Proteomic expression analysis of colorectal cancer by two-dimensional differential gel electrophoresis

An optimized predictor panel for colorectal cancer diagnosis based on the combination of tumor-associated antigens obtained from protein and phage microarrays

Humoral response in cancer patients appears early in cancer progression and can be used for diagnosis, including early detection. By using human recombinant protein and T7 phage microarrays displaying colorectal cancer (CRC)-specific peptides, we previously selected 6 phages and 6 human recombinant proteins as tumor-associated antigens (TAAs) with high diagnostic value. After completing validation in biological samples, TAAs were classified according to their correlation, redundancy in reactivity patterns and multiplex diagnostic capabilities. For predictor model optimization, TAAs were reanalyzed with a new set of samples. A combination of three phages displaying peptides homologous to GRN, NHSL1 and SREBF2 and four proteins PIM1, MAPKAPK3, FGFR4 and ACVR2B, achieved an area under the curve (AUC) of 94%, with a sensitivity of 89.1% and specificity of 90.0%, to correctly predict the presence of cancer. For early colorectal cancer stages, the AUC was 90%, with a sensitivity of 88.2% and specificity of 82.6%. In summary, we have defined an optimized predictor panel, combining TAAs from different sources, with highly improved accuracy and diagnostic value for colorectal cancer. This article is part of a Special Issue entitled: Translational Proteomics.

Expression of UQCRC1 in primary colorectal cancer and lymph node metastases

AIM: To screen new biomarkers for colorectal cancer (CRC) by identifying differentially expressed proteins between CRC and matched normal mucosa using proteomic technology and to analyze the association of identified biomarkers with colorectal carcinogenesis, development and lymph node metastasis.

METHODS: Six pairs of fresh samples of CRC and matched normal mucosa were analyzed by two-dimensional differential gel electrophoresis (2D-DIGE) followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The expression of the identified differential protein ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) was validated in 78 cases of CRC, matched normal mucosa and lymph node metastases. The immunostaining intensity of UQCRC1 was scored. Wilcoxon signed rank test and Krukal-Wallis test were used for statistical analysis.

RESULTS: 2D-DIGE analysis showed that the intensity of a protein spot was significantly increased by 2.14 folds (P < 0.001) in CRC. This spot was confirmed to be UQCRC1 by MALDI-TOF-MS. Immunohistochemistry analysis revealed that the immunostaining intensity of UQCRC1 was significantly higher in CRC than in matched normal mucosa (2.28 ± 0.95 vs 1.81 ± 0.88, P < 0.001). However, the expression of UQCRC1 had no correlation with differentiation, TNM stage or tumor location (all P > 0.05). The intensity of UQCRC1 was significantly lower in primary CRC than in lymph node metastases (P < 0.05).

CONCLUSION: UQCRC1 may play an important role in colorectal carcinogenesis and lymph node metastases.

Desmin expression in colorectal cancer stroma correlates with advanced stage disease and marks angiogenic microvessels

Introduction

Biomarkers that improve stratification of colorectal cancer patients for adjuvant therapy versus resection alone, or that are predictive of response to therapeutic agents, have the potential to greatly improve patient selection for such therapies. The aim was to determine proteins differentially expressed within the malignant epithelial glands and closely associated stromal elements compared to matched normal mucosa, and to characterise the over-expression of one such protein as a potential biomarker.

Methods

Protein from laser microdissected tumor and normal mucosa was analysed by two dimensional difference gel electrophoresis (2D DIGE) and mass spectrometry to determine differentially over expressed tumor proteins. Tumor over-expression of one such protein, desmin, was quantified using immunofluorescence staining in a larger cohort. Dual staining for desmin and vimentin, or desmin and von Willebrand factor, was performed to determine the cell type of interest.

Results

Desmin expression was significantly increased between stage I and III tumors, (P < 0.0001), and stage II and III tumors, (P < 0.0001). Strong focal desmin expression was found in stroma directly adjacent to carcinomatous glands and microvessels. These cells showed co-localisation of desmin and vimentin in close association with cells expressing VWF, indicating they were pericytes. Significantly higher levels of desmin-positive pericytes were observed in late stage tumors, consistent with increased angiogenesis.

Conclusion

Pericyte coverage of vasculature is a marker of vessel maturation, hence desmin expression may have use as a marker for microvessel maturation. Clinical trials will be needed to determine its use in identifying tumors that will be less responsive to anti-angiogenic therapy.

Identification and verification of heat shock protein 60 as a potential serum marker for colorectal cancer

Colorectal cancer (CRC) is a major public health issue worldwide, and novel tumor markers may contribute to its efficient management by helping in early detection, prognosis or surveillance of disease. The aim of our study was to identify new serum biomarkers for CRC, and we followed a phased biomarker discovery and validation process to obtain an accurate preliminary assessment of potential clinical utility. We compared colonic tumors and matched normal tissue from 15 CRC patients, using two-dimensional difference gel electrophoresis (2D-DIGE), and identified 17 proteins that had significant differential expression. These results were further confirmed by western blotting for heat shock protein (HSP) 60, glutathione-S-transferase Pi, α-enolase, T-complex protein 1 subunit β, and leukocyte elastase inhibitor, and by immunohistochemistry for HSP60. Using mAbs raised against HSP60, we developed a reliable (precision of 5-15%) and sensitive (0.3 ng·mL(-1)) immunoassay for the detection of HSP60 in serum. Elevated levels of HSP60 were found in serum from CRC patients in two independent cohorts; the receiver-operating characteristic curve obtained in 112 patients with CRC and 90 healthy controls had an area under the curve (AUC) of 0.70, which was identical to the AUC of carcinoembryonic antigen. Combination of serum markers improved clinical performance: the AUC of a three-marker logistic regression model combining HSP60, carcinoembryonic antigen and carbohydrate antigen 19-9 reached 0.77. Serum HSP60 appeared to be more specific for late-stage CRC; therefore, future studies should evaluate its utility for determining prognosis or monitoring therapy rather than early detection.

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) impairs the regulation of apoptosis in megakaryocytes by activating NF-κB: a proteomic study

We previously showed that the Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and its receptor VPAC1 are negative regulators of megakaryopoiesis and platelet function, but their downstream signaling pathway that inhibits this process still remained unknown. A combined proteomic, transcriptomic, and bioinformatic approach was here used to elucidate the molecular mechanisms underlying PACAP signaling via VPAC1 in megakaryocytes. Two-dimensional difference gel electrophoresis and tandem MS were applied to detect differentially expressed proteins in megakaryocytic CHRF cells stimulated with PACAP. The majority of the 120 proteins modulated by PACAP belong to the class of "cell cycle and apoptosis" proteins. The up- or down-regulated expression of some proteins was confirmed by immunoblot and immunohistochemical analysis. A meta-analysis of our data and 12 other published studies was performed to evaluate signaling pathways involved in different cellular models of PACAP response. From 2384 differentially expressed genes/proteins, 83 were modulated by PACAP in at least three independent studies and Ingenuity Pathway Analysis further identified apoptosis as the highest scored network with NF-κB as a key-player. PACAP inhibited serum depletion-induced apoptosis of CHRF cells via VPAC1 stimulation. In addition, PACAP switched on NF-κB dependent gene expression since higher nuclear levels of the active NF-κB p50/p65 heterodimer were found in CHRF cells treated with PACAP. Finally, a quantitative real time PCR apoptosis array was used to study RNA from in vitro differentiated megakaryocytes from a PACAP overexpressing patient, leading to the identification of 15 apoptotic genes with a 4-fold change in expression and Ingenuity Pathway Analysis again revealed NF-κB as the central player. In conclusion, our findings suggest that PACAP interferes with the regulation of apoptosis in megakaryocytes, probably via stimulation of the NF-κB pathway.

Surface-affinity profiling to identify host-pathogen interactions

Proteolytic treatment of intact bacterial cells has proven to be a convenient approach for the identification of surface-exposed proteins. This class of proteins directly interacts with the outside world, for instance, during adherence to human epithelial cells. Here, we aimed to identify host receptor proteins by introducing a preincubation step in which bacterial cells were first allowed to capture human proteins from epithelial cell lysates. Using Streptococcus gallolyticus as a model bacterium, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of proteolytically released peptides yielded the identification of a selective number of human epithelial proteins that were retained by the bacterial surface. Of these potential receptors for bacterial interference, (cyto)keratin-8 (CK8) was verified as the most significant hit, and its surface localization was investigated by subcellular fractionation and confocal microscopy. Interestingly, bacterial enolase could be assigned as an interaction partner of CK8 by MS/MS analysis of cross-linked protein complexes and complementary immunoblotting experiments. As surface-exposed enolase has a proposed role in epithelial adherence of several Gram-positive pathogens, its interaction with CK8 seems to point toward a more general virulence mechanism. In conclusion, our study shows that surface-affinity profiling is a valuable tool to identify novel adhesin-receptor pairs, which advocates its application in other hybrid biological systems.

The intestinal microbiota, gastrointestinal environment and colorectal cancer: a putative role for probiotics in prevention of colorectal cancer?

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States, and, even though 5-15% of the total CRC cases can be attributed to individual genetic predisposition, environmental factors could be considered major factors in susceptibility to CRC. Lifestyle factors increasing the risks of CRC include elevated body mass index, obesity, and reduced physical activity. Additionally, a number of dietary elements have been associated with higher or lower incidence of CRC. In this context, it has been suggested that diets high in fruit and low in meat might have a protective effect, reducing the incidence of colorectal adenomas by modulating the composition of the normal nonpathogenic commensal microbiota. In addition, it has been demonstrated that changes in abundance of taxonomic groups have a profound impact on the gastrointestinal physiology, and an increasing number of studies are proposing that the microbiota mediates the generation of dietary factors triggering colon cancer. High-throughput sequencing and molecular taxonomic technologies are rapidly filling the knowledge gaps left by conventional microbiology techniques to obtain a comprehensive catalog of the human intestinal microbiota and their associated metabolic repertoire. The information provided by these studies will be essential to identify agents capable of modulating the massive amount of gut bacteria in safe noninvasive manners to prevent CRC. Probiotics, defined as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host" (219), are capable of transient modulation of the microbiota, and their beneficial effects include reinforcement of the natural defense mechanisms and protection against gastrointestinal disorders. Probiotics have been successfully used to manage infant diarrhea, food allergies, and inflammatory bowel disease; hence, the purpose of this review was to examine probiotic metabolic activities that may have an effect on the prevention of CRC by scavenging toxic compounds or preventing their generation in situ. Additionally, a brief consideration is given to safety evaluation and production methods in the context of probiotics efficacy.

Vimentin in cancer and its potential as a molecular target for cancer therapy

Vimentin, a major constituent of the intermediate filament family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress. Vimentin is overexpressed in various epithelial cancers, including prostate cancer, gastrointestinal tumors, tumors of the central nervous system, breast cancer, malignant melanoma, and lung cancer. Vimentin's overexpression in cancer correlates well with accelerated tumor growth, invasion, and poor prognosis; however, the role of vimentin in cancer progression remains obscure. In recent years, vimentin has been recognized as a marker for epithelial-mesenchymal transition (EMT). Although EMT is associated with several tumorigenic events, vimentin's role in the underlying events mediating these processes remains unknown. By virtue of its overexpression in cancer and its association with tumor growth and metastasis, vimentin serves as an attractive potential target for cancer therapy; however, more research would be crucial to evaluate its specific role in cancer. Our recent discovery of a vimentin-binding mini-peptide has generated further impetus for vimentin-targeted tumor-specific therapy. Furthermore, research directed toward elucidating the role of vimentin in various signaling pathways would reveal new approaches for the development of therapeutic agents. This review summarizes the expression and functions of vimentin in various types of cancer and suggests some directions toward future cancer therapy utilizing vimentin as a potential molecular target.

Proteomic analysis of advanced colorectal cancer by laser capture microdissection and two-dimensional difference gel electrophoresis

The emergence of laser capture microdissection (LCM) and two-dimensional difference gel electrophoresis (2D-DIGE) has been shown to greatly improve the accuracy and sensitivity of global protein expression analysis. However, their combined use in profiling tumour proteome has rarely been reported. In this study, we applied these techniques to profile the protein expression changes of the late stage colorectal cancer (CRC) and its liver metastases. The study revealed that both the primary and secondary tumours showed a distinct protein expression profile compared to normal tissues, but were indistinguishable from each other. Differential analysis between the primary tumour and patient-matched normal colon mucosa identified a total of 71 proteins to be altered in CRC. Over 40% of these proteins have been previously reported as CRC-related proteins, validating the accuracy of the current analysis. We have also identified many previously unknown changes including overexpression of ACY1, HSC70, HnRNP I, HnRNP A3, SET, ANP32A and TUFM in CRC, which have been further verified by western blotting and immunohistochemistry. This study demonstrated that LCM in combination with 2D-DIGE is a powerful tool to analyse the proteome of tumour tissues and may lead to the identification of potential novel protein markers and therapeutic targets for cancer.

2-D DIGE uterine endothelial proteomic profile for maternal chronic binge-like alcohol exposure

Little is known about alcohol effects on the utero-placental compartment during pregnancy. For the first time, we utilized 2-D DIGE quantitative proteomics to evaluate the role of the uterus in Fetal Alcohol Spectrum Disorders (FASD) pathogenesis. Uterine artery endothelial cells were isolated from pregnant ewes, FAC sorted, validated, and maintained in culture. To mimic maternal binge drinking patterns, cells were cultured in the absence or presence of alcohol (300 mg/dl) in a compensating sealed humidified chamber system equilibrated with aqueous alcohol for 3 h on 3 consecutive days for two weeks. CyDye switch combined with 2-D DIGE followed by MALDI-TOF and tandem MS/MS were utilized. Validation was performed using Western immunoblot analysis. Chronic binge-like alcohol significantly (P<0.05) decreased 30 proteins and increased 19 others. Gene-enrichment and functional annotation cluster analysis revealed significant enrichment (P<0.05) in three categories: glutathione S transferase, thioredoxin, and vesicle transport-related. Furthermore, alcohol differentially altered proteins with certain isoforms being downregulated while others were upregulated. In summary, binge alcohol has specific effects on the maternal uterine proteome, especially those related to oxidative stress. The current study also demonstrates a great need to utilize proteomic approaches for diagnostic, mechanistic and therapeutic aspects of FASD.

Changes in tumor growth and metastatic capacities of J82 human bladder cancer cells suppressed by down-regulation of calreticulin expression

Bladder cancer is a common urothelial cancer. Through proteomic approaches, calreticulin (CRT) was identified and proposed as a urinary marker for bladder cancer. CRT is a multifunctional molecular chaperone that regulates various cellular functions such as Ca(2+) homeostasis and cell adhesion. CRT is overexpressed in various cancers, but its mechanism of action in the development of bladder tumors remains unclear. We generated J82 bladder cancer cells lines that either stably overexpressed or knocked down CRT to investigate the physiological effects of CRT on bladder tumors. Compared with the transfected control vector cells, the knockdown of CRT suppressed cell proliferation, migration, and attachment, whereas overexpression of CRT enhanced cell migration and attachment. We further demonstrated that the phosphorylation status of focal adhesion kinase and paxillin, important regulators of the focal adhesion complex, was also regulated in these cells. In contrast, phosphorylation of Src, a protein tyrosine kinase reported to be affected by CRT, was not significantly different between the control and CRT-RNAi groups. Most importantly, we observed that tumors derived from J82 CRT-RNAi cells were significantly smaller and had fewer metastatic sites in the lung and liver in vivo than did transfected control vector cells. In conclusion, our results suggest that alteration of CRT expression levels might affect bladder cancer progression in vitro and in vivo.

Global expression study in colorectal cancer on proteins with alkaline isoelectric point by two-dimensional difference gel electrophoresis

Colorectal cancer is one of the leading causes of cancer death worldwide. To identify candidates for biomarkers and therapeutic targets, we investigated the proteome of colorectal cancer tissues. Using 2D-DIGE in combination with our original large format electrophoresis apparatus, we compared surgically resected normal and tumor tissues from 53 patients with colorectal cancer. We focused on proteins with an alkaline pI using IPG gels for the alkaline range. We observed 1687 protein spots, and found 100 spots with statistical (p<0.01) and significant (>2-fold) differences between the normal and the tumor tissue groups. Among these 100 protein spots, five showed a different intensity between tumor tissues from the stage-II and the stage-III patients. MS experiments revealed that these 100 protein spots corresponded to 58 unique proteins. These included six proteins which had not been previously reported to be associated with colorectal cancer. Among these proteins, five were not reported in any type of malignancy. IEF/western blotting confirmed the differences in protein expression between the normal and the tumor tissues. These results may provide an insight for biomarker development and drug target discovery in colorectal cancer.

Cowpea mosaic virus nanoparticles target surface vimentin on cancer cells

AIMS

Vimentin, a type III intermediate filament, is upregulated during epithelial-mesenchymal transition and tumor progression. Vimentin is surface-expressed on cells involved in inflammation; the function remains unknown. We investigated the expression of surface vimentin on cancer cells and evaluated targeting nanoparticles to tumors exploiting vimentin.

MATERIALS & METHODS

Cowpea mosaic virus nanoparticles that interact with surface vimentin were used as probes. Tumor homing was tested using the chick chorioallantoic membrane model with human tumor xenografts.

RESULTS & DISCUSSION

Surface vimentin levels varied during cell cycle and among the cell lines tested. Surface vimentin expression correlated with cowpea mosaic virus uptake, underscoring the utility of cowpea mosaic virus to detect invasive cancer cells. Targeting to tumor xenografts was observed; homing was based on the enhanced permeability and retention effect. Our data provide novel insights into the role of surface vimentin in cancer and targeting nanoparticles in vivo.

S100A4 over-expression underlies lymph node metastasis and poor prognosis in colorectal cancer

AIM: To develop lymph node metastasis (LNM)-associated biomarkers for colorectal cancer (CRC) using quantitative proteome analysis.

METHODS: Differences in protein expression between primary CRC with LNM (LNM CRC) and without LNM (non-LNM CRC) were assessed using methyl esterification stable isotope labeling coupled with 2D liquid chromatography followed by tandem mass spectrometry (2D-LC-MS/MS). The relationship to clinicopathological parameters and prognosis of candidate biomarkers was examined using an independent sample set.

RESULTS: Forty-three proteins were found to be differentially expressed by at least 2.5-fold in two types of CRC. S100A4 was significantly upregulated in LNM CRC compared with non-LNM CRC, which was confirmed by Western blotting, immunohistochemistry and real-time quantitative polymerase chain reaction. Further immunohistochemistry on another 112 CRC cases showed that overexpression of S100A4 frequently existed in LNM CRC compared with non-LNM CRC (P < 0.001). Overexpression of S100A4 was significantly associated with LNM (P < 0.001), advanced TNM stage (P < 0.001), increased 5-year recurrence rate (P < 0.001) and decreased 5-year overall survival rate (P < 0.001). Univariate and multivariate analyses indicated that S100A4 expression was an independent prognostic factor for recurrence and survival of CRC patients (P < 0.05).

CONCLUSION: S100A4 might serve as a powerful biomarker for LNM and a prognostic factor in CRC.

An informatics-assisted label-free approach for personalized tissue membrane proteomics: case study on colorectal cancer

We developed a multiplexed label-free quantification strategy, which integrates an efficient gel-assisted digestion protocol, high-performance liquid chromatography tandem MS analysis, and a bioinformatics alignment method to determine personalized proteomic profiles for membrane proteins in human tissues. This strategy provided accurate (6% error) and reproducible (34% relative S.D.) quantification of three independently purified membrane fractions from the same human colorectal cancer (CRC) tissue. Using CRC as a model, we constructed the personalized membrane protein atlas of paired tumor and adjacent normal tissues from 28 patients with different stages of CRC. Without fractionation, this strategy confidently quantified 856 proteins (≥2 unique peptides) across different patients, including the first and robust detection (Mascot score: 22,074) of the well-documented CRC marker, carcinoembryonic antigen 5 by a discovery-type proteomics approach. Further validation of a panel of proteins, annexin A4, neutrophils defensin A1, and claudin 3, confirmed differential expression levels and high occurrences (48–70%) in 60 CRC patients. The most significant discovery is the overexpression of stomatin-like 2 (STOML2) for early diagnostic and prognostic potential. Increased expression of STOML2 was associated with decreased CRC-related survival; the mean survival period was 34.77 ± 2.03 months in patients with high STOML2 expression, whereas 53.67 ± 3.46 months was obtained for patients with low STOML2 expression. Further analysis by ELISA verified that plasma concentrations of STOML2 in early-stage CRC patients were elevated as compared with those of healthy individuals (p < 0.001), suggesting that STOML2 may be a noninvasive serological biomarker for early CRC diagnosis. The overall sensitivity of STOML2 for CRC detection was 71%, which increased to 87% when combined with CEA measurements. This study demonstrated a sensitive, label-free strategy for differential analysis of tissue membrane proteome, which may provide a roadmap for the subsequent identification of molecular target candidates of multiple cancer types.

Identification of biomarkers to improve diagnostic sensitivity of sporadic colorectal cancer in patients with low preoperative serum carcinoembryonic antigen by clinical proteomic analysis

BACKGROUND

Colorectal cancer (CRC) is the third most common type of cancer worldwide. Carcinoembryonic antigen (CEA) assays usually give false negative results. To improve the diagnosis of primary sporadic CRC, there is an urgent need to identify new biomarkers.

METHODS

We used laser pressure catapulting and proteomics to analyze overexpressed cancer associated proteins from 48 sporadic CRC patients with low preoperative serum CEA (LPSC) (<5 ng/ml). Real-time Q-PCR was used to identify the target gene transcripts. Immunoblots were carried out to validate the biomarkers.

RESULTS

Alpha-enolase, HSP27 and macrophage migration inhibitory factor (MIF) were overexpressed in all tumor tissues from 48 LPSC CRC patients, as assessed by 2DE image analysis. The genes were also overexpressed at the transcript level in all tumor tissues from the same patients. In the immunoblot assay, only serum levels of Alpha-enolase and MIF were significantly overexpressed in the LPSC group compared to the mean levels in the control group. Combined with the determinations of preoperative CEA levels, screening for serum Alpha-enolase and MIF were shown to improve the diagnosis of primary CRC.

CONCLUSIONS

Serum Alpha-enolase and MIF may be potential biomarkers that can be used to improve clinical predication of primary CRC with LPSC.

The differential expression of aqueous soluble proteins in breast normal and cancerous tissues in relation to stage and grade of patients

Breast cancer is a leading cause of female deaths worldwide. In Malaysia, it is the most common form of female cancer while Infiltrating ductal carcinoma (IDC) is the most common form of breast cancer. A proteomic approach was used to identify changes in the protein profile of breast cancerous and normal tissues. The patients were divided into different cohorts according to tumour stage and grade. We identified twenty-four differentially expressed hydrophilic proteins. A few proteins were found significantly related to various stages and grades of IDC, amongst which were SEC13-like 1 (isoform b), calreticulin, 14-3-3 protein zeta, and 14-3-3 protein eta. In this study, we found that by defining the expression of the proteins according to stages and grades of IDC, a significant relationship between the expression of the proteins with the stage or grade of IDC can be established, which increases the usefulness of these proteins as biomarkers for IDC.

Clinicopathological significance of calreticulin in breast invasive ductal carcinoma

Calreticulin is a chaperone protein located in the lumen of the endoplasmic reticulum. The association of calreticulin with pathological conditions such as autoimmune disorders and certain types of cancer have been reported. However, little is known about its role in the pathogenesis of breast cancer. The aim of this study was to determine the expression of calreticulin in vitro and correlate its expression levels in breast cancer tissue samples with clinicopathological parameters. Calreticulin expression was evaluated in MCF-7 and MDA-MB-231 breast cancer cells by real-time RT-PCR, Western blot, immunohistochemistry, and immunofluorescence staining. Patient tissue microarrays were constructed from 228 breast cancer specimens for immunohistochemical analysis. The in vitro study showed a higher calreticulin expression in more aggressive MDA-MB-231 cells as compared with MCF-7 cells at both mRNA and protein levels. In all, 227 out of 228 breast cancer samples exhibited calreticulin staining in at least 5% of the cancer cells. Calreticulin immunostaining was observed to be localized to the cytoplasm of the cancer cells. Regression analysis of calreticulin immunostaining in the tissue microarrays revealed that its expression was positively correlated to logarithm of (log) tumor size (P=0.046) and development of distant metastasis (P=0.017). Multivariate analysis confirmed calreticulin expression as an independent predictor of log tumor size and occurrence of distant metastasis. The data suggest that calreticulin expression is associated with more advanced tumors and is a potential prognostic biomarker.

Identification of phospholipid scramblase 1 as a biomarker and determination of its prognostic value for colorectal cancer

The purpose of this study was to examine the expression of phospholipid scramblase 1 (PLSCR1) in tumor tissues and plasma specimens of patients with colorectal cancer (CRC), as well as analyze its association with clinical parameters. The expression levels of PLSCR1 protein in 104 matched CRC and adjacent normal tissue sections and 50 pairs of CRC tissue blocks were determined by use of immunohistochemical and Western blot analyses, respectively. To evaluate the diagnostic potential of PLSCR1, the plasma levels of PLSCR1 were investigated in 111 additional subjects (59 CRC patients and 52 healthy controls) by Western blot. PLSCR1 was overexpressed in malignant adenocarcinoma tissues compared with normal colorectal mucosa (P < 0.001). In addition, the plasma level of PLSCR1 was not only significantly elevated in CRC patients compared with healthy individuals (P < 0.001), but it was also substantially increased in early stage CRC (P < 0.001). Importantly, the overall sensitivity and specificity of PLSCR1 for CRC detection were 80% and 59.6%, respectively. The area under the ROC curve of PLSCR1 for CRC diagnosis is 0.75, which increases to 0.8 if combined with the measurement of carcinoembryonic antigen. Univariate analysis with the Cox regression model revealed that elevated PLSCR1 expression indicated a poor prognosis for CRC. This study showed that PLSCR1 protein levels were significantly elevated in both the cancer tissue and plasma of CRC patients. Moreover, the plasma levels of PLSCR1 were significantly elevated in patients with early stage CRC compared with healthy individuals, suggesting that PLSCR1 might be used as a noninvasive serological diagnostic and prognostic biomarker for CRC.

Molecular markers for early detection

A common belief is that the earlier that cancer is detected, the better the chance exists for reduced mortality and morbidity. The advent of new and emerging molecular, genetic, and imaging technologies has broadened the possible strategies for early detection and prevention, but a beneficial impact on mortality needs to be supported by clinical evidence. Molecular markers are being identified that are enhancing our ability to predict and detect cancer before it develops and at the earliest signs of impending carcinogenic transformation. Of the innumerable molecular markers in development, a standalone early detection marker with acceptable sensitivity and specificity is available for bladder cancer, although for most cancer sites there are promising avenues of research that will likely produce results in the next decade. The perfect molecular marker would be one that is inherently related to the disease, specifically to the processes of malignant tumorigenesis or to the defense mechanisms of the individual. For example, mutations associated with increased cancer risk often produce gene products that interfere with tumor-suppressor pathways (eg, DNA repair or cell-cycle control) or support oncogenic pathways (eg, through genetic instability or silencing the apoptotic pathway). Finding molecular markers associated with these processes, and where in the process they produce their actions, can lead to interventions based on maintaining support for the normal process and interrupting the action of the products of the mutation. The search for molecular markers for cancer prevention and early detection presents a formidable challenge that requires a systematic and scientifically sound validation process. The search encompasses a broad range of scientific disciplines, including biochemistry, genetics, histology, immunology, informatic technologies, and epidemiology; strategies to identify and understand molecular markers are approached with multidisciplinary teams focused on understanding the mechanistic basis of cancer and the processes and pathways that underlie carcinogenesis.

Proteomic analysis of biopsied human colonic mucosa

BACKGROUND AND OBJECTIVES

: Pediatric gastroenterologists have a unique opportunity to study the proteins in the gastrointestinal tract. To assess the power of proteomic studies we compared 2 methods for analysis of proteins in normal human colonic mucosa: 2-dimensional gel electrophoresis (2DE) and 2-dimensional liquid chromatography (2DLC) in conjunction with mass spectrometry. We used Ingenuity Pathway Analysis to examine these proteins regarding function, location, and relation to disease.

RESULTS

: 2DLC identified 550 proteins, whereas 2DE identified 107 proteins, 18 of which were not observed with 2DLC. The function associated with the largest number of proteins for both methods was cancer (236 proteins with 2DLC, 61 proteins with 2DE). The largest group of proteins was from the cytoplasm (49.3% from 2DE and 49.1% from 2DLC). Two hundred seventy of the total 568 proteins were related to 26 different categories of human disease and 200 of these 270 were described in large intestine, 227 were described in blood, and 149 were described in serum or plasma.

CONCLUSIONS

: These methods are complementary, although many more proteins were identified with 2DLC. This suggests that 2DLC should have greater utility in examining changes in the proteome of the colonic mucosa during disease than 2DE. However, some proteins found were unique to 2DE, and thus the methods chosen for a given analysis must be matched with the proteins to be studied. When pediatric gastroenterologists use proteomic methods, there is a new opportunity to increase our understanding of the gastrointestinal tract in health and disease.

Comparison of membrane fraction proteomic profiles of normal and cancerous human colorectal tissues with gel-assisted digestion and iTRAQ labeling mass spectrometry

The aim of this study was to uncover the membrane protein profile differences between colorectal carcinoma and neighboring normal mucosa from colorectal cancer patients. Information from cellular membrane proteomes can be used not only to study the roles of membrane proteins in fundamental biological processes, but also to discover novel targets for improving the management of colorectal cancer patients. We used solvent extraction and a gel-assisted digestion method, together with isobaric tags with related and absolute quantitation (iTRAQ) reagents to label tumoral and adjacent normal tissues in a pairwise manner (n = 8). For high-throughput quantification, these digested labeled peptides were combined and simultaneously analyzed using LC-MS/MS. Using the shotgun approach, we identified a total of 438 distinct proteins from membrane fractions of all eight patients. After comparing protein expression between cancerous and corresponding normal tissue, we identified 34 upregulated and eight downregulated proteins with expression changes greater than twofold (Student's t-test, P < 0.05). Among these, the overexpression of well-established biomarkers such as carcinoembryonic antigens (CEACAM5, CEACAM6), as well as claudin-3, HLA class I histocompatibility antigen A-1, tapasin and mitochondrial solute carrier family 25A4 were confirmed by western blotting. We conclude that gel-assisted digestion and iTRAQ labeling MS is a potential approach for uncovering and comparing membrane protein profiles of tissue samples that has the potential to identify novel biomarkers.

Differential protein expression on the cell surface of colorectal cancer cells associated to tumor metastasis

Progression to metastasis is the critical point in colorectal cancer (CRC) survival. However, the proteome associated to CRC metastasis is very poorly understood at the moment. In this study, we used stable isotope labeling by amino acids in cell culture to compare two CRC cell lines: KM12C and KM12SM, representing poorly versus highly metastatic potential, to find and quantify the differences in protein expression, mostly at the cell surface level. After biotinylation followed by affinity purification, membrane proteins were separated by SDS-PAGE and analyzed using nanoflow LC-ESI-LTQ. A total of 291 membrane and membrane-associated proteins were identified with a p value<0.01, from which 60 proteins were found to be differentially expressed by more than 1.5-fold. We identified a number of cell signaling, CDs, integrins and other cell adhesion molecules (cadherin 17, junction plakoglobin (JUP)) among the most deregulated proteins. They were validated by Western blot, confocal microscopy and flow cytometry analysis. Immunohistochemical analysis of paired tumoral samples confirmed that these differentially expressed proteins were also altered in human tumoral tissues. A good correlation with a major abundance in late tumor stages was observed for JUP and 17-beta-hydroxysteroid dehydrogenase type 8 (HSD17B8). Moreover, the combined increase in JUP, occludin and F11 receptor expression together with cadherin 17 expression could suggest a reversion to a more epithelial phenotype in highly metastatic cells. Relevant changes were observed also at the metabolic level in the pentose phosphate pathway and several amino acid transporters. In summary, the identified proteins provide us with a better understanding of the events involved in liver colonization and CRC metastasis.

Heat shock protein 27: a potential biomarker for colorectal carcinoma

AIM: To find specific biomarkers for colorectal carcinoma using a proteomic method to provide clues to early diagnosis, prognosis and therapy of colorectal carcinoma as well as to understanding the molecular mechanisms governing cancer progression.

METHODS: Six colorectal carcinoma patients were included in the study. High-resolution two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were utilized for the identification of proteins differentially expressed between cancer and adjacent non-cancerous tissue. The differential expression of heat shock protein 27 (HSP27) was further verified by Western blot and immunohistochemistry.

RESULTS: Comparative analysis of 2-DE maps revealed 42 differentially expressed proteins between the two groups. Ten differential proteins were further identified by mass spectrometry, including HSP27, disulfide isomerase (DI), heterogeneous nuclear ribonucleoprotein A2/B1 (HnRNP A2/B1), triosephosphate isomerase (TIM), pyruvate kinase, etc. Western blot and immunohistochemistry analyses confirmed the overexpression of HSP27 in colorectal carcinoma. These results indicate that HSP27 may be a potential biomarker for colorectal cancer.

CONCLUSION: Many differential proteins are identified between cancer and adjacent non-cancerous tissue in patients with colorectal carcinoma. HSP27 might be a potential biomarker for early diagnosis, therapy and prognosis of colorectal carcinoma.

Novel snail1 target proteins in human colon cancer identified by proteomic analysis

Background

The transcription factor Snail1 induces epithelial-to-mesenchymal transition (EMT), a process responsible for the acquisition of invasiveness during tumorigenesis. Several transcriptomic studies have reported Snail1-regulated genes in different cell types, many of them involved in cell adhesion. However, only a few studies have used proteomics as a tool for the characterization of proteins mediating EMT.

Methodology/Principal Findings

We identified by proteomic analysis using 2D-DIGE electrophoresis combined with MALDI-TOF-TOF and ESI-linear ion trap mass spectrometry a number of proteins with variable functions whose expression is modulated by Snail1 in SW480-ADH human colon cancer cells. Validation was performed by Western blot and immunofluorescence analyses. Snail1 repressed several members of the 14-3-3 family of phosphoserine/phosphothreonine binding proteins and also the expression of the Proliferation-associated protein 2G4 (PA2G4) that was mainly localized at the nuclear Cajal bodies. In contrast, the expression of two proteins involved in RNA processing, the Cleavage and polyadenylation specificity factor subunit 6 (CPSF6) and the Splicing factor proline/glutamine-rich (SFPQ), was higher in Snail1-expressing cells than in controls. The regulation of 14-3-3ε, 14-3-3τ, 14-3-3ζ and PA2G4 by Snail1 was reproduced in HT29 colon cancer cells. In addition, we found an inverse correlation between 14-3-3σ and Snail1 expression in human colorectal tumors.

Conclusions/Significance

We have identified a set of novel Snail1 target proteins in colon cancer that expand the cellular processes affected by Snail1 and thus its relevance for cell function and phenotype.

Differential expression proteomics of human colorectal cancer based on a syngeneic cellular model for the progression of adenoma to carcinoma

This is the first differential expression proteomics study on a human syngeneic cellular in vitro progression model of the colorectal adenoma-to-carcinoma sequence, the anchorage-dependent non-tumorigenic adenoma derived cell line AA/C1 and the derived anchorage-independent and tumorigenic carcinoma cell line AA/C1/SB10C. The study is based on quantitative 2-DE and is complemented by Western blot validation. Excluding redundancies due to proteolysis and post-translational modified isoforms of over 2000 protein spots, 13 proteins were revealed as regulated with statistical variance being within the 95th confidence level and were identified by peptide mass fingerprinting in MALDI MS. Progression-associated proteins belong to the functional complexes of anaerobic glycolysis/gluconeogenesis, steroid biosynthesis, prostaglandin biosynthesis, the regulation and maintenance of the cytoskeleton, protein biosynthesis and degradation, the regulation of apoptosis or other functions. Partial but significant overlap was revealed with previous proteomics and transcriptomics studies in colorectal carcinoma. Among upregulated proteins we identified 3-HMG-CoA synthase, protein phosphatase 1, prostaglandin E synthase 2, villin 1, annexin A1, triosephosphate isomerase, phosphoserine aminotransferase 1, fumarylacetoacetate hydrolase and pyrroline-5-carboxylate reductase 1 (PYCR1), while glucose-regulated protein 78, cathepsin D, lamin A/C and quinolate phosphoribosyltransferase were downregulated.

Heterogeneous nuclear ribonucleoprotein A1 is identified as a potential biomarker for colorectal cancer based on differential proteomics technology

Colorectal cancer (CRC) is the third most common cancer worldwide and has poor prognosis. To identify the proteins involved in colorectal carcinogenesis, we employed 2-DE and MALDI-TOF/TOF-based proteomics approach to study the differentially expressed proteins in tumor and adjacent nontumor tissue samples. Samples from 10 colorectal patients were analyzed. Of the 7 significantly and consistently altered proteins identified, hnRNP A1 was one of the most significantly altered proteins and its overexpression was confirmed using RT-PCR and Western blot analyses. Immunohistochemical examination showed that the enhanced expression of hnRNP A1 was correlated with the increasing severity of colorectal tissue and the progression of the colorectal cancer, as well as UICC (International Union against Cancer) staging, histo-differentiation, recurrence and decreased survival. By developing a highly sensitive immunoassay, hnRNP A1 could be detected in human serum and was significantly elevated in CRC patients compared with healthy volunteers. We proposed that hnRNP A1 could be considered as a novel serum tumor marker for CRC that may have significance in the detection and in the management of patients with this disease. Knockdown of hnRNP A1 expression by RNA interference led to the significant suppression of the cell growth in colorectal cancer SW480 cells in vitro. These data suggested that hnRNP A1 may be a potential biomarker for early diagnosis, prognosis, and monitoring in the therapy of colorectal cancer. Further studies are needed to fully assess the potential clinical value of this biomarker candidate.

Identification of transgelin-2 as a biomarker of colorectal cancer by laser capture microdissection and quantitative proteome analysis

To search for potential protein markers of colorectal cancer (CRC), the changes in protein expression levels between microdissected tumor cells and normal mucosa epithelia were analyzed by an acetylation stable isotopic labeling method coupled with linear quadrupole ion trap fourier transform mass spectrometry (LTQ-FTMS). In total, 137 proteins were up-regulated or down-regulated significantly in cancer by at least two-fold. Based on gene ontology analysis, the largest part of differential proteins were unknown for both subcellular localization and biological process. In particular, the significant up-regulation of transgelin-2 (TAGLN2) in CRC was validated by Western blot analysis and further evaluated by immunohistochemistry in paired tumor and normal mucosa samples from 120 consecutive CRC patients, 20 adenomas, and eight synchronous hepatic metastases of CRC. TAGLN2 expression was frequently observed in cancer cells, precancerous lesions, and hepatic metastases, whereas in normal epithelia expression was rarely observed. The overexpression of TAGLN2 was associated with lymph node and distant metastasis, advanced clinical stage (P < 0.001), and shorter overall survival in CRCs. Cox regression analysis indicated that high tumor-TAGLN2 expression represents an independent prognostic factor. Consequently, over-expression of TAGLN2 may serve as a new biomarker for predicting progression and prognosis of CRC.

Colorectal cancer proteomics, molecular characterization and biomarker discovery

Colorectal cancer (CRC) is a widespread disease, whose major genetic changes and mutations have been well characterized in the sporadic form. Much less is known at the protein and proteome level. Still, CRC has been the subject of multiple proteomic studies due to the urgent necessity of finding clinically relevant markers and to elucidate the molecular mechanisms underlying the progression of the disease. These proteomic approaches have been limited by different technical issues, mainly related with sensitivity and reproducibility. However, recent advances in proteomic techniques and MS systems have rekindled the quest for new biomarkers in CRC and an improved molecular characterization. In this review, we will discuss the application of different proteomic approaches to the identification of differentially expressed proteins in CRC. In particular, we will make a critical assessment about the use of 2-D DIGE, MS and protein microarray technologies, in their different formats, to identify up- or downregulated proteins and/or autoantibodies profiles that could be useful for CRC characterization and diagnosis. Despite a wide list of potential biomarkers, it is clear that more scientific efforts and technical advances are still needed to cover the range of low-abundant proteins, which may play a key role in CRC diagnostics and progression.

Application of proteomics in colorectal cancer research

Colorectal cancer is one of the most common malignant tumors in China. Its morbidity and mortality are increasing year by year. The emergence of proteomics has pushed colorectal cancer research forward. In this article, we will review the application of proteomics in the study of the diagnosis, pathogenesis and treatment of colorectal cancer.

Identification of HSP27 as a potential tumor marker for colorectal cancer by the two-dimensional polyacrylamide gel electrophoresis

The identification of specific biomarkers for colorectal cancer would provide the basis for early diagnosis, prognosis, therapy, as well as clues for understanding the molecular mechanisms governing cancer progression. This study was designed to use comparative proteomics technology to find the differentially expressed proteins between human colorectal carcinoma and the corresponding normal tumor-adjacent colorectal tissues. We have used the highly sensitive two-dimensional gel electrophoresis (2-DE) coupled with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) for the identification of proteins differentially expressed in tumoral and neighboring normal mucosa. We have detected differences in abundance of 42 proteins with statistical variance of the tumor versus normal spot volume ratio within the 95th confidence level (Student's t-test; P < 0.05). 10 out of 42 analyzed proteins were unambiguously identified by MS coupled with database interrogation as being differentially expressed in colorectal cancer. Of the 10 newly implicated proteins, HSP27 was chosen for detailed analysis. Preliminary studies demonstrated that the differentially expressed proteins found by 2-DE could be confirmed and validated by western blotting and immunohistochemistry analyses in those few cases. The results suggest that HSP27 might be a potential biomarker for early diagnosis, prognosis, monitoring in the therapy of colorectal carcinoma.

Identification of cancer-associated proteins by proteomics and downregulation of β-tropomyosin expression in colorectal adenoma and cancer

Elucidating the molecular mechanism underlying the development of adenoma, the major precursor lesion of colorectal cancer (CRC), would provide a basis for early detection, prevention as well as treatment of CRC. Using the highly sensitive 2-D DIGE method coupled with MS, we identified 24 differentially expressed proteins in adenoma tissues compared with matched normal colonic mucosa and CRC tissues. Fifteen proteins were downregulated and three proteins were upregulated in adenoma tissues when compared with individual-matched normal colonic mucosa. Five proteins were downregulated, while one protein was upregulated in adenoma tissues when compared with matched CRC tissues. A protein, β-tropomyosin (TM-β), recently suggested to be a biomarker of esophageal squamous carcinoma, was downregulated in both adenoma and CRC tissues. Additionally, the reduction in the level of TM-β in adenoma and CRC tissues was further validated by Western blotting (p<0.05) and RT-PCR (p<0.001). Our findings suggest that downregulation of TM-β is involved in the early development of CRC and that differentially expressed proteins might serve as potential biomarkers for detection of CRC.

Constitutively active MEK1 is sufficient to induce epithelial-to-mesenchymal transition in intestinal epithelial cells and to promote tumor invasion and metastasis

Constitutive activation of the MAP kinase kinase MEK1 induces oncogenic transformation in intestinal epithelial cells. Loss of cell-cell adhesion followed by the dissociation of epithelial structures is a prerequisite for increased cell motility and tumor invasion. This phenotypic switch is designated epithelial-to-mesenchymal transition (EMT). EMT also plays an important role in determining the dissemination of tumors. However, the role of MEK1 in intestinal EMT, tumor invasion and metastasis has not been elucidated. To determine the functions of activated MEK1 in intestinal tumorigenesis, we established intestinal epithelial cell lines that overexpress wild-type MEK1 (wtMEK) or activated MEK1 (caMEK). Our results indicate that expression of caMEK is sufficient to induce EMT as confirmed with the induction of N-cadherin, vimentin, Snail1 and Snail2, whereas a reduction in E-cadherin, occludin, ZO-1 and cortical F-actin was noted. The Snail1 and Snail2 promoter analyses revealed that Egr-1 and Fra-1, an AP-1 protein, are responsible for MEK1-induced Snail1 and Snail2 expression, respectively. Cells expressing activated MEK1 clearly acquired an invasive capacity when compared to wtMEK-expressing cells. Zymography studies confirmed elevated levels of MMP2 and MMP9 activities in media of caMEK-expressing cells. Importantly, cells expressing activated MEK1 induced tumors with short latency in correlation with their ability to induce experimental metastasis in vivo and to express factors known to promote colorectal cancer cell metastasis. In conclusion, our results demonstrate, for the first time, that constitutive activation of MEK1 in intestinal epithelial cells is sufficient to induce an EMT associated with tumor invasion and metastasis.

Approaches to biomarkers in human colorectal cancer: looking back, to go forward

Like all human cancers, colorectal cancer is a complicated disease. While a mature body of research involving colorectal cancer has implicated the putative sequence of genetic alterations that trigger the disease and sustain its progression, there is a surprising paucity of well-validated, clinically useful diagnostic markers of this disease. For prognosis or guiding therapy, single gene-based markers of colorectal cancer often have limited specificity and sensitivity. Genome-wide analyses (microarrays) have been used to propose candidate patterns of gene expression that are prognostic of outcome or predict the tumor's response to a therapy regimen; however, these patterns frequently do not overlap, and this has raised questions concerning their use as biomarkers. The limitation of gene-expression approaches to marker discovery occurs because the change in mRNA expression across tumors is highly variable and, alone, accounts for a limited variability of the phenotype, such as with cancer. More robust and accurate markers of cancer will result from integrating all the information we have about the cell: genomics, proteomics and interactomics. This article will discuss traditional markers in colorectal cancer, both genomic and proteomic, including their respective approaches and limitations, then conclude with examples of systems biology-based approaches for candidate marker discovery, and discuss how this approach is reshaping our view of a biomarker.

Identification of tumor-associated autoantigens for the diagnosis of colorectal cancer in serum using high density protein microarrays

There is a mounting evidence of the existence of autoantibodies associated to cancer progression. Antibodies are the target of choice for serum screening because of their stability and suitability for sensitive immunoassays. By using commercial protein microarrays containing 8000 human proteins, we examined 20 sera from colorectal cancer (CRC) patients and healthy subjects to identify autoantibody patterns and associated antigens. Forty-three proteins were differentially recognized by tumoral and reference sera (p value <0.04) in the protein microarrays. Five immunoreactive antigens, PIM1, MAPKAPK3, STK4, SRC, and FGFR4, showed the highest prevalence in cancer samples, whereas ACVR2B was more abundant in normal sera. Three of them, PIM1, MAPKAPK3, and ACVR2B, were used for further validation. A significant increase in the expression level of these antigens on CRC cell lines and colonic mucosa was confirmed by immunoblotting and immunohistochemistry on tissue microarrays. A diagnostic ELISA based on the combination of MAPKAPK3 and ACVR2B proteins yielded specificity and sensitivity values of 73.9 and 83.3% (area under the curve, 0.85), respectively, for CRC discrimination after using an independent sample set containing 94 sera representative of different stages of progression and control subjects. In summary, these studies confirmed the presence of specific autoantibodies for CRC and revealed new individual markers of disease (PIM1, MAPKAPK3, and ACVR2B) with the potential to diagnose CRC with higher specificity and sensitivity than previously reported serum biomarkers.

Identification of S100A8 and S100A9 as serological markers for colorectal cancer

In search of novel serological protein biomarkers for human colorectal cancer (CRC), we analyzed CRC tissues using two-dimensional difference in-gel electrophoresis (2D-DIGE) on a narrow range IPG strip (pH 5.5-6.7). By comparing tumor tissues with matched normal tissues in a pairwise manner (n = 6), we identified 34 up-regulated and 17 down-regulated spots with intensity changes greater than 2-fold (Student's t-test, p < 0.05). Expression of both mRNA and protein levels of four proteins, adenosylhomocysteinase, Nm23-H1, S100A8 and S100A9, in CRC tissues was further evaluated by semiquantitative RT-PCR and Western blot analysis. The results revealed that all four proteins were elevated in the tumor tissues. We also confirmed, by immunohistochemistry, that adenosylhomocysteinase and Nm23-H1 were overexpressed in tumor cell cytoplasm and that S100A8 and S100A9 proteins were strongly expressed in tumor infiltrating immune cells. Western blot analysis with fractionated plasma samples showed that S100A8 and S100A9 were significantly increased in the plasma of CRC patients (n = 77) and colorectal adenoma patients (n = 11), compared to healthy controls (n = 21). The area under a receiver operating characteristic (ROC) curve was 0.91 for S100A8 and 0.89 for S100A9, which was superior to the established tumor marker carcinoembryonic antigen with 0.78 for the area under the ROC curve. Some patients with inflammatory diseases such as pancreatitis also showed elevated levels of the proteins. Importantly, in comparison to the control group, both proteins showed a remarkable change at the early stage of cancer. Therefore, we suggest S100A8 and S100A9 as candidates for serological biomarkers in combination with other serum markers that aid CRC diagnosis.

Identification of proteomic changes during human liver development by 2D-DIGE and mass spectrometry

BACKGROUND/AIMS

The aim of this study was to identify human liver proteins that are associated with different stages of liver development.

METHODS

We collected liver samples from 14 fetuses between 14 and 41 weeks of development, one child and four adults. Proteins which exhibited consistent and significant variations during development by two-dimensional differential in gel electrophoresis (2D-DIGE) were subjected to peptide mass fingerprint analysis by MALDI-TOF mass spectrometry. Real-time PCR analysis confirmed, at the transcriptional level, the data obtained by the proteomic approach.

RESULTS

Among a total of 80 protein spots showing differential expression, we identified 42 different proteins or polypeptide chains, of which 26 were upregulated and 16 downregulated in developing in comparison to adult liver. These proteins could be classified in specific groups according to their function. By comparing their temporal expression profiles, we identified protein groups that were associated with different developmental stages of human fetal liver and suggest that the changes in protein expression observed during the 20- to 36-week time window play a pivotal role in liver development.

CONCLUSIONS

The identification of these proteins may represent good markers of human liver and stem cells differentiation.

Proteomics identification of desmin as a potential oncofetal diagnostic and prognostic biomarker in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer worldwide and has poor prognosis. To identify the oncofetal proteins involved in CRC carcinogenesis, differentially expressed proteins among fetal colorectal tissues, CRC, and the paired tumor-adjacent normal colorectal tissues were investigated by a two-dimensional gel electrophoresis and MALDI-TOF/TOF-based proteomics approach. 42 protein spots were differentially expressed among these tissues, and 22 proteins were identified by MS analysis. Desmin and zinc finger protein 829 were found to be elevated in CRC tissue and fetal colorectal tissue compared with normal colorectal tissue. The elevated expression of desmin in CRC tissue and different developmental stages of fetus colon was confirmed by RT-PCR and Western blot analysis. Immunohistochemical analysis showed that the elevated expression of desmin was correlated with the severity and differentiation of CRC and decreased survival rate of CRC patients. Finally by developing a highly sensitive immunoassay, desmin could be detected in human serum and was significantly elevated in CRC patients compared with healthy volunteers. We propose that desmin be considered a potential oncofetal serum tumor marker for CRC that may have significance in the detection of patients with CRC.