Regulation of metastasis in colorectal adenocarcinoma: a collision between development and tumor biology

Targeted DNA demethylation of the ZNF334 promoter inhibits colorectal cancer growth

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. Aberrant regulation of DNA methylation in promoters of tumor suppressor genes or proto-oncogenes is one of the fundamental processes driving the initiation and progression of CRC. Zinc-finger proteins (ZNFs) are one of the most abundant groups of proteins and function in many important biological processes related to tumorigenesis. Herein, we detected abnormal hypermethylation of the ZNF334 gene in CRC tissues compared with normal tissues, and this modification downregulated the expression of ZNF334. Furthermore, ten-eleven translocation 1 (TET1) was identified to be involved in regulating the methylation level of ZNF334. Next, a dCas9-multiGCN4/scFv-TET1CD-sgZNF334-targeted demethylation system was constructed to reverse the expression of ZNF334 through sgRNA targeting the ZNF334 promoter. Both in vitro and in vivo experiments demonstrated the targeted demethylation system upregulated ZNF334 expression and inhibited CRC growth. Collectively, targeted DNA demethylation of the ZNF334 promoter sheds light on the precise treatment of CRC.

STAT1 as a potential prognosis marker for poor outcomes of early stage colorectal cancer with microsatellite instability

Proteomic analyses indicate that STAT1 protein (signal transducer and activator of transcription 1 or transcription factor ISGF-3 components p91/p84) is upregulated in some colorectal cancers. This study examined 736 colorectal cancer patients for the expression of STAT1 protein in tissue specimens, including 614 early stage patients and 122 advanced stage patients. Tissue microarrays were constructed, and STAT1 expression was examined by immunohistochemistry and scored semi-quantitatively. Among all cases, 9% of cases displayed high levels of cytoplasmic expression of STAT1 and 15% of cases had positive nuclear expression. Based on statistical analyses of a cohort of 559 early stage patients with survival data and no neoadjuvant therapy, we found that high levels of cytoplasmic expression of STAT1 correlated with shorter survival time in early stage colorectal cancer, particularly of the microsatellite instability (MSI) subtype. Additional analysis of a 244-case cohort of colorectal cancers from the Cancer Genome Atlas found that STAT1 gene expression correlated positively with PD-L1 (CD274) and PD-1 (PDCD1) but had no correlation with KRAS or BRAF mutation status. STAT1 expression showed no clear correlation with any of the 4 clinical diagnostic markers of mismatch repair, MLH1, MSH2, MSH6, and PMS2, suggesting its potential as an independent outcome marker for MSI cancers. Our findings suggest that STAT1 may be used as a potential prognostic protein marker for stratifying the outcome risk of early stage MSI colorectal cancer.

Prolyl 4-hydroxylase alpha 1 protein expression risk-stratifies early stage colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and lethal malignancies. Especially for early stage CRC, prognostic molecular markers are needed to guide therapy. In this study, we first extracted total proteomes from matched pairs of fresh cancer and benign mucosal tissues from 22 CRC patients. Global proteomic profiling with Fourier transform liquid chromatography-mass spectrometry sequencing and label free quantitation uncovered that P4HA1 (prolyl 4-hydroxylase alpha 1) was overexpressed in CRC relative to benign colonic mucosa. We then investigated expression by immunohistochemical staining with P4HA1-specific antibodies using CRC tissue microarrays. Independent validation cohorts of 599 cases of early stage CRC and 91 cases of late stage CRC were examined. Multivariate and univariate survival analyses revealed that high expression of P4HA1 protein was an independent poor prognostic marker for patients with early stage CRC, especially of the microsatellite stable subtype. Our study provides strong support for P4HA1 as a predictive protein marker for precision diagnostics, therapeutic decision-making, and drug development for early stage colorectal cancer and demonstrates the utility of proteomic profiling to identify novel protein biomarkers.

B7-H3 promotes colorectal cancer angiogenesis through activating the NF-κB pathway to induce VEGFA expression

Tumor angiogenesis is a hallmark of cancer and is involved in the tumorigenesis of solid tumors. B7-H3, an immune checkpoint molecule, plays critical roles in proliferation, metastasis and tumorigenesis in diverse tumors; however, little is known about the biological functions and molecular mechanism underlying B7-H3 in regulating colorectal cancer (CRC) angiogenesis. In this study, we first demonstrated that the expression of B7-H3 was significantly upregulated and was positively associated with platelet endothelial cell adhesion molecule-1 (CD31) level in tissue samples from patients with CRC. In addition, a series of in vitro and in vivo experiments showed that conditioned medium from B7-H3 knockdown CRC cells significantly inhibited the migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs), whereas overexpression of B7-H3 had the opposite effect. Furthermore, B7-H3 promoted tumor angiogenesis by upregulating VEGFA expression. Recombinant VEGFA abolished the inhibitory effects of conditioned medium from shB7-H3 CRC cells on HUVEC angiogenesis, while VEGFA siRNA or a VEGFA-neutralizing antibody reversed the effects of conditioned medium from B7-H3-overexpressing CRC cells on HUVEC angiogenesis. Moreover, we verified that B7-H3 upregulated VEGFA expression and angiogenesis by activating the NF-κB pathway. Collectively, our findings identify the B7-H3/NF-κB/VEGFA axis in promoting CRC angiogenesis, which serves as a promising approach for CRC treatment.

Lupeol inhibits growth and migration in two human colorectal cancer cell lines by suppression of Wnt-β-catenin pathway

Background

Lupeol, a triterpene isolated from various herbal plants, possesses an anti-inflammatory function and has been proposed as a candidate for anticancer agents. The purpose of this research was to investigate the effect of lupeol on the viability, apoptosis, cell-cycle distribution, and migration of colorectal cancer cell lines and its molecular mechanism.

Methods

Lupeol was assessed for its anticancer effect using two human colorectal cancer cell lines: SW480 and HCT116. These cells were treated with lupeol, and their viability, apoptosis, migration, and cycle distribution were detected by CCK8, flow cytometry, and the transwell method. Quantitative PCR, Western blot, and immunofluorescence were applied to detect the expressions of CTNNB1, TCF4, cMYC, CCND1, CLDN1, and CCNA2.

Results

Lupeol suppressed cell viability and migration and induced cellular apoptosis of both cell lines, with increased p53 and decreased Bcl2 protein levels (P<0.05). Cell cycles of both lupeol-treated cell lines were arrested in the S phase (P<0.05). Quantitative PCR and Western blot analyses showed significantly reduced expressions of CTNNB1, TCF4, and downstream genes of the Wnt–β-catenin pathway, including the cell-cycle-regulated genes of cMYC and CCND1 of both cell lines upon lupeol treatment (P<0.05). mRNA and protein levels of CLDN1 decreased in HCT116 cells, plus the expression of CCNA2 mRNA and protein decreased in SW480 cells (P<0.05). Immunofluorescence analysis confirmed decreased expression of Wnt–β-catenin signaling.

Conclusion

Our findings indicate that lupeol effectively inhibits proliferation and migration and induces apoptosis and cell-cycle arrest of two colorectal cell lines by inactivation of the Wnt–β-catenin signaling pathway and downregulation of cMYC, CCND1, CCNA2, and CLDN1, thereby making it a promising anticancer candidate.

MicroRNA-423-5p inhibits colon cancer growth by promoting caspase-dependent apoptosis

Plasma microRNA (miR)-423-5p is a potential biomarker for the detection of colon cancer. However, the expression and biological role of miR-423-5p in colon tumorigenesis remains unclear. In the current study, reverse transcription-quantitative polymerase chain reaction was used to determine miR-423-5p expression in malignant colon tissues and plasma from patients with colon cancer. Cell viability, colony formation and apoptosis assays, as well as western blotting, were performed to investigate the biological role and regulatory mechanisms of miR-423-5p in colon cancer. The results demonstrated that miR-423-5p expression was downregulated in tumor tissues and plasma from patients with colon cancer, as well as in colon cancer cell lines. Furthermore, overexpression of miR-423-5p promoted colon cancer cell apoptosis and resulted in the inhibition of cell proliferation and colony formation. Mechanistically, miR-423-5p induced the expression of caspases 3, 8 and 9, as well as p53 in colon cancer. The effect of z-VAD treatment indicated that the miR-423-5p-mediated colon cancer cell apoptosis is caspase-dependent. These results suggest that miR-423-5p is a tumor suppressor in colon cancer and a potential diagnostic target to enable the early detection of colon cancer.

Colorectal Tumors Require NUAK1 for Protection from Oxidative Stress

Exploiting oxidative stress has recently emerged as a plausible strategy for treatment of human cancer, and antioxidant defenses are implicated in resistance to chemotherapy and radiotherapy. Targeted suppression of antioxidant defenses could thus broadly improve therapeutic outcomes. Here, we identify the AMPK-related kinase NUAK1 as a key component of the antioxidant stress response pathway and reveal a specific requirement for this role of NUAK1 in colorectal cancer. We show that NUAK1 is activated by oxidative stress and that this activation is required to facilitate nuclear import of the antioxidant master regulator NRF2: Activation of NUAK1 coordinates PP1β inhibition with AKT activation in order to suppress GSK3β-dependent inhibition of NRF2 nuclear import. Deletion of NUAK1 suppresses formation of colorectal tumors, whereas acute depletion of NUAK1 induces regression of preexisting autochthonous tumors. Importantly, elevated expression of NUAK1 in human colorectal cancer is associated with more aggressive disease and reduced overall survival.Significance: This work identifies NUAK1 as a key facilitator of the adaptive antioxidant response that is associated with aggressive disease and worse outcome in human colorectal cancer. Our data suggest that transient NUAK1 inhibition may provide a safe and effective means for treatment of human colorectal cancer via disruption of intrinsic antioxidant defenses. Cancer Discov; 8(5); 632-47. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 517.

SARI inhibits angiogenesis and tumour growth of human colon cancer through directly targeting ceruloplasmin

SARI, also called as BATF2, belongs to the BATF family and has been implicated in cancer cell growth inhibition. However, the role and mechanism of SARI in tumour angiogenesis are elusive. Here we demonstrate that SARI deficiency facilitates AOM/DSS-induced colonic tumorigenesis in mice. We show that SARI is a novel inhibitor of colon tumour growth and angiogenesis in mice. Antibody array and HUVEC-related assays indicate that VEGF has an essential role in SARI-controlled inhibition of angiogenesis. Furthermore, Co-IP/PAGE/mass spectrometry indicates that SARI directly targets ceruloplasmin (Cp), and induces protease degradation of Cp, thereby inhibiting the activity of the HIF-1α/VEGF axis. Tissue microarray results indicate that SARI expression inversely correlates with poor clinical outcomes in colon cancer patients. Collectively, our results indicate that SARI is a potential target for therapy by inhibiting angiogenesis through the reduction of VEGF expression and is a prognostic indicator for patients with colon cancer.

Promoter methylation analysis of WNT/β-catenin pathway regulators and its association with expression of DNMT1 enzyme in colorectal cancer

BACKGROUND

Aberrant DNA methylation as the most important reason making epigenetic silencing of genes is a main mechanism of gene inactivation in patients with colorectal cancer. In this study, we decided to identify promoter methylation status of ten genes encoding WNT negative regulators, and measure the expression of DNMT1 enzyme in colorectal cancer samples.

RESULTS

Aberrant methylation of APC gene was statistically significant associated with age over 50 (p = 0.017), DDK3 with male (p < 0.0001), SFRP4, WIF1, and WNT5a with increasing tumor stage (p = 0.004, p = 0.029, and p = 0.004), SFRP4 and WIF1 with tumor differentiation (p = 0.009 and p = 0.031) and SFRP2 and SFRP5 with histological type (p = 0.001 and p = 0.025). The increasing number of methylated genes correlated with the expression levels of the DNMT1 mRNA.

CONCLUSIONS

The rate of gene promoter methylation of WNT pathway regulators is high in colorectal cancer cells. Hyper-methylation is associated with increased expression of the DNMT1 enzyme.

Trefoil factor 1 gene alternations and expression in colorectal carcinomas

Aims and background

Aberrant expression of the trefoil factor family (TFF) has been recognized to be involved in the development and/or progression of various solid tumors. Increased trefoil factor 1 (TFF1) expression is found associated with tumor progression in some tumors, and TFF1 missense mutations have been detected in gastric cancer. The aim of the study was to analyze TFF1 alternations and expression in colorectal carcinoma and their correlation with cancer progression and pathological aspects.

Methods

TFF1 mutations were detected in colorectal carcinomas by DNA sequencing. TFF1mRNA and protein levels in subsets of the primary tumors were determined using quantitative reverse transcription polymerase chain reaction and immunohistochemistry analyses. The serum level of TFF1 was also detected by enzyme-linked immunosorbent assay for patients with colorectal carcinoma.

Results

Five variants were detected in the 5'-untranslation region and intron 1 of TFF1. TFF1 expression was increased in colorectal carcinoma compared to paired distal colonic mucosa. Immunohistochemistry in primary colorectal carcinoma showed no significant differences in tumor TFF1 levels with respect to clinicopathological parameters such as the patient's sex, cancer differentiation, stage and lymph node metastasis. However, serum TFF1 levels were significantly elevated in patients with colorectal carcinoma compared to healthy individuals.

Conclusions

The results indicate that TFF1 missense mutations seem to be a rare event in colorectal carcinogenesis. Serum TFF1 may be a potential useful marker for patients with colorectal carcinoma.

Decreased levels of miR-224 and the passenger strand of miR-221 increase MBD2, suppressing maspin and promoting colorectal tumor growth and metastasis in mice

BACKGROUND & AIMS

Little is known about functions of microRNA (miR) passenger strands (miR*) or their roles in tumor development or progression. We screened for miRs and miR* with levels that were altered in metastatic colorectal cancer (CRC) cells and human tumor samples and investigated their targets and effects on cell function and tumor progression in mice.

METHODS

We performed array-based profile analysis to identify miRs with levels that were increased more than 2-fold in metastatic (SW620) CRC cells compared with nonmetastatic (SW480) cells. Quantitative polymerase chain reaction and in situ hybridization analyses were used to measure miRNA levels in CRC cell lines and human tumor samples. We used miRNA duplex mimics or inhibitors to increase and decrease levels of miRNA in CRC cells and assessed their activities and ability to form metastatic xenograft tumors in nude mice.

RESULTS

Levels of miR-221* and miR-224 were reduced in metastatic compared with nonmetastatic CRC cells; levels in human tumor samples correlated inversely with tumor stage and metastasis to lymph nodes as well as patient survival times. SW480 cells transfected with miR-221* or miR-224 inhibitors had increased motility in vitro compared with SW480 control cells and formed larger, more metastatic tumors when injected into mice. SW620 cells transfected with miR-221* or miR-224 mimics had reduced migration and motility in vitro and formed smaller tumors with fewer metastases in mice compared with control SW620 cells. We identified the 3' untranslated region of MBD2 messenger RNA as a target of miR-221* and miR-224. MBD2 silences the gene encoding maspin, a suppressor of metastasis. In CRC cells, we found that miR-221* and miR-224 increase the expression of maspin through MBD2 down-regulation.

CONCLUSIONS

In metastatic CRC cells, reduced levels of miR-221* and miR-224 increase levels of MBD2, thereby decreasing expression of the metastasis suppressor maspin. Increased activities of miR-221* and miR-224 reduce growth and metastasis of CRC xenograft tumors in mice; these miRs might be developed as therapeutic reagents or biomarkers of CRC progression.

Prognostic and diagnostic significance of annexin A2 in colorectal cancer

AIM

Annexin A2 (ANXA2) is known to be a tumourigenic molecule and is highly expressed in colorectal cancer (CRC). Its diagnostic and prognostic value is not fully understood. This study was designed to investigate the relationship between ANXA2 expression, clinicopathological characteristics, tumour recurrence and survival.

METHOD

Immunohistochemical staining was used to evaluate ANXA2 expression in 150 matched samples from patients with CRC. Overall survival and recurrence were determined by Kaplan-Meier analysis. The Cox proportional hazards model was used to determine independent factors contributing to survival and recurrence. Receiver operating characteristic (ROC) curve and liner correlation analysis were used to estimate the sensitivity and specificity of ANXA2 expression for clinical diagnosis.

RESULTS

ANXA2 was found to be strongly expressed in poorly differentiated tumours (P < 0.001), late stage (P = 0.020) and lymph node positivity (P = 0.002). ANXA2 expression was significantly related to recurrence (P < 0.001) and survival (P = 0.002). The Cox proportional hazards model indicated that ANXA2 expression [P < 0.001, hazard ratio (HR) = 1.366, 95% CI 1.232-1.515] and tumour location (P = 0.039, HR = 1.891, 95% CI 1.034-3.456) were independent factors in predicting overall survival while ANXA2 expression (P < 0.001, HR = 1.445, 95% CI 1.222-1.709) were independent factors predicting recurrence. Receiver operating characteristic (ROC) (AUC = 0.768, 95% CI = 0.642-0.894) and liner correlation analysis suggested that ANXA2 was suitable for the clinical diagnosis of CRC.

CONCLUSION

These results indicate that ANXA2 is a biomarker with diagnostic and prognostic potential for patients with CRC.

Oxidative DNA damage and β-catenin expression in colorectal cancer evolution

PURPOSE

Oxidative DNA damage is one of the mechanisms associated to initial colorectal carcinogenesis, but how it interacts with β-catenin, an adherence protein related to cancer evolution, is not clear. This study investigates the relationship between oxidative DNA damage and β-catenin expression in normal mucosa and colon tumor tissue (adenoma and adenocarcinoma) in colorectal adenocarcinoma evolution.

METHOD

One hundred and 13 samples were studied. Hematoxylin-eosin determined histological grade. β-Catenin expression was analyzed by immunohistochemistry. The oxidative DNA damage was evaluated using comet assay technique. The coefficient for rejection of the nullity hypothesis was taken to 5 %. Kruskal-Wallis, Spearman test, and partial correlation were used to analyze the data.

RESULTS

There was oxidative DNA damage increase in colorectal cancer evolution (p < 0.01). Histological grade was correlated with oxidative DNA damage (p < 0.01). There were differences in β-catenin expression among normal, adenoma, and adenocarcinoma tissue with progressive increase of β-catenin expression (p < 0.00). Histological grade was correlated to β-catenin expression (p < 0.00). There was a relationship (p < 0.00) between β-catenin and histological grade while controlling for the effect of oxidative DNA damage.

CONCLUSION

The findings of this study make it possible to establish a relationship between oxidative DNA damage and β-catenin expression in normal mucosa and colorectal tumor tissue. Additionally, they show a causal relationship between variations of β-catenin in different tissues analyzed while controlling for the effect of oxidative DNA damage.

In-depth characterization of the secretome of colorectal cancer metastatic cells identifies key proteins in cell adhesion, migration, and invasion

Liver metastasis in colorectal cancer is the major cause of cancer-related deaths. To identify and characterize proteins associated with colon cancer metastasis, we have compared the conditioned serum-free medium of highly metastatic KM12SM colorectal cancer cells with the parental, poorly metastatic KM12C cells using quantitative stable isotope labeling by amino acids in cell culture (SILAC) analyses on a linear ion trap-Orbitrap Velos mass spectrometer. In total, 1337 proteins were simultaneously identified in SILAC forward and reverse experiments. For quantification, 1098 proteins were selected in both experiments, with 155 proteins showing >1.5-fold change. About 52% of these proteins were secreted directly or using alternative secretion pathways. GDF15, S100A8/A9, and SERPINI1 showed capacity to discriminate cancer serum samples from healthy controls using ELISAs. In silico analyses of deregulated proteins in the secretome of metastatic cells showed a major abundance of proteins involved in cell adhesion, migration, and invasion. To characterize the tumorigenic and metastatic properties of some top up- and down-regulated proteins, we used siRNA silencing and antibody blocking. Knockdown expression of NEO1, SERPINI1, and PODXL showed a significant effect on cellular adhesion. Silencing or blocking experiments with SOSTDC1, CTSS, EFNA3, CD137L/TNFSF9, ZG16B, and Midkine caused a significant decrease in migration and invasion of highly metastatic cells. In addition, silencing of SOSTDC1, EFNA3, and CD137L/TNFSF9 reduced liver colonization capacity of KM12SM cells. Finally, the panel of six proteins involved in invasion showed association with poor prognosis and overall survival after dataset analysis of gene alterations. In summary, we have defined a collection of proteins that are relevant for understanding the mechanisms underlying adhesion, migration, invasion, and metastasis in colorectal cancer.

Promoter methylation analysis of WNT/β-catenin signaling pathway regulators to detect adenocarcinoma or its precursor lesion of the cervix

OBJECTIVE

Cervical adenocarcinoma (AdCA) and adenocarcinoma in situ (ACIS) are frequently missed in cytology-based screening programs. Testing for high-risk human papillomavirus (hrHPV) improves their detection, but novel ACIS/AdCA specific biomarkers are needed to increase specificity for these lesions. Novel markers may be deduced from the WNT/β-catenin signaling pathway, which is aberrantly activated during cervical carcinogenesis.

METHODS

Promoter methylation of nine WNT-antagonists (APC, AXIN2, DKK3, SFRP2, SFRP4, SFRP5, SOX17, WIF1 and WNT5A) was evaluated by methylation-specific PCR (MSP) on a small series of cervical tissue specimens, including AdCA and SCC. To estimate the diagnostic potential of the genes most frequently methylated in AdCA an extended series of ACIS, AdCA, CIN3, SCC, and normal cervical tissue specimens (n=131) as well as 49 hrHPV-positive scrapings were analyzed by quantitative MSP (qMSP).

RESULTS

The frequency of DKK3 and SFRP2 methylation was significantly higher in AdCA compared to SCC, i.e. 82% vs. 18% (p<0.01) and 84% vs. 39% (p<0.01), respectively, while SOX17 methylation frequency was significantly higher in SCC than AdCA, i.e. 89% vs. 62% (p<0.05). Methylation of WIF1 was common in both AdCA (71%) and SCC (54%). Methylation frequencies ranged from 4% to 55% in precursor lesions and from 0% to 5% in normal biopsies. When tested on HPV-positive cervical scrapings, qMSP of the best ACIS/AdCA discriminator genes, i.e. DKK3 and SFRP2, detected all women with underlying ACIS/AdCA, compared to 3% of controls.

CONCLUSIONS

DKK3 and SFRP2 promoter methylation is highly indicative for the presence of ACIS/AdCA, thereby providing promising triage markers for HPV-positive women at risk of ACIS/AdCA.

Colorectal cancer epigenetics: complex simplicity

Colorectal cancer (CRC) has predominantly been considered a genetic disease, characterized by sequential accumulation of genetic alterations. Growing evidence indicates that epigenetic alterations add an additional layer of complexity to the pathogenesis of CRC, and characterize a subgroup of colorectal cancers with a distinct etiology and prognosis. Epigenetic dysregulation in colorectal cancer is organized at multiple levels, involving DNA methylation, histone modifications, nucleosomal occupancy and remodeling, chromatin looping, and noncoding RNAs. Interactions between these processes and complex associations with genetic alterations have recently been unraveled. It appears that CRC epigenetics will be the paradigm for multistep carcinogenesis, as CRC genetics has been for the past three decades. This review integrates recent data on epigenetic regulation of gene expression in CRC and describes how the understanding of these processes will alter the management of CRC.

Identification of serum biomarkers for colorectal cancer metastasis using a differential secretome approach

Lymph node metastasis is the major concern that causes death in colorectal cancers. However, biomarkers for cancer metastasis are still lacking. In this study, we applied an LC-MS/MS-based label-free quantitative proteomics approach to compare the differential secretome of a primary cell line SW480 and its lymph node metastatic cell line SW620 from the same colorectal cancer patient. We identified a total of 910 proteins from the conditioned media and 145 differential proteins between SW480 and SW620 (>1.5-fold change). The differential expression pattern of 6 candidate proteins was validated by Western blot analysis. Among them, trefoil factor 3 and growth/differentiation factor 15, two up-regulated proteins in SW620, were further analyzed in a large cohort of clinical tissue and serum samples. Sandwich ELISA assay showed that the serum levels of both proteins were significantly higher in lymph node metastatic colorectal cancers. Receiver operating characteristic curve analysis confirmed that serum trefoil factor 3 and growth/differentiation factor 15 could provide a discriminatory diagnostic test for predicting colorectal cancer metastasis. Immunohistochemical analysis also showed that the overexpression of trefoil factor 3 or growth/differentiation factor 15 in colorectal cancer was associated with lymph node metastatic behavior. This study showed an accurate, sensitive, and robust label-free quantitation approach for differential analysis of cancer secretome. The comparison of the cancer secretome in vitro is a feasible strategy to obtain valuable biomarkers for potential clinical application. Both trefoil factor 3 and growth/differentiation factor 15 could serve as potential biomarkers for the prediction of colorectal cancer metastasis.

The effects of epidermal growth factor receptor activation and attenuation of the TGFbeta pathway in an orthotopic model of colon cancer

BACKGROUND

Colorectal cancer is the second leading cause of cancer related mortality, with a majority of deaths resulting from metastases. Few in vivo models allow for the study of the complex process of metastasis. The purpose of this study was to determine the effects of epidermal growth factor receptor activation and TGFbeta pathway attenuation in FET, a weakly tumorigenic human colon cancer cell line, in an orthotopic model.

METHODS AND RESULTS

Using FET, FETalpha, FETalphaDNRII, and FETDNRII cells were constructed. Tumors were orthotopically implanted onto the colons of BALB/c nude mice. After 7 wk, the mice were euthanized and organs extracted for examination. All cell lines demonstrated primary invasion. FETalpha was weakly metastatic compared with FETalphaDNRII and FETDNRII, which demonstrated metastases to the lung and liver, respectively.

CONCLUSION

Epidermal growth factor receptor (EGFR) activation transforms a nontumorigenic cell line into a tumorigenic but not metastatic one. The tumorigenic line becomes metastatic with the attenuation of TGFbeta signaling. Loss of EGFR activation in the TGFbeta inhibited line results in a decreased metastatic burden, but importantly, changes the organotropic homing from lung to liver. Thus, these in vivo studies demonstrate that EGFR activation and TGFbeta signaling pathways play a role in tumorigenicity and in pattern of metastases.