PKM2: the thread linking energy metabolism reprogramming with epigenetics in cancer

GLUT-1/PKM2 loop dysregulation in patients with non-ST-segment elevation myocardial infarction promotes metainflammation

AIMS

The functional capacity of the immune cells is strongly dependent on their metabolic state and inflammatory responses are characterized by a greater use of glucose in immune cells. This study is aimed to establish the role of glucose metabolism and its players [glucose transporter 1 (GLUT-1) and pyruvate kinase isozyme M2 (PKM2)] in the dysregulation of adaptive immunity and inflammation observed in patients with non-ST-segment elevation myocardial infarction (NSTEMI).

METHODS AND RESULTS

We enrolled 248 patients allocated to three groups: NSTEMI patients, chronic coronary syndromes (CCS) patients, healthy subjects (HSs). NSTEMI patients showed higher expression of GLUT-1 and an enhanced glucose uptake in T cells when compared with CCS patients (P < 0.0001; P = 0.0101, respectively) and HSs (P = 0.0071; P = 0.0122, respectively). PKM2 had a prevalent nuclear localization in T lymphocytes in NSTEMI (P = 0.0005 for nuclear vs. cytoplasm localization), while in CCS and HS, it was equally distributed in both compartments. In addition, the nuclear fraction of PKM2 was significantly higher in NSTEMI compared with HS (P = 0.0023). In NSTEMI patients, treatment with Shikonin and Fasentin, which inhibits PKM2 enzyme activity and GLUT-1-mediated glucose internalization, respectively, led to a significant reduction in GLUT-1 expression along with the down-regulation of pro-inflammatory cytokine expression.

CONCLUSION

NSTEMI patients exhibit dysregulation of the GLUT-1/PKM2 metabolic loop characterized by nuclear translocation of PKM2, where it acts as a transcription regulator of pro-inflammatory genes. This detrimental loop might represent a new therapeutic target for personalized medicine.

Adrenomedullin induces cisplatin chemoresistance in ovarian cancer through reprogramming of glucose metabolism

Background and Objectives

The metabolic network of cancer cells has been reprogrammed - relying more on aerobic glycolysis to gain energy, which is an important reason for drug resistance. Expression of adrenomedullin (ADM) in ovarian cancer tissues is related to resistance to platinum-based drugs. In view of this, we intended to investigate the correlation between ADM and glucose metabolism reprogramming of tumor cells to clarify the possible mechanism of ADM-induced ovarian cancer cisplatin resistance through glucose metabolism reprogramming.

Methods

Epithelial ovarian cancer (EOC) cell viability and apoptosis were determined. Different gene expression and protein levels were detected by real-time revere transcription polymerase chain reaction and western blotting. Oxygen consumption rate (OCR) and extracellular acidification rates (ECARs) were measured.

Results

ADM expression was upregulated in cisplatin-resistant EOC cells. ADM attenuated cisplatin-inhibited cell survival and cisplatin-induced apoptosis in sensitive EOC cells; knockdown of ADM enhanced cisplatin chemosensitivity of cisplatin-resistant EOC cells. ADM enhanced glycolysis in cisplatin-sensitive EOC cells; knockdown of ADM significantly inhibited glycolysis in cisplatin-resistant EOC cells. ADM significantly upregulated pyruvate kinase isozyme type M2 (PKM2) protein level, the key enzyme during glycolysis; PKM2 inhibitor significantly abolished the ADM-improved cell survival and ADM-inhibited apoptosis.

Conclusion

ADM promoted proliferation and inhibited apoptosis of ovarian cancer cells through reprogramming of glucose metabolism, so as to promote cisplatin resistance. The study is expected to identify multidrug resistance markers of ovarian cancer and provide a target for the prevention and treatment of ovarian cancer, which is important for clinical translational research.

Knowledge-driven design and optimization of potent symmetric anticancer molecules: A case study on PKM2 activators

BACKGROUND

Pyruvate kinase M2 (PKM2) is preferentially expressed as a low-activity dimer over the active tetramer in proliferating tumor cells, resulting in metabolic reprogramming to achieve high energy requirements and nutrient uptake. This leads to a shift from the normal glycolytic pathway causing tumor cells to proliferate uncontrollably. This study utilizes knowledge-based drug discovery to determine the critical features from experimentally known PKM2 activators and design compounds that would significantly confer a stable structural and functional edge over the known compounds which are still at the preclinical stage.

METHODS

Conscientious molecular modeling studies were carried out and critical structural features were identified and validated from the knowledge of experimentally known PKM2 activators to confer high-binding affinities. A virtual library of 200 palindromic and non-palindromic activators was designed based on these identified critical features to target a distinct activator binding-site. This binding would favor specific dimer-dimer association and subsequent protein tetramerization. The resultant compounds strongly correlated with identified structural features and binding affinities which further strengthened our findings. The designed activators were then subjected to pharmacokinetic profiling and toxicity prediction, followed by free-binding energy calculations and MD simulations.

RESULTS

All the virtually designed activators comprising the identified critical features were observed to confer high-binding affinities ranging from -9.1 to -15.0 kcal/mol to the receptor protein. The designed activators also demonstrated optimum pharmacokinetic and toxicity profiles.

CONCLUSION

The best activators selected for MD simulations studies were conclusively observed to stabilize the required tetrameric conformation suggesting that these activators could potentially target PKM2 tetramerization that might restore the normal glycolytic pathway and suppress tumor progression.

Pyruvate kinase M2 (PKM2) interacts with activating transcription factor 2 (ATF2) to bridge glycolysis and pyroptosis in microglia

Pyruvate kinase M2 (PKM2), a glycolytic rate-limiting enzyme, reportedly plays an important role in tumorigenesis and the inflammatory response by regulating the metabolic reprogramming. However, its contribution to microglial activation during neuroinflammation is still unknown. In this study, we observed an enhanced glycolysis level in the lipopolysaccharide (LPS)-activated microglia. Utilizing the glycolysis inhibitor 2-DG, we proved that LPS requires glycolysis to induce microglial pyroptosis. Moreover, the protein expression, dimer/monomer formation, phosphorylation and nuclear translocation of PKM2 were all increased by LPS. Silencing PKM2 or preventing its nuclear translocation by TEPP-46 significantly alleviated the LPS-induced inflammatory response and pyroptosis in microglia. Employing biological mass spectrometry combined with immunoprecipitation technology, we identified for the first time that PKM2 interacts with activating transcription factor 2 (ATF2) in microglia. Inhibition of glycolysis or preventing PKM2 nuclear aggregation significantly reduced the phosphorylation and activation of ATF2. Furthermore, knocking down ATF2 reduced the LPS-induced pyroptosis of microglia. In vivo, we showed the LPS-induced pyroptosis in the cerebral cortex tissues of mice, and first found that an increased PKM2 expression was co-localized with ATF2 in the inflamed mice brain. Collectively, our data suggested for the first time that PKM2, a key rate-limiting enzyme of the Warburg effect, directly interacts with the pro-inflammatory transcription factor ATF2 to bridge glycolysis and pyroptosis in microglia, which might be a pivotal crosstalk between metabolic reprogramming and neuroinflammation in the CNS.

Proline dehydrogenase in cancer: apoptosis, autophagy, nutrient dependency and cancer therapy

L-proline catabolism is emerging as a key pathway that is critical to cellular metabolism, growth, survival, and death. Proline dehydrogenase (PRODH) enzyme, which catalyzes the first step of proline catabolism, has diverse functional roles in regulating many pathophysiological processes, including apoptosis, autophagy, cell senescence, and cancer metastasis. Notably, accumulated evidence demonstrated that PRODH plays complex role in many types of cancers. In this review, we briefly introduce the function of PRODH, then its expression in different types of cancer. We next discuss the regulation of PRODH in cancer, the downstream pathways of PRODH and the therapies that are under investigation. Finally, we propose novel insights for future perspectives on the modulation of PRODH.

Aberrant RNA Splicing Events Driven by Mutations of RNA-Binding Proteins as Indicators for Skin Cutaneous Melanoma Prognosis

The worldwide incidence of skin cutaneous melanoma (SKCM) is increasing at a more rapid rate than other tumors. Aberrant alternative splicing (AS) is found to be common in cancer; however, how this process contributes to cancer prognosis still remains largely unknown. Mutations in RNA-binding proteins (RBPs) may trigger great changes in the splicing process. In this study, we comprehensively analyzed DNA and RNA sequencing data and clinical information of SKCM patients, together with widespread changes in splicing patterns induced by RBP mutations. We screened mRNA expression-related and prognosis-related mutations in RBPs and investigated the potential affections of RBP mutations on splicing patterns. Mutations in 853 RBPs were demonstrated to be correlated with splicing aberrations (p < 0.01). Functional enrichment analysis revealed that these alternative splicing events (ASEs) may participate in tumor progress by regulating the modification process, cell-cycle checkpoint, metabolic pathways, MAPK signaling, PI3K-Akt signaling, and other important pathways in cancer. We also constructed a prediction model based on overall survival-related AS events (OS-ASEs) affected by RBP mutations, which exhibited a good predict efficiency with the area under the curve of 0.989. Our work highlights the importance of RBP mutations in splicing alterations and provides effective biomarkers for prediction of prognosis of SKCM.

Macrophages in metabolic associated fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named non-alcoholic fatty liver disease is the most common liver disorder in many countries. The inflammatory subtype termed steatohepatitis is a driver of disease progression to cirrhosis, hepatocellular carcinoma, liver transplantation, and death, but also to extrahepatic complications including cardiovascular disease, diabetes and chronic kidney disease. The plasticity of macrophages in response to various environmental cues and the fact that they can orchestrate cross talk between different cellular players during disease development and progression render them an ideal target for drug development. This report reviews recent advances in our understanding of macrophage biology during the entire spectrum of MAFLD including steatosis, inflammation, fibrosis, and hepatocellular carcinoma, as well as for the extra-hepatic manifestations of MAFLD. We discuss the underlying molecular mechanisms of macrophage activation and polarization as well as cross talk with other cell types such as hepatocytes, hepatic stellate cells, and adipose tissue. We conclude with a discussion on the potential translational implications and challenges for macrophage based therapeutics for MAFLD.

Sirtuin 6 and metabolic genes interplay in Warburg effect in cancers

Under oxygen availability, normal cells undergo mitochondrial oxidative phosphorylation to metabolize glucose and yield up to 36 ATPs per glucose molecule for cellular functions, and undergo non-oxidative metabolism (glycolysis) under hypoxic and proliferating conditions to yield 2 ATP per glucose. These cells metabolize glucose to pyruvate via glycolysis followed by conversion of pyruvate to lactate via lactate dehydrogenase. However, cancer cells have the ability to undergo glycolysis and ferment glucose to lactate regardless of oxygen availability; a phenomenon first addressed by Otto Warburg and called, "Warburg effect". Numerous glycolytic genes/proteins have been identified in tumors; that include glucose transporter 1 (GLUT1), hexokinase 2 (HK2), pyruvate kinase-M2 splice isoform (PKM2), and lactate dehydrogenase (LDH-A). Histone deacetylase sirtuin 6 (SIRT6), an epigenetic regulator, is highly expressed in various cancers. SIRT6 plays an important role in Warburg effect by regulating many glycolytic genes. Loss of SIRT6 enhances tumor growth via enhancing glycolysis. This review is mainly concerned with exploring the most recent advances in understanding the roles of the metabolic genes (GLUT1, HK2, PKM2, and LDH-A) and the epigenetic regulator SIRT6 in cancer metabolism and how SIRT6 can modulate these metabolic genes expression and its possible use as a therapeutic target for cancer treatment.

Impact of Sirtuin Enzymes on the Altered Metabolic Phenotype of Malignantly Transformed Cells

Sirtuins compose a unique collection of histone deacetylase enzymes that have a wide variety of enzymatic activities and regulate diverse cell functions such as cellular metabolism, longevity and energy homeostasis, mitochondrial function, and biogenesis. Impaired sirtuin functions or alterations of their expression levels may result in several pathological conditions and contribute to the altered metabolic phenotype of malignantly transformed cells in a significant manner. In the twenty-first century, principles of personalized anticancer treatment need to involve not only the evaluation of changes of the genetic material, but also the mapping of epigenetic and metabolic alterations, to both of which the contribution of sirtuin enzymes is fundamental. Since sirtuins are central players in the maintenance of cellular energy and metabolic homeostasis, they are key elements in the development of metabolic transformation of cancer cells referred to as the Warburg effect. Although its most well-known features are enhanced glycolysis and excessive lactate production, Warburg effect has several aspects involving both carbohydrate, lipid, and amino acid metabolism, among which different tumor types have different preferences. Therefore, energy supply of cancer cells can be impaired by a growing number of antimetabolite agents, for which appropriate vectors are strongly needed. However, data are controversial about their tumor suppressor or oncogenic properties, the biological effects of sirtuin enzymes strongly depend on the tissue microenvironment (TME) in which they are expressed. Immune cells are regarded as key players of TME. Sirtuins regulate the survival, activation, metabolism, and mitochondrial function of these cells, therefore, they are not only single elements, but key regulators of the network that determines anticancer immunity. Altered metabolism of tumor cells induces changes in the gene expression pattern of cells in TME, due to altered concentrations of metabolite cofactors of epigenetic modifiers including sirtuins. In summary, epigenetic and metabolic alterations in malignant diseases are influenced by sirtuins in a significant manner, and should be treated in a personalized approach. Since they often develop in early stages of cancer, broad examination of these alterations is required at time of the diagnosis in order to provide a personalized combination of distinct therapeutic agents.

Obesity-Altered Adipose Stem Cells Promote ER⁺ Breast Cancer Metastasis through Estrogen Independent Pathways

Adipose stem cells (ASCs) play an essential role in tumor microenvironments. These cells are altered by obesity (obASCs) and previous studies have shown that obASCs secrete higher levels of leptin. Increased leptin, which upregulates estrogen receptor alpha (ERα) and aromatase, enhances estrogen bioavailability and signaling in estrogen receptor positive (ER⁺) breast cancer (BC) tumor growth and metastasis. In this study, we evaluate the effect of obASCs on ER⁺BC outside of the ERα signaling axis using breast cancer models with constitutively active ERα resulting from clinically relevant mutations (Y537S and D538G). We found that while obASCs promote tumor growth and proliferation, it occurs mostly through abrogated estrogen signaling when BC has constitutive ER activity. However, obASCs have a similar promotion of metastasis irrespective of ER status, demonstrating that obASC promotion of metastasis may not be completely estrogen dependent. We found that obASCs upregulate two genes in both ER wild type (WT) and ER mutant (MUT) BC: SERPINE1 and ABCB1. This study demonstrates that obASCs promote metastasis in ER WT and MUT xenografts and an ER MUT patient derived xenograft (PDX) model. However, obASCs promote tumor growth only in ER WT xenografts.

Nuclear EGFR-PKM2 axis induces cancer stem cell-like characteristics in irradiation-resistant cells

Radiation therapy has become an important tool in the treatment of cancer patients, but most patients relapse within 5 years. Relapse is due to the presence of cancer stem cells (CSCs), but the molecular mechanism of radioresistance in CSCs remains largely elusive. Here, we found that irradiation-resistant (IR) cells exhibited increased stem cell-like properties together with elevated anchorage-independent growth and metastasis ability. EGFR not only leads to increased acquisition of endometrial cancer stem cell markers in radioresistant sublines but is critical for the cancer stem-cell phenotype and tumorigenicity. Moreover, PKM2 functions as an interacting partner of EGFR, which induces the EMT phenotype and stem cell-like properties in IR cells. Finally, we found that the regulatory function of the EGFR-PKM2 axis is dependent on nuclear EGFR. In sum, our study indicated that EGFR and PKM2 directly interact and bind with each other to regulate the transcription of stemness-related genes and promote the stem-like phenotype, thus promoting invasion and metastasis.

LY294002 inhibits the Warburg effect in gastric cancer cells by downregulating pyruvate kinase M2

The ‘Warburg effect’ is considered a vital hallmark of cancer cells, characterized by an altered metabolism, in which cells rely on aerobic glycolysis. As a key enzyme of aerobic glycolysis, pyruvate kinase M2 (PKM2) serves a crucial role in tumorigenesis. Accumulating studies have indicated that PKM2 is a potential target for cancer therapy. The aim of the present study was to assess the anticancer effects of LY294002, a specific phosphatidylinositol-3-kinase inhibitor, on gastric cancer (GC) cells and further explore its possible mechanism in vitro. The present study revealed that LY294002 inhibited GC cell proliferation, induced early apoptosis and significantly decreased lactate dehydrogenase activity and lactate production, in part through inhibiting PKM2 expression. In summary, LY294002 exhibits anticancer effects on GC, partly via the downregulation of PKM2.

Tumor pyruvate kinase M2: A promising molecular target of gastrointestinal cancer

Gastrointestinal (GI) cancer is one of the most common causes of cancer-related deaths worldwide. Tumor markers are valuable in detecting post-surgical recurrence or in monitoring response to chemotherapy. Pyruvate kinase isoform M2 (PKM2), a glycolytic enzyme catalyzing conversion of phosphoenolpyruvate (PEP) to pyruvate, confers a growth advantage to the tumor cells and enables them to adapt to the tumor microenvironment. In this review, we have summarized current research on the expression and regulation of PKM2 in tumor cells, and its potential role in GI carcinogenesis and progression. Furthermore, we have also discussed the potential of PKM2 as a diagnostic and screening marker, and a therapeutic target in GI cancer.

Nuclear localization of metabolic enzymes in immunity and metastasis

Metabolism is essential to all living organisms that provide cells with energy, regulators, building blocks, enzyme cofactors and signaling molecules, and is in tune with nutritional conditions and the function of cells to make the appropriate developmental decisions or maintain homeostasis. As a fundamental biological process, metabolism state affects the production of multiple metabolites and the activation of various enzymes that participate in regulating gene expression, cell apoptosis, cancer progression and immunoreactions. Previous studies generally focus on the function played by the metabolic enzymes in the cytoplasm and mitochondrion. In this review, we conclude the role of them in the nucleus and their implications for cancer progression, immunity and metastasis.

Pyruvate kinase M2 deregulation enhances the metastatic potential of tongue squamous cell carcinoma

Pyruvate kinase M2 (PKM2) has been verified to correlate with the prognosis of many types of cancer. However, its role in the development and metastasis of tongue squamous cell carcinoma (TSCC) remains unclear. The immunohistochemistry (IHC) results confirmed that PKM2 is overexpressed in patients with TSCC. PKM2 up-regulation was related to lymph node metastasis and associated with reduced overall survival. According to the microarray analysis and Western blots, PKM2 expression was up-regulated in TSCC cells with enhanced metastatic potential. PKM2 knockdown inhibited cell migration and invasion, reduced SOD2 (manganese superoxide dismutase) activity and the intracellular H₂O₂ level, and inhibited tumour growth and lung metastasis in vivo. PKM2 overexpression promoted cell migration and invasion, and increased SOD2 activity and the intracellular H₂O₂ level. Moreover, miR-138 directly targeted PKM2 and inhibited PKM2 expression. Thus, PKM2 deregulation plays an important role in TSCC and may serve as a biomarker of metastatic potential or as a therapeutic target in patients with TSCC. PKM2, a miR-138 target gene, enhances the metastatic potential of TSCC through the SOD2-H₂O₂ pathway.

Interplay between cancer cell cycle and metabolism: Challenges, targets and therapeutic opportunities

A growing interest has emerged in the field of studying the cross-talk between cancer cell cycle and metabolism. In this review, we aimed to present how metabolism and cell cycle are correlated and how cancer cells get energy to drive cell cycle. Cell proliferation and cell death largely depend on the metabolic activity of the cell. Cell cycle proteins, e.g. cyclin D, cyclin dependent kinase (CDK), some pro-apoptotic and anti-apoptotic proteins, and P53 have been shown to be regulated by metabolic crosstalk. Dysregulation of this cross-talk between metabolism and cell cycle leads to degenerative disorder(s) and cancer. It is not fully understood the actual reason of aberration between metabolism and cell cycle, but it is a hallmark of cancer research. Herein, we discussed the role of some regulatory molecules relative of cell cycle and metabolism and highlight how they control the function of each other. We also pointed out, current therapeutic opportunities and some additional crucial therapeutic targets on these fields that could be a breakthrough in cancer research.

Expression Levels of Warburg-Effect Related microRNAs Correlate with each Other and that of Histone Deacetylase Enzymes in Adult Hematological Malignancies with Emphasis on Acute Myeloid Leukemia

Disruption of epigenetic regulation and characteristic metabolic alterations (known as the Warburg-effect) are well-known hallmarks of cancer. In our study we investigated the expression levels of microRNAs and histone deacetylase enzymes via RT-qPCR in bone marrow specimens of adult patients suffering from hematological malignancies (total cohort n = 40), especially acute myeloid leukemia (n = 27). The levels of the three examined Warburg-effect related microRNAs (miR-378*, miR-23b, miR-26a) positively correlated with each other and the oncogenic miR-155 and miR-125b, while negatively with the level of the tumorsuppressor miR-124. Significant relationships have been confirmed between the levels of SIRT6, HDAC4 and the microRNAs listed above. In NPM1-mutated AML (n = 6), the level of miR-125b was significantly lower than in the group of AML patients not carrying this mutation (n = 13) (p < 0.05). In M5 FAB type of AML (n = 5), the level of miR-124 was significantly higher compared to the M2 group (n = 7) (p < 0.05). In two cases of FAB M5 AML, the levels of SIRT6 and miR-26a increased during the first 4 weeks of treatment. In the total cohort, white blood cell count at the time of the diagnosis significantly correlated with the levels of HDAC4, SIRT6, miR-124 and miR-26a. Our results suggest that Warburg-effect related microRNAs may have important role in the pathogenesis of leukemia, and the potential oncogenic property of HDAC4 and SIRT6 cannot be excluded in hematological malignancies. Elevated level of miR-125b can contribute to adverse prognosis of AML without NPM1 mutation. The prevailment of the tumorsuppressor property of miR-124 may depend on the accompanying genetic alterations.

Role of epigenetics in modulation of immune response at the junction of host-pathogen interaction and danger molecule signaling

Epigenetic mechanisms have rapidly and controversially emerged as silent modulators of host defenses that can lead to a more prominent immune response and shape the course of inflammation in the host. Thus, the epigenetics can both drive the production of specific inflammatory mediators and control the magnitude of the host response. The epigenetic actions that are predominantly shown to modulate the host defense against microbial pathogens are DNA methylation, histone modification and the activity of non-coding RNAs. There is also growing evidence that opportunistic chronic pathogens, such as Porphyromonas gingivalis, as a microbial host subversion strategy, can epigenetically interfere with the host DNA machinery for successful colonization. Similarly, the novel involvement of small molecule 'danger signals', which are released by stressed or infected cells, at the center of host-pathogen interplay and epigenetics is developing. In this review, we systematically examine the latest knowledge within the field of epigenetics in the context of host-derived danger molecule and purinergic signaling, with a particular focus on host microbial defenses and infection-driven chronic inflammation.

MiR-338-3p targets pyruvate kinase M2 and affects cell proliferation and metabolism of ovarian cancer

MiR-338-3p is down-regulated in cancer, which inhibits cancer cell proliferation, metastasis, and increases chemosensitivity, but its functions in ovarian cancer remains unknown. The present study aims to identify the miR-338-3p targeted genes and to investigate the associated regulatory mechanisms in ovarian cancer cell proliferation and metabolism. Our results demonstrated miR-338-3p expression was down-regulated in most of ovarian cancer tissues and cell lines. Restoration of miR-338-3p expression in ovarian cancer cells could inhibit cell proliferation, lactate production and lactate production of ovarian cancer cells. PKM2 was verified as a target gene of miR-338-3p by luciferase assay. Further study indicated miR-338-3p controlled ovarian cancer cell metabolism by inhibiting PKM2 expression. It is summarized that the regulatory role of miR-338-3p on PKM2 expression in ovarian cancer may play important roles in cell metabolism.

PKM2 Promotes Cell Survival and Invasion Under Metabolic Stress by Enhancing Warburg Effect in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Pyruvate kinase isoenzyme M2 (PKM2) is an essential enzyme involved in the regulation of aerobic glycolysis in cancer cells and promotes the translation between glycolytic flux and biosynthesis of cellular building blocks.

AIM

Our present study aims to explore the expression pattern and underlying cellular functions of PKM2 in pancreatic ductal adenocarcinoma (PDAC) under metabolic stress.

METHODS

Oncomine database and a tissue microarray (n = 90) were used to investigate the expression pattern of PKM2 and its clinicopathological findings. In vitro proliferation, apoptosis and invasion assays were used to determine the role and related mechanism of PKM2 in PDAC.

RESULTS

Data from Oncomine database and our tissue microarray show that PKM2 is significantly elevated in PDAC specimens compared with the corresponding normal tissues. Kaplan-Meier survival analysis shows that higher expression of PKM2 is closely correlated with a poor prognosis of patients with PDAC. Under metabolic stress, suppression of PKM2 expression in PANC-1 and AsPC-1 cells results in decreased cell survival, increased caspase-3/7 activity, and reduced invasive potential, and these effects can be reversed by reintroduction of PKM2. Furthermore, sh-PKM2 cells show a significant decreased Warburg effect compared with sh-Ctrl cells as demonstrated by reduced glucose consumption and lactate production. Treatment with 2-deoxy-D-glucose, a glycolysis inhibitor, completely blocks the influences of PKM2 on cell survival and invasion.

CONCLUSIONS

Our study reveals that silencing of PKM2 exhibits a tumor-suppressive role through altered Warburg effect and suggests that targeting PKM2 might serve as a potential therapeutic target for PDAC.

Identification of Arsenic Direct-Binding Proteins in Acute Promyelocytic Leukaemia Cells

The identification of arsenic direct-binding proteins is essential for determining the mechanism by which arsenic trioxide achieves its chemotherapeutic effects. At least two cysteines close together in the amino acid sequence are crucial to the binding of arsenic and essential to the identification of arsenic-binding proteins. In the present study, arsenic binding proteins were pulled down with streptavidin and identified using a liquid chromatograph-mass spectrometer (LC-MS/MS). More than 40 arsenic-binding proteins were separated, and redox-related proteins, glutathione S-transferase P1 (GSTP1), heat shock 70 kDa protein 9 (HSPA9) and pyruvate kinase M2 (PKM2), were further studied using binding assays in vitro. Notably, PKM2 has a high affinity for arsenic. In contrast to PKM2, GSTP1and HSPA9 did not combine with arsenic directly in vitro. These observations suggest that arsenic-mediated acute promyelocytic leukaemia (APL) suppressive effects involve PKM2. In summary, we identified several arsenic binding proteins in APL cells and investigated the therapeutic mechanisms of arsenic trioxide for APL. Further investigation into specific signal pathways by which PKM2 mediates APL developments may lead to a better understanding of arsenic effects on APL.

Up-Regulation of PKM2 Relates to Retinal Ganglion Cell Apoptosis After Light-Induced Retinal Damage in Adult Rats

Pyruvate kinase isozyme type M2 (PKM2), a key glycolytic enzyme, which is involved in ATP generation and pyruvate production, participates in tumor metabolism, growth, and other multiple cellular processes. However, one attractive biological function of PKM2 is that it translocates to the nucleus and induces cell apoptosis. Recently, increased PKM2 has been found in age-related macular degeneration (AMD), but little is known regarding its function in the AMD pathophysiology. To investigate whether PKM2 participated in retinal degeneration, we performed a light-induced retinal damage model in adult rats. Western blot and immunohistochemistry analysis showed a significant up-regulation of PKM2 in retinal ganglion cells (RGCs) layer (GCL) after light exposure. Immunofluorescent labeling indicated that PKM2 located mainly in RGCs. Co-localization of PKM2 and active caspase-3 as well as TUNEL in RGCs suggested that PKM2 might participate in RGC apoptosis. In addition, the expression patterns of cyclin D1 and phosphorylated extracellular signal-regulated kinase (p-ERK) were parallel with that of PKM2. Furthermore, PKM2, cyclin D1, and active caspase-3 protein expression decreased by intravitreal injection of U0126, a highly selective inhibitor of MAPK/ERK kinase. Collectively, we hypothesized that PKM2 might participate in RGC apoptosis after light-induced retinal damage medicated by p-ERK through cycle re-entry mechanism.

Deregulation of histone-modifying enzymes and chromatin structure modifiers contributes to glioma development

The epigenetic landscape is deregulated in cancer due to aberrant activation or inactivation of enzymes maintaining and modifying the epigenome. Histone modifications and global aberrations at the histone level may result in distorted patterns of gene expression, and malfunction of proteins that regulate chromatin modification and remodeling. Recent whole genome studies demonstrated that histones and chaperone proteins harbor mutations that may result in gross alterations of the epigenome leading to genome instability. Glioma development is a multistep process, involving genetic and epigenetic alterations. This review summarizes newly identified mechanisms affecting expression/functions of histone-modifying enzymes and chromatin modifiers in gliomas. We discuss recent approaches to overcome epigenetic alterations with histone-modifying enzyme inhibitors and their prospects for glioma therapy.

Overexpression of metabolic markers HK1 and PKM2 contributes to lymphatic metastasis and adverse prognosis in Chinese gastric cancer

Hexokinase 1 (HK1) and pyruvate kinase M2 (PKM2) are two key regulators in glycosis and oncogenic markers in cancers. In the present study, we investigated the expression profile by Western blotting and immunohistochemistry and determined their prognostic values in the gastric cancer. Expression of HK1 and PKM2 was remarkably increased in gastric cancer tissues and was significantly associated lymphatic metastasis and advanced TNM staging. In the COX regression model, HK1 and TNM stage were analyzed as adverse prognostic indicators in gastric cancer. Furthermore, patients with HK1 expression showed remarkable shorter survival duration in both lymphatic metastasis cohort and advanced staging cohort. Our results suggest that overexpression of PKM2 and HK1, especially the latter, significantly associates with lymphatic metastasis, advanced clinical staging and unfavorable prognosis in gastric cancer.

Both high expression of pyruvate kinase M2 and vascular endothelial growth factor-C predicts poorer prognosis in human breast cancer

Pyruvate kinase M2 (PKM2) and vascular endothelial growth factor-C (VEGF-C) have been known to play an important role in tumorigenesis and tumor progression in breast cancer. However, the association between PKM2 and VEGF-C in breast cancer remains unclear. In the present study, a total of 218 specimens from breast cancer patients and 26 paired breast tumors with adjacent normal tissues as well as two breast cancer cell lines were enrolled to investigate the correlation between PKM2 and VEGF-C. We found that PKM2 and VEGF-C mRNA levels were both significantly increasing in breast tumors compared with adjacent normal tissues. Knockdown of PKM2 mRNA expression resulted in VEGF-C mRNA and protein down-regulated as well as cell proliferation inhibited. A positive correlation between PKM2 and VEGF-C expression was identified by immunohistochemical analyses of 218 specimens of patients with breast cancer (P=0.023). PKM2 high expression was significantly correlated with histological grade (P=0.030), lymph node stage (P=0.001), besides VEGF-C high expression was significantly associated with lymphovascular invasion (P=0.012). While combined high expression of PKM2 and VEGF-C was found to be associated with worse histological grade, more lymph node metastasis, more lymphovascular invasion, shorter progression free survival (PFS), and poorer overall survival (OS) in human breast cancer. The results of the present study suggested that PKM2 expression was correlated with VEGF-C expression, and combination of PKM2 and VEGF-C levels had the better prognostic significance in predicting the poor outcome of patients with breast cancer.

JMJD5 is a potential oncogene for colon carcinogenesis

OBJECTIVE

To observe the effects of Jumonji C domain-containing (JMJD) 5 depletion on colon cancer (CC).

METHODS

A short-hairpin RNA targeting JMJD5 was transfected into a lentivirus to make Lv-shJMJD5 for infection into the Caco-2 human cell. Besides, a negative control shRNA was constructed. The mRNA and protein levels of JMJD5 were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting, respectively. Cell proliferation, migration, and invasion were assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), soft agar colony assay and transwell assay, respectively. In addition, immunohistochemical (IHC) staining was performed to investigate the expression of JMJD5 in adjacent normal tissues and tumor tissues from patients with CC.

RESULTS

Compared with control group, mRNA and protein levels of JMJD5 was significantly reduced after infection with Lv-shJMJD5 (P<0.05), and Caco-2 cell proliferation, migration, and invasion were all obviously inhibited (P<0.05). The results of IHC showed that JMJD5 was significantly up-regulated compared with normal tissues (P<0.01). Additionally, follow-up data demonstrated that the survival rate of patients with high expression of JMJD5 was obviously lower than that with low expression (P<0.01).

CONCLUSIONS

JMJD5 depletion could significantly inhibit human CC cell proliferation, migration, and invasion, implying that JMJD5 might be a potential oncogene.

Pyruvate kinase M2 accelerates pro-inflammatory cytokine secretion and cell proliferation induced by lipopolysaccharide in colorectal cancer

Surgery-induced inflammation has been associated with cancer recurrence and metastasis in colorectal cancer (CRC). As a constituent of gram-negative bacteria, lipopolysaccharide (LPS) is frequently abundant in the peri-operative window. However, the definite roles of LPS in tumour progression remain elusive. Here we reported that LPS treatment increased PKM expression through activation of NF-κB signalling pathway, and knockdown of PKM reversed LPS-induced TNF-α, IL-1β production and cell proliferation in CRC cells. We further showed that the PKM2 but not PKM1 mediated the pro-inflammatory and proliferative effects of LPS. Interestingly, LPS promoted PKM2 binding to the STAT3 promoter to enhance STAT3 expression and its subsequent nuclear translocation. Depletion of STAT3 decreased PKM2-induced TNF-α and IL-1β expression, indicating that STAT3 mediates the pro-inflammatory effects of PKM2. Furthermore, it is the protein kinase activity but not the pyruvate kinase activity of PKM2 that is required for inflammatory cytokine production. Collectively, our findings reveal the NF-κB-PKM2-STAT3 axis as a novel mechanism for the regulation of TNF-α and IL-1β production and suggest the importance of PKM2 as a key inflammatory mediator in inflammatory microenvironment.

Gene expression profiling for screening of cancer metabolism related genes in CD133+/CD133- colorectal cancer cells derived from colo205 cells

AIM: To obtain differential gene expression information on cancer metabolic reprogramming from colo205 derived colorectal cancer cells.

METHODS: Colo205 cell spheres were cultured in serum-free medium with cell factors, and CD133⁺/CD133^- cells were sorted using an indirect CD133 microbead kit. In vitro differentiation and nude mouse tumorigenicity assay were carried out to test whether CD133⁺ cells have stem cell characteristics or not together with colo205 cells and CD133^- cells. RNA-seq was employed for analysis of differential genes related to cancer metabolic reprogramming and metabolism regulatory genes, followed by verification by qRT-PCR.

RESULTS: Compared with CD133^- cells, 9 cancer metabolism related genes and 6 glycolysis related genes were up-regulated, and 3 cancer metabolism related genes down-regulated in CD133⁺ cells, while 12 cancer metabolism related genes and 6 glycolysis related genes were up-regulated, and 3 cancer metabolism related genes down-regulated in colo205 cells. For glucose transporters, glucose transporter 1 (GLUT1) was up-regulated in CD133⁺ cells, GLUT3 was up-regulated in CD133^- cells, and GLUT4 was up-regulated in colo205 cells. Among the 6 cancer metabolism related genes involved in the tricarboxylic acid (TCA) cycle, glutaminase1 (GLS1) was up-regulated and isocitrate dehydrogenase 2 (IDH2) was down-regulated along with cytochromec oxidase assembly factors 2 (SCO2) in CD133^- cells. The mRNA expression levels of 20 cancer metabolism regulatory genes were changed, including p53, RAS, extracellular regulated protein kinases (ERK), liver kinase B1 (LKB1), protein kinase B (AKT), and TP53-induced glycolysis and apoptosis regulator (TIGAR) that were down-regulated, and hypoxia inducible factor 1α (HIF-1α), IκB kinase (IKK) and epidermal growth factor receptor (EGFR) that were up-regulated in CD133^- cells, and AMP-activated protein kinase (AMPK) and receptor tyrosine kinase (RTK6) that were down-regulated in colo205 cells.

CONCLUSION: Heterogeneity of gene expression profile exists in colo205 cells and colo205 derived CD133^- cells and CD133⁺ cells, which may provide a reference for molecular diagnosis, therapeutic target selection, treatment evaluation and prognosis judgment in colorectal cancer.