This study also examined the expression of claudin-3 and claudin-4 in the distal fallopian tube and in tumors from the same patients in six cases of serous ovarian cancer, and high expression of these claudins in both sites was observed in all six patients, suggesting that claudin-3 and claudin-4 are normally expressed in the fallopian tube, and downregulation of claudin-3 or claudin-4 in ovarian cancer promotes tumor growth and metastatic behavior in vivo. The gene discussed is CLDN3; the disease is ovarian carcinoma.