Tumour M2-pyruvate kinase: a gastrointestinal cancer marker

ERK/PKM2 Is Mediated in the Warburg Effect and Cell Proliferation in Arsenic-Induced Human L-02 Hepatocytes

This study aimed to investigate the potential role of pyruvate kinase M2 (PKM2) and extracellular regulated protein kinase (ERK) in arsenic-induced cell proliferation. L-02 cells were treated with 0.2 and 0.4 μmol/L As3+, glycolysis inhibitor (2-deoxy-D-glucose,2-DG), ERK inhibitor [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)-butadiene, U0126] or transfected with PKM2 plasmid. Cell viability, proliferation, lactate acid production, and glucose intake capacity were determined by CCK-8 assay, EdU assay, lactic acid kit and 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]-D-glucose (2-NBDG) uptake kit, respectively. Also, levels of PKM2, phospho-PKM2S37, glucose transporter protein 1 (GLUT1), lactate dehydrogenase A (LDHA), ERK, and phospho-ERK were detected using Western blot and the subcellular localization of PKM2 in L-02 cells was detected by immunocytochemistry (ICC). Treatment with 0.2 and 0.4 μmol/L As3+ for 48 h increased the viability and proliferation of L-02 cells, the proportion of 2-NBDG+ cell and lactic acid in the culture medium, and GLUT1, LDHA, PKM2, phospho-PKM2S37, and phospho-ERK levels and PKM2 in nucleus. Compared with the 0.2 μmol/L As3+ treatment group, the lactic acid in the culture medium, cell proliferation and cell viability, and the expression of GLUT1 and LDHA were reduced in the group co-treated with siRNA-PKM2 and arsenic or in the group co-treated with U0126. Moreover, the arsenic-increased phospho-PKM2S37/PKM2 was decreased by U0126. Therefore, ERK/PKM2 plays a key role in the Warburg effect and proliferation of L-02 cells induced by arsenic, and also might be involved in arsenic-induced upregulation of GLUT1 and LDHA. This study provides a theoretical basis for further elucidating the carcinogenic mechanism of arsenic.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

The Importance of Evaluating Serum Levels of Tumor Markers M2-PK and Inhibin A in Patients Undergoing Colonoscopy

Despite the use of colonoscopy to detect colon cancer due to its aggressiveness, high cost, and lack of patient compliance, the use of laboratory tests with high accuracy and sensitivity, such as tumor marker M2-PK and Inhibin A is recommended and can be effective for early diagnosis and screening of patients in the early stages. We studied 46 patients admitted it the gastrointestinal ward of Amir al Momenin Hospital and 45 normal (age and sex-matched) subjects as a control group (case-control and retrospective studies). Before the colonoscopy, the level of tumor marker M2-PK in the stool sample and the serum level of Inhibin A were evaluated in patients and the control group. The level of tumor marker M2-PK was significantly higher in the group with hyperplastic polyps and colon cancer (P < .001) than in the control group. At the same time, there was no significant difference in Inhibin A level (P = .054). In the hyperplastic polyps group 73% and in the colorectal cancer group 27% had a positive immunochemical fecal occult blood (IFOBT) result, significantly higher than the control group (P < .001). Evaluation of the level of tumor marker M2-PK in the stool sample in association with the three-time iFOBT test method may be suggested as a quick and noninvasive method for screening and diagnosis of polyps and early stages of colon cancer.

Unraveling the Complex Interactions between the Fat Mass and Obesity-Associated (FTO) Gene, Lifestyle, and Cancer

Carcinogenesis is a complicated process and originates from genetic, epigenetic, and environmental factors. Recent studies have reported a potential critical role for the fat mass and obesity-associated (FTO) gene in carcinogenesis through different signaling pathways such as mRNA N6-methyladenosine (m6A) demethylation. The most common internal modification in mammalian mRNA is the m6A RNA methylation that has significant biological functioning through regulation of cancer-related cellular processes. Some environmental factors, like physical activity and dietary intake, may influence signaling pathways engaged in carcinogenesis, through regulating FTO gene expression. In addition, people with FTO gene polymorphisms may be differently influenced by cancer risk factors, for example, FTO risk allele carriers may need a higher intake of nutrients to prevent cancer than others. In order to obtain a deeper viewpoint of the FTO, lifestyle, and cancer-related pathway interactions, this review aims to discuss upstream and downstream pathways associated with the FTO gene and cancer. The present study discusses the possible mechanisms of interaction of the FTO gene with various cancers and provides a comprehensive picture of the lifestyle factors affecting the FTO gene as well as the possible downstream pathways that lead to the effect of the FTO gene on cancer.

Extracellular PKM2 facilitates organ-tissue fibrosis progression

Persistent activation of fibroblasts and resistance of myofibroblasts to turnover play important roles in organ-tissue fibrosis development and progression. The mechanism that mediates apoptosis resistance of myofibroblasts is not understood. Here, we report that myofibroblasts express and secrete PKM2. Extracellular PKM2 (EcPKM2) facilitates progression of fibrosis by protecting myofibroblasts from apoptosis. EcPKM2 upregulates arginase-1 expression in myofibroblasts and therefore facilitates proline biosynthesis and subsequent collagen production. EcPKM2 interacts with integrin αvβ3 on myofibroblasts to activate FAK-PI3K signaling axis. Activation of FAK-PI3K by EcPKM2 activates downstream NF-κB survival pathway to prevent myofibroblasts from apoptosis. On the other hand, activation of FAK- PI3K by EcPKM2 suppresses PTEN to subsequently upregulate arginase-1 in myofibroblasts. Our studies uncover an important mechanism for organ fibrosis progression. More importantly, an antibody disrupting the interaction between PKM2 and integrin αvβ3 is effective in reversing fibrosis, suggesting a possible therapeutic strategy and target for treatment of organ fibrosis.

Advances of Tumorigenesis, Diagnosis at Early Stage, and Cellular Immunotherapy in Gastrointestinal Malignancies

Globally, in 2018, 4.8 million new patients have a diagnosis of gastrointestinal (GI) cancers, while 3.4 million people died of such disorders. GI malignancies are tightly relevant to 26% of the world-wide cancer incidence and occupies 35% of all cancer-associated deaths. In this article, we principally investigated molecular and cellular mechanisms of tumorigenesis in five major GI cancers occurring at esophagus, stomach, liver, pancreas, and colorectal region that illustrate high morbidity in Eastern and Western countries. Moreover, through this investigation, we not only emphasize importance of the tumor microenvironment in development and treatment of malignant tumors but also identify significance of M2PK, miRNAs, ctDNAs, circRNAs, and CTCs in early detection of GI cancers, as well as systematically evaluate contribution of personalized precision medicine including cellular immunotherapy, new antigen and vaccine therapy, and oncolytic virotherapy in treatment of GI cancers.

Aziz SH, Zakaria Z, Wong MPK, Zakaria AD. The Use of M2-Pyruvate Kinase as a Stool Biomarker for Detection of Colorectal Cancer in Tertiary Teaching Hospital: A Comparative Study

PURPOSE

Guaiac fecal occult blood test (gFOBT) has been the standard for colorectal screening but it has low sensitivity and specificity. This study evaluated the use of fecal tumor M2-pyruvate kinase (M2-PK) for detection of colorectal cancer and to compare with the current surveillance tool; gFOBT in symptomatic adult subjects underwent colonoscopy.

METHODS

Stool samples were collected prospectively from symptomatic adults who had elective colonoscopy from September 2014 to January 2016 and were analyzed with the ScheBo M2-PK Quick test and laboratory detection of fecal hemoglobin.

RESULTS

The results were correlated to the colonoscopy findings and/or histopathology report. Eighty-five subjects (age of 56.8 ± 15.3 years [mean ± standard deviation]) were recruited with a total of 17 colorectal cancer (20.0%) and 10 colorectal adenoma patients (11.8%). The sensitivity of M2-PK test in colorectal cancer detection was higher than gFOBT (100% vs. 64.7%). M2-PK test had a lower specificity when compared to gFOBT (72.5% vs. 88.2%) in colorectal cancer detection. The positive and negative predictive values were 47.2% and 100% for M2-PK test and 57.9% and 90.9% for gFOBT.

CONCLUSION

Fecal M2-PK Quick test has a high sensitivity for detection of colorectal cancer when compared to gFOBT, making it the potential choice for colorectal tumor screening biomarker in the future.

Significant association of PKM2 and NQO1 proteins with poor prognosis in breast cancer

Pyruvate kinase M2 (PKM2) and NAD(P)H:quinone oxidoreductase-1 (NQO1) have been known to play significant functions in tumorigenesis and development. The association between PKM2 and NQO1 in breast cancer continues, however, to be unclear. In the present study, according to UALCAN and GEPIA database, the mRNA levels of PKM2 and NQO1 in breast primary tumor were significantly higher compared to normal breast tissue. Consonant with these findings, increased expression of both PKM2 and NQO1 were detected in clinical samples and BC cell lines. More importantly, consolidated high expression of NQO1 and PKM2 were obtained to be related with worse clinical stage, relapse, shorter relapse free survival (RFS), and poorer overall survival (OS) in human breast cancer. We subsequently found that knockdown of NQO1 reduced the protein level of PKM2 significantly. Moreover, deletion of PKM2 significantly reduced colony formation, migration and invasion of BC cells. A positive correlation between PKM2 and NQO1 expression was identified by immunohistochemical analyses of 108 specimens of breast cancer patients (rs = 0.60, P = 0.00). Finally, endogenous Co-IP demonstrated that PKM2 and NQO1 interact in breast cancer cells. The results of this study suggest that the correlation between NQO1 and PKM2 might play a critical role during breast tumourigenesis and serve as novel diagnostic biomarkers for breast cancer.

Efficacy and mechanism of combination of oxaliplatin with PKM2 knockdown in colorectal cancer

M2 isomer of pyruvate kinase (PKM2), a key enzyme in aerobic glycolysis, is closely related to cancer development and progression. Suppression of PKM2 exhibits synergistic effects with docetaxel in lung cancer, but the therapeutic potential in colorectal cancer (CRC) is unclear. The aim of the present study was to explore the synergic effects and mechanism of knocking down PKM2 combined with oxaliplatin (a chemosensitizer) treatment in two CRC cell lines (HCT116 and DLD1). The PKM2 gene was initially knocked down using small interfering (si)RNAs (si155 and si156). Subsequently, the effects of PKM2-siRNAs and oxaliplatin, on CRC cells were determined using MTS, cell cycle analysis and apoptosis assays. The mechanism of targeting PKM2 was explored by detecting glucose uptake, lactate secretion fluxes, and the levels of glucose-6-phosphate dehydrogenase (G6PD) mRNA, glutathione (GSH) and reactive oxygen species (ROS). Cell viability in the experimental groups (PKM2-siRNAs, oxaliplatin, PKM2-siRNAs + oxaliplatin) was significantly reduced compared with the control group, and combination treatments (PKM2-siRNAs + oxaliplatin) were more effective than single treatments (PKM2-siRNAs and oxaliplatin only groups). Similar results were observed with the apoptosis assay. The combination groups showed synergistic effects compared with both single treatment groups. Furthermore, glucose uptake and lactate secretion and mRNA levels of G6PD and PKM2 were decreased after PKM2 knockdown in the PKM2-siRNAs and PKM2-siRNAs + oxaliplatin groups. The GSH levels in the PKM2-siRNAs group was significantly lower compared with the negative control group. The ROS levels in the PKM2-siRNAs groups were also significantly increased. The combination of PKM2-siRNAs and oxaliplatin had synergistic effects on CRC cells (HCT116 and DLD1). PKM2 silencing may alter energy metabolism in cancer cells and initiate ROS-induced apoptosis after downregulation of the pentose phosphate pathway by PKM2-siRNAs.

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.

Expression of tumor pyruvate kinase M2 isoform in plasma and stool of patients with colorectal cancer or adenomatous polyps

Background

Tumor pyruvate kinase M2 isoform (tM2-PK), which is an isoform of PK-glycolytic enzyme and appears on the surface of cancerous proliferating cells, has been used as a diagnostic biomarker for colorectal cancer (CRC). The aim of this study was to evaluate the tM2-PK measurement test for the diagnosis of CRCs and adenomatous polyps in plasma and stool samples in an Iranian population.

Methods

In this prospective study, a total of 226 stool and 178 plasma samples were received from patients referred to colonoscopy units. tM2-PK enzyme was measured using two separate ScheBo-Biotech-AG ELISA kits for stool and plasma samples.

Results

According to ROC curves, in the tumor group, at the cut-off value of 4 U/ml, the sensitivity of fecal tM2-PK test was 100% and the specificity was 68%, and in the polyp group, the sensitivity and specificity were 87 and 68%, respectively. For tumor detection in plasma specimens, a cut-off value > 25 U/ml has a sensitivity and specificity of 90.9 and 91.3%, respectively. Similarly, for polyp detection, a cut-off value > 19 U/ml has a sensitivity of 96.3% and the specificity of 85.5%.

Conclusions

Based on our results, a cut-off range of 4.8–8 U/ml and >  8 U/ml could be used to detect polyp and tumor in stool samples, respectively. Similarly, a cut-off range of 19–25 U/ml and > 25 U/ml is recommended in plasma samples, suggesting tM2-PK test as a non-invasive assay to diagnose CRC and adenomatous polyps.

Expression pattern of placenta specific 8 and keratin 20 in different types of gastrointestinal cancer

The aim of the present study was to investigate the expression of keratin 20 (KRT20) and placenta specific 8 (PLAC8) in gastrointestinal (GI) cancer with various differentiation phenotypes. The present study retrospectively investigated archived formalin-fixed paraffin-embedded tissue samples from 12 patients at different stages of GI cancer [four with gastric cancer, four with pancreatic cancer and four with colorectal cancer (CRC)]. The stages were pre-determined, according to differentiation phenotypes, by a pathologist of the Department of Pathology at Sijhih Cathay General Hospital. KRT20 and PLAC8 expression levels were assessed using immunohistochemistry. The CRC cell lines SW620 and Caco-2 were used to assess interactions between KRT20 and PLAC8 via reverse transcription-quantitative PCR. PLAC8 and KRT20 expression was observed consistently only in the well-differentiated CRC tissue samples. Low KRT20 expression levels were observed in the PLAC8 knockdown SW620 cells. In addition, there was a positive association between PLAC8 and KRT20 expression in the differentiated Caco-2 cells. According to the results of the present study, the differentiation status of GI cancer influenced KRT20 expression, particularly in CRC, which may explain why patients with well-differentiated CRC display better clinical outcomes. Therefore, the prognostic significance of KRT20 and PLAC8 may be particularly crucial for patients with CRC displaying a well-differentiated phenotype.

Allicin alleviates lead-induced hematopoietic stem cell aging by up-regulating PKM2

Hematopoietic stem cells (HSCs) aging is associated with hematopoietic dysfunction and diseases. Our previous study showed that lead exposure induced a functional decline in HSCs. Allicin, a chemical extracted from the garlic (Allium sativum L.), has been reported to have antioxidative and anti-inflammatory effects. However, the biological activities of allicin on lead-induced toxicity, especially in the hematopoietic system, remain unclear. Here, we found that lead exposure elicited aging phenotypes in HSCs, including perturbed cell quiescence, disabled self-renewal function and colony-forming ability, and myeloid-biased differentiation, all of which contributed to significant hematopoietic disorders in mice. Intragastric administration of allicin substantially ameliorated lead-induced HSCs aging phenotypes in vivo. Lead exposure induced a peroxide condition in HSCs leading to DNA damage, which reduced expression of the glycolytic enzyme pyruvate kinase M2 isoform (PKM2), a phenotype which was significantly ameliorated by allicin treatment. These findings suggested that allicin alleviated lead-induced HSCs aging by up-regulating PKM2 expression; thus, it could be a natural herb for preventing lead toxicity.

PKM2, function and expression and regulation

Pyruvate kinase (PK), as one of the key enzymes for glycolysis, can encode four different subtypes from two groups of genes, although the M2 subtype PKM2 is expressed mainly during embryonic development in normal humans, and is closely related to tissue repair and regeneration, with the deepening of research, the role of PKM2 in tumor tissue has received increasing attention. PKM2 can be aggregated into tetrameric and dimeric forms, PKM2 in the dimer state can enter the nuclear to regulate gene expression, the transformation between them can play an important role in tumor cell energy supply, epithelial-mesenchymal transition (EMT), invasion and metastasis and cell proliferation. We will use the switching effect of PKM2 in glucose metabolism as the entry point to expand and enrich the Warburg effect. In addition, PKM2 can also regulate each other with various proteins by phosphorylation, acetylation and other modifications, mediate the different intracellular localization of PKM2 and then exert specific biological functions. In this paper, we will illustrate each of these points.

Pyruvate kinase M2: A multifarious enzyme in non-canonical localization to promote cancer progression

Rewiring glucose metabolism, termed as Warburg effect or aerobic glycolysis, is a common signature of cancer cells to meet their high energetic and biosynthetic demands of rapid growth and proliferation. Pyruvate kinase M2 isoform (PKM2) is a key player in such metabolic reshuffle, which functions as a rate-limiting glycolytic enzyme in the cytosol of highly-proliferative cancer cells. During the recent decades, PKM2 has been extensively studied in non-canonical localizations such as nucleus, mitochondria, and extracellular secretion, and pertained to novel biological functions in tumor progression. Such functions of PKM2 open a new avenue for cancer researchers. This review summarizes up-to-date functions of PKM2 at various subcellular localizations of cancer cells and draws attention to the translocation of PKM2 from cytosol into the nucleus induced by posttranslational modifications. Moreover, PKM2 in tumor cells could have an important role in resistance acquisition processes against various chemotherapeutic drugs, which have raised a concern on PKM2 as a potential therapeutic target. Finally, we summarize the current status and future perspectives to improve the potential of PKM2 as a therapeutic target for the development of anticancer therapeutic strategies.

High PKM2 expression is independently correlated with decreased overall survival in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal and malignant types of cancer that affects global human health. The present study aimed to investigate the effect of pyruvate kinase muscle isozyme M2 (PKM2) expression on the clinical features and prognosis of HCC. The present study employed univariate logistic regression to investigate the correlation between PKM2 expression and clinical features. Univariate and multivariate Cox regression analyses were performed to estimate the independent effect of PKM2 expression on survival status. The results revealed that patients in the high PKM2 group (≥11.25) exhibited significantly lower creatinine levels (P=0.043), higher fetoprotein levels (P<0.001), advanced stage (P<0.001) and higher grade (P=0.004) compared with patients with low PKM2 expression levels (<11.25). In addition, patients with high PKM2 expression exhibited poor prognosis compared with patients with low PKM2 expression. After correcting the covariates, PKM2 expression remains significantly associated with reduced overall survival (P<0.05). These findings suggested that PKM2 is an independent risk factor for HCC and provides valuable information for future studies on the pathogenesis of HCC and drug discovery.

Editor’s Pick: Pyruvate Kinase and Gastric Cancer: A Potential Marker

Gastric cancer is the second most common cause of cancer-related deaths worldwide, and the 5-year overall survival rate for advanced gastric cancer is ≤25%. Metabolism is a critical process for maintaining growth and other functions in cancer cells; in these cells, the metabolic process shifts from oxidative phosphorylation to aerobic glycolysis and the expression of pyruvate kinase (PK) splice isoform M2 (PKM2) is upregulated. A PubMed search focussing on PK in gastric cancer was conducted and 32 articles were initially collected; 12 articles were subsequently excluded from this review. PKM2 is responsible for tumour growth and invasion and correlates with short survival times and cancer differentiation. Pyruvate dehydrogenase kinase 1 is associated with cell proliferation, lymph node metastasis, and invasion. Measurement of PKM2 or pyruvate dehydrogenase kinase 1 in the blood or stools could be a good marker for gastric cancer in combination with the glycoprotein CA72-4. The review arose from the need for new biomarkers in the management of gastric cancer and had the primary objective of determining whether PK could be used as a marker to diagnose and monitor gastric cancer.

miR-4417 Targets Tripartite Motif-Containing 35 (TRIM35) and Regulates Pyruvate Kinase Muscle 2 (PKM2) Phosphorylation to Promote Proliferation and Suppress Apoptosis in Hepatocellular Carcinoma Cells

BACKGROUND MicroRNAs (miRNAs) are a class of small non-coding RNAs that are strongly involved in various types of carcinogenesis, including hepatocellular carcinoma (HCC). This study aimed to clarify whether miR-4417 promotes HCC growth by targeting TRIM35 and regulating PKM2 phosphorylation. MATERIAL AND METHODS Online software, including TargetScan and miRanda, was used to predict the potential target of miR-4417. Real-Time PCR (qRT-PCR) and Western blot assays were performed to detect the expression levels of mRNA and protein, respectively. Cell proliferation was measured by MTT assay and apoptosis in A549 cells was examined by flow cytometry. RESULTS Bioinformatics reveal that TRIM35 mRNA contains 1 conserved target site of miR-4417. High level of miR-4417 and low levels of TRIM35 mRNA and protein were observed in HCC cells compared with a normal liver cell line. Biological function analysis showed that miR-4417 inhibitor inhibits cell proliferation and promotes apoptosis in HCC cells. Furthermore, we verified that TRIM35 is a functional target of miR-4417 by use of luciferase reporter assay, and TRIM35 overexpressing showed an elevation of proliferation and a reduction of apoptosis in HCC cells. We subsequently investigated whether miR-4417 and TRIM35 regulate HCC cell proliferation and apoptosis through PKM2 Y105 phosphorylation, and the results supported our speculation that miR-4417 targets TRIM35 and regulates the Y105 phosphorylation of PKM2 to promote hepatocarcinogenesis. CONCLUSIONS Our findings indicate that miR-4417 may function as an oncogene in HCC and is a potential alternative therapeutic target for this deadly disease.

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

Pancreatic cancer has a 5-year survival rate of less than 4%. Despite advances in diagnostic technology, pancreatic cancer continues to be diagnosed at a late and incurable stage. Accurate biomarkers for early diagnosis and to predict treatment response are urgently needed. Since alteration of glucose metabolism is one of the hallmarks of cancer cells, we proposed that pyruvate kinase type M2 (M2PK) and lactate dehydrogenase A (LDHA) enzymes could represent novel diagnostic markers and potential therapeutic targets in pancreatic cancer. In 266 tissue sections from normal pancreas, pancreatic cystic neoplasms, pancreatic intraepithelial neoplasia (PanIN) and cancer, we evaluated the expression of PKM2, LDHA, Ki-67 and CD8+ by immunohistochemistry and correlated these markers with clinicopathological characteristics and patient survival. PKM2 and LDHA expression was also assessed by Western blot in 10 human pancreatic cancer cell lines. PKM2 expression increased progressively from cyst through PanIN to cancer, whereas LDHA was overexpressed throughout the carcinogenic process. All but one cell line showed high expression of both proteins. Patients with strong PKM2 and LDHA expression had significantly worse survival than those with weak PKM2 and/or LDHA expression (7.0 months vs. 27.9 months, respectively, p = 0.003, log rank test). The expression of both PKM2 and LDHA correlated directly with Ki-67 expression, and inversely with intratumoral CD8+ cell count. PKM2 was significantly overexpressed in poorly differentiated tumours and both PKM2 and LDHA were overexpressed in larger tumours. Multivariable analysis showed that combined expression of PKM2 and LDHA was an independent poor prognostic marker for survival. In conclusion, our results demonstrate a high expression pattern of two major glycolytic enzymes during pancreatic carcinogenesis, with increased expression in aggressive tumours and a significant adverse effect on survival.

Early detection of colorectal cancer: from conventional methods to novel biomarkers

PURPOSE

Colorectal cancer (CRC) is one of the major health problems worldwide and is often diagnosed at late stage. There is growing body of evidence in early detection of this disease with novel screening modalities to reduce compliance and increase specificity of available methods. The aim of current review is to give an overview on currently available screening methods (e.g., fecal occult blood testing (FOBT), flexible sigmoidoscopy, and colonoscopy), with their own merits and disadvantages, and new genetic/epigenetic/protein markers, as novel screening modalities.

RESULT

There are several serum and fecal biomarkers that can predict CRC and polyps. Overall sensitivities for detection by fecal DNA markers ranged from 53 to 87%, while a panel of serum protein markers provides a sensitivity/specificity up to 85% for CRC. In particular, DNA methylation markers (e.g., SEPT9, SFRP2, and ALX4), circulating microRNAs (e.g., microRNA21), SNPs in microRNAs binding site (e.g., rs4596 located within a target region of the predicted miR-518a-5p and miR-527), protein markers (e.g., carcinoembryonic antigen, N-methyltransferase), or microsatellites instability in tumors with deficient mismatch repair of some genes are among the most interesting and promising biomarkers.

CONCLUSION

Increasing evidence supports the use of combined fecal and serum biomarkers with sigmoidoscopy and colonoscopy screening in order to maximize the benefits and reduce the number of false-positive tests and patients undergoing invasive methods, which in turn could overcome the limitations of the current screening methods for early detection of CRC and adenomas.

Determination of faecal inflammatory marker concentration as a noninvasive method of evaluation of pathological activity in children with inflammatory bowel diseases

PURPOSE

The optimization of procedure evaluating the severity of inflammatory bowel diseases (IBD) using non-invasive methods.

PATIENTS/METHODS

One hundred and nine children with IBD hospitalized in gastroenterology ward between 2009 and 2011 participated in the study. Activity of the disease was evaluated in each patient. Concentration of three inflammatory markers: dimeric form of tumor pyruvate kinase (M2-PK), calprotectin and lactoferrin was evaluated using immunoenzymatic tests.

RESULTS

Existence of a significant correlation between the faecal level of all tested markers and the stage of clinical activity of the disease was demonstrated in children with IBD, both in Crohn's disease (M2-PK p<0.01; calprotectin p=0.005; lactoferrin p<0.01) and in ulcerative colitis group (M2-PK p<0.01; calprotectin p=0.004; lactoferrin p<0.01). A significant difference in the level of markers was found between children with unclassified colitis and the group of patients with ulcerative colitis and Crohn's disease, but there was no difference between Crohn's disease and ulcerative colitis. The increase in the level of one marker correlated with increasing level of other markers (p<0.01). Faecal markers seem to correlate well with majority of indicators of inflammatory condition in blood.

CONCLUSIONS

Measuring M2-PK, lactoferrin and calprotectin levels in faeces seem to be a useful indicator of the level of disease activity in children with IBD.

The Diagnostic Accuracy of the M2 Pyruvate Kinase Quick Stool Test--A Rapid Office Based Assay Test for the Detection of Colorectal Cancer

Background

M2 pyruvate kinase (M2PK) is an oncoprotein secreted by colorectal cancers in stools. This the first report on the accuracy of a rapid stool test in the detection of colorectal cancer (CRC).

Objective

To determine the sensitivity, specificity and positive and negative predictive value of a rapid, point of care stool test M2 PK- the M2PK Quick.

Methods

Consecutive cases of endoscopically diagnosed and histological proven CRC were recruited. Stools were collected by patients and tested with the immunochromatographic M2PK Quick Test (Schebo Biotech AC, Giessen, Germany). Controls were consecutively chosen from patients without any significant colorectal or gastrointestinal disease undergoing colonoscopy. CRC was staged according to the AJCC staging manual (7^th Edition) and location of tumor defined as proximal or distal.

Results

The sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy were: 93%, 97.5%, 94.9%, 96.5% and 96.0% respectively. The positive predictive value for proximal tumors was significantly lower compared to distal tumors. No differences were seen between the different stages of the tumor.

Conclusions

The M2-PK Quick, rapid, point-of-care test is a highly accurate test in the detection of CRC. It is easy and convenient to perform and a useful diagnostic test for the detection of CRC in a clinical practice setting.

Comparative effectiveness of pyruvate kinase M2 in bile, serum carbohydrate antigen 19-9, and biliary brushings in diagnosing malignant biliary strictures

BACKGROUND

The role of M2-PK (pyruvate kinase) in bile has not been studied in comparison with brushings and carbohydrate antigen (CA) 19-9 in the diagnosis of malignant biliary strictures.

AIM

To compare the diagnostic accuracy of biliary M2-PK with cytology and serum CA 19-9 METHODS: In this prospective cross-sectional study, bile was aspirated in 74 patients (discovery and validation cohort) undergoing endoscopic retrograde cholangiopancreatography. Levels of M2-PK were measured in bile and compared to brushings for cytology and CA 19-9.

RESULTS

In the discovery cohort, the median bile M2-PK levels were significantly elevated in patients with malignant biliary strictures [187.9 U/l (interquartile range (IQR) 3.5, 3626.8)] compared to those with benign biliary conditions and primary sclerosing cholangitis [0 U/l (IQR 0, 15)] (P = 0.007). A M2-PK cutoff value of 109.1 U/l distinguished malignant from benign conditions with a sensitivity and specificity of 52.9 and 94.1 %, respectively, and area under curve (AUC) of 0.77. The sensitivity of CA 19-9 and brushings in diagnosing cancer was 52.9 % and 11.1 % and specificity 94.1 and 100 %, respectively. The presence of elevated M2-PK >109.1 U/l or CA 19-9 >33 U/ml or positive brushing was 88.2 % sensitive and 88.2 % specific, AUC of 0.89 in the diagnosis of malignancy. The diagnostic accuracy was confirmed in the validation cohort.

CONCLUSIONS

As a stand-alone factor, none of the markers were able to distinguish benign from malignant biliary strictures with a high sensitivity. However, a combination was highly sensitive in diagnosing malignant biliary strictures.

In silico screening, genotyping, molecular dynamics simulation and activity studies of SNPs in pyruvate kinase M2

Role of, 29-non-synonymous, 15-intronic, 3-close to UTR, single nucleotide polymorphisms (SNPs) and 2 mutations of Human Pyruvate Kinase (PK) M2 were investigated by in-silico and in-vitro functional studies. Prediction of deleterious substitutions based on sequence homology and structure based servers, SIFT, PANTHER, SNPs&GO, PhD-SNP, SNAP and PolyPhen, depicted that 19% emerged common between all the mentioned programs. SNPeffect and HOPE showed three substitutions (C31F, Q310P and S437Y) in-silico as deleterious and functionally important. In-vitro activity assays showed C31F and S437Y variants of PKM2 with reduced activity, while Q310P variant was catalytically inactive. The allosteric activation due to binding of fructose 1-6 bisphosphate (FBP) was compromised in case of S437Y nsSNP variant protein. This was corroborated through molecular dynamics (MD) simulation study, which was also carried out in other two variant proteins. The 5 intronic SNPs of PKM2, associated with sporadic breast cancer in a case-control study, when subjected to different computational analyses, indicated that 3 SNPs (rs2856929, rs8192381 and rs8192431) could generate an alternative transcript by influencing splicing factor binding to PKM2. We propose that these, potentially functional and important variations, both within exons and introns, could have a bearing on cancer metabolism, since PKM2 has been implicated in cancer in the recent past.

Co-expression of PKM2 and TRIM35 predicts survival and recurrence in hepatocellular carcinoma

The identification of prognostic markers for hepatocellular carcinoma (HCC) is needed for clinical practice. Tripartite motif-containing 35 (TRIM35) is a tumor suppressor of HCC. TRIM35 inhibits phosphorylation of pyruvate kinase isoform M2 (PKM2), which is involved in aerobic glycolysis of cancer cells. We found that expression of PKM2 was significantly increased in HCC tissues. This overexpression of PKM2 was correlated with a high TNM stage and level of vascular invasion. Patients with HCC who were positive for PKM2 expression and negative for TRIM35 expression had shorter overall survival and time to recurrence than patients who were negative for PKM2 and positive for TRIM35. Furthermore, PKM2/TRIM35 combination was an independent and significant risk factor for recurrence and survival. In conclusion, PKM2 (+) and TRIM35 (-) contribute to the aggressiveness and poor prognosis of HCC. PKM2/TRIM35 expression could be a biomarker for the prognosis of HCC and target for cancer therapy.

The multifaceted regulation and functions of PKM2 in tumor progression

Tumor cells undergo metabolic rewiring from oxidative phosphorylation towards aerobic glycolysis to maintain the increased anabolic requirements for cell proliferation. It is widely accepted that specific expression of the M2 type pyruvate kinase (PKM2) in tumor cells contributes to this aerobic glycolysis phenotype. To date, researchers have uncovered myriad forms of functional regulation for PKM2, which confers a growth advantage on the tumor cells to enable them to adapt to various microenvironmental signals. Here the richness of our understanding on the modulations and functions of PKM2 in tumor progression is reviewed, and some new insights into the paradoxical expression and functional differences of PKM2 in distinct cancer types are offered.

Changes in pyruvate metabolism detected by magnetic resonance imaging are linked to DNA damage and serve as a sensor of temozolomide response in glioblastoma cells

Recent findings show that exposure to temozolomide (TMZ), a DNA-damaging drug used to treat glioblastoma (GBM), can suppress the conversion of pyruvate to lactate. To understand the mechanistic basis for this effect and its potential utility as a TMZ response biomarker, we compared the response of isogenic GBM cell populations differing only in expression of the DNA repair protein methyltransferase (MGMT), a TMZ-sensitivity determinant, after exposure to TMZ in vitro and in vivo. Hyperpolarized [1-((13))C]-pyruvate-based MRI was used to monitor temporal effects on pyruvate metabolism in parallel with DNA-damage responses and tumor cell growth. TMZ exposure decreased conversion of pyruvate to lactate only in MGMT-deficient cells. This effect coincided temporally with TMZ-induced increases in levels of the DNA-damage response protein pChk1. Changes in pyruvate to lactate conversion triggered by TMZ preceded tumor growth suppression and were not associated with changes in levels of NADH or lactate dehydrogenase activity in tumors. Instead, they were associated with a TMZ-induced decrease in the expression and activity of pyruvate kinase PKM2, a glycolytic enzyme that indirectly controls pyruvate metabolism. PKM2 silencing decreased PK activity, intracellular lactate levels, and conversion of pyruvate to lactate in the same manner as TMZ, and Chk1 silencing blocked the TMZ-induced decrease in PKM2 expression. Overall, our findings showed how TMZ-induced DNA damage is linked through PKM2 to changes in pyruvate metabolism, and how these changes can be exploited by MRI methods as an early sensor of TMZ therapeutic response.

Molecular simulation of Tyr105 phosphorylated pyruvate kinase M2 to understand its structure and dynamics

Tyrosine phosphorylation (p-Y105) of pyruvate kinase (PK) M2, in recent years, has been suggested to facilitate Warburg effect and tumor cell growth. However, a comparison of the structural dynamics of the un-phosphorylated, the active, and the phosphorylated-at-Y105, the inactive-states, is not clear. We studied molecular dynamics of the two states to unravel these features, where phosphorylated PKM2 showed a rapid global conformation change in the initial stages of the simulation. The overall simulation identified that the phosphorylation event results in more buried and less flexible PKM2 conformation, as compared to the un-phosphorylated form, resulting in an open and closed conformation of the active site in un-phosphorylated and phosphorylated forms, respectively, due to the movement of B domain. This conformational shift in Y105-phosphorylated-PKM2 (p-Y105-PKM2) with closed active site, responsible for inhibition of PKM2 activity, was an outcome of the bending residues (117-118, 218-219, 296-297, and 301-308) within the loop connecting A and B domains and the presence of helix-loop-helix motif in A domain. The un-phosphorylated PKM2 formed a helix bend (H4) due to less fluctuation of the residue S-100; where the other end of the helix (H4) was connected to the substrate binding pocket. Further, simulation analysis showed that phosphorylation did not affect the FBP binding predominantly. We propose that p-Y105 inhibits the activity of PKM2 without influencing FBP binding directly and not allowing the open binding conformation by influencing G128, S100, G506 and gamma turn, G126 and S127 residues. Phosphorylated PKM2 was also identified to gain the transcriptional factor function which was not the case with un-phosphorylated form. These structurally important residues in PKM2 could have a bearing on cancer metabolism, since PKM2 has been implicated in the promotion of cancer in the recent past.

Pyruvate kinase M2 expression, but not pyruvate kinase activity, is up-regulated in a grade-specific manner in human glioma

Normal tissues express the M1 isoform of pyruvate kinase (PK) that helps generate and funnel pyruvate into the mitochondria for ATP production. Tumors, in contrast, express the less active PKM2 isoform, which limits pyruvate production and spares glycolytic intermediates for the generation of macromolecules needed for proliferation. Although high PKM2 expression and low PK activity are considered defining features of tumors, very little is known about how PKM expression and PK activity change along the continuum from low grade to high grade tumors, and how these changes relate to tumor growth. To address this issue, we measured PKM isoform expression and PK activity in normal brain, neural progenitor cells, and in a series of over 100 astrocytomas ranging from benign grade I pilocytic astrocytomas to highly aggressive grade IV glioblastoma multiforme (GBM). All glioma exhibited comparably reduced levels of PKM1 expression and PK activity relative to normal brain. In contrast, while grade I-III gliomas all had modestly increased levels of PKM2 RNA and protein expression relative to normal brain, GBM, regardless of whether they arose de novo or progressed from lower grade tumors, showed a 3-5 fold further increase in PKM2 RNA and protein expression. Low levels of PKM1 expression and PK activity were important for cell growth as PKM1 over-expression and the accompanying increases in PK activity slowed the growth of GBM cells. The increased expression of PKM2, however, was also important, because shRNA-mediated PKM2 knockdown decreased total PKM2 and the already low levels of PK activity, but paradoxically also limited cell growth in vitro and in vivo. These results show that pyruvate kinase M expression, but not pyruvate kinase activity, is regulated in a grade-specific manner in glioma, but that changes in both PK activity and PKM2 expression contribute to growth of GBM.

Mitochondrial Markers for Cancer: Relevance to Diagnosis, Therapy, and Prognosis and General Understanding of Malignant Disease Mechanisms

Cancer cells display changes that aid them to escape from cell death, sustain their proliferative powers, and shift their metabolism toward glycolytic energy production. Mitochondria are key organelles in many metabolic and biosynthetic pathways, and the adaptation of mitochondrial function has been recognized as crucial to the changes that occur in cancer cells. This paper zooms in on the pathologic evaluation of mitochondrial markers for diagnosing and staging of human cancer and determining the patients’ prognoses.

Improving colorectal cancer management: the potential of proteomics

Colorectal cancer (CRC) is the third most common cancer worldwide. Successful treatment is heavily dependent on tumor stage at the time of detection, but unfortunately CRC is often only detected in advanced stages. New biomarkers in the form of genes or proteins that can be used for diagnosis, prognostication, follow-up, and treatment selection and monitoring could be of great benefit for the management of CRC. Furthermore, proteins could prove valuable new targets for therapy. Therefore, clinical proteomics has gained a lot of scientific interest in this regard. To get an overall insight into the extent to which this research has contributed to a better management of CRC, we give a comprehensive overview of the results of proteomics research on CRC, focusing on expression proteomics, in other words, protein profiling studies. Furthermore, we evaluate the potential of the discriminating proteins identified in this research for clinical use as biomarkers for (early) diagnosis, prognosis and follow-up of CRC or as targets for new therapeutic regimens.

A combination of faecal tests for the detection of colon cancer: a new strategy for an appropriate selection of referrals to colonoscopy? A prospective multicentre Italian study

INTRODUCTION

Colonoscopy workload for endoscopy services in Western countries is increasing markedly because of the implementation of faecal occult blood-based mass screening programmes against colorectal cancer (CRC). We therefore explored the possibility of using a combination of faecal tests to prioritize the access to colonoscopy with criteria other than symptoms and/or time of referral.

AIMS AND METHODS

We tested a combination of faecal tests [immunochemical faecal occult blood test (i-FOBT), M2-PK, calprotectin] as markers for advanced neoplasia in a selected series of patients requiring colonoscopy for the suspicion of CRC. All the tests were performed in a 1-day stool sample of patients aged 50-80 years, without any dietary restriction, before colonoscopy.

RESULTS

A total of 280 patients' stool single samples were analysed. Forty-seven patients had CRC and 85 patients had one or more advanced adenoma(s) at colonoscopy/histology. CRCs were associated with a highly significant increase (P<0.001) in faecal tumour M2-PK (mean 24.2 kU/l), which correlated with Dukes' staging. For CRC detection, i-FOBT was the test with the highest specificity and positive predictive value (0.89 and 0.53), whereas M2-PK had the highest sensitivity and negative predictive value (0.87 and 0.96). Calprotectin showed performance similar to M2-PK in terms of sensitivity and negative predictive value (0.93), but had lower specificity (0.39). The best combination of tests to predict the risk of CRC in this series was i-FOBT+M2-PK, as in patients showing positivity to both markers, the risk of cancer was as high as 79%.

CONCLUSION

The combination of i-FOBT and M2-PK is a sensitive tool in clinical practice for the appropriate management of waiting lists for colonoscopy, as it allows the classification of patients into different degrees of priority for investigation, according to their foreseeable risk of CRC.

Faecal pyruvate kinase isoenzyme type M2 for colorectal cancer screening: A meta-analysis

AIM: To present a critical discussion of the efficacy of the faecal pyruvate kinase isoenzyme type M2 (faecal M2-PK) test for colorectal cancer (CRC) screening based on the currently available studies.

METHODS: A literature search in PubMed and Embase was conducted using the following search terms: fecal Tumor M2-PK, faecal Tumour M2-PK, fecal M2-PK, faecal M2-PK, fecal pyruvate kinase, faecal pyruvate kinase, pyruvate kinase stool and M2-PK stool.

RESULTS: Stool samples from 704 patients with CRC and from 11 412 healthy subjects have been investigated for faecal M2-PK concentrations in seventeen independent studies. The mean faecal M2-PK sensitivity was 80.3%; the specificity was 95.2%. Four studies compared faecal M2-PK head-to-head with guaiac-based faecal occult blood test (gFOBT). Faecal M2-PK demonstrated a sensitivity of 81.1%, whereas the gFOBT detected only 36.9% of the CRCs. Eight independent studies investigated the sensitivity of faecal M2-PK for adenoma (n = 554), with the following sensitivities: adenoma < 1 cm in diameter: 25%; adenoma > 1 cm: 44%; adenoma of unspecified diameter: 51%. In a direct comparison with gFOBT of adenoma > 1 cm in diameter, 47% tested positive with the faecal M2-PK test, whereas the gFOBT detected only 27%.

CONCLUSION: We recommend faecal M2-PK as a routine test for CRC screening. Faecal M2-PK closes a gap in clinical practice because it detects bleeding and non-bleeding tumors and adenoma with high sensitivity and specificity.

Defining the molecular basis of tumor metabolism: a continuing challenge since Warburg's discovery

Cancer cells are the product of genetic disorders that alter crucial intracellular signaling pathways associated with the regulation of cell survival, proliferation, differentiation and death mechanisms. The role of oncogene activation and tumor suppressor inhibition in the onset of cancer is well established. Traditional antitumor therapies target specific molecules, the action/expression of which is altered in cancer cells. However, since the physiology of normal cells involves the same signaling pathways that are disturbed in cancer cells, targeted therapies have to deal with side effects and multidrug resistance, the main causes of therapy failure. Since the pioneering work of Otto Warburg, over 80 years ago, the subversion of normal metabolism displayed by cancer cells has been highlighted by many studies. Recently, the study of tumor metabolism has received much attention because metabolic transformation is a crucial cancer hallmark and a direct consequence of disturbances in the activities of oncogenes and tumor suppressors. In this review we discuss tumor metabolism from the molecular perspective of oncogenes, tumor suppressors and protein signaling pathways relevant to metabolic transformation and tumorigenesis. We also identify the principal unanswered questions surrounding this issue and the attempts to relate these to their potential for future cancer treatment. As will be made clear, tumor metabolism is still only partly understood and the metabolic aspects of transformation constitute a major challenge for science. Nevertheless, cancer metabolism can be exploited to devise novel avenues for the rational treatment of this disease.

Clinical significance of serum levels of tumor type M2-pyruvate kinase and heat shock protein 90α in patients with gastric cancer

AIM: To measure serum levels of tumor type M2 pyruvate kinase (M2-PK) and heat shock protein 90α (HSP90α) in patients with gastric cancer and to evaluate their clinical significance by comparing to serum carcinoembryonic antigen (CEA).

METHODS: A total of 80 patients with gastric cancer and 80 controls were enrolled in this study. Serum levels of M2-PK and HSP90α were measured by ELISA, while those of CEA were determined by radioimmunoassay.

RESULTS: Serum levels of M2-PK, HSP90α and CEA were significantly higher in patients with gastric cancer than in controls (all P < 0.05). The sensitivity and specificity of detection of M2-PK, HSP90α and CEA were 56.25% and 91.25%, 52.50% and 92.50%, and 45.00% and 92.50% respectively. Compared to detection of HSP90α and CEA alone, detection of M2-PK had a higher sensitivity. The sensitivity of combined detection of M2-PK, HSP90α and CEA was increased to 91.25%. Serum M2-PK was positively correlated with tumor size, TNM stage, invasion depth and lymph node metastasis (all P < 0.05). A significant positive correlation was noted between serum M2-PK and HSP90α levels in patients with gastric cancer.

CONCLUSION: Serum M2-PK and HSP90α can be used as potential markers for gastric cancer. There is a strong positive correlation between serum M2-PK and HSP90α levels in patients with gastric cancer.

Upregulation of plasma C9 protein in gastric cancer patients

Gastric cancer is one of the leading causes of cancer-related deaths worldwide. Current biomarkers used in the clinic do not have sufficient sensitivity for gastric cancer detection. To discover new and better biomarkers, protein profiling on plasma samples from 25 normal, 15 early-stage and 21 late-stage cancer was performed using an iTRAQ-LC-MS/MS approach. The level of C9 protein was found to be significantly higher in gastric cancer compared with normal subjects. Immunoblotting data revealed a congruent trend with iTRAQ results. The discriminatory power of C9 between normal and cancer states was not due to inter-patient variations and was independent from gastritis and Helicobacter pylori status of the patients. C9 overexpression could also be detected in a panel of gastric cancer cell lines and their conditioned media compared with normal cells, implying that higher C9 levels in plasma of cancer patients could be attributed to the presence of gastric tumor. A subsequent blind test study on a total of 119 plasma samples showed that the sensitivity of C9 could be as high as 90% at a specificity of 74%. Hence, C9 is a potentially useful biomarker for gastric cancer detection.

B16 melanoma secretomes and in vitro invasiveness: syntenin as an invasion modulator

To characterize proteins involved in melanoma dissemination, protein profiles from B16F10 and B16Bl6 cells were compared, as only B16Bl6 cells give pulmonary metastases after subcutaneous graft. As B16F10 and B16Bl6 cells had the same invasive capacities in vitro, we wondered whether their extracellular content could be different and correlate with their metastatic properties. We have shown that B16F10 and B16Bl6 culture cell supernatants have different modulatory effects on HT1080 fibrosarcoma cell invasion in Matrigel-coated chambers. B16Bl6 supernatants significantly enhanced HT1080 in vitro invasion as compared with B16F10 ones, suggesting differences in their protein profiles. Indeed, proteomic analysis allowed the identification of 18 differential proteins. Among the proteins with a higher concentration in B16Bl6 supernanants, lactate dehydrogenase B, M2 pyruvate kinase, cathepsin D, and galectin 1 were involved in the melanoma aggressiveness signature. Interestingly, several Gag retroviral proteins, as well as syntenin, were found mainly in the B16F10 secretome. Although its intracellular form is known as an aggressive melanoma marker, we show for the first time that syntenin was actively secreted and could reduce the invasion process, probably by protein interactions in the B16 model.

Multiplex N-terminome analysis of MMP-2 and MMP-9 substrate degradomes by iTRAQ-TAILS quantitative proteomics

Proteolysis is a major protein posttranslational modification that, by altering protein structure, affects protein function and, by truncating the protein sequence, alters peptide signatures of proteins analyzed by proteomics. To identify such modified and shortened protease-generated neo-N-termini on a proteome-wide basis, we developed a whole protein isobaric tag for relative and absolute quantitation (iTRAQ) labeling method that simultaneously labels and blocks all primary amines including protein N- termini and lysine side chains. Blocking lysines limits trypsin cleavage to arginine, which effectively elongates the proteolytically truncated peptides for improved MS/MS analysis and peptide identification. Incorporating iTRAQ whole protein labeling with terminal amine isotopic labeling of substrates (iTRAQ-TAILS) to enrich the N-terminome by negative selection of the blocked mature original N-termini and neo-N-termini has many advantages. It enables simultaneous characterization of the natural N-termini of proteins, their N-terminal modifications, and proteolysis product and cleavage site identification. Furthermore, iTRAQ-TAILS also enables multiplex N-terminomics analysis of up to eight samples and allows for quantification in MS2 mode, thus preventing an increase in spectral complexity and extending proteome coverage by signal amplification of low abundance proteins. We compared the substrate degradomes of two closely related matrix metalloproteinases, MMP-2 (gelatinase A) and MMP-9 (gelatinase B), in fibroblast secreted proteins. Among 3,152 unique N-terminal peptides identified corresponding to 1,054 proteins, we detected 201 cleavage products for MMP-2 and unexpectedly only 19 for the homologous MMP-9 under identical conditions. Novel substrates identified and biochemically validated include insulin-like growth factor binding protein-4, complement C1r component A, galectin-1, dickkopf-related protein-3, and thrombospondin-2. Hence, N-terminomics analyses using iTRAQ-TAILS links gelatinases with new mechanisms of action in angiogenesis and reveals unpredicted restrictions in substrate repertoires for these two very similar proteases.

In vivo factors influencing tumour M2-pyruvate kinase level in human pancreatic cancer cell lines

In tumour cells, the tetramer/dimer ratio of the pyruvate kinase isoenzyme type M2 (M2-PK) determines whether glucose carbons are degraded to lactate with production of energy (tetrameric form) or are channelled into synthetic processes (dimeric form). The influence of different tumour microenvironment conditions on the tetramer/dimer ratio of M2-PK and cell doublings were investigated in a non-metastatic and metastatic pancreatic cancer cell line. The metastatic Colo357 cells contained about fourfold more M2-PK protein and about 3.5-fold more dimeric M2-PK than the non-metastatic Panc-1 cells. In Colo357 cells hypoxia, glucose starvation as well as acidification induced an increase of the dimeric form of M2-PK, whereas in Panc-1 cells no effect on M2-PK was observed. Under hypoxia in Colo357 cells, the dimerization and inactivation of M2-PK results in an inhibition of cell proliferation, whereas under glucose starvation and acidification the dimerization of M2-PK allowed further cell doublings. M2-PK expression and the quaternary structure of M2-PK are influenced by the tumour metastatic potential. The quaternary structure of M2-PK may be differently affected by hypoxia, glucose starvation and acidification with severe consequences on cell doublings.

Tyrosine phosphorylation inhibits PKM2 to promote the Warburg effect and tumor growth

The Warburg effect describes a pro-oncogenic metabolism switch such that cancer cells take up more glucose than normal tissue and favor incomplete oxidation of glucose even in the presence of oxygen. To better understand how tyrosine kinase signaling, which is commonly increased in tumors, regulates the Warburg effect, we performed phosphoproteomic studies. We found that oncogenic forms of fibroblast growth factor receptor type 1 inhibit the pyruvate kinase M2 (PKM2) isoform by direct phosphorylation of PKM2 tyrosine residue 105 (Y(105)). This inhibits the formation of active, tetrameric PKM2 by disrupting binding of the PKM2 cofactor fructose-1,6-bisphosphate. Furthermore, we found that phosphorylation of PKM2 Y(105) is common in human cancers. The presence of a PKM2 mutant in which phenylalanine is substituted for Y(105) (Y105F) in cancer cells leads to decreased cell proliferation under hypoxic conditions, increased oxidative phosphorylation with reduced lactate production, and reduced tumor growth in xenografts in nude mice. Our findings suggest that tyrosine phosphorylation regulates PKM2 to provide a metabolic advantage to tumor cells, thereby promoting tumor growth.

Genome-wide profile of pleural mesothelioma versus parietal and visceral pleura: the emerging gene portrait of the mesothelioma phenotype

BACKGROUND

Malignant pleural mesothelioma is considered an almost incurable tumour with increasing incidence worldwide. It usually develops in the parietal pleura, from mesothelial lining or submesothelial cells, subsequently invading the visceral pleura. Chromosomal and genomic aberrations of mesothelioma are diverse and heterogenous. Genome-wide profiling of mesothelioma versus parietal and visceral normal pleural tissue could thus reveal novel genes and pathways explaining its aggressive phenotype.

METHODOLOGY AND PRINCIPAL FINDINGS

Well-characterised tissue from five mesothelioma patients and normal parietal and visceral pleural samples from six non-cancer patients were profiled by Affymetrix oligoarray of 38 500 genes. The lists of differentially expressed genes tested for overrepresentation in KEGG PATHWAYS (Kyoto Encyclopedia of Genes and Genomes) and GO (gene ontology) terms revealed large differences of expression between visceral and parietal pleura, and both tissues differed from mesothelioma. Cell growth and intrinsic resistance in tumour versus parietal pleura was reflected in highly overexpressed cell cycle, mitosis, replication, DNA repair and anti-apoptosis genes. Several genes of the "salvage pathway" that recycle nucleobases were overexpressed, among them TYMS, encoding thymidylate synthase, the main target of the antifolate drug pemetrexed that is active in mesothelioma. Circadian rhythm genes were expressed in favour of tumour growth. The local invasive, non-metastatic phenotype of mesothelioma, could partly be due to overexpression of the known metastasis suppressors NME1 and NME2. Down-regulation of several tumour suppressor genes could contribute to mesothelioma progression. Genes involved in cell communication were down-regulated, indicating that mesothelioma may shield itself from the immune system. Similarly, in non-cancer parietal versus visceral pleura signal transduction, soluble transporter and adhesion genes were down-regulated. This could represent a genetical platform of the parietal pleura propensity to develop mesothelioma.

CONCLUSIONS

Genome-wide microarray approach using complex human tissue samples revealed novel expression patterns, reflecting some important features of mesothelioma biology that should be further explored.

Systemic inflammatory response syndrome after percutaneous nephrolithotomy: an assessment of risk factors

OBJECTIVES

To analyze the risk factors for systemic inflammatory response syndrome (SIRS) after percutaneous nephrolithotomy (PCNL) and to quantitatively predict the probability of SIRS after PCNL.

METHODS

Medical records on 209 patients who underwent PCNL were retrospectively analyzed. The chi2 test, the t-test and a logistic regression model were used to identify key risk factors of SIRS after PCNL. A predictive equation was then formulated to assess the risk of SIRS according to the results from the logistic model. Subsequently, the accuracy of the equation by calculating sensitivity, specificity, overall correct percentage, and positive and negative predictive values was tested.

RESULTS

The incidence of SIRS after PCNL was 23.4%. The key risk factors for SIRS following PCNL were: the number of tracts, receipt of a blood transfusion, stone size, and presence of pyelocaliectasis. Other factors added no independent risk to the development of SIRS. The calculated values for sensitivity, specificity, overall percentage correct, positive predictive value and negative predictive value were 44.9%, 95.0%, 83.3%, 73.3%, and 84.9%, respectively.

CONCLUSIONS

Number of tracts, receipt of a blood transfusion, stone size and presence of pyelocaliectasis are identified as the key risk factors for SIRS after PCNL. The predictive equation allows for an individualized and quantitative assessment of the probability of SIRS after PCNL.

Tumor M2 pyruvate kinase: a tumor marker and its clinical application in gastrointestinal malignancy

Proliferating cells, in particular tumor cells, express a dimeric isoenzyme of pyruvate kinase, termed Tumor M2 pyruvate kinase. In the last few years, much attention has been paid to this novel tumor marker that can be determined in EDTA-plasma and in the feces. It has been used in diagnosis and surveillance of a variety of malignant diseases. As compared with the established tumor markers, Tumor M2-PK in EDTA-plasma proves to have at least equal sensitivity in pancreatic, gastric, esophageal, colorectal and cholangiocellular cancer. In combination with established tumor markers, EDTA-plasma M2-PK is a useful tool in diagnosis and surveillance of gastrointestinal tumors. In colorectal cancer, M2-PK in EDTA-plasma even proves superiority as compared with CEA. Fecal Tumor M2-PK testing resembles a good noninvasive screening parameter for colorectal cancer with a reported sensitivity of 68.8-91.0% and a specificity of 71.9-100%. It is superior to fecal occult blood testing in colorectal cancer screening. Since it is effective, easy to handle and bears rather low costs, fecal Tumor M2-PK testing is recommended for large-scale CRC screening.

A comparison of tumour M2-PK with carcinoembryonic antigen and CA19-9 in patients undergoing liver resection for colorectal metastases

BACKGROUND

The currently available tumour markers used in the management of patients with colorectal metastases are of limited value. Tumour M2-pyruvate kinase (TuM2-PK), a tumour-associated isoenzyme of pyruvate kinase, is elevated in patients with gastrointestinal cancer. This study has measured TuM2-PK levels in patients before and after resection of colorectal liver metastases (CLM).

MATERIALS AND METHODS

Fifty patients with CLM and no local residual disease had TuM2-PK levels measured before liver resection. In 20 patients, TuM2-PK levels were repeated at 2 weeks, 5 weeks and 5 months after resection. Plasma levels were analysed by enzyme-linked immunosorbent assay (ScheBo, Giessen, Germany). Carcinoembryonic antigen (CEA) and CA19-9 levels were measured at the same time periods by electrochemiluminescence immunoassay. CEA, CA19-9 and TuM2-PK levels were compared with the tumour number, volume, differentiation and stage. Cut-off values used for TuM2-PK, CEA and CA19-9 were 15 IU/ml, 10 ng/ml and 39 IU/ml, respectively.

RESULTS

TuM2-PK was elevated in 68%, CEA in 62% and CA19-9 in 40% of patients with CLM. TuM2-PK+CEA was elevated in 88% and TuM2-PK+CA19-9 in 78% of patients. A significant correlation was observed between tumour volume and CEA (r=0.34, P<0.05) and CA19-9 (r=0.49, P<0.005). TuM2-PK levels did not show a significant correlation with tumour differentiation, volume or the number of metastases. At 2 weeks after liver resection, CEA and CA19-9 levels had decreased to normal value in 73 and 67% of patients, respectively, but TuM2-PK remained elevated in all patients. At 5 weeks, TuM2-PK, CEA and CA19-9 levels decreased to normal in 64, 93 and 70% of patients, respectively, and at 5 months levels were normal in 58, 92 and 67%.

CONCLUSION

Plasma TuM2-PK is commonly elevated in patients with CLM. Levels do not correlate with tumour volume, number or differentiation. Levels remain elevated after liver resection, the cause of which requires further investigation.

Extensive analysis of the cytoplasmic proteome of human erythrocytes using the peptide ligand library technology and advanced mass spectrometry

The erythrocyte cytoplasmic proteome is composed of 98% hemoglobin; the remaining 2% is largely unexplored. Here we used a combinatorial library of hexameric peptides as a capturing agent to lower the signal of hemoglobin and amplify the signal of low to very low abundance proteins in the cytoplasm of human red blood cells (RBCs). Two types of hexapeptide library beads have been adopted: amino-terminal hexapeptide beads and beads in which the peptides have been further derivatized by carboxylation. The amplification of the signal of low abundance and suppression of the signal of high abundance species were fully demonstrated by two-dimensional gel maps and nano-LC-MSMS analysis. The effect of this new methodology on quantitative information also was explored. Moreover using this approach on an LTQ-Orbitrap mass spectrometer, we could identify with high confidence as many as 1578 proteins in the cytoplasmic fraction of a highly purified preparation of RBCs, allowing a deep exploration of the classical RBC pathways as well as the identification of unexpected minor proteins. In addition, we were able to detect the presence of eight different hemoglobin chains including embryonic and newly discovered globin chains. Thus, this extensive study provides a huge data set of proteins that are present in the RBC cytoplasm that may help to better understand the biology of this simplified cell and may open the way to further studies on blood pathologies using targeted approaches.

Comparison of an established simple office-based immunological FOBT with fecal tumor pyruvate kinase type M2 (M2-PK) for colorectal cancer screening: prospective multicenter study

OBJECTIVES

The immunological fecal occult blood test (IFOBT) has established itself as a more precise marker for colorectal cancer (CRC) screening than traditional guaiac-based FOBT. The simpler, cheaper, and more convenient newer office-based IFOBTs have been validated for diagnosing CRC. Dimeric isoenzyme of pyruvate kinase, M2-PK, expressed by tumor cells, has as well been proposed as a screening tool for CRC. This is the first study comparing fecal M2-PK as a screening biomarker for CRC against previously evaluated office-based IFOBT and colonoscopy.

METHODS

Six hundred forty consecutive subjects (symptomatic, as well as for CRC screening) referred for colonoscopy for various indications across five centers in Germany provided the stool samples for performing M2-PK and an immunochemical FOB strip test. The IFOBT used was a rapid immunochromatographic assay for detection of fecal hemoglobin. For M2-PK, a commercially available sandwich enzyme-linked immunosorbent assay (ELISA) was used. The M2-PK test needs 6 h, while the office-based test can be read in just 10 min and is five times cheaper.

RESULTS

Office-based IFOBT had sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios (LR) of 64.5, 96.3, 72.0, 94.9, 17.5, and 0.4 for diagnosing colorectal neoplasia (CRN), while the above performance characteristics for M2-PK at a cutoff value of 4 U/mL were 72.4, 73.8, 29.0, 94.8, 2.8, and 0.8 respectively.

CONCLUSIONS

This office-based IFOBT was found to have significantly higher specificity, PPV, and positive LR as compared with M2-PK. IFOBT proved to be a convenient, noncumbersome, quick, and cheap tool in patients with above-average risk for detection of CRN.