Meike de Wit

SATB2 in Combination With Cytokeratin 20 Identifies Over 95% of all Colorectal Carcinomas

The special AT-rich sequence-binding protein 2 (SATB2), a nuclear matrix-associated transcription factor and epigenetic regulator, was identified as a tissue type-specific protein when screening protein expression patterns in human normal and cancer tissues using an antibody-based proteomics approach. In this respect, the SATB2 protein shows a selective pattern of expression and, within cells of epithelial lineages, SATB2 expression is restricted to glandular cells lining the lower gastrointestinal tract. The expression of SATB2 protein is primarily preserved in cancer cells of colorectal origin, indicating that SATB2 could function as a clinically useful diagnostic marker to distinguish colorectal cancer (CRC) from other types of cancer. The aim of this study was to further explore and validate the specific expression pattern of SATB2 as a clinical biomarker and to compare SATB2 with the well-known cytokeratin 20 (CK20). Immunohistochemistry was used to analyze the extent of SATB2 expression in tissue microarrays with tumors from 9 independent cohorts of patients with primary and metastatic CRCs (n=1882). Our results show that SATB2 is a sensitive and highly specific marker for CRC with distinct positivity in 85% of all CRCs, and that SATB2 and/or CK20 was positive in 97% of CRCs. In conclusion, the specific expression of SATB2 in a large majority of CRCs suggests that SATB2 can be used as an important complementary tool for the differential diagnosis of carcinoma of unknown primary origin.

Proteomics in colorectal cancer translational research: biomarker discovery for clinical applications.

Colorectal cancer (CRC) is a major cause of cancer-related death in the western world. Screening to detect the disease in an early stage is the most effective approach to tackle this problem. In addition, better diagnostic tools for assessment of prognosis and prediction of response to drug therapy will allow for personalized therapies and better outcomes. Protein biomarkers that reflect tumor biology have the potential to address a wide range of clinical needs. These include diagnostic (screening) biomarkers for early detection, prognostic biomarkers for estimation of disease outcome, predictive biomarkers for adjuvant treatment stratification, and surveillance biomarkers for disease monitoring and treatment response. An important source for the discovery of potential biomarkers comes from mass spectrometry based proteomics research of the biology of CRC development. Here, we review recent colon cancer proteomics studies directed at identification of biomarker proteins. These include studies that use preclinical models (i.e. cell lines or murine tissues) as well as clinical materials (e.g. tissue and stool samples). We separately highlight some studies that focused on identification of cancer stem cell (CSC) related proteins in tumor spheroids, an in vitro model system for investigating CRC treatment response. Recent proteomics studies have generated many new candidate protein biomarkers. However, the lack of follow-up studies that lead to biomarker verification and/or validation remains a limiting factor in the translation of these candidate biomarkers into clinical applications. This is partly due to technological limitations which are bound to diminish with new technologies, including selected reaction monitoring mass spectrometry (SRM-MS). Antibodies are still required, though, both to perform high-throughput validation as well as to develop cost-effective tests for routine use in a clinical setting.

TPX2 and AURKA promote 20q amplicon-driven colorectal adenoma to carcinoma progression

Background and objective Progression of a colorectal adenoma to invasive cancer occurs in a minority of adenomas and is the most crucial step in colorectal cancer pathogenesis. In the majority of cases, this is associated with gain of a substantial part of chromosome 20q, indicating that multiple genes on the 20q amplicon may drive carcinogenesis. The aim of this study was to identify genes located on the 20q amplicon that promote progression of colorectal adenoma to carcinoma. Design Functional assays were performed for 32 candidate driver genes for which a positive correlation between 20q DNA copy number and mRNA expression had been demonstrated. Effects of gene knockdown on cell viability, anchorage-independent growth, and invasion were analysed in colorectal cancer cell lines with 20q gain. Colorectal tumour protein expression was examined by immunohistochemical staining of tissue microarrays. Results TPX2, AURKA, CSE1L, DIDO1, HM13, TCFL5, SLC17A9, RBM39 and PRPF6 affected cell viability and/or anchorage-independent growth. Chromosome 20q DNA copy number status correlated significantly with TPX2 and AURKA protein levels in a series of colorectal adenomas and carcinomas. Moreover, downmodulation of TPX2 and AURKA was shown to inhibit invasion. Conclusion These data identify TPX2 (20q11) and AURKA (20q13.2) as two genes located on distinct regions of chromosome 20q that promote 20q amplicon-driven progression of colorectal adenoma to carcinoma. Therefore the selection advantage imposed by 20q gain in tumour progression is achieved by gain-of-function of multiple cancer-related genes—knowledge that can be translated into novel tests for early diagnosis of progressive adenomas.

The cancer secretome, current status and opportunities in the lung, breast and colorectal cancer context☆

Despite major improvements on the knowledge and clinical management, cancer is still a deadly disease. Novel biomarkers for better cancer detection, diagnosis and treatment prediction are urgently needed. Proteins secreted, shed or leaking from the cancer cell, collectively termed the cancer secretome, are promising biomarkers since they might be detectable in blood or other biofluids. Furthermore, the cancer secretome in part represents the tumor microenvironment that plays a key role in tumor promoting processes such as angiogenesis and invasion. The cancer secretome, sampled as conditioned medium from cell lines, tumor/tissue interstitial fluid or tumor proximal body fluids, can be studied comprehensively by nanoLC-MS/MS-based approaches. Here, we outline the importance of current cancer secretome research and describe the mass spectrometry-based analysis of the secretome. Further, we provide an overview of cancer secretome research with a focus on the three most common cancer types: lung, breast and colorectal cancer. We conclude that the cancer secretome research field is a young, but rapidly evolving research field. Up to now, the focus has mainly been on the discovery of novel promising secreted cancer biomarker proteins. An interesting finding that merits attention is that in cancer unconventional secretion, e.g. via vesicles, seems increased. Refinement of current approaches and methods and progress in clinical validation of the current findings are vital in order to move towards applications in cancer management. This article is part of a Special Issue entitled: An Updated Secretome.

Subnuclear Proteomics in Colorectal Cancer IDENTIFICATION OF PROTEINS ENRICHED IN THE NUCLEAR MATRIX FRACTION AND REGULATION IN ADENOMA TO CARCINOMA PROGRESSION

Abnormalities in nuclear phenotype and chromosome structure are key features of cancer cells. Investigation of the protein determinants of nuclear subfractions in cancer may yield molecular insights into aberrant chromosome function and chromatin organization and in addition may yield biomarkers for early cancer detection. Here we evaluate a proteomics work flow for profiling protein constituents in subnuclear domains in colorectal cancer tissues and apply this work flow to a comparative analysis of the nuclear matrix fraction in colorectal adenoma and carcinoma tissue samples. First, we established the reproducibility of the entire work flow. In a reproducibility analysis of three nuclear matrix fractions independently isolated from the same colon tumor homogenate, 889 of 1,047 proteins (85%) were reproducibly identified at high confidence (minimally two peptides per protein at 99% confidence interval at the protein level) with an average coefficient of variance for the number of normalized spectral counts per protein of 30%. This indicates a good reproducibility of the entire work flow from biochemical isolation to nano-LC-MS/MS analysis. Second, using spectral counting combined with statistics, we identified proteins that are significantly enriched in the nuclear matrix fraction relative to two earlier fractions (the chromatin-binding and intermediate filament fractions) isolated from six colorectal tissue samples. The total data set contained 2,059 non-redundant proteins. Gene ontology mining and protein network analysis of nuclear matrix-enriched proteins revealed enrichment for proteins implicated in “RNA processing” and “mRNA metabolic process.” Finally, an explorative comparison of the nuclear matrix proteome in colorectal adenoma and carcinoma tissues revealed many proteins previously implicated in oncogenesis as well as new candidates. A subset of these differentially expressed proteins also exhibited a corresponding change at the mRNA level. Together, the results show that subnuclear proteomics of tumor tissue is feasible and a promising avenue for exploring oncogenesis.

Identification of key genes for carcinogenic pathways associated with colorectal adenoma-to-carcinoma progression

Colorectal adenomas form a biologically and clinically distinct intermediate stage in development of colorectal cancer (CRC) from normal colon epithelium. Only 5% of adenomas progress into adenocarcinomas, indicating that malignant transformation requires other biological alterations than those involved in adenoma formation. The present study aimed to explore which cancer-related biological processes are affected during colorectal adenoma-to-carcinoma progression and to identify key genes within these pathways that can serve as tumor markers for malignant transformation. The activity of 12 cancer-related biological processes was compared between 37 colorectal adenomas and 31 adenocarcinomas, using the pathway analysis tool Gene Set Enrichment Analysis. Expression of six gene sets was significantly increased in CRCs compared to adenomas, representing chromosomal instability, proliferation, differentiation, invasion, stroma activation, and angiogenesis. In addition, 18 key genes were identified for these processes based on their significantly increased expression levels. For AURKA and PDGFRB, increased mRNA expression levels were verified at the protein level by immunohistochemical analysis of a series of adenomas and CRCs. This study revealed cancer-related biological processes whose activities are increased during malignant transformation and identified key genes which may be used as tumor markers to improve molecular characterization of colorectal tumors.

Colorectal cancer candidate biomarkers identified by tissue secretome proteome profiling.

UNLABELLED Colorectal cancer (CRC) is a major health problem. Biomarkers associated with molecular changes in cancer cells can aid early detection, diagnosis, prognosis, therapy selection, and disease monitoring. Tumor tissue secretomes are a rich source of candidate biomarkers. To identify CRC protein biomarkers, secretomes of four pairs of human CRC tissue and patient-matched normal colon tissue samples, and secretomes of five CRC cell lines were analyzed by GeLC-MS/MS. Subsequent data analysis was based on label-free spectral counting, Ingenuity Pathway Analysis, Secretome/SignalP, STRING and Cytoscape, resulting in 2703 protein identifications in the tissue secretomes, of which 409 proteins were significantly more present in CRC samples than in controls. Biomarker selection of 76 candidates was based on consistent and abundant over-representation in cancer- compared to control-secretomes, and presumed neoplastic origin. Overlap analysis with previously obtained datasets revealed 21 biomarkers suited for early detection of CRC. Immunohistochemistry confirmed overexpression in CRC of one candidate marker (MCM5). In conclusion, a human reference dataset of 76 candidate biomarkers was identified for which we illustrate that combination with existing pre-clinical datasets allows pre-selection of biomarkers for blood- or stool-based assays to support clinical management of CRC. Further dedicated validation studies are required to demonstrate their clinical applicability. BIOLOGICAL SIGNIFICANCE Tissue secretome proteomes are a rich source of candidate biomarkers. Several secretome proteome datasets have been obtained from pre-clinical in vitro and in vivo colorectal cancer (CRC) model systems, yielding promising CRC biomarkers obtained under well-defined experimentally controlled conditions. However, which of these biomarker proteins are actually secreted by human CRC samples was not known. To our knowledge, this is the first study that directly compares secretome proteomes from clinically relevant human CRC tissues to patient-matched normal colon tissues. We identified 76 human CRC protein biomarkers that may facilitate blood-based or stool-based assay development to support clinical management of CRC. Overlap analysis with datasets from well-defined pre-clinical studies helps to determine what clinical application suits these human CRC biomarkers best, i.e. early detection, diagnosis, prognosis, therapy selection, and/or disease monitoring of CRC. This is demonstrated for a CRC mouse model dataset, revealing 21 human CRC biomarkers suited for early detection of CRC.

Whole gel processing procedure for GeLC-MS/MS based proteomics

BackgroundSDS-PAGE followed by in-gel digestion (IGD) is a popular workflow in mass spectrometry-based proteomics. In GeLC-MS/MS, a protein lysate of a biological sample is separated by SDS-PAGE and each gel lane is sliced in 5–20 slices which, after IGD, are analyzed by LC-MS/MS. The database search results for all slices of a biological sample are combined yielding global protein identification and quantification for each sample. In large scale GeLC-MS/MS experiments the manual processing steps including washing, reduction and alkylation become a bottleneck. Here we introduce the whole gel (WG) procedure where, prior to gel slice cutting, the processing steps are carried out on the whole gel.ResultsIn two independent experiments human HCT116 cell lysate and mouse tumor tissue lysate were separated by 1D SDS PAGE. In a back to back comparison of the IGD procedure and the WG procedure, both protein identification (>80% overlap) and label-free protein quantitation (R2=0.94) are highly similar between procedures. Triplicate analysis of the WG procedure of both HCT116 cell lysate and formalin-fixed paraffin embedded (FFPE) tumor tissue showed identification reproducibility of >88% with a CV<20% on protein quantitation.ConclusionsThe whole gel procedure allows for reproducible large-scale differential GeLC-MS/MS experiments, without a prohibitive amount of manual processing and with similar performance as conventional in-gel digestion. This procedure will especially enable clinical proteomics for which GeLC-MS/MS is a popular workflow and sample numbers are relatively high.

Cell surface proteomics identifies glucose transporter type 1 and prion protein as candidate biomarkers for colorectal adenoma-to-carcinoma progression

Background and objective Early detection of colon adenomas at high risk of progression and early-stage colorectal cancer (CRC) is an effective approach to reduce CRC death rates. Current screening methods lack specificity as they detect many adenomas that will never progress to CRC. The authors aimed to identify cell surface protein biomarkers with extracellular domains that could be targeted for molecular imaging and discriminate low-risk adenomas and normal colon from high-risk adenomas and CRC. Design Cell surface proteins of five CRC cell lines were biotinylated, isolated and analysed by in-depth proteomics using gel electrophoresis and nanoliquid chromatography coupled to tandem mass spectrometry. Differential expression in adenomas and CRCs was based on mRNA expression and verified by immunohistochemical staining of tissue microarrays. Results In total, 2609 proteins were identified in the cell surface fractions. Of these, 44 proteins were selected as promising cell surface candidate biomarkers for adenoma-to-carcinoma progression based on the following criteria: protein identification in at least four out of five cell lines, a predicted (trans)membrane location and increased mRNA expression in CRCs compared to adenomas. Increased protein expression in high-risk adenomas and CRCs compared to low-risk adenomas was confirmed by immunohistochemistry for glucose transporter type 1 (gene symbol SLC2A1; p<0.00001) and prion protein (gene symbol PRNP; p<0.005). Conclusion This study revealed glucose transporter type 1, prion protein and 42 other cell surface candidate biomarkers for adenoma-to-carcinoma progression that could potentially serve as targets for emerging molecular imaging modalities like optical imaging, 19F-MRI and positron emission tomography.

The role of SATB2 as a diagnostic marker for tumors of colorectal origin : Results of a pathology-based clinical prospective study

OBJECTIVES Immunohistochemistry is an important extension to clinical information and morphology, and prevails as an invaluable tool for establishing a correct cancer diagnosis in clinical diagnostic pathology. The applicability of immunohistochemistry is limited by the availability of validated cell- and cancer-type specific antibodies, rendering an unmet need to discover, test, and validate novel markers. The SATB2 protein is selectively expressed in glandular cells from the lower gastrointestinal tract and expression is retained in a large majority of primary and metastatic colorectal cancers. METHODS We analyzed the expression of SATB2 in all clinical cases (n = 840), in which immunohistochemistry for detection of CK20 was deemed necessary for a final diagnosis. RESULTS SATB2 showed a high sensitivity (93%) and specificity (77%) to determine a cancer of colorectal origin and in combination with CK7 and CK20, the specificity increased to 100%. CONCLUSIONS We conclude that SATB2 provides a new and advantageous supplement for clinical differential diagnostics.