A High-Throughput Study in Melanoma Identifies Epithelial- Mesenchymal Transition As a Major Determinant of Metastasis
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Research Article A High-Throughput Study in Melanoma Identifies Epithelial- Mesenchymal Transition as a Major Determinant of Metastasis Soledad R. Alonso,1 Lorraine Tracey,1 Pablo Ortiz,4 Beatriz Pe´rez-Go´mez,5 Jose´ Palacios,1 Marina Polla´n,5 Juan Linares,6 Salvio Serrano,7 Ana I. Sa´ez-Castillo,6 Lydia Sa´nchez,2 Raquel Pajares,2 Abel Sa´nchez-Aguilera,1 Maria J. Artiga,1 Miguel A. Piris,1 and Jose´ L. Rodrı´guez-Peralto3 1Molecular Pathology Programme and 2Histology and Immunohistochemistry Unit, Centro Nacional de Investigaciones Oncolo´gicas; Departments of 3Pathology and 4Dermatology, Hospital Universitario 12 de Octubre; 5Centro Nacional de Epidemiologı´a, Instituto de Salud Carlos III, Madrid, Spain; and Departments of 6Pathology and 7Dermatology, Hospital Universitario San Cecilio, Granada, Spain Abstract with a less favorable prognosis as potential candidates for adjuvant Metastatic disease is the primary cause of death in cutaneous or novel therapies. malignant melanoma (CMM) patients. To understand the Currently, the prognosis of primary CMM is mainly based mechanisms of CMM metastasis and identify potential on histopathologic criteria. The most important of these is the predictive markers, we analyzed gene-expression profiles of Breslow index, although it is merely a measure of tumor depth. 34 vertical growth phase melanoma cases using cDNA micro- New molecular markers that correlate with melanoma genesis and/or progression are continuously being identified but, to date, arrays. All patients had a minimum follow-up of 36 months. Twenty-one cases developed nodal metastatic disease and 13 most of them have been obtained in experimental models and did not. Comparison of gene expression profiling of metastatic have not yet been confirmed in series of human samples. and nonmetastatic melanoma cases identified 243genes with The development of high-throughput screening techniques in a >2-fold differential expression ratio and a false discovery genomics and proteomics has enabled the analysis of the rate of <0.2 (206 up-regulated and 37 down-regulated). This expression of multiple genes and proteins in large series set of genes included molecules involved in cell cycle and of tumor samples (1) and may contribute to the resolution of apoptosis regulation, epithelial-mesenchymal transition some specific issues of clinical relevance, such as identifying the (EMT), signal transduction, nucleic acid binding and tran- steps for melanoma progression and metastasis. Until now, most scription, protein synthesis and degradation, metabolism, and studies characterizing CMM have been done using cell lines (2, 3), mouse models (4), or metastatic tumor samples (2, 5). However, a specific group of melanoma- and neural-related proteins. Validation of these expression data in an independent series data obtained from primary CMM samples are difficult to obtain, of melanomas using tissue microarrays confirmed that the due in part to the lack of retrospective collections of frozen expression of a set of proteins included in the EMT group primary melanomas samples or adequate follow-up (5–7). (N-cadherin, osteopontin, and SPARC/osteonectin) were sig- Molecular changes associated with the acquisition of metastatic nificantly associated with metastasis development. Our results capacity in vertical growth phase melanoma are still to be fully suggest that EMT-related genes contribute to the promotion described. We might expect a repertoire of differentially expressed of the metastatic phenotype in primary CMM by supporting genes defining the metastatic phenotype for primary CMM cases. specific adhesive, invasive, and migratory properties. These The present study aimed to investigate the metastasis signature data give a better understanding of the biology of this in primary CMM. To this end, we compared the gene expression aggressive tumor and may provide new prognostic and patient profile in a series of vertical growth phase primary CMMs that had stratification markers in addition to potential therapeutic developed metastatic disease with vertical growth phase CMM targets. [Cancer Res 2007;67(7):3450–60] without metastatic disease by the end of follow-up. Our results confirm the multifactorial genesis of melanoma metastasis and identify the epithelial-mesenchymal transition (EMT) and the Introduction relation with the extracellular matrix as key steps in melanoma progression. In primary cutaneous malignant melanoma (CMM) patients, it is essential to determine the molecular changes associated with metastasis and to apply this knowledge to the fields of outcome prediction and targeted treatment. This information will lead to a Materials and Methods better understanding of the biology of this tumor, and will probably Patients and tissue samples. This study featured a series of 34 primary provide prognostic information for defining subgroups of patients CMMs provided by the Hospital San Cecilio (Granada, Spain) and the Hospital 12 de Octubre (Madrid, Spain). Patients were recruited between 1990 and 2002 to ensure a minimum follow-upof 36 months. Samples were collected and frozen according to standard protocols, and their histology Note: Supplementary data for this article are available at Cancer Research Online was reviewed by two pathologists (S.R.A. and J.L.R-P.) to confirm that they (http://cancerres.aacrjournals.org/). contained at least 50% tumor cells. All selected cases corresponded to Requests for reprints: Miguel A. Piris, Programa de Patologı´a Molecular, Centro consecutive melanoma tumors with potential metastatic capacity (i.e., Nacional de Investigaciones Oncolo´gicas, C/Melchor Ferna´ndez Almagro 3, Madrid vertical growth phase cases with a Breslow index >1 mm). The cutoff was 28029, Spain. Phone: 34-91-224-69-00; Fax: 34-91-224-69-23; E-mail: [email protected]. I2007 American Association for Cancer Research. selected taking into account the criteria of the American Joint Committee doi:10.1158/0008-5472.CAN-06-3481 on Cancer by which thin melanomas (V1 mm) have an excellent prognosis Cancer Res 2007; 67: (7). April 1, 2007 3450 www.aacrjournals.org Downloaded from cancerres.aacrjournals.org on October 1, 2021. © 2007 American Association for Cancer Research. Metastasis Signature in Melanoma Table 1. Antibodies used in the study indicating clone, source, dilution, visualization method, scoring, threshold, and positive controls Protein Clone Source Dilution Visualization Scoring Threshold Positive control system Glypican 3 Polyclonal Santa Cruz 1:25 LSAB/DAB Pos/neg >10% positive cells Hepatocarcinoma Biotechnology N-cadherin 3B9 Zymed 1:10 LSAB/DAB Pos/neg z5% positive cells, Ovarian carcinoma, membranous expression cardiac muscle SPARC/ 15G12 Novocastra 1:25 LSAB/DAB Pos/neg >10% positive cells, cytoplasm Endothelial cells in osteonectin malignant tumors Osteopontin Polyclonal Abcam 1:1,500 LSAB/DAB Pos/neg >10% positive cells, cytoplasm Stromal cells in normal skin PKCa H7 Santa Cruz 1:25 LSAB/DAB High/low z50% positive cells, cytoplasm Small lymphocytes, nevus Biotechnology Abbreviations: Pos/neg, positive/negative; LSAB, peroxidase-labeled streptavidin biotin; DAB, diaminobenzidine. (>90% survival at 5 years) compared with melanomas with a penetration online.8 Sample hybridizations were done as described elsewhere (12). depth of >1 mm (8). Histologic review of the cases was done on paraffin- After washing, the two fluorescent signals on the slides were scanned with embedded tissue, whereas frozen sections were examined for assessing the a standard two-color microarray scanner (Scanarray 5000XL, GSI proportion of the tumoral cells and the character of the neoplastic Lumonics, Kanata, Ontario, Canada). Images were analyzed with the infiltrate. GenePix 4.1 software (Axon Instruments, Inc., Union City, CA). The clone For tissue microarray (TMA) analysis, we used a retrospective cohort sequences of all the genes included in the OncoChipand the repro- of patients representing 127 primary vertical growth phase melanoma ducibility of the expression data of multiple genes have been previously cases (formalin-fixed and paraffin-embedded tissue) collected from 1980 verified (12). to 2000. These cases were obtained from the Hospital 12 de Octubre Data extraction and analysis. Data from each hybridization were (Madrid) and were included in six separate TMAs (1.5-mm core maintained in a database for analysis. Fluorescence intensity measurements diameter), with two representative duplicate cores for each case (9), were subjected to automatic background subtraction. The Cy3/Cy5 ratios and constructed with a manual tissue arrayer (Beecher Instruments, Sun were normalized to the value of the median ratio of all spots in the array. Prairie, WI) using a standard method (10). Patient medical records were The sum of the median background for each channel was calculated, reviewed to gather information on age, gender, localization, tumor and spots with total intensities less than the calculated sum of median thickness, distant invasion (lymph node or skin), and follow-up of at backgrounds were discarded. Additionally, spots with background- least 36 months. Patients were not treated before the development of subtracted signal intensities <500 fluorescence units (sum of the two metastasis. The work was conducted in accordance with the Declaration channels) and bad spots were excluded from the analysis. All ratio values of Helsinki Principles and under the supervision of the Hospital 12 de were log-transformed (base 2), and duplicated spots in the array