Expression of brain-type glycogen phosphorylase is a potentially novel early biomarker in the carcinogenesis of human colorectal carcinomas

Brain-Type Glycogen Phosphorylase (PYGB) in the Pathologies of Diseases: A Systematic Review

Glycogen metabolism is a form of crucial metabolic reprogramming in cells. PYGB, the brain-type glycogen phosphorylase (GP), serves as the rate-limiting enzyme of glycogen catabolism. Evidence is mounting for the association of PYGB with diverse human diseases. This review covers the advancements in PYGB research across a range of diseases, including cancer, cardiovascular diseases, metabolic diseases, nervous system diseases, and other diseases, providing a succinct overview of how PYGB functions as a critical factor in both physiological and pathological processes. We present the latest progress in PYGB in the diagnosis and treatment of various diseases and discuss the current limitations and future prospects of this novel and promising target.

Inhibition of Glycogen Metabolism Induces Reactive Oxygen Species-Dependent Cytotoxicity in Anaplastic Thyroid Cancer in Female Mice

Anaplastic thyroid cancer (ATC) is one of the most lethal solid tumors, yet there are no effective, long-lasting treatments for ATC patients. Most tumors, including tumors of the endocrine system, exhibit an increased consumption of glucose to fuel cancer progression, and some cancers meet this high glucose requirement by metabolizing glycogen. Our goal was to determine whether ATC cells metabolize glycogen and if this could be exploited for treatment. We detected glycogen synthase and glycogen phosphorylase (PYG) isoforms in normal thyroid and thyroid cancer cell lines and patient-derived biopsy samples. Inhibition of PYG using CP-91,149 induced apoptosis in ATC cells but not normal thyroid cells. CP-91,149 decreased NADPH levels and induced reactive oxygen species accumulation. CP-91,149 severely blunted ATC tumor growth in vivo. Our work establishes glycogen metabolism as a novel metabolic process in thyroid cells, which presents a unique, oncogenic target that could offer an improved clinical outcome.

A Proteomic Platform Unveils the Brain Glycogen Phosphorylase as a Potential Therapeutic Target for Glioblastoma Multiforme

In the last few years, several efforts have been made to identify original strategies against glioblastoma multiforme (GBM): this requires a more detailed investigation of the molecular mechanism of GBM so that novel targets can be identified for new possible therapeutic agents. Here, using a combined biochemical and proteomic approach, we evaluated the ability of a blood–brain barrier-permeable 2,3-benzodiazepin-4-one, called 1g, to interfere with the activity and the expression of brain glycogen phosphorylase (PYGB) on U87MG cell line in parallel with the capability of this compound to inhibit the cell growth and cycle. Thus, our results highlighted PYGB as a potential therapeutic target in GBM prompting 1g as a capable anticancer drug thanks to its ability to negatively modulate the uptake and metabolism of glucose, the so-called “Warburg effect”, whose increase is considered a common feature of cancer cells in respect of their normal counterparts.

Identification of a glycolysis-related gene signature for survival prediction of ovarian cancer patients

Background

Ovarian cancer (OV) is deemed the most lethal gynecological cancer in women. The aim of this study was to construct an effective gene prognostic model for predicting overall survival (OS) in patients with OV.

Methods

The expression profiles of glycolysis‐related genes (GRGs) and clinical data of patients with OV were extracted from The Cancer Genome Atlas (TCGA) database. Univariate, multivariate, and least absolute shrinkage and selection operator Cox regression analyses were conducted, and a prognostic signature based on GRGs was constructed. The predictive ability of the signature was analyzed using training and test sets.

Results

A gene risk signature based on nine GRGs (ISG20, CITED2, PYGB, IRS2, ANGPTL4, TGFBI, LHX9, PC, and DDIT4) was identified to predict the survival outcome of patients with OV. The signature showed a good prognostic ability for OV, particularly high‐grade OV, in the TCGA dataset, with areas under the curve (AUC) of 0.709 and 0.762 for 3‐ and 5‐year survival, respectively. Similar results were found in the test sets, and the AUCs of 3‐, 5‐year OS were 0.714 and 0.772 in the combined test set. And our signature was an independent prognostic factor. Moreover, a nomogram combining the prediction model and clinical factors was developed.

Conclusion

Our study established a nine‐GRG risk model and nomogram to better predict OS in patients with OV. The risk model represents a promising and independent prognostic predictor for patients with OV. Moreover, our study on GRGs could offer guidance for the elucidation of underlying mechanisms in future studies.

Application of Proteomics and Metabonomics to Reveal the Molecular Basis of Atractylodis Macrocephalae Rhizome for Ameliorating Hypothyroidism Instead of Hyperthyroidism

As the treatments of diseases with Chinese herbs are holistic and characterized by multiple components, pathways, and targets, elucidating the efficacy of Chinese herbs in treating diseases, and their molecular basis, requires a comprehensive, network-based approach. In this study, we used a network pharmacology strategy, as well as in vivo proteomics and metabonomics, to reveal the molecular basis by which Atractylodis macrocephalae rhizome (AMR) ameliorates hypothyroidism. Eighteen main compounds from AMR and its fractions (volatile oil fraction, crude polysaccharides fraction, lactones fraction, oligosaccharide fraction, and atractyloside fraction) were identified by HPLC, and their targets were screened using the TCMSP database and Swiss Target Prediction. Disease targets were gathered from the TTD, CTD and TCMSP databases. Hub targets were screened by different plug-ins, such as Bisogene, Merge, and CytoNCA, in Cytoscape 3.7.1 software and analyzed for pathways by the DAVID database. Hypothyroidism and hyperthyroidism pharmacological models were established through systems pharmacology based on proteomic and metabolomic techniques. Finally, AMR and its fractions were able to ameliorate the hypothyroidism model to different degrees, whereas no significant improvements were noted in the hyperthyroidism model. The lactones fraction and the crude polysaccharides fraction were considered the most important components of AMR for ameliorating hypothyroidism. These amelioration effects were achieved through promoting substance and energy metabolism. In sum, the integrative approach used in this study demonstrates how network pharmacology, proteomics, and metabolomics can be used effectively to elucidate the efficacy, molecular basis, and mechanism of action of medicines used in TCM.

Muscle Glycogen Phosphorylase and Its Functional Partners in Health and Disease

Glycogen phosphorylase (PG) is a key enzyme taking part in the first step of glycogenolysis. Muscle glycogen phosphorylase (PYGM) differs from other PG isoforms in expression pattern and biochemical properties. The main role of PYGM is providing sufficient energy for muscle contraction. However, it is expressed in tissues other than muscle, such as the brain, lymphoid tissues, and blood. PYGM is important not only in glycogen metabolism, but also in such diverse processes as the insulin and glucagon signaling pathway, insulin resistance, necroptosis, immune response, and phototransduction. PYGM is implicated in several pathological states, such as muscle glycogen phosphorylase deficiency (McArdle disease), schizophrenia, and cancer. Here we attempt to analyze the available data regarding the protein partners of PYGM to shed light on its possible interactions and functions. We also underline the potential for zebrafish to become a convenient and applicable model to study PYGM functions, especially because of its unique features that can complement data obtained from other approaches.

PYGB Promoted Tumor Progression by Regulating Wnt/β-Catenin Pathway in Gastric Cancer

Gastric cancer is one of the most common gastrointestinal malignancy with high mortality in East Asia. Investigation of pathogenic mechanisms of gastric cancer is crucial to develop novel therapeutic strategies and identify new therapeutic candidates. Brain-type glycogen phosphorylase is a glycogen phosphorylase involved in glycogen metabolism, which participates in multiple physiological and pathological processes. Overexpression of brain-type glycogen phosphorylase has been reported in various types of cancer, such as colorectal cancer and non-small cell lung cancer, however, the potential role of brain-type glycogen phosphorylase in gastric cancer remains unclear. Herein, we observed brain-type glycogen phosphorylase expression was significantly elevated in human gastric cancer tissues and positively correlated with the clinical-pathological features including tumor size, lymph node involvement, and tumor, node, metastasis stage of patients with gastric cancer. We further reported brain-type glycogen phosphorylase depletion suppressed the growth of gastric cancer, weakened the epithelial–mesenchymal transformation, and reduced the migration and invasion ability in cell models. We further confirmed brain-type glycogen phosphorylase depletion inhibited tumor growth and lung metastasis in mice. Importantly, we found brain-type glycogen phosphorylase regulated the progression of gastric cancer via Wnt/β-catenin pathway, shedding lights on brain-type glycogen phosphorylase as a promising therapeutic target for drug design and development targeting gastric cancer.

Glycogen Phosphorylase B Is Regulated by miR101-3p and Promotes Hepatocellular Carcinoma Tumorigenesis

Glycogen metabolism plays a key role in tumorigenesis. High expression levels of glycogen phosphorylase B (PYGB) were reported in several cancers and might be served as a prognostic biomarker for cancer from precancerous lesions. Previous studies indicated the high expression of PYGB in hepatocellular carcinoma (HCC) tissues. However, the detailed roles of PYGB in HCC, as well as the regulatory mechanisms, are still unclear. In this study, we confirmed that PYGB was overexpressed in HCC tissues. PYGB overexpression was significantly associated with an aggressive tumor phenotype and poor prognosis of HCC patients. Functionally, PYGB knockdown suppressed HCC cell proliferation, migration and invasion in vitro, as well as tumorigenesis and metastasis in vivo. Bioinformatics analysis indicated that PYGB overexpression might enhance epithelial to mesenchymal transition (EMT) in HCC. Moreover, miR-101-3p was identified to post-transcriptionally inhibit the expression of PYGB via binding to 3′-UTR of PYGB. Overexpression of PYGB antagonized the regulatory effect of miR-101-3p on cell proliferation, migration and invasion in HCC cells. In summary, our results suggest that miR-101-3p/PYGB axis has an important role in HCC and PYGB could be served as a novel prognostic biomarker and therapeutic target for improving the prognosis of HCC patients.

Kinetic modeling of glucose central metabolism in hepatocytes and hepatoma cells

BACKGROUND

Kinetic modeling and control analysis of a metabolic pathway may identify the steps with the highest control in tumor cells, and low control in normal cells, which can be proposed as the best therapeutic targets.

METHODS

Enzyme kinetic characterization, pathway kinetic modeling and control analysis of the glucose central metabolism were carried out in rat (hepatoma AS-30D) and human (cervix HeLa) cancer cells and normal rat hepatocytes.

RESULTS

The glycogen metabolism enzymes in AS-30D, HeLa cells and hepatocytes showed similar kinetic properties, except for higher AS-30D glycogen phosphorylase (GP) sensitivity to AMP. Pathway modeling indicated that fluxes of glycogen degradation and PPP were mainly controlled by GP and NADPH consumption, respectively, in both hepatocytes and cancer cells. Likewise, hexose-6-phosphate isomerase (HPI) and phosphoglucomutase (PGM) exerted significant control on glycolysis and glycogen synthesis fluxes in cancer cells but not in hepatocytes. Modeling also indicated that glycolytic and glycogen synthesis fluxes could be strongly decreased when HPI and PGM were simultaneously inhibited in AS-30D cells but not in hepatocytes. Experimental assessment of these predictions showed that both the glycolytic and glycogen synthesis fluxes of AS-30D cells, but not of hepatocytes, were inhibited by oxamate, by inducing increased Fru1,6BP levels, a competitive inhibitor of HPI and PGM.

CONCLUSION

HPI and PGM seem suitable targets for decreasing glycolytic and glycogen synthesis fluxes in AS-30D cells but not in hepatocytes.

GENERAL SIGNIFICANCE

The present study identified new therapeutic targets within glucose central metabolism in the analyzed cancer cells, with no effects on non-cancer cells.

PYGB facilitates cell proliferation and invasiveness in non-small cell lung cancer by activating the Wnt-β-catenin signaling pathway

Brain-type glycogen phosphorylase (PYGB) has been correlated with the progression of various human malignancies; however, its effects and regulatory mechanisms in non-small cell lung cancer (NSCLC) are still unclear. We used Western blotting, immunohistochemistry, and qRT-PCR to verify that the protein and mRNA expression levels of PYGB are up-regulated in both NSCLC cell lines and tissues. The expression of PYGB was positively related to TNM stage, positive lymph node metastasis, and poor prognosis in patients with NSCLC. Moreover, overexpression of PYGB promoted cell proliferation, migration, and invasiveness, but inhibited apoptosis, in vitro. Immunofluorescence assays showed that overexpression of PYGB promoted the nuclear import and accumulation of β-catenin. By comparison, silencing PYGB produced the opposite effects. Further, overexpression of PYGB resulted in activation of the Wnt signaling pathway, and transfection with Sh-PYGB produced the opposite effect, and these effects were abrogated by XAV-939 (a β-catenin inhibitor) or overexpression of β-catenin, respectively. Finally, knockdown of PYGB inhibited tumor growth in a mouse model of xenograft tumors. These findings highlight the role of PYGB in the progression of NSCLC, and reveal a link between PYGB and the Wnt-β-catenin signaling pathway, thus providing a new potential target for treatment of NSCLC.

Glycogen phosphorylase B promotes ovarian cancer progression via Wnt/β-catenin signaling and is regulated by miR-133a-3p

BACKGROUND

Ovarian cancer is one of the most common gynecologic cancers with high morbidity and mortality in women. Glycogen metabolism plays a critical role in cancer development and glycogen phosphorylase B (PYGB) has reported to be involved in various tumors. Here, we explored the role of PYGB in ovarian cancer.

METHODS

PYGB mRNA expression were examined in ovarian cancer tissue and also analyzed using the dataset from The Cancer Genome Atlas cohort. Correlations between PYGB expression and prognosis of ovarian cancer patients were analyzed. PYGB was silenced to evaluate the ovarian cell proliferation, invasion and migration in vitro and tumorigenesis in vivo. MiR-133a-3p targeting PYGB was identified using online tools and confirmed with luciferase reporter experiment. MiR-133a-3p overexpression using miRNA mimics was conducted to evaluate its function on ovarian cancer cells.

RESULTS

We showed that PYGB was upregulated in ovarian cancer tissue and high level of PYGB expression is markedly correlated with poor prognosis of ovarian cancer patients. PYGB knockdown significantly suppressed ovarian cancer cell proliferation, invasion and migration. Xenograft tumor formation further demonstrated that knockdown PYGB inhibited ovarian tumor development. Bioinformatics analysis revealed that PYGB regulated Wnt/β-catenin signaling pathway in ovarian cancer cells. Mechanistically, miR-133a-3p directly bound to 3'-untranslated region of PYGB and overexpression miR-133a-3p suppressed proliferation, invasion and migration in ovarian cancer cells.

CONCLUSION

Our data suggest that miR-133a-3p/PYGB/Wnt-β-catenin axis plays a critical role in human ovarian cancer, which might serve as a promising therapeutic target of ovarian cancer treatment in the future.

Silencing of PYGB suppresses growth and promotes the apoptosis of prostate cancer cells via the NF‑κB/Nrf2 signaling pathway

Brain‑type glycogen phosphorylase (PYGB) is an enzyme that metabolizes glycogen, whose function is to provide energy for an organism in an emergency state. The present study purposed to investigate the role and mechanism of PYGB silencing on the growth and apoptosis of prostate cancer cells. A cell counting kit‑8 assay and flow cytometry were performed to determine the cell viability, apoptosis and reactive oxygen species (ROS) content, respectively. Colorimetry was performed to analyze the activity of caspase‑3. Western blotting and reverse transcription‑quantitative polymerase chain reaction were used to evaluate the associated mRNA and protein expression levels. The results revealed that PYGB was upregulated in prostate cancer tissues and was associated with disease progression. In addition, PYGB silencing suppressed the cell viability of PC3 cells. PYGB silencing promoted apoptosis of PC3 cells via the regulation of the expression levels of cleaved‑poly (adenosine diphosphate‑ribose) polymerase, cleaved‑caspase‑3, B‑cell lymphoma‑2 (Bcl‑2) and Bcl‑2‑associated X protein. PYGB silencing increased the ROS content in PC3 cells, and affected nuclear factor (NF)‑κB/nuclear factor‑erythroid 2‑related factor 2 (Nrf2) signaling pathways in PC3 cells. In conclusion, PYGB silencing suppressed the growth and promoted the apoptosis of prostate cancer cells by affecting the NF‑κB/Nrf2 signaling pathway. The present study provided evidence that may lead to the development of a potential therapeutic strategy for prostate cancer.

PYGB siRNA inhibits the cell proliferation of human osteosarcoma cell lines

Osteosarcoma is the most common malignant bone carcinoma that primarily occurs between childhood to adolescence. It was suggested by recent research that the Brain type glycogen phosphorylase (PYGB) gene may serve an important role in various types of cancer. In the present study, the PYGB gene was knocked down in order to evaluate the cell viability, invasion and migration of the human osteosarcoma cell lines MG63 and HOS. The expression levels of PYGB in osteosarcoma and bone cyst tissue samples, as well as in the osteosarcoma cell lines were identified using reverse transcription-quantitative polymerase chain reaction and western blot assay. Subsequently, a Cell Counting kit 8 assay was employed to evaluate cell proliferation. Cell apoptosis rate and cell cycle distribution were measured by flow cytometry. In addition, cell invasion and migration were evaluated through a Transwell assay. The expression levels of the cell apoptosis and tumor metastasis associated proteins B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein, E-cadherin, Twist, matrix metalloproteinase (MMP)-9 and MMP2 were measured via western blotting. PYGB exhibited a higher expression level in the osteosarcoma tissue samples, particularly in the human osteosarcoma cell lines MG63 and HOS. Knockdown of PYGB resulted in a decline in cell proliferation, invasion and migration, which was coupled with induced cell apoptosis and cell cycle arrest in MG63 and HOS cells. Furthermore, alterations in the expression of apoptosis and metastasis associated proteins indicated that small interfering (si)PYGB may have regulated cell viability by targeting the Bcl/Caspase and cyclin dependent kinase (CDK)-1 signaling pathway. In conclusion, PYGB siRNA exerted an inhibitory effect on the cell viability of the human osteosarcoma cells MG63 and HOS by blocking the Caspase/Bcl and CDK1 signaling pathway, highlighting novel potential therapeutic methods for treating osteosarcoma.

KIAA1199 interacts with glycogen phosphorylase kinase β-subunit (PHKB) to promote glycogen breakdown and cancer cell survival

The KIAA1199 gene was first discovered to be associated with non-syndromic hearing loss. Recently, several reports have shown that the up-regulation of KIAA1199 is associated with cancer cell migration or invasion and a poor prognosis. These findings indicate that KIAA1199 may be a novel target for cancer therapy. Therefore, we explored in detail the function of KIAA1199 in cancer cells. In this study, we investigated the interaction of KIAA1199 protein with intracellular proteins in cancer cells. To this end, we expressed KIAA1199-MBP fusion protein and performed a pull-down assay. In addition, KIAA1199-overexpressing cancer cell lines were constructed using a retroviral vector and were used for further experiments. A pull-down analysis showed that the glycogen phosphorylase kinase β-subunit (PHKB) interacted with the C-terminal region of KIAA1199 protein. Furthermore, we observed the interaction of KIAA1199 with glycogen phosphorylase brain form (PYGB) under serum-free conditions. The interaction promoted glycogen breakdown and cancer cell survival. Our findings indicate that KIAA1199 plays an important role in glycogen breakdown and cancer cell survival and that it may represent a novel target for cancer therapy.

Enzymatic features of the glucose metabolism in tumor cells

Many tumor types exhibit an impaired Pasteur effect, i.e. despite the presence of oxygen, glucose is consumed at an extraordinarily high rate compared with the tissue from which they originate - the so-called 'Warburg effect'. Glucose has to serve as the source for a diverse array of cellular functions, including energy production, synthesis of nucleotides and lipids, membrane synthesis and generation of redox equivalents for antioxidative defense. Tumor cells acquire specific enzyme-regulatory mechanisms to direct the main flux of glucose carbons to those pathways most urgently required under challenging external conditions such as varying substrate availability, presence of anti-cancer drugs or different phases of the cell cycle. In this review we summarize the currently available information on tumor-specific expression, activity and kinetic properties of enzymes involved in the main pathways of glucose metabolism with due regard to the explanation of the regulatory basis and physiological significance of the Warburg effect. We conclude that, besides the expression level of the metabolic enzymes involved in the glucose metabolism of tumor cells, the unique tumor-specific pattern of isozymes and accompanying changes in the metabolic regulation below the translation level enable tumor cells to drain selfishly the blood glucose pool that non-transformed cells use as sparingly as possible.

Biomarkers of human gastrointestinal tract regions

Dysregulation of intestinal epithelial cell performance is associated with an array of pathologies whose onset mechanisms are incompletely understood. While whole-genomics approaches have been valuable for studying the molecular basis of several intestinal diseases, a thorough analysis of gene expression along the healthy gastrointestinal tract is still lacking. The aim of this study was to map gene expression in gastrointestinal regions of healthy human adults and to implement a procedure for microarray data analysis that would allow its use as a reference when screening for pathological deviations. We analyzed the gene expression signature of antrum, duodenum, jejunum, ileum, and transverse colon biopsies using a biostatistical method based on a multivariate and univariate approach to identify region-selective genes. One hundred sixty-six genes were found responsible for distinguishing the five regions considered. Nineteen had never been described in the GI tract, including a semaphorin probably implicated in pathogen invasion and six novel genes. Moreover, by crossing these genes with those retrieved from an existing data set of gene expression in the intestine of ulcerative colitis and Crohn's disease patients, we identified genes that might be biomarkers of Crohn's and/or ulcerative colitis in ileum and/or colon. These include CLCA4 and SLC26A2, both implicated in ion transport. This study furnishes the first map of gene expression along the healthy human gastrointestinal tract. Furthermore, the approach implemented here, and validated by retrieving known gene profiles, allowed the identification of promising new leads in both healthy and disease states.

Differential expression of proteins during the canceration of colorectal adenoma cells

Colorectal carcinoma is one of the most frequently seen malignant tumors of the gastric tract. Colorectal adenomas are considered to be precancerous lesions of colorectal carcinoma. The adenoma-carcinoma sequence has traditionally been characterized as a uniform progression from normal mucosa to adenoma to carcinoma through an underlying homogenous carcinogenic pathway. Current research indicates that some proteins are differentially expressed in colorectal adenomas during their carcinomatous changes. These proteins include cell skeleton-related proteins, intracellular enzymes and proteins involved in cellular signal transduction. The functional roles of these proteins in the carcinomatous changes of colorectal adenomas differ greatly from each other and have not yet been fully clarified. This article reviews these differentially expressed proteins and briefly describes the possible mechanism by which these proteins cause the malignant transition from colorectal adenoma to colorectal carcinoma. Furthermore, proteomic technology has developed rapidly and has been simultaneously applied to the detection and characterization of various kinds of proteins due to its high throughput and convenient nature. This article also introduces the utilization of proteomics to identify and compare proteins that are differentially expressed between colorectal adenoma and colorectal carcinoma. Research on these proteins may lead to the identification of cancer markers that could subsequently facilitate the early diagnosis and further understanding of colorectal carcinoma.

Clinicopathological significance of BGP expression in non-small-cell lung carcinoma: relationship with histological type, microvessel density and patients' survival

AIMS

Brain-type glycogen phosphorylase (BGP) is the major isoform of glycogen phosphorylase found in fetal and neoplastic tissues, and is generally thought to induce glucose supply during an ischaemic period. This study was performed to investigate BGP expression in non-small-cell lung carcinoma (NSCLC).

METHODS

A total of 119 cases of NSCLC, including 63 squamous cell carcinomas (SqCCs) and 56 adenocarcinomas (ACs), were imunohistochemically evaluated for BGP expression, and its expression was correlated with clinicopathological parameters.

RESULTS

In total, 76.5% were positive, while non-neoplastic bronchial epithelial cells were weakly positive and pneumocytes were negative. High BGP expression was noted in 78.6% of ACs and 36.5% of SqCCs (p=0.001). Microvessel density was higher in the low BGP expression tumours (29.6 +/- 16.9/mm(2)) than in the high expression tumours (22.8+/-13.8/mm(2)) (p=0.017). BGP expression did not correlate with patient age or tumour stage, but was more frequent in females than males. Kaplan-Meier analysis showed that high BGP expression was associated with poorer survival (p=0.032).

CONCLUSIONS

BGP is expressed in NSCLC, particularly AC, and is an independent poor prognostic factor.

In silico whole-genome screening for cancer-related single-nucleotide polymorphisms located in human mRNA untranslated regions

BACKGROUND

A promising application of the huge amounts of genetic data currently available lies in developing a better understanding of complex diseases, such as cancer. Analysis of publicly available databases can help identify potential candidates for genes or mutations specifically related to the cancer phenotype. In spite of their huge potential to affect gene function, no systematic attention has been paid so far to the changes that occur in untranslated regions of mRNA.

RESULTS

In this study, we used Expressed Sequence Tag (EST) databases as a source for cancer-related sequence polymorphism discovery at the whole-genome level. Using a novel computational procedure, we focused on the identification of untranslated region (UTR)-localized non-coding Single Nucleotide Polymorphisms (UTR-SNPs) significantly associated with the tumoral state. To explore possible relationships between genetic mutation and phenotypic variation, bioinformatic tools were used to predict the potential impact of cancer-associated UTR-SNPs on mRNA secondary structure and UTR regulatory elements. We provide a comprehensive and unbiased description of cancer-associated UTR-SNPs that may be useful to define genotypic markers or to propose polymorphisms that can act to alter gene expression levels. Our results suggest that a fraction of cancer-associated UTR-SNPs may have functional consequences on mRNA stability and/or expression.

CONCLUSION

We have undertaken a comprehensive effort to identify cancer-associated polymorphisms in untranslated regions of mRNA and to characterize putative functional UTR-SNPs. Alteration of translational control can change the expression of genes in tumor cells, causing an increase or decrease in the concentration of specific proteins. Through the description of testable candidates and the experimental validation of a number of UTR-SNPs discovered on the secreted protein acidic and rich in cysteine (SPARC) gene, this report illustrates the utility of a cross-talk between in silico transcriptomics and cancer genetics.

Immunocytochemical localization of glycogen phosphorylase isozymes in rat nervous tissues by using isozyme-specific antibodies

Isozyme-specific antibodies were raised against peptides from the low-homology regions of the sequences of rat glycogen phosphorylase BB and MM isozymes by immunization of rabbits and guinea pigs. Immunocytochemical double-labelling experiments on frozen sections of rat nervous tissues were performed to investigate the isozyme localization pattern. Astrocytes throughout the brain and spinal cord expressed both isozymes in perfect co-localization. Ependymal cells only expressed the BB isozyme. Most neurones were not immunoreactive. The rare neurones that contained glycogen phosphorylase only expressed the BB isozyme. Nearly all of these neurones formed part of the afferent somatosensory system. These findings stress the general importance of glycogen in neural energy metabolism and indicate a special role for the glycogen phosphorylase BB isozyme in neurones in the somatosensory system.

Frequent p53 mutation in brain (fetal)-type glycogen phosphorylase positive foci adjacent to human 'de novo' colorectal carcinomas

'de novo' carcinogenesis has been advocated besides 'adenoma carcinoma sequence' as another dominant pathway leading to colorectal carcinoma. Our recent study has demonstrated that the distribution of brain (fetal)-type glycogen phosphorylase (BGP) positive foci (BGP foci) has a close relationship with the location of 'de novo' carcinoma. The aims of the present study are to investigate genetic alteration in the BGP foci and to characterize them in the 'de novo' carcinogenesis. 17 colorectal carcinomas without any adenoma component expressing both immunoreactive p53 and BGP protein were selected from 96 resected specimens from our previous study. Further investigations to examine the proliferating cell nuclear antigen (PCNA)-labelling index, and the p53 and the codon 12 of K-ras mutation using the polymerase chain reaction-single strand conformation polymorphism were performed in the BGP foci, BGP negative mucosa and carcinoma. The BGP foci were observed sporadically in the transitional mucosa adjacent to the carcinoma in all cases. The PCNA labelling index in the BGP foci was significantly higher than that in the BGP negative mucosa (P< 0.001). p53 mutations were observed in 8 carcinomas, but no K-ras mutation was detected. Interestingly, although none of the overexpressions of p53 protein was detected immunohistochemically in the BGP positive foci, the p53 gene frequently (41.2% of the BGP foci tested) mutated in spite of no K-ras mutation. The present study demonstrates potentially premalignant foci in the colorectal transitional mucosa with frequent p53 gene mutation. It is suggested that BGP foci are promising candidates for the further investigation of 'de novo' colorectal carcinogenesis.