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Increased chromosome 20 copy number detected by fluorescence in situ hybridization (FISH) in malignant melanoma
J H Barks1, F H Thompson, R Taetle
1Graduate Interdisciplinary Program in Genetics, University of Arizona, Tucson, USA.
Abstract:
DNA amplification is an important mechanism of tumor progression that allows cancer cells to up-regulate the expression of critical genes such as oncogenes and genes conferring drug resistance. Recent studies using comparative genomic hybridization (CGH) revealed increased DNA copies of 20q sequences in 7 melanoma cell lines and B archival metastatic melanoma lesions. To evaluate chromosome 20 abnormalities in more detail and to resolve discrepancies between karyotype and CGH findings, we performed FISH analysis of metaphase cells in 13 melanoma cell lines (including the 7 lines used for CGH) and 9 primary melanoma specimens by using a whole chromosome paint specific for chromosome 20. All 13 cell lines (100%) and 8/9 primary tumors (89%) showed extra copies of chromosome 20 relative to tumor ploidy. Additionally, 6/14 cell lines (43%) and 2/8 primary tumors (25%) showed translocated chromosome 20 material previously undetected by standard cytogenetics. Cytologic evidence for gene amplification was also found in one cell line, which contained an add(20)(p13), with additional DNA being derived from 20q sequences. These data suggest that overrepresentation of a gene or genes important for melanoma pathogenesis resides on the long arm of chromosome 20.
Insights
DNA amplification in chromosome 20 is common in melanoma, driving tumor progression. FISH analysis revealed extra chromosome 20 copies and translocations in most melanoma cell lines and primary tumors.
Area of Science:
- Genetics
- Oncology
- Molecular Biology
Background:
- DNA amplification drives tumor progression by up-regulating oncogenes and drug resistance genes.
- Comparative genomic hybridization (CGH) identified increased 20q sequences in melanoma.
- Discrepancies between karyotype and CGH necessitate detailed evaluation of chromosome 20 abnormalities.
Purpose of the Study:
- To investigate chromosome 20 abnormalities in melanoma using FISH analysis.
- To resolve discrepancies between karyotype and CGH findings in melanoma.
- To identify potential genes involved in melanoma pathogenesis on chromosome 20.
Main Methods:
- Fluorescence in situ hybridization (FISH) analysis was performed on metaphase cells.
- A whole chromosome paint specific for chromosome 20 was used.
- Analysis included 13 melanoma cell lines and 9 primary melanoma specimens.
Main Results:
- 100% of cell lines and 89% of primary tumors showed extra copies of chromosome 20.
- Translocated chromosome 20 material was detected in 43% of cell lines and 25% of primary tumors.
- Gene amplification evidence was found in one cell line with an add(20)(p13).
Conclusions:
- Overrepresentation of chromosome 20 is a frequent event in melanoma.
- The long arm of chromosome 20 (20q) likely harbors genes critical for melanoma pathogenesis.
- FISH analysis provides detailed insights into chromosome 20 alterations in melanoma.