Recently, cDNA microarray studies have identified multiple different genes that are aberrantly-expressed in aggressive human lung cancers. However, to translate these microarray-based results into improved therapies for cancer patients, the critical genes whose aberrant expression actually controls metastatic spread must now be identified. To date, functional assays for identifying such metastasis-controlling genes have been limited. Systemic gene transfer in adult, tumor-bearing mice is a powerful new approach to this problem. We now propose to use new systemic gene transfer technologies to identify which of nine selected genes (already identified by cDNA microarray studies to be aberrantly-expressed in poor prognosis, primary human lung cancers) actually control the metastatic spread of two different murine lung cancer tumor lines, LLC-LM and LLC-HM, in tumor-bearing mice. Our three specific aims are: Aim 1: To maximize the level and duration of gene expression produced in tumor-bearing mice by PEI- and IV, CLDC-based gene delivery. We will identify the most efficient, durably-expressing systemic gene transfer approaches for transfecting LLC-LM and LLC-HM cells in tumor-bearing mice. To accomplish this, we will optimize the: A) DNA carrier system, B) plasmid DNA:carrier ratio and C) repetitive dosing schedule. Aim 2: To use systemic delivery of selected cDNAs and ribozymes to identify specific genes that control the metastatic spread of lung cancers in mice. We will identify specific genes whose blocked expression or over-expression significantly reduces the metastatic spread of LLC-LM and HM in mice. Specifically, we will use plasmid-based ribozymes to target the endogenous expression of the CD98, cathepsin L, prostaglandin E synthase or VEGF-C genes, and use plasmid-based cDNAs to over-express the p21, 14-3-3, TGF-beta, thymosin beta or diacylglycerol genes. Each of these nine genes has already been identified by cDNA microarray studies to be aberrantly-expressed specifically in poor prognosis human lung cancers, and has been linked to the malignant phenotype. Aim 3: To identify pairs of metastasis-controlling cDNAs and/or ribozymes that act synergistically. We will assess IV co-injection of pairs of plasmid-based ribozymes and/or cDNAs that produce significant metastasis-controlling effects against murine lung cancer lines in Aim 2. We will assess multiple different dose combinations of each pair tested to determine whether there are specific interactions between each pair of genes. Overall, we will attempt to identify specific genes whose altered expression is functionally required for the metastatic spread of lung cancers. These critical metastasis-controlling genes can be specifically targeted by emerging small molecule-, protein- and gene-based therapeutic approaches; including those based on the more powerful systemic gene transfer approaches we have recently developed.