17077 Background: The overall 5-yr survival for the treatment of lung cancer patients is less than 20% due to the inability to control metastatic disease. Methods: To identify genes that promote the development of metastases in NSCLC and other solid tumors, we first performed three separate microarray analyses using Affymetrix U133A chips whereby expression values of a pool of normal lymph nodes was compared to: lung cancer cell lines (n = 4), and metastatic lymph nodes from breast (n = 3) and pancreatic (n = 3) cancer patients. Separate lists of the 35 most highly overexpressed genes for each cancer type were compiled. Results: We observed that each list contained EpCAM, XAG, CK19, and CK8 (p = 1.1E-18). To search for genes that might regulate expression of these four genes, we queried the CGAP NCI60 gene expression database with the 87 genes contained on the three lists and constructed a connectivity map such that the presence of a gene on the map required: 1) high correlation (p < 8.0E-6) with at least two other genes, and 2), direct or indirect contact to EpCAM or XAG. The map contained two gene clusters (XAG cluster = 6 genes; EpCAM/CK19/CK8 cluster = 7 genes) that were connected to, and potentially regulated by, the Ets transcriptional factor Esx. Genes from both clusters, as well as Esx, were highly overexpressed in metastatic mediastianal lymph nodes obtained from NSCLC patients. To investigate whether Esx might regulate expression of one or more genes in the two clusters, we transfected an NSCLC cell line derived from lymph node metastases with siRNA to Esx and observed: 1) a reduction in expression of EpCAM (4-fold), XAG (7-fold), and the orphan nuclear receptor ESRRα (1,000-fold), and 2), an inhibition of cell growth. Conclusions: Based on our ability to simultaneously inhibit cell growth and expression of multiple metastasis-associated genes with a single siRNA, we conclude that Esx is a major regulator of lymph node metastasis. No significant financial relationships to disclose.