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Gene expression changes associated with prognosis of Merkel cell carcinoma

ABSTRACT: Purpose: Due to the rarity of Merkel Cell Carcinoma (MCC), prospective clinical trials have not been practical. This study seeks to identify biomarkers to differentiate between patients with a good and poor prognosis. Methods: Patients were stratified into good, moderate or poor prognosis. Merkel cell carcinoma (MCC) patients were stratified into one of three groups based upon status 24 months following treatment. Poor prognosis patients either presented with or progressed to distant metastasis. Patients with favorable prognosis had local disease presentation with no subsequent recurrence or nodal disease at presentation with no progression during follow-up of longer than 24 months. Moderate prognosis had recurrent local disease, development of nodal metastasis, or nodal disease at presentation with no progression during follow-up of fewer than 24 months. Using ArcturusXT Laser Capture Microdissection (Molecular Devices), tumor cells were isolated from the specific areas of interest. The captured tumor tissue was subjected to RNA extraction using the Invitrogen PureLink™ FFPE RNA Isolation Kit. The extracted RNA was analyzed for integrity with the Agilent Bioanalyzer then amplified and hybridized to Affymetrix GeneChip Human Exon 1.0 ST arrays using the NuGEN WT- Ovation™ FFPE System. Results: A total of 191 genes showed significant differential expression (p≤0.05 and 1.5-fold cutoff) between the different between the good and poor prognosis groups. Keratin 20 (KRT20) and Neurofilament protein (NEFM) have been identified in previous studies as proteins of interest in MCC. Our study showed these genes to be significantly upregulated in patients with a poor prognosis. Of interest, phospholipase A2, group X was upregulated in poor responders. Phospholipases liberate arachidonic acid from cellular membranes which can be metabolized to eicosanoids through three major pathways: the cyclooxygenase (COX), the lipoxygenase (LOX) and the cytochrome P450 monooxygenase pathways. This pathway has been implicated in several cancers. Conclusions: The study identified genes with a previous association with MCC as well as some novel genes. These genes provide the basis for further research into possible biomarkers that will enable the differentiation between patients with a good and poor prognosis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE36150 | GEO | 2014/02/20

SECONDARY ACCESSION(S): PRJNA152891

REPOSITORIES: GEO

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Project description:Purpose: Due to the rarity of Merkel Cell Carcinoma (MCC), prospective clinical trials have not been practical. This study seeks to identify biomarkers to differentiate between patients with a good and poor prognosis. Methods: Patients were stratified into good, moderate or poor prognosis. Merkel cell carcinoma (MCC) patients were stratified into one of three groups based upon status 24 months following treatment. Poor prognosis patients either presented with or progressed to distant metastasis. Patients with favorable prognosis had local disease presentation with no subsequent recurrence or nodal disease at presentation with no progression during follow-up of longer than 24 months. Moderate prognosis had recurrent local disease, development of nodal metastasis, or nodal disease at presentation with no progression during follow-up of fewer than 24 months. Using ArcturusXT Laser Capture Microdissection (Molecular Devices), tumor cells were isolated from the specific areas of interest. The captured tumor tissue was subjected to RNA extraction using the Invitrogen PureLinkM-bM-^DM-" FFPE RNA Isolation Kit. The extracted RNA was analyzed for integrity with the Agilent Bioanalyzer then amplified and hybridized to Affymetrix GeneChip Human Exon 1.0 ST arrays using the NuGEN WT- OvationM-bM-^DM-" FFPE System. Results: A total of 191 genes showed significant differential expression (pM-bM-^IM-$0.05 and 1.5-fold cutoff) between the different between the good and poor prognosis groups. Keratin 20 (KRT20) and Neurofilament protein (NEFM) have been identified in previous studies as proteins of interest in MCC. Our study showed these genes to be significantly upregulated in patients with a poor prognosis. Of interest, phospholipase A2, group X was upregulated in poor responders. Phospholipases liberate arachidonic acid from cellular membranes which can be metabolized to eicosanoids through three major pathways: the cyclooxygenase (COX), the lipoxygenase (LOX) and the cytochrome P450 monooxygenase pathways. This pathway has been implicated in several cancers. Conclusions: The study identified genes with a previous association with MCC as well as some novel genes. These genes provide the basis for further research into possible biomarkers that will enable the differentiation between patients with a good and poor prognosis. Using laser capture microdissection, tumor cells of patients with a good (n=5), moderate (n=3), and poor prognosis (n=7) were isolated from paraffin embedded archival tissue of 15 patients with Merkel cell carcinoma. Affymetrix Human Exon 1.0ST microarrays were utilized to compare gene expression signatures from good and poor prognosis patients.

Project description:Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor with high mortality rates. Merkel cell polyomavirus (MCPyV), identified in the majority of MCC, may drive tumorigenesis via viral T antigens. However, mechanisms underlying pathogenesis in MCPyV-negative MCC remain poorly understood. To nominate genes contributing to pathogenesis of MCPyV-negative MCC, we performed DNA microarray analysis on 30 MCCs. MCPyV status of MCCs was determined by PCR for viral DNA and RNA. 1593 probe-sets were differentially expressed between MCPyV-negative and -positive MCC, with significant differential expression defined as at least 2-fold change in either direction and p-value of ≤ 0.05. MCPyV-negative tumors showed decreased RB1 expression, whereas MCPyV-positive tumors were enriched for immune response genes. Validation studies included immunohistochemistry demonstration of decreased RB protein expression in MCPyV-negative tumors and increased peritumoral CD8+ T lymphocytes surrounding MCPyV-positive tumors. In conclusion, our data suggest that loss of RB1 expression may play an important role in tumorigenesis of MCPyV-negative MCC. Functional and clinical validation studies are needed to determine whether this tumor suppressor pathway represents an avenue for targeted therapy. We used microarrays to characterize global gene expression patterns related to Merkel cell polyomavirus status in Merkel cell carcinoma. Furthermore, we compared Merkel cell carcinoma to less aggressive primary cutaneous carcinomas. We utilized flash-frozen tumor tissue from primary Merkel cell carcinomas, metastatic Merkel cell carcinomas, primary cutaneous squamous cell carcinomas, and basal cell carcinomas. Merkel cell carcinoma cell lines, which represent a pure population of tumor cells, were also included. Merkel cell polyomavirus status was determined at the DNA and RNA level using multiple primers for viral T-antigen and capsid protein sequences. This Series represents two analyses - one with new Samples normalized together, and another with some of the new Samples re-normalized with Samples previously submitted under Series GSE13355. The latter group contain 'renormalized' in the titles.

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Gene expression changes associated with prognosis of Merkel cell carcinoma

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