Pyruvate Kinase M2 and Lactate Dehydrogenase A Are Overexpressed in Pancreatic Cancer and Correlate with Poor Outcome

Targeted protein degradation: advances in drug discovery and clinical practice

Targeted protein degradation (TPD) represents a revolutionary therapeutic strategy in disease management, providing a stark contrast to traditional therapeutic approaches like small molecule inhibitors that primarily focus on inhibiting protein function. This advanced technology capitalizes on the cell's intrinsic proteolytic systems, including the proteasome and lysosomal pathways, to selectively eliminate disease-causing proteins. TPD not only enhances the efficacy of treatments but also expands the scope of protein degradation applications. Despite its considerable potential, TPD faces challenges related to the properties of the drugs and their rational design. This review thoroughly explores the mechanisms and clinical advancements of TPD, from its initial conceptualization to practical implementation, with a particular focus on proteolysis-targeting chimeras and molecular glues. In addition, the review delves into emerging technologies and methodologies aimed at addressing these challenges and enhancing therapeutic efficacy. We also discuss the significant clinical trials and highlight the promising therapeutic outcomes associated with TPD drugs, illustrating their potential to transform the treatment landscape. Furthermore, the review considers the benefits of combining TPD with other therapies to enhance overall treatment effectiveness and overcome drug resistance. The future directions of TPD applications are also explored, presenting an optimistic perspective on further innovations. By offering a comprehensive overview of the current innovations and the challenges faced, this review assesses the transformative potential of TPD in revolutionizing drug development and disease management, setting the stage for a new era in medical therapy.

Lactate dehydrogenase B as a metabolism-related marker for immunotherapy in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignancies. Lactate dehydrogenase family genes (LDHs) play a critical role in tumor metabolism, but their functions in HNSCC have not been investigated thoroughly. Thus, we aimed to explore the value of LDHs in HNSCC.

METHODS

The association between LDHs expression and mutations, methylation, copy number variations (CNVs), alternative splicing (AS) and competing endogenous RNA (ceRNA) was investigated in The Cancer Genome Atlas (TCGA). The expression level of LDHs in OSCC tissues and adjacent normal tissues was verified by qPCR. Algorithms, such as ssGSEA, ESTIMATE, xCell and TIDE were utilized to analyze the characteristics of immune infiltration. Pathway alternations were enriched by GO, GSEA and KEGG analysis. The Mantel test was employed to elucidate the correlation between metabolism and the tumor microenvironment (TME). Subsequently, MTT and colony formation assays were utilized to assess the impact of LDHB knockdown on cellular proliferation. Additionally, ATP and lactate assays were performed to examine metabolic alterations. Co-culture experiments further investigated the effect of LDHB knockdown on T cell differentiation.

RESULTS

LDHs were completely analyzed in multiple databases, among which LDHB was differentially expressed in HNSCC and significantly associated with prognosis. Low LDHB expression had better clinicopathological characteristics. Downregulated LDHB expression was associated with enhanced immune cell infiltration and could influence tumor metabolism. Despite having worse cytotoxic T lymphocyte dysfunction, the LDHBlow group was predicted to respond more favorably to immune checkpoint inhibitors (ICIs) therapy. Moreover, the correlation between metabolism and TME was depicted. In vitro, LDHB knockdown resulted in inhibited cell proliferation, increased lactate levels and decreased ATP levels, while promoted the Th1 differentiation of T cells.

CONCLUSIONS

Our study provided a comprehensive analysis of the LDHs and illustrated low LDHB expression could inhibit tumor cell proliferation and ATP production by influencing metabolism, with improved immune cell infiltration and better response to immunotherapy.

The regulatory roles and clinical significance of glycolysis in tumor

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

Metabolism and structure of PDA as the target for new therapies: possibilities and limitations for nanotechnology

INTRODUCTION

Certainly, pancreatic ductal adenocarcinoma poses one of the greatest challenges in current oncology. The dense extracellular matrix and low vessel density in PDA tumor impede the effective delivery of drugs, primarily due to the short pharmacokinetics of most drugs and potential electrostatic interactions with stroma components.

AREA COVERED

Owing to the distinctive metabolism of PDA and challenges in accessing nutrients, there is a growing interest in cell metabolism inhibitors as a potential means to inhibit cancer development. However, even if suitable combinations of inhibitors are identified, the question about their administration remains, as the same hindrances that impede effective treatment with conventional drugs will also hinder the delivery of inhibitors. Methods including nanotechnology to increase drugs in PDA penetrations are reviewed and discussed.

EXPERT OPINION

Pancreatic cancer is one of the most difficult tumors to treat due to the small number of blood vessels, high content of extracellular matrix, and specialized resistance mechanisms of tumor cells. One possible method of treating this tumor is the use of metabolic inhibitors in combinations that show synergy. Despite promising results in in vitro tests, their effect is uncertain due to the tumor's structure. In the case of pancreatic cancer, priming of the tumor tissue is required through the sequential administration of drugs that generate blood vessels, increase blood flow, and enhance vascular permeability and extracellular matrix. The use of drug carriers with a size of 10-30 nm may be crucial in the therapy of this cancer.

An Update on Stiripentol Mechanisms of Action: A Narrative Review

Stiripentol (Diacomit®) (STP) is an orally active antiseizure medication (ASM) indicated as adjunctive therapy, for the treatment of seizures associated with Dravet syndrome (DS), a severe form of childhood epilepsy, in conjunction with clobazam and, in some regions valproic acid. Since the discovery of STP, several mechanisms of action (MoA) have been described that may explain its specific effect on seizures associated with DS. STP is mainly considered as a potentiator of gamma-aminobutyric acid (GABA) neurotransmission: (i) via uptake blockade, (ii) inhibition of degradation, but also (iii) as a positive allosteric modulator of GABAA receptors, especially those containing α3 and δ subunits. Blockade of voltage-gated sodium and T-type calcium channels, which is classically associated with anticonvulsant and neuroprotective properties, has also been demonstrated for STP. Finally, several studies indicate that STP could regulate glucose energy metabolism and inhibit lactate dehydrogenase. STP is also an inhibitor of several cytochrome P450 enzymes involved in the metabolism of other ASMs, contributing to boost their anticonvulsant efficacy as add-on therapy. These different MoAs involved in treatment of DS and recent data suggest a potential for STP to treat other neurological or non-neurological diseases.

Positioning determines function: Wandering PKM2 performs different roles in tumor cells

Short for pyruvate kinase M2 subtype, PKM2 can be said of all-round player that is notoriously known for its metabolic involvement in glycolysis. Holding a dural role as a metabolic or non-metabolic (kinase) enzyme, PKM2 has drawn extensive attention over its biological roles implicated in tumor cells, including proliferation, migration, invasion, metabolism, and so on. wandering PKM2 can be transboundary both intracellularly and extracellularly. Specifically, PKM2 can be nuclear, cytoplasmic, mitochondrial, exosomal, or even circulate within the body. Importantly, PKM2 can function as an RNA-binding protein (RBP) to self-support its metabolic function. Despite extensive investigations or reviews available surrounding the biological roles of PKM2 from different angles in tumor cells, little has been described regarding some novel role of PKM2 that has been recently found, including, for example, acting as RNA-binding protein, protection of Golgi apparatus, and remodeling of microenvironment, and so forth. Given these findings, in this review, we summarize the recent advancements made in PKM2 research, mainly from non-metabolic respects. By the way, PKM1, another paralog of PKM2, seems to have been overlooked or under-investigated since its discovery. Some recent discoveries made about PKM1 are also preliminarily mentioned and discussed.

Recent Advances on PKM2 Inhibitors and Activators in Cancer Applications

Metabolic reprogramming of cells, from the normal mode of glucose metabolism named glycolysis, is a pivotal characteristic of impending cancerous cells. Pyruvate kinase M2 (PKM2), an important enzyme that catalyzes the final rate-limiting stage during glycolysis, is highly expressed in numerous types of tumors and aids in development of favorable conditions for the survival of tumor cells. Increasing evidence has suggested that PKM2 is one of promising targets for innovative drug discovery, especially for the developments of antitumor therapeutics. Herein, we systematically summarize the recent advancement on PKM2 modulators including inhibitors and activators in cancer applications. We also discussed the classifications of pyruvate kinases in mammals and the biological functions of PKM2 in this review. We do hope that this review would provide a comprehensive understanding of the current research on PKM2 modulators, which may benefit the development of more potent PKM2-related drug candidates to treat PKM2-associated diseases including cancers in future.

Integrated transcriptomics, proteomics and metabolomics-based analysis uncover TAM2-associated glycolysis and pyruvate metabolic remodeling in pancreatic cancer

Introduction

Tumor-associated macrophage 2 (TAM2) abundantly infiltrates pancreatic ductal adenocarcinoma (PAAD), and its interaction with malignant cells is involved in the regulation of tumor metabolism. In this study, we explored the metabolic heterogeneity involved in TAM2 by constructing TAM2-associated metabolic subtypes in PAAD.

Materials and methods

PAAD samples were classified into molecular subtypes with different metabolic characteristics based on a multi-omics analysis strategy. 20 PAAD tissues and 10 normal pancreatic tissues were collected for proteomic and metabolomic analyses. RNA sequencing data from the TCGA-PAAD cohort were used for transcriptomic analyses. Immunohistochemistry was used to assess TAM2 infiltration in PAAD tissues.

Results

The results of transcriptomics and immunohistochemistry showed that TAM2 infiltration levels were upregulated in PAAD and were associated with poor patient prognosis. The results of proteomics and metabolomics indicated that multiple metabolic processes were aberrantly regulated in PAAD and that this dysregulation was linked to the level of TAM2 infiltration. WGCNA confirmed pyruvate and glycolysis/gluconeogenesis as co-expressed metabolic pathways of TAM2 in PAAD. Based on transcriptomic data, we classified the PAAD samples into four TAM2-associated metabolic subtypes (quiescent, pyruvate, glycolysis/gluconeogenesis and mixed). Metabolic subtypes were each characterized in terms of clinical prognosis, tumor microenvironment, immune cell infiltration, chemotherapeutic drug sensitivity, and functional mechanisms.

Conclusion

Our study confirmed that the metabolic remodeling of pyruvate and glycolysis/gluconeogenesis in PAAD was closely related to TAM2. Molecular subtypes based on TAM2-associated metabolic pathways provided new insights into prognosis prediction and therapy for PAAD patients.

Correlation of PKM2 Expression With HER2/neu and Additional Breast Cancer Biomarkers and its Prognostic Significance

BACKGROUND

Pyruvate kinase M2 (PKM2) has a central role in both tumor development and metastasis, and it has increasingly become a valuable subject for many cancer studies due to its important prognostic value in various tumor types. In this study, we aimed to elucidate the impact of PKM2 expression level on breast cancer prognosis and survival rates and its association with various clinicopathologic characteristics and tumor markers in breast cancer patients.

MATERIALS AND METHODS

This retrospective study included sample tissues from patients with breast cancer who did not receive chemotherapy or radiotherapy before surgery. Expression levels of PKM2, estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER2), and Ki-67 were analyzed using tissue microarray and immunohistochemistry.

RESULTS

A total of 164 patients were included with an age range from 28 to 82 years. High PKM2 was observed in 48.8% of cases (80/164). A significant association was found between PKM2 expression and breast cancer molecular subtype and HER2 status ( P <0.001). In HER2-negative tumors, there was a significant association between PKM2 expression and tumor grade, TNM stage, pN stage, lymphovascular invasion, and estrogen receptor/progesterone receptor status. Survival analysis revealed that high PKM2 expression levels were associated with decreased overall survival rate in HER2-positive cases with high Ki-67 index. Moreover, in the HER2-positive group, low PKM2 expression level impacted the survival outcome of metastasis ( P =0.002).

CONCLUSIONS

PKM2 is a valuable prognostic and a potential diagnostic and predictive marker in breast cancer. Moreover, the combination of PKM2 with Ki-67 provides excellent prognostic accuracy in HER2-positive tumors.

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.

Effectiveness for Diagnosis of Malignancy of Bile Pyruvate Kinase M2 in Patients with Indeterminate Biliary Stricture

BACKGROUND

Up to 70% of the cases of biliary strictures are cholangiocarcinoma. Cholangiocarcinoma has a late diagnosis and poor outcomes; therefore, effective biomarkers are needed for malignant lesions detection at earlier stages.

AIM

The aim was to assess the diagnostic utility of bile pyruvate kinase M2 (PKM2) as a biomarker for the detection of malignant biliary strictures in patients with an indeterminate biliary stricture.

MATERIALS AND METHODS

This is a prospective study to evaluate the diagnostic value of bile PKM2 for the diagnosis of malignant biliary strictures. Bile samples were collected during Endoscopic Retrograde Cholangio Pancreatography to quantify PKM2 levels and were used to compare their diagnostic value with biliary brush cytology, endoscopic ultrasound-guided fine needle biopsy, or clinical follow-up.

RESULTS

Forty-six patients were recruited for the study; 19 patients with malignant strictures and 27 with benign biliary strictures. The bile PKM2 levels were elevated in patients with malignant biliary strictures [median 0.045 ng/mL (IQR 0.014 to 0.092)] compared with those with benign strictures [median 0.019 ng/mL (IQR 0.00 to 0.047)]. Bile PKM2 had a receiver-operating characteristic curve of 0.66 (0.49 to 0.83) with a cutoff value of bile PKM2 of 0.0017 ng/mL. The sensitivity and specificity of bile PKM2 for the diagnosis of cholangiocarcinoma were 89% and 26%; the positive and negative predictive values were 46% and 78%, respectively.

CONCLUSION

In patients with indeterminate biliary strictures, bile PKM2 may be a potential biomarker for the diagnosis of malignancy.

Modulating Glycolysis to Improve Cancer Therapy

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

Target c-Myc to treat pancreatic cancer

C-Myc overexpression is a common finding in pancreatic cancer and predicts the aggressive behavior of cancer cells. It binds to the promoter of different genes, thereby regulating their transcription. C-Myc is downstream of KRAS and interacts with several oncogenic and proliferative pathways in pancreatic cancer. C-Myc enhances aerobic glycolysis in cancer cells and regulates glutamate biosynthesis from glutamine. It provides enough energy for cancer cells' metabolism and sufficient substrate for the synthesis of organic molecules. C-Myc overexpression is associated with chemoresistance, intra-tumor angiogenesis, epithelial-mesenchymal transition (EMT), and metastasis in pancreatic cancer. Despite its title, c-Myc is not "undruggable" and recent studies unveiled that it can be targeted, directly or indirectly. Small molecules that accelerate c-Myc ubiquitination and degradation have been effective in preclinical studies. Small molecules that hinder c-Myc-MAX heterodimerization or c-Myc/MAX/DNA complex formation can functionally inhibit c-Myc. In addition, c-Myc can be targeted through transcriptional, post-transcriptional, and translational modifications.

Lactate Dehydrogenase and its clinical significance in pancreatic and thoracic cancers

The energy metabolism of tumor cells is considered one of the hallmarks of cancer because it is different from normal cells and mainly consists of aerobic glycolysis, fatty acid oxidation, and glutaminolysis. It is about one hundred years ago since Warburg observed that cancer cells prefer aerobic glycolysis even in normoxic conditions, favoring their high proliferation rate. A pivotal enzyme driving this phenomenon is lactate dehydrogenase (LDH), and this review describes prognostic and therapeutic opportunities associated with this enzyme, focussing on tumors with limited therapeutic strategies and life expectancy (i.e., pancreatic and thoracic cancers). Expression levels of LDH-A in pancreatic cancer tissues correlate with clinicopathological features: LDH-A is overexpressed during pancreatic carcinogenesis and showed significantly higher expression in more aggressive tumors. Similarly, LDH levels are a marker of negative prognosis in patients with both adenocarcinoma or squamous cell lung carcinoma, as well as in malignant pleural mesothelioma. Additionally, serum LDH levels may play a key role in the clinical management of these diseases because they are associated with tissue damage induced by tumor burden. Lastly, we discuss the promising results of strategies targeting LDH as a treatment strategy, reporting recent preclinical and translational studies supporting the use of LDH-inhibitors in combinations with current/novel chemotherapeutics that can synergistically target the oxygenated cells present in the tumor.

Strategies for drug targeting in pancreatic cancer

BACKGROUND

Pancreatic cancer is expected to replace lung cancer as the second greatest cause of cancer mortality by 2025. It has been a particularly the most lethal kind of cancer.

OBJECTIVE

Despite the new innovations, research, and improvements in drug design; there are many hurdles limiting their therapeutic applications such as intrinsic resistance to chemotherapeutics, inability to deliver a sufficient concentration of drug to the target site, lack of effectiveness of drug delivery systems. These are the major contributing factors to limit the treatment. So, the main objective is to overcome these types of problems by nanotechnology and ligand conjugation approach to achieve targeted drug delivery.

METHOD

Nanotechnology has emerged as a major approach to develop cancer treatment. Regardless of the severity, there are several issues that restrict the therapeutic impact, including inadequate transport across biological barriers, limited cellular absorption, degradation, and faster clearance.

RESULT

Targeted drug delivery may overcome these obstacles by binding a natural ligand to the surface of nanocarriers, which enhances the drug's capacity to release at the desired site and minimizes adverse effects.

CONCLUSION

This study will investigate the possible outcomes of targeted therapeutic agent delivery in the treatment of pancreatic cancer, as well as the limitations and future prospects.

Warburg effect in colorectal cancer: the emerging roles in tumor microenvironment and therapeutic implications

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death worldwide. Countless CRC patients undergo disease progression. As a hallmark of cancer, Warburg effect promotes cancer metastasis and remodels the tumor microenvironment, including promoting angiogenesis, immune suppression, cancer-associated fibroblasts formation and drug resistance. Targeting Warburg metabolism would be a promising method for the treatment of CRC. In this review, we summarize information about the roles of Warburg effect in tumor microenvironment to elucidate the mechanisms governing Warburg effect in CRC and to identify novel targets for therapy.

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.

Transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor-resistant pancreatic ductal adenocarcinoma

Metabolic reprogramming, due in part to the overexpression of metabolic enzymes, is a key hallmark of cancer cells. Lactate dehydrogenase (LDHA), a metabolic enzyme that catalyzes the interconversion of lactate and pyruvate, is overexpressed in a wide variety of cancer types, including pancreatic ductal adenocarcinoma (PDAC). Furthermore, the genetic or pharmacological inhibition of LDHA suppresses cancer growth, demonstrating a cancer-promoting role for this enzyme. Therefore, several pharmacological LDHA inhibitors are being developed and tested as potential anti-cancer therapeutic agents. Because cancer cells are known to rapidly adapt and become resistant to anti-cancer therapies, in this study, we modeled the adaptation of cancer cells to LDHA inhibition. Using PDAC as a model system, we studied the molecular aspects of cells resistant to the competitive LDHA inhibitor sodium oxamate. We performed unbiased RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), and metabolomics analyses of parental and oxamate-resistant PDAC cells treated with and without oxamate to identify the transcriptional, chromatin, and metabolic landscapes of these cells. We found that oxamate-resistant PDAC cells were significantly different from parental cells at the levels of mRNA expression, chromatin accessibility, and metabolites. Additionally, an integrative analysis combining the RNA-seq and ATAC-seq datasets identified a subset of differentially expressed mRNAs that directly correlated with changes in chromatin accessibility. Finally, functional analysis of differentially expressed metabolic genes in parental and oxamate-resistant PDAC cells treated with and without oxamate, together with an integrative analysis of RNA-seq and metabolomics data, revealed changes in metabolic enzymes that might explain the changes in metabolite levels observed in these cells. Collectively, these studies identify the transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor resistance in PDAC cells. Future functional studies related to these changes remain necessary to reveal the direct roles played by these changes in the development of LDHA inhibitor resistance and uncover approaches for more effective use of LDHA inhibitors in cancer therapy.

Exploring the metabolic landscape of pancreatic ductal adenocarcinoma cells using genome-scale metabolic modeling

Pancreatic ductal adenocarcinoma (PDAC) is a major research focus because of its poor therapy response and dismal prognosis. PDAC cells adapt their metabolism to the surrounding environment, often relying on diverse nutrient sources. Because traditional experimental techniques appear exhaustive to find a viable therapeutic strategy, a highly curated and omics-informed PDAC genome-scale metabolic model was reconstructed using patient-specific transcriptomics data. From the model-predictions, several new metabolic functions were explored as potential therapeutic targets in addition to the known metabolic hallmarks of PDAC. Significant downregulation in the peroxisomal beta oxidation pathway, flux modulation in the carnitine shuttle system, and upregulation in the reactive oxygen species detoxification pathway reactions were observed. These unique metabolic traits of PDAC were correlated with potential drug combinations targeting genes with poor prognosis in PDAC. Overall, this study provides a better understanding of the metabolic vulnerabilities in PDAC and will lead to novel effective therapeutic strategies.

Glycolysis in the progression of pancreatic cancer

Metabolic reprogramming, as a key hallmark of cancers, leads to the malignant behavior of pancreatic cancer, which is closely related to tumor development and progression, as well as the supportive tumor microenvironments. Although cells produce adenosine triphosphate (ATP) from glucose by glycolysis when lacking oxygen, pancreatic cancer cells elicit metabolic conversion from oxide phosphorylation to glycolysis, which is well-known as "Warburg effect". Glycolysis is critical for cancer cells to maintain their robust biosynthesis and energy requirement, and it could promote tumor initiation, invasion, angiogenesis, and metastasis to distant organs. Multiple pathways are involved in the alternation of glycolysis for pancreatic cancer cells, including UHRF1/SIRT4 axis, PRMT5/FBW7/cMyc axis, JWA/AMPK/FOXO3a/FAK axis, KRAS/TP53/TIGAR axis, etc. These signaling pathways play an important role in glycolysis and are potential targets for the treatment of pancreatic cancer. Mutations in glycolytic enzymes (such as LDH, PKM2, and PGK1) also contribute to the early diagnosis and monitoring of pancreatic cancer. In this review, we summarized the recent advances on the mechanisms for glycolysis in pancreatic cancer and the function of glycolysis in the progression of pancreatic cancer, which suggested new targets for cancer diagnosis and treatment.

Tumor-associated macrophages promote PD-L1 expression in tumor cells by regulating PKM2 nuclear translocation in pancreatic ductal adenocarcinoma

In many types of cancer, tumor cells prefer to use glycolysis as a major energy acquisition method. Here, we found that the 18fluoro-deoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT)-based markers were positively associated with the expression of programmed cell death ligand 1 (PD-L1), pyruvate kinase M2 (PKM2), both of which indicate poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC). However, the regulatory mechanism of PD-L1 remains elusive. In this study, we confirmed that transforming growth factor-beta1 (TGF-β1) secreted by tumor-associated macrophages (TAMs) was a key factor contributing to the expression of PD-L1 in PDAC cells by inducing the nuclear translocation of PKM2. Using co-immunoprecipitation and chromatin immunoprecipitation assays, we demonstrated that the interaction between PKM2 and signal transducer and activator of transcription 1 (STAT1) was enhanced by TGF-β1 stimulation, which facilitated the transactivation of PD-L1 by the binding of PKM2 and STAT1 to its promoter. In vivo, PKM2 knockdown decreased PD-L1 expression in PDAC cells and inhibited tumor growth partly by promoting natural killer cell activation and function, and the combination of PD-1/PD-L1 blockade with PKM2 knockdown limited tumor growth. In conclusion, PKM2 significantly contributes to TAM-induced PD-L1 overexpression and immunosuppression, providing a novel target for immunotherapies for PDAC.

The role of metabolic ecosystem in cancer progression — metabolic plasticity and mTOR hyperactivity in tumor tissues

Despite advancements in cancer management, tumor relapse and metastasis are associated with poor outcomes in many cancers. Over the past decade, oncogene-driven carcinogenesis, dysregulated cellular signaling networks, dynamic changes in the tissue microenvironment, epithelial-mesenchymal transitions, protein expression within regulatory pathways, and their part in tumor progression are described in several studies. However, the complexity of metabolic enzyme expression is considerably under evaluated. Alterations in cellular metabolism determine the individual phenotype and behavior of cells, which is a well-recognized hallmark of cancer progression, especially in the adaptation mechanisms underlying therapy resistance. In metabolic symbiosis, cells compete, communicate, and even feed each other, supervised by tumor cells. Metabolic reprogramming forms a unique fingerprint for each tumor tissue, depending on the cellular content and genetic, epigenetic, and microenvironmental alterations of the developing cancer. Based on its sensing and effector functions, the mechanistic target of rapamycin (mTOR) kinase is considered the master regulator of metabolic adaptation. Moreover, mTOR kinase hyperactivity is associated with poor prognosis in various tumor types. In situ metabolic phenotyping in recent studies highlights the importance of metabolic plasticity, mTOR hyperactivity, and their role in tumor progression. In this review, we update recent developments in metabolic phenotyping of the cancer ecosystem, metabolic symbiosis, and plasticity which could provide new research directions in tumor biology. In addition, we suggest pathomorphological and analytical studies relating to metabolic alterations, mTOR activity, and their associations which are necessary to improve understanding of tumor heterogeneity and expand the therapeutic management of cancer.

Metabolic syndrome related gene signature predicts the prognosis of patients with pancreatic ductal carcinoma. A novel link between metabolic dysregulation and pancreatic ductal carcinoma

Background

Pancreatic cancer is one of the most common malignancies worldwide. In recent years, specific metabolic activities, which involves the development of tumor, caused wide public concern. In this study, we wish to explore the correlation between metabolism and progression of tumor.

Methods

A retrospective analysis including 95 patients with pancreatic ductal adenocarcinoma (PDAC) and PDAC patients from The Cancer Genome Atlas (TCGA), the International Cancer Genome Consortium (ICGC), and The Gene Expression Omnibus (GEO) database were involved in our study. Multivariate Cox regression analysis was used to construct the prognosis model. The potential connection between metabolism and immunity of PDAC was investigated through a weighted gene co-expression network analysis (WGCNA). 22 types of Tumor-infiltrating immune cells (TIICs) between high-risk and low-risk groups were estimated through CIBERSORT. Moreover, the potential immune-related signaling pathways between high-risk and low-risk groups were explored through the gene set enrichment analysis (GSEA). The role of key gene GMPS in developing pancreatic tumor was further investigated through CCK-8, colony-information, and Transwell.

Results

The prognostic value of the MetS factors was analyzed using the Cox regression model, and a clinical MetS-based nomogram was established. Then, we established a metabolism-related signature to predict the prognosis of PDAC patients based on the TCGA databases and was validated in the ICGC database and the GEO database to find the distinct molecular mechanism of MetS genes in PDAC. The result of WGCNA showed that the blue module was associated with risk score, and genes in the blue module were found to be enriched in the immune-related signaling pathway. Furthermore, the result of CIBERSORT demonstrated that proportions of T cells CD8, T cells Regulatory, Tregs NK cells Activated, Dendritic cells Activated, and Mast cells Resting were different between high-risk and low-risk groups. These differences are potential causes of different prognoses of PDAC patients. GSEA and the protein–protein interaction network (PPI) further revealed that our metabolism-related signature was significantly enriched in immune‐related biological processes. Moreover, knockdown of GMPS in PDAC cells suppressed proliferation, migration, and invasion of tumor cells, whereas overexpression of GMPS performed oppositely.

Conclusion

The results shine light on fundamental mechanisms of metabolic genes on PDAC and establish a reliable and referable signature to evaluate the prognosis of PDAC. GMPS was identified as a potential candidate oncogene with in PDAC, which can be a novel biomarker and therapeutic target for PDAC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02378-w.

Glycometabolic rearrangements-aerobic glycolysis in pancreatic ductal adenocarcinoma (PDAC): roles, regulatory networks, and therapeutic potential

INTRODUCTION

Glycometabolic rearrangements (aerobic glycolysis) is a hallmark of pancreatic ductal adenocarcinoma (PDAC) and contributes to tumorigenesis and progression through numerous mechanisms. The targeting of aerobic glycolysis is recognized as a potential therapeutic strategy which offers the possibility of improving treatment outcomes for PDAC patients.

AREAS COVERED

In this review, the role of aerobic glycolysis and its regulatory networks in PDAC are discussed. The targeting of aerobic glycolysis in PDAC is examined, and its therapeutic potential is evaluated. The relevant literature published from 2001 to 2021 was searched in databases including PubMed, Scopus, and Embase.

EXPERT OPINION

Regulatory networks of aerobic glycolysis in PDAC are based on key factors such as c-Myc, hypoxia-inducible factor 1α, the mammalian target of rapamycin pathway, and non-coding RNAs. Experimental evidence suggests that modulators or inhibitors of aerobic glycolysis promote therapeutic effects in preclinical tumor models. Nevertheless, successful clinical translation of drugs that target aerobic glycolysis in PDAC is an obstacle. Moreover, it is necessary to identify the potential targets for future interventions from regulatory networks to design efficacious and safer agents.

Therapeutic resistance in pancreatic ductal adenocarcinoma: Current challenges and future opportunities

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related deaths in the United States. Although chemotherapeutic regimens such as gemcitabine+ nab-paclitaxel and FOLFIRINOX (FOLinic acid, 5-Fluroruracil, IRINotecan, and Oxaliplatin) significantly improve patient survival, the prevalence of therapy resistance remains a major roadblock in the success of these agents. This review discusses the molecular mechanisms that play a crucial role in PDAC therapy resistance and how a better understanding of these mechanisms has shaped clinical trials for pancreatic cancer chemotherapy. Specifically, we have discussed the metabolic alterations and DNA repair mechanisms observed in PDAC and current approaches in targeting these mechanisms. Our discussion also includes the lessons learned following the failure of immunotherapy in PDAC and current approaches underway to improve tumor's immunological response.

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.

ETV4 promotes breast cancer cell stemness by activating glycolysis and CXCR4-mediated sonic Hedgehog signaling

Cancer stem cells (CSCs) are a major cause of tumor treatment resistance, relapse and metastasis. Cancer cells exhibit reprogrammed metabolism characterized by aerobic glycolysis, which is also critical for sustaining cancer stemness. However, regulation of cancer cell metabolism rewiring and stemness is not completely understood. Here, we report that ETV4 is a key transcription factor in regulating glycolytic gene expression. ETV4 loss significantly inhibits the expression of HK2, LDHA as well as other glycolytic enzymes, reduces glucose uptake and lactate release in breast cancer cells. In human breast cancer and hepatocellular carcinoma tissues, ETV4 expression is positively correlated with glycolytic signaling. Moreover, we confirm that breast CSCs (BCSCs) are glycolysis-dependent and show that ETV4 is required for BCSC maintenance. ETV4 is enriched in BCSCs, its knockdown and overexpression suppresses and promotes breast cancer cell stem-like traits, respectively. Mechanistically, on the one hand, we find that ETV4 may enhance glycolysis activity to facilitate breast cancer stemness; on the other, ETV4 activates Sonic Hedgehog signaling by transcriptionally promoting CXCR4 expression. A xenograft assay validates the tumor growth-impeding effect and inhibition of CXCR4/SHH/GLI1 signaling cascade after ETV4 depletion. Together, our study highlights the potential roles of ETV4 in promoting cancer cell glycolytic shift and BCSC maintenance and reveals the molecular basis.

Inhibition of β-Catenin Activity Abolishes LKB1 Loss-Driven Pancreatic Cystadenoma in Mice

Pancreatic cancer (PC) is the seventh leading cause of cancer death worldwide, and remains one of our most recalcitrant and dismal diseases. In contrast to many other malignancies, there has not been a significant improvement in patient survival over the past decade. Despite advances in our understanding of the genetic alterations associated with this disease, an incomplete understanding of the underlying biology and lack of suitable animal models have hampered efforts to develop more effective therapies. LKB1 is a tumor suppressor that functions as a primary upstream kinase of adenine monophosphate-activated protein kinase (AMPK), which is an important mediator in the regulation of cell growth and epithelial polarity pathways. LKB1 is mutated in a significant number of Peutz–Jeghers syndrome (PJS) patients and in a small proportion of sporadic cancers, including PC; however, little is known about how LKB1 loss contributes to PC development. Here, we report that a reduction in Wnt/β-catenin activity is associated with LKB1 tumor-suppressive properties in PC. Remarkably, in vivo functional analyses of β-catenin in the Pdx-1-Cre LKB1^L/L β-catenin^L/L mouse model compared to LKB1 loss-driven cystadenoma demonstrate that the loss of β-catenin impairs cystadenoma development in the pancreas of Pdx-1Cre LKB1^L/L mice and dramatically restores the normal development and functions of the pancreas. This study further determined the in vivo and in vitro therapeutic efficacy of the β-catenin inhibitor FH535 in suppressing LKB1 loss-driven cystadenoma and reducing PC progression that delineates the potential roles of Wnt/β-catenin signaling in PC harboring LKB1 deficiency.

Mechanism of PKM2 affecting cancer immunity and metabolism in Tumor Microenvironment

PKM2 is the enzyme that regulates the final rate-limiting step of glycolysis. PKM2 expression can reinforce the utilization of oxygen and synthesis of growth substances in cancer cells by enhancing OXPHOS and the Warburg effect. In cancer immunity, PKM2 can modulate the expression of PD-L1 in M2 macrophage and decrease the amount and activity of CD8+ T cells. This affects cancer cell killing and immune escape sequentially. How PKM2 regulates PD-L1 expression through immunometabolism is summarized. PKM2 builds a bridge between energy metabolism and cancer immunity. The activator and inhibitor of PKM2 both promote the anti-cancer immune response and inhibit cancer growth and metastasis by regulating the metabolism of cancer cells and immune cells in the tumor microenvironment through HIF-1α/PKM2 pathway. This review focuses on the precise role of PKM2 modulating immunometabolism, providing valuable suggestions for further study in this field.

The Glycolytic Pathway as a Target for Novel Onco-Immunology Therapies in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal forms of human cancer, characterized by unrestrained progression, invasiveness and treatment resistance. To date, there are limited curative options, with surgical resection as the only effective strategy, hence the urgent need to discover novel therapies. A platform of onco-immunology targets is represented by molecules that play a role in the reprogrammed cellular metabolism as one hallmark of cancer. Due to the hypoxic tumor microenvironment (TME), PDA cells display an altered glucose metabolism-resulting in its increased uptake-and a higher glycolytic rate, which leads to lactate accumulation and them acting as fuel for cancer cells. The consequent acidification of the TME results in immunosuppression, which impairs the antitumor immunity. This review analyzes the genetic background and the emerging glycolytic enzymes that are involved in tumor progression, development and metastasis, and how this represents feasible therapeutic targets to counteract PDA. In particular, as the overexpressed or mutated glycolytic enzymes stimulate both humoral and cellular immune responses, we will discuss their possible exploitation as immunological targets in anti-PDA therapeutic strategies.

Role of different immune cells and metabolic pathways in modulating the immune response in pancreatic cancer (Review)

Pancreatic cancer is an aggressive cancer, making it a leading cause of cancer‑related deaths. It is characteristically resistant to treatment, which results in low survival rates. In pancreatic cancer, immune cells undergo transitions that can inhibit or promote their functions, enabling treatment resistance and tumor progression. These transitions can be fostered by metabolic pathways that are dysregulated during tumorigenesis. The present review aimed to summarize the different immune cells and their roles in pancreatic cancer. The review also highlighted the individual metabolic pathways in pancreatic cancer and how they enable transitions in immune cells. Finally, the potential of targeting metabolic pathways for effective therapeutic strategies was considered.

Glycometabolic rearrangements--aerobic glycolysis in pancreatic cancer: causes, characteristics and clinical applications

Pancreatic cancer is one of the most malignant tumors worldwide, and pancreatic ductal adenocarcinoma is the most common type. In pancreatic cancer, glycolysis is the primary way energy is produced to maintain the proliferation, invasion, migration, and metastasis of cancer cells, even under normoxia. However, the potential molecular mechanism is still unknown. From this perspective, this review mainly aimed to summarize the current reasonable interpretation of aerobic glycolysis in pancreatic cancer and some of the newest methods for the detection and treatment of pancreatic cancer. More specifically, we reported some biochemical parameters, such as newly developed enzymes and transporters, and further explored their potential as diagnostic biomarkers and therapeutic targets.

Targets (Metabolic Mediators) of Therapeutic Importance in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The higher mortality in PDAC is often attributed to the inability to detect it until it has reached advanced stages. The major challenge in tackling PDAC is due to its elusive pathology, minimal effectiveness, and resistance to existing therapeutics. The aggressiveness of PDAC is due to the capacity of tumor cells to alter their metabolism, utilize the diverse available fuel sources to adapt and grow in a hypoxic and harsh environment. Therapeutic resistance is due to the presence of thick stroma with poor angiogenesis, thus making drug delivery to tumor cells difficult. Investigating the metabolic mediators and enzymes involved in metabolic reprogramming may lead to the identification of novel therapeutic targets. The metabolic mediators of glucose, glutamine, lipids, nucleotides, amino acids and mitochondrial metabolism have emerged as novel therapeutic targets. Additionally, the role of autophagy, macropinocytosis, lysosomal transport, recycling, amino acid transport, lipid transport, and the role of reactive oxygen species has also been discussed. The role of various pro-inflammatory cytokines and immune cells in the pathogenesis of PDAC and the metabolites involved in the signaling pathways as therapeutic targets have been previously discussed. This review focuses on the therapeutic potential of metabolic mediators in PDAC along with stemness due to metabolic alterations and their therapeutic importance.

Therapeutic Strategies Toward Lactate Dehydrogenase Within the Tumor Microenvironment of Pancreatic Cancer

OBJECTIVES

Pancreatic stellate cells (PSCs) play a key metabolic role within the tumor microenvironment (stroma) of pancreatic ductal adenocarcinoma (PDAC), being glycolytic and associated with protumorigenic acidification from excess lactate. This study investigates the clinical significance of glycolytic enzyme lactate dehydrogenase (LDH) and determines efficacy of the novel pan-LDH inhibitor Galloflavin.

METHODS

An in vitro Transwell system was adopted for coculture of PSCs and 3 PDAC cell lines (MIA PaCa-2, PANC-1, and BxPC-3). Cells were treated with Galloflavin, and outcomes were analyzed regarding proliferation, apoptosis, lactate production, and glycolytic enzyme protein expression. Immunohistochemical staining for lactate dehydrogenase B (LDHB) was performed on 59 resected PDAC tumors annotated for clinical outcome.

RESULTS

Galloflavin reduced PDAC proliferation in monoculture (P < 0.01); however, in co-culture with PSCs, an antiproliferative effect was only evident in PANC-1 (P = 0.001). An apoptotic effect was observed in MIA PaCa-2 and BxPC-3 in coculture (P < 0.05). A reduction in media lactate was observed in coculture (P < 0.01) with PSCs. Immunohistochemistry revealed stromal and tumoral LDHB expression had no impact on survival.

CONCLUSIONS

Galloflavin has the potential to neutralize the acidic PDAC microenvironment and thereby reduce tumor invasiveness and metastasis. Patients with lower LDHB expression are more likely to be beneficial responders.

Lactate dehydrogenase A inhibition by small molecular entities: steps in the right direction

Direct targeting of energy metabolism to defeat cancer is not a recent strategy. Although quite a few drugs use cellular metabolism for their antitumor effect, no direct inhibitors of energy metabolism have been approved by the FDA. Currently, several inhibitors of lactate dehydrogenase A (LDH-A), a key player in glycolysis, are in development. Earlier, we demonstrated the efficacy of N-hydroxyindole-based LDH-A inhibitors in different cancer types. In this study we describe the efficacy of NHI-Glc-2, which is designed to dual target cancer cells, by exploiting a simultaneous enhanced glucose uptake by overexpressed glucose transporter 1 (GLUT1) and by inhibition of LDH-A. NHI-Glc-2 inhibits LDH-A enzyme activity, PANC-1 cell growth and disrupts spheroid integrity, with an overall effect that is more pronounced when combined with gemcitabine.

FAM46B Promotes Apoptosis and Inhibits Glycolysis of Prostate Cancer Through Inhibition of the MYC-LDHA Axis

Objective

Increased dependence on glycolysis is a known element of cancer. This study was designed to examine critical glycolysis components including transcription factor MYC and its downstream target lactate dehydrogenase A (LDHA), potential upstream regulators of glycolysis such as family with sequence similarity 46 member B (FAM46B), and the impact of the abundance of these proteins on apoptosis and glycolysis in prostate cancer.

Materials and Methods

A total of 70 primary prostate cancer patient samples were compared to normal tissues for FAM46B and LDHA expression and the corresponding patients’ survival was monitored for 60 months. Prostate cancer cell lines were employed for protein expression manipulation, glucose uptake and LDH assays, and apoptosis measurements. A xenograft mouse model was used to quantify the role of FAM46B and LDHA on tumor growth in vivo.

Results

FAM46B expression was reduced in prostate tumor tissue compared to normal tissue and prostate cancer patients who expressed low amounts of FAM46B had shortened average lifespans compared to those who expressed higher amounts of FAM46B (p=0.008). FAM46B overexpression reduced glucose uptake, decreased LDH activity, and induced apoptosis in prostate cancer cell lines while FAM46B shRNA increased MYC levels in a non-malignant prostate cell line (P69). Conversely, forced expression of LDHA in LNCaP cells produced an increase in glycolysis markers with a corresponding decrease in apoptosis. FAM46B-overexpressing xenografts had starkly blunted growth which was restored with co-overexpression of LDHA.

Conclusion

FAM46B plays a central role in regulating glycolysis and apoptosis in prostate cancer and operates through the regulation of LDHA via MYC. FAM46B’s keystone status in prostate cancer makes it a potential, robust biomarker for prostate cancer prognosis and a promising therapeutic target.

Ribosomal protein S3 selectively affects colon cancer growth by modulating the levels of p53 and lactate dehydrogenase

Ribosomal protein S3 (RPS3) is a component of the 40S ribosomal subunit. It is known to function in ribosome biogenesis and as an endonuclease. RPS3 has been shown to be over expressed in colon adenocarcinoma but its role in colon cancer is still unknown. In this study, we aim at determining the expression levels of RPS3 in a colon cancer cell line Caco-2 compared to a normal colon mucosa cell line NCM-460 and study the effects of targeting this protein by siRNA on cellular behavior. RPS3 was found to be expressed in both cell lines. However, siRNA treatment showed a more protruding effect on Caco-2 cells compared to NCM-460 cells. RPS3 knockdown led to a significant decrease in the proliferation, survival, migration and invasion and an increase in the apoptosis of Caco-2 cells. Western blot analysis demonstrated that these effects correlated with an increase in the level of the tumor suppressor p53 and a decrease in the level and activity of lactate dehydrogenase (LDH), an enzyme involved in the metabolism of cancer cells. No significant effect was shown in normal colon NCM-460 cells. Targeting p53 by siRNA did not affect RPS3 levels indicating that p53 may be a downstream target of RPS3. However, the concurrent knockdown of RPS3 and p53 showed no change in LDH level in Caco-2 cells suggesting an interesting interplay among the three proteins. These findings might present RPS3 as a selective molecular marker in colon cancer and an attractive target for colon cancer therapy.

Clinical and Pre-Clinical Evidence of Carbonic Anhydrase IX in Pancreatic Cancer and Its High Expression in Pre-Cancerous Lesions

Hypoxia is a common phenomenon that occurs in most solid tumors. Regardless of tumor origin, the evolution of a hypoxia-adapted phenotype is critical for invasive cancer development. Pancreatic ductal adenocarcinoma is also characterized by hypoxia, desmoplasia, and the presence of necrosis, predicting poor outcome. Carbonic anhydrase IX (CAIX) is one of the most strict hypoxia regulated genes which plays a key role in the adaptation of cancer cells to hypoxia and acidosis. Here, we summarize clinical data showing that CAIX expression is associated with tumor necrosis, vascularization, expression of Frizzled-1, mucins, or proteins involved in glycolysis, and inevitably, poor prognosis of pancreatic cancer patients. We also describe the transcriptional regulation of CAIX in relation to signaling pathways activated in pancreatic cancers. A large part deals with the preclinical evidence supporting the relevance of CAIX in processes leading to the aggressive behavior of pancreatic tumors. Furthermore, we focus on CAIX occurrence in pre-cancerous lesions, and for the first time, we describe CAIX expression within intraductal papillary mucinous neoplasia. Our review concludes with a detailed account of clinical trials implicating that treatment consisting of conventionally used therapies combined with CAIX targeting could result in an improved anti-cancer response in pancreatic cancer patients.

The dichotomous role of the glycolytic metabolism pathway in cancer metastasis: Interplay with the complex tumor microenvironment and novel therapeutic strategies

Cancer metastasis to distant organs is initiated by tumor cells that disseminate from primary heterogeneous tumors. The subsequent growth and survival of tumor metastases depend on different metabolic changes, which constitute one of the enigmatic properties of tumor cells. Aerobic glycolysis, 'the Warburg effect', contributes to tumor energy supply, by oxidizing glucose in a faster manner compared to oxidative phosphorylation, leading to an increased lactate production by lactate dehydrogenase A (LDH-A), which in turn affects the immune response. Surrounding stromal cells contribute to feedback mechanisms further prompting the acquisition of pro-invasive metabolic features. Hence, therapeutic strategies targeting the glycolytic pathway are intensively investigated, with a special interest on their anti-metastatic properties. Various small molecules, such as LDH-A inhibitors, have shown pre-clinical activity against different cancer types, and blocking LDH-A could also help in designing future complimentary therapies. Modulation of specific targets in cells with an altered glycolytic metabolism should indeed result in a milder and distinct toxicity profile, compared to conventional cytotoxic therapy, while a combination treatment with vitamin C leading to increasing reactive oxygen species levels, should further inhibit cancer cell survival and invasion. In this review we describe the impact of metabolic reprogramming in cancer metastasis, the contribution of lactate in this aberrant process and its effect on oncogenic processes. Furthermore, we discuss experimental compounds that target glycolytic metabolism, such as LDH-A inhibitors, and their potential to improve current and experimental therapeutics against metastatic tumors.

Metabolic Fitness and Plasticity in Cancer Progression

Cancer cells have enhanced metabolic needs due to their rapid proliferation. Moreover, throughout their progression from tumor precursors to metastases, cancer cells face challenging physiological conditions, including hypoxia, low nutrient availability, and exposure to therapeutic drugs. The ability of cancer cells to tailor their metabolic activities to support their energy demand and biosynthetic needs throughout disease progression is key for their survival. Here, we review the metabolic adaptations of cancer cells, from primary tumors to therapy resistant cancers, and the mechanisms underpinning their metabolic plasticity. We also discuss the metabolic coupling that can develop between tumors and the tumor microenvironment. Finally, we consider potential metabolic interventions that could be used in combination with standard therapeutic approaches to improve clinical outcome.

Cutting off the fuel supply to calcium pumps in pancreatic cancer cells: role of pyruvate kinase-M2 (PKM2)

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has poor survival and treatment options. PDAC cells shift their metabolism towards glycolysis, which fuels the plasma membrane calcium pump (PMCA), thereby preventing Ca2+-dependent cell death. The ATP-generating pyruvate kinase-M2 (PKM2) is oncogenic and overexpressed in PDAC. This study investigated the PKM2-derived ATP supply to the PMCA as a potential therapeutic locus.

METHODS

PDAC cell growth, migration and death were assessed by using sulforhodamine-B/tetrazolium-based assays, gap closure assay and poly-ADP ribose polymerase (PARP1) cleavage, respectively. Cellular ATP and metabolism were assessed using luciferase/fluorescent-based assays and the Seahorse XFe96 analyzer, respectively. Cell surface biotinylation identified membrane-associated proteins. Fura-2 imaging was used to assess cytosolic Ca2+ overload and in situ Ca2+ clearance. PKM2 knockdown was achieved using siRNA.

RESULTS

The PKM2 inhibitor (shikonin) reduced PDAC cell proliferation, cell migration and induced cell death. This was due to inhibition of glycolysis, ATP depletion, inhibition of PMCA and cytotoxic Ca2+ overload. PKM2 associates with plasma membrane proteins providing a privileged ATP supply to the PMCA. PKM2 knockdown reduced PMCA activity and reduced the sensitivity of shikonin-induced cell death.

CONCLUSIONS

Cutting off the PKM2-derived ATP supply to the PMCA represents a novel therapeutic strategy for the treatment of PDAC.

Cysteine catabolism and the serine biosynthesis pathway support pyruvate production during pyruvate kinase knockdown in pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with limited treatment options. Pyruvate kinase, especially the M2 isoform (PKM2), is highly expressed in PDAC cells, but its role in pancreatic cancer remains controversial. To investigate the role of pyruvate kinase in pancreatic cancer, we knocked down PKM2 individually as well as both PKM1 and PKM2 concurrently (PKM1/2) in cell lines derived from a Kras^G12D/-; p53^-/- pancreatic mouse model.

Methods

We used liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine metabolic profiles of wildtype and PKM1/2 knockdown PDAC cells. We further used stable isotope-labeled metabolic precursors and LC-MS/MS to determine metabolic pathways upregulated in PKM1/2 knockdown cells. We then targeted metabolic pathways upregulated in PKM1/2 knockdown cells using CRISPR/Cas9 gene editing technology.

Results

PDAC cells are able to proliferate and continue to produce pyruvate despite PKM1/2 knockdown. The serine biosynthesis pathway partially contributed to pyruvate production during PKM1/2 knockdown: knockout of phosphoglycerate dehydrogenase in this pathway decreased pyruvate production from glucose. In addition, cysteine catabolism generated ~ 20% of intracellular pyruvate in PDAC cells. Other potential sources of pyruvate include the sialic acid pathway and catabolism of glutamine, serine, tryptophan, and threonine. However, these sources did not provide significant levels of pyruvate in PKM1/2 knockdown cells.

Conclusion

PKM1/2 knockdown does not impact the proliferation of pancreatic cancer cells. The serine biosynthesis pathway supports conversion of glucose to pyruvate during pyruvate kinase knockdown. However, direct conversion of serine to pyruvate was not observed during PKM1/2 knockdown. Investigating several alternative sources of pyruvate identified cysteine catabolism for pyruvate production during PKM1/2 knockdown. Surprisingly, we find that a large percentage of intracellular pyruvate comes from cysteine. Our results highlight the ability of PDAC cells to adaptively rewire their metabolic pathways during knockdown of a key metabolic enzyme.

Primary prostate cancer educates bone stroma through exosomal pyruvate kinase M2 to promote bone metastasis

Prostate cancer (PCa) metastasizes selectively to bone through unknown mechanisms. In the current study, we identified exosome-mediated transfer of pyruvate kinase M2 (PKM2) from PCa cells into bone marrow stromal cells (BMSCs) as a novel mechanism through which primary tumor-derived exosomes promote premetastatic niche formation. We found that PKM2 up-regulates BMSC CXCL12 production in a HIF-1α-dependent fashion, which subsequently enhances PCa seeding and growth in the bone marrow. Furthermore, serum-derived exosomes from patients with either primary PCa or PCa metastasis, as opposed to healthy men, reveal that increased exosome PKM2 expression is associated with metastasis, suggesting clinical relevance of exosome PKM2 in PCa. Targeting the exosome-induced CXCL12 axis diminished exosome-mediated bone metastasis. In summary, primary PCa cells educate the bone marrow to create a premetastatic niche through primary PCa exosome-mediated transfer of PKM2 into BMSCs and subsequent up-regulation of CXCL12. This novel mechanism indicates the potential for exosome PKM2 as a biomarker and suggests therapeutic targets for PCa bone metastasis.

Prognostic Value of Lactate Dehydrogenase Expression in Different Cancers: A Meta-Analysis

BACKGROUND

This meta-analysis was performed to elucidate the association between the expression of lactate dehydrogenase (LDH) and the prognosis of various malignant neoplasms.

MATERIALS AND METHODS

Qualified studies were systematically identified from relevant databases, including PubMed, Cochrane Library, Embase, WanFang, and HowNet. A total of 17 eligible studies with 4,176 patients that complied with the inclusion criteria were enrolled in this meta-analysis. The 17 articles were published from 2011 to 2018. The hazard ratio (HR) and 95% confidence interval (95%CI) were obtained from the selected studies.

RESULTS

The analysis that included all LDH-related studies showed a significant association with the overall survival (OS) outcome (HR = 1.74, P = 0.001) but exhibited an insignificant association with the disease-free survival (DFS) or recurrence-free survival (RFS) outcome (HR = 1.40, P = 0.072). High lactate dehydrogenase A (LDHA) expression was significantly relevant to inferior OS (HR = 1.88, 95%CI: 1.37-2.59) and DFS or RFS (HR = 1.56, 95%CI: 1.29-1.89).

CONCLUSIONS

High LDH expression and the prognostic outcome of various cancer patients are significantly correlated. High LDHA expression is a promising biomarker for forecasting the survival of patients and the recurrence of different cancers in these patients. Further associative studies are required due to the complex role of LDH genes.

Targeting Pyruvate Kinase M2 and Lactate Dehydrogenase A Is an Effective Combination Strategy for the Treatment of Pancreatic Cancer

Reprogrammed glucose metabolism is one of the hallmarks of cancer, and increased expression of key glycolytic enzymes, such as pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA), has been associated with poor prognosis in various malignancies. Targeting these enzymes could attenuate aerobic glycolysis and inhibit tumor proliferation. We investigated whether the PKM2 activator, TEPP-46, and the LDHA inhibitor, FX-11, can be combined to inhibit in vitro and in vivo tumor growth in preclinical models of pancreatic cancer. We assessed PKM2 and LDHA expression, enzyme activity, and cell proliferation rate after treatment with TEPP-46, FX-11, or a combination of both. Efficacy was validated in vivo by evaluating tumor growth, PK and LDHA activity in plasma and tumors, and PKM2, LDHA, and Ki-67 expression in tumor tissues following treatment. Dual therapy synergistically inhibited pancreatic cancer cell proliferation and significantly delayed tumor growth in vivo without apparent toxicity. Treatment with TEPP-46 and FX-11 resulted in increased PK and reduced LDHA enzyme activity in plasma and tumor tissues and decreased PKM2 and LDHA expression in tumors, which was reflected by a decrease in tumor volume and proliferation. The targeting of glycolytic enzymes such as PKM2 and LDHA represents a promising therapeutic approach for the treatment of pancreatic cancer.

ARHGAP4 mediates the Warburg effect in pancreatic cancer through the mTOR and HIF-1α signaling pathways

Objective

The phenomenon that cancer cells avidly exhibit glycolysis with lactate secretion and decrease in mitochondrial activity under aerobic conditions is known historically as the Warburg effect. Rho GTPase-activating protein 4 (ARHGAP4) is an important negative regulator of the Rho signaling pathway that was associated with the tumorigenesis. Our study aims to determine the function of ARHGAP4 in controlling the glycolytic process of pancreatic cancer in vitro and possible molecular mechanism involved.

Methods

ARHGAP4 and PKM2 expressions in pancreatic cancer tissues were measured by immunohistochemistry. Human pancreatic cancer cells transfected with ARHGAP4 expressing lentivirus or siRNA were treated with either mTOR inhibitor (Rapamycin) or HIF-1α inhibitor (YC-1), and the effects were analyzed on cell viability, glucose uptake, lactate release, and the levels of ARHGAP4, p-mTOR, mTOR, PKM2, and HIF-1α expression.

Results

Our findings showed that ARHGAP4 and PKM2 expressions were, respectively, down-regulated and up-regulated in pancreatic cancer tissues. Overexpression of ARHGAP4 significantly inhibited cell viability, glucose uptake, lactate release, PKM2 expression, and activation of mTOR and HIF-1α signaling pathways in pancreatic cancer cells while ARHGAP4 silencing and treatment of Rapamycin or YC-1 showed inverse effects. Additionally, ARHGAP4 downregulation induced cell morphology of pancreatic cancer was inhibited by Rapamycin or YC-1 treatment.

Conclusion

These findings suggest that mTOR and HIF-1α signaling pathways can regulate the ARHGAP4-mediated glycolytic process of pancreatic cancer.

Lactate and cancer: a "lactatic" perspective on spinal tumor metabolism (part 1)

Spine tumors are among the most difficult tumors to treat given their proximity to the spinal cord. Despite advances in adjuvant therapies, surgery remains a critical component of treatment, both in primary tumors and metastatic disease. Given the significant morbidity of these surgeries and with other current adjuvant therapies (e.g., radiation, chemotherapy), interest has grown in other methods of targeting tumors of the spine. Recent efforts have highlighted the tumor microenvironment, and specifically lactate, as central to tumorigenesis. Once erroneously considered a waste product that indicated hypoxia/hypoperfusion, lactate is now known to be at the center of whole-body metabolism, shuttling between tissues and being used as a fuel. Diffusion-driven transporters and the near-equilibrium enzyme lactate dehydrogenase (LDH) allow rapid mobilization of large stores of muscle glycogen in the form of lactate. In times of stress, catecholamines can bind muscle cell receptors and trigger the breakdown of glycogen to lactate, which can then diffuse out into circulation and be used as a fuel where needed. Hypoxia, in contrast, is rarely the reason for an elevated arterial [lactate]. Tumors were originally described in the 1920's as being "glucose-avid" and "lactate-producing" even in normoxia (the "Warburg effect"). We now know that a broad range of metabolic behaviors likely exist, including cancer cells that consume lactate as a fuel, others that may produce it, and still others that may change their behavior based on the local microenvironment. In this review we will examine the relationship between lactate and tumor metabolism with a brief look at spine-specific tumors. Lactate is a valuable fuel and potent signaling molecule that has now been implicated in multiple steps in tumorigenesis [e.g., driving vascular endothelial growth factor (VEGF) expression in normoxia]. Future work should utilize translational animal models to target tumors by altering the local tumor microenvironment, of which lactate is a critical part.

Unappreciated Role of LDHA and LDHB to Control Apoptosis and Autophagy in Tumor Cells

Tumor cells possess a high metabolic plasticity, which drives them to switch on the anaerobic glycolysis and lactate production when challenged by hypoxia. Among the enzymes mediating this plasticity through bidirectional conversion of pyruvate and lactate, the lactate dehydrogenase A (LDHA) and lactate dehydrogenase B (LDHB), are indicated. LDHA has a higher affinity for pyruvate, preferentially converting pyruvate to lactate, and NADH to NAD⁺ in anaerobic conditions, whereas LDHB possess a higher affinity for lactate, preferentially converting lactate to pyruvate, and NAD⁺ to NADH, when oxygen is abundant. Apart from the undisputed role of LDHA and LDHB in tumor cell metabolism and adaptation to unfavorable environmental or cellular conditions, these enzymes participate in the regulation of cell death. This review presents the latest progress made in this area on the roles of LDHA and LDHB in apoptosis and autophagy of tumor cells. Several examples of how LDHA and LDHB impact on these processes, as well as possible molecular mechanisms, will be discussed in this article. The information included in this review points to the legitimacy of modulating LDHA and/or LDHB to target tumor cells in the context of human and veterinary medicine.

Prognostic role of glycolysis for cancer outcome: evidence from 86 studies

OBJECTIVE

The abnormal expression of the key enzymes in glycolytic pathways, including glucose transporter-1, glucose transporter-3, hexokinase-II, lactate dehydrogenase 5, pyruvate kinase M2, glucose-6-phosphate dehydrogenase, transketolase-like protein 1 and pyruvate dehydrogenase kinase-1 was reported to be associated with poor prognosis of various cancers. However, the association remains controversial. The objective of this study was to investigate the prognostic significance of glycolysis-related proteins.

MATERIALS AND METHODS

We searched MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, using Pubmed and Ovid as search engines and Google Scholar from inception to April 2017. Eighty-six studies with 12,002 patients were included in the study.

RESULTS

Our pooled results identified that glycolysis-related proteins in cancers were associated with shorter overall survival of colorectal cancer (HR 2.33, 95% CI 1.38-3.93, P = 0.002), gastric cancer (HR 1.55, 95% CI 1.31-1.82, P < 0.001), cancer of gallbladder or bile duct (HR 2.16, 95% CI 1.70-2.75, P < 0.001), oral cancer (HR 2.07, 95% CI 1.32-3.25, P < 0.001), esophageal cancer (HR 1.66, 95% CI 1.25-2.21, P = 0.01), hepatocellular carcinoma (HR 2.04, 95% CI 1.64-2.54, P < 0.001), pancreatic cancer (HR 1.72, 95% CI 1.39-2.13, P < 0.001), breast cancer(HR 1.67, 95% CI 1.34-2.08, P < 0.001), and nasopharyngeal carcinoma (HR 3.59, 95% CI 1.75-7.36, P < 0.001). No association was found for lung cancer, ovarian cancer or melanoma. The key glycolytic transcriptional regulators (HIF-1α, p53) were analyzed in parallel to the glycolysis-related proteins, and the pooled results identified that high-level expression of HIF-1α was significantly associated with shorter overall survival (HR 0.57, 95% CI 0.42-0.79, P < 0.001) Furthermore, glycolysis-related proteins linked with poor differentiated tumors (OR 1.81, 95% CI 1.46-2.25, P < 0.001), positive lymph node metastasis (OR 2.73, 95% CI 2.16-3.46, P < 0.001), positive vascular invasion (OR 2.05, 95% CI 1.37-3.07, P < 0.001), large tumor size (OR 2.06, 95% CI 1.80-2.37, P < 0.001), advanced tumor stage (OR 1.58, 95% CI 1.19-2.09, P < 0.001), and deeper invasion (OR 2.37, 95% CI 1.93-2.91, P < 0.001).

CONCLUSION

Glycolytic transcriptional regulators and glycolysis-related proteins in cancers were significantly associated with poor prognosis, suggesting glycolytic status may be potentially valuable prognostic biomarkers for various cancers.

Expression of LDH and CEA in serum in the process of targeted therapy of lung adenocarcinoma and the association between them and prognosis

Expression of lactate dehydrogenase (LDH) and carcinoembryonic antigen (CEA) in serum was investigated in the process of epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) targeting for treating lung adenocarcinoma and the association between LDH, CEA and prognosis of patients was evaluated. A retrospective analysis of 89 patients with lung adenocarcinoma admitted to The First People's Hospital of Chuzhou from January 2014 to February 2015 was performed. Fifty-one patients who received resection were considered the operation group, while the other 38 patients received EGFR-TKI targeted therapy and were considered the targeted group. Electrochemiluminescence and automatic biochemical analyzer were respectively used to detect the expression of CEA and LDH in serum. The therapeutic effective rates and the expression levels of LDH and CEA of the patients were compared. The patients in the targeted group were divided into LDH high-expression group, LDH low-expression group, CEA high-expression group and CEA low-expression group according to the median of the expression levels of LDH and CEA. The therapeutic effective rate in LDH high-expression group (65.00%) was significantly lower than that in LDH low-expression group (100.00%) (P=0.004). The therapeutic effective rate in CEA high-expression group (64.71%) was significantly lower than that in CEA low-expression group (95.24%) (P=0.016). The 3-year overall mortality rate in LDH high-expression group (47.37%) was significantly higher than that in LDH low-expression group (11.11%) (P=0.034). The 3-year overall mortality rate in CEA high-expression group (56.25%) was significantly higher than that in CEA low-expression group (4.76%) (P=0.020). The levels of CEA and LDH in serum were abnormally expressed in the process of the treatment of lung adenocarcinoma targeted by EGFR-TKI, which had great significance for monitoring the efficacy and prognosis of the treatment of lung adenocarcinoma targeted by EGFR-TKI.