[1080] ERG Protein Expression and PTEN Loss Are Uncommon in Prostate Cancer of Chinese Population

Tianying Xing, Xuelian Pei, Weigang Fang, Huiying He. Peking University, Health Science Center, Beijing, China

Background: In Western countries, gene fusions involving the ERG oncogene and deletions of the tumor suppressor gene PTEN are frequent alterations in prostate cancer (PCa). Recent reports demonstrated that TMPRSS2-ERG gene fusion correlated with the ethnicity. It was less common in Asian PCa of Japanese and Korean populations (16-28%) than Western PCa (40-50%), however the studies of TMPRSS2-ERG fusion status in Chinese PCa were very limited and contradictory. The ERG protein expression in Chinese PCa patients has not been evaluated to date. The objective of this study was to determine the frequency of ERG positive PCa by immunohistochemistry (IHC), PTEN deletion by IHC, and correlation with clinico-pathological parameters.
Design: IHC was performed on a single standard tissue section from the index tumor of 48 radical prostatectomies, enriched for relatively high grade (46% Gleason Score (GS) 7, 27% GS 8-9) and pathological stage (29% T3) tumors, utilizing the ERG mAb (EPR 3864;Epitomics,CA) and PTEN mAb (D4.3;CST,MA). Nuclear ERG expression was scored as positive or negative in a given tumor focus. Cytoplasmic PTEN staining was scored as normal (increased or equal staining compared to adjacent benign acini) or markedly decreased/absent dichotomously.
Results: Only 6% (3/48) of all the cases showed ERG positivity, with one case showing intratumoral ERG heterogeneity. The three ERG expressing cases were of GS ≤7. Two cases were pathological T2c and one was T3a. Seventeen percent (8/48) of cases showed PTEN loss, and of these, 25% (2/8) showed heterogeneity. In PTEN loss cases, 38% (3/8) had GS 8-9, however which was not significantly higher than 25% (10/40) in PTEN normal cases (P=0.08). PTEN loss did not correlate with GS or pathological stage. There was no association between ERG protein expression and PTEN loss (P>0.05 for all correlations).
Conclusions: Interestingly, ERG protein expression and PTEN loss are infrequent in Chinese PCa. Six percent of ERG positivity is even lower than that in PCa of other asian populations. Furthermore there was no association between ERG protein expression and PTEN loss. Our preliminary study suggests that there are different pathways of prostate carcinogenesis in Chinese population. Further studies of large specimen are underway.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 69, Tuesday Morning


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