Normally, Salmonella bacteria ingested in food or water can cause diarrhea or more severe illness. The bacteria in this study are altered genetically so they can be injected through a vein and circulate in the blood with less likelihood of causing side effects. It is believed that the bacteria will travel in the blood to the tumor and infect it. In studies of mice, tumor growth slowed in animals whose tumors were infected with VNP0009.