Widespread evidence suggests that a unifying principle governing the molecular pathology of cancer is the co-dependent aberrant regulation of core machinery driving proliferation and suppressing apoptosis. Anomalous proteins engaged to support a tumorigenic regulatory environment likely represent optimal intervention targets in a heterogenous population of cancer cells. The advent of RNAi-based functional genomics provides the opportunity to derive unbiased comprehensive collections of validated gene targets supporting critical biological systems outside the framework of preconceived notions of mechanistic relationships. Here, I have combined a high throughput cell-based one-well/one-gene screening platform with an arrayed genome-wide synthetic siRNA library for systematic interrogation of the molecular underpinnings of cancer cell chemoresponsiveness. NCI-H1155, a human non small cell lung cancer line, was employed for a paclitaxel-dependent synthetic lethal screen designed to identify gene targets that specifically reduce cell viability in the presence of otherwise suboptimal pactlitaxel concentrations. Using a stringent objective statistical algorithm to reduce false discovery rates below 5%, we isolated a panel of 87 genes that represent major fulcrums of the cancer cell autonomous response to abrogation of microtubule dynamics. Importantly, a number of these targets sensitize lung cancer cells to paclitaxel concentrations 1000-fold lower than otherwise required for a significant response, and reveal novel mechanistic relationships between cancer-associated aberrant gene expression programs and the basic cellular machinery required for robust mitotic progression. In the studies proposed herein, I plan to characterize the mechanism of action of these targets and determine if they are required for tumor cell survival and chemoresistance in vivo. My specific aims are to 1: Defining the contribution of novel paclitaxel sensitizers to cancer cell spindle assembly and function. 2: Validate effectiveness of candidate therapeutic targets with orthotopic xenograft models of lung cancer. 3: Isolate the core components of the cancer cell network that liberate chemoresistant tumors from mitotic catastrophe checkpoints. [unreadable] [unreadable] With respect to public health, these studies will aid in identifying both novel chemotherapeutics as well as novel combinations of existing chemotherapeutics to better treat cancer. [unreadable] [unreadable] [unreadable] [unreadable]