Differential phosphofructokinase-1 isoenzyme patterns associated with glycolytic efficiency in human breast cancer and paracancer tissues

Transcriptional regulation and post-translational modifications in the glycolytic pathway for targeted cancer therapy

Cancer cells largely rely on aerobic glycolysis or the Warburg effect to generate essential biomolecules and energy for their rapid growth. The key modulators in glycolysis including glucose transporters and enzymes, e.g. hexokinase 2, enolase 1, pyruvate kinase M2, lactate dehydrogenase A, play indispensable roles in glucose uptake, glucose consumption, ATP generation, lactate production, etc. Transcriptional regulation and post-translational modifications (PTMs) of these critical modulators are important for signal transduction and metabolic reprogramming in the glycolytic pathway, which can provide energy advantages to cancer cell growth. In this review we recapitulate the recent advances in research on glycolytic modulators of cancer cells and analyze the strategies targeting these vital modulators including small-molecule inhibitors and microRNAs (miRNAs) for targeted cancer therapy. We focus on the regulation of the glycolytic pathway at the transcription level (e.g., hypoxia-inducible factor 1, c-MYC, p53, sine oculis homeobox homolog 1, N6-methyladenosine modification) and PTMs (including phosphorylation, methylation, acetylation, ubiquitination, etc.) of the key regulators in these processes. This review will provide a comprehensive understanding of the regulation of the key modulators in the glycolytic pathway and might shed light on the targeted cancer therapy at different molecular levels.

Oxidative Stress in Breast Cancer: A Biochemical Map of Reactive Oxygen Species Production

This review systematizes information about the metabolic features of breast cancer directly related to oxidative stress. It has been shown those redox changes occur at all levels and affect many regulatory systems in the human body. The features of the biochemical processes occurring in breast cancer are described, ranging from nonspecific, at first glance, and strictly biochemical to hormone-induced reactions, genetic and epigenetic regulation, which allows for a broader and deeper understanding of the principles of oncogenesis, as well as maintaining the viability of cancer cells in the mammary gland. Specific pathways of the activation of oxidative stress have been studied as a response to the overproduction of stress hormones and estrogens, and specific ways to reduce its negative impact have been described. The diversity of participants that trigger redox reactions from different sides is considered more fully: glycolytic activity in breast cancer, and the nature of consumption of amino acids and metals. The role of metals in oxidative stress is discussed in detail. They can act as both co-factors and direct participants in oxidative stress, since they are either a trigger mechanism for lipid peroxidation or capable of activating signaling pathways that affect tumorigenesis. Special attention has been paid to the genetic and epigenetic regulation of breast tumors. A complex cascade of mechanisms of epigenetic regulation is explained, which made it possible to reconsider the existing opinion about the triggers and pathways for launching the oncological process, the survival of cancer cells and their ability to localize.

The determinants of metabolic discrepancies in aerobic glycolysis: Providing potential targets for breast cancer treatment

Altered aerobic glycolysis is the robust mechanism to support cancer cell survival and proliferation beyond the maintenance of cellular energy metabolism. Several investigators portrayed the important role of deregulated glycolysis in different cancers, including breast cancer. Breast cancer is the most ubiquitous form of cancer and the primary cause of cancer death in women worldwide. Breast cancer with increased glycolytic flux is hampered to eradicate with current therapies and can result in tumor recurrence. In spite of the low order efficiency of ATP production, cancer cells are highly addicted to glycolysis. The glycolytic dependency of cancer cells provides potential therapeutic strategies to preferentially kill cancer cells by inhibiting glycolysis using antiglycolytic agents. The present review emphasizes the most recent research on the implication of glycolytic enzymes, including glucose transporters (GLUTs), hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), lactate dehydrogenase-A (LDHA), associated signalling pathways and transcription factors, as well as the antiglycolytic agents that target key glycolytic enzymes in breast cancer. The potential activity of glycolytic inhibitors impinges cancer prevalence and cellular resistance to conventional drugs even under worse physiological conditions such as hypoxia. As a single agent or in combination with other chemotherapeutic drugs, it provides the feasibility of new therapeutic modalities against a wide spectrum of human cancers.

Acetyltransferase P300 Regulates Glucose Metabolic Reprogramming through Catalyzing Succinylation in Lung Cancer

Aberrant protein post-translational modification is a hallmark of malignant tumors. Lysine succinylation (Ksucc) plays a vital role in cell energy metabolism in various cancers. However, whether succinylation can be catalyzed by acetyltransferase p300 remains unclear. In this study, we unveiled that p300 is a "writer" for succinylation, and p300-mediated Ksucc promotes cell glycometabolism in lung adenocarcinoma (LUAD). Specifically, our succinylome data revealed that EP300 deficiency leads to the systemic reduction of Ksucc, and 79.55% of the p300-succinylated proteins were found in the cytoplasm, which were primarily enriched in the carbohydrate metabolism process. Interestingly, deleting EP300 led to a notable decrease in Ksucc levels on several glycolytic enzymes, especially Phosphoglycerate Kinase 1 (PGK1). Mutation of the succinylated site of PGK1 notably hindered cell glycolysis and lactic acid excretion. Metabolomics in vivo indicated that p300-caused metabolic reprogramming was mainly attributed to the altered carbohydrate metabolism. In addition, 89.35% of LUAD patients exhibited cytoplasmic localization of p300, with higher levels in tumor tissues than adjacent normal tissues. High levels of p300 correlated with advanced tumor stages and poor prognosis of LUAD patients. Briefly, we disclose the activity of p300 to catalyze succinylation, which contributes to cell glucose metabolic reprogramming and malignant progression of lung cancer.

Protein phosphatase 4 dephosphorylates phosphofructokinase-1 to regulate its enzymatic activity

Most cancer cells utilize glucose at a high rate to produce energyand precursors for the biosynthesis of macromolecules such as lipids, proteins, and nucleic acids. This phenomenon is called the Warburg effect or aerobic glycolysis- this distinct characteristic is an attractive target for developing anticancer drugs. Here, we found that Phosphofructokinase-1 (PFK-1) is a substrate of the Protein Phosphatase 4 catalytic subunit (PP4C)/PP4 regulatory subunit 1 (PP4R1) complex by using immunoprecipitation and in vitro assay. While manipulation of PP4C/PP4R1 does not have a critical impact on PFK-1 expression, the absence of the PP4C/PP4R1 complex increases PFK-1 activity. Although PP4C depletion or overexpression does not cause a dramatic change in the overall glycolytic rate, PP4R1 depletion induces a considerable increase in both basal and compensatory glycolytic rates, as well as the oxygen consumption rate, indicating oxidative phosphorylation. Collectively, the PP4C/PP4R1 complex regulates PFK-1 activity by reversing its phosphorylation and is a promising candidate for treating glycolytic disorders and cancers. Targeting PP4R1 could be a more efficient and safer strategy to avoid pleiotropic effects than targeting PP4C directly. [BMB Reports 2023; 56(11): 618-623].

PFKP is a prospective prognostic, diagnostic, immunological and drug sensitivity predictor across pan-cancer

Phosphofructokinase, platelet (PFKP) is a rate-limiting enzyme of glycolysis that plays a decisive role in various human physio-pathological processes. PFKP has been reported to have multiple functions in different cancer types, including lung cancer and breast cancer. However, no systematic pancancer analysis of PFKP has been performed; this type of analysis could elucidate the clinical value of PFKP in terms of diagnosis, prognosis, drug sensitivity, and immunological correlation. Systematic bioinformation analysis of PFKP was performed based on several public datasets, including The Cancer Genome Atlas (TCGA), Cancer Cell Line Encyclopedia (CCLE), Genotype-Tissue Expression Project (GTEx), and Human Protein Atlas (HPA). Prospective carcinogenesis of PFKP across cancers was estimated by expression analysis, effect on patient prognosis, diagnosis significance evaluation, and immunity regulation estimation. Then, pancancer functional enrichment of PFKP was also assessed through its effect on the signaling score and gene expression profile. Finally, upstream expression regulation of PFKP was explored by promoter DNA methylation and transcription factor (TF) prediction. Our analysis revealed that high expression of PFKP was found in most cancer types. Additionally, a high level of PFKP displayed a significant correlation with poor prognosis in patients across cancers. The diagnostic value of PFKP was performed based on its positive correlation with programmed cell death-ligand 1 (PD-L1). We also found an obvious immune-regulating effect of PFKP in most cancer types. PFKP also had a strong negative correlation with several cancer drugs. Finally, ectopic expression of PFKP may depend on DNA methylation and several predicated transcription factors, including the KLF (KLF transcription factor) and Sp (Sp transcription factor) families. This pancancer analysis revealed that a high expression level of PFKP might be a useful biomarker and predictor in most cancer types. Additionally, the performance of PFKP across cancers also suggested its meaningful role in cancer immunity regulation, even in immunotherapy and drug resistance. Overall, PFKP might be explored as an auxiliary monitor for pancancer early prognosis and diagnosis.

Combination of 3PO analog PFK15 and siPFKL efficiently suppresses the migration, colony formation ability, and PFK-1 activity of triple-negative breast cancers by reducing the glycolysis

Among all the subtypes of breast cancer, triple-negative breast cancer (TNBC) has been associated with the worst prognosis. Recently, for many solid tumors (including breast cancer) metabolic reprogramming has appeared as a cancer cell hallmark, and the elevated glycolytic pathway has been linked to their aggressive phenotype. In the present study, we evaluated the prognostic and therapeutic relevance of PFKFB3 (6-phosphofructo-2- kinase/fructose-2,6-bisphosphatase) in TNBCs. Prognostic significance of PFKFB3 expression was evaluated in overall breast cancers as well as in TNBCs. PFKFB3 inhibitor (3PO potent analogue i.e., PFK15) cytotoxicity in TNBC cell lines (MDA-MB-231 and MDA-MB-468) was analyzed using an MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cancer cell physiological characteristics like clonogenicity and migration were also investigated after PFK15 treatment. As fructose-2,6-bisphosphate (F-2,6-BP), has been associated with increased PFK-1 activity, the effect of PFKFB3 inhibition by PFK15 was investigated on two major isoforms of phosphofructokinase-1 (PFK-1) in breast cancer, that is, phosphofructokinase-platelet type (PFKP) and phosphofructokinase-liver type (PFKL) (relevant to breast cancer). For PFKL inhibition, the siRNA approach was used. PFKFB3 expression was significantly correlated with inferior overall survival in breast cancer patients including TNBCs. PFK15 treatment in TNBC cells (i.e., MDA-MB-231 and MDA-MB-468) resulted in a decreased PFKP expression, thereby leading to reduced colony formation ability, migration rate, and extracellular lactate levels. However, to our surprise PFK15 treatment in both TNBC cells also resulted in elevated PFKL levels. Our results demonstrated that the combinatorial inhibition of PFK15 with siPFKL was more effective in TNBC cells, as it led to a decrease in colony formation ability, migration rate, extracellular lactate levels, and PFK-1 activity when compared with individual treatments. Using bona fide PFKFB3 inhibitor, that is, AZ67, we further show that AZ67 treatment to TNBC cells has no effect either on the expression of PFKP and PFKL, or on the lactate production. In summary, our present in vitro study demonstrated that 3PO derived PFK15 mechanism of action is totally different from AZ67 in TNBC cells. However, we advocate that the PFK15-mediated inhibition (along with PFKL) on the TNBCs migration, colony formation, and PFK-1 activity can be further explored for the therapeutic advantage of TNBC patients.

PFKP: More than phosphofructokinase

Phosphofructokinase (PFK) is one of the key enzymes that functions in glycolysis. Studies show that PFKP regulates cell proliferation, apoptosis, autophagy, cell migration/metastasis, and stemness through glycolysis and glycolysis-independent functions. PFKP performs its function not only in the cytoplasm, but also at the cell membrane, on the mitochondria, at the lysosomal membrane, and in the nucleus. The functions of PFKP are extensively studied in cancer cells. PFKP is also highly expressed in certain immune cells; nevertheless, the study of the PFKP's role in immune cells is limited. In this review, we summarize how the expression and activity of PFKP are regulated in cancer cells. PFKP may be applied as a prognostic marker due to its overexpression and significant functions in cancer cells. As such, specifically targeting/inhibiting PFKP may be a critical and promising strategy for cancer therapy.

Glycolysis regulator PFKP induces human melanoma cell proliferation and tumor growth

PURPOSE

Cutaneous melanoma is an aggressive and deadly cancer resulting from malignant transformation of cells involved in skin pigmentation. Glycolysis is widely implicated in cancer progression, but its precise role in melanoma has not been extensively studied. Here, we investigated the role of the glycolysis regulator phosphofructokinase 1 platelet isoform (PFKP) in melanoma progression.

METHODS

PFKP expression in human melanoma tissues was analyzed by immunohistochemistry. Knockdown of PFKP by siRNA and overexpression of PFKP were performed to evaluate its functions in vitro. CCK-8 assay was used to assess cell proliferation. Glycolytic activity was determined via measurement of extracellular acidification rate (ECAR), lactic acid level, and ATP content. A tumor xenograft model was used to test the function of PFKP in vivo.

RESULTS

PFKP upregulation was observed in human melanoma tissues and correlated with poor patient survival. Knockdown of PFKP in human melanoma cells suppressed cell proliferation and reduced ECAR, ATP levels, and lactic acid levels, while overexpression of PFKP displayed the opposite effects. In vivo, knockdown of PFKP in melanoma cells markedly reduced tumorigenesis. Inhibitory effects on cell proliferation, glycolysis, and tumorigenesis due to PFKP knockdown were further augmented upon treatment with the glycolysis inhibitor 2-deoxy-D-glucose (2-DG).

CONCLUSION

Collectively, these results indicate that PFKP expression in melanoma cells increases proliferation and glycolytic activity in vitro and promotes tumorigenesis in vivo, suggesting that suppression of PKFP and inhibition of glycolysis may potently suppress melanoma progression.

Energy metabolism pathways in breast cancer progression: The reprogramming, crosstalk, and potential therapeutic targets

Breast cancer (BC) is a malignant tumor that seriously endangers health in women. BC, like other cancers, is accompanied by metabolic reprogramming. Among energy metabolism-related pathways, BC exhibits enhanced glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), glutamate metabolism, and fatty acid metabolism activities. These pathways facilitate the proliferation, growth and migration of BC cells. The progression of BC is closely related to the alterations in the activity or expression level of several metabolic enzymes, which are regulated by the intrinsic factors such as the key signaling and transcription factors. The metabolic reprogramming in the progression of BC is attributed to the aberrant expression of the signaling and transcription factors associated with the energy metabolism pathways. Understanding the metabolic mechanisms underlying the development of BC will provide a druggable potential for BC treatment and drug discovery.

Long non-coding RNAs affecting cell metabolism in cancer

Metabolic reprogramming is commonly recognized as one important hallmark of cancers. Cancer cells present significant alteration of glucose metabolism, oxidative phosphorylation, and lipid metabolism. Recent findings demonstrated that long non-coding RNAs control cancer development and progression by modulating cell metabolism. Here, we give an overview of breast cancer metabolic reprogramming and the role of long non-coding RNAs in driving cancer-specific metabolic alteration.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Platelet isoform of phosphofructokinase accelerates malignant features in breast cancer

The platelet isoform of phosphofructokinase (PFKP) is one of the key enzymes in the glycolytic pathway. PFKP is highly expressed in several cancers, and it has been reported to be involved in the progression of cancer cells. However, its oncological role in breast cancer (BC) remains unclear. The present study aimed to evaluate the function of PFKP in BC cells and its expression level in patients with BC. Firstly, the mRNA and protein expression of PFKP was evaluated in BC and non‑cancerous mammary cell lines. Polymerase chain reaction (PCR) array analysis was conducted to evaluate the correlation between PFKP and 84 cancer‑related genes. Then, PFKP knockdown was conducted using small interfering RNA, and cell proliferation, invasiveness and migration were analyzed. Furthermore, the association between PFKP mRNA expression and clinicopathological factors was investigated in 167 patients with BC. PFKP was highly expressed in estrogen receptor‑negative and human epidermal growth factor receptor 2‑negative BC cell lines. PCR array analysis demonstrated that the expression level of PFKP was significantly correlated with that of transforming growth factor‑β1 and MYC proto‑oncogene. PFKP knockdown significantly decreased the proliferation and invasiveness of MCF7, SK‑BR‑3, and MDA‑MB‑231 cells. Furthermore, cell migration was inhibited in SK‑BR‑3 and MDA‑MB‑231 cells. In the clinical specimens, patients with T2/T3/T4, lymph node metastasis, or stage II/III/IV exhibited higher expression of PFKP mRNA than patients with less severe disease. In conclusion, the present findings indicated that PFKP is involved in promoting tumor‑progressive oncological roles in BC cells across different subtypes and is considered a possible novel therapeutic target for BC.

Wnt signaling promotes tumor development in part through phosphofructokinase 1 platelet isoform upregulation

The activation of Wnt signaling has been detected in various types of human cancer and has been shown to be associated with cancer development. In the present study, it was revealed that Wnt signaling induced the expression of phosphofructokinase 1 platelet isoform (PFKP), which has been reported to catalyze a rate‑limiting reaction in glycolysis and is important for the Warburg effect, proliferation, colony formation and cancer cell migration. Moreover, it was demonstrated that Wnt3A induced PFKP expression in a β‑catenin‑independent manner, resulting in increased PFK enzyme activity. Wnt3A‑induced epidermal growth factor receptor transactivation activated PI3K/AKT, which stabilized PFKP through PFKP S386 phosphorylation and subsequent PFKP upregulation. Wnt3A‑induced PFKP S386 phosphorylation increased PFKP expression and promoted the Warburg effect, cell proliferation, colony formation and the migratory ability of cancer cells. On the whole, the findings of the present study underscore the potential role of PFKP in Wnt signaling‑induced tumor development.

Akt Isoforms: A Family Affair in Breast Cancer

Simple Summary

Breast cancer is the second leading cause of cancer-related death in women in the United States. The Akt signaling pathway is deregulated in approximately 70% of patients with breast cancer. While targeting Akt is an effective therapeutic strategy for the treatment of breast cancer, there are several members in the Akt family that play distinct roles in breast cancer. However, the function of Akt isoforms depends on many factors. This review analyzes current progress on the isoform-specific functions of Akt isoforms in breast cancer.

Abstract

Akt, also known as protein kinase B (PKB), belongs to the AGC family of protein kinases. It acts downstream of the phosphatidylinositol 3-kinase (PI3K) and regulates diverse cellular processes, including cell proliferation, cell survival, metabolism, tumor growth and metastasis. The PI3K/Akt signaling pathway is frequently deregulated in breast cancer and plays an important role in the development and progression of breast cancer. There are three closely related members in the Akt family, namely Akt1(PKBα), Akt2(PKBβ) and Akt3(PKBγ). Although Akt isoforms share similar structures, they exhibit redundant, distinct as well as opposite functions. While the Akt signaling pathway is an important target for cancer therapy, an understanding of the isoform-specific function of Akt is critical to effectively target this pathway. However, our perception regarding how Akt isoforms contribute to the genesis and progression of breast cancer changes as we gain new knowledge. The purpose of this review article is to analyze current literatures on distinct functions of Akt isoforms in breast cancer.

Down-Regulating the Expression of miRNA-21 Inhibits the Glucose Metabolism of A549/DDP Cells and Promotes Cell Death Through the PI3K/AKT/mTOR/HIF-1α Pathway

miRNA-21 is a single-stranded non-coding RNA that is highly expressed in a variety of tumor cells. It participates in tumor cell proliferation, metabolism, metastasis, and drug resistance. Here, we tested the potential mechanism of miRNA-21 in cisplatin-resistant non-small cell lung cancer A549/DDP (human lung adenocarcinoma drug-resistant cell line) cells. A549 and A549/DDP RNAs were sequenced to show that miRNA-21 was highly expressed in the latter, and this was verified by qRT-PCR. In addition, we found that miRNA-21 combined with cisplatin can significantly inhibit glycolysis and glycolysis rate-limiting enzyme protein expression in A549/DDP cells. We also found that miRNA-21 combined with cisplatin can promote A549/DDP cell death. Further investigations showed that miRNA-21 combined with cisplatin caused excessive inactivation of the pI3K/AKT/mTOR/HIF-1α signaling pathway in cisplatin-resistant A549/DDP cells. Hence, reduction of the expression of miRNA-21 in combination with cisplatin chemotherapy may effectively improve the therapeutic effect on patients with non-small cell lung cancer, and this may provide a theoretical basis for the treatment of this disease.

Metabolic changes in triple negative breast cancer-focus on aerobic glycolysis

Among breast cancer subtypes, the triple negative breast cancer (TNBC) has the worst prognosis. In absence of any permitted targeted therapy, standard chemotherapy is the mainstay for TNBC treatment. Hence, there is a crucial need to identify potential druggable targets in TNBCs for its effective treatment. In recent times, metabolic reprogramming has emerged as cancer cells hallmark, wherein cancer cells display discrete metabolic phenotypes to fuel cell progression and metastasis. Altered glycolysis is one such phenotype, in which even in oxygen abundance majority of cancer cells harvest considerable amount of energy through elevated glycolytic-flux. In the present review, we attempt to summarize the role of key glycolytic enzymes i.e. HK, Hexokinase; PFK, Phosphofructokinase; PKM2, Pyruvate kinase isozyme type 2; and LDH, Lactate dehydrogenase in TNBCs, and possible therapeutic options presently available.

Investigation of glucose catabolism in hypoxic Mcf 7 breast cancer culture

Hypoxia plays an important role in tumor phenotype and progression and alters glycolysis, with changes in signaling pathways that develop in response to hypoxia. In this study, the effects of oxygen (normoxia/hypoxia) and of glucose levels on the glucose metabolism was investigated in MCF-7 cancer cells. Under either normoxia or hypoxia conditions, the cells were exposed to glucose at different concentrations (0, 5.5, 15 or 55 mM) for either 3, 6, 12, 24 or 48 h. In all groups, cell viability, levels of key enzymes reflecting glycolytic metabolism in cell lysates, glucose consumed in the medium and extracellular lactate levels and wound closure percentages were determined. In hypoxic cells, intracellular consumption of glucose, and extracellular lactate levels due to increased glucose concentration were observed to be higher (compared to normoxia) and as a result of prolonged exposure to hypoxia, cells were observed to develop resistance to the prolonged exposure to hypoxia. The number of glycolytic enzymes obtained at different levels proved that cells had different potential capacities and changing mechanisms for the metabolic needs of the cell depending on the glucose amount in the medium and time in adapting to the oxygen tension. This study showed that there was an important interaction between hypoxia and glucose metabolism in general, and it was concluded that metabolic processes activated by hypoxia could offer new therapeutic targets.

A control theoretic three timescale model for analyzing energy management in mammalian cancer cells

Interaction among different pathways, such as metabolic, signaling and gene regulatory networks, of cellular system is responsible to maintain homeostasis in a mammalian cell. Malfunctioning of this cooperation may lead to many complex diseases, such as cancer and type 2 diabetes. Timescale differences among these pathways make their integration a daunting task. Metabolic, signaling and gene regulatory networks have three different timescales, such as, ultrafast, fast and slow respectively. The article deals with this problem by developing a support vector regression (SVR) based three timescale model with the application of genetic algorithm based nonlinear controller. The proposed model can successfully capture the nonlinear transient dynamics and regulations of such integrated biochemical pathway under consideration. Besides, the model is quite capable of predicting the effects of certain drug targets for many types of complex diseases. Here, energy and cell proliferation management of mammalian cancer cells have been explored and analyzed with the help of the proposed novel approach. Previous investigations including in silico/in vivo/in vitro experiments have validated the results (the regulations of glucose transporter 1 (glut1), hexokinase (HK), and hypoxia-inducible factor-1 α (HIF-1 α ) among others, and the switching of pyruvate kinase (M2 isoform) between dimer and tetramer) generated by this model proving its effectiveness. Subsequently, the model predicts the effects of six selected drug targets, such as, the deactivation of transketolase and glucose-6-phosphate isomerase among others, in the case of mammalian malignant cells in terms of growth, proliferation, fermentation, and energy supply in the form of adenosine triphosphate (ATP).

Digging deeper through glucose metabolism and its regulators in cancer and metastasis

Glucose metabolism enzymes and transporters play major role in cancer development and metastasis. In this study, we discuss glucose metabolism, transporters, receptors, hormones, oncogenes and tumor suppressors which interact with glucose metabolism and we try to discuss their major role in cancer development and cancer metabolism. We try to highlight the. Metabolic changes in cancer and metastasis upregulation of glycolysis is observed in many primary and metastatic cancers and aerobic glycolysis is the most favorable mechanism for glucose metabolism in cancer cells, and it is a kind of evolutionary change. The question that is posed at this juncture is: Can we use aerobic glycolysis phenotype and enzymes beyond this mechanism in estimating cancer prognosis and metastasis? Lactate is a metabolite of glucose metabolism and it is a key player in cancer and metastasis in both normoxic and hypoxic condition so lactate dehydrogenase can be a good prognostic biomarker. Furthermore, monocarboxylic transporter which is the main lactate transporter can be good target in therapeutic studies. Glycolysis enzymes are valuable enzymes in cancer and metastasis diagnosis and can be used as therapeutic targets in cancer treatment. Designing a diagnostic and prognostic profile for cancer metastasis seems to be possible base on glycolysis enzymes and glucose transporters. Also, glucose metabolism enzymes and agents can give us a clear vision in estimating cancer metastasis. We can promote a panel of genes that detect genetic changes in glucose metabolism agents to diagnose cancer metastasis.

Prognostic and therapeutic relevance of phosphofructokinase platelet-type (PFKP) in breast cancer

In the present study, we have explored the prognostic value of the Phosphofructokinase Platelet-type (PFKP) expression and its therapeutic relevance in metastatic breast cancer. PFKP immunohistochemistry was performed on Invasive ductal carcinomas (IDCs; n = 87) of breast, and its association with clinicopathological parameters were evaluated. Using online meta-analysis tools, PFKP's prognostic value was investigated in overall breast cancer as well as in triple negative subtype (TNBCs). For in vitro analysis, MDA-MB-231 cells model was used in order to elucidate mechanisms behind PFKP regulated glycolysis and its impact on cancer cell physiology. Therapeutic relevance of PFKP was further evaluated using PFKP siRNA and Quercetin. PFKP protein expression was found to be positively associated with nodal invasion (p = 0.009), receptor (ER & PR) negative status (p = 0.005 & p = 0.028) and reduced overall survival in breast cancer patients (p = 0.014). In MDA-MB-231 cells, quercetin treatment impaired PFKP-LDHA signaling axis thereby inhibiting aerobic glycolysis mediated increased migration of cancer cells. Our present study demonstrates that elevated PFKP levels are associated with basal cells/TNBC subtypes and might serve as prognostic indicator for TNBC patients. Ability of quercetin to inhibit aerobic glycolysis, cell migration and clonogenic potential of malignant breast cancer cells advocates possibility of quercetin in aggressive breast cancer treatment.

Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages

Background

Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important infectious disease pathogen that can survive and replicate in macrophages. Glycolysis is essential for immune responses against S. Typhimurium infection in macrophages, and is also associated with apoptosis. S. Typhimurium secreted effector K3 (SseK3) was recently identified as a novel translated and secreted protein. However, there is no study about the role of sseK3 in the relationship between apoptosis and glycolysis in cells infected with S. Typhimurium. It is unclear whether this protein exerts a significant role in the progress of apoptosis and glycolysis in S. Typhimurium-infected macrophages.

Results

Macrophages were infected with S. Typhimurium SL1344 wild-type (WT), ΔsseK3 mutant or sseK3-complemented strain, and the effects of sseK3 on apoptosis and glycolysis were determined. The adherence and invasion in the ΔsseK3 mutant group were similar to that in the WT and sseK3-complemented groups, indicating that SseK3 was not essential for the adherence and invasion of S. Typhimurium in macrophages. However, the percentage of apoptosis in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. Caspase-3, caspase-8, and caspase-9 enzyme activity in the ΔsseK3 mutant group were significantly lower than in the WT group and sseK3-complemented groups, indicating that sseK3 could improve the caspase-3, caspase-8, and caspase-9 enzyme activity. We also found that there were no significant differences in pyruvic acid levels between the three groups, but the lactic acid level in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. The ATP levels in the ΔsseK3 mutant group were remarkably higher than those in the WT and sseK3-complemented groups. These indicated that the sseK3 enhanced the level of glycolysis in macrophages infected by S. Typhimurium.

Conclusions

S. Typhimurium sseK3 is likely involved in promoting macrophage apoptosis and modulating glycolysis in macrophages. Our results could improve our understanding of the relationship between apoptosis and glycolysis in macrophages induced by S. Typhimurium sseK3.

PFKP is transcriptionally repressed by BRCA1/ZBRK1 and predicts prognosis in breast cancer

Objectives

The present study aims to elucidate the underlying mechanism how PFKP is regulated by BRCA1 and the clinical significance of PFKP in breast cancer.

Methods

MEF-BRCA1^△/△ and the wild type counterpart MEF-BRCA1^+/+ cell lines were used to test the sensitivity of glucose depletion in culture medium. Glucose Assay Kit was used to quantify glucose levels in cultural supernatant and cell lysate. Real time PCR was used to measure the mRNA expression levels of genes. Western blot was used to detect protein levels. Chromatin immunoprecipitation was used to verify the bindings between transcription factors and DNA elements. Luciferase reporter assay was performed to determine the transcriptional activity. Histochemistry assay was performed on tissue microarray.

Results

We found that MEF-BRCA1^△/△ cells consumed more glucose and were more vulnerable to glucose-deprived culture medium. The mRNA profiles and qPCR assay of MEF-BRCA1^△/△ and MEF-BRCA1^+/+ cells revealed that PFKP, the rate-limiting enzyme of glycolysis, was significantly upregulated in MEF-BRCA1^△/△ cells. Consistently, the repressive effects of BRCA1 on PFKP were confirmed by overexpression or knockdown of BRCA1. Moreover, we also demonstrated that PFKP was suppressed by ZBRK1 as well, which was the co-repression partner of BRCA1. Mechanistically, we figured out that BRCA1 formed a transcriptional repression complex with ZBRK1 on the promoter of PFKP and consequently restrained its expression. Importantly, the expression levels of PFKP were demonstrated to associate with poor survival of patients with breast cancer.

Conclusion

Our study provided a new insight into the dysregulation of glycolysis in breast cancer, which might be partially due to the deficiency of BRCA1/ZBRK1 axis and subsequently reversed the transcriptional repressive effect on PFKP. We also found that PFKP overexpressed in a subset of breast cancer patients and could serve as a prognostic factor, which represented a potential target for BC therapy.

PFKP is highly expressed in lung cancer and regulates glucose metabolism

PURPOSE

Although it has been reported that up-regulation of phosphofructokinase (PFK) expression is a major feature of malignant tumors, the role of platelet type PFK (PFKP) in tumor initiation and progression is as yet poorly understood. The objective of this study was to evaluate PFKP expression in lung cancer and its effect on glycolysis, and to explore correlations between PFKP expression levels and clinical lung cancer patient features.

METHODS

PFKP mRNA expression levels in cancer tissues and adjacent normal tissues were compared using The Cancer Genome Atlas (TCGA) database. PFKP mRNA and protein expression levels in fresh lung cancer tissues and cell lines were assessed using quantitative real-time PCR and Western blotting. Immunohistochemistry (IHC) was used to assess PFKP expression in 150 archival lung adenocarcinoma samples, after which follow-up data and their correlations with clinical features and patient prognosis were evaluated. A retroviral shRNA-mediated method was used to construct stable cell lines expressing low levels of PFKP. Glucose, lactate and adenosine triphosphate concentrations in the cell culture supernatants were determined using enzymatic, spectrophotometric and enzyme-linked immunosorbent (ELISA) assays, respectively. The effect of PFKP expression on the proliferation of lung cancer cells was assessed using colony forming, MTT and flow cytometry assays, respectively. Finally, data from tissue samples of 533 patients with lung adenocarcinoma and 502 patients with lung squamous cell carcinoma were downloaded from the TCGA database, after which pathway and gene correlation information was retrieved using gene set enrichment analyses.

RESULTS

We found that PFKP was highly expressed in lung cancer tissues and cell lines. Using IHC we found that PFKP was highly expressed in primary lung adenocarcinoma tissues and that a high expression was associated with a poor prognosis. Clinical data analysis revealed that the PFKP expression levels correlated with tumor size and patient survival. Lung cancer cell lines with decreased PFKP expression levels showed significant decreases in glucose uptake rates, lactate levels and adenosine triphosphate concentrations. They also exhibited significantly decreased proliferation rates, colony forming abilities and increased G2/M cell cycle phase percentages. Gene set enrichment analysis revealed that multiple pathways, including glycolytic pathways, may be involved in the regulation PFKP.

CONCLUSIONS

Our data indicate that PFKP is highly expressed in lung cancer tissues and cell lines and is associated with tumor size and patient prognosis. As such, PFKP may serve as a prognostic biomarker. We also found that PFKP regulates the level of glycolysis in lung cancer cells and is associated with lung cancer cell proliferation. These data may be instrumental for the design of new lung cancer treatment options.

Energy Metabolism in Cancer: The Roles of STAT3 and STAT5 in the Regulation of Metabolism-Related Genes

A central characteristic of many types of cancer is altered energy metabolism processes such as enhanced glucose uptake and glycolysis and decreased oxidative metabolism. The regulation of energy metabolism is an elaborate process involving regulatory proteins such as HIF (pro-metastatic protein), which reduces oxidative metabolism, and some other proteins such as tumour suppressors that promote oxidative phosphorylation. In recent years, it has been demonstrated that signal transducer and activator of transcription (STAT) proteins play a pivotal role in metabolism regulation. STAT3 and STAT5 are essential regulators of cytokine- or growth factor-induced cell survival and proliferation, as well as the crosstalk between STAT signalling and oxidative metabolism. Several reports suggest that the constitutive activation of STAT proteins promotes glycolysis through the transcriptional activation of hypoxia-inducible factors and therefore, the alteration of mitochondrial activity. It seems that STAT proteins function as an integrative centre for different growth and survival signals for energy and respiratory metabolism. This review summarises the functions of STAT3 and STAT5 in the regulation of some metabolism-related genes and the importance of oxygen in the tumour microenvironment to regulate cell metabolism, particularly in the metabolic pathways that are involved in energy production in cancer cells.

Metabolic crosstalk in the breast cancer microenvironment

During tumorigenesis, breast tumour cells undergo metabolic reprogramming, which generally includes enhanced glycolysis, tricarboxylic acid cycle activity, glutaminolysis and fatty acid biosynthesis. However, the extension and functional importance of these metabolic alterations may diverge not only according to breast cancer subtypes, but also depending on the interaction of cancer cells with the complex surrounding microenvironment. This microenvironment comprises a variety of non-cancerous cells, such as immune cells (e.g. macrophages, lymphocytes, natural killer cells), fibroblasts, adipocytes and endothelial cells, together with extracellular matrix components and soluble factors, which influence cancer progression and are predictive of clinical outcome. The continuous interaction between cancer and stromal cells results in metabolic competition and symbiosis, with oncogenic-driven metabolic reprogramming of cancer cells shaping the metabolism of neighbouring cells and vice versa. This review addresses current knowledge on this metabolic crosstalk within the breast tumour microenvironment (TME). Improved understanding of how metabolism in the TME modulates cancer development and evasion of tumour-suppressive mechanisms may provide clues for novel anticancer therapeutics directed to metabolic targets.

EGFR-Phosphorylated Platelet Isoform of Phosphofructokinase 1 Promotes PI3K Activation

EGFR activates phosphatidylinositide 3-kinase (PI3K), but the mechanism underlying this activation is not completely understood. We demonstrated here that EGFR activation resulted in lysine acetyltransferase 5 (KAT5)-mediated K395 acetylation of the platelet isoform of phosphofructokinase 1 (PFKP) and subsequent translocation of PFKP to the plasma membrane, where the PFKP was phosphorylated at Y64 by EGFR. Phosphorylated PFKP binds to the N-terminal SH2 domain of p85α, which is distinct from binding of Gab1 to the C-terminal SH2 domain of p85α, and recruited p85α to the plasma membrane resulting in PI3K activation. PI3K-dependent AKT activation results in enhanced phosphofructokinase 2 (PFK2) phosphorylation and production of fructose-2,6-bisphosphate, which in turn promotes PFK1 activation. PFKP Y64 phosphorylation-enhanced PI3K/AKT-dependent PFK1 activation and GLUT1 expression promoted the Warburg effect, tumor cell proliferation, and brain tumorigenesis. These findings underscore the instrumental role of PFKP in PI3K activation and enhanced glycolysis through PI3K/AKT-dependent positive-feedback regulation.

Stabilization of phosphofructokinase 1 platelet isoform by AKT promotes tumorigenesis

Phosphofructokinase 1 (PFK1) plays a critical role in glycolysis; however, its role and regulation in tumorigenesis are not well understood. Here, we demonstrate that PFK1 platelet isoform (PFKP) is the predominant PFK1 isoform in human glioblastoma cells and its expression correlates with total PFK activity. We show that PFKP is overexpressed in human glioblastoma specimens due to an increased stability, which is induced by AKT activation resulting from phosphatase and tensin homologue (PTEN) loss and EGFR-dependent PI3K activation. AKT binds to and phosphorylates PFKP at S386, and this phosphorylation inhibits the binding of TRIM21 E3 ligase to PFKP and the subsequent TRIM21-mediated polyubiquitylation and degradation of PFKP. PFKP S386 phosphorylation increases PFKP expression and promotes aerobic glycolysis, cell proliferation, and brain tumor growth. In addition, S386 phosphorylation in human glioblastoma specimens positively correlates with PFKP expression, AKT S473 phosphorylation, and poor prognosis. These findings underscore the potential role and regulation of PFKP in human glioblastoma development.Phosphofructokinase 1 (PFK1) plays a critical role in glycolysis. Here the authors show that PFK1 platelet isoform is upregulated in Glioblastoma and is required for tumor growth mechanistically, such upregulation is due to an increased stability induced by AKT activation via phosphorylation on residue S386.

Partial Substitution of Glucose with Xylitol Suppressed the Glycolysis and Selectively Inhibited the Proliferation of Oral Cancer Cells

Suitable diet for cancer survivors remains an unresolved challenge. Increased glucose utilization is a hallmark of various cancers. Therefore, alternative carbohydrate supplying normal tissue but retarding cancer growth is needed. This study investigated the effect of sugar alcohols on the proliferation of oral cancer cells compared to nontransformed cells and explored the mechanism. Six oral squamous cell carcinoma (CAL-27, FaDu, SCC4, SCC9, SCC15, and SCC25) and one nontransformed oral keratinocyte (OKF6/TERT2) lines were cultured in media containing 1 mg/ml glucose and 5.8 mg/ml xylitol or sorbitol, yielding equal energy input to control group (4.5 mg/ml glucose). Partial substitution of glucose with sugar alcohols especially xylitol significantly suppressed proliferation of oral cancer but not nontransformed cells. Despite the addition of isocaloric quantities of the sugars, cancer cells exposed to low glucose plus xylitol had retarded ATP generation and decreased activity of phosphofructokinase (PFK), the rate-limiting enzyme in glycolysis. Furthermore, D-xylulose, its key metabolic intermediate, enhanced the anticancer effect of xylitol. These findings suggested a selective anticancer activity of xylitol and the potential mechanism involving inhibition of glucose utilization. Partial substitution of glucose with xylitol may be a proper nutrient for oral cancer survivors, deserving further investigation in animal and clinical settings.

Snail reprograms glucose metabolism by repressing phosphofructokinase PFKP allowing cancer cell survival under metabolic stress

Dynamic regulation of glucose flux between aerobic glycolysis and the pentose phosphate pathway (PPP) during epithelial–mesenchymal transition (EMT) is not well-understood. Here we show that Snail (SNAI1), a key transcriptional repressor of EMT, regulates glucose flux toward PPP, allowing cancer cell survival under metabolic stress. Mechanistically, Snail regulates glycolytic activity via repression of phosphofructokinase, platelet (PFKP), a major isoform of cancer-specific phosphofructokinase-1 (PFK-1), an enzyme involving the first rate-limiting step of glycolysis. The suppression of PFKP switches the glucose flux towards PPP, generating NADPH with increased metabolites of oxidative PPP. Functionally, dynamic regulation of PFKP significantly potentiates cancer cell survival under metabolic stress and increases metastatic capacities in vivo. Further, knockdown of PFKP rescues metabolic reprogramming and cell death induced by loss of Snail. Thus, the Snail-PFKP axis plays an important role in cancer cell survival via regulation of glucose flux between glycolysis and PPP.

Cancer cell survival under metabolic stress is a critical step for metastasis. Here, the authors show that under glucose deprivation, Snail, a key regulator of the metastatic process, promotes survival by diverting glucose to the pentose phosphate pathway through repression of phosphofructokinase PFKP.

Phosphofructokinase-1 Negatively Regulates Neurogenesis from Neural Stem Cells

Phosphofructokinase-1 (PFK-1), a major regulatory glycolytic enzyme, has been implicated in the functions of astrocytes and neurons. Here, we report that PFK-1 negatively regulates neurogenesis from neural stem cells (NSCs) by targeting pro-neural transcriptional factors. Using in vitro assays, we found that PFK-1 knockdown enhanced, and PFK-1 overexpression inhibited the neuronal differentiation of NSCs, which was consistent with the findings from NSCs subjected to 5 h of hypoxia. Meanwhile, the neurogenesis induced by PFK-1 knockdown was attributed to the increased proliferation of neural progenitors and the commitment of NSCs to the neuronal lineage. Similarly, in vivo knockdown of PFK-1 also increased neurogenesis in the dentate gyrus of the hippocampus. Finally, we demonstrated that the neurogenesis mediated by PFK-1 was likely achieved by targeting mammalian achaete-scute homologue-1 (Mash 1), neuronal differentiation factor (NeuroD), and sex-determining region Y (SRY)-related HMG box 2 (Sox2). All together, our results reveal PFK-1 as an important regulator of neurogenesis.

The Effects of Severe Hypoxia on Glycolytic Flux and Enzyme Activity in a Model of Solid Tumors

Solid tumors contend with, and adapt to, a hostile micro-environment that includes limited availability of nutrient fuels and oxygen. The presence of hypoxia (O2 <5%) stabilizes the transcription factor Hif1 and results in numerous cellular adaptations including increased flux of glucose through glycolysis. Increasingly, more sophisticated analysis of tumor oxygenation has revealed large gradients of oxygen tension and significant regions under severe hypoxia (O2 ∼0.1%). The present investigation has demonstrated a significant increase in the glycolytic flux rate when tumor spheroids were exposed to 0.1% O2 . The severe hypoxia was associated with uniform pimonidazole adduct formation and elevated levels of Hif1α and c-Myc. This resulted in elevated expression of GLUT and MCT transporters, in addition to increased activity of PFK1 in comparison to that observed in normoxia. However, the protein expression and enzymatic capacity of HK2, G6PDH, PK, and LDH were all reduced by severe hypoxia. Clearly, the effects of exposure to severe hypoxia lead to a significantly abridged Hif1 response, yet one still able to elevate glycolytic flux and prevent loss of intermediates to anabolism. J. Cell. Biochem. 117: 1890-1901, 2016. © 2016 Wiley Periodicals, Inc.

A strategy for improving FDG accumulation for early detection of metastasis from primary pancreatic cancer: stimulation of the Warburg effect in AsPC-1 cells

INTRODUCTION

Early detection and/or prediction of metastasis provide more prognostic relevance than local recurrence. Direct spread into the peritoneum is frequently found in pancreatic cancer patients, but positron emission tomography (PET) with 2-deoxy-2-fluoro-d-glucose (FDG) is not useful for identifying such metastasis. We investigated a method to enhance FDG accumulation using AsPC-1 human ascites tumor cells.

METHODS

(14)C-FDG accumulation was assessed under the following conditions: 1) characteristics of (14)C-FDG transport were examined using phloridzin, a Na(+)-free buffer, and various hexoses, and 2) accumulation of (14)C-FDG was measured in cells that were pretreated with hexose for various time periods, and activity of 6-phosphofructo-1-kinase (PFK-1) was assayed.

RESULTS

(14)C-FDG transport into AsPC-1 cells was mediated primarily by a Na(+)-independent transport mechanism. Aldohexoses such as d-glucose, D-mannose, and D-galactose inhibited (14)C-FDG transport. Cells pretreated with d-glucose, D-mannose, or D-fructose exhibited augmented (14)C-FDG accumulation. Pretreatment with higher concentrations of D-glucose or D-fructose tended to increase PFK-1 activity.

CONCLUSIONS

Very little information has been published about the association between PFK-1 and FDG accumulation, and we confirmed the impacts of various hexoses on the activity of PFK-1 and FDG accumulation in AsPC-1 cells. Clarifying the relevance of PFK-1 in FDG accumulation will contribute to developing new features of FDG-PET, because PFK-1 is the main regulator of glycolysis.

Cancer cell metabolism and the modulating effects of nitric oxide

Altered metabolic phenotype has been recognized as a hallmark of tumor cells for many years, but this aspect of the cancer phenotype has come into greater focus in recent years. NOS2 (inducible nitric oxide synthase of iNOS) has been implicated as a component in many aggressive tumor phenotypes, including melanoma, glioblastoma, and breast cancer. Nitric oxide has been well established as a modulator of cellular bioenergetics pathways, in many ways similar to the alteration of cellular metabolism observed in aggressive tumors. In this review we attempt to bring these concepts together with the general hypothesis that one function of NOS2 and NO in cancer is to modulate metabolic processes to facilitate increased tumor aggression. There are many mechanisms by which NO can modulate tumor metabolism, including direct inhibition of respiration, alterations in mitochondrial mass, oxidative inhibition of bioenergetic enzymes, and the stimulation of secondary signaling pathways. Here we review metabolic alterations in the context of cancer cells and discuss the role of NO as a potential mediator of these changes.

Heterogeneity of glycolysis in cancers and therapeutic opportunities

Upregulated glycolysis, both in normoxic and hypoxic environments, is a nearly universal trait of cancer cells. The enormous difference in glucose metabolism offers a target for therapeutic intervention with a potentially low toxicity profile. The past decade has seen a steep rise in the development and clinical assessment of small molecules that target glycolysis. The enzymes in glycolysis have a highly heterogeneous nature that allows for the different bioenergetic, biosynthetic, and signaling demands needed for various tissue functions. In cancers, these properties enable them to respond to the variable requirements of cell survival, proliferation and adaptation to nutrient availability. Heterogeneity in glycolysis occurs through the expression of different isoforms, posttranslational modifications that affect the kinetic and regulatory properties of the enzyme. In this review, we will explore this vast heterogeneity of glycolysis and discuss how this information might be exploited to better target glucose metabolism and offer possibilities for biomarker development.

Association of cancer metabolism-related proteins with oral carcinogenesis - indications for chemoprevention and metabolic sensitizing of oral squamous cell carcinoma?

Background

Tumor metabolism is a crucial factor for the carcinogenesis of oral squamous cell carcinoma (OSCC).

Methods

Expression of IGF-R1, glycolysis-related proteins (GLUT-1, HK 2, PFK-1, LDHA, TKTL1), mitochondrial enzymes (SDHA, SDHB, ATP synthase) were analyzed in normal oral mucosa (n = 5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen (n = 42) by immunohistochemistry and real-time polymerase chain reaction (qPCR) analysis in OSCC cell lines. Metabolism-related proteins were correlated with proliferation activity (Ki-67) and apoptotic properties (TUNEL assay) in OSCC. Specificity of antibodies was confirmed by western blotting in cancer cell lines.

Results

Expression of IGF-R1, glycolysis-related proteins (GLUT-1, HK 2, LDHA, TKTL1), and mitochondrial enzymes (SDHA, SDHB, ATP synthase) were significantly increased in the carcinogenesis of OSCC. Metabolic active regions of OSCC were strongly correlated with proliferating cancer (Ki-67+) cells without detection of apoptosis (TUNEL assay).

Conclusions

This study provides the first evidence of the expression of IGF-R1, glycolysis-related proteins GLUT-1, HK 2, PFK-1, LDHA, and TKTL1, as well as mitochondrial enzymes SDHA, SDHB, and ATP synthase in the multi-step carcinogenesis of OSCC. Both, hypoxia-related glucose metabolism and mitochondrial oxidative phosphorylation characteristics are associated with the carcinogenesis of OSCC. Acidosis and OXPHOS may drive a metabolic shift towards the pentose phosphate pathway (PPP). Therefore, inhibition of the PPP, glycolysis, and targeted anti-mitochondrial therapies (ROS generation) by natural compounds or synthetic vitamin derivatives may act as sensitizer for apoptosis in cancer cells mediated by adjuvant therapies in OSCC.