Microarray analysis and RNA silencing link fra-1 to cd44 and c-met expression in mesothelioma

Malignant mesothelioma is a cancer with poor prognosis associated with exposures to asbestos. The mechanisms of asbestos-induced mesotheliomas are unclear, and studies are required to find diagnostic tools and therapies to improve the survival rates of patients. After oligonucleotide microarray analysis (Affymetrix array) of normal rat pleural mesothelial (RPM) cells, RPM cells exposed to crocidolite asbestos, and rat mesotheliomas, subsets of genes that changed in expression were categorized, including the highly up-regulated, early response proto-oncogene, fra-1. Increases in fra-1 in both rat and human mesotheliomas and a subset of genes common to both asbestos-exposed RPM cells and mesotheliomas that mimicked fra-1 patterns of expression were subsequently confirmed using real-time quantitative PCR. Using RNA interference technology, fra-1 gene silenced RPM cells were assayed by real-time quantitative PCR for the expression of possible fra-1-regulated genes. Results reveal that induction of cd44 and c-met is causally linked to fra-1 expression, connecting fra-1 with genes governing cell motility and invasion in mesothelioma. These studies suggest that inhibition of fra-1 signaling pathways may be a strategy for therapy of malignant mesothelioma.