Because peptides are promising molecules to deliver radionuclides or chemotherapeutic drugs into tumors, we hypothesized that using the C- CPE290-319 peptide to target ovarian cancer cells based on their high levels of claudin-3 and -4 may represents a novel, potentially highly effective diagnostic and therapeutic approach to identify and treat chemotherapy-resistant ovarian cancer. This evidence concerns the gene CLDN3 and ovarian cancer.