Ubiquitin proteasome system and autophagy associated proteins in human testicular tumors

Ubiquitin proteasome sytem (UPS) and autophagy govern protein quality control by degradation and clearance of damaged proteins. Many proteins working in these pathways such as p97/VCP, Ubiquitin (Ub), Jab1/CSN5, p62, LC3B and Beclin 1 are known to be essential for different pathological conditions, especially in cancer, but their expression in human testicular tumors has not been characterized yet. In the present study, we aimed to investigate the expression of UPS (p97/VCP, Ubiquitin, Jab1/CSN5) and autophagic (p62, LC3B, Beclin 1) proteins in human testicular tumors and cancer adjacent normal testicular tissues. We used an immunohistochemical staining technique. 120 cases of testicular germ and non-germ cell tumors, which are 42 seminomas, 31 embryonal carcinomas, 11 yolk sac tumors, 25 intratubular germ cell neoplasms, 6 Leydig cell tumors, 5 Sertoli cell tumors, were collected and evaluated on tissue microarray. For the first time, the expression of p97/VCP, Ub, Jab1/CSN5, p62, LC3B and Beclin 1 in different type of human testicular tumors has been confirmed. We found that p97/VCP, Ub and Jab1/CSN5 were frequently expressed at higher levels in testicular tumours. In contrast to UPS markers, p62, LC3B and Beclin 1 showed significantly diminished expressions in testicular tumors. Accordingly, a negative correlation between p97/VCP and autophagic markers (p62 and LC3B) was found, suggesting a relationship between UPS and autophagy in different type of testicular tumors. The current results displayed elevated level of p97/VCP, Ub and Jab1/CSN5 expressions in contrast to the diminished expression of p62, LC3B and Beclin 1 in human testicular tumors, thereby supporting a correlation between p97/VCP and autophagic markers in testicular tumors.