[876] ERG Protein Expression and ERG Gene Rearrangement in Prostate Cancers of Different Zonal Origin

Charles C Guo, Michael P Mikulasovich, Michael T Deavers, Patricia Troncoso, Bogdan A Czerniak. University of Texas MD Anderson Cancer Center, Houston, TX

Background: Recent studies have demonstrated that most prostate cancers carry the TMPRSS2-ERG fusion gene. To evaluate the utility of ERG immunohistochemistry in the analysis of this gene fusion, we compared ERG protein expression with ERG gene rearrangement in prostate cancers of different zonal origin.
Design: We selected 22 radical prostatectomy specimens with multifocal prostatic adenocarcinoma from our pathology files. The ERG protein expression was evaluated by immunohistochemistry (IHC) using the ERG (9 FY) antibody (Biocare Medical, Concord, CA), and the ERG gene rearrangement was evaluated by fluorescence in situ hybridization (FISH) using ERG break-apart probes.
Results: The mean age of patients was 58.5 years (range 46-71 years). Two separate tumor foci in each RP specimen, one in the peripheral zone (PZ) and one in the transition zone (TZ), were analyzed. The Gleason scores of the PZ tumor foci ranged from 6(3+3) to 7 (4+3) and the tumor volume ranged from 0.3 to 3.0 cm3 (mean, 1.4 cm3). The Gleason scores of the TZ tumor foci ranged from 5(3+2) to 7 (4+3) and the tumor volume ranged from 0.5 to 12.8 cm3 (mean, 4.1 cm3). On FISH analysis, 11 of the 22 PZ tumor foci showed rearrangement of the ERG gene, including deletion (n=8) and translocation (n=3), but none of the TZ foci had rearrangement. On IHC analysis, all 11 PZ tumor foci with the ERG rearrangement showed positive immunoreactivity for ERG in nuclei, while all tumor foci without the ERG rearrangement (n=33) showed negative immunoreactivity.
Conclusions: Our study demonstrates an excellent correlation between ERG protein expression and ERG gene rearrangement in prostatic adenocarcinoma, suggesting that the ERG IHC may be an effective tool to evaluate the TMPRSS2-ERG gene fusion in prostate cancer. Although we did not find ERG protein expression in the TZ tumor foci, the number of cases in our study was small. Other studies have reported that prostate cancers of TZ origin may also carry the ERG gene rearrangement but the frequency is lower than that in prostate cancers of PZ origin.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 159, Monday Afternoon

 

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