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Genetic alteration in recurrent melanoma

ABSTRACT: It is generally accepted that human cancers derive from a mutated single cell. However, the genetic steps characterizing various stages of progression remain unclear. Studying a unique case of metastatic melanoma, we observed that cell lines derived from metachronous metastases arising over a decade retained a central core of genetic stability in spite of divergent phenotypes. In the present study we expanded our previous observations comparing these autologous cell lines of clonal derivation with heterologous ones and correlated array Comparative Genomic Hybridization (aCGH) with gene expression profiling to determine their relative contribution to the dynamics of disease progression. aCGH and gene expression profiling were performed on autologous cell lines and heterologous melanoma cell lines originated from other patients. A striking correlation existed between total extent of genetic imbalances, global transcriptional patterns and cellular phenotypes; they did not follow a strict temporal progression but stemmed independently at various time points from a central core of genetic stability best explained according to the cancer stem cell hypothesis; although their contribution was intertwined, genomic imbalances detectable by aCGH contributed only 25% of the transcriptional traits determining autologous tumors distinctiveness. Our study provides important insights about the dynamics of cancer progression and supports the development of targeted anti-cancer therapies against stable genetic factors determining the individuality of each patient’s disease that are maintained throughout the end stage of disease. Keywords: genetic modification design

ORGANISM(S): Homo sapiens

PROVIDER: GSE8777 | GEO | 2008/07/22

SECONDARY ACCESSION(S): PRJNA102067

REPOSITORIES: GEO

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Project description:It is generally accepted that human cancers derive from a mutated single cell. However, the genetic steps characterizing various stages of progression remain unclear. Studying a unique case of metastatic melanoma, we observed that cell lines derived from metachronous metastases arising over a decade retained a central core of genetic stability in spite of divergent phenotypes. In the present study we expanded our previous observations comparing these autologous cell lines of clonal derivation with heterologous ones and correlated array Comparative Genomic Hybridization (aCGH) with gene expression profiling to determine their relative contribution to the dynamics of disease progression. aCGH and gene expression profiling were performed on autologous cell lines and heterologous melanoma cell lines originated from other patients. A striking correlation existed between total extent of genetic imbalances, global transcriptional patterns and cellular phenotypes; they did not follow a strict temporal progression but stemmed independently at various time points from a central core of genetic stability best explained according to the cancer stem cell hypothesis; although their contribution was intertwined, genomic imbalances detectable by aCGH contributed only 25% of the transcriptional traits determining autologous tumors distinctiveness. Our study provides important insights about the dynamics of cancer progression and supports the development of targeted anti-cancer therapies against stable genetic factors determining the individuality of each patientâs disease that are maintained throughout the end stage of disease. Keywords: genetic modification design PBMC from a female donor were Ficoll gradient separated and used throughout the study as reference.. Validation of array CGH accuracy was done by obtaining six additional PBMC from female donors and six PBMC from male donors to confirm stability of gene representation in autosomes and sex-determined imbalances within the X and Y chromosome regions. Five melanoma cell lines were generated from distinct cutaneous melanoma metastases that progressively appeared in patient 888. Other melanoma cell lines were generated from cutaneous melanoma metastases from other patients. The melanoma cell line A375 was purchased from the American Type Culture Collection. For each cell line arrayCGh has been performed.

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).

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Genetic alteration in recurrent melanoma

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