A Novel Candidate Gene for Promotion of Melanoma Progression
B Horst, K Chernoff, L Bordone, G Brunner, J Celebi. UCLA, LA, CA; Columbia University, NY, NY; Fachklinik Hornheide, Muenster, Germany
Background: Malignant Melanoma is the most common fatal skin cancer, and shows the fastest rising incidence of all cancers in the US. Current therapy is restricted to surgical excision during early tumor stages, and treatment strategies for advanced disease have not proven significant durable responses. New molecular and genetic targets are being identified and tested in clinical trials. The aim of the current study was to identify novel genes which may play a role in melanoma progression and offer a potential target for regional or systemic tumor therapy.
Design: New molecular genetic techniques allow high resolution genome-wide exploration of DNA copy number and are effective tools in the search for amplification or loss of chromosomal regions. We performed a genome-wide search using BAC CGH and SNP arrays in 63 metastatic melanomas. Overexpression of candidate genes of amplified regions was confirmed by qPCR. Metastatic melanoma cell lines were screened for overexpression of respective loci and selected to assess the impact on invasive capacity of specific downregulation of target genes. Overexpression was confirmed in an independent series of melanocytic lesions, including nevi, primary melanomas as well as melanoma metastases.
Results: We identified distinct amplifications of the 11q13 genomic region in metastatic melanomas. CyclinD1 on 11q13.2 accounted for a subset of these amplifications. Fine mapping delineated a second amplification core. qPCR revealed amplification of a specific locus encoding a critical signal transduction scaffolding protein at the amplicon center. Metastatic melanoma cell lines with overexpression at this locus were subjected to in vitro invasion assays in the presence of small interfering RNAs and showed a significant reduction in invasive capacity. Increased protein expression could be confirmed in malignant melanomas as compared to melanocytic nevi by immunofluorescent studies in an independent set of melanocytic tumors.
Conclusions: We have identified a novel target gene by genome-wide screening which shows significant upregulation in metastatic melanomas as compared to benign melanocytic lesions. The reduction in invasive capacity by RNA interference is encouraging and warrants in vivo studies to assess for a potential therapeutic target. As mechanisms of resistance to conventional chemotherapy of metastatic melanoma are being investigated, identification of new molecular and genetic targets is a useful means to advance treatment of melanoma.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 45, Wednesday Morning