concomitant impairment of mitochondrial metabolism, it has recently been demonstrated that several tumor types are sustained by oxidative phosphorylation (OXPHOS). In this context, endogenous fatty acids (FAs) deriving from lipolysis or lipophagy are oxidised into the mitochondrion, and are used as a source of energy through OXPHOS. Because the electron transport chain is the main source of ROS, cancer cells relying on fatty acid oxidation (FAO) need to be equipped with antioxidant systems that maintain the ROS levels under the death threshold. In those conditions, ROS can act as second messengers, favouring proliferation and survival. Herein, we highlight the different responses that tumor cells adopt when lipid catabolism is augmented, taking into account the different ROS fates. Many papers have demonstrated that the pro- or anti-tumoral roles of endogenous FA usage are hugely dependent on the tumor type, and on the capacity of cancer cells to maintain redox homeostasis. In light of this, clinical studies have taken advantage of the boosting of lipid catabolism to increase the efficacy of tumor therapy, whereas, in other contexts, antioxidant compounds are useful to reduce the pro-survival effects of ROS deriving from FAO.

Intraoperative detection of human meningioma using a handheld visible resonance Raman analyzer

To report for the first time the preliminary results for the evaluation of a VRR-LRR™ analyzer based on visible resonance Raman technique to identify human meningioma grades and margins intraoperatively. Unprocessed primary and recurrent solid human meningeal tissues were collected from 33 patients and underwent Raman analysis during surgeries. A total of 1180 VRR spectra were acquired from fresh solid tissues using a VRR-LRR™ analyzer. A confocal HR Evolution (HORIBA, France SAS) Raman system with 532-nm excitation wavelength was also used to collect data for part of the ex vivo samples after they were thawed from - 80 °C for comparison. The preliminary analysis led to the following observations. (1) The intensity ratio of VRR peaks of protein to fatty acid (I₂₉₃₄/I₂₈₈₈) decreased with the increase of meningioma grade. (2) The ratio of VRR peaks of phosphorylated protein to amid I (I₁₅₈₈/I₁₆₃₉) decreased for the higher grade of meningioma. (3) Three RR vibration modes at 1378, 3174, and 3224 cm^-1 which were related to the molecular vibrational bands of oxy-hemeprotein, amide B, and amide A protein significantly changed in peak intensities in the two types of meningioma tissues compared to normal tissue. (4) The changes in the intensities of VRR modes of carotenoids at 1156 and 1524 cm^-1 were also found in the meningioma boundary. The VRR-LRR™ analyzer demonstrates a new approach for label-free, rapid, and objective identification of primary human meningioma in quasi-clinical settings. The accuracy for detecting meningioma tissues using support vector machines (SVMs) was over 70% based on Raman peaks of key biomolecules and up to 100% using principal component analysis (PCA).

Aspects of the Tumor Microenvironment Involved in Immune Resistance and Drug Resistance

The tumor microenvironment (TME) is a complex and ever-changing "rogue organ" composed of its own blood supply, lymphatic and nervous systems, stroma, immune cells and extracellular matrix (ECM). These complex components, utilizing both benign and malignant cells, nurture the harsh, immunosuppressive and nutrient-deficient environment necessary for tumor cell growth, proliferation and phenotypic flexibility and variation. An important aspect of the TME is cellular crosstalk and cell-to-ECM communication. This interaction induces the release of soluble factors responsible for immune evasion and ECM remodeling, which further contribute to therapy resistance. Other aspects are the presence of exosomes contributed by both malignant and benign cells, circulating deregulated microRNAs and TME-specific metabolic patterns which further potentiate the progression and/or resistance to therapy. In addition to biochemical signaling, specific TME characteristics such as the hypoxic environment, metabolic derangements, and abnormal mechanical forces have been implicated in the development of treatment resistance. In this review, we will provide an overview of tumor microenvironmental composition, structure, and features that influence immune suppression and contribute to treatment resistance.

Nuclear localization of p65 reverses therapy-induced senescence

Senescence is the arrest of cell proliferation and is a tumor suppressor phenomenon. In a previous study, we have shown that therapy-induced senescence of glioblastoma multiforme (GBM) cells can prevent relapse of GBM tumors. Here, we demonstrate that ciprofloxacin-induced senescence in glioma-derived cell lines and primary glioma cultures is defined by SA-β-gal positivity, a senescence-associated secretory phenotype (SASP), a giant cell (GC) phenotype, increased levels of reactive oxygen species (ROS), γ-H2AX and a senescence-associated gene expression signature, and has three stages of senescence -initiation, pseudo-senescence and permanent senescence. Ciprofloxacin withdrawal during initiation and pseudo-senescence reinitiated proliferation in vitro and tumor formation in vivo Importantly, prolonged treatment with ciprofloxacin induced permanent senescence that failed to reverse following ciprofloxacin withdrawal. RNA-seq revealed downregulation of the p65 (RELA) transcription network, as well as incremental expression of SMAD pathway genes from initiation to permanent senescence. Ciprofloxacin withdrawal during initiation and pseudo-senescence, but not permanent senescence, increased the nuclear localization of p65 and escape from ciprofloxacin-induced senescence. By contrast, permanently senescent cells showed loss of nuclear p65 and increased apoptosis. Pharmacological inhibition or genetic knockdown of p65 upheld senescence in vitro and inhibited tumor formation in vivo Our study demonstrates that levels of nuclear p65 define the window of reversibility of therapy-induced senescence and that permanent senescence can be induced in GBM cells when the use of senotherapeutics is coupled with p65 inhibitors.

Lipid Metabolism and Resistance to Anticancer Treatment

Simple Summary

Cancer cells directly control nutrient uptake and utilization in a different manner from that of normal cells. These metabolic changes drive growth, proliferation of cancer cells as well as their ability to develop resistance to traditional therapies. We review published studies with pre-clinical models, showing the essential roles of lipid metabolism in anticancer drug resistance. We also discuss how changes in cellular lipid metabolism contribute to the acquisition of drug resistance and the new therapeutic opportunities to target lipid metabolism for treating drug resistant cancers.

Abstract

Metabolic reprogramming is crucial to respond to cancer cell requirements during tumor development. In the last decade, metabolic alterations have been shown to modulate cancer cells’ sensitivity to chemotherapeutic agents including conventional and targeted therapies. Recently, it became apparent that changes in lipid metabolism represent important mediators of resistance to anticancer agents. In this review, we highlight changes in lipid metabolism associated with therapy resistance, their significance and how dysregulated lipid metabolism could be exploited to overcome anticancer drug resistance.