Genetic disparity between primary tumours, disseminated tumour cells, and manifest metastasis

Recent genetic analyses of paired samples from primary tumours and disseminated tumour cells have uncovered a bewildering genetic disparity. It was therefore proposed that ectopically residing tumour cells disseminate early and develop independently into metastases parallel to the primary tumour. Alternatively, these cells may represent an irrelevant cell population unable to spawn metastases whereas only cells that disseminated late in primary tumour development (which therefore are similar to the primary tumour) will form manifest metastasis. Here, we review comparative analyses of paired samples from primary tumours and disseminated tumour cells or primary tumours and metastases. The data demonstrate a striking disparity, questioning the use of primary tumours as surrogate for the genetics of systemic cancer. In the era of molecular therapies that build upon genetic defects of tumour cells, these data call for a direct diagnostic pathology of systemic cancer.

Lessons from an aggressive cancer: evolutionary dynamics in esophageal carcinoma

Rapid progression to metastatic disease and an intrinsic resistance to any type of systemic therapy are hallmarks of aggressive solid cancers. The molecular basis for this phenotype is not clear. A detailed study of the somatic progression from local to early systemic esophageal cancer revealed rapid diversification of cancer cells isolated from various sites, but also evidence for early clonal expansion. These findings have implications for diagnostic pathology and therapeutic decision making.

The hematopoietic stem cell in chronic phase CML is characterized by a transcriptional profile resembling normal myeloid progenitor cells and reflecting loss of quiescence

We found that composition of cell subsets within the CD34+ cell population is markedly altered in chronic phase (CP) chronic myeloid leukemia (CML). Specifically, proportions and absolute cell counts of common myeloid progenitors (CMP) and megakaryocyte-erythrocyte progenitors (MEP) are significantly greater in comparison to normal bone marrow whereas absolute numbers of hematopoietic stem cells (HSC) are equal. To understand the basis for this, we performed gene expression profiling (Affymetrix HU-133A 2.0) of the distinct CD34+ cell subsets from six patients with CP CML and five healthy donors. Euclidean distance analysis revealed a remarkable transcriptional similarity between the CML patients' HSC and normal progenitors, especially CMP. CP CML HSC were transcriptionally more similar to their progeny than normal HSC to theirs, suggesting a more mature phenotype. Hence, the greatest differences between CP CML patients and normal donors were apparent in HSC including downregulation of genes encoding adhesion molecules, transcription factors, regulators of stem-cell fate and inhibitors of cell proliferation in CP CML. Impaired adhesive and migratory capacities were functionally corroborated by fibronectin detachment analysis and transwell assays, respectively. Based on our findings we propose a loss of quiescence of the CML HSC on detachment from the niche leading to expansion of myeloid progenitors.

Direct genetic analysis of single disseminated cancer cells for prediction of outcome and therapy selection in esophageal cancer

The increasing use of primary tumors as surrogate markers for prognosis and therapeutic decisions neglects evolutionary aspects of cancer progression. To address this problem, we studied the precursor cells of metastases directly for the identification of prognostic and therapeutic markers and prospectively analyzed single disseminated cancer cells from lymph nodes and bone marrow of 107 consecutive esophageal cancer patients. Whole-genome screening revealed that primary tumors and lymphatically and hematogenously disseminated cancer cells diverged for most genetic aberrations. However, we identified chromosome 17q12-21, the region comprising HER2, as the most frequent gain in disseminated tumor cells that were isolated from both ectopic sites. Survival analysis demonstrated that HER2 gain in a single disseminated tumor cell but not in primary tumors conferred high risk for early death.

High-resolution array comparative genomic hybridization of single micrometastatic tumor cells

Only few selected cancer cells drive tumor progression and are responsible for therapy resistance. Their specific genomic characteristics, however, are largely unknown because high-resolution genome analysis is currently limited to DNA pooled from many cells. Here, we describe a protocol for array comparative genomic hybridization (array CGH), which enables the detection of DNA copy number changes in single cells. Combining a PCR-based whole genome amplification method with arrays of highly purified BAC clones we could accurately determine known chromosomal changes such as trisomy 21 in single leukocytes as well as complex genomic imbalances of single cell line cells. In single T47D cells aberrant regions as small as 1-2 Mb were identified in most cases when compared to non-amplified DNA from 10(6) cells. Most importantly, in single micrometastatic cancer cells isolated from bone marrow of breast cancer patients, we retrieved and confirmed amplifications as small as 4.4 and 5 Mb. Thus, high-resolution genome analysis of single metastatic precursor cells is now possible and may be used for the identification of novel therapy target genes.

Occult tumor cells in lymph nodes as a predictor for tumor relapse in pancreatic adenocarcinoma

BACKGROUND AND AIMS

Occurrence of tumor relapse is frequent in patients with pancreatic cancer despite the absence of residual tumor detectable at primary surgery and in histopathological examination. Therefore, it has to be assumed that current tumor staging procedures fail to identify minimal amounts of disseminated tumor cells, which might be precursors of subsequent metastatic relapse. The aim of this study was to assess the prognostic impact of minimal tumor cell spread detected in lymph nodes classified as "tumor-free" in routine histopathologic evaluation.

MATERIALS AND METHODS

A total of 154 "tumor-free" lymph nodes from 59 patients with pancreatic cancer who underwent intentionally curative tumor resection were examined by immunohistochemistry for disseminated tumor cells.

RESULTS

Fifty (32.5%) of the "tumor-free" lymph nodes obtained from 36 (61%) patients displayed disseminated tumor cells. Multivariate survival analysis revealed that the presence of disseminated tumor cells in "tumor-free" lymph nodes is an independent prognostic factor for both a significantly reduced relapse-free survival (p = 0.03) and overall survival (p = 0.02).

CONCLUSIONS

The frequent occurrence and prognostic impact of immunohistochemically identifiable disseminated tumor cells in lymph nodes of patients with operable pancreatic cancer supports the need for a refined staging system of excised lymph nodes, which should include immunohistochemical examination.

Sentinel lymph node biopsy in colon cancer: a prospective multicenter trial

INTRODUCTION

The clinical impact of sentinel lymph node biopsy (SLNB) in colon cancer is still controversial. The purpose of this prospective multicenter trial was to evaluate its clinical value to predict the nodal status and identify factors that influence these results.

METHODS

Colon cancer patients without prior colorectal surgery or irradiation were eligible. The sentinel lymph node (SLN) was identified intraoperatively by subserosal blue dye injection around the tumor. The SLN underwent step sections and immunohistochemistry (IHC), if classified free of metastases after routine hematoxylin and eosin examination.

RESULTS

At least one SLN (median, n = 2) was identified in 268 of 315 enrolled patients (detection rate, 85%). Center experience, lymphovascular invasion, body mass index (BMI), and learning curve were positively associated with the detection rate. The false-negative rate to identify pN+ patients by SLNB was 46% (38 of 82). BMI showed a significant association to the false-negative rate (P < 0.0001), the number of tumor-involved lymph nodes was inversely associated. If only slim patients (BMI < or =24) were investigated in experienced centers (>22 patients enrolled), the sensitivity increased to 88% (14 of 16). Moreover, 21% (30 of 141) of the patients, classified as pN0 by routine histopathology, revealed micrometastases or isolated tumor cells (MM/ITC) in the SLN.

CONCLUSIONS

The contribution of SLNB to conventional nodal staging of colon cancer patients is still unspecified. Technical problems have to be resolved before a definite conclusion can be drawn in this regard. However, SLNB identifies about one fourth of stage II patients to reveal MM/ITC in lymph nodes. Further studies must clarify the clinical impact of these findings in terms of prognosis and the indication of adjuvant therapy.

Benefit of Surgical Treatment of Lung Metastasis in Soft Tissue Sarcoma

HYPOTHESIS

Patients with pulmonary metastatic soft tissue sarcoma benefit from resection, with long-term cure possible.

DESIGN

Retrospective medical records review.

SETTING

Academic tertiary care center.

PATIENTS

Between January 1, 1991, and December 31, 2002, 61 patients (33 men and 28 women; median age at initial diagnosis, 42 years [age range, 18-74 years]) were surgically treated for pulmonary metastases of soft tissue sarcoma at University Hospital, Hamburg-Eppendorf, Germany.

INTERVENTIONS

Sternotomy or anterior lateral thoracotomy was performed for metastasectomy, including wedge resection or lobectomy.

MAIN OUTCOME MEASURE

The effects of clinical and pathologic factors on disease-specific survival were analyzed using the log rank test and a multivariate Cox proportional hazards model.

RESULTS

Primary tumor size was pT1 in 13 patients and pT2 in 48 patients. The differentiation was high in 7 patients, intermediate in 19 patients, and low in 35 patients. The mean number of resected pulmonary metastatic lesions was 5 (range, 1-48). An anterolateral thoracotomy was performed in 39 patients, and sternotomy in 22 patients. There were no significant postoperative complications that required surgical revision. The perioperative mortality was 0%. At a mean follow-up of 60 months, the mean survival time after metastasectomy was 33 months (range, 2-125 months). The 5-year survival was 25%. The number of resected lung metastatic lesions had no prognostic relevance (P = .37).

CONCLUSIONS

Patients with lung metastasis from soft tissue sarcomas benefit from surgical excision. This treatment has low complication rates and has a favorable influence on the course of the disease. Long-term survival is possible even when recurrent pulmonary disease is resected.

Ep-CAM expression in squamous cell carcinoma of the esophagus: a potential therapeutic target and prognostic marker

BACKGROUND

To evaluate the expression and test the clinical significance of the epithelial cellular adhesion molecule (Ep-CAM) in esophageal squamous cell carcinoma (SCC) to check the suitability of esophageal SCC patients for Ep-CAM directed targeted therapies.

METHODS

The Ep-CAM expression was immunohistochemically investigated in 70 primary esophageal SCCs using the monoclonal antibody Ber-EP4. For the interpretation of the staining results, we used a standardized scoring system ranging from 0 to 3+. The survival analysis was calculated from 53 patients without distant metastasis, with R0 resection and at least 2 months of clinical follow-up.

RESULTS

Ep-CAM neo-expression was observed in 79% of the tumors with three expression levels, 1+ (26%), 2+ (11%) and 3+ (41%). Heterogeneous expression was observed at all expression levels. Interestingly, tumors with 3+ Ep-CAM expression conferred a significantly decreased median relapse-free survival period (log rank, p = 0.0001) and median overall survival (log rank, p = 0.0003). Multivariate survival analysis disclosed Ep-CAM 3+ expression as independent prognostic factor.

CONCLUSION

Our results suggest Ep-CAM as an attractive molecule for targeted therapy in esophageal SCC. Considering the discontenting results of the current adjuvant concepts for esophageal SCC patients, Ep-CAM might provide a promising target for an adjuvant immunotherapeutic intervention.

Copy number of chromosome 17 but not HER2 amplification predicts clinical outcome of patients with pancreatic ductal adenocarcinoma

PURPOSE

To determine the frequency and the potential clinical use of HER2 (17q21) gene amplification and chromosome 17 aneuploidy in pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

Serial tissue sections of 50 resected PDACs were analyzed with chromogenic in situ hybridization using locus-specific HER2 probes and centromeric probes for chromosome 17. Centromeric probes for chromosome 7 and 8 were hybridized to confirm ploidy levels. Expression of HER2 protein was assessed by immunohistochemistry. Correlations of experimental findings with clinical and follow-up data were tested.

RESULTS

The HER2 gene locus was frequently (24%) amplified in PDAC and the rate of overexpression (2+ and 3+) was 10%, but no prognostic significance was found. Copy number analysis of chromosomes 7, 8, and 17 revealed disomic (40%), trisomic (36%), and hypertetrasomic (24%) tumors. Compared with patients with disomic tumors, patients with hypertetrasomic tumors exhibited a significantly decreased relapse-free and overall survival (5.0 v 13.0 months, P = .0144 and 7.0 v 20.0 months, P = .0099, respectively). Multivariate analysis confirmed the independent prognostic significance of hypertetrasomy.

CONCLUSION

Tumor ploidy levels correlate with prognosis of PDAC patients, indicating characteristic biologic properties of PDAC with high chromosomal instability. In contrast, no prognostic influence on patient outcome was found for the amplification of the HER2 oncogene or p185(HER2) overexpression. Therefore, evaluation of ploidy levels offers new opportunities for patient stratification in clinical trials and enables novel approaches to study the well-known aggressiveness of PDAC.

Squamous cell carcinoma of the esophagus can be detected by microsatellite analysis in tumor and serum

PURPOSE

Esophageal squamous cell cancer can be treated effectively by potentially curative surgery if diagnosed at an early stage. Our aim was to develop a novel molecular approach as a noninvasive test for squamous cell cancer detection and as an indicator for the prognosis of the patients.

EXPERIMENTAL DESIGN

Matched normal, tumor, and serum samples were obtained from 28 patients with squamous cell carcinoma (SCC) of the esophagus. DNA was extracted, and the samples were subjected to microsatellite analysis using 12 markers. Serum and normal DNA from 10 healthy individuals served as controls.

RESULTS

Twenty-six of the 28 patients (92.9%) with SCC were found to have one or more microsatellite DNA alterations in their primary tumor. Twenty-seven of the 28 patients (96.4%) had at least one alteration in the serum by microsatellite analysis. Mean age was 61.5 years. Microsatellite alterations were not identified in the serum DNA of samples from normal control subjects. Median follow-up was 13 months. Survival and recurrence were not significantly correlated with either loss of heterozygosity in the tumor or in the serum.

CONCLUSIONS

Microsatellite DNA analysis of tumor and serum specimen is a potentially valuable tool for detection and for the evaluation of the prognosis of SCC of the esophagus. The follow-up in our study is still too short to draw final conclusions on the correlation of disease-specific survival and disease recurrence with microsatellite alterations. The evidence of circulating tumor DNA in almost all of our patients underlines a systemic component of the disease that is not surgically amenable.

Molecular markers and staging of early esophageal cancer

BACKGROUND

Patients with early esophageal cancer experience varying clinical outcomes despite identical tumor staging by standard diagnostic methods because clinical and histopathological staging fail to reveal the underlying complex biology of cancer.

METHODS AND FOCUS

This review discusses some of the current concepts of molecular staging with the potential to enhance the current staging methods of patients with early esophageal cancer.

CONCLUSIONS

Understanding the molecular biology of esophageal cancer has increased substantially, and clinicians anticipate the translation of the gained knowledge into patient care. Numerous molecular techniques are potentially available for analyzing biological aspects of the individual tumor for improved staging.

Genetic heterogeneity of single disseminated tumour cells in minimal residual cancer

BACKGROUND

Because cancer patients with small tumours often relapse despite local and systemic treatment, we investigated the genetic variation of the precursors of distant metastasis at the stage of minimal residual disease. Disseminated tumour cells can be detected by epithelial markers in mesenchymal tissues and represent targets for adjuvant therapies.

METHODS

We screened 525 bone-marrow, blood, and lymph-node samples from 474 patients with breast, prostate, and gastrointestinal cancers for single disseminated cancer cells by immunocytochemistry with epithelial-specific markers. 71 (14%) of the samples contained two or more tumour cells whose genomic organisation we studied by single cell genomic hybridisation. In addition, we tested whether TP53 was mutated. Hierarchical clustering algorithms were used to determine the degree of clonal relatedness of sister cells that were isolated from individual patients.

FINDINGS

Irrespective of cancer type, we saw an unexpectedly high genetic divergence in minimal residual cancer, particularly at the level of chromosomal imbalances. Although few disseminated cells harboured TP53 mutations at this stage of disease, we also saw microheterogeneity of the TP53 genotype. The genetic heterogeneity was strikingly reduced with the emergence of clinically evident metastasis.

INTERPRETATION

Although the heterogeneity of primary tumours has long been known, we show here that early disseminated cancer cells are genomically very unstable as well. Selection of clonally expanding cells leading to metastasis seems to occur after dissemination has taken place. Therefore, adjuvant therapies are confronted with an extremely large reservoir of variant cells from which resistant tumour cells can be selected.

SCOMP is superior to degenerated oligonucleotide primed-polymerase chain reaction for global amplification of minute amounts of DNA from microdissected archival tissue samples

Global genome amplification from formalin-fixed tissues is still problematic when performed with low cell numbers. Here, we tested a recently developed method for whole genome amplification termed "SCOMP" (single cell comparative genomic hybridization) on archival tissues of different ages. We show that the method is very well suited for formalin-fixed paraffin-embedded samples obtained by nuclei extraction or laser microdissection. The polymerase chain reaction (PCR) products can be used for subsequent comparative genomic hybridization, loss of heterozygosity studies, and DNA sequencing. To control for PCR-induced artifacts we amplified genomic DNA isolated from 20 nuclei of archival formalin-fixed, paraffin-embedded nonpathological lymph nodes. Subsequent comparative genomic hybridization revealed the expected balanced profiles. For loss of heterozygosity analysis by microsatellite PCR 60 to 160 cells were sufficient. In comparative experiments the approach turned out to be superior to published degenerated oligonucleotide-primed-PCR protocols. The method provides a robust and valuable tool to study very small cell samples, such as the genomes of dysplastic cells or the clonal evolution within heterogeneous tumors.

Expression of 17-1A antigen and complement resistance factors CD55 and CD59 on liver metastasis in colorectal cancer

Despite radical surgery, the prognosis for colorectal cancer patients with liver metastases has not changed markedly. Furthermore, no standard adjuvant therapeutic regimen has been developed. Adjuvant therapy with monoclonal antibodies (e.g., against 17-1A), which has been shown to be effective in preventing metastatic relapse in patients with Dukes' C colorectal cancer, might be a promising approach for these patients. However, the cytotoxic effects of monoclonal antibodies can be blocked by coexpression of complement resistance factors that inhibit antibody-dependent complement-mediated cytotoxicity. We therefore analyzed immunohistochemically the expression of 17-1A and the membrane-bound complement resistance factors CD55 and CD59 on metastatic tumor cells in the livers of 71 patients with colorectal carcinoma who had undergone resection of their metastases with curative intent. In 67 (94%) of 71 patients, liver metastases with homogeneous expression of 17-1A was seen. Heterogeneous expression of 17-1A was seen in four patients (6%). Heterogeneous expression of CD55 or CD59 was observed in 8 (11%) of 71 patients and 4 (6%) of 71 patients, respectively. None of the patients showed homogeneous expression of either CD55 or CD59. All patients with CD55 or CD59 expression showed homogeneous 17-1A expression, whereas none of the four patients with heterogeneous 17-1A expression was positive for CD55 or CD59. Our data indicate that 17-1A is widely expressed on liver metastases of patients with colorectal carcinoma. Therefore patients with completely resected liver metastases might be suitable candidates for adjuvant therapy with and-17-1A antibody since only a few of these lesions showed coexpression of complement resistance factors.

Esophageal cancer: the mode of lymphatic tumor cell spread and its prognostic significance

PURPOSE

Data on skip metastases and their significance are lacking for esophageal cancer. This issue is important to determine the extent of lymphadenectomy for esophageal resection. In this study we examined the lymphatic spread in esophageal cancer by routine histopathology and by immunohistochemistry.

PATIENTS AND METHODS

A total of 1,584 resected lymph nodes were obtained from 86 patients with resected esophageal carcinoma and evaluated by routine histopathology. Additionally, frozen tissue sections of 540 lymph nodes classified as tumor-free by routine histopathology were screened for micrometastases by immunohistochemistry with the monoclonal antibody Ber-EP4. The lymph nodes were mapped according to the mapping scheme of the American Thoracic Society modified by Casson et al.

RESULTS

Forty-four patients (51%) had pN1 disease, and 61 patients (71%) harbored lymphatic micrometastases detected by immunohistochemistry. Skip metastases detected by routine histopathology were present in 34% of pN1 patients. Skipping of micrometastases detected by immunohistochemistry was found in 66%. The presence of micrometastases was associated with a significantly decreased relapse-free and overall survival (56.0 v 10.0 months and > 64 v 15 months, P <.0001 and P =.004, respectively). Cox regression analysis revealed the independent prognostic influence of micrometastases in lymph nodes. Lymph node skipping had no significant independent prognostic influence on survival.

CONCLUSION

Histopathologically and immunohistochemically detectable skip metastases are a frequent event in esophageal cancer. Only extensive lymph node sampling, in conjunction with immunohistochemical evaluation, will lead to accurate staging. An improved staging system is essential for more individualized adjuvant therapy.