[771] Prostate Cancer of Transitional Zone Lacks TMPRSS2-ERG Gene Fusion

CC Guo, G Zuo, D Cao, C Soto, P Troncoso, BA Czerniak. University of Texas MD Anderson Cancer Center, Houston, TX

Background: Recent studies have revealed that the majority of prostate cancers have a unique chromosomal rearrangement leading to the TMPRSS2-ERG gene fusion. Whereas most prostate cancers develop in the peripheral zone (PZ), some arise in the transitional zone (TZ). The role of TMPRSS2-ERG gene fusion in zonal origin of prostate cancer remains unclear. Therefore, we studied TMPRSS2-ERG gene fusion in prostate cancer of different zonal origin.
Design: Radical prostatectomy specimens were obtained from 30 patients who received treatment of clinically localized prostate cancer at our institution. Every specimen contained at least two foci of the tumor, one in the PZ and the other in the TZ. The PZ and TZ tumor foci were separated by at least 4.5 mm. The TMPRSS2-ERG gene fusion was evaluated in each tumor focus by fluorescence in situ hybridization (FISH) using the ERG break-apart probes, and was related to their pathological features including zonal distribution.
Results: The average age of the patients was 58.7 years (range, 46.0-71.0 years). None of the patients had received neoadjuvant hormonal or radiation therapy. The average number of tumor foci in the specimens was 3.3 (range, 2.0-5.0). Two separate tumor foci in each specimen, one in the PZ and the other in the TZ, were selected for the analysis. The PZ tumor foci selected for the analysis had a mean Gleason score of 6.8 (range, 6.0-7.0) and a mean tumor volume of 1.2 cm³ (range, 0.1-4.6 cm³). The selected TZ tumor foci had a mean Gleason score of 6.7 (range, 5.0-8.0) and a mean tumor volume of 4.0 cm³ (range, 0.5-9.0 cm³). In all cases, the TZ tumors had a normal FISH signal pattern without evidence of rearrangement in the ERG gene. In 13 cases (43.3%), the PZ tumors demonstrated rearrangements in the ERG gene. In 10 cases, the rearrangement was associated with a deletion of the 5' end of the ERG gene. This deletion was not present in the other 3 cases.
Conclusions: The TZ prostate cancer was negative for rearrangements in the ERG gene, implicating the absence of TMPRSS2-ERG gene fusion in the prostate cancer arising in the TZ. In contrast, PZ prostate cancers frequently exhibited rearrangements in the ERG gene, suggesting that the TMPRSS2-ERG fusion play a role in the pathogenesis of prostate cancer arising in the PZ.
Category: Genitourinary (including renal tumors)

Monday, March 9, 2009 1:00 PM

Poster Session II # 107, Monday Afternoon