Abstract
TMPRSS2 and SLC45A3 rearrangements may coexist in the same tumor. ERG rearrangements and PTEN loss are concomitant events in prostate cancer (PrCa), and can cooperate in progression. We have reported that mRNA expression of TMPRSS2-ERG and SLC45A3-ERG rearrangements plus PTEN loss define an aggressive tumor subset. The aim of this study has been to validate these results by immunohistochemistry in a large cohort of tumors. ERG, SLC45A3 and PTEN immunostaining and their association with pathological features and PSA progression-free survival were analyzed in 220 PrCa (PSMAR-Biobank, Barcelona, Spain). ERG protein expression was found in 46.8% and SLC45A3 and PTEN loss in 30% and 34% tumors, respectively. Single ERG positive immunostaining was associated with GS = 6 tumors (p = 0.016), double ERG+/PTEN loss with GS = 7 (p = 0.008) and Grade Group 2 (GG) or GG3 cases (p = 0.042), ERG+/SLC45A3 loss/PTEN loss (“triple hit”) with GS ≥ 8 (p < 0.0001) and GG4 or GG5 tumors (p = 0.0003). None of GS = 6 nor = GG1 cases showed this combination. In the GS ≥ 8 group, ERG+ (p = 0.002), PTEN loss (p = 0.009) and “triple hit” (p = 0.003) were associated with Gleason pattern 3 component, and single SLC45A3 loss (p = 0.036) with GS ≥ 8 without pattern 3. The number of aberrant events and the triple hit were strongly associated with shorter PSA progression-free survival. In GS = 6 PrCa, single ERG+ was also associated with progression. ERG+ identifies a distinct pathway of PrCa. Additional assessment of PTEN and SLC45A3 adds relevant prognostic information. The triple hit phenotype (ERG+/SLC45A3 loss/PTEN loss) is associated with progression and could be used for patient stratification, treatment and follow-up.
Highlights
ERG overexpression resulting from the rearrangement between the TMPRSS2 promoter and the coding regions of the ERG gene has been identified as the most common alteration in prostate cancer (PrCa), accounting for more than 90% of the TMPRSS2-ETS family rearrangements [1,2,3]
We have reported that mRNA expression of TMPRSS2-ERG and SLC45A3-ERG rearrangements plus PTEN loss define an aggressive tumor subset
In Gleason score (GS) 6 biopsies, PTEN loss has been proposed as a potential predictor of upgrading at radical prostatectomy [31, 32]
Summary
ERG overexpression resulting from the rearrangement between the TMPRSS2 promoter and the coding regions of the ERG gene has been identified as the most common alteration in prostate cancer (PrCa), accounting for more than 90% of the TMPRSS2-ETS family rearrangements [1,2,3]. Double rearrangements of ERG with TMPRSS2 and SLC45A3 or NDRG1, well known androgeninduced genes (8), have been found to coexist in the same tumor in a subset of PrCa cases [9,10,11]. The association of PTEN loss with high grade prostate tumors is well documented [21,22,23,24] Both ERG rearrangements and loss of PTEN are frequent and concomitant events in PrCa that can cooperate in progression [11, 14, 20, 25,26,27,28]. In Gleason score (GS) 6 biopsies, PTEN loss has been proposed as a potential predictor of upgrading at radical prostatectomy [31, 32]
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