ERG overexpression plus SLC45A3 (prostein) and PTEN expression loss: Strong association of the triple hit phenotype with an aggressive pathway of prostate cancer progression

// Silvia Hernández-Llodrà 1, * , Nuria Juanpere 1, 2, * , Silvia de Muga 1 , Marta Lorenzo 2 , Joan Gil 1 , Alba Font-Tello 3 , Laia Agell 1 , Raquel Albero-González 2 , Laura Segalés 1 , José Merino 4 , Laia Serrano 2 , Lluís Fumadó 5 , Lluís Cecchini 5 and Josep Lloreta Trull 1, 2 1 Department of Health and Experimental Sciences, Universitat Pompeu Fabra, Barcelona, Spain 2 Department of Pathology, Hospital del Mar-Parc de Salut Mar-IMIM, Barcelona, Spain 3 Dana Farber Cancer Institute, Boston, MA, USA 4 Fundación Jiménez Díaz, Madrid, Spain 5 Department of Urology, Hospital del Mar-Parc de Salut Mar-IMIM, Barcelona, Spain * These authors have contributed equally to this work Correspondence to: Silvia Hernández-Llodrà, email: silvia.hernandez@upf.edu Josep Lloreta Trull, email: jlloreta@parcdesalutmar.cat Keywords: ERG, SLC45A3, PTEN, prostate cancer, progression Received: August 10, 2016      Accepted: May 15, 2017      Published: May 26, 2017 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.