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

Using Pyruvate Kinase as a Predictor for Patient With Endometrial Cancer Having Complex Hyperplasia With Atypia to Prevent Hysterectomy and Preserve Fertility: Retrospective Immunohistochemical Study

OBJECTIVES

To explore whether the metabolic switches proceed or succeed the histological changes in precancerous lesions. To validate pyruvate kinase isoform 1 (PKM1) and pyruvate kinase isoform 2 (PKM2) as a histological biomarker to predict the progression of endometrial hyperplasia into invasive cancer status.

METHODS

The records of 56 patients with a primary diagnosis of complex hyperplasia with atypia after endometrial biopsy were selected and analyzed retrospectively. A set of 3 consecutive sections at 4-μm thickness were cut and studied with immunohistochemical stains. From each case, 2 to 3 fields with a diagnosis of complex hyperplasia with atypia were selected and compared. A single pathologist blinded to the final diagnosis assigned the scoring.

RESULTS

Positive immunostaining for PKM1 was observed in 31.25% (10 out of 32) of initial endometrial biopsy with the diagnosis of complex hyperplasia with atypia and final diagnosis of endometrial cancer, while 91.67% (out of 24) of patients with final diagnosis of negative endometrial cancer had endometrial biopsy with positive PKM1 staining ( P < .001). Positive immunostaining for PKM2 was observed in 100% of patient with endometrial biopsy result of endometrial hyperplasia with atypia (56 of 56).

CONCLUSIONS

Lack of staining with PKM1 expression may help to predict the fate of endometrial hyperplasia. The disappearance of this marker is associated with the progression of hyperplasia toward cancer phenotype. Further studies are needed to understand the causes and potential mechanisms for suppressing Pyruvate Kinase Isoform 1 expression in endometrial hyperplasia.

Curcumin decreases Warburg effect in cancer cells by down-regulating pyruvate kinase M2 via mTOR-HIF1α inhibition

Warburg effect is an emerging hallmark of cancer cells with pyruvate kinase M2 (PKM2) as its key regulator. Curcumin is an extensively-studied anti-cancer compound, however, its role in affecting cancer metabolism remains poorly understood. Herein, we show that curcumin inhibits glucose uptake and lactate production (Warburg effect) in a variety of cancer cell lines by down-regulating PKM2 expression, via inhibition of mTOR-HIF1α axis. Stable PKM2 silencing revealed that PKM2 is required for Warburg effect and proliferation of cancer cells. PKM2 over-expression abrogated the effects of curcumin, demonstrating that inhibition of Warburg effect by curcumin is PKM2-mediated. High PKM2 expression correlated strongly with poor overall survival in cancer, suggesting the requirement of PKM2 in cancer progression. The study unravels novel PKM2-mediated inhibitory effect of curcumin on metabolic capacities of cancer cells. To the best of our knowledge, this is the first study linking curcumin with PKM2-driven cancer glycolysis, thus, providing new perspectives into the mechanism of its anticancer activity.

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.

Resveratrol inhibits cancer cell metabolism by down regulating pyruvate kinase M2 via inhibition of mammalian target of rapamycin

Metabolism of cancer cells with pyruvate kinase M2 (PKM2) at its centre stage has assumed a prime significance in cancer research in recent times. Cancer cell metabolism, characterized by enhanced glucose uptake, production of lactate and anabolism is considered an ideal target for therapeutic interventions. Expression of PKM2 switches metabolism in favor of cancer cells, therefore, the present study was designed to investigate the hitherto unknown effect of resveratrol, a phytoalexin, on PKM2 expression and resultant implications on cancer metabolism. We observed that resveratrol down-regulated PKM2 expression by inhibiting mTOR signaling and suppressed cancer metabolism, adjudged by decreased glucose uptake, lactate production (aerobic glycolysis) and reduced anabolism (macromolecule synthesis) in various cancer cell lines. A contingent decrease in intracellular levels of ribose-5-phosphate (R5P), a critical intermediate of pentose phosphate pathway, accounted for a reduced anabolism. Consequently, the state of suppressed cancer metabolism resulted in decreased cellular proliferation. Interestingly, shRNA-mediated silencing of PKM2 inhibited glucose uptake and lactate production, providing evidence for the critical role of PKM2 and its mediation in the observed effects of resveratrol on cancer metabolism. Further, an over-expression of PKM2 abolished the observed effects of resveratrol, signifying the role of PKM2 downregulation as a critical function of resveratrol. The study reports a novel PKM2-mediated effect of resveratrol on cancer metabolism and provides a new dimension to its therapeutic potential.

Review of biomarkers in colorectal cancer

AIM

Advances in molecular technology have resulted in the discovery of many putative biomarkers relevant to colorectal cancer (CRC).

METHOD

Literature searches were performed on PubMed and EMBASE using the words 'colorectal cancer', AND 'biomarkers OR markers'. Biomarkers that are either currently in clinical use or have potential clinical use were identified.

RESULTS

Most potential markers are in the discovery phase waiting to undergo clinical validation. Hypermethylation of the plasma septin-9 gene shows promise as a nonstool-based screening tool. Hypermethylation of the DYPD gene (encodes the enzyme dihydropyrimidine dehydrogenase) and variation of the uridine diphosphate-glucuronosyltransferase 1A (UGT1A1) gene have predictive value for side effects and the efficacy of 5-fluoruracil and irinotecan, respectively. Mismatch repair protein immunohistochemistry is able to predict response to 5-fluorouracil, and the KRAS (Kirsten rat sarcoma viral oncogene) and B-RAF (v-RAF murine sarcoma viral oncogene homolog B1) somatic gene mutation status can predict the response to anti-epidermal growth factor receptor therapy.

CONCLUSION

Recent advances indicate that the widespread use of biomarkers may herald the next major advance in the diagnosis and management of CRC.

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.

Proteomic analysis of low dose arsenic and ionizing radiation exposure on keratinocytes

Human exposure to arsenic and ionizing radiation (IR) occur environmentally at low levels. While the human health effects of arsenic and IR have been examined separately, there is little information regarding their combined effects at doses approaching environmental levels. Arsenic toxicity may be affected by concurrent IR especially given their known individual carcinogenic actions at higher doses. We found that keratinocytes responded to either low dose arsenic and/or low dose IR exposure, resulting in differential proteomic expression based on 2-DE, immunoblotting and statistical analysis. Seven proteins were identified that passed a rigorous statistical screen for differential expression in 2-DE and also passed a strict statistical screen for follow-up immunoblotting. These included: alpha-enolase, epidermal-fatty acid binding protein, heat shock protein 27, histidine triad nucleotide-binding protein 1, lactate dehydrogenase A, protein disulfide isomerase precursor, and S100A9. Four proteins had combined effects that were different than would be expected based on the response to either individual toxicant. These data demonstrate a possible reaction to the combined insult that is substantially different from that of either separate treatment. Several proteins had different responses than what has been seen from high dose exposures, adding to the growing literature suggesting that the cellular responses to low dose exposures are distinct.

Tenascin-W, a new marker of cancer stroma, is elevated in sera of colon and breast cancer patients

Tenascins are extracellular matrix proteins present during the development of organisms as well as in pathological conditions. Tenascin-W, the fourth and last member of the tenascin family remains the least well-characterized one. Our study aimed to evaluate the potential significance of tenascin-W as cancer biomarker by monitoring its presence in the serum of colorectal and breast cancer patients and its expression in colorectal tumor tissues. To measure serum tenascin-W levels, a sensitive sandwich-ELISA was established. Mean tenascin-W concentration in sera of patients with nonmetastatic colorectal cancer at time of diagnosis was highly increased compared to that of healthy volunteers. A similar tendency was observed for tenascin-C in the same patient cohort. However, the increase was much more striking for tenascin-W. We also detected elevated tenascin-W levels in sera of breast cancer patients. Furthermore, we could show a prominent expression of tenascin-W in extracts from colorectal tumor tissues by immunoblot analysis, whereas tenascin-W was not detectable in the corresponding normal colon mucosa. To confirm the western blot results, we performed immunohistochemistry of frozen sections of the same patients as well as of an additional, independently chosen collection of colorectal cancer tissues. In all cases, similarly to tenascin-C, tenascin-W was detected in the tumor stroma. Our results reveal a clear association between elevated levels of tenascin-W and the presence of cancer. These results warrant further studies to evaluate the potential value of serum and tissue tenascin-W levels as diagnostic, prognostic or monitoring biomarker in colorectal, breast and possibly other solid cancers.

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.

Screening tests for colorectal cancer: A menu of options remains relevant

Until the early 1990s, no evidence was available to show that screening for colorectal cancer (CRC) by any means actually saved lives. Subsequently, sufficient evidence for the efficacy of fecal occult blood testing (FOBT) and flexible sigmoidoscopy allowed the US Preventive Services Task Force to publish guidelines for CRC screening. Since that time the major organizations in the United States concerned with screening guidelines have recommended a menu of screening test options including FOBT, flexible sigmoidoscopy, flexible sigmoidoscopy plus FOBT, barium enema, and colonoscopy. No organization, except for the American College of Gastroenterology, has designated any one of these options as "preferred." Nevertheless, the lay press and many gastroenterology opinion leaders have encouraged Americans to have only one test--colonoscopy. In this review we discuss the rationale for caution in designating one screening test as "the best" and present information on how new stool and serum tests can be used effectively to screen for CRC.

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.

Use of magnetic beads with immobilized monoclonal antibodies for isolation of highly pure plasma membranes

In plasma membrane proteome research, contamination of the isolated plasma membrane fraction with proteins from other organelles is still a problem. Even if highly specific isolation methods are used, such as density gradient centrifugation combined with selective extraction, contaminating proteins cannot be completely removed. To solve this problem, a protocol for the isolation of highly pure plasma membrane fractions from rat liver and two different hepatocellular carcinoma cell lines was developed. Magnetic beads with immobilized mAb's against highly expressed membrane proteins were used for specific binding of membrane vesicles and their separation from other organelles. Isolated plasma membranes were further selectively solubilized with different reagents and analyzed by use of different methods, such as Western blotting, 1- and 2-DE, and MS. Purification and further selective solubilization was validated by use of mAb's against the marker integral plasma membrane protein carcinoembryonic antigen cell adhesion molecule 1, and identification of isolated proteins by MS. The method presented here minimizes contamination with other organelles and enables further identification of membrane proteins.