Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression analysis of recurrent metastatic melanoma lesions

ABSTRACT: In this study, we sought to indentify stable individual traits in developing metastatic melanoma, assess their stability in time, and analyze typical dynamics and common trends of genomic changes in individual cases of late stage metastatic cancer. To this end, we compared consecutive recurrent metastases developed by a special group of eight individuals with advanced metastatic melanoma, all developing several recurrent metastases over several months to years of natural disease evolution. Twenty-six recurrent melanoma metastases were surgically isolated from 8 patients experiencing relapse after one or more successful treatment intervention(s) with no signs of residual disease. Patients experiencing recurrent metastases were labeled with capital letters; M-bM-^@M-^\AM-bM-^@M-^], M-bM-^@M-^\BM-bM-^@M-^], M-bM-^@M-^\CM-bM-^@M-^], etc., their subsequent metastases as M-bM-^@M-^\A/1M-bM-^@M-^], M-bM-^@M-^\A/2M-bM-^@M-^], M-bM-^@M-^\B/1M-bM-^@M-^], M-bM-^@M-^\B/2M-bM-^@M-^], etc., while synchronous metastases in a given patient were labeled as M-bM-^@M-^\A/1aM-bM-^@M-^], M-bM-^@M-^\A/1bM-bM-^@M-^] etc. Another 22 melanoma cell lines isolated and maintained as above were expanded from melanoma patients with rapid disease curse, for whom only one metastasis was available. As no extended follow up was possible in these cases, the cell lines are considered representative of random time points in the natural course of metastatic melanoma. These cell lines were labeled with Arabic numbers, as M-bM-^@M-^\1M-bM-^@M-^], M-bM-^@M-^\2M-bM-^@M-^], M-bM-^@M-^]3M-bM-^@M-^], etc

ORGANISM(S): Homo sapiens

SUBMITTER: Zoltan Pos

PROVIDER: E-GEOD-38119 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Melanoma recurrence frequently occurs after a latency period of several years. In vivo studies demonstrated that tumor cells overcoming latency show a T cell-edited phenotype, suggesting a relevant role for CD8+ T cells in maintaining metastatic latency. Here, in a patient model of multiple recurrent lesions, we illustrate the genetic evolution of poorly immunogenic melanoma phenotypes, evolving in the presence of autologous tumor antigen-specific CD8+ T cells. Melanoma cells from two of three late recurrent metastases, developing within a 6-year latency period, lacked HLA class I expression. HLA class I-negative tumor cells became clinically apparent 1.5 and 6 years into stage IV disease. Genome profiling by SNP arrays revealed total T-cell resistance in both metastases originating from a shared chromosome 15q alteration and independently acquired focal B2M gene deletions. A third HLA class I-positive lesion developed in year 3 of stage IV disease. By HLA haplotype loss lesion-derived melanoma cells acquired resistance towards dominant T-cell clonotypes targeting early stage III tumor cells. Early disease melanoma cells showed a dedifferentiated MITFnegative phenotype, recently described to be associated with immunosuppression, in contrast to the MITFhigh phenotype of T cell-edited tumor cells from late metastases. In summary, our study demonstrates that tumor recurrences after long-term latency develop towards T-cell resistance by independent genetic events, suggesting a mechanism of T cell-driven genetic evolution of melanoma as a means to evade immune recognition and tumor immunotherapy. Genetic alterations lead to loss of tumor antigen presentation. Cell lines were generated from tumor material, differences in T cell recognition were observed and Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from the cell lines. SNP analysis of different melanoma cell lines obtained from one melanoma patient (4 cell lines from different metastasis of one patient with matching germline DNA).

Project description:Circulating tumor cells (CTCs) are critical in the development of distant organ tumor metastasis, and are associated with advanced cancer stage and poor patient outcome. Here, we present the first genome-wide nucleotide-level characterization of CTCs. Our single-nucleotide polymorphism (SNP) analysis in patients with melanoma involved: 1) global comparative genomic analysis of CTCs and matched regional metastases, 2) identification of key genomic aberrations in CTCs, 3) verification of these target genes in aggressive distant tumor metastases, and 4) evidence of selective expression and functional consequence of CTC-associated genes in melanomas. We report 131 aberrant loci in CTCs that are potentially pro-metastatic, and show that such expression of a 5-marker gene panel (CSMD2, CNTNAP5, FLJ14051, ADAM6, TRPM2) in melanomas confers prognostic utility. Successful treatment of melanoma requires understanding of the metastatic process and identification of patients with tumors most likely to develop aggressive metastatic disease. Melanomas are heterogeneous, and CTCs have long been recognized as vehicles for cancer spread, representing particularly aggressive tumor clones that can evolve into successful clinical metastases. Elucidation of genomic aberrations in CTCs will aid in the development of prognostic biomarkers and therapeutic strategies to target CTCs to prevent or control distant cancer spread. This study provides the first detailed genomic confirmation of the close relation between CTCs and tumor metastases, and illustrates how CTCs can be utilized as a novel approach and rational source for identification of pro-metastatic genes in cancer research. Three individual patient cohorts were utilized in the study. CNV and LOH loci were evaluated initially in metastatic melanoma patients (n=13) in a discovery cohort. SNP loci that harbored CNV/LOH in CTCs were then separately verified for: (a) presence in distant organ metastasis (AJCC Stage IV melanoma) (n=27), and (b) relevance to prognosis in regional melanoma metastasis (AJCC Stage III melanoma) (n=35). The first discovery patient cohort group was utilized for capture of CTCs, and consisted of peripheral blood mononuclear cell (PBMC) and tumor specimens from metastatic melanoma patients (n=13). CTC-related loci were verified in a second cohort of patients with Stage IV distant organ metastases (n=27), including 15 brain, 4 lung, and 8 gastrointestinal (bowel, liver) metastases. The third patient cohort consisted of early passage (<12) established melanoma cell lines derived from 35 regional melanoma metastases (Stage III) for evaluation of the prognostic utility of the CTC-associated aberrant loci.

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Gene expression analysis of recurrent metastatic melanoma lesions

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