Increased chromosome 20 copy number detected by fluorescent in situ hybridization (FISH) in malignant melanoma

Abstract

DNA amplification is an important mechanism of tumor progression that allows cancer cells to up-regulate expression of critical genes such as oncogenes. Recent studies using comparative genomic hybridization revealed increased DNA copies on chromosome 20q in seven melanoma cell lines and eight archival metastatic melanoma lesions. We performed FISH analysis of metaphase spreads in 13 melanoma cell lines and nine primary melanoma specimens using a variety of probes 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. Cytological evidence for gene amplification was found in one of the 13 cell lines with an add(20)(p13). These data suggest that over-representation of a gene(s) important for melanoma pathogenesis occurs on the chromosome 20 long arm.