Identification of differentially expressed genes in matched primary and metastatic melanoma tumor pairs

ABSTRACT: Comparison of gene expression profiles between a primary melanoma and an early metastatic specimen from the same patient will provide essential biological insight into early metastatic processes. The DASL (cDNA mediated annealing, selection, extension and ligation) assay has been used to generate gene expression data for 502 cancer-related genes from very small formalin-fixed sentinel node biopsy (SNB) melanoma samples, this data has been further compared with gene expression of the matched formalin-fixed primary melanoma. Tissue was sampled from twenty-five SNB deposits using laser capture microdissection. The mean number of genes detected using DASL with SNB samples was lower than when using a core of primary melanoma tumor (242 versus 434 genes). A large proportion of SNB samples failed (<240 genes detected) the assay (57.7%). Area of tissue microdissected, RNA concentration and qRT-PCR quality control did not predict performance of samples on the array but age of sampled tissue negatively correlated with number of genes detected (p=0.01). For samples that performed successfully, matched primary samples were available for 10 samples. Gene expression profiles correlated between all matched tumor pairs (Spearman’s rho 0.15-0.80, p<0.01), although a number of genes were differentially expressed between nodal and primary tumors in all tumor pairs. This study demonstrates that the DASL assay can be used to generate gene expression data from small formalin-fixed samples, but not consistently. Differentially expressed genes were identified across 10 matched primary and nodal tumor pairs suggesting that the DASL assay could be used to derive essential biological information about early metastasis. Formalin-fixed paraffin-embedded SNB samples and primary tumors were identified from two study sets. In Study 1, population ascertained melanoma patients were recruited to a cohort in the period from 2000 till the present day. Eight positive SNB samples were identified, from patients whose primary tumors had already been sampled for DASL studies. In Study 2, seventeen positive SNB samples were identified in a study designed to identify predictors of sentinel node positivity and relapse (SNB study). One nodal RNA sample, microdissected from a diagnostic H&E slide, was not sent for DASL analysis because of low RNA concentration (0.37 ng/μl), therefore a total of 26 nodal samples (including 2 replicate samples) were supplied to the Illumina DASL service provider. Of the 11 samples successfully yielding gene expression data, 10 had matched primary samples (e.g., Node_1 and Primary_1) for which gene expression data were available and is presented in this data set.

ORGANISM(S): Homo sapiens

SUBMITTER: Rosalyn Jewell 

PROVIDER: E-GEOD-31139 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress