Both claudin-3 and/or claudin-4 genes were found highly expressed in all primary ovarian cancer studied including five high grade serous papillary tumors and two high grade clear cell carcinomas when compared to normal ovarian epithelial cells (NOVA) as well as other normal cells or other gynecologic tumors (i.e., mean claudin-3 expression = 15,119 folds and mean claudin-4 expression = 1,800 folds, respectively, when compared to NOVA, Table 1, p < 0.05, and data not shown). The gene discussed is CLDN3; the disease is ovarian cancer.