Diagnostic and prognostic value of metastasis inducer S100A4 transcripts in plasma of colon, rectal, and gastric cancer patients

Differential expression of angiogenesis-related genes 'VEGF' and 'angiopoietin-1' in metastatic and EMAST-positive colorectal cancer patients

Abnormal angiogenesis leads to tumor progression and metastasis in colorectal cancer (CRC). This study aimed to elucidate the association between angiogenesis-related genes, including VEGF-A, ANGPT-1, and ANGPT-2 with both metastatic and microsatellite alterations at selected tetranucleotide repeats (EMAST) subtypes of CRC. We conducted a thorough assessment of the ANGPT-1, ANGPT-2, and VEGF-A gene expression utilizing publicly available RNA sequencing and microarray datasets. Then, the experimental validation was performed in 122 CRC patients, considering their disease metastasis and EMAST+/- profile by using reverse transcription polymerase chain reaction (RT-PCR). Subsequently, a competing endogenous RNA (ceRNA) network associated with these angiogenesis-related genes was constructed and analyzed. The expression level of VEGF-A and ANGPT-2 genes were significantly higher in tumor tissues as compared with normal adjacent tissues (P-value < 0.001). Nevertheless, ANGPT-1 had a significantly lower expression in tumor samples than in normal colon tissue (P-value < 0.01). We identified a significantly increased VEGF-A (P-value = 0.002) and decreased ANGPT-1 (P-value = 0.04) expression in EMAST+ colorectal tumors. Regarding metastasis, a significantly increased VEGF-A and ANGPT-2 expression (P-value = 0.001) and decreased ANGPT-1 expression (P-value < 0.05) were established in metastatic CRC patients. Remarkably, co-expression analysis also showed a strong correlation between ANGPT-2 and VEGF-A gene expressions. The ceRNA network was constructed by ANGPT-1, ANGPT-2, VEGF-A, and experimentally validated miRNAs (hsa-miR-190a-3p, hsa-miR-374c-5p, hsa-miR-452-5p, and hsa-miR-889-3p), lncRNAs (AFAP1-AS1, KCNQ1OT1 and MALAT1), and TFs (Sp1, E2F1, and STAT3). Network analysis revealed that colorectal cancer is amongst the 82 significant pathways. We demonstrated a significant differential expression of VEGF-A and ANGPT-1 in colorectal cancer patients exhibiting the EMAST+ phenotype. This finding provides novel insights into the molecular pathogenesis of colorectal cancer, specifically in EMAST subtypes. Yet, the generalization of in silico findings to EMAST+ colorectal cancer warrants future experimental investigations. In the end, this study proposes that the EMAST biomarker could serve as an additional perspective on CMS4 biology which is well-defined by activated angiogenesis and worse overall survival.

Plasma Circulating mRNA Profile for the Non-Invasive Diagnosis of Colorectal Cancer Using NanoString Technologies

Colorectal cancer (CRC) is one of the most prevalent cancers and the second leading cause of cancer deaths in developed countries. Early CRC may have no symptoms and symptoms usually appear with more advanced diseases. Regular screening can identify people who are at increased risk of CRC in order to offer earlier treatment. A cost-effective non-invasive platform for the screening and monitoring of CRC patients allows early detection and appropriate treatment of the disease, and the timely application of adjuvant therapy after surgical operation is needed. In this study, a cohort of 71 plasma samples that include 48 colonoscopy- and histopathology-confirmed CRC patients with TNM stages I to IV were recruited between 2017 and 2019. Plasma mRNA profiling was performed in CRC patients using NanoString nCounter. Normalized data were analyzed using a Mann-Whitney U test to determine statistically significant differences between samples from CRC patients and healthy subjects. A multiple-group comparison of clinical phenotypes was performed using the Kruskal-Wallis H test for statistically significant differences between multiple groups. Among the 27 selected circulating mRNA markers, all of them were found to be overexpressed (gene expression fold change > 2) in the plasma of patients from two or more CRC stages. In conclusion, NanoString-based targeted plasma CRC-associated mRNAs circulating the marker panel that can significantly distinguish CRC patients from a healthy population were developed for the non-invasive diagnosis of CRC using peripheral blood samples.

Cell-free circulating tumor RNAs in plasma as the potential prognostic biomarkers in colorectal cancer

Background

Cell free RNA (cfRNA) contains transcript fragments from multiple cell types, making it useful for cancer detection in clinical settings. However, the pathophysiological origins of cfRNAs in plasma from colorectal cancer (CRC) patients remain unclear.

Methods

To identify the tissue-specific contributions of cfRNAs transcriptomic profile, we used a published single-cell transcriptomics profile to deconvolute cell type abundance among paired plasma samples from CRC patients who underwent tumor-ablative surgery. We further validated the differentially expressed cfRNAs in 5 pairs of CRC tumor samples and adjacent tissue samples as well as 3 additional CRC tumor samples using RNA-sequencing.

Results

The transcriptomic component from intestinal secretory cells was significantly decreased in the in-house post-surgical cfRNA. The HPGD, PACS1, and TDP2 expression was consistent across cfRNA and tissue samples. Using the Cancer Genome Atlas (TCGA) CRC datasets, we were able to classify the patients into two groups with significantly different survival outcomes.

Conclusions

The three-gene signature holds promise in applying minimal residual disease (MRD) testing, which involves profiling remnants of cancer cells after or during treatment. Biomarkers identified in the present study need to be validated in a larger cohort of samples in order to ascertain their possible use in early diagnosis of CRC.

Combinatorial treatment with statins and niclosamide prevents CRC dissemination by unhinging the MACC1-β-catenin-S100A4 axis of metastasis

Colorectal cancer (CRC) is the second-most common malignant disease worldwide, and metastasis is the main culprit of CRC-related death. Metachronous metastases remain to be an unpredictable, unpreventable, and fatal complication, and tracing the molecular chain of events that lead to metastasis would provide mechanistically linked biomarkers for the maintenance of remission in CRC patients after curative treatment. We hypothesized, that Metastasis-associated in colorectal cancer-1 (MACC1) induces a secretory phenotype to enforce metastasis in a paracrine manner, and found, that the cell-free culture medium of MACC1-expressing CRC cells induces migration. Stable isotope labeling by amino acids in cell culture mass spectrometry (SILAC-MS) of the medium revealed, that S100A4 is significantly enriched in the MACC1-specific secretome. Remarkably, both biomarkers correlate in expression data of independent cohorts as well as within CRC tumor sections. Furthermore, combined elevated transcript levels of the metastasis genes MACC1 and S100A4 in primary tumors and in blood plasma robustly identifies CRC patients at high risk for poor metastasis-free (MFS) and overall survival (OS). Mechanistically, MACC1 strengthens the interaction of β-catenin with TCF4, thus inducing S100A4 synthesis transcriptionally, resulting in elevated secretion to enforce cell motility and metastasis. In cell motility assays, S100A4 was indispensable for MACC1-induced migration, as shown via knock-out and pharmacological inhibition of S100A4. The direct transcriptional and functional relationship of MACC1 and S100A4 was probed by combined targeting with repositioned drugs. In fact, the MACC1-β-catenin-S100A4 axis by statins (MACC1) and niclosamide (S100A4) synergized in inhibiting cancer cell motility in vitro and metastasis in vivo. The MACC1-β-catenin-S100A4 signaling axis is causal for CRC metastasis. Selectively repositioned drugs synergize in restricting MACC1/S100A4-driven metastasis with cross-entity potential.

S100A4 Is a Strong Negative Prognostic Marker and Potential Therapeutic Target in Adenocarcinoma of the Stomach and Esophagus

Deregulated Wnt-signaling is a key mechanism driving metastasis in adenocarcinoma of the gastroesophageal junction and stomach (AGE/S). The oncogene S100A4 was identified as a Wnt-signaling target gene and is known to promote metastasis. In this project, we illuminate the role of S100A4 for metastases development and disease prognosis of AGE/S. Five gastric cancer cell lines were assessed for S100A4 expression. Two cell lines with endogenous high S100A4 expression were used for functional phenotyping including analysis of proliferation and migration after stable S100A4 knock-down. The prognostic value of S100A4 was evaluated by analyzing the S100A4 expression of tissue microarrays with samples of 277 patients with AGE/S. S100A4 knock-down induced lower migration in FLO1 and NCI-N87 cells. Treatment with niclosamide in these cells led to partial inhibition of S100A4 and to reduced migration. Patients with high S100A4 expression showed lower 5-year overall and disease-specific survival. In addition, a larger share of patients in the S100A4 high expressing group suffered from metachronous metastasis. This study identifies S100A4 as a negative prognostic marker for patients with AGE/S. The strong correlation between S100A4 expression, metastases development and patient survival might open opportunities to use S100A4 to improve the prognosis of these patients and as a therapeutic target for intervention in this tumor entity.

Chk1 suppression leads to a reduction in the enhanced radiation-induced invasive capability on breast cancer cells

Radiation therapy is generally effective for treating breast cancers. However, approximately 30% of patients with breast cancer experience occasional post-treatment local and distant metastasis. Low-dose (0.5 Gy) irradiation is a risk factor that promotes the invasiveness of breast cancers. Although an inhibitor of checkpoint kinase 1 (Chk1) suppresses the growth and motility of breast cancer cell lines, no study has investigated the effects of the combined use of a Chk1 inhibitor and radiation on cancer metastasis. Here, we addressed this question by treating the human breast cancer cell line MDA-MB-231 (in vitro) and mouse mammary tumor cell line 4 T1 (in vitro and in vivo) with γ-irradiation and the Chk1 inhibitor PD407824. Low-dose γ-irradiation promoted invasiveness, which was suppressed by PD407824. Comprehensive gene expression analysis revealed that low-dose γ-irradiation upregulated the mRNA and protein levels of S100A4, the both of which were downregulated by PD407824. We conclude that PD407824 suppresses the expression of S100A4. As the result, γ-irradiation-induced cell invasiveness were inhibited.

Quantification of mRNA Expression Using Single-Molecule Nanopore Sensing

RNA quantification methods are broadly used in life science research and in clinical diagnostics. Currently, real-time reverse transcription polymerase chain reaction (RT-qPCR) is the most common analytical tool for RNA quantification. However, in cases of rare transcripts or inhibiting contaminants in the sample, an extensive amplification could bias the copy number estimation, leading to quantification errors and false diagnosis. Single-molecule techniques may bypass amplification but commonly rely on fluorescence detection and probe hybridization, which introduces noise and limits multiplexing. Here, we introduce reverse transcription quantitative nanopore sensing (RT-qNP), an RNA quantification method that involves synthesis and single-molecule detection of gene-specific cDNAs without the need for purification or amplification. RT-qNP allows us to accurately quantify the relative expression of metastasis-associated genes MACC1 and S100A4 in nonmetastasizing and metastasizing human cell lines, even at levels for which RT-qPCR quantification produces uncertain results. We further demonstrate the versatility of the method by adapting it to quantify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA against a human reference gene. This internal reference circumvents the need for producing a calibration curve for each measurement, an imminent requirement in RT-qPCR experiments. In summary, we describe a general method to process complicated biological samples with minimal losses, adequate for direct nanopore sensing. Thus, harnessing the sensitivity of label-free single-molecule counting, RT-qNP can potentially detect minute expression levels of RNA biomarkers or viral infection in the early stages of disease and provide accurate amplification-free quantification.

Decoding and targeting the molecular basis of MACC1-driven metastatic spread: Lessons from big data mining and clinical-experimental approaches

Metastasis remains the key issue impacting cancer patient survival and failure or success of cancer therapies. Metastatic spread is a complex process including dissemination of single cells or collective cell migration, penetration of the blood or lymphatic vessels and seeding at a distant organ site. Hundreds of genes involved in metastasis have been identified in studies across numerous cancer types. Here, we analyzed how the metastasis-associated gene MACC1 cooperates with other genes in metastatic spread and how these coactions could be exploited by combination therapies: We performed (i) a MACC1 correlation analysis across 33 cancer types in the mRNA expression data of TCGA and (ii) a comprehensive literature search on reported MACC1 combinations and regulation mechanisms. The key genes MET, HGF and MMP7 reported together with MACC1 showed significant positive correlations with MACC1 in more than half of the cancer types included in the big data analysis. However, ten other genes also reported together with MACC1 in the literature showed significant positive correlations with MACC1 in only a minority of 5 to 15 cancer types. To uncover transcriptional regulation mechanisms that are activated simultaneously with MACC1, we isolated pan-cancer consensus lists of 1306 positively and 590 negatively MACC1-correlating genes from the TCGA data and analyzed each of these lists for sharing transcription factor binding motifs in the promotor region. In these lists, binding sites for the transcription factors TELF1, ETS2, ETV4, TEAD1, FOXO4, NFE2L1, ELK1, SP1 and NFE2L2 were significantly enriched, but none of them except SP1 was reported in combination with MACC1 in the literature. Thus, while some of the results of the big data analysis were in line with the reported experimental results, hypotheses on new genes involved in MACC1-driven metastasis formation could be generated and warrant experimental validation. Furthermore, the results of the big data analysis can help to prioritize cancer types for experimental studies and testing of combination therapies.

Ca2+-Binding Proteins of the EF-Hand Superfamily: Diagnostic and Prognostic Biomarkers and Novel Therapeutic Targets

A multitude of Ca²⁺-sensor proteins containing the specific Ca²⁺-binding motif (helix-loop-helix, called EF-hand) are of major clinical relevance in a many human diseases. Measurements of troponin, the first intracellular Ca-sensor protein to be discovered, is nowadays the "gold standard" in the diagnosis of patients with acute coronary syndrome (ACS). Mutations have been identified in calmodulin and linked to inherited ventricular tachycardia and in patients affected by severe cardiac arrhythmias. Parvalbumin, when introduced into the diseased heart by gene therapy to increase contraction and relaxation speed, is considered to be a novel therapeutic strategy to combat heart failure. S100 proteins, the largest subgroup with the EF-hand protein family, are closely associated with cardiovascular diseases, various types of cancer, inflammation, and autoimmune pathologies. The intention of this review is to summarize the clinical importance of this protein family and their use as biomarkers and potential drug targets, which could help to improve the diagnosis of human diseases and identification of more selective therapeutic interventions.

Circulating MACC1 Transcripts in Glioblastoma Patients Predict Prognosis and Treatment Response

Glioblastoma multiforme is the most aggressive primary brain tumor of adults, but lacks reliable and liquid biomarkers. We evaluated circulating plasma transcripts of metastasis-associated in colon cancer-1 (MACC1), a prognostic biomarker for solid cancer entities, for prediction of clinical outcome and therapy response in glioblastomas. MACC1 transcripts were significantly higher in patients compared to controls. Low MACC1 levels clustered together with other prognostically favorable markers. It was associated with patients’ prognosis in conjunction with the isocitrate dehydrogenase (IDH) mutation status: IDH1 R132H mutation and low MACC1 was most favorable (median overall survival (OS) not yet reached), IDH1 wildtype and high MACC1 was worst (median OS 8.1 months), while IDH1 wildtype and low MACC1 was intermediate (median OS 9.1 months). No patients displayed IDH1 R132H mutation and high MACC1. Patients with low MACC1 levels receiving standard therapy survived longer (median OS 22.6 months) than patients with high MACC1 levels (median OS 8.1 months). Patients not receiving the standard regimen showed the worst prognosis, independent of MACC1 levels (low: 6.8 months, high: 4.4 months). Addition of circulating MACC1 transcript levels to the existing prognostic workup may improve the accuracy of outcome prediction and help define more precise risk categories of glioblastoma patients.

Clinical relevance of circulating MACC1 and S100A4 transcripts for ovarian cancer

Metastasis‐associated in colon cancer 1 (MACC1) and S100 calcium‐binding protein A4 (S100A4) are prominent inducers of tumor progression and metastasis. For the first time, we systematically tracked circulating serum levels of MACC1 and S100A4 transcripts in the course of surgery and chemotherapy and analyzed their clinical relevance for ovarian cancer. MACC1 and S100A4 transcripts were quantified in a total of 318 serum samples from 79 ovarian cancer patients by RT‐qPCR and digital droplet PCR, respectively. MACC1 and S100A4 transcripts were significantly elevated in serum of ovarian cancer patients, compared to healthy controls (P = 0.024; P < 0.001). At primary diagnosis, high levels of MACC1 or S100A4 correlated with advanced FIGO stage (P = 0.042; P = 0.008), predicted suboptimal debulking surgery and indicated shorter progression‐free survival (PFS; P = 0.003; P = 0.001) and overall survival (OS; P = 0.001; P = 0.002). This is the first study in ovarian cancer to propose circulating MACC1 and S100A4 transcripts as potential liquid biopsy markers.

The Use of Circulating Tumor DNA for Prognosis of Gastrointestinal Cancers

Gastrointestinal cancers, including oesophageal, gastric and colorectal cancers (CRC) have high rates of disease recurrence despite curative resection. There are a number of recent studies that have investigated the use of circulating tumor DNA (ctDNA) for prognostic value in these cancers. We reviewed studies that had been published prior to March 2018 that assessed the prognostic values of ctDNA in patients with oesophageal and gastric cancers, gastrointestinal stromal tumors (GIST) and CRC. We identified 63 eligible clinical studies that focussed on recurrence and survival. Studies assessed investigated various ctDNA biomarkers in patients with different stages of cancer undergoing surgical resection, chemotherapy and no treatment. For oesophageal squamous cell carcinoma and oesophageal adenocarcinoma, methylation of certain genes such as APC and DAPK have been highlighted as promising biomarkers for prognostication, but these studies are limited and more comprehensive research is needed. Studies focusing on gastric cancer patients showed that methylation of ctDNA in SOX17 and APC were independently associated with poor survival. Two studies demonstrated an association between ctDNA and recurrence and survival in GIST patients, but more studies are needed for this type of gastrointestinal cancer. A large proportion of the literature was on CRC which identified both somatic mutations and DNA methylation biomarkers to determine prognosis. ctDNA biomarkers that identified somatic mutations were more effective if they were personalized based on mutations found in the primary tumor tissue, but ctDNA methylation studies identified various biomarkers that predicted increased risk of recurrence, poor disease free survival and overall survival. While the use of non-invasive ctDNA biomarkers for prognosis is promising, larger studies are needed to validate the clinical utility for optimizing treatment and surveillance strategies to reduce mortality from gastrointestinal cancers.

S100A4 May Be a Good Prognostic Marker and a Therapeutic Target for Colon Cancer

Background

Globally, the colorectal cancers rank the third in terms of cancer incidence and rank the fourth in cancer-associated deaths. S100A4, an important member of the S100 protein family, serves to promote tumor progression and metastasis. By conducting this study, we aim to examine the role of S100A4 in the prognosis of colon cancer and to demonstrate its prognostic significance.

Methods

Tissue samples of colon cancer from 148 patients who underwent colon resection due to colon cancer were analyzed by immunohistochemical staining to determine the protein expression levels of S100A4. The protein expression levels of S100A4 in tumor tissue were matched with the clinicopathologic factors including patient survival.

Results

Cytoplasmic expression of S100A4 protein was demonstrated in the tumor tissue of 132 patients (89.2%) out of a total of 148 study patients. Statistically, the expression levels of the cytoplasmic S100A4 protein correlated significantly with the TNM stages and patient survival. The distribution of the S100A4 protein staining in the tumor tissue was associated with the age groups, tumor localization, TNM staging, and patient survival with statistical significance. The levels of S100A4 protein expression were found to be an independent prognostic factor for TNM staging and poor survival.

Conclusion

Expression of the S100A4 protein in colon cancers may be an indicator of tumor progression and lymph node metastasis and may be useful for predicting the overall survival of the patients with colon cancer. In patients with colon cancer, it may be used as an indicator of poor prognosis.

The Effect of Centrifugal Force in Quantification of Colorectal Cancer-Related mRNA in Plasma Using Targeted Sequencing

In our previous study, we detected the effects of centrifugal forces on plasma RNA quantification by quantitative reverse transcription PCR. The aims of this study were to perform targeted mRNA sequencing and data analysis in healthy donors' plasma prepared by two centrifugation protocols and to investigate the effects of centrifugal forces on plasma mRNA quality and quantity. Targeted mRNA sequencing was performed using a custom panel with 108 colorectal cancer-related genes in 18 healthy donors' plasma that prepared by (1) 3,500 g for 10 min at 4°C and (2) 1,600 g for 10 min at 4°C followed by 16,000 g for 10 min at 4°C. Results showed that plasma ribosomal RNA was detected in 16/18 (88.9%) 3,500 g and 6/18 (33.3%) 1,600 g followed by 16,000 g centrifuged plasma. For targeted sequencing, 75/108 (69.4%) and 86/108 (79.6%) genes were detected in 3,500 and 1,600 g followed by 16,000 g, respectively, while 16/108 (14.8%) genes were not detected in both centrifugations. Detailed analysis showed that 2 of 108 (1.85%) genes showed lower expressions in 3,500 g than in 1,600 g followed by 16,000 g. The median expressions of genes in 3,500 g were positively correlated with the expressions in 1,600 g followed by 16,000 g (R² = 0.9471, P < 0.0001, Spearman rank correlation). Meanwhile, plasma samples were not distinctively clustered based on centrifugal forces according to hierarchical clustering. Targeted mRNA sequencing and subsequent data analysis were performed in this study to investigate the effects of two different centrifugal forces that are commonly used in plasma collection. Our targeted sequencing results help to understand the centrifugal force effects on plasma mRNA, and these findings show that the centrifugation protocol for plasma mRNA research using targeted sequencing can be standardized which facilitates multicenter studies for comparison and quality assurance in the future.

STK31 as novel biomarker of metastatic potential and tumorigenicity of colorectal cancer

Purpose

Colorectal cancer (CRC) is the fifth most common cause of cancer deaths in China and fourth worldwide. Metastatic dissemination of primary tumors is considered main cause for CRC related mortality. The serine–threonine kinase 31 (STK31) gene is a novel cancer testis (CT) antigen. It was found significantly highly expressed in gastrointestinal cancers. In our study we aimed to analyze the correlation between STK31 expression patterns and metastasization, tumor stage and grade in CRC patients.

RESULTS

Relative STK31 expression level was significantly higher in patients with lymph node metastasis. STK31 expression levels in primary tumorous tissues of metastatic patients were significantly higher than in ANCTs and in lymph nodes samples, both at the RNA level and the protein level.

Materials and Methods

Surgical specimens of cancerous tissues, paired with adjacent noncancerous tissues, and lymph nodes from 44 CRC cases with different clinicopathological features were collected. Expression of STK31 was detected and measured by immunohistochemistry and quantitative real-time polymerase chain reaction (QRT-PCR).

Conclusions

Our data suggest that STK31 might be a potential biomarker in detecting, monitoring and predicting the metastatic risk of colorectal cancer.

Metastasis-associated in colon cancer 1: A promising biomarker for the metastasis and prognosis of colorectal cancer

Colorectal cancer (CRC) is the fourth most frequent type of malignancy in the world. Metastasis accounts for >90% mortalities in patients with CRC. The metastasis-associated in colon cancer 1 (MACC1) gene has been identified as a novel biomarker for the prediction of metastasis and disease prognosis, particularly for patients with early-stage disease. Previous clinical studies demonstrated that MACC1 expression and polymorphisms in CRC tissues were indicators of metastasis, and that circulating transcripts in plasma were also significantly associated with the survival of patients. The present review describes the use of MACC1 beyond its utility in the clinic. By elucidating the upstream and downstream signal pathways of MACC1, the well-known mechanisms of MACC1-mediated cell proliferation, invasion, migration and epithelial-mesenchymal transition (EMT) are summarized, as well as the potential signaling pathways. Furthermore, the underlying mechanisms by which the overexpression of MACC1 causes cisplatin resistance are emphasized.

S100A4 in cancer progression and metastasis: A systematic review

Metastasis is the leading cause of cancer-related death and directly associates with cancer progression, resistance to anticancer therapy, and poor patient survival. Current efforts focusing on the underlying molecular mechanisms of cancer metastasis attract a special attention to cancer researchers. The epithelial-mesenchymal transition is a complex of molecular program during embryogenesis, inflammation, tissue fibrosis, and cancer progression and metastasis. S100A4, an important member of S100 family proteins, functions to increase the tumor progression and metastasis. The molecular mechanisms of S100A4 involving in the progression and metastasis are diverse in various malignant tumors. Detection of S100A4 expression becomes a promising candidate biomarker in cancer early diagnosis and prediction of cancer metastasis and therefore, S100A4 may be a therapeutic target. This review summarized up to date advancement on the role of S100A4 in human cancer development, progression, and metastasis and the underlying molecular events and then strategies to target S100A4 expression experimentally.

Underlying Mechanisms for Distant Metastasis - Molecular Biology

BACKGROUND

The formation of distant metastases constitutes a complex process with a variety of different genes and pathways involved. To improve patient survival, it is necessary to understand the underlying mechanisms of metastasis to allow for targeted intervention.

METHODS

This review provides an overview of the general concepts of metastasis, focusing on the most important genes and pathways involved and on interventional strategies.

RESULTS

Cancer cells undergo different steps to form metastasis: most prominently, local invasion, intravasation, survival in the circulation, arrest at a distant organ site and extravasation, micrometastasis formation, and metastatic colonization. In order to pass these steps, different molecular pathways are of major importance: EGF/RAS/RAF/MEK/ERK, PI3K/Akt/mTOR, HGF/Met, Wnt/β-catenin, and VEGF signaling. The HGF/Met regulator MACC1 and the Wnt signaling target S100A4 have been shown to play a major role in the metastatic process. Each gene and pathway provides an opportunity for therapeutic intervention.

CONCLUSION

Since metastasis represents a highly limiting factor in cancer therapy causing 90% of cancer deaths, it is imperative to reveal the underlying mechanisms. This is fundamental for uncovering prognostic markers and new targeted therapy options.

S100A4 Protein in Inflammatory Bowel Disease: Results of a Single Centre Prospective Study

INTRODUCTION

The aim of our study was to assess association of serum S100A4 protein with ulcerative colitis (UC) and Crohn's disease (CD).

METHODS

Study included 118 subjects: 93 patients with CD, 16 with UC and 9 controls. In CD group, 20/93 patients had B1 phenotype, 19/93 B2, 20/93 B3 and 34/93 B2 + B3. L1 involvement was present in 15/93, L2 in 14/93 and L3 in 64/93 patients. Serum S100A4 concentration was investigated in peripheral venous blood samples by means of ELISA.

RESULTS

Serum S100A4 was significantly higher in UC (158.6 ± 56.2 ng/mL), p = 0.019 and in CD (154.4 ± 52.1 ng/mL), p = 0.007 compared to controls (104.8 ± 40.5 ng/mL). No difference in S100A4 was revealed between UC and CD, p > 0.05. Serum S100A4 in each CD subgroup (according to behaviour) was significantly higher compared to controls, p < 0.05. Serum S100A4 was significantly higher in L2 (144.6 ± 44.2 ng/mL), p = 0.041 and in L3 (163.0 ± 52.8 ng/mL), p = 0.002 compared to controls and in L3 compared to L1 (126.9 ± 47.6 ng/mL), p = 0.017.

CONCLUSION

Association of serum S100A4 protein with UC and CD was confirmed. In CD, disease behaviour did not influence serum concentration of S100A4 protein. In CD, higher levels of serum S100A4 were observed in patients with ileo-colonic and colonic involvement compared to those with isolated small bowel involvement.

Methylation of serum SST gene is an independent prognostic marker in colorectal cancer

There is an increasing demand for accurate prognostication for colorectal cancer (CRC). This study sought to assess prognostic potentials of methylation targets in the serum of CRC patients. A total of 165 CRC patients were enrolled in this prospective study. Promoter methylation levels of seven genes in pre-operative sera and matched tumor tissues were evaluated by quantitative methylation-specific PCR. Kaplan-Meier test, and univariate and multivariate Cox proportional hazards regression models were used for survival analyses. After a median follow-up of 56 months, 43 patients (28.7%) experienced tumor recurrence. In univariate survival analyses, serum methylation levels of SST and MAL were significantly predictive of cancer-specific death (P<0.005 for both). The former was also a significant predictor for tumor recurrence (P=0.007). Independent prognostic effects of serum methylation levels of SST were revealed by multivariate Cox regression model (P=0.031 and P=0.003 for cancer death and recurrence, respectively). When focusing on stage II and III patients, prognostication with serum methylated SST remained significant. Methylated SST detected in all serum samples can be traced back to the matched primary tumor tissues. We believe that methylated SST detected in the pre-operative sera of CRC patients appear to be a novel promising prognostic marker and probably can be auxiliary to tumor staging system and serum carcinoembryonic antigen towards better risk stratification.

S100A4 in Cancer Metastasis: Wnt Signaling-Driven Interventions for Metastasis Restriction

The aberrant activity of Wnt signaling is an early step in the transformation of normal intestinal cells to malignant tissue, leading to more aggressive tumors, and eventually metastases. In colorectal cancer (CRC), metastasis accounts for about 90% of patient deaths, representing the most lethal event during the course of the disease and is directly linked to patient survival, critically limiting successful therapy. This review focuses on our studies of the metastasis-inducing gene S100A4, which we identified as transcriptional target of β-catenin. S100A4 increased migration and invasion in vitro and metastasis in mice. In patient CRC samples, high S100A4 levels predict metastasis and reduced patient survival. Our results link pathways important for tumor progression and metastasis: the Wnt signaling pathway and S100A4, which regulates motility and invasiveness. S100A4 suppression by interdicting Wnt signaling has potential for therapeutic intervention. As proof of principle, we applied S100A4 shRNA systemically and prevented metastasis in mice. Furthermore, we identified small molecule inhibitors from high-throughput screens of pharmacologically active compounds employing an S100A4 promoter-driven reporter. Best hits act, as least in part, via intervening in the Wnt pathway and restricted metastasis in mouse models. We currently translate our findings on restricting S100A4-driven metastasis into clinical practice. The repositioned FDA-approved drug niclosamide, targeting Wnt signaling, is being tested in a prospective phase II clinical trial for treatment of CRC patients. Our assay for circulating S100A4 transcripts in patient blood is used to monitor treatment success.

Repositioning of drugs for intervention in tumor progression and metastasis: Old drugs for new targets

The increasing unraveling of the molecular basis of cancer offers manifold novel options for intervention strategies. However, the discovery and development of new drugs for potential clinical applications is a tremendously time-consuming and costly process. Translating a novel lead candidate compound into an approved clinical drug takes often more than a decade, and the success rate is very low due to versatile efforts including defining its pharmacokinetics, pharmacodynamics, side effects as well as lack of sufficient efficacy. Thus, strategies are needed to minimize time and costs, while maximizing success rates. A very attractive strategy for novel cancer therapeutic options is the repositioning of already approved drugs. These medicines, approved for the treatment of non-malignant disorders, have already passed some early costs and time, have been tested in humans and are ready for clinical trials as anti-cancer drugs. Here we discuss the repositioning of nonsteroidal anti-inflammatory drugs (NSAID), statins, anti-psychotic drugs, anti-helminthic drugs and vitamin D as anti-tumor agents. We focus on their novel actions and potential for inhibition of cancer growth and metastasis by interfering with target molecules and pathways, which drive these malignant processes. Furthermore, important pre-clinical and clinical data are reviewed herein, which elucidate their therapeutic mechanisms which enable their repositioning for cancer therapy and disruption of metastasis.

RAGE mediates S100A4-induced cell motility via MAPK/ERK and hypoxia signaling and is a prognostic biomarker for human colorectal cancer metastasis

Survival of colorectal cancer patients is strongly dependent on development of distant metastases. S100A4 is a prognostic biomarker and inducer for colorectal cancer metastasis. Besides exerting intracellular functions, S100A4 is secreted extracellularly. The receptor for advanced glycation end products (RAGE) is one of its interaction partners. The impact of the S100A4-RAGE interaction for cell motility and metastasis formation in colorectal cancer has not been elucidated so far. Here we demonstrate the RAGE-dependent increase in migratory and invasive capabilities of colorectal cancer cells via binding to extracellular S100A4. We show the direct interaction of S100A4 and RAGE, leading to hyperactivated MAPK/ERK and hypoxia signaling. The S100A4-RAGE axis increased cell migration (P<0.005) and invasion (P<0.005), which was counteracted with recombinant soluble RAGE and RAGE-specific antibodies. In colorectal cancer patients, not distantly metastasized at surgery, high RAGE expression in primary tumors correlated with metachronous metastasis, reduced overall (P=0.022) and metastasis-free survival (P=0.021).

In summary, interaction of S100A4-RAGE mediates S100A4-induced colorectal cancer cell motility. RAGE by itself represents a biomarker for prognosis of colorectal cancer. Thus, therapeutic approaches targeting RAGE or intervening in S100A4-RAGE-dependent signaling early in tumor progression might represent alternative strategies restricting S100A4-induced colorectal cancer metastasis.

Circulating MACC1 as a novel diagnostic and prognostic biomarker for nonsmall cell lung cancer

PURPOSE

Metastasis-associated in colon cancer-1 (MACC1) is a newly identified gene that plays an important role in cancer progression and metastasis. MACC1 has important functions in the differentiation, invasion, and metastasis of nonsmall cell lung cancer (NSCLC). However, the value of circulating MACC1 as a potential diagnostic and prognostic biomarker for NSCLC remains unknown.

METHODS

Plasma MACC1 mRNA levels were examined in 272 patients with NSCLC, 61 with benign lung disease, and 80 healthy volunteers using reverse transcription quantitative real-time polymerase chain reaction.

RESULTS

MACC1 was more highly expressed in NSCLC patients than in patients with benign disease (P < 0.001) or in healthy volunteers (P < 0.001). High MACC1 expression was significantly associated with NSCLC stage (P = 0.013) and lymph node metastasis (P = 0.016). The area under the receiver operating characteristic curve was 0.766, and the optimal cutoff value was 0.105, providing a sensitivity of 71.4 % and a specificity of 89.1 %. The diagnostic capability of circulating MACC1 mRNA was higher than that of carcinoembryonic antigen (P = 0.025) or cytokeratin-19 (P = 0.010). Furthermore, high MACC1 expression was associated with poor overall survival (OS) and disease-free survival (DFS) and predicted poor survival in NSCLC patients. Consequently, MACC1 mRNA was an independent prognostic factor of OS and DFS.

CONCLUSION

We concluded that circulating MACC1 mRNA represents a potential noninvasive, diagnostic and prognostic marker for NSCLC.

Meta-analysis shows that circulating tumor cells including circulating microRNAs are useful to predict the survival of patients with gastric cancer

Background

Circulating tumor cells (CTCs) are metastatic cells disseminated into the bloodstreams. They have been proposed to monitor disease progression for decades. However, the prognostic value of CTCs in gastric cancer (GC) remains controversial. We performed a meta-analysis to investigate the topic.

Methods

A systematic search was made for relevant studies in academic data bases, involving the Medline, Embase, and Science Citation Index. Data on prognosis of GC patients, such as recurrence-free survival (RFS) and overall survival (OS), were extracted when possible. The meta-analysis was performed with the random effects model and the pooled hazard ratios (HRs) and their associated 95% confident intervals (95%CIs) were computed as effect measures.

Results

Twenty six studies (including 40 subgroups) with peripheral blood samples of 1950 cases from 10 countries were included in the final analysis. The pooled results showed that GC patients with detectable CTCs (including circulating miRNAs) had a tendency to experience shortened RFS (HR = 2.91, 95% CI [1.84-4.61], I² = 52.18%, n = 10). As for patient deaths, we found a similar association of CTC (including circulating miRNAs) presence with worse OS (HR = 1.78, 95% CI [1.49-2.12], I² = 30.71%, n = 30). Additionally, subgroup analyses indicated strong prognostic powers of CTCs, irrespective of geographical, methodological, detection time and sample size differences of the studies.

Conclusions

Our meta-analysis shows that CTCs (including circulating miRNAs) can predict the survival of GC patients. Large prospective studies are warranted to determine the best sampling time points, detection methods in homogeneous patients with GC in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-773) contains supplementary material, which is available to authorized users.

Clinicopathological and prognostic value of S100A4 expression in gastric cancer: a meta-analysis

PURPOSES

For several years S100A4 has been implicated in tumor progression and prognosis. However, the prognostic value of S100A4 overexpression in patients with gastric cancer remains unknown. Therefore, we performed a meta-analysis to assess the relationship between S100A4 overexpression and clinical outcome of gastric cancer.

METHODS AND RESULTS

Candidate studies were searched from PubMed, Embase, Cochrane Library, and ISI Web of Science. We included studies that evaluated the prognostic value of S100A4 expression in gastric cancer patients with regard to survival and a series of clinicopathological parameters. The pooled hazard ratios (HR) and odds ratios (OR) with 95% confidence intervals (CI) were used to estimate the effects. Ten studies, all from Asia, were included in the meta-analysis. The pooled analysis showed that S100A4 overexpression was significantly associated with worse overall survival (OS) (HR=1.86, 95% CI: 1.45-2.38, p<0.00001) without heterogeneity in the data (I2=43.6%, p=0.131). Furthermore, our results showed that S100A4 overexpression was significantly correlated with some clinicopathological parameters such as tumor grade, stage, metastasis, invasion, and relapse.

CONCLUSIONS

The results of our meta-analysis indicate that S100A4 overexpression correlates with more adverse clinical features and a poor prognosis of gastric cancer patients in Asia, thus suggesting that S100A4 could be a useful marker to evaluate progression and prognosis of Asian gastric cancer patients. More studies from Western countries with a larger number of tumors and standardized methods are required before significant conclusions can be drawn.

Postoperative serum methylation levels of TAC1 and SEPT9 are independent predictors of recurrence and survival of patients with colorectal cancer

BACKGROUND

Serum carcinoembryonic antigen (CEA) is the only marker recommended for surveillance of colorectal cancer (CRC) recurrence; its sensitivity and specificity, however, are suboptimal. This study sought to evaluate the values of postoperative serum methylation levels of 7 genes for prognostication and especially for recurrence detection after curative resection.

METHODS

This prospective cohort study included 150 patients with stage I-III CRC from whom 3 consecutive blood sampling was taken 1 week before, and 6 months and 1 year after operation. Methylation levels of 7 genes were evaluated via quantitative methylation-specific polymerase chain reaction. Serum CEA was measured in parallel. Univariate and multivariate survival analyses were followed by construction of receiver operating characteristic curves for recurrence detection.

RESULTS

After a median follow-up of 59 months, 43 patients (28.7%) developed recurrent lesions. High serum methylation levels of TAC1 in serum at 6-month follow-up (6M-FU), and SEPT9 at 1-year follow-up (1Y-FU) were independent predictors for tumor recurrence and unfavorable cancer-specific survival (CSS) (P < .05 in all tests). Serum NELL1 methylation levels were significant alone for CSS at both 6M-FU and 1Y-FU, but not for disease-free survival. Dynamic changes of TAC1 and SEPT9 with methylation increment were also independently predictive for recurrence (P < .05 in all tests). More importantly, TAC1 at 6M-FU and SEPT9 at 1Y-FU exhibited earlier detection of potential recurrences compared with concurrent serum CEA.

CONCLUSIONS

Levels of TAC1 and SEPT9 methylation detected in postoperative sera of patients with CRC appear to be novel promising prognostic markers and may probably be considered for monitoring of CRC recurrence.

S100 protein family in human cancer

S100 protein family has been implicated in multiple stages of tumorigenesis and progression. Among the S100 genes, 22 are clustered at chromosome locus 1q21, a region frequently rearranged in cancers. S100 protein possesses a wide range of intracellular and extracellular functions such as regulation of calcium homeostasis, cell proliferation, apoptosis, cell invasion and motility, cytoskeleton interactions, protein phosphorylation, regulation of transcriptional factors, autoimmunity, chemotaxis, inflammation and pluripotency. Many lines of evidence suggest that altered expression of S100 proteins was associated with tumor progression and prognosis. Therefore, S100 proteins might also represent potential tumor biomarkers and therapeutic targets. In this review, we summarize the evidence connecting S100 protein family and cancer and discuss the mechanisms by which S100 exerts its diverse functions.

Clinicopathological and prognostic significance of S100A4 overexpression in colorectal cancer: a meta-analysis

Background

Accumulated evidence has indicated a correlation between S100A4 expression and colorectal cancer (CRC) progression. However, its prognostic significance for patients with CRC remains inconclusive. To clarify their relationship, a meta-analysis of the relevant published studies was performed.

Method

PubMed, Cochrane Library, and Web of Science databases were electronically searched. All studies evaluating the prognostic value of S100A4 expression in CRC patients regarding survival and a series of clinicopathological parameters were included. The effect of S100A4 expression on the overall survival (OS) and disease-free survival (DFS) were measured by pooled hazard ratios (HRs) and 95% confidence intervals (CIs), while the effect of S100A4 expression on the clinicopathological parameters were measured by the pooled odds ratios (ORs) and their 95% CIs.

Results

Eleven studies (2,824 patients in total) were included in the meta-analysis. Overall, S100A4 overexpression was significantly associated with worse OS (HR = 1.90, 95% CI: 1.58–2.29, P <0.001), and worse DFS (HR = 2.16, 95% CI: 1.53–3.05, P <0.001) in patients with CRC. Subgroup analyses showed that S100A4 overexpression was significantly correlated with poor OS in Asian, European, and Australian patients and patients treated with surgery or chemotherapy. Additionally, there were significant associations between S100A4 expression and several clinicopathological parameters (tumour location, lymph node metastasis, nodal status, TNM stage, and tumour depth).

Conclusions

This meta-analysis indicates that S100A4 overexpression seems to correlate with tumour progression and poor prognosis of CRC patients. It may be a useful marker to predict progression and prognosis of CRC.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8643820431072915

Functions of S100 proteins

The S100 protein family consists of 24 members functionally distributed into three main subgroups: those that only exert intracellular regulatory effects, those with intracellular and extracellular functions and those which mainly exert extracellular regulatory effects. S100 proteins are only expressed in vertebrates and show cell-specific expression patterns. In some instances, a particular S100 protein can be induced in pathological circumstances in a cell type that does not express it in normal physiological conditions. Within cells, S100 proteins are involved in aspects of regulation of proliferation, differentiation, apoptosis, Ca2+ homeostasis, energy metabolism, inflammation and migration/invasion through interactions with a variety of target proteins including enzymes, cytoskeletal subunits, receptors, transcription factors and nucleic acids. Some S100 proteins are secreted or released and regulate cell functions in an autocrine and paracrine manner via activation of surface receptors (e.g. the receptor for advanced glycation end-products and toll-like receptor 4), G-protein-coupled receptors, scavenger receptors, or heparan sulfate proteoglycans and N-glycans. Extracellular S100A4 and S100B also interact with epidermal growth factor and basic fibroblast growth factor, respectively, thereby enhancing the activity of the corresponding receptors. Thus, extracellular S100 proteins exert regulatory activities on monocytes/macrophages/microglia, neutrophils, lymphocytes, mast cells, articular chondrocytes, endothelial and vascular smooth muscle cells, neurons, astrocytes, Schwann cells, epithelial cells, myoblasts and cardiomyocytes, thereby participating in innate and adaptive immune responses, cell migration and chemotaxis, tissue development and repair, and leukocyte and tumor cell invasion.

Circulating MACC1 transcripts in colorectal cancer patient plasma predict metastasis and prognosis

Background

Metastasis is the most frequent cause of treatment failure and death in colorectal cancer. Early detection of tumors and metastases is crucial for improving treatment strategies and patient outcome. Development of reliable biomarkers and simple tests routinely applicable in the clinic for detection, prognostication, and therapy monitoring is of special interest. We recently identified the novel gene Metastasis-Associated in Colon Cancer 1 (MACC1), a key regulator of the HGF/Met-pathway. MACC1 is a strong prognostic biomarker for colon cancer metastasis and allows identification of high-risk subjects in early stages, when determined in patients’ primary tumors. To overcome the limitation of a restricted number of molecular analyses in tumor tissue, the establishment of a non-invasive blood test for early identification of high-risk cancer patients, for monitoring disease course and therapy response is strongly needed.

Methodology/Principal Findings

For the first time, we describe a non-invasive assay for quantification of circulating MACC1 transcripts in blood of more than 300 colorectal cancer patients. MACC1 transcript levels are increased in all disease stages of the cancer patients compared to tumor-free volunteers. Highest MACC1 levels were determined in individuals with metastases (all P<0.05). Importantly, high MACC1 levels correlate with unfavorable survival (P<.0001). Combining MACC1 with circulating transcripts of the metastasis gene S100A4, a transcriptional target of the Wnt/β-catenin-pathway, improves survival prediction for newly diagnosed cancer patients.

Conclusion/Significance

This blood-based assay for circulating MACC1 transcripts, which can be quantitated on a routine basis, is clinically applicable for diagnosis, prognosis, and therapeutic monitoring of cancer patients. Here we demonstrate the diagnostic and prognostic value of circulating MACC1 transcripts in patient plasma for metastasis and survival. Since MACC1 represents a promising target for anti-metastatic therapies, circulating MACC1 transcripts may prove to be an ideal read-out for monitoring therapeutic response of future interventions targeting MACC1-induced metastasis in cancer patients.

High-throughput screening strategies for targeted identification of therapeutic compounds in colorectal cancer

Recent advancements in understanding the role of both genetics and molecular pathways in the formation and progression of colorectal cancer have allowed the identification of factors that may be targeted for drug discovery. During the past decade, various approaches have been developed to target specific steps or components of these pathways in order to prevent the development and progression of colorectal cancer and to treat this disease. The innovation and optimization of high-throughput screening methods, as well as the recent emphasis from the NIH on translational sciences, have enabled rapid progress in drug discovery in many fields, including colorectal cancer. Here we present a summary of the recent efforts of targeted high-throughput drug discovery directed at pathways affected in colorectal cancer.

S100A4 silencing blocks invasive ability of esophageal squamous cell carcinoma cells

AIM: To investigate a potential role of S100A4 in esophagus squamous cell carcinoma metastasis (ESCCs).

METHODS: Expression of S100A4 and E-cadherin were analyzed in frozen sections from ESCCs (metastasis, n = 28; non-metastasis, n = 20) by reverse transcription-polymerase chain reaction, quantitative polymerase chain reaction and immunohistochemistry. To explore the influence of S100A4 on esophageal cancer invasion and metastasis, S100A4 was overexpressed or silenced by S100A4 siRNA in TE-13 or Eca-109 cells in vitro and in vivo.

RESULTS: We found the mRNA and protein levels of S100A4 expression in ESCCs was significantly upregulated, and more importantly, that expression of S100A4 and E cadherin are strongly negatively correlated in patients who had metastasis. It was indicated that overexpression of S100A4 in TE-13 and Eca-109 cells downregulates the expression of E-cadherin, leading to increased cell migration in vitro, whereas knockdown of S100A4 inhibited cell migration and upregulation of E-cadherin expression. Moreover, the loss of cell metastatic potential was rescued by overexpression of E-cadherin completely. In addition, nude mice inoculated with S100A4 siRNA-transfected cells exhibited a significantly decreased invasion ability in vivo.

CONCLUSION: S100A4 may be involved in ESCC progression by regulate E-cadherin expression, vector-based RNA interference targeting S100A4 is a potential therapeutic method for human ESCC.

Novel effect of antihelminthic Niclosamide on S100A4-mediated metastatic progression in colon cancer

BACKGROUND

Metastasis formation in colon cancer severely reduces the survival rate in patients. S100A4, a calcium-binding protein, is implicated in promoting metastasis formation in colon cancer.

METHODS

To identify a transcription inhibitor of S100A4, high-throughput screening of 1280 pharmacologically active compounds was performed using a human colon cancer cell line expressing a S100A4 promoter-driven luciferase (LUC) reporter gene construct (HCT116-S1004p-LUC). Niclosamide, an antihelminthic agent, was identified as a potential candidate. Colon cancer cell lines (HCT116, SW620, LS174T, SW480, and DLD-1) were treated with 1 μM niclosamide to analyze the effect on S100A4 mRNA and protein expression by quantitative reverse transcription-polymerase chain reaction and immunoblot assays, and effects on cell migration, invasion, proliferation, and colony formation were also assessed in vitro. The effect of niclosamide on liver metastasis was assessed in a xenograft mouse model of human colon cancer (n = 8 mice) by in vivo imaging. The long-term effect of niclosamide on metastasis formation after discontinued treatment was quantified by scoring, and overall survival (n = 12 mice) was analyzed by Kaplan-Meier method after discontinuation of treatment. All statistical tests were two-sided.

RESULTS

Reduced S100A4 mRNA and protein expression, and inhibited cell migration, invasion, proliferation, and colony formation were observed in niclosamide-treated colon cancer cells in vitro. In vivo imaging of niclosamide-treated mice showed reduced liver metastasis compared with solvent-treated control mice (n = 4 mice per group). Compared with the control group, discontinuation of treatment for 26 days showed reduced liver metastasis formation in mice (n = 6 mice per group) (control vs discontinuous treatment, mean metastasis score = 100% vs 34.9%, mean difference = 65.1%; 95% confidence interval [CI] = 18.4% to 111.9%, P < .01) and increased overall survival (n = 6 mice per group; control vs discontinuous treatment, median survival = 24 vs 46.5 days, ratio = 0.52, 95% CI = 0.19 to 0.84, P = .001).

CONCLUSION

Niclosamide inhibits S100A4-induced metastasis formation in a mouse model of colon cancer and has therapeutic potential.