We have produced mice that do not make mesothelin and are comparing them with normal mice to determine if various types of cancer will grow in the peritoneal cavity of these mice, where mesothelin is present on the mesothelial cells lining the peritoneal cavity of the normal mice. We have crossed these mice with immuno-deficient mice to make meso-/-, nu/nu mice to allow human cancer cells to grow in the peritoneal cavity of the mice. We plan to implant various types of human cancers into the peritoneal cavity of these mice and determine if mesothelin expression correlates with the behavior of the tumor. If there is a correlation we will inject soluble mesothelin to determine if it will affect tumor growth.