Monoclonal antibodies that bind specifically to Claudin 3 expressed on cell surface are provided. The antibodies of the present invention are useful for diagnosis of cancers that have enhanced expression of Claudin 3, such as ovarian cancer, prostate cancer, breast cancer, uterine cancer, liver cancer, lung cancer, pancreatic cancer, stomach cancer, bladder cancer, and colon cancer. The present invention provides monoclonal antibodies showing cytotoxic effects against cells of these cancers. Methods for inducing cell injury in Claudin 3-expressing cells and methods for suppressing proliferation of Claudin 3-expressing cells by contacting Claudin 3-expressing cells with a Claudin 3-binding antibody are disclosed. The present application also discloses methods for diagnosis or treatment of cancers.
