Twist is inversely associated with claudins in germ cell tumors of the testis.

We investigated the expression of claudins 1, 3-7 and transcriptional factor twist in a set of testicular germ cell tumors. The material consisted of 17 seminomas, 13 teratomas, 9 teratocarcinomas, 20 embryonal carcinomas and 9 mixed germ cell tumors. They were immunostained with antibodies to claudins 1, 3-7 and twist. As expected, all claudins were variably present in germ cell tumors with epithelial elements or differentiation, but the intensity of expression varied depending on the claudin type. Mesenchymal elements in teratomatous tumors remained negative for claudins. Expression of different claudins was less intense and inconsistent in other types of germ cell tumors. Choriocarcinomatous elements in germ cell tumors expressed relatively strongly claudin 4 and weaker positivity for claudins 5-7, while claudins 1 and 3 were negative. Seminomas showed expression only for claudins 5 and 7. The transcriptional factor twist was most strongly expressed in seminoma followed by embryonal carcinoma. Twist expression was inversely associated with several claudins (claudins 1, 3, 4 and 6). Germ cell tumors vary in their expression of claudins 1-7. Twist expression was inversely associated with several claudins, suggesting that it takes part in the downregulation of claudins in testicular tumors.