Tumor M2-pyruvate kinase as tumor marker in exocrine pancreatic cancer a meta-analysis

OBJECTIVES

Tumor M2-pyruvate kinase, a tumor-associated dimeric form of enzyme pyruvate kinase, is commonly elevated in pancreatic cancers. This meta-analysis aimed to evaluate its diagnostic utility in comparison to carbohydrate antigen 19-9 (CA19-9) in pancreatic cancer.

METHODS

A literature search was conducted for entries from 1951 to 2006 using PubMed, Embase, Central, and SCI Expanded databases using M2 pyruvate kinase AND pancreatic cancer/s OR tumor/s as keywords. A total of 258 references were retrieved. Of these, 118 duplicates were removed and 132 references were excluded. All studies comparing TuM2-PK with CA19-9 in pancreatic cancer were included. Full text was obtained for 8 references of 7 included studies. Diagnostic odds ratio (DOR) and 95% confidence interval (CI) was calculated from the available specificity and sensitivity for each study and were pooled to give overall DOR and 95% CI for TuM2-PK and CA19-9. Receiver operator characteristic curve was calculated to give overall specificity and sensitivity for TuM2-PK.

RESULTS

The diagnostic performance of TuM2-PK (DOR, 35; 95% CI, 19.7-62.3) was similar to those of CA19-9 (DOR, 44; 95% CI, 26.5-73.1). The overall specificity for TuM2-PK was 60% with corresponding sensitivity of 95%.

CONCLUSION

Efficacy of TuM2-PK as a tumor marker is similar to that of CA19-9. Further trials are needed to use it alone or in combination with CA19-9 in patients with suspected pancreatic cancer.

Fecal pyruvate kinase-M2 (tumor M2-PK) measurement: a new screening concept for colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a disease with major impact on public health and public health costs. Colonoscopy is purportedly the best screening tool for CRC. However, the acceptance by the general population is very poor. Therefore evaluation of additional screening tools is of great interest.

PATIENTS AND METHODS

The use of M2-PK measurement in the feces has been reported in 6 studies to date. The data of these studies were analysed and critically reviewed. Additionally, 1,906 persons undergoing routine health care check-up provided stool samples for M2-PK measurement.

RESULTS

The overall sensitivity of M2-PK is 77.9% for CRC. Specificity ranges from 74.3 to 83.3%. Of the 1,906 screened persons, 90.4% had results within the normal range, while 9.6% had elevated results.

CONCLUSION

Measurement of tumor M2-PK in feces seems to be the most promising tool for CRC screening at the present time. In combination with colonoscopy, this test should hence be recommended for CRC screening programs.

Tumour M2-PK as a stool marker for colorectal cancer: comparative analysis in a large sample of unselected older adults vs colorectal cancer patients

Stool testing based on tumour-derived markers might offer a promising approach for non-invasive colorectal cancer (CRC) screening. The aim of this study was to estimate the potential of a new test for faecal tumour M2-PK to discriminate patients with CRC from a large sample of unselected older adults. Faecal tumour M2-PK concentrations were determined in 65 CRC patients and in a population-based sample of 917 older adults (median age: 65 and 62 years, respectively). Sensitivity and specificity of the test were calculated at different cutoff values, and receiver-operating characteristic curves (ROC) were constructed to visualise the discriminatory power of the test. The median (interquartile range) faecal tumour M2-PK concentration was 8.6 U ml⁻¹ (2.8–18.0) among CRC patients and <2 U ml⁻¹ (<2–3.2; P<0.0001) in the population sample. At a cutoff value of 4 U ml⁻¹, sensitivity (95% confidence interval) was 85% (65–96%) for colon cancer and 56% (41–74%) for rectum cancer. Specificity (95% confidence interval) was estimated to be 79% (76–81%). Given the comparatively high sensitivity of the tumour M2-PK stool test (especially for colon cancer) and its simple analysis, the potential use of the test for early detection of CRC merits further investigation. Possibilities to enhance specificity of the test should be explored.

Tumour M2-pyruvate kinase: a gastrointestinal cancer marker

BACKGROUND

Gastrointestinal cancer tumour markers are valuable in the detection of recurrence following resection or in monitoring response to chemotherapy. CEA, CA19-9, CA-50 and CA72-4 are currently available but are nonspecific and have a low sensitivity. 'Tumour M2-pyruvate kinase' was described by Eigenbrodt around 1985. In cancers the active tetrameric form of the M2 isoenzyme of pyruvate kinase converted to an inactive dimeric form by direct interaction with oncoproteins to channel glucose carbons into DNA synthesis. This review summarizes the current knowledge of this unique tumour marker with regard to its biochemistry, assay and potential use as a diagnostic and screening tool in gastrointestinal cancer.

METHODS

A literature search was conducted for entries from 1980 to 2005 using PubMed and NeLH databases using tumour M2-pyruvate kinase, faecal tumour M2-pyruvate kinase, tumour metabolism, tumour markers and carcinoembryonic antigen as keywords. A total of 56 references relevant to tumour M2-pyruvate kinase were retrieved. Eighteen references were clinical studies involving plasma/faecal tumour M2-pyruvate kinase and gastrointestinal cancer. The remaining 38 references were clinical/nonclinical trials and reviews on tumour metabolism and plasma/faecal tumour M2-pyruvate kinase assay. Seven of the 18 clinical studies involved faecal M2-pyruvate kinase. Three of the 11 plasma tumour M2-pyruvate kinase studies were non-English language and were excluded. The sensitivity, specificity, positive predictive and negative predictive value for plasma/serum tumour M2-pyruvate kinase in the detection of gastrointestinal cancer was determined for each of the remaining eight studies. Data for gastrointestinal cancer M2-pyruvate kinase were compared with other gastrointestinal cancer markers. Data from three of the eight studies using a diagnostic cut-off value of 15 U/ml for ethylenediaminetetraacetic acid (EDTA) plasma tumour M2-pyruvate kinase were analysed together as a small meta-analysis.

RESULTS

At a diagnostic cut-off value of 15 U/ml for tumour M2-pyruvate kinase in EDTA plasma the sensitivity, specificity, positive predictive and negative predictive value was 57.3, 89, 85.7 and 64.8%, respectively, for colorectal cancers, 62.1, 89, 88 and 64%, respectively, for gastric/oesophageal cancers and 72.5, 89, 58 and 94%, respectively, for pancreatic cancers. As a faecal marker for colorectal cancers, faecal tumour M2-pyruvate kinase has a sensitivity of 73-92% at a cut-off value of 4 U/ml as against 50% sensitivity for Guaiac faecal test.

CONCLUSION

Circulating tumour M2-pyruvate kinase is more commonly elevated in oesophageal, gastric and colorectal cancer patients than conventional tumour markers. Faecal M2-pyruvate kinase is a sensitive marker of colorectal cancer. The clinical role of tumour M2-pyruvate kinase in gastrointestinal cancer management should be investigated in large-scale clinical trials.

Phosphoenolpyruvate metabolism in Jerusalem artichoke mitochondria

We report here initial studies on phosphoenolpyruvate metabolism in coupled mitochondria isolated from Jerusalem artichoke tubers. It was found that: (1) phosphoenolpyruvate can be metabolized by Jerusalem artichoke mitochondria by virtue of the presence of the mitochondrial pyruvate kinase, shown both immunologically and functionally, located in the inner mitochondrial compartments and distinct from the cytosolic pyruvate kinase as shown by the different pH and inhibition profiles. (2) Jerusalem artichoke mitochondria can take up externally added phosphoenolpyruvate in a proton compensated manner, in a carrier-mediated process which was investigated by measuring fluorimetrically the oxidation of intramitochondrial pyridine nucleotide which occurs as a result of phosphoenolpyruvate uptake and alternative oxidase activation. (3) The addition of phosphoenolpyruvate causes pyruvate and ATP production, as monitored via HPLC, with their efflux into the extramitochondrial phase investigated fluorimetrically. Such an efflux occurs via the putative phosphoenolpyruvate/pyruvate and phosphoenolpyruvate/ATP antiporters, which differ from each other and from the pyruvate and the adenine nucleotide carriers, in the light of the different sensitivity to non-penetrant compounds. These carriers were shown to regulate the rate of efflux of both pyruvate and ATP. The appearance of citrate and oxaloacetate outside mitochondria was also found as a result of phosphoenolpyruvate addition.

[Pilot study on M2-PK-- a new non-invasive parameter for early diagnosis of colorectal carcinoma]

To determine the level of tumor marker pyruvate kinase dimer (M2-PK) in the feces of patients with colorectal cancer and benign polyps, as well as in individuals with chronic inflammatory bowel diseases. Fecal M2-PK determination could be outlined as a highly reliable non-invasive approach to the diagnosis of colorectal carcinoma. The establishing of elevated values in patients with chronic inflammatory bowel diseases decreases the specificity of M2-PK as a tumor marker. However, this does not compromise its essential clinical significance, because the precise diagnosis in both diseases imposes an obligatory performance of colonoscopy.

Colorectal cancer screening by non-invasive metabolic biomarker fecal tumor M2-PK

AIM: To evaluate the utility of the innovative fecal tumor M2-Pyruvate kinase (M2-PK) test in our daily clinical routine, as a marker for the pre-selection of patients who should subsequently undergo colonoscopy for the diagnosis or exclusion of colorectal cancer.

METHODS: Fecal tumor M2-PK was measured in stool samples of 96 study participants (33 patients with colorectal cancer, 21 patients with rectal carcinoma and 42 controls) who all underwent total colonoscopy.

RESULTS: In 39 of 42 individuals in the control group, fecal tumor M2-PK was below 4.0 kU/L (93% specificity). Colorectal tumors were accompanied by a highly significant increase (P < 0.001) in fecal tumor M2-PK levels (median: colon carcinoma, 23.1 kU/L; rectal carcinoma, 6.9 kU/L; colorectal carcinoma, 14.7 kU/L), which correlated with Duke’s staging and T-classification. The overall sensitivity was 78% for colorectal cancer, increasing from 60% for stage T1 to 100% for stage T4 and from 60% for Duke’s A to 90% for Duke’s D tumors.

CONCLUSION: Fecal tumor M2-PK is an appropriately sensitive tool to pre-select those patients requiring colonoscopy for the further diagnostic confirmation or exclusion of colorectal cancer.

Plasmodium falciparum pyruvate kinase as a novel target for antimalarial drug-screening

BACKGROUND

Global travellers are increasingly at risk of contracting malaria. The increasing occurrence of drug-resistance in many endemic areas emphasizes the need for novel drug targets for antimalarial-screening. In this study, the use of pyruvate kinase as a drug-target is evaluated. The functional validation of a gene encoding pyruvate kinase (designated PK1) has previously been reported. However, alternative copies of this enzyme encoded by Plasmodium falciparum could also circumvent the role of PK1. A survey of genome data revealed a putative ORF seemingly coding for another pyruvate kinase (designated PK2).

METHODS

The expression of PK1 and PK2 in in vitro cultures were investigated by RT-PCR. Biocomputational analysis was carried out to identify structural differences between the P. falciparum pyruvate kinases and the corresponding enzymes from its human host.

RESULTS

Both PK1 and PK2 were indeed actively transcribed during the intraerythrocytic stages, suggesting the involvement of both enzymes during infection. A comparison of amino acid residues at the effector binding sites of PK1 and PK2, to those of the human pyruvate kinases revealed some significant differences that could serve as targets for selective inhibitors to be designed against parasitic pyruvate kinases.

CONCLUSION

Experimental evidence for the expression of both PK1 and PK2 during the blood stages of malaria infection was provided. Interestingly, phylogenetic analysis revealed that the "PK2" type of enzyme appears to be confined to Apicomplexans, an important observation with respect to the assessment of PK2 as a drug-target.

Ecological impact assessment of metallurgic effluents using in situ biomarker assays

An ecological impact study was performed based on in situ biomarker assays with the waterflea Daphnia magna. The effects of metallurgic effluents on the energy metabolism, anti-oxidative metabolism and DNA damage were assessed in caged daphnids during a 4-week study. In situ survival and reproduction studies demonstrated a clear impact on these parameters in organisms exposed in the most polluted areas. At the downstream--sublethal--zone the organisms were disturbed within their tolerance limits, resulting in alterations of their energy metabolism. These data suggest an acclimation hypothesis, which was tested through the analysis of the energy metabolism of resident species: isopods and amphipods. These organisms had shifted to a decrease in their overall energy metabolism compared to the upstream region. This change in some biochemical processes suggests a selective advantage to cope with the prevailing environmental conditions. In addition, we found clear genotoxic effects caused by the industrial discharges that might correlate with a reduction in (long-term) survival.

Differential protein expression in brain capillary endothelial cells induced by hypoxia and posthypoxic reoxygenation

Cerebral ischemia causes functional alteration of the blood-brain barrier, formed by brain capillary endothelial cells (BCEC). Changes in protein expression and activity of selected differentially expressed enzymes were investigated in BCEC subjected to hypoxia (24 h) alone or followed by a 24-h reoxygenation. BCEC proteins were isolated, separated by 2-DE, and identified by MALDI-MS. Computer-based 2-D gel analysis identified 21 up-regulated proteins and 4 down-regulated proteins after hypoxia alone and 9 proteins that were further up-regulated after posthypoxic reoxygenation. The expression of the majority of hypoxia-induced proteins was reduced toward control levels during reoxygenation. The most prominent changes were identified for glycolytic enzymes (e.g., phosphoglycerate kinase), proteins of the ER (e.g., calreticulin), and cytoskeletal (e.g., vimentin) proteins. The results indicate that BCEC respond to hypoxia/reoxygenation by adaptive up-regulation of proteins involved in the glycolysis, protein synthesis, and stress response.

[Pyruvate kinase M2 (tumor M2-PK) as a screening tool for colorectal cancer (CRC). A review of current published data]

INTRODUCTION

Colonoscopy is currently supposed to be the best screening tool for colorectal cancer. However, the acceptance of the population is very poor although it has been included in screening programs in the German health system since 2002. Therefore, evaluation of additional screening tools seems to be of great interest. Recently testing for fecal occult blood (FOBT), genetic alterations or alterations in tumor metabolism (e.g., tumor M2-PK) are under investigation.

METHODS

The use of M2-PK measurement in the feces has been reported in 6 studies until today. The data of these studies were analyzed and critically reviewed.

RESULTS

The overall sensitivity of M2-PK is 77.9% concerning CRC. Specificity ranges from 74.3-83.3%. Overall sensitivity for adenomas is 45.9%, increasing to 61.1% for adenomas > 1 cm. A high percentage of positive results (90.4%) was also observed in patients with chronic inflammatory bowel disease.

CONCLUSIONS

Compared to FOBT or genetic testing the M2-PK test seems to be superior for CRC screening. Concerning handling, effectiveness and analysis, M2-PK seems to be a good possibility for large scale-screening of colorectal carcinoma. It might even be used to detect larger adenomas. Elevated levels of M2-PK in patients with acute and/or chronic inflammatory bowel diseases are probably due to proliferation of epithelial cells and leucocytes in the inflammatory area.

The activity and kinetics of pyruvate kinase in hypoxic newborns

Pyruvate kinase (PK) plays a key role in erythrocytes, which obtain most of their energy from glycolysis. This study investigated erythrocyte energy metabolism in hypoxic newborns, measuring pyruvate kinase activity, kinetic, and ATP levels in hypoxia. Forty-nine babies who had cord pH value lower than 7.2 and Apgar scores lower than 7 in the first minute were accepted as the hypoxic group, and 48 babies who had cord pH value higher than 7.2 and an Apgar score higher than 7 in the first minute were taken as controls. The erythrocyte mean PK activity was found to be lower (16.9+/-8.5 [5.8-47.9] EU/gHb) in the hypoxic group than the control group (21.3+/-10.9 [3.9-44.3] EU/gHb) (p<.05). The mean ATP value of hypoxic group was higher (19.2+/-11.3 [3.9-37.6] mM) compared to control group (13.8+/-7.16 [3.9-28.7] mM). In the kinetic study, with different ADP concentrations in the control group, the substrate amount (Km) that is needed to reach the half-maximum of enzyme activity (Vmax=27.7 Eu/gHb) was found to be 2.70 mM, but it was 1.47 mM to reach Vmax (22.7 Eu/gHb) in the hypoxic group. Vmax was 41.67 Eu/gHb and Km was 8.33 mM in the control group at different PEP concentrations, whereas Vmax was 21.7 Eu/gHb and Km was 0.89 mM in the hypoxic group. Increase in the ATP level while ePK activity decreases, suggesting that glycolysis increases in hypoxia. In the kinetic study, the substrate amount needed for reaching the half-maximum of enzyme activity was less in the hypoxic group, probably suggests that pyruvate kinase increases glycolysis by increasing its affinity to the substrates. In this way, erythrocytes may gain the energy required for oxygen delivery to tissues and maintaining ion gradient. This arrangement possibly proceeds from sygmoidal structure of pyruvate kinase.

[Comparison of different stool tests for the detection of cancer of the colon]

BACKGROUND AND OBJECTIVE

Colonoscopy is the gold standard for the diagnosis of colonic neoplasia. Because of the low compliance, the discomfort of bowel preparation and the procedure itself and the (albeit small) risk of perforation or bleeding alternative procedures such as stool tests are being focused on.

PATIENTS AND METHODS

After informed consent stool samples of 116 patients (44 male, 72 female, median age 47 years), scheduled for colonoscopy and 22 patients (17 m, 5 f, 69 y) with known colorectal cancer stool samples were collected. The samples were investigated by three methods: a biochemical (Guajak) test for fecal occult blood, an immunological test for fecal occult blood and a test determining the dimer pyruvat kinase M2 (tumor M2-PK).

RESULTS

Sensitivity for detection of colorectal cancer or polyps was 27 % and 10 % for the biochemical test, 91 % and 19 % for the immunological test and 77 % and 48 % for the M2-PK-test, respectively. Specificity was 89 %, 94 % and 72 %, respectively.

CONCLUSIONS

Both methods for detection of occult blood had a similar specificity. The sensitivity of the immunological test for the detection of colorectal cancer was significantly higher. The M2-PK-test had a markedly lower specificity in diagnosing cancer. Because of the low sensitivity for polyps the usefulness of stool tests is questionable. Reducing incidence and mortality of colorectal cancer should be achieved by colonoscopy, a recommendation that requires specific communication to the public.

Improved sensitivity in the diagnosis of gastro-intestinal tumors by fuzzy logic-based tumor marker profiles including the tumor M2-PK

The aim of this study was to improve diagnostic efficiency in the detection of gastro-intestinal cancers by using fuzzy logic modeling in combination with a tumor marker panel (CEA, CA72-4, CA19-9) including Tumor M2-PK. In this prospective study histologically confirmed colorectal (n=247), esophageal (n=86) and gastric cancer (n=122) patients were investigated and compared to control (n=53) persons without any malignant diseases. Tumor M2-PK was measured in plasma with an ELISA (ScheBoBiotech, Germany); all other markers were measured in sera (Roche, Germany). At 95% specificity, tumor detection was possible by the best single marker in colorectal cancer patients in 48% (Tumor M2-PK), in gastric cancers in 61% (CA72-4) and in esophageal cancers in 56% (Tumor M2-PK). A fuzzy logic rule-based system employing a tumor marker panel increased sensitivity significantly in colorectal cancers (p<0. 001) to 63% (Tumor M2-PK and CEA), in gastric cancers (p<0.001) to 81% (Tumor M2-PK and CA 72-4) and in esophageal cancers (p<0.02) to 74% (Tumor M2-PK and CA72-4). Adding a third marker further improved the sensitivity only marginally. Fuzzy logic analysis has proven to be more powerful than measurement of single markers alone or combinations using multiple logistic regression analysis of the markers. Therefore, with the fuzzy logic method and a tumor marker panel (including Tumor M2-PK), a new diagnostic tool for the detection of gastro-intestinal cancers is available.

Kupffer cell cytokines interleukin-1beta and interleukin-10 combine to inhibit phosphoenolpyruvate carboxykinase and gluconeogenesis in cultured hepatocytes

BACKGROUND AND AIMS

Recent evidence suggests that inflammatory cytokines may mediate reduced hepatic glucose production and reduced blood glucose concentrations in sepsis. Therefore the aim of this study is to provide direct evidence of a cytokine-mediated interaction between Kupffer cells and hepatocytes by characterising the effects of lipopolysaccharide-stimulated Kupffer cells on hepatocyte gluconeogenesis, and the activity of key regulatory enzymes of this pathway.

METHODS AND RESULTS

Primary isolates of hepatocytes co-cultured with lipopolysaccharide-stimulated Kupffer cells in Transwell inserts showed a 48% inhibition of gluconeogenesis (P < 0.001). RNase protection assay and ELISA of Kupffer cells and the culture media following exposure to lipopolysaccharide showed increased levels of interleukin-1 alpha and beta, tumour necrosis factor alpha and IL-10. The addition of IL-1beta and IL-10 to hepatocyte cultures inhibited gluconeogenesis by 52% (P < 0.001), whereas each cytokine alone was ineffective. To determine whether altered production or activity of phosphoenolpyruvate carboxykinase or pyruvate kinase was responsible for the reduced glucose synthesis, their mRNA, protein levels and enzyme activities were measured. Primary hepatocytes co-cultured with lipopolysaccharide-stimulated Kupffer cells or cultured with a combination of IL-1beta and IL-10 displayed reduced levels of phosphoenolpyruvate carboxykinase mRNA, protein and enzyme activity. In contrast the mRNA, protein levels and enzyme activity of pyruvate kinase were not altered; suggesting that gluconeogenesis was suppressed by downregulation of phosphoenolpyruvate carboxykinase.

CONCLUSIONS

Therefore, hypoglycaemia, which is often observed in sepsis, may be mediated by Kupffer cell-derived IL-1beta and IL-10. In addition this study suggests these cytokines inhibit phosphoenolpyruvate carboxykinase production and thereby hepatic gluconeogenesis.

Epigallocatechin gallate attenuates diet-induced obesity in mice by decreasing energy absorption and increasing fat oxidation

OBJECTIVE

To examine the antiobesity effect of epigallocatechin gallate (EGCG), a green tea bioactive polyphenol in a mouse model of diet-induced obesity.

METHODS

Obesity was induced in male New Zealand black mice by feeding of a high-fat diet. EGCG purified from green tea (TEAVIGO) was supplemented in the diet (0.5 and 1%). Body composition (quantitative magnetic resonance), food intake, and food digestibility were recorded over a 4-week period. Animals were killed and mRNA levels of uncoupling proteins (UCP1-3), leptin, malic enzyme (ME), stearoyl-CoA desaturase-1 (SCD1), glucokinase (GK), and pyruvate kinase (PK) were analysed in different tissues. Also investigated were acute effects of orally administered EGCG (500 mg/kg) on body temperature, activity (transponders), and energy expenditure (indirect calorimetry).

RESULTS

Dietary supplementation of EGCG resulted in a dose-dependent attenuation of body fat accumulation. Food intake was not affected but faeces energy content was slightly increased by EGCG, indicating a reduced food digestibility and thus reduced long-term energy absorption. Leptin and SCD1 gene expression in white fat was reduced but SCD1 and UCP1 expression in brown fat was not changed. In liver, gene expression of SCD1, ME, and GK was reduced and that of UCP2 increased. Acute oral administration of EGCG over 3 days had no effect on body temperature, activity, and energy expenditure, whereas respiratory quotient during night (activity phase) was decreased, supportive of a decreased lipogenesis and increased fat oxidation.

CONCLUSIONS

Dietary EGCG attenuated diet-induced body fat accretion in mice. EGCG apparently promoted fat oxidation, but its fat-reducing effect could be entirely explained by its effect in reducing diet digestibility.

Metabolism of the microregions of human breast cancer

Glucose and glutamine metabolism of two microregions of human infiltrating ductile breast cancer, the center and the periphery, was studied and the results were compared with those of healthy mammary glands. In general, the activities of glycolytic enzymes and of phosphate-dependent glutaminase were as follows: center>periphery>mammary gland. Insulin caused a marked increase of glucose consumption and lactate production by incubated slices of mammary gland but had no effect on both microregions of the tumor. Therefore, human breast cancer presents metabolic microregions.

The metabolic marker tumour pyruvate kinase type M2 (tumour M2-PK) shows increased expression along the metaplasia-dysplasia-adenocarcinoma sequence in Barrett's oesophagus

BACKGROUND

Proliferating and tumour cells express the glycolytic isoenzyme, pyruvate kinase type M2 (M2-PK). In tumours cells, M2-PK usually exists in dimeric form (tumour M2-PK), causing the accumulation of glycolytic phosphometabolites, which allows cells to invade areas with low oxygen and glucose concentrations.

AIMS

To investigate the expression of tumour M2-PK during the metaplasia-dysplasia-adenocarcinoma sequence of Barrett's oesophagus, and to assess the prognostic usefulness of tumour M2-PK in oesophageal cancer.

MATERIALS/METHODS

One hundred and ninety cases selected from the histopathology archives as follows: 17 reflux oesophagitis, 37 Barrett's oesophagus, 21 high grade dysplasia, 112 adenocarcinomas, and three control tumours. Sections were stained immunohistochemically with antibody to tumour M2-PK.

RESULTS

Tumour M2-PK was expressed in all cases, and increased cytoplasmic expression was seen with progression along the metaplasia-dysplasia-adenocarcinoma sequence. All cases of adenocarcinoma showed 100% staining so that tumour M2-PK was not a useful prognostic marker.

CONCLUSIONS

Tumour M2-PK is not a specific marker of Barrett's adenocarcinoma, but may be important as a marker of transformed and highly proliferating clones during progression along the metaplasia-dysplasia-adenocarcinoma sequence.

Faecal tumour M2 pyruvate kinase: a new, sensitive screening tool for colorectal cancer

Proliferating cells, especially tumour cells, express a special isoenzyme of pyruvate kinase, termed M2-PK, which can occur in a tetrameric form with a high affinity to its substrate, phosphoenolpyruvate (PEP), and in a dimeric form with a low PEP affinity. In tumour cells, the dimeric form is usually predominant and is therefore termed Tumour M2-PK. The levels of Tumour M2-PK within tumours and in EDTA-plasma correlate with staging and the ability of the tumour cells to metastasise. Since most colorectal tumours grow intraluminally, it appeared interesting to determine whether Tumour M2-PK is detectable in the faeces of tumour patients. Stool samples were tested by ELISA from controls without colorectal cancer and colorectal cancer patients. Whereas Tumour M2-PK levels were low in the control group (mean value+/-s.e.m.: 3.3+/-0.4, n=144), they were high in the case of colorectal cancer (56.1+/-15.3, n=60). At a cutoff value of 4 U ml(-1), the sensitivity was 73%. TNM and Dukes' classification of the tumours revealed a strong correlation between faecal Tumour M2-PK levels and staging. The determination of Tumour M2-PK in faeces provides a new promising screening tool for colorectal tumours.

A simple kinetic method for rapid mechanistic analysis of reversible enzyme inhibitors

A simple diagnostic method for mechanistic analysis of reversible enzyme inhibitors is presented. The method involves simple experimentation to determine how the inhibition by a reversible inhibitor changes in response to the substrate concentration varied in the assay. Four types of inhibitors are categorized based on their kinetic characteristic: (1) competitive or mutually exclusive inhibitors that compete with the substrate for the enzyme; (2) noncompetitive inhibitors that are independent of the substrate for binding to the enzyme; (3) antagonistic inhibitors where the binding affinity of the inhibitor is partially reduced by the substrate binding to the enzyme; and (4) synergistic inhibitors where inhibitor binding is enhanced by substrate binding. An equation was derived for data fitting and subsequent determination of inhibitor binding mode. The method was evaluated in three model enzyme systems, i.e., PK, adenylate kinase, and LDH, with known inhibitors. The method was also used to characterize a large number of unknown Csp3 inhibitors identified from HTS of a compound library consisting of 120,000 distinct chemical entities, a field test that validated the utility of the method. Among 76 Csp3 inhibitors analyzed, 70 were found to be non-mutually exclusive inhibitors, suggesting the existence of an allosteric site(s) in Csp3 for effective inhibition. The implication of this observation is discussed.

Tumor Suppressor Gene 14-3-3σ Is Down-Regulated whereas the Proto-Oncogene Translation Elongation Factor 1δ Is Up-Regulated in Non-Small Cell Lung Cancers As Identified by Proteomic Profiling

Lung cancer, a leading cause of cancer deaths, consists of two major groups: small cell lung cancer (SCLC) and nonsmall cell lung cancer (NSCLC) with the NSCLC accounting for approximately 75% cases of lung cancers. It has been suggested that molecular changes including overexpression of oncogenes and decreased expression of tumor suppressor genes are responsible for lung carcinogenesis. In this study, we analyzed protein profiles of four different human NSCLC cell lines compared with normal human bronchial epithelial cells using two-dimensional PAGE and MALDI-TOF mass spectrometry. We identified 12 protein spots with different expressions between the normal and cancer cells. Of these proteins, vimentin, cytokeratin 8, YB-1, PCNA, Nm23, hnRNP A2/B1, and HSP90beta were known to be up-regulated in lung cancers, which is consistent with the current study. We also found that the expression of M-type pyruvate kinase is altered in NSCLC likely due to changes in translational control and/or differential phosphorylation of the protein. Interestingly, the expression of the tumor suppressor gene 14-3-3sigma is down-regulated while that of the proto-oncogene TEF1delta is up-regulated in NSCLC cells. On the basis of these observations and previous studies, we propose that the altered expression of 14-3-3sigma and TEF1delta may be involved in lung carcinogenesis.