Therefore, we hypothesize that chemoresistance against gemcitabine is due to combination of inherent and acquired resistance. Inherent resistance is due to hypoxia-induced NFκB activation and acquired resistance is due to gemcitabine-induced NFκB activation. Accordingly, we are determining whether NFkB inhibition by treatment with thiol donors enhances killing of tumor cells by gemcitabine. Gemcitabine seems to work as “a double sword”: it induces apoptosis acting as an antimetabolite, but on the other hand it activates NFκB tipping the balance towards survival. NAC also seems to work on two fronts, first by inhibiting NFκB activation arising from hypoxic regions of tumors and second by blocking gemcitabine-activated NFκB in hypoxic and normoxic regions of tumors. Inhibition of NFκB decreases expression of survival genes and sensitize cells to gemcitabine-induced killing. Our goal is to develop non-toxic strategies how to overcome the gemcitabine resistance, which should be useful for optimizing therapeutic responses. This project utilizes techniques of molecular and cell biology, biochemical assays, confocal microscopy, and proteomics in cell culture and animal models.