Differential Gene Expression of Primary Melanoma Versus Sentinel Lymph Node Metastasis
SS Koh, JJ Wei, X Li, AJ Cochran, SW Binder. University of California Los Angeles, Los Angeles, CA
Background: Melanoma is a potentially fatal cutaneous neoplasm with no effective treatment and 48,000 yearly deaths worldwide (WHO). Understanding of molecular mechanisms of metastasis is limited, contributing to the absence of effective treatments. Altered expression of genes that underpin molecular events leading to metastasis is of particular interest. We investigated gene expression profiles of primary melanomas and melanomas metastatic to sentinel nodes by DNA microarray technique.
Design: 8 primary melanomas and 3 melanomas metastatic to sentinel node were retrieved from UCLA archives. 2-4mm lesions were dissected from formalin fixed, paraffin-embedded blocks. Total mRNA was isolated, amplified and labeled using anAmbion Recover All™ Total Nucleic Acid Isolation kit, Nu-GEN WT-Ovation® FFPE RNA Amplification System and FL-Ovation® cDNA Biotin Module V2, respectively. Samples were then hybridized to the Affymetrix Gene Chip® Human U133 Plus 2.0 Array. Data analyses were performed using Partek® Genomics Suite Version 6.4. Differentially expressed genes were selected at >=2fold and p<0.05.
Results: Hierarchical clustering of the melanocytic lesions disclosed two distinct groups: the 8 primary melanomas and 3 sentinel node metastases. Analysis identified 278 statistically significant genes that were differentially expressed. Most differences were associated with decreased expression of genes by sentinel node metastases relative to primary melanomas. The reverse was rare. Interesting genes with relatively decreased expression in the sentinel node tumors were gap junction protein, keratin genes and stratifin.
Conclusions: DNA microarray system showed striking differential gene expression patterns between primary and nodally metastatic melanomas. From our list of significant genes, there is a predominant trend of relatively decreased expression of genes in nodal metastases relative to primary melanomas. Down regulation of genes is globally correlated with nodal metastasis by melanoma. Decreased genes are critically involved in cellular structural integrity (gap junction protein, keratins) and also in tumor suppression (stratifin). These initial studies of melanoma show that critical genes are differentially expressed in primary and nodal metastasis: preliminary findings that are consistent with current understanding of the molecular biology of tumors and may explain molecular events that underlie melanoma metastases and lead to the development of novel effective therapy.
Wednesday, March 24, 2010 1:00 PM
Poster Session VI # 82, Wednesday Afternoon