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Copy number variation analysis of hepatic metastases from uveal melanoma

ABSTRACT: Metastatic uveal melanoma (MUM) is chemoresistant and usually fatal within one year of diagnosis. There is an urgent need to better understand disease pathogenesis, in order to determine key drivers of the metastatic process that could be effectively targeted by therapy. Gene copy number variations occurring in a rare cohort of 13 metastatic and six matched primary, formalin-fixed, paraffin-embedded uveal melanoma samples were identified using the Affymetrix Genome-Wide Human SNP 6.0 Array. Gross chromosomal abnormalities commonly seen in primary UM and associated with the development of metastasis were observed in the MUMs. The most common CNVs were gene amplifications on chromosome 8q, especially in the region 8q24.3. Interestingly, deletions on chromosome 3 were detected at a lower frequency. Genomic profiles of PUM-MUM pairs varied in their degree of similarity and complexity. No genes were altered being unique to either all PUMs or all MUMs of the pairs, but 135 gene CNVs were consistently shared. Of these genes, 125 were amplifications located on chr. 8q24.3. Five genes in the region 8q24.3 and two genes on chromosome 3 were selected for validation by immunohistochemistry because of their known function in cancer (BCL6, C-MYC, E2F5, PTP4A3, SNAI2, and WISP1), or known importance in UM pathology (BAP1). The functional effect of these CNVs on protein expression was confirmed; amplified genes showed increased expression and deleted genes reduced expression. To conclude, our data demonstrate frequent amplification of chromosome 8q in MUMs, suggesting that genes facilitating the expansion of UM in the metastatic niche occur in this region. Furthermore, validation of a range of amplified 8q genes at the protein level strongly indicates the CNVs may be functional and, contribute to MUM biology.

ORGANISM(S): Homo sapiens

PROVIDER: GSE69614 | GEO | 2016/05/18

SECONDARY ACCESSION(S): PRJNA285989

REPOSITORIES: GEO

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Project description:Analysis of DNA from fixed tissues specimens of 58 primary uveal melanomas, with known clinical outcome, to determine gene copy number variations that were associated with survival. Abstract: Uveal melanomas can be stratified into subgroups with high or low risk of metastatic death, according to the presence of gross chromosomal abnormalities. Where a monosomy 3 uveal melanoma is detected, patient survival at three years is reduced to 50%. However, approximately 5% of patients with a disomy 3 tumour ultimately develop metastasis, and a further 5% of monosomy 3 uveal melanoma patients’ exhibit disease-free survival for more than five years. Despite extensive knowledge of the chromosomal abnormalities occurring in uveal melanoma, the genes driving metastasis are not well defined. Gene copy number variations occurring in a well-characterised cohort of 58 formalin-fixed, paraffin-embedded uveal melanoma samples were identified using the Affymetrix SNP 6.0 whole genome microarray. Four genetic sub-groups of primary uveal melanoma were represented in the patient cohort: 1) disomy 3 with long-term survival; 2) metastasizing disomy 3; 3) metastasizing monosomy 3; and 4) monosomy 3 with long-term survival. Cox regression and Kaplan-Meier survival analysis identified three genes that were associated with differences in patient survival. Patients with an amplification of CNKSR3 (6q) or RIPK1 (6p) demonstrated longer survival than those with gene deletions or no copy number change (log rank, p=0.022 and p<0.001, respectively). Conversely, those patients with an amplification of PENK (8q) showed reduced survival (log rank p<0.001). CNKSR3, RIPK1 and PENK are novel candidate metastasis regulatory genes in uveal melanoma. This is the first report of amplification of a specific gene on 6p that is associated with improved uveal melanoma patient survival and suggests that the development of uveal melanomas with a propensity to metastasise may be limited by genes on 6p. 58 samples in total. Ten disomy 3 with long-term survival. Fifteen disomy 3 with metastasising. Seventeen monosomy 3 with long-term survival. Sixteen monosomy 3 metastasising.

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Copy number variation analysis of hepatic metastases from uveal melanoma

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