The invention discloses high levels of receptors for Clostridium perfringens enterotoxin (CPE) have been found in ovarian cancer and uterine cancer tissue samples. In addition, successful in vivo treatment of a mouse model of ovarian cancer with intraperitoneal injection of CPE is disclosed. High levels of Ep-CAM protein is also disclosed in ovarian cancer tissue samples. Thus, the invention provides a method of treating ovarian cancer and uterine cancer by administering CPE. The invention also provides a method of treating cancer in a mammal involving intraperitoneal administration of CPE, where at least some cancerous cells are located in or adjacent to the peritoneal cavity of the mammal. The invention also provides a method of treating ovarian cancer involving administering an anti-Ep-CAM antibody. The invention also provides a method of treating cancers expressing claudin-3 or claudin-4 by administering an antibody against claudin-3 and/or an antibody against claudin-4. The invention also provides a method of protecting a mammal from CPE toxicity involving administering a protective agent that binds to claudin-3 and/or claudin-4 and inhibits CPE binding to claudin-3 and/or claudin-4.