Tumor resistance to anti-cancer drugs is a major problem in cancer treatment. Studies have found that a protein (P-glycoprotein) on some cancer cells pumps chemotherapy drugs out of the cells, reducing treatment effectiveness. In laboratory tests, an experimental drug called XR9576, has blocked pumping by this protein. It is being used in this study to try to increase the amount of the anti-cancer drug vinorelbine, in cancer cells. Vinorelbine has been shown in several clinical trials to be effective against some advanced cancers, including breast, lung and ovarian, and is one of the drugs pumped out of tumor cells by P-glycoprotein.