A Multi-Histology Phase II Study of 5-Fluoro-2'-Deoxycytidine With Tetrahydrouridine (FdCyd + THU)

Background: * Two experimental drugs, FdCyd (also called 5-fluoro-2'-deoxcytidine), and THU (also called tetrahydrouridine), are undergoing trials to test their effectiveness in treating cancer that has not responded to standard therapies. FdCyd is thought to work by changing how genes work in cancer cells. THU does not have any anticancer effects on its own, but it helps keep the other drug, FdCyd, from being broken down by the body. * These drugs are being tested in several separate clinical trials. Objectives: * To determine if FdCyd and THU can work together to control tumor growth. * To evaluate the safety and tolerability of FdCyd and THU when given together. Eligibility: \- Individuals 18 years of age and older who have advanced non-small cell lung cancer, breast cancer, bladder cancer, or head and neck cancer that has progressed after receiving standard treatment or for which no effective therapy exists. Design: * The drugs are given over 28-day periods called cycles. FdCyd and THU are given through a vein for about 3 hours each day on days 1, 5 and 8, 12 of each cycle. * Clinical Center visits: FdCyd and THU will be given through a vein on days 1, 5 and 8, 12 of each cycle. During the Clinical Center visits, researchers will perform study tests and procedures to see how the study drugs are affecting the body. * Patients will undergo a number of tests and procedures during the treatment cycle, including physical examinations, blood and urine samples for standard tests, imaging studies (ultrasound, magnetic resonance imaging (MRI) or computed tomography (CT) scans) to evaluate tumor growth, and blood and urine samples to evaluate the amount of FdCyd and THU in the body and the body's response to the drugs. * Patients may continue to receive FdCyd and THU if their cancer does not grow, if they do not have too many side effects, and if they are willing to do so.