Estrogen receptor‐binding fragment‐associated gene 9 expression and its clinical significance in human testicular cancer

OBJECTIVES: We previously demonstrated that estrogen receptor-binding fragment-associated gene 9 (EBAG9) is a tumor promoting factor in renal cell carcinoma (Ogushi T, Cancer Res. 2005; 65: 3700). Here, we evaluated EBAG9 expression and its clinical significance in normal and malignant human testicular tissues. METHODS: We investigated the expression of EBAG9 in 90 testicular specimens (28 benign testicular tissue and 62 testicular germ cell tumor samples) by immunohistochemistry using rabbit polyclonal anti-EBAG9 antibody. RESULTS: Positive immunostaining of EBAG9 in the cytoplasm was found in 32 (52%) cancerous lesions, whereas the immunoreactivity of EBAG9 was weak in benign testicular tissues. Serum lactate dehydrogenaze (LDH) level was significantly higher in EBAG9-positive cases (715.0 +/- 727.3) compared with the negative cases (221.4 +/- 126.8) (P = 0.0016). The EBAG9-positive cases among the patients with advanced clinical stage (Stage II and III) more frequently belonged to the intermediate or poor risk group in the International Germ Cell Consensus Prognostic Classification System (IGCCPCS), compared with the EBAG9-negative cases (P = 0.0012). CONCLUSIONS: These findings suggest that increased expression of EBAG9 may play a significant role in cancer progression and aggressiveness in testicular germ cell tumors.