Inhibition of Pyruvate Kinase M2 Markedly Reduces Chemoresistance of Advanced Bladder Cancer to Cisplatin

Unveiling the anticancer potential of plumbagin: targeting pyruvate kinase M2 to induce oxidative stress and apoptosis in hepatoma cells

Pyruvate kinase M2 (PKM2), a crucial enzyme in the glycolysis pathway, is commonly documented as being overexpressed in cancer cells. Inhibiting PKM2, a strategy to mitigate cancer cell-dependent glycolysis, has demonstrated efficacy in anticancer treatment. In this study, plumbagin, which was originally extracted from the plant Plumbago zeylanica L., was discovered as a novel PKM2 inhibitor and it could bind to PKM2 to inhibit the enzymatic activity. Treatment with plumbagin in HepG2 cells resulted in the decrease of PKM2 expression, which in turn reduced the protein kinase function. The mRNA levels of its downstream genes, such as LDHA and MYC, were suppressed. Additionally, plumbagin downregulated the expression of intracellular antioxidant proteins, which induced oxidative stress and mitochondrial damage, ultimately triggering apoptosis. Moreover, plumbagin also reduced the migration and proliferation of HepG2 cells. This study offered valuable insights into the molecular mechanism of plumbagin and advocated for the exploration of PKM2 inhibitors as viable possibilities for anticancer therapeutics.

Immunoglobulin Superfamily Containing Leucine-Rich Repeat (ISLR) Serves as a Redox Sensor That Modulates Antioxidant Capacity by Suppressing Pyruvate Kinase Isozyme M2 Activity

Cells defend against oxidative stress by enhancing antioxidant capacity, including stress-activated metabolic alterations, but the underlying intracellular signaling mechanisms remain unclear. This paper reports that immunoglobulin superfamily containing leucine-rich repeat (ISLR) functions as a redox sensor that responds to reactive oxygen species (ROS) stimulation and modulates the antioxidant capacity by suppressing pyruvate kinase isozyme M2 (PKM2) activity. Following oxidative stress, ISLR perceives ROS stimulation through its cysteine residue 19, and rapidly degrades in the autophagy-lysosome pathway. The downregulated ISLR enhances the antioxidant capacity by promoting the tetramerization of PKM2, and then enhancing the pyruvate kinase activity, PKM2-mediated glycolysis is crucial to the ISLR-mediated antioxidant capacity. In addition, our results demonstrated that, in triple-negative breast cancer, cisplatin treatment reduced the level of ISLR, and PKM2 inhibition sensitizes tumors to cisplatin by enhancing ROS production; and argued that PKM2 inhibition can synergize with cisplatin to limit tumor growth. Our results demonstrate a molecular mechanism by which cells respond to oxidative stress and modulate the redox balance.

Cisplatin-Resistant Urothelial Bladder Cancer Cells Undergo Metabolic Reprogramming beyond the Warburg Effect

Advanced urothelial bladder cancer (UBC) patients are tagged by a dismal prognosis and high mortality rates, mostly due to their poor response to standard-of-care platinum-based therapy. Mediators of chemoresistance are not fully elucidated. This work aimed to study the metabolic profile of advanced UBC, in the context of cisplatin resistance. Three isogenic pairs of parental cell lines (T24, HT1376 and KU1919) and the matching cisplatin-resistant (R) sublines were used. A set of functional assays was used to perform a metabolic screening on the cells. In comparison to the parental sublines, a tendency was observed towards an exacerbated glycolytic metabolism in the cisplatin-resistant T24 and HT1376 cells; this glycolytic phenotype was particularly evident for the HT1376/HT1376R pair, for which the cisplatin resistance ratio was higher. HT1376R cells showed decreased basal respiration and oxygen consumption associated with ATP production; in accordance, the extracellular acidification rate was also higher in the resistant subline. Glycolytic rate assay confirmed that these cells presented higher basal glycolysis, with an increase in proton efflux. While the results of real-time metabolomics seem to substantiate the manifestation of the Warburg phenotype in HT1376R cells, a shift towards distinct metabolic pathways involving lactate uptake, lipid biosynthesis and glutamate metabolism occurred with time. On the other hand, KU1919R cells seem to engage in a metabolic rewiring, recovering their preference for oxidative phosphorylation. In conclusion, cisplatin-resistant UBC cells seem to display deep metabolic alterations surpassing the Warburg effect, which likely depend on the molecular signature of each cell line.

[RBMX overexpression inhibits proliferation, migration, invasion and glycolysis of human bladder cancer cells by downregulating PKM2]

OBJECTIVE

To investigate the role of RNA-binding motif protein X-linked (RBMX) in regulating the proliferation, migration, invasion and glycolysis in human bladder cancer cells.

METHODS

A lentivirus vectors system and RNA interference technique were used to construct bladder cancer 1376 and UC-3 cell models with RBMX overexpression and knockdown, respectively, and successful cell modeling was verified using RT-qPCR and Western blotting. Proliferation and colony forming ability of the cells were evaluated using EdU assay and colony-forming assay, and cell migration and invasion abilities were determined using Transwell experiment. The expressions of glycolysis-related proteins M1 pyruvate kinase (PKM1) and M2 pyruvate kinase (PKM2) were detected using Western blotting. The effects of RBMX overexpression and knockdown on glycolysis in the bladder cancer cells were assessed using glucose and lactic acid detection kits.

RESULTS

RT-qPCR and Western blotting confirmed successful construction of 1376 and UC-3 cell models with RBMX overexpression and knockdown. RBMX overexpression significantly inhibited the proliferation, clone formation, migration and invasion of bladder cancer cells, while RBMX knockdown produced the opposite effects. Western blotting results showed that RBMX overexpression increased the expression of PKM1 and decreased the expression of PKM2, while RBMX knockdown produced the opposite effects. Glucose consumption and lactate production levels were significantly lowered in the cells with RBMX overexpression (P < 0.05) but increased significantly following RBMX knockdown (P < 0.05).

CONCLUSION

RBMX overexpression inhibits bladder cancer progression and lowers glycolysis level in bladder cancer cells by downregulating PKM2 expression, suggesting the potential of RBMX as a molecular target for diagnosis and treatment of bladder cancer.

β-Arrestin2 promotes docetaxel resistance of castration-resistant prostate cancer via promoting hnRNP A1-mediated PKM2 alternative splicing

PURPOSE

To investigate the influence of β-arrestin2 on the docetaxel resistance in castration-resistant prostate cancer (CRPC) and elucidate the underlying molecular mechanisms.

METHODS

PC3 and DU145 cells with stable β-arrestin2 overexpression and C4-2 cells with stable β-arrestin2 knockdown, were constructed via using lentivirus and puromycin selection. MTT and colony formation assays were carried out to investigate the effect of β-arrestin2 expression on the docetaxel resistance of CRPC cells. Glycolysis analysis was used to assess the glycolytic capacity modulated by β-arrestin2. GO enrichment analysis, gene set enrichment analysis and Spearman correlation test were carried out to explore the potential biological function and mechanism via using public data from GEO and TCGA. The expressions of PKM2, Phospho-PKM2, Phospho-ERK1/2 and hnRNP A1 were detected by western blot. Functional blocking experiments were carried out to confirm the roles of PKM2 and hnRNP A1 in the regulation of β-arrestin2's biological functions via silencing PKM2 or hnRNP A1 expression in cells with stable β-arrestin2 overexpression. Finally, nude mice xenograft models were established to confirm the experimental results of cell experiments.

RESULTS

β-Arrestin2 significantly decreased the sensitivity of CRPC cells to docetaxel stimulation, through enhancing the phosphorylation and expression of PKM2. Additionally, β-arrestin2 increased PKM2 phosphorylation via the ERK1/2 signaling pathway and induced PKM2 expression in a post-transcriptional manner through an hnRNP A1-dependent PKM alternative splicing mechanism, rather than by inhibiting its ubiquitination degradation.

CONCLUSION

Our findings indicate that the β-arrestin2/hnRNP A1/PKM2 pathway could be a promising target for treating docetaxel-resistant CRPC.

TRAF6 promotes chemoresistance to paclitaxel of triple negative breast cancer via regulating PKM2-mediated glycolysis

Ample evidence reveals that glycolysis is crucial to tumor progression; however, the underlying mechanism of its drug resistance is still worth being further explored. TRAF6, an E3 ubiquitin ligase, is well recognized to overexpress in various types of cancer, which predicts a poor prognosis. In our study, we discovered that TRAF6 was expressed more significantly in the case of triple-negative breast cancer (TNBC) than in other of breast cancers, promoting chemoresistance to paclitaxel; that inhibited TRAF6 expression in the chemoresistant TNBC (TNBC-CR) cells enhanced the sensitivity by decreasing glucose uptake and lactate production; that TRAF6 regulated glycolysis and facilitated chemoresistance via binding directly to PKM2; and that overexpressing PKM2 in the TNBC-CR cells with TRAF6 knocked down regained significantly TRAF6-dependent drug resistance and glycolysis. Additionally, we verified that TRAF6 could facilitate PKM2-mediated glycolysis and chemoresistance in animal models and clinical tumor tissues. Thus, we identified the novel function of TRAF6 to promote glycolysis and drug resistance in TNBC with the regulation of PKM2, which could provide a potential molecular target for TNBC treatment.

Curcuminoids as Anticancer Drugs: Pleiotropic Effects, Potential for Metabolic Reprogramming and Prospects for the Future

The number of published studies on curcuminoids in cancer research, including its lead molecule curcumin and synthetic analogs, has been increasing substantially during the past two decades. Insights on the diversity of inhibitory effects they have produced on a multitude of pathways involved in carcinogenesis and tumor progression have been provided. As this wealth of data was obtained in settings of various experimental and clinical data, this review first aimed at presenting a chronology of discoveries and an update on their complex in vivo effects. Secondly, there are many interesting questions linked to their pleiotropic effects. One of them, a growing research topic, relates to their ability to modulate metabolic reprogramming. This review will also cover the use of curcuminoids as chemosensitizing molecules that can be combined with several anticancer drugs to reverse the phenomenon of multidrug resistance. Finally, current investigations in these three complementary research fields raise several important questions that will be put among the prospects for the future research related to the importance of these molecules in cancer research.

Alternative splicing in bladder cancer: potential strategies for cancer diagnosis, prognosis, and treatment

Bladder cancer is the most common malignancy of the urinary tract worldwide. The therapeutic options to tackle this disease comprise surgery, intravesical or systemic chemotherapy, and immunotherapy. Unfortunately, a wide number of patients ultimately become resistant to these treatments and develop aggressive metastatic disease, presenting a poor prognosis. Therefore, the identification of novel therapeutic approaches to tackle this devastating pathology is urgently needed. However, a significant limitation is that the progression and drug response of bladder cancer is strongly associated with its intrinsic molecular heterogeneity. In this sense, RNA splicing is recently gaining importance as a critical hallmark of cancer since can have a significant clinical value. In fact, a profound dysregulation of the splicing process has been reported in bladder cancer, especially in the expression of certain key splicing variants and circular RNAs with a potential clinical value as diagnostic/prognostic biomarkers or therapeutic targets in this pathology. Indeed, some authors have already evidenced a profound antitumor effect by targeting some splicing factors (e.g., PTBP1), mRNA splicing variants (e.g., PKM2, HYAL4-v1), and circular RNAs (e.g., circITCH, circMYLK), which illustrates new possibilities to significantly improve the management of this pathology. This review represents the first detailed overview of the splicing process and its alterations in bladder cancer, and highlights opportunities for the development of novel diagnostic/prognostic biomarkers and their clinical potential for the treatment of this devastating cancer type. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing RNA in Disease and Development > RNA in Disease.

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.

Cancer metabolism control by natural products: Pyruvate kinase M2 targeting therapeutics

Glycolysis is the primary source of energy for cancer growth and metastasis. The shift in metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis is called the Warburg effect. Cancer progression due to aerobic glycolysis is often associated with the activation of oncogenes or the loss of tumor suppressors. Therefore, inhibition of glycolysis is one of the effective strategies in cancer control. Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme overexpressed in breast, prostate, lung, colorectal, and liver cancers. Here, we discuss published studies regarding PKM2 inhibitors from natural products that are promising drug candidates for cancer therapy. We have highlighted the potential of natural PKM2 inhibitors for various cancer types. Moreover, we encourage researchers to evaluate the combinational effects between natural and synthetic PKM2 inhibitors. Also, further high-quality studies are needed to firmly establish the clinical efficacy of natural products.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Integrated Analysis of Energy Metabolism Signature-Identified Distinct Subtypes of Bladder Urothelial Carcinoma

Background: Bladder urothelial carcinoma (BLCA) is the most common type of bladder cancer. In this study, the correlation between the metabolic status and the outcome of patients with BLCA was evaluated using data from the Cancer Genome Atlas and Gene Expression Omnibus datasets.

Methods: The clinical and transcriptomic data of patients with BLCA were downloaded from the Cancer Genome Atlas and cBioPortal datasets, and energy metabolism-related gene sets were obtained from the Molecular Signature Database. A consensus clustering algorithm was then conducted to classify the patients into two clusters. Tumor prognosis, clinicopathological features, mutations, functional analysis, ferroptosis status analysis, immune infiltration, immune checkpoint-related gene expression level, chemotherapy resistance, and tumor stem cells were analyzed between clusters. An energy metabolism-related signature was further developed and verified using data from cBioPortal datasets.

Results: Two clusters (C1 and C2) were identified using a consensus clustering algorithm based on an energy metabolism-related signature. The patients with subtype C1 had more metabolism-related pathways, different ferroptosis status, higher cancer stem cell scores, higher chemotherapy resistance, and better prognosis. Subtype C2 was characterized by an increased number of advanced BLCA cases and immune-related pathways. Higher immune and stromal scores were also observed for the C2 subtype. A signature containing 16 energy metabolism-related genes was then identified, which can accurately predict the prognosis of patients with BLCA.

Conclusion: We found that the energy metabolism-associated subtypes of BLCA are closely related to the immune microenvironment, immune checkpoint-related gene expression, ferroptosis status, CSCs, chemotherapy resistance, prognosis, and progression of BLCA patients. The established energy metabolism-related gene signature was able to predict survival in patients with BLCA.

Overcoming Radiation Resistance in Gliomas by Targeting Metabolism and DNA Repair Pathways

Gliomas represent a wide spectrum of brain tumors characterized by their high invasiveness, resistance to chemoradiotherapy, and both intratumoral and intertumoral heterogeneity. Recent advances in transomics studies revealed that enormous abnormalities exist in different biological layers of glioma cells, which include genetic/epigenetic alterations, RNA expressions, protein expression/modifications, and metabolic pathways, which provide opportunities for development of novel targeted therapeutic agents for gliomas. Metabolic reprogramming is one of the hallmarks of cancer cells, as well as one of the oldest fields in cancer biology research. Altered cancer cell metabolism not only provides energy and metabolites to support tumor growth, but also mediates the resistance of tumor cells to antitumor therapies. The interactions between cancer metabolism and DNA repair pathways, and the enhancement of radiotherapy sensitivity and assessment of radiation response by modulation of glioma metabolism are discussed herein.

PKM2 Is Essential for Bladder Cancer Growth and Maintenance

Pyruvate kinase M2 (PKM2) has been shown to promote tumorigenesis by facilitating the Warburg effect and enhancing the activities of oncoproteins. However, this paradigm has recently been challenged by studies in which the absence of PKM2 failed to inhibit and instead accelerated tumorigenesis in mouse models. These results seem inconsistent with the fact that most human tumors overexpress PKM2. To further elucidate the role of PKM2 in tumorigenesis, we investigated the effect of PKM2 knockout in oncogenic HRAS-driven urothelial carcinoma. While PKM2 ablation in mouse urothelial cells did not affect tumor initiation, it impaired the growth and maintenance of HRAS-driven tumors. Chemical inhibition of PKM2 recapitulated these effects. Both conditions substantially reduced complex formation of PKM2 with STAT3, their nuclear translocation, and HIF1α- and VEGF-related angiogenesis. The reduction in nuclear STAT3 in the absence of PKM2 also correlated with decreased autophagy and increased apoptosis. Time-controlled, inducible PKM2 overexpression in simple urothelial hyperplasia did not trigger tumorigenesis, while overexpression of PKM2, but not PKM1, in nodular urothelial hyperplasia with angiogenesis strongly accelerated tumorigenesis. Finally, in human patients, PKM2 was overexpressed in low-grade nonmuscle-invasive and high-grade muscle-invasive bladder cancer. Based on these data, PKM2 is not required for tumor initiation but is essential for tumor growth and maintenance by enhancing angiogenesis and metabolic addiction. The PKM2-STAT3-HIF1α/VEGF signaling axis may play a critical role in bladder cancer and may serve as an actionable therapeutic target.

SIGNIFICANCE

Genetic manipulation and pharmacologic inhibition of PKM2 in mouse urothelial lesions highlight its essential role in promoting angiogenesis and metabolic addiction, events indispensable for tumor growth and maintenance.

Targeting HNRNPU to overcome cisplatin resistance in bladder cancer

Purpose

The overall response of cisplatin-based chemotherapy in bladder urothelial carcinoma (BUC) remains unsatisfactory due to the complex pathological subtypes, genomic difference, and drug resistance. The genes that associated with cisplatin resistance remain unclear. Herein, we aimed to identify the cisplatin resistance associated genes in BUC.

Experimental design

The cytotoxicity of cisplatin was evaluated in six bladder cancer cell lines to compare their responses to cisplatin. The T24 cancer cells exhibited the lowest sensitivity to cisplatin and was therefore selected to explore the mechanisms of drug resistance. We performed genome-wide CRISPR screening in T24 cancer cells in vitro, and identified that the gene heterogeneous nuclear ribonucleoprotein U (HNRNPU) was the top candidate gene related to cisplatin resistance. Epigenetic and transcriptional profiles of HNRNPU-depleted cells after cisplatin treatment were analyzed to investigate the relationship between HNRNPU and cisplatin resistance. In vivo experiments were also performed to demonstrate the function of HNRNPU depletion in cisplatin sensitivity.

Results

Significant correlation was found between HNRNPU expression level and sensitivity to cisplatin in bladder cancer cell lines. In the high HNRNPU expressing T24 cancer cells, knockout of HNRNPU inhibited cell proliferation, invasion, and migration. In addition, loss of HNRNPU promoted apoptosis and S-phase arrest in the T24 cells treated with cisplatin. Data from The Cancer Genome Atlas (TCGA) demonstrated that HNRNPU expression was significantly higher in tumor tissues than in normal tissues. High HNRNPU level was negatively correlated with patient survival. Transcriptomic profiling analysis showed that knockout of HNRNPU enhanced cisplatin sensitivity by regulating DNA damage repair genes. Furthermore, it was found that HNRNPU regulates chemosensitivity by affecting the expression of neurofibromin 1 (NF1).

Conclusions

Our study demonstrated that HNRNPU expression is associated with cisplatin sensitivity in bladder urothelial carcinoma cells. Inhibition of HNRNPU could be a potential therapy for cisplatin-resistant bladder cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01517-9.

A Perspective on Medicinal Chemistry Approaches for Targeting Pyruvate Kinase M2

The allosteric regulation of pyruvate kinase M2 (PKM2) affects the switching of the PKM2 protein between the high-activity and low-activity states that allow ATP and lactate production, respectively. PKM2, in its low catalytic state (dimeric form), is chiefly active in metabolically energetic cells, including cancer cells. More recently, PKM2 has emerged as an attractive target due to its role in metabolic dysfunction and other interrelated conditions. PKM2 (dimer) activity can be inhibited by modulating PKM2 dimer-tetramer dynamics using either PKM2 inhibitors that bind at the ATP binding active site of PKM2 (dimer) or PKM2 activators that bind at the allosteric site of PKM2, thus activating PKM2 from the dimer formation to the tetrameric formation. The present perspective focuses on medicinal chemistry approaches to design and discover PKM2 inhibitors and activators and further provides a scope for the future design of compounds targeting PKM2 with better efficacy and selectivity.

Shikonin suppresses the epithelial-to-mesenchymal transition by downregulating NHE1 in bladder cancer cells

Shikonin (SK) is the major bioactive component extracted from the roots of Lithospermum erythrorhizon with anticancer activity. SK could inhibit the epithelial-to-mesenchymal transition (EMT) of cancer cells. However, the underlying mechanism is elusive. In the present study, the inhibitory activities of SK on proliferation, invasion and migration were examined in bladder cancer (BC) cells. SK potently decreased the viabilities of BC cells but showed less cytotoxicity to normal bladder epithelial cells. Moreover, SK reversed the EMT, suppressed the migration and invasion of BC cells. Intriguingly, NHE1, the major proton efflux pump, was dramatically down-regulated by SK. The EMT-inhibitory effect of SK was mediated by NHE1 down-regulation, as NHE1-overexpress alleviated while Cariporide (NHE1 inhibitor) enhanced this effect. Further, enforced alkalinization of intracellular pH (pHi) reversed the EMT-inhibitory effect of SK, indicating a key role of acidic pHi in this process. Finally, elevated NHE1 expression was observed in human bladder cancer tissues. Collectively, this research reveals a supportive effect of NHE1 and alkaline pHi on EMT. SK can suppress EMT through inhibiting NHE1 and hence inducing an acidic pHi.

TBX15/miR-152/KIF2C pathway regulates breast cancer doxorubicin resistance via promoting PKM2 ubiquitination

Background

Chemoresistance is a critical risk problem for breast cancer treatment. However, mechanisms by which chemoresistance arises remains to be elucidated. The expression of T-box transcription factor 15 (TBX-15) was found downregulated in some cancer tissues. However, role and mechanism of TBX15 in breast cancer chemoresistance is unknown. Here we aimed to identify the effects and mechanisms of TBX15 in doxorubicin resistance in breast cancer.

Methods

As measures of Drug sensitivity analysis, MTT and IC50 assays were used in DOX-resistant breast cancer cells. ECAR and OCR assays were used to analyze the glycolysis level, while Immunoblotting and Immunofluorescence assays were used to analyze the autophagy levels in vitro. By using online prediction software, luciferase reporter assays, co-Immunoprecipitation, Western blotting analysis and experimental animals models, we further elucidated the mechanisms.

Results

We found TBX15 expression levels were decreased in Doxorubicin (DOX)-resistant breast cancer cells. Overexpression of TBX15 reversed the DOX resistance by inducing microRNA-152 (miR-152) expression. We found that KIF2C levels were highly expressed in DOX-resistant breast cancer tissues and cells, and KIF2C was a potential target of miR-152. TBX15 and miR-152 overexpression suppressed autophagy and glycolysis in breast cancer cells, while KIF2C overexpression reversed the process. Overexpression of KIF2C increased DOX resistance in cancer cells. Furthermore, KIF2C directly binds with PKM2 for inducing the DOX resistance. KIF2C can prevent the ubiquitination of PKM2 and increase its protein stability. In addition, we further identified that Domain-2 of KIF2C played a major role in the binding with PKM2 and preventing PKM2 ubiquitination, which enhanced DOX resistance by promoting autophagy and glycolysis.

Conclusions

Our data identify a new mechanism by which TBX15 abolishes DOX chemoresistance in breast cancer, and suggest that TBX15/miR-152/KIF2C axis is a novel signaling pathway for mediating DOX resistance in breast cancer through regulating PKM2 ubiquitination and decreasing PKM2 stability. This finding suggests new therapeutic target and/or novel strategy development for cancer treatment to overcome drug resistance in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02235-w.

Current Development and Application of Anaerobic Glycolytic Enzymes in Urothelial Cancer

Urothelial cancer is a malignant tumor with metastatic ability and high mortality. Malignant tumors of the urinary system include upper tract urothelial cancer and bladder cancer. In addition to typical genetic alterations and epigenetic modifications, metabolism-related events also occur in urothelial cancer. This metabolic reprogramming includes aberrant expression levels of genes, metabolites, and associated networks and pathways. In this review, we summarize the dysfunctions of glycolytic enzymes in urothelial cancer and discuss the relevant phenotype and signal transduction. Moreover, we describe potential prognostic factors and risks to the survival of clinical cancer patients. More importantly, based on several available databases, we explore relationships between glycolytic enzymes and genetic changes or drug responses in urothelial cancer cells. Current advances in glycolysis-based inhibitors and their combinations are also discussed. Combining all of the evidence, we indicate their potential value for further research in basic science and clinical applications.

The Mechanism of Warburg Effect-Induced Chemoresistance in Cancer

Although chemotherapy can improve the overall survival and prognosis of cancer patients, chemoresistance remains an obstacle due to the diversity, heterogeneity, and adaptability to environmental alters in clinic. To determine more possibilities for cancer therapy, recent studies have begun to explore changes in the metabolism, especially glycolysis. The Warburg effect is a hallmark of cancer that refers to the preference of cancer cells to metabolize glucose anaerobically rather than aerobically, even under normoxia, which contributes to chemoresistance. However, the association between glycolysis and chemoresistance and molecular mechanisms of glycolysis-induced chemoresistance remains unclear. This review describes the mechanism of glycolysis-induced chemoresistance from the aspects of glycolysis process, signaling pathways, tumor microenvironment, and their interactions. The understanding of how glycolysis induces chemoresistance may provide new molecular targets and concepts for cancer therapy.

Shikonin induces programmed death of fibroblast synovial cells in rheumatoid arthritis by inhibiting energy pathways

Shikonin is the main component of the traditional Chinese medicine comfrey, which can inhibit the activity of PKM2 by regulating glycolysis and ATP production. Rheumatoid arthritis synovial cells (RA-FLSs) have been reported to increase glycolytic activity and have other similar hallmarks of metabolic activity. In this study, we investigated the effects of shikonin on glycolysis, mitochondrial function, and cell death in RA-FLSs. The results showed that shikonin induced apoptosis and autophagy in RA-FLSs by activating the production of reactive oxygen species (ROS) and inhibiting intracellular ATP levels, glycolysis-related proteins, and the PI3K-AKT-mTOR signaling pathway. Shikonin can significantly reduce the expression of apoptosis-related proteins, paw swelling in rat arthritic tissues, and the levels of inflammatory factors in peripheral blood, such as TNF-α, IL-6, IL-8, IL-10, IL-17A, and IL-1β while showing less toxicity to the liver and kidney.

Targeting pyruvate kinase muscle isoform 2 (PKM2) in cancer: What do we know so far?

Cancer is a leading cause of death globally. Cancer cell transformation is the result of intricate crosstalk between intracellular components and proteins. A characteristic feature of cancer cells is the ability to reprogram their metabolic pathways to ensure their infinite proliferative potential. Pyruvate kinase muscle isoform 2 (PKM2) is a glycolytic enzyme that plays crucial roles in cancer, apart from carrying out its metabolic roles. PKM2 is involved in all the major events associated with cancer growth. Modulation of PKM2 activity (dimer inhibition or tetramer activation) has been successful in controlling cancer. However, recent studies provide contrary evidences regarding the oncogenic functions of PKM2. Moreover, several studies have highlighted the cancerous roles of PKM1 isoform in certain contexts. The present review aims at providing the current updates regarding PKM2 targeting in cancer. Further, the review discusses the contradictory results that suggest that both the isoforms of PKM can lead to cancer growth. In conclusion, the review emphasizes revisiting the approaches to target cancer metabolism through PKM to find novel and effective targets for anticancer therapy.

Dual Covalent Inhibition of PKM and IMPDH Targets Metabolism in Cutaneous Metastatic Melanoma

Overcoming acquired drug resistance is a primary challenge in cancer treatment. Notably, more than 50% of patients with BRAFV600E cutaneous metastatic melanoma (CMM) eventually develop resistance to BRAF inhibitors. Resistant cells undergo metabolic reprogramming that profoundly influences therapeutic response and promotes tumor progression. Uncovering metabolic vulnerabilities could help suppress CMM tumor growth and overcome drug resistance. Here we identified a drug, HA344, that concomitantly targets two distinct metabolic hubs in cancer cells. HA344 inhibited the final and rate-limiting step of glycolysis through its covalent binding to the pyruvate kinase M2 (PKM2) enzyme, and it concurrently blocked the activity of inosine monophosphate dehydrogenase, the rate-limiting enzyme of de novo guanylate synthesis. As a consequence, HA344 efficiently targeted vemurafenib-sensitive and vemurafenib-resistant CMM cells and impaired CMM xenograft tumor growth in mice. In addition, HA344 acted synergistically with BRAF inhibitors on CMM cell lines in vitro. Thus, the mechanism of action of HA344 provides potential therapeutic avenues for patients with CMM and a broad range of different cancers. SIGNIFICANCE: Glycolytic and purine synthesis pathways are often deregulated in therapy-resistant tumors and can be targeted by the covalent inhibitor described in this study, suggesting its broad application for overcoming resistance in cancer.

Cisplatin Resistance and Redox-Metabolic Vulnerability: A Second Alteration

The development of drug resistance in tumors is a major obstacle to effective cancer chemotherapy and represents one of the most significant complications to improving long-term patient outcomes. Despite early positive responsiveness to platinum-based chemotherapy, the majority of lung cancer patients develop resistance. The development of a new combination therapy targeting cisplatin-resistant (CR) tumors may mark a major improvement as salvage therapy in these patients. The recent resurgence in research into cellular metabolism has again confirmed that cancer cells utilize aerobic glycolysis ("the Warburg effect") to produce energy. Hence, this observation still remains a characteristic hallmark of altered metabolism in certain cancer cells. However, recent evidence promotes another concept wherein some tumors that acquire resistance to cisplatin undergo further metabolic alterations that increase tumor reliance on oxidative metabolism (OXMET) instead of glycolysis. Our review focuses on molecular changes that occur in tumors due to the relationship between metabolic demands and the importance of NAD+ in redox (ROS) metabolism and the crosstalk between PARP-1 (Poly (ADP ribose) polymerase-1) and SIRTs (sirtuins) in CR tumors. Finally, we discuss a role for the tumor metabolites of the kynurenine pathway (tryptophan catabolism) as effectors of immune cells in the tumor microenvironment during acquisition of resistance in CR cells. Understanding these concepts will form the basis for future targeting of CR cells by exploiting redox-metabolic changes and their consequences on immune cells in the tumor microenvironment as a new approach to improve overall therapeutic outcomes and survival in patients who fail cisplatin.

Extracellular Vesicle Transmission of Chemoresistance to Ovarian Cancer Cells Is Associated with Hypoxia-Induced Expression of Glycolytic Pathway Proteins, and Prediction of Epithelial Ovarian Cancer Disease Recurrence

Simple Summary

Ovarian cancer is one of the most lethal cancers affecting women worldwide. Its high mortality rate is often attributed to the non-specific nature of early symptoms of the disease. Developing a better understanding of the disease progression and identifying clinically useful biomarkers that aid in clinical management are requisite to reducing the mortality rate of ovarian cancer. Reduced oxygen tension (i.e., hypoxia) is not only a characteristic of solid tumors but may also enhance the metastatic capacity of tumors by inducing the release of tumor growth promoting factors. Recently, it has been proposed that small tumor-derived extracellular vesicles (sEVs) facilitate cancer progression. In this study, we established that sEVs produced under low oxygen tension induce a metabolic switch in ovarian cancer cells associated with changes in glycolytic pathway proteins that promote resistance to carboplatin. Significantly, we identified a suite of sEV-associated glycolysis pathway proteins that are present in patients with ovarian cancer that can predict disease recurrence with over 90% accuracy.

Abstract

Hypoxia is a key regulator of cancer progression and chemoresistance. Ambiguity remains about how cancer cells adapt to hypoxic microenvironments and transfer oncogenic factors to surrounding cells. In this study, we determined the effects of hypoxia on the bioactivity of sEVs in a panel of ovarian cancer (OvCar) cell lines. The data obtained demonstrate a varying degree of platinum resistance induced in OvCar cells when exposed to low oxygen tension (1% oxygen). Using quantitative mass spectrometry (Sequential Window Acquisition of All Theoretical Fragment Ion Mass Spectra, SWATH) and targeted multiple reaction monitoring (MRM), we identified a suite of proteins associated with glycolysis that change under hypoxic conditions in cells and sEVs. Interestingly, we identified a differential response to hypoxia in the OvCar cell lines and their secreted sEVs, highlighting the cells’ heterogeneity. Proteins are involved in metabolic reprogramming such as glycolysis, including putative hexokinase (HK), UDP-glucuronosyltransferase 1–6 (UD16), and 6-phosphogluconolactonase (6 PGL), and their presence correlates with the induction of platinum resistance. Furthermore, when normoxic cells were exposed to sEVs from hypoxic cells, platinum-resistance increased significantly (p < 0.05). Altered chemoresistance was associated with changes in glycolysis and fatty acid synthesis. Finally, sEVs isolated from a clinical cohort (n = 31) were also found to be enriched in glycolysis-pathway proteins, especially in patients with recurrent disease. These data support the hypothesis that hypoxia induces changes in sEVs composition and bioactivity that confers carboplatin resistance on target cells. Furthermore, we propose that the expression of sEV-associated glycolysis-pathway proteins is predictive of ovarian cancer recurrence and is of clinical utility in disease management.

The role of the HIF-1α/ALYREF/PKM2 axis in glycolysis and tumorigenesis of bladder cancer

BACKGROUND

As a rate-limiting enzyme of glycolysis, pyruvate kinase muscle isozyme M2 (PKM2) participates in tumor metabolism and growth. The regulatory network of PKM2 in cancer is complex and has not been fully studied in bladder cancer. The 5-methylcytidine (m5C) modification in PKM2 mRNA might participate in the pathogenesis of bladder cancer and need to be further clarified. This study aimed to investigate the biological function and regulatory mechanism of PKM2 in bladder cancer.

METHODS

The expression of PKM2 and Aly/REF export factor (ALYREF) was measured by Western blotting, qRT-PCR, and immunohistochemistry. The bioprocesses of bladder cancer cells were demonstrated by a series of experiments in vitro and in vivo. RNA immunoprecipitation, RNA-sequencing, and dual-luciferase reporter assays were conducted to explore the potential regulatory mechanisms of PKM2 in bladder cancer.

RESULTS

In bladder cancer, we first demonstrated that ALYREF stabilized PKM2 mRNA and bound to its m5C sites in 3'-untranslated regions. Overexpression of ALYREF promoted bladder cancer cell proliferation by PKM2-mediated glycolysis. Furthermore, high expression of PKM2 and ALYREF predicted poor survival in bladder cancer patients. Finally, we found that hypoxia-inducible factor-1alpha (HIF-1α) indirectly up-regulated the expression of PKM2 by activating ALYREF in addition to activating its transcription directly.

CONCLUSIONS

The m5C modification in PKM2 mRNA in the HIF-1α/ALYREF/PKM2 axis may promote the glucose metabolism of bladder cancer, providing a new promising therapeutic target for bladder cancer.

Overcoming chemoresistance by targeting reprogrammed metabolism: the Achilles' heel of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death due to its late diagnosis that removes the opportunity for surgery and metabolic plasticity that leads to resistance to chemotherapy. Metabolic reprogramming related to glucose, lipid, and amino acid metabolism in PDAC not only enables the cancer to thrive and survive under hypovascular, nutrient-poor and hypoxic microenvironments, but also confers chemoresistance, which contributes to the poor prognosis of PDAC. In this review, we systematically elucidate the mechanism of chemotherapy resistance and the relationship of metabolic programming features with resistance to anticancer drugs in PDAC. Targeting the critical enzymes and/or transporters involved in glucose, lipid, and amino acid metabolism may be a promising approach to overcome chemoresistance in PDAC. Consequently, regulating metabolism could be used as a strategy against PDAC and could improve the prognosis of PDAC.

The Role of Tumour Metabolism in Cisplatin Resistance

Cisplatin is a chemotherapy drug commonly used in cancer treatment. Tumour cells are more sensitive to cisplatin than normal cells. Cisplatin exerts an antitumour effect by interfering with DNA replication and transcription processes. However, the drug-resistance properties of tumour cells often cause loss of cisplatin efficacy and failure of chemotherapy, leading to tumour progression. Owing to the large amounts of energy and compounds required by tumour cells, metabolic reprogramming plays an important part in the occurrence and development of tumours. The interplay between DNA damage repair and metabolism also has an effect on cisplatin resistance; the molecular changes to glucose metabolism, amino acid metabolism, lipid metabolism, and other metabolic pathways affect the cisplatin resistance of tumour cells. Here, we review the mechanism of action of cisplatin, the mechanism of resistance to cisplatin, the role of metabolic remodelling in tumorigenesis and development, and the effects of common metabolic pathways on cisplatin resistance.

A short review on cross-link between pyruvate kinase (PKM2) and Glioblastoma Multiforme

Pyruvate kinase (PK) catalyzes the last irreversible reaction of glycolysis pathway, generating pyruvate and ATP, from Phosphoenol Pyruvate (PEP) and ADP precursors. In mammals, four different tissue-specific isoforms (M1, M2, L and R) of PK exist, which are translated from two genes (PKL and PKR). PKM2 is the highly expressed isoform of PK in cancers, which regulates the aerobic glycolysis via reprogramming cancer cell's metabolic pathways to provide an anabolic advantage to the tumor cells. In addition to the established role of PKM2 in aerobic glycolysis of multiple cancer types, various recent findings have highlighted the non-metabolic functions of PKM2 in brain tumor development. Nuclear PKM2 acts as a co-activator and directly regulates gene transcription. PKM2 dependent transactivation of various oncogenic genes is instrumental in the progression and aggressiveness of Glioblastoma Multiforme (GBM). Also, PKM2 acts as a protein kinase in histone modification which regulates gene expression and tumorigenesis. Ongoing research has explored novel regulatory mechanisms of PKM2 and its association in GBM progression. This review enlists and summarizes the metabolic and non-metabolic roles of PKM2 at the cellular level, and its regulatory function highlights the importance of the nuclear functions of PKM2 in GBM progression, and an emerging role of PKM2 as novel cancer therapeutics.

Epigenomic and Metabolomic Integration Reveals Dynamic Metabolic Regulation in Bladder Cancer

Bladder cancer (BC) represents a clinical, social, and economic challenge due to tumor-intrinsic characteristics, limitations of diagnostic techniques and a lack of personalized treatments. In the last decade, the use of liquid biopsy has grown as a non-invasive approach to characterize tumors. Moreover, the emergence of omics has increased our knowledge of cancer biology and identified critical BC biomarkers. The rewiring between epigenetics and metabolism has been closely linked to tumor phenotype. Chromatin remodelers interact with each other to control gene silencing in BC, but also with stress-inducible factors or oncogenic signaling cascades to regulate metabolic reprogramming towards glycolysis, the pentose phosphate pathway, and lipogenesis. Concurrently, one-carbon metabolism supplies methyl groups to histone and DNA methyltransferases, leading to the hypermethylation and silencing of suppressor genes in BC. Conversely, α-KG and acetyl-CoA enhance the activity of histone demethylases and acetyl transferases, increasing gene expression, while succinate and fumarate have an inhibitory role. This review is the first to analyze the interplay between epigenome, metabolome and cell signaling pathways in BC, and shows how their regulation contributes to tumor development and progression. Moreover, it summarizes non-invasive biomarkers that could be applied in clinical practice to improve diagnosis, monitoring, prognosis and the therapeutic options in BC.

Exosomes function as nanoparticles to transfer miR-199a-3p to reverse chemoresistance to cisplatin in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a frequently seen malignant tumor globally. The occurrence of cisplatin (DDP) resistance is one of the main reasons for the high mortality of HCC patients. Therefore, it is of great theoretical significance and application value to explore the mechanism of chemotherapy resistance. Drug resistance can be modulated by exosomes containing mRNAs, micro RNAs (miRNAs) and other non-coding RNA (ncRNAs). Exosomal miR-199a-3p (Exo-miR-199a-3p) was subjected to extraction and verification. Whether exo-miR-199a-3p could make HCC cells sensitive to DDP in vitro was verified via flow cytometry, Cell Counting Kit-8 (CCK-8) assay, immunofluorescence assay and Transwell assay. Intravenous injection of exo-miR-199a-3p and intraperitoneal injection of DDP were carried out in vivo. Moreover, the possible targets of miR-199a-3p were screened through bioinformatics analysis, which were ascertained by Western blotting (WB). Then, miR-199a-3p levels in human normal liver epithelial cell line HL-7702 and HCC cell lines HuH7 and HuH7/DDP were elevated in a concentration-dependent manner. Exo-miR-199a-3p has abilities to adjust underlying targets and conjugate cells, to repress cells to invade, stimulate their apoptosis and abate their ability. Additionally, the caudal injection of exo-miR-199a-3p reversed the chemoresistance of tumors and slowed down their growth in the body owing to the up-regulation of miR-199a-3p and down-regulation of underlying target proteins in tumors. Finally, exo-miR-199a-3p was found to overturn the HCC’s resistance to DDP, and it may function in DDP-refractory HCC therapy as an underlying option in the future.

Cisplatin resistance reversal in lung cancer by tumor acidity-activable vesicular nanoreactors via tumor oxidative stress amplification

Drug resistance of cisplatin significantly limits its therapeutic efficacy in clinical applications against different cancers. Herein, we develop a novel strategy to overcome cisplatin drug resistance through sensitizing cisplatin-resistant human lung cancer cells (A549R) under amplified oxidative stress using a vesicular nanoreactor for simultaneous cisplatin delivery and H₂O₂ generation. We engineer the nanoreactor by the self-assembly of the amphiphilic diblock copolymers to co-deliver glucose oxidase (GOD) and cisplatin (Cis) (Cis/GOD@Bz-V). Cis/GOD@Bz-V was rationally designed to stay impermeable during blood circulation while mild acidity (pH 6.5-6.8) can activate its molecular-weight selective membrane permeability and release cisplatin locally. Diffusion of small molecules such as oxygen and glucose across the membranes can induce the in situ generation of superfluous H₂O₂ to promote cellular oxidative stress and sensitize A549R cells via activation of pro-apoptotic pathways. Cis/GOD@Bz-V nanoreactors could effectively kill A549R at pH 6.8 in the presence of glucose by the combination of H₂O₂ generation and cisplatin release. Growth of A549R xenograft tumors can be inhibited efficiently without the obvious toxic side effects via the systemic administration of Cis/GOD@Bz-V. Accordingly, the tumor acidity-activable cisplatin-loaded nanoreactors show great potential to enhance the therapeutic efficacy against cisplatin-resistant cancers.

Natural products as a means of overcoming cisplatin chemoresistance in bladder cancer

Cisplatin remains an integral part of the treatment for muscle invasive bladder cancer. A large number of patients do not respond to cisplatin-based chemotherapy and efficacious salvage regimens are limited. Immunotherapy has offered a second line of treatment; however, only approximately 20% of patients respond, and molecular subtyping of tumors indicates there may be significant overlap in those patients that respond to cisplatin and those patients that respond to immunotherapy. As such, restoring sensitivity to cisplatin remains a major hurdle to improving patient care. One potential source of compounds for enhancing cisplatin is naturally derived bioactive products such as phytochemicals, flavonoids and others. These compounds can activate a diverse array of different pathways, many of which can directly promote or inhibit cisplatin sensitivity. The purpose of this review is to understand current drug development in the area of natural products and to assess how these compounds may enhance cisplatin treatment in bladder cancer patients.

Advances in Our Understanding of the Molecular Mechanisms of Action of Cisplatin in Cancer Therapy

Cisplatin and other platinum-based chemotherapeutic drugs have been used extensively for the treatment of human cancers such as bladder, blood, breast, cervical, esophageal, head and neck, lung, ovarian, testicular cancers, and sarcoma. Cisplatin is commonly administered intravenously as a first-line chemotherapy for patients suffering from various malignancies. Upon absorption into the cancer cell, cisplatin interacts with cellular macromolecules and exerts its cytotoxic effects through a series of biochemical mechanisms by binding to Deoxyribonucleic acid (DNA) and forming intra-strand DNA adducts leading to the inhibition of DNA synthesis and cell growth. Its primary molecular mechanism of action has been associated with the induction of both intrinsic and extrinsic pathways of apoptosis resulting from the production of reactive oxygen species through lipid peroxidation, activation of various signal transduction pathways, induction of p53 signaling and cell cycle arrest, upregulation of pro-apoptotic genes/proteins, and down-regulation of proto-oncogenes and anti-apoptotic genes/proteins. Despite great clinical outcomes, many studies have reported substantial side effects associated with cisplatin monotherapy, while others have shown substantial drug resistance in some cancer patients. Hence, new formulations and several combinational therapies with other drugs have been tested for the purpose of improving the clinical utility of cisplatin. Therefore, this review provides a comprehensive understanding of its molecular mechanisms of action in cancer therapy and discusses the therapeutic approaches to overcome cisplatin resistance and side effects.

Altered glycolysis results in drug-resistant in clinical tumor therapy

Cancer cells undergo metabolic reprogramming, including increased glucose metabolism, fatty acid synthesis and glutamine metabolic rates. These enhancements to three major metabolic pathways are closely associated with glycolysis, which is considered the central component of cancer cell metabolism. Increasing evidence suggests that dysfunctional glycolysis is commonly associated with drug resistance in cancer treatment, and aberrant glycolysis plays a significant role in drug-resistant cancer cells. Studies on the development of drugs targeting these abnormalities have led to improvements in the efficacy of tumor treatment. The present review discusses the changes in glycolysis targets that cause drug resistance in cancer cells, including hexokinase, pyruvate kinase, pyruvate dehydrogenase complex, glucose transporters, and lactate, as well the underlying molecular mechanisms and corresponding novel therapeutic strategies. In addition, the association between increased oxidative phosphorylation and drug resistance is introduced, which is caused by metabolic plasticity. Given that aberrant glycolysis has been identified as a common metabolic feature of drug-resistant tumor cells, targeting glycolysis may be a novel strategy to develop new drugs to benefit patients with drug-resistance.

The Role of PKM2 in Metabolic Reprogramming: Insights into the Regulatory Roles of Non-Coding RNAs

Pyruvate kinase is a key regulator in glycolysis through the conversion of phosphoenolpyruvate (PEP) into pyruvate. Pyruvate kinase exists in various isoforms that can exhibit diverse biological functions and outcomes. The pyruvate kinase isoenzyme type M2 (PKM2) controls cell progression and survival through the regulation of key signaling pathways. In cancer cells, the dimer form of PKM2 predominates and plays an integral role in cancer metabolism. This predominance of the inactive dimeric form promotes the accumulation of phosphometabolites, allowing cancer cells to engage in high levels of synthetic processing to enhance their proliferative capacity. PKM2 has been recognized for its role in regulating gene expression and transcription factors critical for health and disease. This role enables PKM2 to exert profound regulatory effects that promote cancer cell metabolism, proliferation, and migration. In addition to its role in cancer, PKM2 regulates aspects essential to cellular homeostasis in non-cancer tissues and, in some cases, promotes tissue-specific pathways in health and diseases. In pursuit of understanding the diverse tissue-specific roles of PKM2, investigations targeting tissues such as the kidney, liver, adipose, and pancreas have been conducted. Findings from these studies enhance our understanding of PKM2 functions in various diseases beyond cancer. Therefore, there is substantial interest in PKM2 modulation as a potential therapeutic target for the treatment of multiple conditions. Indeed, a vast plethora of research has focused on identifying therapeutic strategies for targeting PKM2. Recently, targeting PKM2 through its regulatory microRNAs, long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) has gathered increasing interest. Thus, the goal of this review is to highlight recent advancements in PKM2 research, with a focus on PKM2 regulatory microRNAs and lncRNAs and their subsequent physiological significance.

Role of Bladder Cancer Metabolic Reprogramming in the Effectiveness of Immunotherapy

Metabolic reprogramming (MR) is an upregulation of biosynthetic and bioenergetic pathways to satisfy increased energy and metabolic building block demands of tumors. This includes glycolytic activity, which deprives the tumor microenvironment (TME) of nutrients while increasing extracellular lactic acid. This inhibits cytotoxic immune activity either via direct metabolic competition between cancer cells and cytotoxic host cells or by the production of immune-suppressive metabolites such as lactate or kynurenine. Since immunotherapy is a major treatment option in patients with metastatic urothelial carcinoma (UC), MR may have profound implications for the success of such therapy. Here, we review how MR impacts host immune response to UC and the impact on immunotherapy response (including checkpoint inhibitors, adaptive T cell therapy, T cell activation, antigen presentation, and changes in the tumor microenvironment). Articles were identified by literature searches on the keywords or references to "UC" and "MR". We found several promising therapeutic approaches emerging from preclinical models that can circumvent suppressive MR effects on the immune system. A select summary of active clinical trials is provided with examples of possible options to enhance the effectiveness of immunotherapy. In conclusion, the literature suggests manipulating the MR is feasible and may improve immunotherapy effectiveness in UC.

Glycolysis-induced drug resistance in tumors-A response to danger signals?

Tumor cells often switch from mitochondrial oxidative metabolism to glycolytic metabolism even under aerobic conditions. Tumor cell glycolysis is accompanied by several nonenzymatic activities among which induction of drug resistance has important therapeutic implications. In this article, we review the main aspects of glycolysis-induced drug resistance. We discuss the classes of antitumor drugs that are affected and the components of the glycolytic pathway (transporters, enzymes, metabolites) that are involved in the induction of drug resistance. Glycolysis-associated drug resistance occurs in response to stimuli, either cell-autonomous (e.g., oncoproteins) or deriving from the tumor microenvironment (e.g., hypoxia or pseudohypoxia, mechanical cues, etc.). Several mechanisms mediate the induction of drug resistance in response to glycolytic metabolism: inhibition of apoptosis, induction of epithelial-mesenchymal transition, induction of autophagy, inhibition of drug influx and increase of drug efflux. We suggest that drug resistance in response to glycolysis comes into play in presence of qualitative (e.g., expression of embryonic enzyme isoforms, post-translational enzyme modifications) or quantitative (e.g., overexpression of enzymes or overproduction of metabolites) alterations of glycolytic metabolism. We also discern similarities between changes occurring in tumor cells in response to stimuli inducing glycolysis-associated drug resistance and those occurring in cells of the innate immune system in response to danger signals and that have been referred to as danger-associated metabolic modifications. Eventually, we briefly address that also mitochondrial oxidative metabolism may induce drug resistance and discuss the therapeutic implications deriving from the fact that the main energy-generating metabolic pathways may be both at the origin of antitumor drug resistance.

Targeting Metabolism in Cancer Cells and the Tumour Microenvironment for Cancer Therapy

Targeting altered tumour metabolism is an emerging therapeutic strategy for cancer treatment. The metabolic reprogramming that accompanies the development of malignancy creates targetable differences between cancer cells and normal cells, which may be exploited for therapy. There is also emerging evidence regarding the role of stromal components, creating an intricate metabolic network consisting of cancer cells, cancer-associated fibroblasts, endothelial cells, immune cells, and cancer stem cells. This metabolic rewiring and crosstalk with the tumour microenvironment play a key role in cell proliferation, metastasis, and the development of treatment resistance. In this review, we will discuss therapeutic opportunities, which arise from dysregulated metabolism and metabolic crosstalk, highlighting strategies that may aid in the precision targeting of altered tumour metabolism with a focus on combinatorial therapeutic strategies.

[Shikonin induces cell death by inhibiting glycolysis in human testicular cancer I-10 and seminoma TCAM-2 cells]

OBJECTIVE

To investigate the pattern of shikonin-induced cell death in testicular cancer cell I-10 and seminoma TCAM-2 cells and explore the possible mechanism in light of mitochondrial function and glycolysis.

METHODS

I-10 cells treated with 0, 1.2, 1.4 and 1.6 μmol/L shikonin and TCAM-2 cells treated with 0, 0.5, 1 and 1.5 μmol/L shikonin were examined for mitochondrial membrane potential and production of reactive oxygen species (ROS) using JC-1 kit and ROS kit, respectively. The levels of intracellular lactic acid in the cells were detected using a lactic acid kit. The inhibitory effect of shikonin on the proliferation of the cells was assessed with MTT assay. The death patterns of the cells were observed by transmission electron microscopy, and annexin V-FITC/PI double staining was used to detect cell apoptosis. Western blotting was used to detect the relative expression levels of the apoptotic proteins Bax, Bcl-2, and cleaved caspase-3, the autophagy- related protein LC3B and glycolysis- related proteins PKM2, GLUT1 and HK2.

RESULTS

MTT assay showed that shikonin significantly inhibited the proliferation of I-10 and TCAM-2 cells in a time- and dose-dependent manner (P < 0.05). The IC₅₀ values of shikonin in I-10 cells at 24, 48, and 72 h were 1.8, 1.36 and 1.16 μmol/L, as compared with 2.37, 0.8 and 0.41 μmol/L in TCAM-2 cells, respectively. Shikonin treatment significantly reduced mitochondrial membrane potential, increased ROS levels and lower the level of lactic acid in both I-10 and TCAM-2 cells (P < 0.05). Transmission electron microscopy and annexin V-FITC/PI double staining demonstrated that shikonin induced apoptosis and excessive autophagy in I-10 and TCAM-2 cells (P < 0.05). In both I-10 and TCAM cells, shikonin treatment significantly down- regulated the expressions of Bax, Bcl-2, cleaved caspase-3, PKM2, GLUT1 and HK2, and up-regulated the expression of autophagy-related protein LC3B (P < 0.05).

CONCLUSIONS

Shikonin can inhibit the proliferation, induce apoptosis and increase autophagy in both I-10 and TCAM-2 cells probably by affecting energy metabolism of the cells.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

PKM2 Expression as Biomarker for Resistance to Oxaliplatin-Based Chemotherapy in Colorectal Cancer

The purpose of the current study is to investigate the prognostic significance of M2 isoform of pyruvate kinase (PKM2) mRNA expression loss in patients with operable colon cancer (CC). Two hundred sixty-two specimens from patients with stage-III or high-risk stage-II CC (group-A) treated with adjuvant fluoropyrimidine and oxaliplatin chemotherapy (FOLFOX), 118 specimens from metastatic CC patients (group-B) treated with FOLFOX, and 104 metastatic CC patients (group-C) treated with irinotecan-based chemotherapy were analyzed for PKM2, TS, ERCC1, MYC, and NEDD9 mRNA expression, as well as KRAS exon2 and BRAF^V600E mutations. High PKM2 mRNA expression was correlated with left-sided located primaries (p = 0.001, group-A; p = 0.003, group-B; p = 0.001, group-C), high-grade tumors (p = 0.001, group-A; p = 0.017, group-B; p = 0.021, group-C), microsatellite-stable tumors (p < 0.001, group-A), pericolic lymph nodes involvement (p = 0.018, group-A), and cMYC mRNA expression (p = 0.002, group-A; p = 0.008, group-B; p = 0.006, group-C). High PKM2 mRNA expression was correlated with significantly lower disease free survival (DFS) (p = 0.002) and overall survival (OS) (p = 0.001) in the group-A. Similarly, PKM2 mRNA expression was associated with significantly decreased progression free survival (PFS) (p = 0.001) and OS (p = 0.001) in group-B. On the contrary, no significant association for the PKM2 mRNA expression has been observed with either PFS (p = 0.612) or OS (p = 0.517) in group-C. To conclude, the current study provides evidence for the prediction of PKM2 mRNA expression oxaliplatin-based treatment resistance.

Reactive Oxygen Species, Metabolic Plasticity, and Drug Resistance in Cancer

The metabolic abnormality observed in tumors is characterized by the dependence of cancer cells on glycolysis for their energy requirements. Cancer cells also exhibit a high level of reactive oxygen species (ROS), largely due to the alteration of cellular bioenergetics. A highly coordinated interplay between tumor energetics and ROS generates a powerful phenotype that provides the tumor cells with proliferative, antiapoptotic, and overall aggressive characteristics. In this review article, we summarize the literature on how ROS impacts energy metabolism by regulating key metabolic enzymes and how metabolic pathways e.g., glycolysis, PPP, and the TCA cycle reciprocally affect the generation and maintenance of ROS homeostasis. Lastly, we discuss how metabolic adaptation in cancer influences the tumor’s response to chemotherapeutic drugs. Though attempts of targeting tumor energetics have shown promising preclinical outcomes, the clinical benefits are yet to be fully achieved. A better understanding of the interaction between metabolic abnormalities and involvement of ROS under the chemo-induced stress will help develop new strategies and personalized approaches to improve the therapeutic efficiency in cancer patients.

Targets for Therapy of Bladder Cancer

In 2018 bladder cancer (urothelial carcinoma) was ranked twelfth concerning worldwide diagnosis of malignancies. At the time point of diagnosis of bladder cancer, approximately 75% of patients present with a nonmuscle-invasive disease (NMIBC), while the remaining 25% show invasion of tumor cells in the muscle layer of the bladder wall (MIBC). Among NMIBC tumors, flat, high-grade carcinoma in situ (CIS) is a therapeutic challenge. CIS shows a tendency to invade the muscle tissue of the bladder wall and thus become a MIBC. Standard therapy of NMIBC (including CIS) is done via intravesical instillation of BCG (bacillus Calmette Guerin) inducing a local immune reaction that finally promotes elimination of bladder cancer cells. However, BCG treatment of NMIBC proves to be ineffective in approximately 40% of patients. Therefore, new therapeutic approaches for the treatment of bladder cancer are urgently needed. Among promising new treatment options that are currently being investigated are the use of immune checkpoint inhibitors, and targeted approaches attacking (among others) long noncoding RNAs, micro RNAs, cancer stem cells, PARP1, and receptor signaling pathways. Moreover, the use of antibody-drug-conjugates (ADCs) is investigated also in bladder cancer therapy. Another approach that has been successfully established in preclinical studies uses the cytotoxic power of the alpha-emitter Bi-213 coupled to an antibody targeting EGFR. Overexpression of EGFR has been demonstrated in the majority of patients suffering from CIS. Feasibility, safety, toxicity and therapeutic efficacy of intravesical instillation of Bi-213-anti-EGFR have been evaluated in a pilot study. Since the results of the pilot study proved to be promising, a further optimization of alpha-emitter immunotherapy in bladder cancer seems mandatory.

Metabolic Symbiosis in Chemoresistance: Refocusing the Role of Aerobic Glycolysis

Cellular metabolic reprogramming is now recognized as a hallmark of tumors. Altered tumor metabolism determines the malignant biological behaviors and phenotypes of cancer. More recently, studies have begun to reveal that cancer cells generally exhibit increased glycolysis or oxidative phosphorylation (OXPHOS) for Adenosine Triphosphate(ATP)generation, which is frequently associated with drug resistance. The metabolism of drug-resistant cells is regulated by the PI3K/AKT/mTOR pathway which ultimately confer cancer cells drug resistance phenotype. The key enzymes involved in glycolysis and the key molecules in relevant pathways have been used as targets to reverse drug resistance. In this review, we highlight our current understanding of the role of metabolic symbiosis in therapeutic resistance and discuss the ongoing effort to develop metabolic inhibitors as anti-cancer drugs to overcome drug resistance to classical chemotherapy.

Competitive glucose metabolism as a target to boost bladder cancer immunotherapy

Bladder cancer - the tenth most frequent cancer worldwide - has a heterogeneous natural history and clinical behaviour. The predominant histological subtype, urothelial bladder carcinoma, is characterized by high recurrence rates, progression and both primary and acquired resistance to platinum-based therapy, which impose a considerable economic burden on health-care systems and have substantial effects on the quality of life and the overall outcomes of patients with bladder cancer. The incidence of urothelial tumours is increasing owing to population growth and ageing, so novel therapeutic options are vital. Based on work by The Cancer Genome Atlas project, which has identified targetable vulnerabilities in bladder cancer, immune checkpoint inhibitors (ICIs) have arisen as an effective alternative for managing advanced disease. However, although ICIs have shown durable responses in a subset of patients with bladder cancer, the overall response rate is only ~15-25%, which increases the demand for biomarkers of response and therapeutic strategies that can overcome resistance to ICIs. In ICI non-responders, cancer cells use effective mechanisms to evade immune cell antitumour activity; the overlapping Warburg effect machinery of cancer and immune cells is a putative determinant of the immunosuppressive phenotype in bladder cancer. This energetic interplay between tumour and immune cells leads to metabolic competition in the tumour ecosystem, limiting nutrient availability and leading to microenvironmental acidosis, which hinders immune cell function. Thus, molecular hallmarks of cancer cell metabolism are potential therapeutic targets, not only to eliminate malignant cells but also to boost the efficacy of immunotherapy. In this sense, integrating the targeting of tumour metabolism into immunotherapy design seems a rational approach to improve the therapeutic efficacy of ICIs.

The Metabolic Remodelling in Lung Cancer and Its Putative Consequence in Therapy Response

Lung cancer is the leading cause of cancer-related deaths worldwide in both men and women. Conventional chemotherapy has failed to provide long-term benefits for many patients and in the past decade, important advances were made to understand the underlying molecular/genetic mechanisms of lung cancer, allowing the unfolding of several other pathological entities. Considering these molecular subtypes, and the appearance of promising targeted therapies, an effective personalized control of the disease has emerged, nonetheless benefiting a small proportion of patients. Although immunotherapy has also appeared as a new hope, it is still not accessible to the majority of patients with lung cancer.The metabolism of energy and biomass is the basis of cellular survival. This is true for normal cells under physiological conditions and it is also true for pathophysiologically altered cells, such as cancer cells. Thus, knowledge of the metabolic remodelling that occurs in cancer cells in the sense of, on one hand, surviving in the microenvironment of the organ in which the tumour develops and, on the other hand, escaping from drugs conditioned microenvironment, is essential to understand the disease and to develop new therapeutic approaches.

Forkhead Box R2 Knockdown Decreases Chemoresistance to Cisplatin via MYC Pathway in Bladder Cancer

Background

Bladder cancer is a very common urological cancer globally, and cisplatin- or gemcitabine-based chemotherapy is essential for advanced bladder cancer patients. Many patients with bladder cancer have a relatively poor response to chemotherapy, leading to failure of clinical treatment. We mined the GSE77883 GEO dataset, identifying FoxR2 as being a significantly upregulated gene in T24 chemoresistant cells. Herein, we assessed how FoxR2 functions in bladder cancer cell chemoresistance.

Material/Methods

Cisplatin-resistant T24 (T24/DDP) cells were constructed by administering increasing concentrations of cisplatin, and differences in expression of FoxR2 were examined in T24/DDP and T24 cells. FoxR2 loss- and gain-of-function cells models were established in T24/DDP and T24 cells, respectively. Cell survival, clone formation, cell cycle, and cell apoptosis were assessed, and the MYC pathway was verified.

Results

FoxR2 was significantly upregulated in T24/DDP cells compared to T24 cells. Knockdown of FoxR2 in T24/DDP cells, survival rate, and clone formation were decreased, G1/S phase transition was suppressed, and cell apoptosis was promoted. These results were reversed by restoration of FoxR2 levels in T24 cells. We found that FoxR2 knockdown enhanced sensitivity to cisplatin, whereas MYC overexpression antagonized chemosensitivity in T24/DDP cells.

Conclusions

FoxR2 knockdown decreases chemoresistance to cisplatin via the MYC pathway in bladder cancer cells, and this may be a target for overcoming chemoresistance in bladder cancer.

Pyruvate kinase M2: A simple molecule with complex functions

Pyruvate kinase M2 is a critical enzyme that regulates cell metabolism and growth under different physiological conditions. In its metabolic role, pyruvate kinase M2 catalyzes the last glycolytic step which converts phosphoenolpyruvate to pyruvate with the generation of ATP. Beyond this metabolic role in glycolysis, PKM2 regulates gene expression in the nucleus, phosphorylates several essential proteins that regulate major cell signaling pathways, and contribute to the redox homeostasis of cancer cells. The expression of PKM2 has been demonstrated to be significantly elevated in several types of cancer, and the overall inflammatory response. The unusual pattern of PKM2 expression inspired scientists to investigate the unrevealed functions of PKM2 and the therapeutic potential of targeting PKM2 in cancer and other disorders. Therefore, the purpose of this review is to discuss the mechanistic and therapeutic potential of targeting PKM2 with the focus on cancer metabolism, redox homeostasis, inflammation, and metabolic disorders. This review highlights and provides insight into the metabolic and non-metabolic functions of PKM2 and its relevant association with health and disease.