Lung cancer is the leading cause of cancer deaths in Canada. In recent years, more non-smokers are being diagnosed with lung cancer, causing a major public concern. Non-small cell lung cancer (NSCLC) accounts for about 80% of the cases of which two-thirds of the patients have reached the inoperable stage at diagnosis. Standard of care for these patients is a combination of two chemotherapy drugs, with one typically being cisplatin. Even with two agents, the 5-year survival rate is less than 20%, suggesting a great need for new drug combinations to improve treatment outcomes. We propose that certain genes and pathways are activated in cancer cells when they are first exposed to chemotherapy, allowing cancer cells to survive. Inhibiting these genes or gene products should improve the effects of current first-line treatments and, in turn, reduce the chances of cancer recurrence. A recently completed siRNA (small interfering RNA) screen (where each of the 22,000 genes of the human genome was individually knocked out) identified several genes that, when silenced, increased cisplatin activity more than 5-fold. One such gene encodes for 3'-phosphoadenosine 5'-phosphosulfate (PAPS) synthase 1 (PAPSS1), an enzyme that makes the biologically usable form of sulfate PAPS from inorganic sulfate. We aim to characterize the role of PAPSS1 and other identified targets in NSCLC and to validate their therapeutic value in multiple NSCLC cell lines as well as in patient-derived NSCLC cells. Therapeutic siRNA will be used in conjunction with high content screening methods to evaluate cisplatin activity under gene silencing conditions. A virtual screen will also help identify existing drug candidates against promising targets to be used as part of a cisplatin chemotherapy cocktail in treating NSCLC. This program will allow us to better understand and ultimately target cytoprotective responses in cancer cells; responses that help cancer cells survive initial exposure to anticancer drugs.