Cytokeratin 20 and guanylyl cyclase C mRNA is largely present in lymph node and liver specimens of colorectal cancer patients

Prognostic Value of Molecular Detection of Lymph Node Metastases After Curative Resection of Stage II Colon Cancer: A Systematic Pooled Data Analysis

BACKGROUND

We aimed to clarify the prognostic value of guanylyl cyclase C (GCC) lymph node ratio (LNR) status as a predictor of recurrence in untreated stage IIA colon cancer on the basis of pooled individual data from previous studies.

METHODS

Patients were classified according to predefined GCC LNR risk groups (low, LNR ≤ 0.1; intermediate, 0.1 < LNR ≤ 0.2; high, LNR > 0.2). Outcomes included time to recurrence, disease-free survival, and overall survival. Stratified log-rank tests and multivariate Cox models assessed the association between outcomes and GCC lymph node status.

RESULTS

The final data set contained 553 patients with stage IIA colon cancer with a median of 18 lymph nodes examined after resection; 65 patients (11.8%) had recurrence. Overall, 109 patients (19.7%) were classified high risk on the basis of GCC LNR. In multivariate analysis, high GCC LNR value (> 0.2) was a significant predictor of cancer recurrence (hazard ratio [HR], 3.18; 95% confidence interval [CI], 1.77-5.71; P < .001) and lower disease-free survival (HR, 2.40; 95% CI, 1.60-3.62; P < .001) and overall survival (HR, 2.12; 95% CI, 1.35-3.33; P = .001).

CONCLUSION

Patients considered at high risk on the basis of their GCC LNR status have significantly inferior outcomes compared to those with low GCC LNR values, particularly among those traditionally considered to be at low risk for recurrence.

Molecular biomarkers for the detection of metastatic colorectal cancer cells

Approximately half of all patients with colorectal cancer develop local recurrence or distant metastasis during the course of their illness. Recently, the molecular detection of metastatic cancer cells in various types of clinical samples, such as lymph nodes, bone marrow, peripheral blood, and peritoneal lavage fluid, has been investigated as a potential prognostic marker. The prognostic value of molecular tumor cell detection was independent of the type of detection method used. As assays become more sensitive and quantitative, a more thorough assessment of the cancer status of patients will be based on molecular markers alone. At present, it is difficult to conclude that one specific molecular marker is superior to others. Comparative analyses are recommended to assess the prognostic impact of molecular analyses in the same patient and determine the biomarkers that provide the most accurate prognostic information.

WITHDRAWN: Expression and functional characterization of guanylyl cyclase C receptor in HepG2 cells: Two-step regulation by dexamethasone and hepatocyte nuclear factor 4 (HNF4)

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Biology and significance of circulating and disseminated tumour cells in colorectal cancer

PURPOSE

More than 130 years ago, circulating tumour cells (CTCs) and disseminated tumour cells (DTCs) have been linked to metastasis. Since then, a myriad of studies attempted to characterise and elucidate the clinical impact of CTCs/DTCs, amongst others in colorectal cancer (CRC). Due to a flood of heterogeneous findings regarding CTCs/DTCs in CRC, this review aims to describe the known facts about CTC/DTC biology and clinical impact.

METHODS

To identify the basic scientific literature regarding the biology and clinical impact of CTCs/DTCs in CRC, we reviewed the literature in the PubMed database. We focused on publications written in English and published until January 2012. As search terms, we used "colorectal cancer (CRC)", "colon cancer (CC)", "CTC", "DTC", "bone marrow (BM)", "lymph node (LN)", "peripheral blood (PB)", "significance" and "prognosis".

RESULTS

CTC detection and quantification under standardised conditions is feasible. Several studies in large patient settings have revealed prognostic impact of CTCs in CRC. CRC-derived DTC detection and analysis in BM exhibits a more heterogeneous picture but also shows clinical value. Furthermore, the presence of DTCs in LN has a strong prognostic impact in CRC.

CONCLUSIONS

Clinical relevance and prognostic significance of CTCs/DTCs in CRC have been clearly demonstrated in many experimental studies. The major challenge in CTC/DTC research is now to harmonise the various identification and detection approaches and consequently to conduct large prospective multi-institutional trials to verify the use of CTCs/DTCs as a valid prognostic and predictive biomarker for clinical routine.

Epitope-targeted cytotoxic T cells mediate lineage-specific antitumor efficacy induced by the cancer mucosa antigen GUCY2C

Guanylyl cyclase C (GUCY2C) is the index cancer mucosa antigen, an emerging class of immunotherapeutic targets for the prevention of recurrent metastases originating in visceral epithelia. GUCY2C is an autoantigen principally expressed by intestinal epithelium, and universally by primary and metastatic colorectal tumors. Immunization with adenovirus expressing the structurally unique GUCY2C extracellular domain (GUCY2C(ECD); Ad5-GUCY2C) produces prophylactic and therapeutic protection against GUCY2C-expressing colon cancer metastases in mice, without collateral autoimmunity. GUCY2C antitumor efficacy is mediated by a unique immunological mechanism involving lineage-specific induction of antigen-targeted CD8(+) T cells, without CD4(+) T cells or B cells. Here, the unusual lineage specificity of this response was explored by integrating high-throughput peptide screening and bioinformatics, revealing the role for GUCY2C-directed CD8(+) T cells targeting specific epitopes in antitumor efficacy. In BALB/c mice vaccinated with Ad5-GUCY2C, CD8(+) T cells recognize the dominant GUCY2C(254-262) epitope in the context of H-2K(d), driving critical effector functions including interferon gamma secretion, cytolysis ex vivo and in vivo, and antitumor efficacy. The ability of GUCY2C to induce lineage-specific responses targeted to cytotoxic CD8(+) T cells recognizing a single epitope mediating antitumor efficacy without autoimmunity highlights the immediate translational potential of cancer mucosa antigen-based vaccines for preventing metastases of mucosa-derived cancers.

Expression of chemokine receptor CCR5 correlates with the presence of hepatic molecular metastases in K-ras positive human colorectal cancer

BACKGROUND

Molecular metastases are precursors of postoperative recurrence, detected by molecular-biological tools. Chemokines and their receptors contribute to dissemination and local immune recognition. A strong expression of the chemokine receptor CCR5 is associated with non-metastatic colorectal cancer and increased CD8+ T-cell infiltration. The aim of this study was to analyze whether CCR5 expression correlates with the presence of hepatic molecular metastases (MM).

METHODS

Ninety-three patients undergoing elective surgery for colorectal cancer were assessed. The K-ras mutation status was defined by PCR-RFLP, and the CCR5 expression status was analyzed by CCR5-specific reverse transcription (RT-PCR) analysis. Liver biopsy samples had been intra-operatively taken to screen for MM. MM were detected by K-ras-specific PCR-RFLP and nested CK20/GCC RT-PCR. Prevalence of MM was correlated with CCR5 expression status.

RESULTS

Human colorectal cancer harboured K-ras mutations in 53% (codon 12: 47%; codon 13: 6%) of cases. Among K-ras mutants, MM were detected in 27-53% of patients, dependent on the technique applied (K-ras-specific PCR-RFLP assay vs. nested CK20/GCC RT-PCR approach (P = 0.004)). CCR5 expression of K-ras mutants ranged from absent (23/49: 47%), weak (17/49: 35%), intermediate (4/49: 8%) to strong (5/49: 10%). MM were found in 30% of CCR5 negative and in 23% of CCR5 positive cancer patients by the K-ras-specific PCR-RFLP assay. The nested CK20/GCC RT-PCR assay detected MM in 87% of CCR5 negative and in 27% of CCR5 positive colorectal cancer patients (P = 0.00002).

CONCLUSION

Thus, CCR5 expression of the primary cancer might be a valuable biomarker indicating the absence of hepatic molecular metastases.

The potential of cytokeratin 20 and mucin 2 mRNA as metastasis markers in regional lymph nodes of colon cancer patients investigated by quantitative RT-PCR

PURPOSE

The presence of regional lymph node metastases is one of the most important prognostic factors in colon cancer. Nevertheless, up to 30% of the lymph node negative patients experience disease recurrence. Possibly, this patient group may be identified by more sensitive techniques than routine histopathological examination of the lymph nodes.

METHODS

In the present study, we have evaluated the detection of colon cancer lymph node metastases by real-time RT-PCR quantitation of the epithelial-specific cytokeratin 20 (CK20) and mucin 2 (MUC2) mRNAs.

RESULTS

Both assays were able to detect dilutions of tumor cells down to one tumor cell in 10(6) normal lymphocytes. CK20 and MUC2 mRNA were quantitated in 52 normal lymph nodes from 12 patients undergoing surgery for benign bowel diseases and in 144 primary colon tumors. The median tumor level of both markers were more than 10(4)-fold higher than the highest level in normal lymph nodes, indicating that the markers had a potential for metastasis detection in a clinical context. We applied the assays to 61 lymph nodes with known metastases detected by routine staining. Elevated CK20 or MUC2 mRNA levels were detected in 57 (95%) of the 61 LNs.

CONCLUSIONS

Thus, CK20 and MUC2 quantitation by real-time RT-PCR seems to be a promising, sensitive tool to detect metastases in regional lymph nodes from colon cancer patients.

Review: Biological relevance of disseminated tumor cells in cancer patients

The prognosis of cancer patients is largely determined by the occurrence of distant metastases. In patients with primary tumors, this relapse is mainly due to clinically occult micrometastasis present in secondary organs at primary diagnosis but not detectable even with high resolution imaging procedures. Sensitive and specific immunocytochemical and molecular assays enable the detection and characterization of disseminated tumor cells (DTC) at the single cell level in bone marrow (BM) as the common homing site of DTC and circulating tumor cells (CTC) in peripheral blood. Because of the high variability of results in DTC and CTC detection, there is an urgent need for standardized methods. In this review, we will focus on BM and present currently available methods for the detection and characterization of DTC. Furthermore, we will discuss data on the biology of DTC and the clinical relevance of DTC detection. While the prognostic impact of DTC in BM has clearly been shown for primary breast cancer patients, less is known about the clinical relevance of DTC in patients with other carcinomas. Current findings suggest that DTC are capable to survive chemotherapy and persist in a dormant nonproliferating state over years. To what extent these DTC have stem cell properties is subject of ongoing investigations. Further characterization is required to understand the biology of DTC and to identify new targets for improved risk prevention and tailoring of therapy. Our review will focus on breast, colon, lung, and prostate cancer as the main tumor entities in Europe and the United States.

Detection of disseminated tumor cells in liver biopsies of colorectal cancer patients is not associated with a worse prognosis

BACKGROUND

Liver metastases occur frequently in colorectal cancer and are probably caused by disseminated tumor cells having been trapped in the liver. The prognostic significance of hematogenous tumor cell dissemination has already been demonstrated for blood and bone marrow of patients with colorectal cancer. The aim of this study was to investigate the frequency and prognostic significance of disseminated tumor cells in liver biopsies of colorectal cancer patients.

METHODS

Liver biopsies from 100 patients with UICC stage I-III colorectal cancer were taken prospectively during resection of the primary tumor. Liver biopsies obtained from 16 patients with benign gastrointestinal diseases served as negative controls. Liver samples from seven patients with liver cirrhosis were additionally taken. Liver biopsies were examined using a reverse transcriptase (RT)-PCR assay to amplify cytokeratin (CK) 20 transcripts. The median follow-up of the patients was 55 months.

RESULTS

Disseminated tumor cells were detected in liver samples of 10/100 (10%) patients with UICC stage I-III colorectal cancer. Liver specimens from all seven patients with liver cirrhosis were CK 20-positive, whereas 16 patients with other benign gastrointestinal diseases were all CK 20-negative. There was no correlation between tumor cell detection in liver biopsies and survival of the patients. The only significant prognostic factor on uni- and multivariate analysis was the UICC stage.

CONCLUSIONS

This study demonstrates that detection of disseminated tumor cells in liver samples from patients with UICC stage I-III colorectal cancer has no prognostic influence. UICC classification was the strongest prognostic factor in this patient series.

Guanylyl cyclase C: a molecular marker for staging and postoperative surveillance of patients with colorectal cancer

Staging patients with colorectal cancer defines their prognosis and therapeutic management. Unfortunately, histopathology, the current standard for staging, is relatively insensitive for detecting occult micrometastases and a significant fraction of patients are understaged and, consequently, undertreated. Similarly, current approaches to postoperative surveillance of patients with colorectal cancer detect disease recurrence at a point when interventions have little impact on survival. The detection of rare cells in tissue, for accurately staging patients, and in blood, for detecting disease recurrence, could be facilitated by employing sensitive and specific markers of disease. Guanylyl cyclase C (GCC), the receptor for the diarrheagenic bacterial heat-stable enterotoxin, is expressed selectively by cells derived from intestinal mucosa, including normal intestinal cells and colorectal tumor cells, but not by extragastrointestinal tissues and tumors. The nearly uniform expression of relatively high levels by metastatic colorectal tumors suggests that GCC may be a sensitive and specific molecular marker for metastatic colorectal cancer cells. Employing GCC reverse transcriptase PCR, occult colorectal cancer micrometastases were detected in lymph nodes that escaped detection by histopathology. Moreover, marker expression correlated with the risk of disease recurrence. Similarly, GCC reverse transcriptase PCR revealed the presence of tumor cells in blood of all patients examined with metastatic colorectal cancer and, in some studies, was associated with an increased risk of disease recurrence and mortality. These observations suggest that GCC reverse transcriptase PCR is a sensitive and specific technique for identifying tumor cells in extraintestinal sites and may be useful for staging and postoperative surveillance of patients with colorectal cancer.

Real-time reverse transcription PCR and the detection of occult disease in colorectal cancer

Molecular diagnostics offers the promise of accurately matching patient with treatment, and a resultant significant effect on improved disease outcome. More specifically, the real-time reverse transcription polymerase chain reaction (qRT-PCR), with its combination of conceptual simplicity and technical utility, has the potential to become a valuable analytical tool for the detection of mRNA targets from tissue biopsies and body fluids. Its potential is particularly promising in cancer patients, both as a prognostic assay and for monitoring response to therapy. Colorectal cancer provides an instructive paradigm for this potential as well as the problems associated with its use as a clinical assay. Currently, histopathological staging, which provides a static description of the anatomical extent of tumour spread within a surgical specimen, defines patient prognosis. The detection of lymph node (LN) metastasis constitutes the most important prognostic factor in colorectal cancer and as the primary indicator of systemic disease spread, LN status determines the choice of postoperative adjuvant chemotherapy. However, its limitations are emphasised by the considerable prognostic heterogeneity of patients within a given tumour stage: not all patients with LN-negative cancers are cured and not all patients with LN-positive tumours die from their disease. This has resulted in a search for more accurate staging protocols and has seen the introduction of the concept of "molecular staging", the incorporation of molecular parameters into clinical tumour staging. Quantification of disease-associated mRNA is one such parameter that utilises the qRT-PCR assay's potential for generating quantitative results. These are not only more informative than qualitative data, but contribute to assay standardisation and quality management. This review provides an assessment of the practical value to the clinician of RT-PCR-based molecular diagnostics. It points out reasons for the many contradictory results encountered in the literature and concludes that there is an urgent need for standardisation at every level, starting with pre-assay sample acquisition and template preparation, assay protocols and post-assay analysis.

Detection of disseminated tumour cells in the liver of cancer patients

AIMS

The liver is a common site of metastasis from a variety of solid malignancies. This is due to disseminated tumour cells (DTC) that have spread prior to or during surgery from the primary carcinoma. This article gives a short overview of the data published on the detection of DTC in the liver and describes the commonly used detection methods and respective markers.

METHODS

A literature survey was performed in public medical databases comprising the last 15 years with focus on DTC detection in liver tissue of cancer patients.

KEY FINDINGS

Although the liver is a preferred site of metastasis, only a few studies have analysed the DTC incidence in inconspicuous liver tissue. The available reports include only patients with pancreatic and colorectal carcinomas. In patients with pancreatic cancer the DTC incidence varied from 5 to 76%. No follow-up data has been reported so far. In patients with colorectal carcinoma hepatic DTC were found in 5-69% of cases. A negative prognostic influence of hepatic DTC was reported in all but one studies with follow-up information.

CONCLUSIONS

The detection of DTC in the liver can contribute to identify patients with increased risk who could benefit from an intensified follow-up or new treatment strategies.

Detection of disseminated tumour cells in the liver of colorectal cancer patients

AIMS

The aim of this study was to assess the incidence and lobar distribution of three surrogate tumour cell markers in biopsies from both liver lobes.

PATIENTS AND METHODS

This study comprised 189 patients for whom DNA and/or RNA was available from both liver lobes and who showed at least one positive marker in one liver lobe. Detection of cytokeratin 20 (CK20) and guanylylcyclase C (GCC) was performed by nested reverse transcription-PCR. For detection of K-ras mutations in codons 12 and 13, a PCR-restriction-fragment-length-polymorphism assay was used.

RESULTS

The incidence of all markers and their combinations was higher in the smaller left lobe than in the larger right lobe (CK20: 62 vs 38%; GCC: 52 vs 48%; K-ras: 61 vs 39%; CK20+GCC: 61 vs 39%; CK20+GCC and/or K-ras: 61 vs 39%). The marker incidence in the two liver lobes was independent from the location of the respective primary colorectal carcinoma.

CONCLUSIONS

The markers CK20, GCC, and K-ras indicating cells shed from the primary CRC were detected more often individually and in combination in biopsies from the smaller left lobe than from the larger right lobe. The site of the primary tumour did not influence the marker incidence in both liver lobes.

Molecular detection of clinical colorectal cancer metastasis: how should multiple markers be put to use?

BACKGROUND AND AIMS

Up to 45% of colorectal cancer (CRC) patients will develop local recurrence or metastasis following curative resection. The latter is due to cells shed from the primary carcinoma prior to or during surgery. The aim of this study was to contribute toward a "rational"-approach for detecting these disseminated tumor cells (DTC) using a combination of independent markers and detection methods.

PATIENTS/METHODS

Liver, lymph node, and bone marrow samples from 246 CRC patients were screened for DTC using three markers: mutated K-ras was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and cytokeratin 20 (CK20) and guanylylcyclase C (GCC), indicating circulating epithelial cells, were tracked by nested reverse-transcription (RT) PCR.

RESULTS

The rate of positive findings of the individual markers (CK20: 88%; GCC: 88%; K-ras: 67%) and their combinations (88-50%) was significantly higher in biopsies from liver metastases than in liver samples from patients without evident distant metastasis (M0; p<0.03). The detection rate of individual markers (except GCC) was also significantly elevated in inconspicuous liver tissue adjacent to metastasis compared with specimens from M0 patients. When using the concomitant detection of all three markers as criterion for DTC in the liver of M0 patients, however, no patient was DTC-positive. Therefore, the concomitant presence of the two CEC markers (CK20 plus GCC) and/or the presence of mutated K-ras were preferred for a combined evaluation, which resulted in a 24% detection rate for biopsies from both liver lobes. This translates into 39% of M0 patients with at least one positive liver biopsy.

CONCLUSION

Our results suggest that the concomitant detection of CK20 plus GCC and/or the presence of mutated K-ras are a rational approach for tracking CEC/DTC in CRC patients.

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