Therapeutic targeting of PFKFB3 with a novel glycolytic inhibitor PFK158 promotes lipophagy and chemosensitivity in gynecologic cancers

Targeting the reprogrammed metabolism in H3.3K27M pediatric high-grade gliomas

Recent studies in Diffuse Midline Gliomas (DMG) demonstrated a strong connection between epigenome dysregulation and metabolic rewiring. Here, we evaluated the value of targeting a glycolytic protein named Phosphofructo-2-kinase/Fructose-2,6-bisphosphatase 3 (PFKFB3) in H3.3K27M DMG. We observed that the viability of H3.3K27M cells is dramatically reduced by PFK15, a potent inhibitor of PFKFB3. Furthermore, PFKFB3 inhibition induced apoptosis and G2/M arrest. Interestingly, CRISPR-Knockout of the K27M mutant allele has a synergistic effect on the observed phenotype. Altogether, we identified PFKFB3 as a new target for H3.3K27M DMG, making PFK15 a potential candidate for future animal studies and clinical trials.

Exploring the mystery of tumor metabolism: Warburg effect and mitochondrial metabolism fighting side by side

The metabolic reconfiguration of tumor cells constitutes a pivotal aspect of tumor proliferation and advancement. This study delves into two primary facets of tumor metabolism: the Warburg effect and mitochondrial metabolism, elucidating their contributions to tumor dominance. The Warburg effect facilitates efficient energy acquisition by tumor cells through aerobic glycolysis and lactic acid fermentation, offering metabolic advantages conducive to growth and proliferation. Simultaneously, mitochondrial metabolism, serving as the linchpin of sustained tumor vitality, orchestrates the tricarboxylic acid cycle and electron transport chain, furnishing a steadfast and dependable wellspring of biosynthesis for tumor cells. Regarding targeted therapy, this discourse examines extant strategies targeting tumor glycolysis and mitochondrial metabolism, underscoring their potential efficacy in modulating tumor metabolism while envisaging future research trajectories and treatment paradigms in the realm of tumor metabolism. By means of a thorough exploration of tumor metabolism, this study aspires to furnish crucial insights into the regulation of tumor metabolic processes, thereby furnishing valuable guidance for the development of novel therapeutic modalities. This comprehensive deliberation is poised to catalyze advancements in tumor metabolism research and offer novel perspectives and pathways for the formulation of cancer treatment strategies in the times ahead.

Metabolic Reprogramming in Tumor Immune Microenvironment: Impact on Immune Cell Function and Therapeutic Implications

Understanding of the metabolic reprogramming has revolutionized our insights into tumor progression and potential treatment. This review concentrates on the aberrant metabolic pathways in cancer cells within the tumor microenvironment (TME). Cancer cells differ from normal cells in their metabolic processing of glucose, amino acids, and lipids in order to adapt to heightened biosynthetic and energy needs. These metabolic shifts, which crucially alter lactic acid, amino acid and lipid metabolism, affect not only tumor cell proliferation but also TME dynamics. This review also explores the reprogramming of various immune cells in the TME. From a therapeutic standpoint, targeting these metabolic alterations represents a novel cancer treatment strategy. This review also discusses approaches targeting the regulation of metabolism of different nutrients in tumor cells and influencing the tumor microenvironment to enhance the immune response. In summary, this review summarizes metabolic reprogramming in cancer and its potential as a target for innovative therapeutic strategies, offering fresh perspectives on cancer treatment.

The regulatory roles and clinical significance of glycolysis in tumor

Metabolic reprogramming has been demonstrated to have a significant impact on the biological behaviors of tumor cells, among which glycolysis is an important form. Recent research has revealed that the heightened glycolysis levels, the abnormal expression of glycolytic enzymes, and the accumulation of glycolytic products could regulate the growth, proliferation, invasion, and metastasis of tumor cells and provide a favorable microenvironment for tumor development and progression. Based on the distinctive glycolytic characteristics of tumor cells, novel imaging tests have been developed to evaluate tumor proliferation and metastasis. In addition, glycolytic enzymes have been found to serve as promising biomarkers in tumor, which could provide assistance in the early diagnosis and prognostic assessment of tumor patients. Numerous glycolytic enzymes have been identified as potential therapeutic targets for tumor treatment, and various small molecule inhibitors targeting glycolytic enzymes have been developed to inhibit tumor development and some of them are already applied in the clinic. In this review, we systematically summarized recent advances of the regulatory roles of glycolysis in tumor progression and highlighted the potential clinical significance of glycolytic enzymes and products as novel biomarkers and therapeutic targets in tumor treatment.

Mechanisms and implications of podocyte autophagy in chronic kidney disease

Autophagy is a protective mechanism through which cells degrade and recycle proteins and organelles to maintain cellular homeostasis and integrity. An accumulating body of evidence underscores the significant impact of dysregulated autophagy on podocyte injury in chronic kidney disease (CKD). In this review, we provide a comprehensive overview of the diverse types of autophagy and their regulation in cellular homeostasis, with a specific emphasis on podocytes. Furthermore, we discuss recent findings that focus on the functional role of different types of autophagy during podocyte injury in chronic kidney disease. The intricate interplay between different types of autophagy and podocyte health requires further research, which is critical for understanding the pathogenesis of CKD and developing targeted therapeutic interventions.

Metabolic Regulation of Endothelial Cells: A New Era for Treating Wet Age-Related Macular Degeneration

Wet age-related macular degeneration (wet AMD) is a primary contributor to visual impairment and severe vision loss globally, but the prevailing treatments are often unsatisfactory. The development of conventional treatment strategies has largely been based on the understanding that the angiogenic switch of endothelial cells (ECs) is mainly dictated by angiogenic growth factors. Even though treatments targeting vascular endothelial growth factor (VEGF), like ranibizumab, are widely administered, more than half of patients still exhibit inadequate or null responses, suggesting the involvement of other pathogenic mechanisms. With advances in research in recent years, it has become well recognized that EC metabolic regulation plays an active rather than merely passive responsive role in angiogenesis. Disturbances of these metabolic pathways may lead to excessive neovascularization in angiogenic diseases such as wet AMD, therefore targeted modulation of EC metabolism represents a promising therapeutic strategy for wet AMD. In this review, we comprehensively discuss the potential applications of EC metabolic regulation in wet AMD treatment from multiple perspectives, including the involvement of ECs in wet AMD pathogenesis, the major endothelial metabolic pathways, and novel therapeutic approaches targeting metabolism for wet AMD.

A new strategy for screening novel functional genes involved in reduction of lipid droplet accumulation

Lipid droplets (LDs) are organelles that store excess lipids and provide fatty acids for energy production during starvation. LDs are also essential for cellular maintenance, but excessive accumulation of LDs triggers various cancers in addition to metabolic diseases such as diabetes. In this study, we aimed to develop a strategy to identify new genes that reduces accumulation of LDs in cancer cells using an RNA interference (RNAi) screening system employing artificial sequence-enriched shRNA libraries. Monitoring LDs by fluorescent activated cell sorting, the subsequently collected cumulative LDs cells, and shRNA sequence analysis identified a clone that potentially functioned to accumulate LDs. The clone showed no identical sequence to human Refseq. It showed very similar sequence to seven genes by allowing three mismatches. Among these genes, we identified the mediator complex subunit 6 (MED6) gene as a target of this shRNA. Silencing of MED6 led to an increase in LD accumulation and expression of the marker genes, PLIN2 and DGAT1, in fatty cells. MED6 is a member of the mediator complex that regulates RNA polymerase II transcription through transcription factor II. Some mediator complexes play important roles in both normal and pathophysiological transcription processes. These results suggest that MED6 transcriptionally regulates the genes involved in lipid metabolism and suppresses LD accumulation.

The role of DGAT1 and DGAT2 in regulating tumor cell growth and their potential clinical implications

Lipid metabolism is widely reprogrammed in tumor cells. Lipid droplet is a common organelle existing in most mammal cells, and its complex and dynamic functions in maintaining redox and metabolic balance, regulating endoplasmic reticulum stress, modulating chemoresistance, and providing essential biomolecules and ATP have been well established in tumor cells. The balance between lipid droplet formation and catabolism is critical to maintaining energy metabolism in tumor cells, while the process of energy metabolism affects various functions essential for tumor growth. The imbalance of synthesis and catabolism of fatty acids in tumor cells leads to the alteration of lipid droplet content in tumor cells. Diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2, the enzymes that catalyze the final step of triglyceride synthesis, participate in the formation of lipid droplets in tumor cells and in the regulation of cell proliferation, migration and invasion, chemoresistance, and prognosis in tumor. Several diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2 inhibitors have been developed over the past decade and have shown anti-tumor effects in preclinical tumor models and improvement of metabolism in clinical trials. In this review, we highlight key features of fatty acid metabolism and different paradigms of diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2 activities on cell proliferation, migration, chemoresistance, and prognosis in tumor, with the hope that these scientific findings will have potential clinical implications.

Targeting the Warburg effect: A revisited perspective from molecular mechanisms to traditional and innovative therapeutic strategies in cancer

Cancer reprogramming is an important facilitator of cancer development and survival, with tumor cells exhibiting a preference for aerobic glycolysis beyond oxidative phosphorylation, even under sufficient oxygen supply condition. This metabolic alteration, known as the Warburg effect, serves as a significant indicator of malignant tumor transformation. The Warburg effect primarily impacts cancer occurrence by influencing the aerobic glycolysis pathway in cancer cells. Key enzymes involved in this process include glucose transporters (GLUTs), HKs, PFKs, LDHs, and PKM2. Moreover, the expression of transcriptional regulatory factors and proteins, such as FOXM1, p53, NF-κB, HIF1α, and c-Myc, can also influence cancer progression. Furthermore, lncRNAs, miRNAs, and circular RNAs play a vital role in directly regulating the Warburg effect. Additionally, gene mutations, tumor microenvironment remodeling, and immune system interactions are closely associated with the Warburg effect. Notably, the development of drugs targeting the Warburg effect has exhibited promising potential in tumor treatment. This comprehensive review presents novel directions and approaches for the early diagnosis and treatment of cancer patients by conducting in-depth research and summarizing the bright prospects of targeting the Warburg effect in cancer.

Targeting natural killer cells: from basic biology to clinical application in hematologic malignancies

Natural killer (NK) cell belongs to innate lymphoid cell family that contributes to host immunosurveillance and defense without pre-immunization. Emerging studies have sought to understand the underlying mechanism behind NK cell dysfunction in tumor environments, and provide numerous novel therapeutic targets for tumor treatment. Strategies to enhance functional activities of NK cell have exhibited promising efficacy and favorable tolerance in clinical treatment of tumor patients, such as immune checkpoint blockade (ICB), chimeric antigen receptor NK (CAR-NK) cell, and bi/trispecific killer cell engager (BiKE/TriKE). Immunotherapy targeting NK cell provides remarkable advantages compared to T cell therapy, including a decreased rate of graft versus-host disease (GvHD) and neurotoxicity. Nevertheless, advanced details on how to support the maintenance and function of NK cell to obtain better response rate and longer duration still remain to be elucidated. This review systematically summarizes the profound role of NK cells in tumor development, highlights up-to-date advances and current challenges of therapy targeting NK cell in the clinical treatment of hematologic malignancies.

PFKFB3 in neovascular eye disease: unraveling mechanisms and exploring therapeutic strategies

BACKGROUND

Neovascular eye disease is characterized by pathological neovascularization, with clinical manifestations such as intraocular exudation, bleeding, and scar formation, ultimately leading to blindness in millions of individuals worldwide. Pathologic ocular angiogenesis often occurs in common fundus diseases including proliferative diabetic retinopathy (PDR), age-related macular degeneration (AMD), and retinopathy of prematurity (ROP). Anti-vascular endothelial growth factor (VEGF) targets the core pathology of ocular angiogenesis.

MAIN BODY

In recent years, therapies targeting metabolism to prevent angiogenesis have also rapidly developed, offering assistance to patients with a poor prognosis while receiving anti-VEGF therapy and reducing the side effects associated with long-term VEGF usage. Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key enzyme in targeted metabolism, has been shown to have great potential, with antiangiogenic effects and multiple protective effects in the treatment of neovascular eye disease. In this review, we summarize the mechanisms of common types of neovascular eye diseases; discuss the protective effect and potential mechanism of targeting PFKFB3, including the related inhibitors of PFKFB3; and look forward to the future exploration directions and therapeutic prospects of PFKFB3 in neovascular eye disease.

CONCLUSION

Neovascular eye disease, the most common and severely debilitating retinal disease, is largely incurable, necessitating the exploration of new treatment methods. PFKFB3 has been shown to possess various potential protective mechanisms in treating neovascular eye disease. With the development of several drugs targeting PFKFB3 and their gradual entry into clinical research, targeting PFKFB3-mediated glycolysis has emerged as a promising therapeutic approach for the future of neovascular eye disease.

Selective autophagy in cancer: mechanisms, therapeutic implications, and future perspectives

Eukaryotic cells engage in autophagy, an internal process of self-degradation through lysosomes. Autophagy can be classified as selective or non-selective depending on the way it chooses to degrade substrates. During the process of selective autophagy, damaged and/or redundant organelles like mitochondria, peroxisomes, ribosomes, endoplasmic reticulum (ER), lysosomes, nuclei, proteasomes, and lipid droplets are selectively recycled. Specific cargo is delivered to autophagosomes by specific receptors, isolated and engulfed. Selective autophagy dysfunction is closely linked with cancers, neurodegenerative diseases, metabolic disorders, heart failure, etc. Through reviewing latest research, this review summarized molecular markers and important signaling pathways for selective autophagy, and its significant role in cancers. Moreover, we conducted a comprehensive analysis of small-molecule compounds targeting selective autophagy for their potential application in anti-tumor therapy, elucidating the underlying mechanisms involved. This review aims to supply important scientific references and development directions for the biological mechanisms and drug discovery of anti-tumor targeting selective autophagy in the future.

Ferroptosis, Metabolic Rewiring, and Endometrial Cancer

Ferroptosis is a newly discovered form of regulated cell death. The main feature of ferroptosis is excessive membrane lipid peroxidation caused by iron-mediated chemical and enzymatic reactions. In normal cells, harmful lipid peroxides are neutralized by glutathione peroxidase 4 (GPX4). When GPX4 is inhibited, ferroptosis occurs. In mammalian cells, ferroptosis serves as a tumor suppression mechanism. Not surprisingly, in recent years, ferroptosis induction has gained attention as a potential anticancer strategy, alone or in combination with other conventional therapies. However, sensitivity to ferroptosis inducers depends on the metabolic state of the cell. Endometrial cancer (EC) is the sixth most common cancer in the world, with more than 66,000 new cases diagnosed every year. Out of all gynecological cancers, carcinogenesis of EC is mostly dependent on metabolic abnormalities. Changes in the uptake and catabolism of iron, lipids, glucose, and glutamine affect the redox capacity of EC cells and, consequently, their sensitivity to ferroptosis-inducing agents. In addition to this, in EC cells, ferroptosis-related genes are usually mutated and overexpressed, which makes ferroptosis a promising target for EC prediction, diagnosis, and therapy. However, for a successful application of ferroptosis, the connection between metabolic rewiring and ferroptosis in EC needs to be deciphered, which is the focus of this review.

Research progress on the mechanism of glycolysis in ovarian cancer

Glycolysis is the preferred energy metabolism pathway in cancer cells even when the oxygen content is sufficient. Through glycolysis, cancer cells convert glucose into pyruvic acid and then lactate to rapidly produce energy and promote cancer progression. Changes in glycolysis activity play a crucial role in the biosynthesis and energy requirements of cancer cells needed to maintain growth and metastasis. This review focuses on ovarian cancer and the significance of key rate-limiting enzymes (hexokinase, phosphofructokinase, and pyruvate kinase, related signaling pathways (PI3K-AKT, Wnt, MAPK, AMPK), transcription regulators (HIF-1a), and non-coding RNA in the glycolytic pathway. Understanding the relationship between glycolysis and these different mechanisms may provide new opportunities for the future treatment of ovarian cancer.

MiR-206 inhibits estrogen signaling and ovarian cancer cell migration without affecting GPER

AIMS

Estrogen-regulated pathways are involved in the etiology and progression of epithelial ovarian cancer (EOC), but the relative contribution of estrogen receptor isoforms is unclear. Only a subset of patients responds to antiestrogens including tamoxifen. Based on our previous evidence that miR-206 behaves as an oncosuppressor in EOC, we hypothesized that miR-206 would interfere with G protein-coupled estrogen receptor (GPER)-mediated signaling and cell motility.

MAIN METHODS

PFKFB3 and FAK proteins from OC cells challenged with selective estrogen receptor agonist and antagonist were measured by Western blotting. Cell proliferation and motility were analyzed by MTT and Boyden chamber, respectively. Estrogen-dependent cells were transfected with miR-206 mimic or control using Lipofectamine.

KEY FINDINGS

The migration of SKOV3 and OVCAR5 cells significantly increased following treatment with 17β-estradiol (E2) and the selective GPER agonist G1. However, tamoxifen failed to inhibit E2 effect and even promoted SKOV3 cell migration. Estrogen receptor ligands did not affect SKOV3 proliferation. The GPER antagonist G15 significantly prevented E2-mediated upregulation of PFKFB3 expression, while G1 concentration-dependently upregulated PFKFB3 levels. Consistent with the functional link between PFKFB3 and FAK activation, E2 and G1 increased FAK phosphorylation at Tyr397. Transfection with miR-206 abolished estrogen-induced EOC migration and down-regulated PFKFB3 protein levels. Notably, miR-206 transfection reduced ERα protein abundance, whereas GPER amount was unchanged.

SIGNIFICANCE

By blocking estrogen signaling and G1-induced EOC cell invasiveness with no direct interference with GPER levels, miR-206 mimics have the potential to act as pathway-selective antagonists and deserve further testing as RNA therapeutics in estrogen-dependent EOC.

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.

Post-Transcriptional and Epigenetic Regulation of Estrogen Signaling

Post-translational and epigenetic regulation are important mechanisms controlling functions of genes and proteins. Although the "classic" estrogen receptors (ERs) have been acknowledged to function in mediating estrogen effects via transcriptional mechanisms, estrogenic agents modulate the turnover of several proteins via post-transcriptional and post-translational pathways including epigenetics. For instance, the metabolic and angiogenic action of G-protein coupled estrogen receptor (GPER) in vascular endothelial cells has been recently elucidated. By interacting with GPER, 17β-estradiol and the GPER agonist G1 enhance endothelial stability of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and capillary tube formation by increasing ubiquitin-specific peptidase 19 levels, thereby reducing PFKFB3 ubiquitination and proteasomal degradation. In addition to ligands, the functional expression and trafficking of ERs can be modulated by post-translational modification, including palmitoylation. MicroRNAs (miRNAs), the most abundant form of endogenous small RNAs in humans, regulate multiple target genes and are at the center of the multi-target regulatory network. This review also discusses the emerging evidence of how miRNAs affect glycolytic metabolism in cancer, as well as their regulation by estrogens. Restoring dysregulated miRNA expression represents a promising strategy to counteract the progression of cancer and other disease conditions. Accordingly, estrogen post-transcriptional regulatory and epigenetic mechanisms represent novel targets for pharmacological and nonpharmacological intervention for the treatment and prevention of hormone-sensitive noncommunicable diseases, including estrogen-sensitive cancers of the reproductive system in women. SIGNIFICANCE STATEMENT: The effects of estrogen are mediated by several mechanisms that are not limited to the transcriptional regulation of target genes. Slowing down the turnover of master regulators of metabolism by estrogens allows cells to rapidly adapt to environmental cues. Identification of estrogen-targeted microRNAs may lead to the development of novel RNA therapeutics that disrupt pathological angiogenesis in estrogen-dependent cancers.

m6A-regulated tumor glycolysis: new advances in epigenetics and metabolism

Glycolytic reprogramming is one of the most important features of cancer and plays an integral role in the progression of cancer. In cancer cells, changes in glucose metabolism meet the needs of self-proliferation, angiogenesis and lymphangiogenesis, metastasis, and also affect the immune escape, prognosis evaluation and therapeutic effect of cancer. The n6-methyladenosine (m6A) modification of RNA is widespread in eukaryotic cells. Dynamic and reversible m6A modifications are widely involved in the regulation of cancer stem cell renewal and differentiation, tumor therapy resistance, tumor microenvironment, tumor immune escape, and tumor metabolism. Lately, more and more evidences show that m6A modification can affect the glycolysis process of tumors in a variety of ways to regulate the biological behavior of tumors. In this review, we discussed the role of glycolysis in tumor genesis and development, and elaborated in detail the profound impact of m6A modification on different tumor by regulating glycolysis. We believe that m6A modified glycolysis has great significance and potential for tumor treatment.

Small molecule inhibitors for cancer metabolism: promising prospects to be explored

BACKGROUND

Abnormal metabolism is the main hallmark of cancer, and cancer metabolism plays an important role in tumorigenesis, metastasis, and drug resistance. Therefore, studying the changes of tumor metabolic pathways is beneficial to find targets for the treatment of cancer diseases. The success of metabolism-targeted chemotherapy suggests that cancer metabolism research will provide potential new targets for the treatment of malignant tumors.

PURPOSE

The aim of this study was to systemically review recent research findings on targeted inhibitors of tumor metabolism. In addition, we summarized new insights into tumor metabolic reprogramming and discussed how to guide the exploration of new strategies for cancer-targeted therapy.

CONCLUSION

Cancer cells have shown various altered metabolic pathways, providing sufficient fuel for their survival. The combination of these pathways is considered to be a more useful method for screening multilateral pathways. Better understanding of the clinical research progress of small molecule inhibitors of potential targets of tumor metabolism will help to explore more effective cancer treatment strategies.

Lipid droplets: a cellular organelle vital in cancer cells

Lipid droplets (LDs) are cellular organelles comprising a core of neutral lipids (glycerides, sterols) encased within a single phospholipid membrane, responsible for storing surplus lipids and furnishing cellular energy. LDs engage in lipid synthesis, catabolism, and transport processes by interacting with other organelles (e.g., endoplasmic reticulum, mitochondria), and they play critical roles in regulating cellular stress and immunity. Recent research has uncovered that an elevated number of LDs is a hallmark of cancer cells, attributable to their enhanced lipid uptake and synthesis capacity, with lipids stored as LDs. Depletion of LDs in cancer cells induces apoptosis, prompting the emergence of small molecule antitumor drugs targeting LDs or key factors (e.g., FASN, SCD1) within the lipid synthesis pathway. Advancements in LD isolation and artificial synthesis have demonstrated their potential applicability in antitumor research. LDs extracted from murine adipose tissue and incubated with lipophilic antitumor drugs yield drug-coated LDs, which promote apoptosis in cancer cells. Furthermore, LDs have been employed as biological lenses to augment the resolution of subcellular structures (microfilaments, microtubules), facilitating the observation of intricate structures within thicker cells, including cancer cells. This review delineates the functional and metabolic mechanisms of LDs in cancer cells and encapsulates recent progress in LD-centered antitumor research, offering novel insights for tumor diagnosis and treatment.

Oncogenic viruses and host lipid metabolism: a new perspective

As noncellular organisms, viruses do not have their own metabolism and rely on the metabolism of host cells to provide energy and metabolic substances for their life cycles. Increasing evidence suggests that host cells infected with oncogenic viruses have dramatically altered metabolic requirements and that oncogenic viruses produce substances used for viral replication and virion production by altering host cell metabolism. We focused on the processes by which oncogenic viruses manipulate host lipid metabolism and the lipid metabolism disorders that occur in oncogenic virus-associated diseases. A deeper understanding of viral infections that cause changes in host lipid metabolism could help with the development of new antiviral agents as well as potential new therapeutic targets.

Metabolic dependencies and targets in ovarian cancer

Reprogramming of cellular metabolism is a hallmark of cancer. Cancer cells undergo metabolic adaptations to maintain tumorigenicity and survive under the attack of immune cells and chemotherapy in the tumor microenvironment. Metabolic alterations in ovarian cancer in part overlap with findings from other solid tumors and in part reflect unique traits. Altered metabolic pathways not only facilitate ovarian cancer cells' survival and proliferation but also endow them to metastasize, acquire resistance to chemotherapy, maintain cancer stem cell phenotype and escape the effects of anti-tumor immune defense. In this review, we comprehensively review the metabolic signatures of ovarian cancer and their impact on cancer initiation, progression, and resistance to treatment. We highlight novel therapeutic strategies targeting metabolic pathways under development.

Deregulated Metabolic Pathways in Ovarian Cancer: Cause and Consequence

Ovarian cancers are tumors that originate from the different cells of the ovary and account for almost 4% of all the cancers in women globally. More than 30 types of tumors have been identified based on the cellular origins. Epithelial ovarian cancer (EOC) is the most common and lethal type of ovarian cancer which can be further divided into high-grade serous, low-grade serous, endometrioid, clear cell, and mucinous carcinoma. Ovarian carcinogenesis has been long attributed to endometriosis which is a chronic inflammation of the reproductive tract leading to progressive accumulation of mutations. Due to the advent of multi-omics datasets, the consequences of somatic mutations and their role in altered tumor metabolism has been well elucidated. Several oncogenes and tumor suppressor genes have been implicated in the progression of ovarian cancer. In this review, we highlight the genetic alterations undergone by the key oncogenes and tumor suppressor genes responsible for the development of ovarian cancer. We also summarize the role of these oncogenes and tumor suppressor genes and their association with a deregulated network of fatty acid, glycolysis, tricarboxylic acid and amino acid metabolism in ovarian cancers. Identification of genomic and metabolic circuits will be useful in clinical stratification of patients with complex etiologies and in identifying drug targets for personalized therapies against cancer.

The Role of Reprogrammed Glucose Metabolism in Cancer

Cancer cells reprogram their metabolism to meet biosynthetic needs and to adapt to various microenvironments. Accelerated glycolysis offers proliferative benefits for malignant cells by generating glycolytic products that move into branched pathways to synthesize proteins, fatty acids, nucleotides, and lipids. Notably, reprogrammed glucose metabolism and its associated events support the hallmark features of cancer such as sustained cell proliferation, hijacked apoptosis, invasion, metastasis, and angiogenesis. Overproduced enzymes involved in the committed steps of glycolysis (hexokinase, phosphofructokinase-1, and pyruvate kinase) are promising pharmacological targets for cancer therapeutics. In this review, we summarize the role of reprogrammed glucose metabolism in cancer cells and how it can be manipulated for anti-cancer strategies.

SQSTM1, lipid droplets and current state of their lipophagy affairs

SQSTM1/p62 (sequestosome 1) is a well-established indicator of macroautophagic/autophagic flux. It was initially characterized as the ubiquitin-binding autophagic receptor in aggrephagy, the selective autophagy of ubiquitinated protein aggregates. Recently, several studies correlated its levels with the abundance of intracellular lipid droplets (LDs). In the absence of a bona fide receptor for the selective autophagy of LDs (lipophagy), a few studies demonstrated the role of SQSTM1 in lipophagy. Our analysis of these studies shows that SQSTM1 colocalizes with LDs, bridges them with phagophores, is co-degraded with them in the lysosomes, and affects LD abundance in a variety of cells and under diverse experimental conditions. Although only one study reported all these functions together, the overwhelming and complementary evidence from other studies suggests that the role of SQSTM1 in lipophagy via tagging, movement, aggregation/clustering and sequestration of LDs is rather a common phenomenon in mammalian cells. As ubiquitination of the LD-associated proteins under stress conditions is increasingly recognized as another common phenomenon, some other ubiquitin-binding autophagic receptors, such as NBR1 and OPTN, might soon join SQSTM1 on a list of the non-exclusive lipophagy receptors.Abbreviations: LD: lipid droplet; LIR: LC3-interacting region; PAT: Perilipin, ADRP and TIP47 domain; SAR: selective autophagy receptor.

Modulating Glycolysis to Improve Cancer Therapy

Cancer cells undergo metabolic reprogramming and switch to a 'glycolysis-dominant' metabolic profile to promote their survival and meet their requirements for energy and macromolecules. This phenomenon, also known as the 'Warburg effect,' provides a survival advantage to the cancer cells and make the tumor environment more pro-cancerous. Additionally, the increased glycolytic dependence also promotes chemo/radio resistance. A similar switch to a glycolytic metabolic profile is also shown by the immune cells in the tumor microenvironment, inducing a competition between the cancer cells and the tumor-infiltrating cells over nutrients. Several recent studies have shown that targeting the enhanced glycolysis in cancer cells is a promising strategy to make them more susceptible to treatment with other conventional treatment modalities, including chemotherapy, radiotherapy, hormonal therapy, immunotherapy, and photodynamic therapy. Although several targeting strategies have been developed and several of them are in different stages of pre-clinical and clinical evaluation, there is still a lack of effective strategies to specifically target cancer cell glycolysis to improve treatment efficacy. Herein, we have reviewed our current understanding of the role of metabolic reprogramming in cancer cells and how targeting this phenomenon could be a potential strategy to improve the efficacy of conventional cancer therapy.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Synthesis of Glycolysis Inhibitor PFK15 and Its Synergistic Action with an Approved Multikinase Antiangiogenic Drug on Human Endothelial Cell Migration and Proliferation

Activated endothelial, immune, and cancer cells prefer glycolysis to obtain energy for their proliferation and migration. Therefore, the blocking of glycolysis can be a promising strategy against cancer and autoimmune disease progression. Inactivation of the glycolytic enzyme PFKFB3 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase) suppresses glycolysis level and contributes to decreased proliferation and migration of cancer (tumorigenesis) and endothelial (angiogenesis) cells. Recently, several glycolysis inhibitors have been developed, among them (E)-1-(pyridin-4-yl)-3-(quinolin-2-yl)prop-2-en-1-one (PFK15) that is considered as one of the most promising. It is known that PFK15 decreases glucose uptake into the endothelial cells and efficiently blocks pathological angiogenesis. However, no study has described sufficiently PFK15 synthesis enabling its general availability. In this paper we provide all necessary details for PFK15 preparation and its advanced characterization. On the other hand, there are known tyrosine kinase inhibitors (e.g., sunitinib), that affect additional molecular targets and efficiently block angiogenesis. From a biological point of view, we have studied and proved the synergistic inhibitory effect by simultaneous administration of glycolysis inhibitor PFK15 and multikinase inhibitor sunitinib on the proliferation and migration of HUVEC. Our results suggest that suppressing the glycolytic activity of endothelial cells in combination with growth factor receptor blocking can be a promising antiangiogenic treatment.

PFKFB3 works on the FAK-STAT3-SOX2 axis to regulate the stemness in MPM

BACKGROUND

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm and often acquires chemoresistance by increasing stemness in tumour tissue, thereby generating cancer stem cells (CSCs). CSCs escape treatment by deploying metabolic pathways to trigger dormancy or proliferation, also gaining the ability to exit and re-enter the cell cycle to hide their cellular identity.

METHODS

We employed various cellular and biochemical assays to identify the role of the glycolytic enzyme PFKFB3, by knocking it down and pharmacologically inhibiting it with PFK158, to determine its anticancer effects in vitro and in vivo by targeting the CSC population in MPM.

RESULTS

Here, we have identified PFKFB3 as a strategic player to target the CSC population in MPM and demonstrated that both pharmacologic (PFK158) and genetic inhibition of PFKFB3 destroy the FAK-Stat3-SOX2 nexus resulting in a decline in conspicuous stem cell markers viz. ALDH, CD133, CD44, SOX2. Inhibition of PFKFB3 accumulates p21 and p27 in the nucleus by decreasing SKP2. Lastly, PFK158 diminishes tumour-initiating cells (TICs) mediated MPM xenograft in vivo.

CONCLUSIONS

This study confers a comprehensive and mechanistic function of PFKFB3 in CSC maintenance that may foster exceptional opportunities for targeted small molecule blockade of the TICs in MPM.

Targeting Glucose Metabolism Enzymes in Cancer Treatment: Current and Emerging Strategies

Simple Summary

Reprogramming of glucose metabolism is a hallmark of cancer and can be targeted by therapeutic agents. Some metabolism regulators, such as ivosidenib and enasidenib, have been approved for cancer treatment. Currently, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Furthermore, some natural products have shown efficacy in killing tumor cells by regulating glucose metabolism, offering novel therapeutic opportunities in cancer. However, most of them have failed to be translated into clinical applications due to low selectivity, high toxicity, and side effects. Recent studies suggest that combining glucose metabolism modulators with chemotherapeutic drugs, immunotherapeutic drugs, and other conventional anticancer drugs may be a future direction for cancer treatment.

Abstract

Reprogramming of glucose metabolism provides sufficient energy and raw materials for the proliferation, metastasis, and immune escape of cancer cells, which is enabled by glucose metabolism-related enzymes that are abundantly expressed in a broad range of cancers. Therefore, targeting glucose metabolism enzymes has emerged as a promising strategy for anticancer drug development. Although several glucose metabolism modulators have been approved for cancer treatment in recent years, some limitations exist, such as a short half-life, poor solubility, and numerous adverse effects. With the rapid development of medicinal chemicals, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Additionally, several studies have found that some natural products can suppress cancer progression by regulating glucose metabolism enzymes. In this review, we summarize the mechanisms underlying the reprogramming of glucose metabolism and present enzymes that could serve as therapeutic targets. In addition, we systematically review the existing drugs targeting glucose metabolism enzymes, including small-molecule modulators and natural products. Finally, the opportunities and challenges for glucose metabolism enzyme-targeted anticancer drugs are also discussed. In conclusion, combining glucose metabolism modulators with conventional anticancer drugs may be a promising cancer treatment strategy.

Emerging Roles of Lipophagy in Cancer Metastasis

Simple Summary

Metastasis is the main cause of death in patients with malignant tumors worldwide. Mounting evidence suggests lipid droplet metabolism is involved in the process of metastasis. As a mechanism to selectively degrade lipid droplets, the current research on lipophagy and tumor metastasis is quite limited. This review summarizes the crosstalk among lipophagy, tumor lipid metabolism and cancer metastasis, which will provide a new reference for the development of effective targeted drugs.

Abstract

Obesity is a prominent risk factor for certain types of tumor progression. Adipocytes within tumor stroma contribute to reshaping tumor microenvironment (TME) and the metabolism and metastasis of tumors through the production of cytokines and adipokines. However, the crosstalk between adipocytes and tumor cells remains a major gap in this field. Known as a subtype of selective autophagy, lipophagy is thought to contribute to lipid metabolism by breaking down intracellular lipid droplets (LDs) and generating free fatty acids (FAs). The metastatic potential of cancer cells closely correlates with the lipid degradation mechanisms, which are required for energy generation, signal transduction, and biosynthesis of membranes. Here, we discuss the recent advance in the understanding of lipophagy with tumor lipid metabolism and review current studies on the roles of lipoghagy in the metastasis of certain human malignancies. Additionally, the novel candidate drugs targeting lipophagy are integrated for effective treatment strategies.

Integration of clinical and transcriptomics reveals programming of the lipid metabolism in gastric cancer

Lipid metabolism has a profound impact on gastric cancer (GC) progression and is a newly targetable vulnerability for cancer therapy. Given the importance of lipids in cancer cellular processes, in this study we employed lipidomic clinical and transcriptomic data to connect the variations of lipid metabolism changes of GC. We constructed a clinical nomogram based on the lipid factors and other clinical items. Then by using multi-omics techniques, we established a lipid-related gene signature for individualized prognosis prediction in patients with GC. Moreover, a total of 1357 GC cases were then applied to evaluate the robustness of this model. WGCNA was used to identify co-expression modules and enriched genes associated with GC lipid metabolism. The role of key genes ACLY in GC was further investigated. The prognostic value of the lipgenesis signature was analyzed using Cox regression model, and clinical nomogram was established. Among them, we observed overexpression of ACLY significantly increased the levels of intracellular free fatty acid and triglyceride, and activated AKT/mTOR pathway to promote cancer development. In conclusion, our findings revealed that GC exhibited a reprogramming of lipid metabolism in association with an altered expression of associated genes. Among them, ACLY significantly promoted GC lipid metabolism and increased cancer cell proliferation, suggesting that this pathway can be targetable as a metabolic vulnerability in future GC therapy.

Metabolic Reprogramming in Hematologic Malignancies: Advances and Clinical Perspectives

Metabolic reprogramming is a hallmark of cancer progression. Metabolic activity supports tumorigenesis and tumor progression, allowing cells to uptake essential nutrients from the environment and use the nutrients to maintain viability and support proliferation. The metabolic pathways of malignant cells are altered to accommodate increased demand for energy, reducing equivalents, and biosynthetic precursors. Activated oncogenes coordinate with altered metabolism to control cell-autonomous pathways, which can lead to tumorigenesis when abnormalities accumulate. Clinical and preclinical studies have shown that targeting metabolic features of hematologic malignancies is an appealing therapeutic approach. This review provides a comprehensive overview of the mechanisms of metabolic reprogramming in hematologic malignancies and potential therapeutic strategies to target cancer metabolism.

Link of sorafenib resistance with the tumor microenvironment in hepatocellular carcinoma: Mechanistic insights

Sorafenib, a multi-kinase inhibitor with antiangiogenic, antiproliferative, and proapoptotic properties, is the first-line treatment for patients with late-stage hepatocellular carcinoma (HCC). However, the therapeutic effect remains limited due to sorafenib resistance. Only about 30% of HCC patients respond well to the treatment, and the resistance almost inevitably happens within 6 months. Thus, it is critical to elucidate the underlying mechanisms and identify effective approaches to improve the therapeutic outcome. According to recent studies, tumor microenvironment (TME) and immune escape play critical roles in tumor occurrence, metastasis and anti-cancer drug resistance. The relevant mechanisms were focusing on hypoxia, tumor-associated immune-suppressive cells, and immunosuppressive molecules. In this review, we focus on sorafenib resistance and its relationship with liver cancer immune microenvironment, highlighting the importance of breaking sorafenib resistance in HCC.

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.

PFKFB3 regulates cancer stemness through the hippo pathway in small cell lung carcinoma

PFKFB3 (6-phosphofructo-2-kinase) is the rate-limiting enzyme of glycolysis and is overexpressed in several human cancers that are associated with poor prognosis. High PFKFB3 expression in cancer stem cells promotes glycolysis and survival in the tumor microenvironment. Inhibition of PFKFB3 by the glycolytic inhibitor PFK158 and by shRNA stable knockdown in small cell lung carcinoma (SCLC) cell lines inhibited glycolysis, proliferation, spheroid formation, and the expression of cancer stem cell markers CD133, Aldh1, CD44, Sox2, and ABCG2. These factors are also associated with chemotherapy resistance. We found that PFK158 treatment and PFKFB3 knockdown enhanced the ABCG2-interacting drugs doxorubicin, etoposide, and 5-fluorouracil in reducing cell viability under conditions of enriched cancer stem cells (CSC). Additionally, PFKFB3 inhibition attenuated the invasion/migration of SCLC cells by downregulating YAP/TAZ signaling while increasing pLATS1 via activation of pMST1 and NF2 and by reducing the mesenchymal protein expression. PFKFB3 knockdown and PFK158 treatment in a H1048 SCLC cancer stem cell-enriched mouse xenograft model showed significant reduction in tumor growth and weight with reduced expression of cancer stem cell markers, ABCG2, and YAP/TAZ. Our findings identify that PFKFB3 is a novel target to regulate cancer stem cells and its associated therapeutic resistance markers YAP/TAZ and ABCG2 in SCLC models.

The strategic roles of four enzymes in the interconnection between metabolism and oncogene activation in non-small cell lung cancer: Therapeutic implications

NSCLC is the leading cause of cancer mortality and represents a major challenge in cancer therapy. Intrinsic and acquired anticancer drug resistance are promoted by hypoxia and HIF-1α. Moreover, chemoresistance is sustained by the activation of key signaling pathways (such as RAS and its well-known downstream targets PI3K/AKT and MAPK) and several mutated oncogenes (including KRAS and EGFR among others). In this review, we highlight how these oncogenic factors are interconnected with cell metabolism (aerobic glycolysis, glutaminolysis and lipid synthesis). Also, we stress the key role of four metabolic enzymes (PFK1, dimeric-PKM2, GLS1 and ACLY), which promote the activation of these oncogenic pathways in a positive feedback loop. These four tenors orchestrating the coordination of metabolism and oncogenic pathways could be key druggable targets for specific inhibition. Since PFK1 appears as the first tenor of this orchestra, its inhibition (and/or that of its main activator PFK2/PFKFB3) could be an efficacious strategy against NSCLC. Citrate is a potent physiologic inhibitor of both PFK1 and PFKFB3, and NSCLC cells seem to maintain a low citrate level to sustain aerobic glycolysis and the PFK1/PI3K/EGFR axis. Awaiting the development of specific non-toxic inhibitors of PFK1 and PFK2/PFKFB3, we propose to test strategies increasing citrate levels in NSCLC tumors to disrupt this interconnection. This could be attempted by evaluating inhibitors of the citrate-consuming enzyme ACLY and/or by direct administration of citrate at high doses. In preclinical models, this "citrate strategy" efficiently inhibits PFK1/PFK2, HIF-1α, and IGFR/PI3K/AKT axes. It also blocks tumor growth in RAS-driven lung cancer models, reversing dedifferentiation, promoting T lymphocytes tumor infiltration, and increasing sensitivity to cytotoxic drugs.

How Phosphofructokinase-1 Promotes PI3K and YAP/TAZ in Cancer: Therapeutic Perspectives

Simple Summary

We propose that PFK1 promotes a positive feedback loop with PI3K/AKT and YAP/TAZ signaling pathways in cancer cells. Therefore, targeting PFK1 (or its product F-1,6-BP) could improve the efficacy of PI3K and YAP/TAZ inhibitors currently tested in clinical trials. To this aim, we suggest the use of citrate, which is a physiologic and potent inhibitor of PFK1.

Abstract

PI3K/AKT is one of the most frequently altered signaling pathways in human cancers, supporting the activation of many proteins sustaining cell metabolism, proliferation, and aggressiveness. Another important pathway frequently altered in cancer cells is the one regulating the YAP/TAZ transcriptional coactivators, which promote the expression of genes sustaining aerobic glycolysis (such as WNT, MYC, HIF-1), EMT, and drug resistance. Of note, the PI3K/AKT pathway can also regulate the YAP/TAZ one. Unfortunately, although PI3K and YAP inhibitors are currently tested in highly resistant cancers (both solid and hematologic ones), several resistance mechanisms may arise. Resistance mechanisms to PI3K inhibitors may involve the stimulation of alternative pathways (such as RAS, HER, IGFR/AKT), the inactivation of PTEN (the physiologic inhibitor of PI3K), and the expression of anti-apoptotic Bcl-xL and MCL1 proteins. Therefore, it is important to improve current therapeutic strategies to overcome these limitations. Here, we want to highlight how the glycolytic enzyme PFK1 (and its product F-1,6-BP) promotes the activation of both PI3K/AKT and YAP/TAZ pathways by several direct and indirect mechanisms. In turn, PI3K/AKT and YAP/TAZ can promote PFK1 activity and F-1,6-BP production in a positive feedback loop, thus sustaining the Warburg effect and drug resistance. Thus, we propose that the inhibition of PFK1 (and of its key activator PFK2/PFKFB3) could potentiate the sensitivity to PI3K and YAP inhibitors currently tested. Awaiting the development of non-toxic inhibitors of these enzymes, we propose to test the administration of citrate at a high dosage, because citrate is a physiologic inhibitor of both PFK1 and PFK2/PFKFB3. Consistently, in various cultured cancer cells (including melanoma, sarcoma, hematologic, and epithelial cancer cells), this “citrate strategy” efficiently inhibits the IGFR1/AKT pathway, promotes PTEN activity, reduces Bcl-xL and MCL1 expression, and increases sensitivity to standard chemotherapy. It also inhibits the development of sarcoma, pancreatic, mammary HER⁺ and lung RAS-driven tumors in mice without apparent toxicities.

Novel Insights on Lipid Metabolism Alterations in Drug Resistance in Cancer

Chemotherapy is one of the primary treatments for most human cancers. Despite great progress in cancer therapeutics, chemotherapy continues to be important for improving the survival of cancer patients, especially for those who has unresectable metastatic tumors or fail to respond to immunotherapy. However, intrinsic or acquired chemoresistance results in tumor recurrence, which remains a major obstacle in anti-cancer treatment. The high prevalence of chemoresistant cancer makes it urgent to deepen our understanding on chemoresistance mechanisms and to develop novel therapeutic strategies. Multiple mechanisms, including drug efflux, enhanced DNA damage reparability, increased detoxifying enzymes levels, presence of cancer stem cells (CSCs), epithelial mesenchymal transition (EMT), autophagy, ferroptosis and resistance to apoptosis, underlie the development of chemoresistance. Recently, accumulating evidence suggests that lipid metabolism alteration is closely related to drug resistance in tumor. Targeting lipid metabolism in combination with traditional chemotherapeutic drugs is a promising strategy to overcome drug resistance. Therefore, this review compiles the current knowledge about aberrant lipid metabolism in chemoresistant cancer, mainly focusing on aberrant fatty acid metabolism, and presents novel therapeutic strategies targeting altered lipid metabolism to overcome chemoresistance in cancer.

The role of PFKFB3 in maintaining colorectal cancer cell proliferation and stemness

Since generally confronting with the hypoxic and stressful microenvironment, cancer cells alter their glucose metabolism pattern to glycolysis to sustain the continuous proliferation and vigorous biological activities. Bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) isoform 3 (PFKFB3) functions as an effectively modulator of glycolysis and also participates in regulating angiogenesis, cell death and cell stemness. Meanwhile, PFKFB3 is highly expressed in a variety of cancer cells, and can be activated by several regulatory factors, such as hypoxia, inflammation and cellular signals. In colorectal cancer (CRC) cells, PFKFB3 not only has the property of high expression, but also probably relate to inflammation-cancer transformation. Recent studies indicate that PFKFB3 is involved in chemoradiotherapy resistance as well, such as breast cancer, endometrial cancer and CRC. Cancer stem cells (CSCs) are self-renewable cell types that contribute to oncogenesis, metastasis and relapse. Several studies indicate that CSCs utilize glycolysis to fulfill their energetic and biosynthetic demands in order to maintain rapid proliferation and adapt to the tumor microenvironment changes. In addition, elevated PFKFB3 has been reported to correlate with self-renewal and metastatic outgrowth in numerous kinds of CSCs. This review summarizes our current understanding of PFKFB3 roles in modulating cancer metabolism to maintain cell proliferation and stemness, and discusses its feasibility as a potential target for the discovery of antineoplastic agents, especially in CRC.

Metabolic Reprogramming and Lipophagy Mediates Survival of Ascites Derived Metastatic Ovarian Cancer Cells

OBJECTIVE

The study was aimed at understanding the survival of metastatic ovarian cancer spheroids in the malignant ascites microenvironment.

METHODS

All the assays were performed using aseptically collected patient samples. The cells were characterized for the expression of ovarian and cancer stem cell markers using immunocytochemistry. The presence of lipid in the primary metastatic cancer spheroids were confirmed by neutral fat staining using Oil Red-O and transmission electron microscopy. The mRNA expression of autophagy and lipid metabolism genes was analyzed using RT-PCR. The lipid content was analyzed using lipidomics analysis. Etomoxir and chloroquine were used to study the effect of inhibition of autophagy in the metastatic cells. The data were analyzed using appropriate statistical tools and a p-value <0.05 was considered to be statistically significant.

RESULTS

Metastatic ovarian cancer spheroids exhibit cancer stem like properties and undergo a metabolic reprogramming when they disseminate from the primary tumor. We report here the accumulation of numerous cytoplasmic lipid droplets and lipophagic vesicles in the metastatic cells in contrast to their primary tumors. In addition we also report that these cells depend on lipophagy for the utilization of lipids rather than the conventional lipolytic pathway. The lipidomics analysis data reveals that the metastatic cells possess high levels of unsaturated fatty acids. We have also reported the occurrence of distinct accumulation of multiple nuclei in the patient derived metastatic cells. Inhibition of beta-oxidation and autophagic machinery using etomoxir and chloroquine resulted in cell death suggesting a potential mode to suppress metastatic cancer cells.

CONCLUSION

Metabolic reprogramming is a characteristic feature of the metastatic ovarian cancer cells that are persisting in the malignant ascites. Targeting of the metastatic by gaining an insight into the various metabolic and molecular changes that occur in the metastatic niche provides a promising therapeutic approach in management of the disease.

Treatment against glucose-dependent cancers through metabolic PFKFB3 targeting of glycolytic flux

Reprogrammed metabolism and high energy demand are well-established properties of cancer cells that enable tumor growth. Glycolysis is a primary metabolic pathway that supplies this increased energy demand, leading to a high rate of glycolytic flux and a greater dependence on glucose in tumor cells. Finding safe and effective means to control glycolytic flux and curb cancer cell proliferation has gained increasing interest in recent years. A critical step in glycolysis is controlled by the enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), which converts fructose 6-phosphate (F6P) to fructose 2,6-bisphosphate (F2,6BP). F2,6BP allosterically activates the rate-limiting step of glycolysis catalyzed by PFK1 enzyme. PFKFB3 is often overexpressed in many human cancers including pancreatic, colon, prostate, and breast cancer. Hence, PFKFB3 has gained increased interest as a compelling therapeutic target. In this review, we summarize and discuss the current knowledge of PFKFB3 functions, its role in cellular pathways and cancer development, its transcriptional and post-translational activity regulation, and the multiple pharmacologic inhibitors that have been used to block PFKFB3 activity in cancer cells. While much remains to be learned, PFKFB3 continues to hold great promise as an important therapeutic target either as a single agent or in combination with current interventions for breast and other cancers.

Tumor Cell Glycolysis—At the Crossroad of Epithelial–Mesenchymal Transition and Autophagy

Upregulation of glycolysis, induction of epithelial–mesenchymal transition (EMT) and macroautophagy (hereafter autophagy), are phenotypic changes that occur in tumor cells, in response to similar stimuli, either tumor cell-autonomous or from the tumor microenvironment. Available evidence, herein reviewed, suggests that glycolysis can play a causative role in the induction of EMT and autophagy in tumor cells. Thus, glycolysis has been shown to induce EMT and either induce or inhibit autophagy. Glycolysis-induced autophagy occurs both in the presence (glucose starvation) or absence (glucose sufficiency) of metabolic stress. In order to explain these, in part, contradictory experimental observations, we propose that in the presence of stimuli, tumor cells respond by upregulating glycolysis, which will then induce EMT and inhibit autophagy. In the presence of stimuli and glucose starvation, upregulated glycolysis leads to adenosine monophosphate-activated protein kinase (AMPK) activation and autophagy induction. In the presence of stimuli and glucose sufficiency, upregulated glycolytic enzymes (e.g., aldolase or glyceraldehyde 3-phosphate dehydrogenase) or decreased levels of glycolytic metabolites (e.g., dihydroxyacetone phosphate) may mimic a situation of metabolic stress (herein referred to as “pseudostarvation”), leading, directly or indirectly, to AMPK activation and autophagy induction. We also discuss possible mechanisms, whereby glycolysis can induce a mixed mesenchymal/autophagic phenotype in tumor cells. Subsequently, we address unresolved problems in this field and possible therapeutic consequences.

Is Autophagy Always a Barrier to Cisplatin Therapy?

Cisplatin has long been a first-line chemotherapeutic agent in the treatment of cancer, largely for solid tumors. During the course of the past two decades, autophagy has been identified in response to cancer treatments and almost uniformly detected in studies involving cisplatin. There has been increasing recognition of autophagy as a critical factor affecting tumor cell death and tumor chemoresistance. In this review and commentary, we introduce four mechanisms of resistance to cisplatin followed by a discussion of the factors that affect the role of autophagy in cisplatin-sensitive and resistant cells and explore the two-sided outcomes that occur when autophagy inhibitors are combined with cisplatin. Our goal is to analyze the potential for the combinatorial use of cisplatin and autophagy inhibitors in the clinic.

The Fibrillin-1/VEGFR2/STAT2 signaling axis promotes chemoresistance via modulating glycolysis and angiogenesis in ovarian cancer organoids and cells

Background

Chemotherapy resistance is a primary reason of ovarian cancer therapy failure; hence it is important to investigate the underlying mechanisms of chemotherapy resistance and develop novel potential therapeutic targets.

Methods

RNA sequencing of cisplatin‐resistant and ‐sensitive (chemoresistant and chemosensitive, respectively) ovarian cancer organoids was performed, followed by detection of the expression level of fibrillin‐1 (FBN1) in organoids and clinical specimens of ovarian cancer. Subsequently, glucose metabolism, angiogenesis, and chemosensitivity were analyzed in structural glycoprotein FBN1‐knockout cisplatin‐resistant ovarian cancer organoids and cell lines. To gain insights into the specific functions and mechanisms of action of FBN1 in ovarian cancer, immunoprecipitation, silver nitrate staining, mass spectrometry, immunofluorescence, Western blotting, and Fӧrster resonance energy transfer‐fluorescence lifetime imaging analyses were performed, followed by in vivo assays using vertebrate model systems of nude mice and zebrafish.

Results

FBN1 expression was significantly enhanced in cisplatin‐resistant ovarian cancer organoids and tissues, indicating that FBN1 might be a key factor in chemoresistance of ovarian cancer. We also discovered that FBN1 sustained the energy stress and induced angiogenesis in vitro and in vivo, which promoted the cisplatin‐resistance of ovarian cancer. Knockout of FBN1 combined with treatment of the antiangiogenic drug apatinib improved the cisplatin‐sensitivity of ovarian cancer cells. Mechanistically, FBN1 mediated the phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) at the Tyr1054 residue, which activated its downstream focal adhesion kinase (FAK)/protein kinase B (PKB or AKT) pathway, induced the phosphorylation of signal transducer and activator of transcription 2 (STAT2) at the tyrosine residue 690 (Tyr690), promoted the nuclear translocation of STAT2, and ultimately altered the expression of genes associated with STAT2‐mediated angiogenesis and glycolysis.

Conclusions

The FBN1/VEGFR2/STAT2 signaling axis may induce chemoresistance of ovarian cancer cells by participating in the process of glycolysis and angiogenesis. The present study suggested a novel FBN1‐targeted therapy and/or combination of FBN1 inhibition and antiangiogenic drug for treating ovarian cancer.

Long noncoding RNA LINC00930 promotes PFKFB3-mediated tumor glycolysis and cell proliferation in nasopharyngeal carcinoma

Background

Metabolic reprogramming is a hallmark of cancer. However, the roles of long noncoding RNAs (lncRNAs) in cancer metabolism, especially glucose metabolism remain largely unknown.

Results

In this study, we identified and functionally characterized a novel metabolism-related lncRNA, LINC00930, which was upregulated and associated with tumorigenesis, lymphatic invasion, metastasis, and poor prognosis in nasopharyngeal carcinoma (NPC). Functionally, LINC00930 was required for increased glycolysis activity and cell proliferation in multiple NPC models in vitro and in vivo. Mechanistically, LINC00930 served as a scaffold to recruit the RBBP5 and GCN5 complex to the PFKFB3 promoter and increased H3K4 trimethylation and H3K9 acetylation levels in the PFKFB3 promoter region, which epigenetically transactivating PFKFB3, and thus promoting glycolytic flux and cell cycle progression. Clinically, targeting LINC00930 and PFKFB3 in combination with radiotherapy induced tumor regression.

Conclusions

Collectively, LINC00930 is mechanistically, functionally and clinically oncogenic in NPC. Targeting LINC00930 and its pathway may be meaningful for treating patients with NPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02282-9.

The regulation, function, and role of lipophagy, a form of selective autophagy, in metabolic disorders

Autophagy is a conserved method of quality control in which cytoplasmic contents are degraded via lysosomes. Lipophagy, a form of selective autophagy and a novel type of lipid metabolism, has recently received much attention. Lipophagy is defined as the autophagic degradation of intracellular lipid droplets (LDs). Although much remains unknown, lipophagy appears to play a significant role in many organisms, cell types, metabolic states, and diseases. It participates in the regulation of intracellular lipid storage, intracellular free lipid levels (e.g., fatty acids), and energy balance. However, it remains unclear how intracellular lipids regulate autophagy. Impaired lipophagy can cause cells to become sensitive to death stimuli and may be responsible for the onset of a variety of diseases, including nonalcoholic fatty liver disease and metabolic syndrome. Like autophagy, the role of lipophagy in cancer is poorly understood, although analysis of specific autophagy receptors has helped to expand the diversity of chemotherapeutic targets. These studies have stimulated increasing interest in the role of lipophagy in the pathogenesis and treatment of cancer and other human diseases.

Targeting of PFKFB3 with miR-206 but not mir-26b inhibits ovarian cancer cell proliferation and migration involving FAK downregulation

Few studies explored the role of microRNAs (miRNAs) in the post-transcriptional regulation of glycolytic proteins and downstream effectors in ovarian cancer cells. We recently showed that the functional activation of the cytoskeletal regulator FAK in endothelial cells is fostered by the glycolytic enhancer 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3). We tested the hypothesis that miR-206 and mir-26b, emerging onco-suppressors targeting PFKFB3 in estrogen-dependent tumors, would regulate proliferation and migration of serous epithelial ovarian cancer (EOC) cells via common glycolytic proteins, i.e., GLUT1 and PFKFB3, and downstream FAK. PFKFB3 was overexpressed in SKOV3, and its pharmacological inhibition with 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO) significantly reduced cell proliferation and motility. Both miR-206 and miR-26b directly targeted PFKFB3 as evaluated by a luciferase reporter assay. However, endogenous levels of miR-26b were higher than those of miR-206, which was barely detectable in SKOV3 as well as OVCAR5 and CAOV3 cells. Accordingly, only the anti-miR-26b inhibitor concentration-dependently increased PFKFB3 levels. While miR-206 overexpression impaired proliferation and migration by downregulating PFKFB3 levels, the decreased PFKFB3 protein levels related to miR-26 overexpression had no functional consequences in all EOC cell lines. Finally, consistent with the migration outcome, exogenous miR-206 and miR-26b induced opposite effects on the levels of total FAK and of its phosphorylated form at Tyr576/577. 3PO did not prevent miR-26b-induced SKOV3 migration. Overall, these results support the inverse relation between endogenous miRNA levels and their tumor-suppressive effects and suggest that restoring miR-206 expression represents a potential dual anti-PFKFB3/FAK strategy to control ovarian cancer progression.

Long Noncoding RNA RMRP Contributes to Paclitaxel Sensitivity of Ovarian Cancer by Regulating miR-580-3p/MICU1 Signaling

Ovarian cancer is a prevalent female malignancy affecting the health and life of an increasing population of women around the world. Paclitaxel (PTX) resistance is a significant clinical problem in the treatment of ovarian cancer. However, the regulation mechanism of PTX resistance remains unclear. In this investigation, we reported an innovative function of the long noncoding RNA RMRP in promoting PTX resistance and glycolysis of ovarian cancer cells. We observed that RMRP was highly expressed in the ovarian cancer samples, in which the expression of RMRP was elevated in the PTX-resistant patients compared with the PTX-sensitive patients. Meanwhile, RMRP was upregulated in PTX-resistant ovarian cancer cell lines. Functionally, we found that the silencing of RMRP by siRNA significantly enhanced the PTX sensitivity of PTX-resistant ovarian cancer cells, in which the IC50 of PTX was reduced by RMRP depletion. The RMRP knockdown reduced cell viabilities and enhanced cell apoptosis of PTX-resistant ovarian cancer cells. Moreover, we observed that glucose uptake was enhanced in PTX-resistant ovarian cancer cells. The depletion of RMRP decreased glucose uptake, lactate product, and ATP production in PTX-resistant ovarian cancer cells. About the mechanism, we identified that RMRP was able to sponge miR-580-3p to enhance mitochondrial calcium uptake 1 (MICU1) expression in PTX-resistant ovarian cancer cells. MICU1 overexpression and miR-580-3p repression could reverse the RMRP-inhibited proliferation of PTX-resistant ovarian cancer cells in vitro. Thus, we concluded that RMRP contributes to PTX resistance and glycolysis of ovarian cancer by enhancing MICU1 expression through sponging miR-580-3p. Targeting RMRP may serve as a potential therapeutic strategy for the treatment of PTX-resistant ovarian cancer patients.

PFKFB3 Regulates Chemoresistance, Metastasis and Stemness via IAP Proteins and the NF-κB Signaling Pathway in Ovarian Cancer

Glycolysis has been reported to be critical for cancer stem cells (CSCs), which are associated with tumor chemoresistance, metastasis and recurrence. Thus, selectively targeting glycolytic enzymes may be a potential therapy for ovarian cancer. 6‐phosphofructo‐2‐kinase/fructose‐2,6‐biphosphatase 3 (PFKFB3), the main source of fructose-2,6-bisphosphate, controls the first committed step in glycolysis. We investigate the clinical significance and roles of PFKFB3 in ovarian cancer using in vitro and in vivo experiments. We demonstrate that PFKFB3 is widely overexpressed in ovarian cancer and correlates with advanced stage/grade and poor outcomes. Significant up-regulation of PFKFB3 was found in ascites and metastatic foci, as well as CSC-enriched tumorspheres and ALDH+CD44+ cells. 3PO, a PFKFB3 inhibitor, reduced lactate level and sensitized A2780CP cells to cisplatin treatment, along with the modulation of inhibitors of apoptosis proteins (c-IAP1, c-IAP2 and survivin) and an immune modulator CD70. Blockade of PFKFB3 by siRNA approach in the CSC-enriched subset led to decreases in glycolysis and CSC properties, and activation of the NF-κB cascade. PFK158, another potent inhibitor of PFKFB3, impaired the stemness of ALDH+CD44+ cells in vitro and in vivo, whereas ectopic expression of PFKFB3 had the opposite results. Overall, PFKFB3 was found to mediate metabolic reprogramming, chemoresistance, metastasis and stemness in ovarian cancer, possibly via the modulation of inhibitors of apoptosis proteins and the NF-κB signaling pathway; thus, suggesting that PFKFB3 may be a potential therapeutic target for ovarian cancer.