Tumor markers and colorectal cancer: utility in management

Reconstruction of the tumor spatial microenvironment along the malignant-boundary-nonmalignant axis

Although advances in spatial transcriptomics (ST) enlarge to unveil spatial landscape of tissues, it remains challenging to delineate pathology-relevant and cellular localizations, and interactions exclusive to a spatial niche (e.g., tumor boundary). Here, we develop Cottrazm, integrating ST with hematoxylin and eosin histological image, and single-cell transcriptomics to delineate the tumor boundary connecting malignant and non-malignant cell spots in tumor tissues, deconvolute cell-type composition at spatial location, and reconstruct cell type-specific gene expression profiles at sub-spot level. We validate the performance of Cottrazm along the malignant-boundary-nonmalignant spatial axis. We identify specific macrophage and fibroblast subtypes localized around tumor boundary that interacted with tumor cells to generate a structural boundary, which limits T cell infiltration and promotes immune exclusion in tumor microenvironment. In this work, Cottrazm provides an integrated tool framework to dissect the tumor spatial microenvironment and facilitates the discovery of functional biological insights, thereby identifying therapeutic targets in oncologic ST datasets.

Proteomic profiling reveals key cancer progression modulators in shed microvesicles released from isogenic human primary and metastatic colorectal cancer cell lines

Extracellular vesicles comprise two main classes - exosomes and shed microvesicles (sMVs). Whilst much is known about exosome cargo content and functionality, sMVs are poorly understood. Here, we describe the large-scale purification of sMVs released from primary (SW480) and metastatic (SW620) human isogenic colorectal cancer (CRC) cell lines using a combination of differential ultracentrifugation and isopycnic iodixanol density centrifugation. The yield of SW480-sMVs and SW620-sMVs was 0.75 mg and 0.80 mg, respectively. Both SW480-/SW620-sMVs are heterogeneous in size (100-600 nm diameter) and exhibit identical buoyant densities (1.10 g/mL). In contrast to exosomes, sMVs are ALIX^-, TSG101^-, CD63^- and CD9^-. Quantitative mass spectrometry identified 1295 and 1300 proteins in SW480-sMVs and SW620-sMVs, respectively. Gene Ontology enrichment analysis identified 'cell adhesion' (CDH1, OCLN, CTN families), 'signalling pathway' (KRAS, NRAS, MAPK1, MAP2K1), and 'translation/RNA related' processes (EIF, RPL, HNRNP families) in both sMV types. Strikingly, SW480- and SW620-sMVs exhibit distinct protein signatures - SW480-sMVs being enriched in ITGA/B, ANXA1, CLDN7, CD44 and EGFR/NOTCH signalling networks, while SW620-sMVs are enriched in PRKCA, MACC1, FGFR4 and MTOR/MARCKS signalling networks. Both SW480- and SW620-sMVs are taken up by NIH3T3 fibroblasts resulting in similar cell invasion capability. This study provides, for the first time, molecular insights into sMVs and CRC biology.

SMAD2 and the Relationship of Colorectal Cancer to Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) affecting the colon [Crohn's disease (CD) and ulcerative colitis (UC)] are associated with an increased risk of colorectal cancer (CRC). Our previous work using oligonucleotide array data indicated that SMAD2 was significantly underexpressed in UC dysplastic tissue compared to benign UC. The aim of this current study was to determine whether single nucleotide polymorphisms (SNPs) within the SMAD2 gene are associated with IBD dysplasia/cancer. We performed an SNP haplotype-based case-control association study. Leukocyte DNA was obtained from 489 unrelated Caucasians (158 UC, 175 CD, 71 CRC, 85 controls). Eleven SNPs were genotyped. All 11 SNPs were in Hardy-Weinberg equilibrium in the control population. Strong linkage disequilibrium was observed among nearly all SMAD2 SNPs. There were no significant associations between SMAD2 allele or haplotype frequencies. Power calculations indicated good power for single-marker analysis (>0.8) and reasonably good power against effects of 0.1–0.15 for haplotype analysis. SMAD2 SNPs were not associated with the development of IBD dysplasia/cancer. This incongruity between our previous microarray data and the findings from this genotype study may be attributed to mechanisms such as alternative splicing of pre-mRNA SMAD2 and/or cross talk with other cellular pathways.

Single Domain Antibodies as New Biomarker Detectors

Biomarkers are defined as indicators of biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. Biomarkers have been widely used for early detection, prediction of response after treatment, and for monitoring the progression of diseases. Antibodies represent promising tools for recognition of biomarkers, and are widely deployed as analytical tools in clinical settings. For immunodiagnostics, antibodies are now exploited as binders for antigens of interest across a range of platforms. More recently, the discovery of antibody surface display and combinatorial chemistry techniques has allowed the exploration of new binders from a range of animals, for instance variable domains of new antigen receptors (V_NAR) from shark and variable heavy chain domains (V_HH) or nanobodies from camelids. These single domain antibodies (sdAbs) have some advantages over conventional murine immunoglobulin owing to the lack of a light chain, making them the smallest natural biomarker binders thus far identified. In this review, we will discuss several biomarkers used as a means to validate diseases progress. The potential functionality of modern singe domain antigen binders derived from phylogenetically early animals as new biomarker detectors for current diagnostic and research platforms development will be described.

Imatinib Inhibits the Renewal and Tumorigenicity of CT-26 Colon Cancer Cells after Cytoreductive Treatment with Doxorubicin

Conventional anti-cancer drugs preferentially eliminate differentiated cancer cells but those cells that are spared (i.e. cancer stem cells: CSC), initiate recurrence. We tested whether drugs that target receptor tyrosine kinases (RTKs) involved in developmental signaling cascades and activated in CSC, could be used to silence and/or to eliminate colorectal cancer cells refractory to conventional treatment with cytoreductive drugs. A sequential treatment model was thereby developed with doxorubicin (DOX) and imatinib. CT-26 mouse colon carcinoma cells were pre-treated with DOX to select DOX-refractory cells with CSC properties, which were then subsequently treated with RTK inhibitor imatinib, where their regrowth was found to be inhibited. Under both normoxic and hypoxic conditions, imatinib potently inhibited clonogenicity of DOX-refractory CT-26 cells. Treatment with DOX did not eliminate tumorigenic CT-26 cells, since CT-26 cells pre-exposed to DOX in vitro, when inoculated subcutaneously, induced tumors in 90 % of mice, as opposed to a 100 % rate in the case of chemonaive CT-26 cells. In mice inoculated with chemonaive CT-26 cells, tumor formation was not prevented by imatinib. However, imatinib prevented tumor formation in 50 % of mice inoculated with CT-26 cells pre-exposed to DOX in vitro, with the remaining 50 % mice showing delayed tumor formation. These results suggest that the sequential use of the drug imatinib, as a drug targeting cancer cells expressing stem cell features after conventional cytoreductive treatment, is a promising future strategy for preventing tumor recurrence.

Elevated CA19-9 as the Most Significant Prognostic Factor in Locally Advanced Rectal Cancer Following Neoadjuvant Chemoradiotherapy

It remains controversial regarding the prognostic significance of carbohydrate antigen 19-9 (CA19-9) for locally advanced rectal cancer (LARC) (T3-4/N+) patients with neoadjuvant chemoradiotherapy (neo-CRT). And it is unknown whether CA19-9 can identify patients who may benefit from adjuvant chemotherapy.Overall, 303 LARC patients with neo-CRT between 2004 and 2010 were recruited. Overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and local recurrence-free survival across pretreatment CA19-9 were estimated by Kaplan-Meier method and Cox regression model.In univariate analysis, elevated CA19-9 (>35 U/mL) was significantly correlated with poor OS (P = 0.003), DFS (P = 0.001), and DMFS (P = 0.039). Adjusting for the known covariates, CA19-9 was significantly associated with OS (HR = 1.86, 95% CI 1.03-3.34, P = 0.039) and DFS (HR = 1.74, 95% CI 1.08-2.80, P = 0.024). In the elevated CA19-9 subgroup, patients with adjuvant chemotherapy got much better OS (P < 0.001) and DFS (P = 0.016) than those without. In consideration of both CA19-9 and carcinoembryonic antigen (CEA), we found that patients with both elevated CA19-9 and CEA (>5 ng/mL) got the worst OS (P = 0.021) and DFS (P = 0.006), and significantly benefited from adjuvant chemotherapy in OS (P < 0.001) and DFS (P = 0.026).Pretreatment CA19-9 level is a significant prognostic indicator in patients with LARC following neo-CRT. The addition of CA19-9 to CEA is valuable to discriminate the appropriate patients for adjuvant chemotherapy.

Ectokinases as novel cancer markers and drug targets in cancer therapy

While small-molecule kinase inhibitors became the most prominent anticancer drugs, novel combinatorial strategies need to be developed as the fight against cancer is not yet won. We review emerging literature showing that the release of several ectokinases is significantly upregulated in body fluids from cancer patients and that they leave behind their unique signatures on extracellular matrix (ECM) proteins. Our analysis of proteomic data reveals that fibronectin is heavily phosphorylated in cancer tissues particularly within its growth factor binding sites and on domains that regulate fibrillogenesis. We are thus making the case that cancer is not only a disease of cells but also of the ECM. Targeting extracellular kinases or the extracellular signatures they leave behind might thus create novel opportunities in cancer diagnosis as well as new avenues to interfere with cancer progression and malignancy.

Proteomic analysis of colorectal cancer: discovering novel biomarkers

Colorectal cancer is one of the most common cancers in the Western world. When detected at an early stage, the majority of cancers can be cured with current treatment modalities. However, most cancers present at an intermediate stage. The discovery of sensitive and specific biomarkers has the potential to improve preclinical diagnosis of primary and recurrent colorectal cancer, and holds the promise of prognostic and therapeutic application. Current biomarkers such as carcinoembryonic antigen lack sensitivity and specificity for general population screening. This review aims to highlight the role of current proteomic technologies in the discovery and validation of potential biomarkers with a view to translation to the clinic.

Comprehensive fluorogenic derivatization-liquid chromatography/tandem mass spectrometry proteomic analysis of colorectal cancer cell to identify biomarker candidate

Existing colorectal cancer biomarkers are insufficient for providing a quick and accurate diagnosis, which is critical for a good prognosis. More appropriate biomarkers are thus needed. To identify new colorectal cancer biomarker candidates, we conducted a comprehensive differential proteomic analysis of six cancer cell lines and a normal cell line, utilizing a fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) approach. Two sets of intracellular biomarker candidates were identified: one for colorectal cancer, and the other for metastatic colorectal cancer. Our results suggest that cooperative expression of FABP5 and cyclophilin A might be linked to Her2 signaling. Upregulation of LDHB and downregulation of GAPDH suggest the existence of a specific nonglycolytic energy production pathway in metastatic colorectal cancer cells. Downregulation of 14-3-3ζ/δ, cystatin-B, Ran and thioredoxin could be a result of their secretion, which then stimulates metastasis via activity in the sera and ascitic fluids. We propose a possible flow scheme to describe the dynamics of protein expression in colorectal cancer cells leading to tumor progression and metastasis via cell proliferation, angiogenesis, disorganization of actin filaments and epithelial-mesenchymal transition. Our results suggest that colorectal tumor progression may be regulated by signaling mediated by Her2, hypoxia, and TGFβ.

Cytoplasmic CD133 expression is a reliable prognostic indicator of tumor regression after neoadjuvant concurrent chemoradiotherapy in patients with rectal cancer

BACKGROUND

Despite development in therapeutic strategies, such as neoadjuvant concurrent chemoradiotherapy (CCRT), the prognosis of colorectal cancer remains relatively poor. Cancer stem cells (CSC) with several characteristics can lead to therapeutic resistance. CD133 has been identified as a putative CSC marker in colorectal cancer; however, its functional role still needs elucidation. We verified the role of CD133 with emphasis on expression location and correlated the results of CD133 with clinical outcome in colorectal cancer.

METHODS

We used immunohistochemistry to investigate the expression of CD133 in samples from 157 patients with colonic adenocarcinoma and from 76 patients with rectal adenocarcinoma who received neoadjuvant CCRT. We also correlated the expression location of CD133 with the clinicopathological parameters and prognosis.

RESULTS

CD133 protein was variably overexpressed in colorectal cancer tissues and was present in three locations: apical and/or endoluminal surfaces, cytoplasm, and lumen. Cytoplasmic CD133 expression level correlated significantly with tumor local recurrence (P = 0.025) and survival of patients with colorectal cancer (P = 0.002), and correlated inversely with tumor regression grading (P = 0.021) after CCRT in patients with rectal cancer.

CONCLUSIONS

The expression of CD133 in the cytoplasm is closely associated with local recurrence and patient survival, and may provide a reliable prognostic indicator of tumor regression grading in patients with rectal cancer after CCRT. Cytoplasmic CD133 expression may also help identify the surviving cancer cells in areas with nearly total regression after CCRT.

Association of CTTN polymorphisms with the risk of colorectal cancer

Purpose

Various studies searching for biomarkers to predict tumor metastasis or prognosis in both esophageal squamous cell carcinoma (ESCC) and head and neck squamous cell carcinoma (HNSCC) are currently underway. However, few data have been reported on its association with colorectal cancer (CRC). Single nucleotide polymorphisms (SNPs) are the most common known form of human genetic variation and may contribute to an increased susceptibility to cancer including CRC. The present study aimed to investigate whether the polymorphisms in the CTTN gene are associated with susceptibility to CRC in the Korean population.

Methods

A case-control study was performed to examine the relationship between the CTTN g.-9101C>T, g.-8748C>T, and g.72C>T polymorphisms and the risk of CRC. Polymerase chain reaction-restriction fragment length polymorphism analysis of g.-8748C>T, g.-9101C>T and Taqman analysis of g.72C>T were performed on blood samples from 218 patients with CRC and 533 control individuals. The g.-9101C>T, g.-8748C>T, and g.72C>T SNPs in CTTN and their haplotypes were analyzed.

Results

The genotype and allele frequencies of g.-9101C>T, g.-8748C>T, and g.72C>T did not differ between the patient group and the control group. Further, the haplotype of CTTN g.-9101C>T, g.-8748C>T, and g.72C>T did not differ between patient group and the control group. However, the genotype and allele frequencies of CTTN g.-9101C>T were significantly increased in the lymph node positive CRC group compared to the control group.

Conclusion

The CTTN g.-9101C>T polymorphism may influence lymph node positive CRC.

A quantitative proteomic approach of the different stages of colorectal cancer establishes OLFM4 as a new nonmetastatic tumor marker

Expression profiles represent new molecular tools that are useful to characterize the successive steps of tumor progression and the prediction of recurrence or chemotherapy response. In this study, we have used quantitative proteomic analysis to compare different stages of colorectal cancer. A combination of laser microdissection, OFFGEL separation, iTRAQ labeling, and MALDI-TOF/TOF MS was used to explore the proteome of 28 colorectal cancer tissues. Two software packages were used for identification and quantification of differentially expressed proteins: Protein Pilot and iQuantitator. Based on ∼1,190,702 MS/MS spectra, a total of 3138 proteins were identified, which represents the largest database of colorectal cancer realized to date and demonstrates the value of our quantitative proteomic approach. In this way, individual protein expression and variation have been identified for each patient and for each colorectal dysplasia and cancer stage (stages I-IV). A total of 555 proteins presenting a significant fold change were quantified in the different stages, and this differential expression correlated with immunohistochemistry results reported in the Human Protein Atlas database. To identify a candidate biomarker of the early stages of colorectal cancer, we focused our study on secreted proteins. In this way, we identified olfactomedin-4, which was overexpressed in adenomas and in early stages of colorectal tumors. This early stage overexpression was confirmed by immunohistochemistry in 126 paraffin-embedded tissues. Our results also indicate that OLFM4 is regulated by the Ras-NF-κB2 pathway, one of the main oncogenic pathways deregulated in colorectal tumors.

Toward standardized high-throughput serum diagnostics: multiplex-protein array identifies IL-8 and VEGF as serum markers for colon cancer

Development and progression of colon cancer may be related to cytokines. Cytokines with diagnostic value have been identified individually but have not been implemented into clinical praxis. Using a multiplex protein array, the authors explore a panel of cytokines simultaneously and compared its performance to carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9). Serum concentrations of 12 cytokines were simultaneously determined by multiplex biochip technology in 50 colon cancer patients and 50 healthy controls. Serum levels of interleukin-8 (IL-8) and CEA were significantly higher in cancer patients than in healthy controls. Areas under the receiver operating characteristic curves (AUCs) were largest for IL-8, followed by CEA, vascular endothelial growth factor (VEGF), and CA 19-9. Analyses regarding marker combinations showed an advantage over single marker performance for CEA, VEGF, and CA 19-9 but not for IL-8. Multiplex biochip array technology represents a practical tool in cytokine and cancer research when simultaneous determination of different biomarkers is of interest. The results suggest that the assessment of IL-8, CEA, VEGF, and possibly CA 19-9 serum levels could be useful for colon cancer screening with the potential of also detecting early stage tumors. Further validation studies using these and additional markers on a multiplex array format are encouraged.

Highly glycosylated tumour antigens: interactions with the immune system

A common phenotypic change in cancer is a dramatic transformation of cellular glycosylation. Functional studies of particular tumour-associated oligosaccharides are difficult to interpret conclusively, but carbohydrate-binding proteins are likely to contribute to progression of the tumour. This review discusses the potential role of CLRs (C-type lectin receptors), expressed by antigen-presenting cells of the immune system, in tumour recognition and immune modulation. Studies in recent years have provided significant insight into the immunomodulatory function of CLR during infections, but their role in cancer remains elusive; some strongly bind tumour cells and antigens, indicating participation in malignancy. The potential to use recombinant CLR as diagnostic tools will also be discussed.

Clinical relevance of serum vascular endothelial growth factor and interleukin-6 in patients with colorectal cancer

BACKGROUND/AIM

Some biological factors play a role in stimulation of malignant growth, metastasis and angiogenesis; however, their clinical relevance has not yet been well established for most of them. This work was aimed at studying the clinical relevance of serum vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6), in patients with colorectal cancer (CRC).

MATERIALS AND METHODS

Preoperative serum levels of VEGF and IL-6 were measured by enzyme-linked immuno-assay in 35 CRC patients and in 30 healthy controls.

RESULTS

CRC patients with or without metastasis had significantly higher VEGF and IL-6 levels than healthy controls (all P < 0.001). Patients with advanced clinical stage had significantly higher levels of VEGF and IL-6 than those with early clinical stage (all P < 0.001). Also, patients with metastatic disease had significantly higher VEGF and IL-6 levels than those with localized disease (all P < 0.001). The diagnostic accuracy for invasiveness was 83% for VEGF (cut off value = 240 pg/ml) and 66% for IL-6 (cut off value = 6.7 pg/ml), with sensitivity 79% and 74% and specificity 68% and 59%, respectively.

CONCLUSION

In CRC patients, preoperative measurement of serum VEGF and Il-6 may prove useful non-invasive diagnostic indicators associated with advanced clinical stage and tumor metastasis that warrants further investigations.

Serum protein fingerprinting for diagnosis and prognosis evaluation of colorectal cancer

AIM: To identify differentially expressed proteins for diagnosis and prognosis evaluation of colorectal cancer by serum protein fingerprint in colorectal cancer patients.

METHODS: Serum protein fingerprinting was performed by surface-enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS) in 45 colorectal cancer patients, 14 colorectal cancer having a good prognosis (no postoperative recurrence and metastasis), 13 colorectal cancer patients having a poor prognosis (having recurrence or metastasis), 24 patients with benign gastrointestinal disease, and 155 healthy controls. The Biomarker Wizard software was used to identify differential proteins. Two respective artificial neural network (ANN) models were developed for diagnosis and prognosis evaluation of colorectal cancer.

RESULTS: Seven proteins that displayed significant differential expression were identified (all P < 0.01), and their molecular weight was 4 955 Da, 5 325 Da, 5 890 Da, 6 615 Da, 7 739 Da, 8 109 Da, and 8 575 Da, respectively. Using these seven protein markers, we developed an artificial neural network model for diagnosis of colorectal cancer. Furthermore, five proteins that had a molecular weight of 4 955 Da, 5 325 Da, 5 890 Da, 6 615 Da, and 7 739 Da were used to develop an artificial neural network model for evaluation of the prognosis of colorectal cancer. The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of the diagnostic model were 82.22%, 80.45%, 94.74%, 51.39% and 80.80%, respectively. The coincidence rate of the prognostic model for evaluation of recurrence and metastasis was 62.96%.

CONCLUSION: SELDI-TOF-MS serum protein fingerprinting allows identification of differentially expressed proteins in colorectal cancer to develop models for diagnosis and prognosis evaluation of the disease.

Proteomic analysis of colorectal cancer: prefractionation strategies using two-dimensional free-flow electrophoresis

This review deals with the application of a new prefractionation tool, free-flow electrophoresis (FFE), for proteomic analysis of colorectal cancer (CRC). CRC is a leading cause of cancer death in the Western world. Early detection is the single most important factor influencing outcome of CRC patients. If identified while the disease is still localized, CRC is treatable. To improve outcomes for CRC patients there is a pressing need to identify biomarkers for early detection (diagnostic markers), prognosis (prognostic indicators), tumour responses (predictive markers) and disease recurrence (monitoring markers). Despite recent advances in the use of genomic analysis for risk assessment, in the area of biomarker identification genomic methods alone have yet to produce reliable candidate markers for CRC. For this reason, attention is being directed towards proteomics as a complementary analytical tool for biomarker identification. Here we describe a proteomics separation tool, which uses a combination of continuous FFE, a liquid-based isoelectric focusing technique, in the first dimension, followed by rapid reversed-phase HPLC (1–6 min/analysis) in the second dimension. We have optimized imaging software to present the FFE/RP-HPLC data in a virtual 2D gel-like format. The advantage of this liquid based fractionation system over traditional gel-based fractionation systems is the ability to fractionate large quantity protein samples. Unlike 2D gels, the method is applicable to both high-M_r proteins and small peptides, which are difficult to separate, and in the case of peptides, are not retained in standard 2D gels.

A study of the expression of Cyclin E and its isoforms in tumor and adjacent mucosa, correlated to patient outcome in early colon cancer

BACKGROUND

Cyclin E, a key regulator in the cell cycle, is often over-expressed in malignant disease. It can present as full length (FL) and low-molecular-weight (LMW) isoforms. The purpose of this study was to characterize the expression pattern of cyclin E in colon cancer, both in tumor and in macroscopically normal adjacent mucosa. A secondary aim was to study the possible correlation to clinical factors and patient outcome.

MATERIAL AND METHOD

Tumor and mucosa tissue from 114 patients with radically operated, non-metastatic colon tumors were analyzed. The cyclin E expression was measured by Western Blot in the tumor and adjacent mucosa using the antibody targeting C-terminal. The cyclin E expression was correlated to both pathology factors as differentiation grade and to the patient outcome.

RESULTS

Cyclin E was detected in both tumor and adjacent mucosa and in both FL and LMW-forms. FL was present in 29 (25.4%) tumors and only in three (2.6%) mucosa samples, the corresponding figures for the LMW-isoforms were 80 (70.2%) and 67 (58.8%). There was no correlation between the cyclin E expression and gender, age, tumor location or tumor pathology. Patients with a high expression of LMW isoforms (p < 0.03) or a high total expression (FL+LMW) (p < 0.006) had higher risks of recurrence and thus a worse survival.

CONCLUSION

Cyclin E is expressed in FL- and LMW-forms in both colon tumors and the macroscopically normal adjacent mucosa. A high expression of cyclin E in tumor was associated with an increased risk of tumor recurrence and a worse outcome. It could be a possible prognostic marker in non-metastatic colon cancer.

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.

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.

Metabolic profiling of human colorectal cancer using high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy and gas chromatography mass spectrometry (GC/MS)

Current clinical strategy for staging and prognostication of colorectal cancer (CRC) relies mainly upon the TNM or Duke system. This clinicopathological stage is a crude prognostic guide because it reflects in part the delay in diagnosis in the case of an advanced cancer and gives little insight into the biological characteristics of the tumor. We hypothesized that global metabolic profiling (metabonomics/metabolomics) of colon mucosae would define metabolic signatures that not only discriminate malignant from normal mucosae, but also could distinguish the anatomical and clinicopathological characteristics of CRC. We applied both high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) and gas chromatography mass spectrometry (GC/MS) to analyze metabolites in biopsied colorectal tumors and their matched normal mucosae obtained from 31 CRC patients. Orthogonal partial least-squares discriminant analysis (OPLS-DA) models generated from metabolic profiles obtained by both analytical approaches could robustly discriminate normal from malignant samples (Q(2) > 0.50, Receiver Operator Characteristic (ROC) AUC >0.95, using 7-fold cross validation). A total of 31 marker metabolites were identified using the two analytical platforms. The majority of these metabolites were associated with expected metabolic perturbations in CRC including elevated tissue hypoxia, glycolysis, nucleotide biosynthesis, lipid metabolism, inflammation and steroid metabolism. OPLS-DA models showed that the metabolite profiles obtained via HR-MAS NMR could further differentiate colon from rectal cancers (Q(2)> 0.60, ROC AUC = 1.00, using 7-fold cross validation). These data suggest that metabolic profiling of CRC mucosae could provide new phenotypic biomarkers for CRC management.

Identification of colorectal cancer patients by serum protein profile using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

AIM: To establish a serum protein fingerprinting technique coupled with a pattern-matching algorithm to distinguish colorectal cancer from healthy individuals.

METHODS: Serum samples were applied to metal affinity protein chips to generate mass spectra by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Protein peak identification and clustering were performed using the Biomarker Wizard software. Proteomic spectra of serum samples from 84 colorectal cancer patients and age- and sex-matched 83 healthy individuals were used as a training set and a classification tree with 1 distinct protein masses was generated by using Biomarker Pattern software. The validity of the classification tree was then challenged with a blind test set including another 85 colorectal cancer patients and 83 healthy individuals. We additionally determined carcinoembryonic antigen (CEA) in all the serum samples included in the blind test set using an electrochemiluminescent immunoassay.

RESULTS: The software identified an average of 59 mass peaks/spectrum and 1 of the identified peaks at 5765 was used to construct the classification tree. The classification tree separated effectively colorectal cancer from healthy individuals, with a sensitivity of 98.81% and a specificity of 100.00%. The blind test challenged the model with a sensitivity of 97.65% and a specificity of 98.80%, and a positive predictive value of 98.81%, respectively. The specificity and sensitivity provided by CEA were significantly lower than that of the SELDI marker pattern (P < 0.05).

CONCLUSION: SELDI-TOF-MS technique can correctly distinguish colorectal cancer patients from healthy individuals and shows great potential for the development of a screening test for the detection of colorectal cancer.

Profiling tumor-associated autoantibodies for the detection of colon cancer

PURPOSE

The purpose of the present study was to screen the autoantibody signature of colon cancers to develop serum markers for colon cancer detection.

EXPERIMENTAL DESIGN

A phage cDNA expression library of colon cancer was built. The library was sequentially screened by a pool of 10 colon cancer sera, goat antihuman IgG, and a pool of two healthy sera to identify phage-expressed antigens recognized by tumor-associated antibodies. The clones picked out by these screening were subjected to a training set with 24 colon cancer sera and 24 healthy sera. The antigen combination, which got the most satisfactory classification, was tested by an independent set of 24 colon cancer sera with equal number of sera from normal donors. The carcinoembryonic antigen (CEA) level of these sera was detected for the additional classification analysis with or without the antigen combination.

RESULTS

A cDNA expression library consisting of 2 x 10(6) primary clones was prepared. After three turns of screening, 24 antigens recognized by tumor-associated antibodies were picked out for serum marker identification. The training set showed that a six-marker combination got the most satisfactory classification in a logistic regression model; leave-one-out validation achieved 91.7% sensitivity and 91.7% specificity. In a testing set with this marker panel, we correctly predicted 85% of the samples. Although according to CEA level alone, we correctly predicted 75% of the samples with 42% of cancer patients misclassified. When CEA was combined with the six markers, the sensitivity and specificity increased to 91.7% and 95.8%, respectively. The six antigen sequences in the phage display system are relatively short peptides. Only two of them showed homology to known protein sequences.

CONCLUSIONS

Autoantibodies against phage-expressed antigens derived from colon cancer tissues could be used as serum markers for the detection of colon cancer.

Proteomic expression analysis of surgical human colorectal cancer tissues: up-regulation of PSB7, PRDX1, and SRP9 and hypoxic adaptation in cancer

Colorectal adenocarcinoma is one of the worldwide leading causes of cancer deaths. Discovery of specific biomarkers for early detection of cancer progression and the identification of underlying pathogenetic mechanisms are important tasks. Global proteomic approaches have thus far been limited by the large dynamic range of molecule concentrations in tissues and the lack of selective enrichment of the low-abundance proteome. We studied paired cancerous and normal clinical tissue specimens from patients with colorectal adenocarcinomas by heparin affinity fractionation enrichment (HAFE) followed by 2-D PAGE and tandem mass spectrometric (MS/MS) identification. Fifty-six proteins were found to be differentially expressed, of which 32 low-abundance proteins were only detectable after heparin affinity enrichment. MS/MS was used to identify 5 selected differentially expressed proteins as proteasome subunit beta type 7 (PSB7), hemoglobin alpha subunit (HBA), peroxiredoxin-1 (PRDX1), argininosuccinate synthase (ASSY), and signal recognition particle 9 kDa protein (SRP9). This is the first proteomic study detecting the differential expression of these proteins in human colorectal cancer tissue. Several of the proteins are functionally related to tissue hypoxia and hypoxic adaptation. The relative specificities of PSB7, PRDX1, and SRP9 overexpression in colon cancer were investigated by Western blot analysis of patients with colon adenocarcinomas and comparison with a control cohort of patients with lung adenocarcinomas. Furthermore, immunohistochemistry on tissue sections was used to define the specific locations of PSB7, PRDX1, and SRP9 up-regulation within heterogeneous primary human tumor tissue. Overexpression of the three proteins was restricted to the neoplastic cancer cell population within the tumors, demonstrating both cytoplasmic and nuclear localization of PSB7 and predominantly cytoplasmic localization of PRDX1 and SRP9. In summary, we describe heparin affinity fractionation enrichment (HAFE) as a prefractionation tool for the study of the human primary tissue proteome and the discovery of PSB7, PRDX1, and SRP9 up-regulation as candidate biomarkers of colon cancer.

Association of vascular endothelial growth factor gene polymorphisms with susceptibility and clinicopathologic characteristics of colorectal cancer

Since vascular endothelial growth factor (VEGF) is known to be a potent pro-angiogenic factor, we evaluated the potential association of two VEGF gene polymorphisms (-634G>C and 936C>T) with the susceptibility and the clinicopathologic characteristics of colorectal cancer (CRC). The VEGF genotypes were determined using fresh colorectal tissue from 465 patients who had undergone a surgical resection and peripheral blood lymphocytes from 413 healthy controls by PCR/DHPLC assay. For the -634G>C polymorphism, the -634 GC or CC genotype was associated with a decreased risk of CRC (odds ratio [OR], 0.62; p=0.001) as a dominant model of C allele, whereas the 936 TT genotype correlated with advanced stage/ metastasis, a high serum level of CA19-9, and an higher grade in patients with CRC. In the haplotype analyses, haplotype -634C/936C and -634G/936T were associated with a decreased susceptibility of CRC (OR, 0.53 and 0.56; p<0.001, respectively). These observations imply that the VEGF gene polymorphisms may be associated with the susceptibility or clinicopathologic features of CRC. However, further studies of other VEGF sequence variants and their biological functions are needed to understand the role of the VEGF gene polymorphisms in the development and progression of CRC.

New insights into the role of age and carcinoembryonic antigen in the prognosis of colorectal cancer

The aim of this study was to verify through relative survival (an estimate of cancer-specific survival) the true prognostic factors of colorectal cancer. The study involved 506 patients who underwent locally radical resection. All the clinical, histological and laboratory parameters were prognostically analysed for both overall and relative survival. This latter was calculated from the expected survival of the general population with identical age, sex and calendar years of observation. Univariate and multivariate analyses were applied to the proportional hazards model. Liver metastases, age, lymph node involvement and depth of bowel wall involvement were independent prognosticators of both overall and relative survival, whereas carcinoembryonic antigen (CEA) was predictive only of relative survival. Increasing age was unfavourably related to overall survival, but mildly protective with regard to relative survival. Three out of the five prognostic factors identified are the cornerstones of the current staging systems, and were confirmed as adequate by the analysis of relative survival. The results regarding age explain the conflicting findings so far obtained from studies considering overall survival only and advise against the adoption of absolute age limits in therapeutic protocols. Moreover, the prechemotherapy CEA level showed a high clinical value.

Tumour markers in colorectal cancer: European Group on Tumour Markers (EGTM) guidelines for clinical use

The aim of this article is to present updated guidelines for the use of serum, tissue and faecal markers in colorectal cancer (CRC). Lack of specificity and sensitivity preclude the use of all existing serum markers for the early detection of CRC. For patients with stage II or stage III CRC who may be candidates for either liver resection or systemic treatment should recurrence develop, CEA should be measured every 2-3 months for at least 3 years after diagnosis. Insufficient evidence exists to recommend routine use of tissue factors such as thymidylate synthase, microsatellite instability (MSI), p53, K-ras and deleted in colon cancer (DCC) for either determining prognosis or predicting response to therapy in patients with CRC. Microsatellite instability, however, may be used as a pre-screen for patients with suspected hereditary non-polyposis colorectal cancer. Faecal occult blood testing but not faecal DNA markers may be used to screen asymptomatic subjects 50 years or older for early CRC.

A serum proteomic pattern for the detection of colorectal adenocarcinoma using surface enhanced laser desorption and ionization mass spectrometry

PURPOSE

New serum biomarkers are needed to improve the early detection of colorectal adenocarcinoma. We performed surface enhanced laser desorption and ionization time-of-flight mass spectrometry (SELDI-TOF-MS) to screen for differentially expressed proteins in serum and build a proteomic diagnostic pattern for the detection of colorectal adenocarcinoma to improve the prognosis of patients with this disease.

EXPERIMENTAL DESIGN

In an attempt to improve current approaches to the serologic diagnosis of colorectal cancer, we analyzed serum samples from subjects with or without colorectal cancer using SELDI-MS. Using a case-control study design, SELDI-MS profile of serum samples from 74 colorectal adenocarcinoma patients were compared with 48 age-and sex-matched healthy subjects using a ProteinChip reader, PBSII-C. Proteomic MS spectra were generated using IMAC3 chips, and protein peaks clustering and classification analyses were performed to build a proteomic pattern that could differentiate patients with colorectal adenocarcinoma from healthy subjects utilizing Biomarker Wizard and Biomarker Patterns software packages, respectively. The constructed pattern was then used to test an independent set of masked serum samples from 60 colorectal cancer patients and 39 healthy subjects.

RESULTS

Among the differentially expressed protein peaks identified by SELDI-MS profiling that had the ability to distinguish between patients and healthy subjects, we determined a minimum set of two protein peaks for system training and for developing a decision classification pattern. Masked analysis of an independent set of serum samples showed the diagnostic pattern could differentiate patients with different stages of colorectal cancer from healthy subjects with a sensitivity of 95.00 percent and specificity of 94.87 percent.

CONCLUSION

SELDI-TOF-MS profiling of serum proteins combined with bioinformatics tools can be applied to accurately differentiate patients with colorectal cancer from healthy subjects. The high sensitivity and specificity achieved by the constructed clustering analysis algorithm show great potential for the early detection of colorectal cancer.

Raf kinase inhibitor protein expression in a survival analysis of colorectal cancer patients

PURPOSE

Raf kinase inhibitor protein (RKIP) inhibits the Raf and nuclear factor kappa B signaling pathways, and suppresses metastasis in animal models. We examined whether RKIP expression in primary colorectal cancers (CRCs) correlates with the risk of metastasis and overall survival.

PATIENTS AND METHODS

RKIP expression was examined immunohistochemically in three separate cohorts: a tissue microarray containing 276 samples from human tumors and normal tissues, and retrospective studies of 268 CRC patients and 65 early-stage CRCs. Overall and metastasis-free survival rates were measured.

RESULTS

RKIP was expressed in normal epithelia but was reduced in metastatic tumors. RKIP expression in primary CRC was an independent prognostic marker for survival using multivariate Cox regression analysis (hazard ratio, 2.808; 95% CI, 1.58 to 4.96; P = .0002), independent of Dukes' stage. Patients with Dukes' C RKIP-positive tumors had similar 5-year survival rates as early-stage patients if tumors had equivalent RKIP expression levels. An independent study of early-stage CRCs confirmed that reduced RKIP expression predicted metastatic recurrence and reduced disease-free survival (hazard ratio, 4.5; 95% CI, 1.7 to 12.3; P = .003). RKIP expression was independent of sex, age, mitotic index, lymphatic and vascular invasion, depth of invasion, and tumor site, but correlated positively with apoptotic index (P = .024). Weak or loss of RKIP expression was the most significant and independent prognostic marker using a multivariate regression equation (hazard ratio, 4.5; 95% CI, 1.7 to 12.3; P = .003).

CONCLUSION

RKIP expression in primary CRCs correlates with overall and disease-free survival, and can be useful for identifying early-stage CRC patients at risk of relapse.

Immunomodulatory roles of the carcinoembryonic antigen family of glycoproteins

One of the most remarkable aspects of the immune system is its ability to fashion an immune response most appropriate to the activating stimulus. Although the immune system possesses a number of adaptations to accomplish this, an important theme is local immune regulation by site-specific expression of receptors and ligands. One family of molecules that is gaining attention as modulators of the immune system is the carcinoembryonic antigen cell-adhesion molecule family (CEACAM). Functionally, the carcinoembryonic antigen family can mediate cell-cell contact, host-pathogen interactions, and immune regulation. For example, biliary glycoprotein (CEACAM1) can have direct activity on T cells, leading to the inhibition of helper or cytotoxic T cell function. The expression of carcinoembryonic antigen (CEACAM5) on intestinal epithelial cells is involved in the activation of populations of regulatory CD8(+) T cells, while a distinct subset of regulatory CD8+ T cells is activated by nonspecific cross-reacting antigen (CEACAM6) on placental trophoblasts. Interestingly, the function and phenotype of these cells depend upon the specific member of the carcinoembryonic antigen family expressed, as well as the antigen-presenting molecule with which it associates. Thus, these glycoproteins comprise a family of molecules whose functions can depend on their nature and context.

Autoantibody Cancer Biomarker: Extracellular Protein Kinase A

In cancer cells, cyclic AMP-dependent protein kinase (PKA) is secreted into the conditioned medium. This PKA, designated as extracellular protein kinase A (ECPKA), is markedly up-regulated in the sera of patients with cancer. The currently available tumor markers are based on the antigen determination method and lack specificity and sensitivity. Here, we present an ECPKA autoantibody detection method for a universal biomarker that detects cancer of various cell types. We tested sera from 295 patients with cancers of various cell types, 155 normal controls, and 55 patients without cancer. The specificity and sensitivity of this autoantibody enzyme immunoassay method were compared with the conventional antigen determination method by receiver-operating characteristic plots. In the sera, the presence of autoantibody directed against ECPKA was highly correlated with cancer. High anti-ECPKA autoantibody titers (frequency, 90%; mean titer, 3.0) were found in the sera of patients with various cancers, whereas low or negative titers (frequency, 12%; mean titer, 1.0) were found in the control group. The receiver-operating characteristic plot showed that autoantibody enzyme immunoassay exhibited 90% sensitivity and 88% specificity, whereas the enzymatic assay exhibited 83% sensitivity and 80% specificity. These results show that the autoantibody method distinguished between patients with cancer and controls better than the antigen method could. Our results show that autoantibody ECPKA is a universal serum biomarker for cancers of various cell types.

Preoperative carcinoembryonic antigen and albumin in predicting survival in patients with colon and rectal carcinomas

OBJECTIVE

To examine the relationship between postoperative outcomes of colorectal carcinoma patients and preoperative serum carcinoembryonic antigen (CEA) and albumin (ALB) levels and evaluate if these levels can accurately predict outcomes and/or be factor indicating adjuvant chemotherapy.

BACKGROUND

CEA is a marker for colorectal carcinoma and its level usually increases before a distant metastasis is detected. Also, a low level of serum ALB is usually found in metastatic colorectal carcinoma patients.

STUDY

A retrospective cohort study of patients with colorectal carcinomas who were treated with curative surgery in Songklanagarind Hospital between 1998 and 2002.

RESULTS

One hundred seventy patients were identified with a median survival of 1131 days (range 71 to 2293 d) and with an overall 5-year survival rate of 54%. Patients were stratified using CEA at 5 ng/mL and an ALB level at 3.5 g/dL into 4 groups: (1) low CEA, high ALB; (2) low CEA, low ALB; (3) high CEA, high ALB; and (4) high CEA, low ALB. The 5-year survival rates for groups 1 to 4 were 66%, 63%, 46%, and 34%, respectively. There was statistically significant difference in 5-year survival between the well-differentiated tumor with low CEA and the poorly differentiated tumor with high CEA (P=0.0115). The high CEA patients who had the well-differentiated tumor had longer survival than those with a poorly differentiated tumor (P=0.0412).

CONCLUSIONS

A preoperative CEA level greater than or equal to 5 ng/mL and ALB level less than 3.5 g/dL predict a poor survival chance for colorectal carcinoma patients. In high CEA patients, tumor differentiated is an independent factor affecting survival.

Autoantibody biomarkers in the detection of cancer

By definition, tumor biomarkers are selective molecules that can distinguish between patients with cancer and controls. Serum tumor markers have been the most widely used approach for cancer detection. However, the limitations of these markers, which are based on the measurement of tumor antigens, preclude their general use in cancer screening and diagnosis. Here we give an overview of recent cancer biomarker developments based on the detection of autoantibodies produced against tumor antigens in patients' sera. This new detection method can measure the autoantibodies for a spectrum of tumor antigens in a single assay, with sensitivity and specificity exceeding those obtained using the conventional antigen determination method. Autoantibodies against serum cancer biomarkers offer a novel technology for cancer detection.

HCCR-1-interacting molecule "deleted in polyposis 1" plays a tumor-suppressor role in colon carcinogenesis

BACKGROUND & AIMS

Human cervical cancer oncogene (HCCR-1) has appeared to act as a negative regulator of p53 and contributes to tumorigenesis of various organs including the colon. We identified the HCCR-1 binding protein deleted in polyposis 1 (DP1) and accessed the role of HCCR-1 and DP1 in colon tumorigenesis.

METHODS

Yeast 2-hybrid was used to identify HCCR-1 interacting proteins. Various molecular biological approaches were used to examine the expression profile of HCCR-1 and DP1, subcellular localization, epitope mapping, the biological role of DP1, and the serum HCCR-1 level. Loss of heterozygosity frequency around DP1 also was examined.

RESULTS

We identified that HCCR-1 interacted with DP1. These 2 proteins colocalized in mitochondria but the expression of HCCR-1 showed negative correlation with that of DP1 in colorectal cancer (CRC). DP1 played a tumor-suppressor role in colon tumorigenesis (ie, DP1-transfected RKO cells showed growth inhibition, apoptosis, decreased telomerase activity, and up-regulation of p53). These phenomena were reversed when HCCR-1 was overexpressed. Loss of heterozygosity around the DP1 gene was observed frequently (50%) in CRCs. We examined the use of serum HCCR-1 in CRC patients. The sensitivity of HCCR-1 (76.0%) for detecting CRC was proven to be much higher than that of CA19-9 (32.0%).

CONCLUSIONS

DP1 plays a tumor-suppressor role in CRC. DP1 and HCCR-1 are supposed to regulate each other negatively by interaction, but further study is required to get better insight into the biological significance of the interaction.

Autoantibody biomarker opens a new gateway for cancer diagnosis

The list of cancer markers of current interest has grown considerably, but none of the markers used in clinical work is a true tumor marker. These cancer biomarkers are based on the determination of tumor antigens. Here, we report a single method of autoantibody enzyme immunoassay (EIA) screens for a spectrum of serum tumor markers. A comparison of the autoantibody-based EIA to conventional antigen EIA kits, using receiver operating characteristic (ROC) plots, showed that the autoantibody EIA can significantly enhance the sensitivity and specificity of tumor markers. The detection of serum autoantibodies for a spectrum of serum tumor markers, as demonstrated here, suggests that most, if not all, serum cancer biomarkers produce autoantibodies. A unique autoantibody biomarker screening method, as presented here, might therefore facilitate achieving the accurate and early diagnosis of cancer.

Altered Expression and Localization of Creatine Kinase B, Heterogeneous Nuclear Ribonucleoprotein F, and High Mobility Group Box 1 Protein in the Nuclear Matrix Associated with Colon Cancer

Identification of biomarkers could lead to the development of effective screening tests for colorectal cancer. A previous study from our laboratory showed specific alterations of nuclear structure in colon cancer. In an effort to characterize these biomarkers, protein spots were selected from separations made by two-dimensional gel electrophoresis, which were analyzed by mass spectrometry. The sequences obtained from the isolated spots revealed that they have close similarity to creatine kinase B (CKB) isoforms, heterogeneous nuclear ribonucleoprotein F (hnRNP F) and high mobility group box 1 protein (HMGB1) isoforms. To determine the expression of these proteins in colon cancer, expression was studied in 9 tumor and matched adjacent normal pairs, 5 donor colons, 16 polyps, 4 metastatic liver lesions and matched adjacent normal pairs, and 3 liver donors. CKB and hnRNP F were expressed in 78% and 89% of colon tumors, respectively. hnRNP F had a higher frequency of expression than CKB in premalignant polyps. With the establishment of differential expression of the proteins in colon cancer, their subcellular localization was analyzed. The subcellular fractions studied both showed high protein levels of hnRNP F in colon tumors compared with normal colon tissues. Surprisingly, subcellular levels of CKB were decreased in colon tumors, suggesting that the observed high CKB levels in nuclear matrix extracts are caused by the enhanced localization of CKB to the nuclear matrix during colon tumorigenesis. These results suggest an involvement of hnRNP F and CKB in colorectal cancer. Additionally, they suggest that hnRNP F is a potential marker for colorectal cancer progression.

Normal and modified urinary nucleosides represent novel biomarkers for colorectal cancer diagnosis and surgery monitoring

BACKGROUND

Up to now, there is still no ideal tumor marker in early diagnosis and effective monitoring, especially for surgical resection of colorectal cancer (CRC). The aim of the present study was to evaluate the application of urinary normal and modified nucleosides in diagnosis and surgery monitoring of CRC.

METHODS

Between October 2002 and July 2003, 52 consecutive patients with pathological confirmed CRC were enrolled. Spontaneous urine samples were collected 1 day before surgery and on day 8 postoperatively, and 14 urinary nucleosides were determined by reverse-phase high-performance liquid chromatography (RP-HPLC). Another 62 healthy people were also studied as control. The clinical routine tumor markers, serum carcinoembryonic antigen (CEA), carbohydrate antigen (CA)199, CA125, and alpha-fetoprotein (AFP) of CRC patients, were correspondingly evaluated by electrochemiluminescent immunoassay.

RESULTS

The levels of 11 out of 14 of the determined urinary nucleosides in the CRC group were much higher than those of normal controls. Through the principal component analysis of these 14 nucleosides, 76.9% of CRC patients were correctly classified. The sensitivity of this analysis was much higher than that of CEA (38.5%), CA199 (40.4%), CA125 (15.4%), and AFP (17.3%; P < 0.01). Receiver operating characteristic (ROC) curve analysis of 1-methylguanosine (m1G) and pseudouridine (Pseu) showed good sensitivity-specificity profiles of the diagnosis of CRC. The elevated levels of the nine nucleosides significantly decreased after curative resection of 40 CRC cases. The data also showed that the preoperative levels of some nucleosides were positively related with tumor size and Dukes staging of CRC.

CONCLUSION

The evaluation of normal and modified urinary nucleosides might become novel tumor markers, which will be facilitated in the clinical setting and helpful in the diagnosis, management and follow up of CRC. Pseu and m1G may be more promising for clinical use and be worthy of further studies in the near future.

Identification of proteins of human colorectal carcinoma cell line SW480 by two-dimensional electrophoresis and MALDI-TOF mass spectrometry

AIM: To conduct the proteomic analysis of human colorectal carcinoma cell line, SW480 by using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption /ionization-time of flight mass spectrometry (MALDI-TOFMS).

METHODS: The total proteins of human colorectal carcinoma cell line, SW480 were separated with 2-DE by using immobilized pH gradient strips and visualized by staining with silver nitrate. The gel images were acquired by scanner and 2-DE analysis software, Image Master 2D Elite. Nineteen distinct protein spots were excised from gel randomly and digested in gel by TPCK-trypsin. Mass analysis of the tryptic digest peptides mixture was performed by using MALDI-TOF MS. Peptide mass fingerprints (PMFs) obtained by the MALDI-TOF analysis were used to search NCBI, SWISS-PROT and MSDB databases by using Mascot software.

RESULTS: PMF maps of all spots were obtained by MALDI-TOF MS and thirteen proteins were preliminarily identified.

CONCLUSION: The methods of analysis and identification of protein spots of tumor cells in 2-DE gel with silver staining by MALDI-TOF MS derived PMF have been established. Protein expression profile of SW480 has been obtained. It is demonstrated that a combination of proteomics and cell culture is a useful approach to comprehend the process of colon carcinogenesis.