PKM2, cancer metabolism, and the road ahead

The "sweet" path to cancer: focus on cellular glucose metabolism

The hypoxia-inducible factor-1α (HIF-1α), a key player in the adaptive regulation of energy metabolism, and the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2), a critical regulator of glucose consumption, are the main drivers of the metabolic rewiring in cancer cells. The use of glycolysis rather than oxidative phosphorylation, even in the presence of oxygen (i.e., Warburg effect or aerobic glycolysis), is a major metabolic hallmark of cancer. Aerobic glycolysis is also important for the immune system, which is involved in both metabolic disorders development and tumorigenesis. More recently, metabolic changes resembling the Warburg effect have been described in diabetes mellitus (DM). Scientists from different disciplines are looking for ways to interfere with these cellular metabolic rearrangements and reverse the pathological processes underlying their disease of interest. As cancer is overtaking cardiovascular disease as the leading cause of excess death in DM, and biological links between DM and cancer are incompletely understood, cellular glucose metabolism may be a promising field to explore in search of connections between cardiometabolic and cancer diseases. In this mini-review, we present the state-of-the-art on the role of the Warburg effect, HIF-1α, and PKM2 in cancer, inflammation, and DM to encourage multidisciplinary research to advance fundamental understanding in biology and pathways implicated in the link between DM and cancer.

Simultaneous suppression of PKM2 and PHGDH elicits synergistic anti-cancer effect in NSCLC

Metabolic reprogramming is a hallmark of human cancer. Cancer cells exhibit enhanced glycolysis, which allows glycolytic intermediates to be diverted into several other biosynthetic pathways, such as serine synthesis. Here, we explored the anti-cancer effects of the pyruvate kinase (PK) M2 inhibitor PKM2-IN-1 alone or in combination with the phosphoglycerate dehydrogenase (PHGDH) inhibitor NCT-503 in human NSCLC A549 cells in vitro and in vivo. PKM2-IN-1 inhibited proliferation and induced cell cycle arrest and apoptosis, with increased glycolytic intermediate 3-phosphoglycerate (3-PG) level and PHGDH expression. The combination of PKM2-IN-1 and NCT-503 further suppressed cancer cell proliferation and induced G2/M phase arrest, accompanied by the reduction of ATP, activation of AMPK and inhibition of its downstream mTOR and p70S6K, upregulation of p53 and p21, as well as downregulation of cyclin B1 and cdc2. In addition, combined treatment triggered ROS-dependent apoptosis by affecting the intrinsic Bcl-2/caspase-3/PARP pathway. Moreover, the combination suppressed glucose transporter type 1 (GLUT1) expression. In vivo, co-administration of PKM2-IN-1 and NCT-503 significantly inhibited A549 tumor growth. Taken together, PKM2-IN-1 in combination with NCT-503 exhibited remarkable anti-cancer effects through induction of G2/M cell cycle arrest and apoptosis, in which the metabolic stress induced ATP reduction and ROS augmented DNA damage might be involved. These results suggest that the combination of PKM2-IN-1 and NCT-503 might be a potential strategy for the therapy of lung cancer.

S-lactoyl modification of KEAP1 by a reactive glycolytic metabolite activates NRF2 signaling

KEAP1 (Kelch-like ECH-associated protein), a cytoplasmic repressor of the oxidative stress responsive transcription factor Nuclear factor erythroid 2-related factor 2 (NRF2), senses the presence of electrophilic agents by modification of its sensor cysteine residues. In addition to xenobiotics, several reactive metabolites have been shown to covalently modify key cysteines on KEAP1, although the full repertoire of these molecules and their respective modifications remain undefined. Here, we report the discovery of sAKZ692, a small molecule identified by high-throughput screening that stimulates NRF2 transcriptional activity in cells by inhibiting the glycolytic enzyme pyruvate kinase. sAKZ692 treatment promotes the buildup of glyceraldehyde 3-phosphate, a metabolite which leads to S-lactate modification of cysteine sensor residues of KEAP1, resulting in NRF2-dependent transcription. This work identifies a posttranslational modification of cysteine derived from a reactive central carbon metabolite and helps further define the complex relationship between metabolism and the oxidative stress-sensing machinery of the cell.

TFEB inhibition induces melanoma shut-down by blocking the cell cycle and rewiring metabolism

Melanomas are characterised by accelerated cell proliferation and metabolic reprogramming resulting from the contemporary dysregulation of the MAPK pathway, glycolysis and the tricarboxylic acid (TCA) cycle. Here, we suggest that the oncogenic transcription factor EB (TFEB), a key regulator of lysosomal biogenesis and function, controls melanoma tumour growth through a transcriptional programme targeting ERK1/2 activity and glucose, glutamine and cholesterol metabolism. Mechanistically, TFEB binds and negatively regulates the promoter of DUSP-1, which dephosphorylates ERK1/2. In melanoma cells, TFEB silencing correlates with ERK1/2 dephosphorylation at the activation-related p-Thr185 and p-Tyr187 residues. The decreased ERK1/2 activity synergises with TFEB control of CDK4 expression, resulting in cell proliferation blockade. Simultaneously, TFEB rewires metabolism, influencing glycolysis, glucose and glutamine uptake, and cholesterol synthesis. In TFEB-silenced melanoma cells, cholesterol synthesis is impaired, and the uptake of glucose and glutamine is inhibited, leading to a reduction in glycolysis, glutaminolysis and oxidative phosphorylation. Moreover, the reduction in TFEB level induces reverses TCA cycle, leading to fatty acid production. A syngeneic BRAFV600E melanoma model recapitulated the in vitro study results, showing that TFEB silencing sustains the reduction in tumour growth, increase in DUSP-1 level and inhibition of ERK1/2 action, suggesting a pivotal role for TFEB in maintaining proliferative melanoma cell behaviour and the operational metabolic pathways necessary for meeting the high energy demands of melanoma cells.

A PKM2 inhibitor induces apoptosis and autophagy through JAK2 in human oral squamous cell carcinoma cells

The enzyme pyruvate kinase M2 (PKM2) is involved in glycolysis, which plays an important role in the regulation of tumor progression. In this study, we investigated the anti-tumor activity of N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(prop-2-yn-1-yloxy)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide (MTP), a PKM2 inhibitor, in oral squamous cell carcinoma (OSCC) cells. Our results showed that MTP inhibited cell growth with IC50 values of 0.59 μM and 0.78 μM in SCC2095 and HSC3 OSCC cells, respectively. MTP induced caspase-dependent apoptosis, which was associated with the modulation of PKM2 and oncogenic biomarkers epidermal growth factor receptor and β-catenin. In addition, MTP increased the generation of reactive oxygen species (ROS) and modulated the expression of autophagic gene products, including LC3B-II and p62. Western blotting showed that MTP inhibited Janus kinase 2 (JAK2) signaling, and JAK2 overexpression partially reversed MTP-mediated cytotoxicity. Taken together, these data indicate the potential use of MTP as a therapeutic agent for OSCC.

The interplay between non-coding RNAs and alternative splicing: from regulatory mechanism to therapeutic implications in cancer

Alternative splicing (AS) is a common and conserved process in eukaryotic gene regulation. It occurs in approximately 95% of multi-exon genes, greatly enriching the complexity and diversity of mRNAs and proteins. Recent studies have found that in addition to coding RNAs, non-coding RNAs (ncRNAs) are also inextricably linked with AS. Multiple different types of ncRNAs are generated by AS of precursor long non-coding (pre-lncRNAs) or precursor messenger RNAs (pre-mRNAs). Furthermore, ncRNAs, as a novel class of regulators, can participate in AS regulation by interacting with the cis-acting elements or trans-acting factors. Several studies have implicated abnormal expression of ncRNAs and ncRNA-related AS events in the initiation, progression, and therapy resistance in various types of cancers. Therefore, owing to their roles in mediating drug resistance, ncRNAs, AS-related factors and AS-related novel antigens may serve as promising therapeutic targets in cancer treatment. In this review, we summarize the interaction between ncRNAs and AS processes, emphasizing their great influences on cancer, especially on chemoresistance, and highlighting their potential values in clinical treatment.

OBHS Drives Abnormal Glycometabolis Reprogramming via GLUT1 in Breast Cancer

Due to the poor metabolic conditions fomenting the emergence of the Warburg effect (WE) phenotype, abnormal glycometabolism has become a unique and fundamental research topic in the field of tumor biology. Moreover, hyperglycemia and hyperinsulinism are associated with poor outcomes in patients with breast cancer. However, there are a few studies on anticancer drugs targeting glycometabolism in breast cancer. We hypothesized that Oxabicycloheptene sulfonate (OBHS), a class of compounds that function as selective estrogen receptor modulators, may hold potential in a therapy for breast cancer glycometabolism. Here, we evaluated concentrations of glucose, glucose transporters, lactate, 40 metabolic intermediates, and glycolytic enzymes using an enzyme-linked immunosorbent assay, Western blotting, and targeted metabolomic analysis in, in vitro and in vivo breast cancer models. OBHS significantly inhibited the expression of glucose transporter 1 (GLUT1) via PI3K/Akt signaling pathway to suppress breast cancer progression and proliferation. Following an investigation of the modulatory effect of OBHS on breast cancer cells, we found that OBHS suppressed the glucose phosphorylation and oxidative phosphorylation of glycolytic enzymes, leading to the decreased biological synthesis of ATP. This study was novel in highlighting the role of OBHS in the remodeling of tumor glycometabolism in breast cancer, and this is worth further investigation of breast cancer in clinical trials.

Metabolic reprogramming in cancer: Mechanisms and therapeutics

Cancer cells characterized by uncontrolled growth and proliferation require altered metabolic processes to maintain this characteristic. Metabolic reprogramming is a process mediated by various factors, including oncogenes, tumor suppressor genes, changes in growth factors, and tumor–host cell interactions, which help to meet the needs of cancer cell anabolism and promote tumor development. Metabolic reprogramming in tumor cells is dynamically variable, depending on the tumor type and microenvironment, and reprogramming involves multiple metabolic pathways. These metabolic pathways have complex mechanisms and involve the coordination of various signaling molecules, proteins, and enzymes, which increases the resistance of tumor cells to traditional antitumor therapies. With the development of cancer therapies, metabolic reprogramming has been recognized as a new therapeutic target for metabolic changes in tumor cells. Therefore, understanding how multiple metabolic pathways in cancer cells change can provide a reference for the development of new therapies for tumor treatment. Here, we systemically reviewed the metabolic changes and their alteration factors, together with the current tumor regulation treatments and other possible treatments that are still under investigation. Continuous efforts are needed to further explore the mechanism of cancer metabolism reprogramming and corresponding metabolic treatments.

Targeting PKLR/MYCN/ROMO1 signaling suppresses neuroendocrine differentiation of castration-resistant prostate cancer

Conventional treatment of prostate cancer (PCa) uses androgen-deprivation therapy (ADT) to inhibit androgen receptor (AR) signaling-driven tumor progression. ADT-induced PCa recurrence may progress to an AR-negative phenotype with neuroendocrine (NE) histologic features, which are associated with metabolic disturbances and poor prognoses. However, the metabolic pathways that regulate NE differentiation (NED) in PCa remain unclear. Herein, we show a regulatory mechanism in NED-associated metabolism dysfunction induced by ADT, whereby overexpression of pyruvate kinase L/R (PKLR) mediates oxidative stress through upregulation of reactive oxygen species modulator 1 (ROMO1), thereby promoting NED and aggressiveness. ADT mediates the nuclear translocation of PKLR, which binds to the MYCN/MAX complex to upregulate ROMO1 and NE-related genes, leading to altered mitochondrial function and NED of PCa. Targeting nuclear PKLR/MYCN using bromodomain and extra-terminal motif (BET) inhibitors has the potential to reduce PKLR/MYCN-driven NED. Abundant ROMO1 in serum samples may provide prognostic information in patients with ADT. Our results suggest that ADT resistance leads to upregulation of PKLR/MYCN/ROMO1 signaling, which may drive metabolic reprogramming and NED in PCa. We further show that increased abundance of serum ROMO1 may be associated with the development of NE-like PCa.

IgSF11-mediated phosphorylation of pyruvate kinase M2 regulates osteoclast differentiation and prevents pathological bone loss

Osteoclasts are primary bone-resorbing cells, and receptor-activated NF-kB ligand (RANKL) stimulation is the key driver of osteoclast differentiation. During late-stage differentiation, osteoclasts become multinucleated and enlarged (so-called "maturation"), suggesting their need to adapt to changing metabolic demands and a substantial increase in size. Here, we demonstrate that immunoglobulin superfamily 11 (IgSF11), which is required for osteoclast differentiation through an association with the postsynaptic scaffolding protein PSD-95, regulates osteoclast differentiation by controlling the activity of pyruvate kinase M isoform 2 (PKM2). By using a system that directly induces the activation of IgSF11 in a controlled manner, we identified PKM2 as a major IgSF11-induced tyrosine-phosphorylated protein. IgSF11 activates multiple Src family tyrosine kinases (SFKs), including c-Src, Fyn, and HcK, which phosphorylate PKM2 and thereby inhibit PKM2 activity. Consistently, IgSF11-deficient cells show higher PKM2 activity and defective osteoclast differentiation. Furthermore, inhibiting PKM2 activities with the specific inhibitor Shikonin rescues the impaired osteoclast differentiation in IgSF11-deficient cells, and activating PKM2 with the specific activator TEPP46 suppresses osteoclast differentiation in wild-type cells. Moreover, PKM2 activation further suppresses osteoclastic bone loss without affecting bone formation in vivo. Taken together, these results show that IgSF11 controls osteoclast differentiation through PKM2 activity, which is a metabolic switch necessary for optimal osteoclast maturation.

Parkin exerts the tumor-suppressive effect through targeting mitochondria

The role of PARKIN in Parkinson's disease is well established but its role in cancer has recently emerged. PARKIN serves as a tumor suppressor in many cancers and loses the tumor-suppressive function due to loss of heterozygosity and DNA copy number. But how PARKIN protects against cancer is poorly understood. Through the analysis of PARKIN substrates and their association with mitochondria, this viewpoint discussed that PARKIN exerts its anti-cancer activity through targeting mitochondria. Mitochondria function as a convergence point for many signaling pathways and biological processes, including apoptosis, cell cycle, mitophagy, energy metabolism, oxidative stress, calcium homeostasis, inflammation, and so forth. PARKIN participates in these processes through regulating its mitochondrial targets. Conversely, these mitochondrial substrates also influence the function of PARKIN under different cellular circumstances. We believe that future studies in this area may lead to novel therapeutic targets and strategies for cancer therapy.

Design, Synthesis and Biological Evaluation of Quinoline-8-Sulfonamides as Inhibitors of the Tumor Cell-Specific M2 Isoform of Pyruvate Kinase: Preliminary Study

Cancer cells need to carefully regulate their metabolism to keep them growing and dividing under the influence of different nutrients and oxygen levels. Muscle isoform 2 of pyruvate kinase (PKM2) is a key glycolytic enzyme involved in the generation of ATP and is critical for cancer metabolism. PKM2 is expressed in many human tumors and is regulated by complex mechanisms that promote tumor growth and proliferation. Therefore, it is considered an attractive therapeutic target for modulating tumor metabolism. Various modulators regulate PKM2, shifting it between highly active and less active states. In the presented work, a series of 8-quinolinesulfonamide derivatives of PKM2 modulators were designed using molecular docking and molecular dynamics techniques. New compounds were synthesized using the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Compound 9a was identified in in silico studies as a potent modulator of muscle isoform 2 of pyruvate kinase. The results obtained from in vitro experiments confirmed the ability of compound 9a to reduce the intracellular pyruvate level in A549 lung cancer cells with simultaneous impact on cancer cell viability and cell-cycle phase distribution. Moreover, compound 9a exhibited more cytotoxicity on cancer cells than normal cells, pointing to high selectivity in the mode of action. These findings indicate that the introduction of another quinolinyl fragment to the modulator molecule may have a significant impact on pyruvate levels in cancer cells and provides further directions for future research to find novel analogs suitable for clinical applications in cancer treatment.

Transcriptional Response to Hypoxia: The Role of HIF-1-Associated Co-Regulators

The Hypoxia Inducible Factor 1 (HIF-1) plays a major role in the cellular response to hypoxia by regulating the expression of many genes involved in adaptive processes that allow cell survival under low oxygen conditions. Adaptation to the hypoxic tumor micro-environment is also critical for cancer cell proliferation and therefore HIF-1 is also considered a valid therapeutical target. Despite the huge progress in understanding regulation of HIF-1 expression and activity by oxygen levels or oncogenic pathways, the way HIF-1 interacts with chromatin and the transcriptional machinery in order to activate its target genes is still a matter of intense investigation. Recent studies have identified several different HIF-1- and chromatin-associated co-regulators that play important roles in the general transcriptional activity of HIF-1, independent of its expression levels, as well as in the selection of binding sites, promoters and target genes, which, however, often depends on cellular context. We review here these co-regulators and examine their effect on the expression of a compilation of well-characterized HIF-1 direct target genes in order to assess the range of their involvement in the transcriptional response to hypoxia. Delineating the mode and the significance of the interaction between HIF-1 and its associated co-regulators may offer new attractive and specific targets for anticancer therapy.

Inhibition of ATF4-mediated elevation of both autophagy and AKT/mTOR was involved in antitumorigenic activity of curcumin

Curcumin, a natural hydrophobic polyphenol, carries significant anticancer activity. The protein kinase B (AKT)/the mammalian target of the rapamycin (mTOR) pathway and autophagy are well known to be involved in carcinogenesis, and usually, inhibition of mTOR is the main reason to promote autophagy. In this study, however, autophagy and mTOR were found to be inhibited simultaneously by curcumin treatments, and both of them played an important role in the effect of curcumin on suppressing the growth of A549 cells. Tunicamycin (TM), the activator of Endoplasmic Reticulum (ER) stress, increased both autophagy and AKT/mTOR, while curcumin could significantly decrease TM-induced autophagy and AKT/mTOR. Furthermore, curcumin could inhibit TM-induced aerobic glycolysis in A549 cells, and decrease the level of cycle-related and migration-related proteins. Blocking activating transcription factor 4 (ATF4) by siRNA strongly reduced both the expression of autophagy-related proteins and AKT/mTOR. ChIP assay illustrated that ATF4 protein could bind to the promotor sequence of either ATG4B or AKT1. The transplantation tumor experiment showed that the weight and volume of the transplanted tumors were reduced significantly in the BALB/c mice subcutaneously injected with A549 cells treated with curcumin. Moreover, intranasal administration of curcumin decreased the protein level of autophagy, AKT/mTOR and ER stress in lung tissues of BALB/c mice. Taken together, our results demonstrated that inhibition of ER stress-dependent ATF4-mediated autophagy and AKT/mTOR pathway plays an important role in anticancer effect of curcumin.

Metabolic reprograming of cancer as a therapeutic target

Our understanding of metabolic reprogramming in cancer has tremendously improved along with the technical progression of metabolomic analysis. Metabolic changes in cancer cells proved much more complicated than the classical Warburg effect. Previous studies have approached metabolic changes as therapeutic and/or chemopreventive targets. Recently, several clinical trials have reported anti-cancer agents associated with metabolism. However, whether cancer cells are dependent on metabolic reprogramming or favor suitable conditions remains nebulous. Both scenarios are possibly intertwined. Identification of downstream molecules and the understanding of mechanisms underlying reprogrammed metabolism can improve the effectiveness of cancer therapy. Here, we review several examples of the metabolic reprogramming of cancer cells and the therapies targeting the metabolism-related molecules as well as discuss practical approaches to improve the next generation of cancer therapies focused on the metabolic reprogramming of cancer.

RNA splicing dysregulation and the hallmarks of cancer

Dysregulated RNA splicing is a molecular feature that characterizes almost all tumour types. Cancer-associated splicing alterations arise from both recurrent mutations and altered expression of trans-acting factors governing splicing catalysis and regulation. Cancer-associated splicing dysregulation can promote tumorigenesis via diverse mechanisms, contributing to increased cell proliferation, decreased apoptosis, enhanced migration and metastatic potential, resistance to chemotherapy and evasion of immune surveillance. Recent studies have identified specific cancer-associated isoforms that play critical roles in cancer cell transformation and growth and demonstrated the therapeutic benefits of correcting or otherwise antagonizing such cancer-associated mRNA isoforms. Clinical-grade small molecules that modulate or inhibit RNA splicing have similarly been developed as promising anticancer therapeutics. Here, we review splicing alterations characteristic of cancer cell transcriptomes, dysregulated splicing's contributions to tumour initiation and progression, and existing and emerging approaches for targeting splicing for cancer therapy. Finally, we discuss the outstanding questions and challenges that must be addressed to translate these findings into the clinic.

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.

Glucose metabolism and lncRNAs in breast cancer: Sworn friend

BACKGROUND

Glucose metabolism disorder is a common feature in cancer. Cancer cells generate much energy through anaerobic glycolysis, which promote the development of tumors. However, long non-coding RNA may play an important role in this process. Our aim is to explore a prognostic risk model based on the glucose metabolism-related lncRNAs which provides clues that lncRNAs predict a clinical outcome through glucose metabolism in breast cancer.

METHODS

1222 RNA-seq were extracted from the TCGA database, and 74 glucose metabolism-related genes were loaded from the GSEA website. Then, 7 glucose metabolism-related lncRNAs risk score model was developed by univariate, Lasso, and multivariate regression analysis. The lncRNA risk model showed that high-risk patients predict a poor clinical outcome with high reliability (P=2.838×10-6). Univariate and multivariate independent prognostic analysis and ROC curve analysis proved that the risk score was an independent prognostic factor in breast cancer with an AUC value of 0.652. Finally, Gene set enrichment analysis showed that cell cycle-related pathways were significantly enriched in a high-risk group.

RESULTS

Our results showed that glucose metabolism-related lncRNAs can affect breast cancer progression. 7 glucose metabolism-related lncRNAs prognostic signature was established to evaluate the OS of patients with breast cancer. PICSAR, LINC00839, AP001505.1, LINC00393 were risk factors and expressed highly in the high-risk group. A Nomogram was made based on this signature to judge patients' living conditions and prognosis.

CONCLUSION

7 glucose metabolism-related lncRNAs risk score model had a high prognostic value in breast cancer. PICSAR, LINC00839, AP001505.1, LINC00393 were risk factors. AP001505.1 expression was increased in most triple-negative breast cancer cells treated with high glucose, which may also take part in breast cancer progression and potential therapeutic targets.

OTUB2 promotes the progression of endometrial cancer by regulating the PKM2-mediated PI3K/AKT signaling pathway

Endometrial carcinoma (EC) morbidity and mortality have been increasing in recent years. Otubain 2 (OTUB2) was shown to be upregulated in EC patients, so the aim of this study was to explore the role of OTUB2 in EC. Cell Counting Kit-8 (CCK-8), colony formation, enzyme-linked immunosorbent assay, the wound healing assay, and Transwell invasion assays were used to investigate the specific role of OTUB2 in EC tumorigenesis. Real-time polymerase chain reaction and western blot analysis were used to detect the expression of OTUB2 in EC tissues and cells. OTUB2 is upregulated in EC patients and cell lines and is associated with a poor prognosis. The overexpression of OTUB2 promoted glycolysis and induced the proliferation, migration, and invasion of endometrial cancer cells. The silencing of OTUB2 had the opposite effect. In addition, the silencing of OTUB2 significantly suppressed the expression levels of PKM2. Importantly, inhibition of the PKM2/PI3K/AKT signaling pathway significantly reversed the promoting effect of OTUB2 overexpression on EC. OTUB2 regulated the proliferation and invasion of EC cells by regulating the PKM2/PI3K/AKT signaling pathway. OTUB2 may serve as a potential prognostic and therapeutic target in EC.

Expression of PKM2 in wound keratinocytes is coupled to angiogenesis during skin repair in vivo and in HaCaT keratinocytes in vitro

An injured skin is rapidly restored in a manner of wound healing. We have previously shown that intact insulin signaling and glucose uptake are fundamental to proper wound closure. Consequently, under exacerbated inflammation, compromised insulin action and glucose uptake lead to impaired healing. However, in spite of the increased attention to cell metabolism during tissue regeneration, metabolic mediators that govern cellular and physiological processes throughout skin repair remained largely elusive. Through assessment of mRNA using real-time PCR and protein blot analysis, we report that healing of cutaneous wounds comprise a boosted expression of genes involved in glycolysis, oxidative phosphorylation, pentose phosphate shunt, and glutamine anaplerosis. We further focused on the functional role of pyruvate kinase M (PKM) isoenzymes that catalyze the final and rate-limiting step of glycolysis. Whereas the expression of the metabolic constitutively active Pkm1 isozyme remained almost unchanged, Pkm2 is augmented during the inflammatory phase of healing. The immunohistochemistry and RNA in situ hybridization analysis showed a confined Pkm2 expression to keratinocytes of the hyperproliferative epithelium and, to a lesser extent, infiltrating neutrophils and monocytes as well as later on in macrophages. Notably, the expression of Pkm2 in keratinocytes facing the wound bed side colocalized with VEGF expression. The in vitro knockdown of PKM2 in HaCaT keratinocytes using small interfering (si) RNA confirmed an acute role for PKM2 in facilitating the complete induction of VEGF mRNA and protein expression in keratinocytes; this function is mainly HIF-1α independent. KEY MESSAGES: • Wound healing involves activation of glycolysis, oxidative phosphorylation, pentos-phosphate shunt, and replenishment of tri-carboxylic acid (TCA) cycle through glutamine anaplerosis. • The pyruvate kinase M2 (PKM2) isoform is upregulated during the inflammatory phase of cutaneous healing, mainly in keratinocytes of hyperproliferative epithelia. • In vivo, the expression of VEGF in wound keratinocytes is colocalized with PKM2. • PKM2 is required for full induction of VEGF in HaCaT keratinocytes in vitro.

Mediation of PKM2-dependent glycolytic and non-glycolytic pathways by ENO2 in head and neck cancer development

BACKGROUND

Enolase 2 (ENO2) is a crucial glycolytic enzyme in cancer metabolic process and acts as a "moonlighting" protein to play various functions in diverse cellular processes unrelated to glycolysis. ENO2 is highly expressed in head and neck squamous cell carcinoma (HNSCC) tissues relative to normal tissues; however, its impact and underlying regulatory mechanisms in HNSCC malignancy remain unclear.

METHODS

Molecular alterations were examined by bioinformatics, qRT-PCR, western blotting, immunofluorescence, immunohistochemistry, immunoprecipitation, and ChIP-PCR assays. Metabolic changes were assessed by intracellular levels of ATP and glucose. Animal study was used to evaluate the therapeutic efficacy of the ENO inhibitor.

RESULTS

ENO2 is required for HNSCC cell proliferation and glycolysis, which, surprisingly, is partially achieved by controlling PKM2 protein stability and its nuclear translocation. Mechanistically, loss of ENO2 expression promotes PKM2 protein degradation via the ubiquitin-proteasome pathway and prevents the switch of cytoplasmic PKM2 to the nucleus by inactivating AKT signaling, leading to a blockade in PKM2-mediated glycolytic flux and CCND1-associated cell cycle progression. In addition, treatment with the ENO inhibitor AP-III-a4 significantly induces HNSCC remission in a preclinical mouse model.

CONCLUSION

Our work elucidates the signaling basis underlying ENO2-dependent HNSCC development, providing evidence to establish a novel ENO2-targeted therapy for treating HNSCC.

MiR-1286 inhibits lung cancer growth through aerobic glycolysis by targeting PKM2

INTRODUCTION

This study aims to explore the effects of microRNA-1286 (miR-1286) on the development of non-small cell lung cancer (NSCLC) via the aerobic glycolysis pathway by targeting pyruvate kinase muscle isozyme M2 (PKM2).

MATERIAL AND METHODS

The mRNA levels of miR-1286 in NSCLC tissues and mouse tumor tissues were detected by q-PCR. MiR-1286 was knocked down and overexpressed separately in A549 cells. The effect of miR-1286 on cell proliferation was determined by CCK8 assay. Western blotting was used to measure the expression of PKM2 protein. Lactate production assay was used to detect the aerobic glycolysis in A549 cells. The effect of miR-1286 in vivo was determined by xenograft assay.

RESULTS

The mRNA level of miR-1286 decreased in NSCLC tissues compared with paired, tumor adjacent normal tissues. In addition, miR-1286 inhibited A549 cell proliferation in vitro. Moreover, knockdown of miR-1286 increased PKM2 expression and lactate production. Thus, miR-1286 expression negatively correlated with PKM2 in A549 cells. At the same time, in vivo experiments also showed that miR-1286 suppressed the growth of A549 cells and PKM2 was the target gene of miR-1286.

CONCLUSIONS

These data show that miR-1286 inhibits lung cancer proliferation via aerobic glycolysis by targeting PKM2, which suggests that the functions of miR-1286 in NSCLC may play a key role in tumor progression and that miR-1286 can be a promising predictive biomarker and potential therapeutic target for NSCLC.

Warburg Effect Revisited: Embodiment of Classical Biochemistry and Organic Chemistry. Current State and Prospects

The Nobel Prize Winner (1931) Dr. Otto H. Warburg had established that the primary energy source of the cancer cell is aerobic glycolysis (the Warburg effect). He also postulated the hypothesis about "the prime cause of cancer", which is a matter of debate nowadays. Contrary to the hypothesis, his discovery was recognized entirely. However, the discovery had almost vanished in the heat of battle about the hypothesis. The prime cause of cancer is essential for the prevention and diagnosis, yet the effects that influence tumor growth are more important for cancer treatment. Due to the Warburg effect, a large amount of data has been accumulated on biochemical changes in the cell and the organism as a whole. Due to the Warburg effect, the recovery of normal biochemistry and oxygen respiration and the restoration of the work of mitochondria of cancer cells can inhibit tumor growth and lead to remission. Here, we review the current knowledge on the inhibition of abnormal glycolysis, neutralization of its consequences, and normalization of biochemical parameters, as well as recovery of oxygen respiration of a cancer cell and mitochondrial function from the point of view of classical biochemistry and organic chemistry.

Aberrant splicing in human cancer: An RNA structural code point of view

Alternative splicing represents an essential process that occurs widely in eukaryotes. In humans, most genes undergo alternative splicing to ensure transcriptome and proteome diversity reflecting their functional complexity. Over the last decade, aberrantly spliced transcripts due to mutations in cis- or trans-acting splicing regulators have been tightly associated with cancer development, largely drawing scientific attention. Although a plethora of single proteins, ribonucleoproteins, complexed RNAs, and short RNA sequences have emerged as nodal contributors to the splicing cascade, the role of RNA secondary structures in warranting splicing fidelity has been underestimated. Recent studies have leveraged the establishment of novel high-throughput methodologies and bioinformatic tools to shed light on an additional layer of splicing regulation in the context of RNA structural elements. This short review focuses on the most recent available data on splicing mechanism regulation on the basis of RNA secondary structure, emphasizing the importance of the complex RNA G-quadruplex structures (rG4s), and other specific RNA motifs identified as splicing silencers or enhancers. Moreover, it intends to provide knowledge on newly established techniques that allow the identification of RNA structural elements and highlight the potential to develop new RNA-oriented therapeutic strategies against cancer.

FLI1 accelerates leukemogenesis through transcriptional regulation of pyruvate kinase-L/R and other glycolytic genes

In cancer cells, multiple oncogenes and tumor suppressors control glycolysis to sustain rapid proliferation. The ETS-related transcription factor Fli1 plays a critical role in the induction and progression of leukemia, yet, the underlying mechanism of this oncogenic event is still not fully understood. In this study, RNAseq analysis of FLI1-depleted human leukemic cells revealed transcriptional suppression of the PKLR gene and activation of multiple glycolytic genes, such as PKM1/2. Pharmacological inhibition of glycolysis by PKM2 inhibitor, Shikonin, significantly suppressed leukemic cell proliferation. FLI1 directly binds to the PKLR promoter, leading to the suppression of this inhibitor of glycolysis. In accordance, shRNA-mediated depletion of PKLR in leukemic HEL cells expressing high levels of FLI1 accelerated leukemia proliferation, pointing for the first time to its tumor suppressor function. PKLR knockdown also led to downregulation of the erythroid markers EPOR, HBA1, and HBA2 and suppression of erythroid differentiation. Interestingly, silencing of PKLR in HEL cells significantly increased FLI1 expression, which was associated with faster proliferation in culture. In FLI1-expressing leukemic cells, lower PKLR expression was associated with higher expression of PKM1 and PKM2, which promote aerobic glycolysis. Finally, injection of pyruvate, a known inhibitor of glycolysis, into leukemia mice significantly suppressed leukemogenesis. These results demonstrate that FLI1 promotes leukemia in part by inducing glycolysis, implicates PKLR in erythroid differentiation, and suggests that targeting glycolysis may be an attractive therapeutic strategy for cancers driven by FLI1 overexpression.

The emerging role of PKM in keratinocyte homeostasis and pathophysiology

Increased aerobic glycolysis in keratinocytes has been reported as a hallmark of skin diseases while its pharmacological inhibition restores keratinocyte homeostasis. Pyruvate kinase muscle (PKM) isoforms are key enzymes in the glycolytic pathway and, therefore, an attractive therapeutic target. Simon Nold and colleagues used CRISPR/Cas9-mediated gene editing to investigate the outcomes of PKM splicing perturbations and specific PKM1 or PKM2 deficiency in human HaCaT keratinocytes. Collectively, the study demonstrated different effects of PKM1 or PKM2 depletion on the reciprocal PKM isoform and on keratinocyte gene expression, metabolism and proliferation. Findings from this study provide novel insights into the role of PKM in keratinocyte homeostasis, warranting additional investigations into the underlying molecular mechanisms and potential therapeutic applications.

FSTL1 promotes liver fibrosis by reprogramming macrophage function through modulating the intracellular function of PKM2

OBJECTIVE

Follistatin-like protein 1 (FSTL1) is widely recognised as a secreted glycoprotein, but its role in modulating macrophage-related inflammation during liver fibrosis has not been documented. Herein, we aimed to characterise the roles of macrophage FSTL1 in the development of liver fibrosis.

DESIGN

Expression analysis was conducted with human liver samples obtained from 33 patients with liver fibrosis and 18 individuals without fibrosis serving as controls. Myeloid-specific FSTL1-knockout (FSTL1^M-KO) mice were constructed to explore the function and mechanism of macrophage FSTL1 in 3 murine models of liver fibrosis induced by carbon tetrachloride injection, bile duct ligation or a methionine-deficient and choline-deficient diet.

RESULTS

FSTL1 expression was significantly elevated in macrophages from fibrotic livers of both humans and mice. Myeloid-specific FSTL1 deficiency effectively attenuated the progression of liver fibrosis. In FSTL1^M-KO mice, the microenvironment that developed during liver fibrosis showed relatively less inflammation, as demonstrated by attenuated infiltration of monocytes/macrophages and neutrophils and decreased expression of proinflammatory factors. FSTL1^M-KO macrophages exhibited suppressed proinflammatory M1 polarisation and nuclear factor kappa B pathway activation in vivo and in vitro. Furthermore, this study showed that, through its FK domain, FSTL1 bound directly to the pyruvate kinase M2 (PKM2). Interestingly, FSTL1 promoted PKM2 phosphorylation and nuclear translocation, reduced PKM2 ubiquitination to enhance PKM2-dependent glycolysis and increased M1 polarisation. Pharmacological activation of PKM2 (DASA-58) partially countered FSTL1-mediated glycolysis and inflammation.

CONCLUSION

Macrophage FSTL1 promotes the progression of liver fibrosis by inducing M1 polarisation and inflammation based on the intracellular PKM2 reprogramming function of macrophages.

The roles of metabolic profiles and intracellular signaling pathways of tumor microenvironment cells in angiogenesis of solid tumors

Innate and adaptive immune cells patrol and survey throughout the human body and sometimes reside in the tumor microenvironment (TME) with a variety of cell types and nutrients that may differ from those in which they developed. The metabolic pathways and metabolites of immune cells are rooted in cell physiology, and not only provide nutrients and energy for cell growth and survival but also influencing cell differentiation and effector functions. Nowadays, there is a growing awareness that metabolic processes occurring in cancer cells can affect immune cell function and lead to tumor immune evasion and angiogenesis. In order to safely treat cancer patients and prevent immune checkpoint blockade-induced toxicities and autoimmunity, we suggest using anti-angiogenic drugs solely or combined with Immune checkpoint blockers (ICBs) to boost the safety and effectiveness of cancer therapy. As a consequence, there is significant and escalating attention to discovering techniques that target metabolism as a new method of cancer therapy. In this review, a summary of immune-metabolic processes and their potential role in the stimulation of intracellular signaling in TME cells that lead to tumor angiogenesis, and therapeutic applications is provided. Video abstract.

The Role of WRAP53 in Cell Homeostasis and Carcinogenesis Onset

The WD repeat containing antisense to TP53 (WRAP53) gene codifies an antisense transcript for tumor protein p53 (TP53), stabilization (WRAP53α), and a functional protein (WRAP53β, WDR79, or TCAB1). The WRAP53β protein functions as a scaffolding protein that is important for telomerase localization, telomere assembly, Cajal body integrity, and DNA double-strand break repair. WRAP53β is one of many proteins known for containing WD40 domains, which are responsible for mediating a variety of cell interactions. Currently, WRAP53 overexpression is considered a biomarker for a diverse subset of cancer types, and in this study, we describe what is known about WRAP53β's multiple interactions in cell protein trafficking, Cajal body formation, and DNA double-strand break repair and its current perspectives as a biomarker for cancer.

A functional analysis of 180 cancer cell lines reveals conserved intrinsic metabolic programs

Cancer cells reprogram their metabolism to support growth and invasion. While previous work has highlighted how single altered reactions and pathways can drive tumorigenesis, it remains unclear how individual changes propagate at the network level and eventually determine global metabolic activity. To characterize the metabolic lifestyle of cancer cells across pathways and genotypes, we profiled the intracellular metabolome of 180 pan-cancer cell lines grown in identical conditions. For each cell line, we estimated activity for 49 pathways spanning the entirety of the metabolic network. Upon clustering, we discovered a convergence into only two major metabolic types. These were functionally confirmed by ¹³ C-flux analysis, lipidomics, and analysis of sensitivity to perturbations. They revealed that the major differences in cancers are associated with lipid, TCA cycle, and carbohydrate metabolism. Thorough integration of these types with multiomics highlighted little association with genetic alterations but a strong association with markers of epithelial-mesenchymal transition. Our analysis indicates that in absence of variations imposed by the microenvironment, cancer cells adopt distinct metabolic programs which serve as vulnerabilities for therapy.

Druggable Metabolic Vulnerabilities Are Exposed and Masked during Progression to Castration Resistant Prostate Cancer

There is an urgent need for exploring new actionable targets other than androgen receptor to improve outcome from lethal castration-resistant prostate cancer. Tumor metabolism has reemerged as a hallmark of cancer that drives and supports oncogenesis. In this regard, it is important to understand the relationship between distinctive metabolic features, androgen receptor signaling, genetic drivers in prostate cancer, and the tumor microenvironment (symbiotic and competitive metabolic interactions) to identify metabolic vulnerabilities. We explore the links between metabolism and gene regulation, and thus the unique metabolic signatures that define the malignant phenotypes at given stages of prostate tumor progression. We also provide an overview of current metabolism-based pharmacological strategies to be developed or repurposed for metabolism-based therapeutics for castration-resistant prostate cancer.

PHB2 Maintains the Contractile Phenotype of VSMCs by Counteracting PKM2 Splicing

BACKGROUND

Phenotypic transition of vascular smooth muscle cells (VSMCs) accounts for the pathogenesis of a variety of vascular diseases during the early stage. Recent studies indicate the metabolic reprogramming may be involved in VSMC phenotypic transition. However, the definite molecules that link energy metabolism to distinct VSMC phenotype remain elusive.

METHODS

A carotid artery injury model was used to study postinjury neointima formation as well as VSMC phenotypic transition in vivo. RNA-seq analysis, cell migration assay, collagen gel contraction assay, wire myography assay, immunoblotting, protein interactome analysis, co-immunoprecipitation, and mammalian 2-hybrid assay were performed to clarify the phenotype and elucidate the molecular mechanisms.

RESULTS

We collected cell energy-regulating genes by using Gene Ontology annotation and applied RNA-Seq analysis of transforming growth factor-β or platelet-derived growth factor BB stimulated VSMCs. Six candidate genes were overlapped from energy metabolism-related genes and genes reciprocally upregulated by transforming growth factor-β and downregulated by platelet-derived growth factor BB. Among them, prohibitin 2 has been reported to regulate mitochondrial oxidative phosphorylation. Indeed, prohibitin 2-deficient VSMCs lost the contractile phenotype as evidenced by reduced contractile proteins. Consistently, Phb2^SMCKO mice were more susceptible to postinjury VSMC proliferation and neointima formation compared with Phb2^flox/flox mice. Further protein interactome analysis, co-immunoprecipitation, and mammalian 2-hybrid assay revealed that prohibitin 2, through its C-terminus, directly interacts with hnRNPA1, a key modulator of pyruvate kinase M1/2 (PKM) mRNA splicing that promotes PKM2 expression and glycolysis. Prohibitin 2 deficiency facilitated PKM1/2 mRNA splicing and reversion from PKM1 to PKM2, and enhanced glycolysis in VSMCs. Blocking prohibitin 2-hnRNPA1 interaction resulted in increased PKM2 expression, enhanced glycolysis, repressed contractile marker genes expression in VSMCs, as well as aggravated postinjury neointima formation in vivo.

CONCLUSIONS

Prohibitin 2 maintains VSMC contractile phenotype by interacting with hnRNPA1 to counteract hnRNPA1-mediated PKM alternative splicing and glucose metabolic reprogramming.

Single-Cell Transcriptomic Profiling in Inherited Retinal Degeneration Reveals Distinct Metabolic Pathways in Rod and Cone Photoreceptors

The cellular mechanisms underlying hereditary photoreceptor degeneration are still poorly understood. The aim of this study was to systematically map the transcriptional changes that occur in the degenerating mouse retina at the single cell level. To this end, we employed single-cell RNA-sequencing (scRNA-seq) and retinal degeneration-1 (rd1) mice to profile the impact of the disease mutation on the diverse retinal cell types during early post-natal development. The transcriptome data allowed to annotate 43,979 individual cells grouped into 20 distinct clusters. We further characterized cluster-specific metabolic and biological changes in individual cell types. Our results highlight Ca2+-signaling as relevant to hereditary photoreceptor degeneration. Although metabolic reprogramming in retina, known as the 'Warburg effect', has been documented, further metabolic changes were noticed in rd1 mice. Such metabolic changes in rd1 mutation was likely regulated through mitogen-activated protein kinase (MAPK) pathway. By combining single-cell transcriptomes and immunofluorescence staining, our study revealed cell type-specific changes in gene expression, as well as interplay between Ca2+-induced cell death and metabolic pathways.

Recent progress of the tumor microenvironmental metabolism in cervical cancer radioresistance

Radiotherapy is widely used as an indispensable treatment option for cervical cancer patients. However, radioresistance always occurs and has become a big obstacle to treatment efficacy. The reason for radioresistance is mainly attributed to the high repair ability of tumor cells that overcome the DNA damage caused by radiotherapy, and the increased self-healing ability of cancer stem cells (CSCs). Accumulating findings have demonstrated that the tumor microenvironment (TME) is closely related to cervical cancer radioresistance in many aspects, especially in the metabolic processes. In this review, we discuss radiotherapy in cervical cancer radioresistance, and focus on recent research progress of the TME metabolism that affects radioresistance in cervical cancer. Understanding the mechanism of metabolism in cervical cancer radioresistance may help identify useful therapeutic targets for developing novel therapy, overcome radioresistance and improve the efficacy of radiotherapy in clinics and quality of life of patients.

Dual roles of β-arrestin 1 in mediating cell metabolism and proliferation in gastric cancer

β-Arrestin 1 (ARRB1) has been recognized as a multifunctional adaptor protein in the last decade, beyond its original role in desensitizing G protein-coupled receptor signaling. Here, we identify that ARRB1 plays essential roles in mediating gastric cancer (GC) cell metabolism and proliferation, by combining cohort analysis and functional investigation using patient-derived preclinical models. Overexpression of ARRB1 was associated with poor outcome of GC patients and knockdown of ARRB1 impaired cell proliferation both ex vivo and in vivo. Intriguingly, ARRB1 depicted diverse subcellular localizations during a passage of organoid cultures (7 d) to exert dual functions. Further analysis revealed that nuclear ARRB1 binds with transcription factor E2F1 triggering up-regulation of proliferative genes, while cytoplasmic ARRB1 modulates metabolic flux by binding with the pyruvate kinase M2 isoform (PKM2) and hindering PKM2 tetramerization, which reduces pyruvate kinase activity and leads to cellular metabolism shifts from oxidative phosphorylation to aerobic glycolysis. As ARRB1 localization was shown mostly in the cytoplasm in human GC samples, therapeutic potential of the ARRB1-PKM2 axis was tested, and we found tumor proliferation could be attenuated by the PKM2 activator DASA-58, especially in ARRB1^high organoids. Together, the data in our study highlight a spatiotemporally dependent role of ARRB1 in mediating GC cell metabolism and proliferation and implies reactivating PKM2 may be a promising therapeutic strategy in a subset of GC patients.

Aurora A-mediated pyruvate kinase M2 phosphorylation promotes biosynthesis with glycolytic metabolites and tumor cell cycle progression

Cancer cells have distinctive demands for intermediates from glucose metabolism for biosynthesis and energy in different cell cycle phases. However, how cell cycle regulators and glycolytic enzymes coordinate to orchestrate the essential metabolic processes are still poorly characterized. Here, we report a novel interaction between the mitotic kinase, Aurora A, and the glycolytic enzyme, pyruvate kinase M2 (PKM2), in the interphase of the cell cycle. We found Aurora A–mediated phosphorylation of PKM2 at threonine 45. This phosphorylation significantly attenuated PKM2 enzymatic activity by reducing its tetramerization and also promoted glycolytic flux and the branching anabolic pathways. Replacing the endogenous PKM2 with a nonphosphorylated PKM2 T45A mutant inhibited glycolysis, glycolytic branching pathways, and tumor growth in both in vitro and in vivo models. Together, our study revealed a new protumor function of Aurora A through modulating a rate-limiting glycolytic enzyme, PKM2, mainly during the S phase of the cell cycle. Our findings also showed that although both Aurora A and Aurora B kinase phosphorylate PKM2 at the same residue, the spatial and temporal regulations of the specific kinase and PKM2 interaction are context dependent, indicating intricate interconnectivity between cell cycle and glycolytic regulators.

The function and mechanism of lactate and lactylation in tumor metabolism and microenvironment

Lactate is an end product of glycolysis. Owing to the lactate shuttle concept introduced in the early 1980s, increasing researchers indicate lactate as a critical energy source for mitochondrial respiration and as a precursor of gluconeogenesis. Lactate also acts as a multifunctional signaling molecule through receptors expressed in various cells, resulting in diverse biological consequences including decreased lipolysis, immune regulation, and anti-inflammation wound healing, and enhanced exercise performance in association with the gut microbiome. Furthermore, increasing evidence reveals that lactate contributes to epigenetic gene regulation by lactylating lysine residues of histones, which accounts for its key role in immune modulation and maintenance of homeostasis. Here, we summarize the function and mechanism of lactate and lactylation in tumor metabolism and microenvironment.

MicroRNA and Metabolic Profiling of a Primary Ovarian Neuroendocrine Carcinoma Pulmonary-Type Reveals a High Degree of Similarity with Small Cell Lung Cancer

Small cell neuroendocrine carcinoma is most frequently found in the lung (SCLC), but it has been also reported, albeit with a very low incidence, in the ovary. Here, we analyze a case of primary small cell carcinoma of the ovary of pulmonary type (SCCOPT), a rare and aggressive tumor with poor prognosis, whose biology and molecular features have not yet been thoroughly investigated. The patient affected by SCCOPT had a residual tumor following chemotherapy which displayed pronounced similarity with neuroendocrine tumors and lung cancer in terms of its microRNA expression profile and mTOR-downstream activation. By analyzing the metabolic markers of the neoplastic lesion, we established a likely glycolytic signature. In conclusion, this in-depth characterization of SCCOPT could be useful for future diagnoses, possibly aided by microRNA profiling, allowing clinicians to adopt the most appropriate therapeutic strategy.

Small Extracellular Vesicles and Their Involvement in Cancer Resistance: An Up-to-Date Review

In recent years, tremendous progress has been made in understanding the roles of extracellular vesicles (EVs) in cancer. Thanks to advancements in molecular biology, it has been found that the fraction of EVs called exosomes or small EVs (sEVs) modulates the sensitivity of cancer cells to chemotherapeutic agents by delivering molecularly active non-coding RNAs (ncRNAs). An in-depth analysis shows that two main molecular mechanisms are involved in exosomal modified chemoresistance: (1) translational repression of anti-oncogenes by exosomal microRNAs (miRs) and (2) lack of translational repression of oncogenes by sponging of miRs through long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). At the cellular level, these processes increase the proliferation and survival of cancer cells and improve their ability to metastasize and resist apoptosis. In addition, studies in animal models have shown enhancing tumor size under the influence of exosomal ncRNAs. Ultimately, exosomal ncRNAs are responsible for clinically significant chemotherapy failures in patients with different types of cancer. Preliminary data have also revealed that exosomal ncRNAs can overcome chemotherapeutic agent resistance, but the results are thoroughly fragmented. This review presents how exosomes modulate the response of cancer cells to chemotherapeutic agents. Understanding how exosomes interfere with chemoresistance may become a milestone in developing new therapeutic options, but more data are still required.

Prognostic value of glycolysis markers in pancreatic cancer: A systematic review and meta-analysis

Introduction

Previous studies have investigated the prognostic significance of glycolysis markers in pancreatic cancer; however, conclusions from these studies are still controversial.

Methods

PubMed, Embase, and Web of Science were systematically searched to investigate the prognostic role of glycolysis markers in pancreatic cancer up to May 2022. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) related to overall survival (OS), disease free survival (DFS), recurrence-free survival (RFS), and distant metastasis-free survival (DMFS) were calculated using the STATA 12.0 software.

Results

A total of 28 studies comprising 2010 patients were included in this meta-analysis. High expression of the five glycolysis markers was correlated with a poorer OS (HR = 1.72, 95% CI: 1.34-2.22), DFS (HR = 3.09, 95% CI: 1.91-5.01), RFS (HR = 1.73, 95% CI: 1.21-2.48) and DMFS (HR = 2.60, 95% CI: 1.09-6.20) in patients with pancreatic cancer. In subgroup analysis, it was shown that higher expression levels of the five glycolysis markers were related to a poorer OS in Asians (HR = 1.85, 95% CI: 1.46-2.35, P < 0.001) and Caucasians (HR = 1.97, 95% CI: 1.40-2.77, P < 0.001). Besides, analysis based on the expression levels of specific glycolysis markers demonstrated that higher expression levels of GLUT1 (HR = 2.11, 95% CI: 1.58-2.82, P < 0.001), MCT4 (HR = 2.26, 95% CI: 1.36-3.76, P = 0.002), and ENO1 (HR = 2.16, 95% CI: 1.28-3.66, P =0.004) were correlated with a poorer OS in patients with pancreatic cancer.

Conclusions

High expression of the five glycolysis markers are associated with poorer OS, DFS, RFS and DMFS in patients with pancreatic cancer, indicating that the glycolysis markers could be potential prognostic predictors and therapeutic targets in pancreatic cancer.

In-Silico Analysis of Phytocompounds of Olea europaea as Potential Anti-Cancer Agents to Target PKM2 Protein

Globally, cancer is the second leading cause of mortality and morbidity. The growth and development of cancer are extremely complex. It is caused by a variety of pathways and involves various types of enzymes. Pyruvate kinase M2 (PKM2) is an isoform of pyruvate kinase, that catalyses the last steps of glycolysis to produce energy. PKM2 is relatively more expressed in tumour cells where it tends to exist in a dimer form. Various medicinal plants are available that contain a variety of micronutrients to combat against different cancers. The phytocompounds of the olive tree (Olea europaea) leaves play an important role in inhibiting the proliferation of several cancers. In this study, the phytocompounds of olive leaf extract (OLE) were studied using various in silico tools, such as pkCSM software to predict ADMET properties and PASS Online software to predict anticancer activity. However, the molecular docking study provided the binding energies and inhibition constant and confirmed the interaction between PKM2 and the ligands. The dynamic behaviour, conformational changes, and stability between PKM2 and the top three hit compounds (Verbascoside (Ver), Rutin (Rut), and Luteolin_7_O_glucoside (Lut)) are studied by MD simulations.

The roles of glycolysis in osteosarcoma

Metabolic reprogramming is of great significance in the progression of various cancers and is critical for cancer progression, diagnosis, and treatment. Cellular metabolic pathways mainly include glycolysis, fat metabolism, glutamine decomposition, and oxidative phosphorylation. In cancer cells, reprogramming metabolic pathways is used to meet the massive energy requirement for tumorigenesis and development. Metabolisms are also altered in malignant osteosarcoma (OS) cells. Among reprogrammed metabolisms, alterations in aerobic glycolysis are key to the massive biosynthesis and energy demands of OS cells to sustain their growth and metastasis. Numerous studies have demonstrated that compared to normal cells, glycolysis in OS cells under aerobic conditions is substantially enhanced to promote malignant behaviors such as proliferation, invasion, metastasis, and drug resistance of OS. Glycolysis in OS is closely related to various oncogenes and tumor suppressor genes, and numerous signaling pathways have been reported to be involved in the regulation of glycolysis. In recent years, a vast number of inhibitors and natural products have been discovered to inhibit OS progression by targeting glycolysis-related proteins. These potential inhibitors and natural products may be ideal candidates for the treatment of osteosarcoma following hundreds of preclinical and clinical trials. In this article, we explore key pathways, glycolysis enzymes, non-coding RNAs, inhibitors, and natural products regulating aerobic glycolysis in OS cells to gain a deeper understanding of the relationship between glycolysis and the progression of OS and discover novel therapeutic approaches targeting glycolytic metabolism in OS.

DDX39B drives colorectal cancer progression by promoting the stability and nuclear translocation of PKM2

Metastasis is a major cause of colorectal cancer (CRC) mortality, but its molecular mechanisms are still not fully understood. Here, we show that upregulated DDX39B correlates with liver metastases and aggressive phenotypes in CRC. DDX39B is an independent prognostic factor associated with poor clinical outcome in CRC patients. We demonstrate that Sp1 potently activates DDX39B transcription by directly binding to the GC box of the DDX39B promoter in CRC cells. DDX39B overexpression augments the proliferation, migration, and invasion of CRC cells, while the opposite results are obtained in DDX39B-deficient CRC cells. Mechanistically, DDX39B interacts directly with and stabilizes PKM2 by competitively suppressing STUB1-mediated PKM2 ubiquitination and degradation. Importantly, DDX39B recruits importin α5 to accelerate the nuclear translocation of PKM2 independent of ERK1/2-mediated phosphorylation of PKM2, leading to the transactivation of oncogenes and glycolysis-related genes. Consequently, DDX39B enhances glucose uptake and lactate production to activate Warburg effect in CRC. We identify that Arg319 of DDX39B is required for PKM2 binding as well as PKM2 nuclear accumulation and for DDX39B to promote CRC growth and metastasis. In addition, blocking PKM2 nuclear translocation or treatment with glycolytic inhibitor 2-deoxy-D-glucose efficiently abolishes DDX39B-triggered malignant development in CRC. Taken together, our findings uncover a key role for DDX39B in modulating glycolytic reprogramming and aggressive progression, and implicate DDX39B as a potential therapeutic target in CRC.

Overexpressed PKM2 promotes macrophage phagocytosis and atherosclerosis

BACKGROUND

The expression of pyruvate kinase muscle 2 (PKM2) is augmented in macrophages of patients with atherosclerotic coronary artery disease. The role of PKM2 in atherosclerosis is to be determined.

METHODS

Global and myeloid cell-specific PKM2 knock-in mice with ApoE^-/- background (ApoE^-/- , PKM2^KI/KI and Lyz2-cre, ApoE^-/- , and PKM2^flox/flox ) were produced to evaluate the clinical significance of PKM2 in atherosclerosis development. Wild-type and PKM2 knock-in macrophages were isolated to assess the function of PKM2 in macrophage phagocytosis. Atherosclerotic mice were treated with PKM2 inhibitor shikonin (SKN) to evaluate the therapeutic potential of PKM2 suppression in atherosclerosis.

RESULTS

Oxidized low-density lipoprotein (oxLDL) upregulated PKM2 in macrophages. PKM2 in return promoted the uptake of oxLDL by macrophages. Overexpressed PKM2 accelerated atherosclerosis in mice. SKN blocked the progress of mouse atherosclerosis.

CONCLUSIONS

PKM2 accelerates macrophage phagocytosis and atherosclerosis. Targeting PKM2 is a potential therapy for atherosclerosis.

lncRNA HITT Inhibits Lactate Production by Repressing PKM2 Oligomerization to Reduce Tumor Growth and Macrophage Polarization

Lactic acid acidifies the tumor microenvironment and promotes multiple critical oncogenic processes, including immune evasion. Pyruvate kinase M2 (PKM2) is a dominant form of pyruvate kinase (PK) expressed in cancers that plays essential roles in metabolic reprograming and lactate production, rendering it as an attractive therapeutic target of cancer. However, the mechanism underlying PKM2 regulation remains unclear. Here, we show that long noncoding RNA (lncRNA) HIF-1α inhibitor at transcription level (HITT) inhibits lactate production in a PKM2-dependent manner. Mechanistically, it physically interacts with PKM2 mapped to a region that has been involved in both dimer (less-active) and tetramer (more-active) formation, inhibiting PKM2 oligomerization and leading to dramatic reduction of PK activity. Under glucose starvation, HITT was reduced as a result of miR-106 induction, which subsequently facilitates PKM2 oligomerization and increases vulnerability to apoptosis under glucose starvation stress. In addition, the interaction also reduces lactate secretion from cancer cells, which subsequently polarizes macrophages toward an M2-like anti-inflammatory phenotype and thus possibly contributes to immune escape in vivo. This study highlights an important role of an lncRNA in regulating PKM2 activity and also reveals a metabolic regulatory effect of PKM2 on macrophage polarization.

MiR-4461 Inhibits Tumorigenesis of Renal Cell Carcinoma by Targeting PPP1R3C

Background: Renal cell carcinoma (RCC) is one of the most common and malignant tumors in the urinary system. The aim of this research was to investigate the mechanism and clinical significance of miR-4461 in the RCC progression. Materials and Methods: Twenty-eight (28) paired RCC tissue samples and adjacent nontumor tissue samples, as well as RCC cell lines were used to measure the expression of miR-4461 and protein phosphatase 1 regulatory subunit 3C (PPP1R3C) transcript by real-time quantitative PCR. The target relationship between miR-4461 and PPP1R3C was predicted by TargetScan and further verified by dual-luciferase reporter gene assay and RNA pull-down assay. Cell Counting Kit-8 (CCK-8) assay and BrdU ELISA assay were performed to measure RCC cell viability and proliferation. In addition, caspase-3 activity assay and cell adhesion assay were implemented to measure RCC cell apoptosis and adhesion. Results: MiR-4461 was lowly expressed both in RCC tissues and cells, while upregulated PPP1R3C was tested in RCC tissues and cells. In addition, miR-4461 was validated to directly target PPP1R3C, thereby negatively regulating PPP1R3C. Particularly, miR-4461 exerted a clear inhibitory effect on the malignant phenotypes of RCC cells by binding and inhibiting PPP1R3C. Conclusion: MiR-4461, which served as a tumor suppressor, inhibited RCC progression by targeting and downregulating PPP1R3C.

Tumor-Treating Fields in Glioblastomas: Past, Present, and Future

Simple Summary

Glioblastoma (GBM) is the most common malignant primary brain tumor. Although the standard of care, including maximal resection, concurrent radiotherapy with temozolomide (TMZ), and adjuvant TMZ, has largely improved the prognosis of these patients, the 5-year survival rate is still < 10%. Tumor-treating fields (TTFields), a noninvasive anticancer therapeutic modality, has been rising as a fourth treatment option for GBMs, as confirmed by recent milestone large-scale phase 3 randomized trials and subsequent real-world data, elongating patient overall survival from 16 months to 21 months. However, the mechanisms of antitumor efficacy, its clinical safety, and potential benefits when combined with other treatment modalities are far from completely elucidated. As an increasing number of studies have recently been published on this topic, we conducted this updated, comprehensive review to establish an objective understanding of the mechanism of action, efficacy, safety, clinical concerns, and future perspectives of TTFields.

Abstract

Tumor-treating fields (TTFields), a noninvasive and innovative therapeutic approach, has emerged as the fourth most effective treatment option for the management of glioblastomas (GBMs), the most deadly primary brain cancer. According to on recent milestone randomized trials and subsequent observational data, TTFields therapy leads to substantially prolonged patient survival and acceptable adverse events. Clinical trials are ongoing to further evaluate the safety and efficacy of TTFields in treating GBMs and its biological and radiological correlations. TTFields is administered by delivering low-intensity, intermediate-frequency, alternating electric fields to human GBM function through different mechanisms of action, including by disturbing cell mitosis, delaying DNA repair, enhancing autophagy, inhibiting cell metabolism and angiogenesis, and limiting cancer cell migration. The abilities of TTFields to strengthen intratumoral antitumor immunity, increase the permeability of the cell membrane and the blood–brain barrier, and disrupt DNA-damage-repair processes make it a promising therapy when combined with conventional treatment modalities. However, the overall acceptance of TTFields in real-world clinical practice is still low. Given that increasing studies on this promising topic have been published recently, we conducted this updated review on the past, present, and future of TTFields in GBMs.