The present invention provides compositions and methods useful for diagnosing, treating, and preventing cancer, particularly ovarian cancer and uterine cancer, based on the discovery that the oocyte specific protein, SAS1R (Sperm Acrosomal SLL-P1 Receptor), which is a sperm protein receptor, is also expressed in various cancers, including ovarian cancer and uterine cancer. Six SAS1R variants have been previously identified, and they are encompassed by the invention. The present invention further provides antibodies useful for targeting SAS1R expressing cells and for killing such cells.
