Noninvasive Detection of TMPRSS2:ERG Fusion Transcripts in the Urine of Men with Prostate Cancer

Abstract

We recently reported the identification of recurrent gene fusions in the majority of prostate cancers involving the 5' untranslated region of the androgen-regulated gene TMPRSS2 and the ETS family members ERG, ETV1, and ETV4. Here we report the noninvasive detection of these gene fusions in the urine of patients with clinically localized prostate cancer. By quantitative polymerase chain reaction, we assessed the expression of ERG and TMPRSS2:ERG transcripts in urine samples obtained after prostatic massage from 19 patients (11 prebiopsy and 8 pre-radical prostatectomy) with prostate cancer. We observed a strong concordance between ERG overexpression and TMPRSS2:ERG expression, with 8 of 19 (42%) patients having detectable TMPRSS2:ERG transcripts in their urine. Importantly, by fluorescence in situ hybridization, we confirmed the presence or the absence of TMPRSS2:ERG gene fusions in matched prostate cancer tissue samples from three of three patients with fusion transcripts in their urine and from two of two patients without fusion transcripts in their urine. These results demonstrate that TMPRSS2:ERG gene fusions can be detected in the urine of patients with prostate cancer and support larger studies on prospective cohorts for noninvasive detection of prostate cancer.

ETS rearrangements in prostate cancer

“…Several studies to date have demonstrated the detection of the TMPRSS2:ERG fusion transcripts in urine. 44,45,67 These studies, and other unpublished reports, demonstrate a high specificity. Unlike PSA, which can be elevated in benign conditions as well as cancer, the presence of TMPRSS2:ERG transcripts has only been reported in neoplastic cells.…”

“…This has important clinical implications, as the TMPRSS2:ERG transcript can be detected in urine and represents a highly specific prostate cancer biomarker. [44][45][46] The common ETS gene fusions are widely believed to have an important oncogenic role, but that ERG or ETV1 overexpression alone is not sufficient to lead to prostate cancer. There is now mounting molecular data for an important concomitant role of TMPRSS2:ERG and the pten/PI3K/ATK pathway activation in prostate cancer oncogenesis.…”

Urine markers in monitoring for prostate cancer

“…69 Urine RNA was analyzed by qRT-PCR after preamplification (whole transcriptome amplification) and then break-apart fluorescent in situ hybridization (FISH) was used to validate the presence or absence of the TMPRSS2/ERG gene rearrangement in the CaP tissue. Indeed, patients with high levels of ERG and detectable levels of TMPRSS2/ERG in their urine were positive for ERG rearrangement.…”

“…Current biopsy strategies may miss heterogenous tumor foci, and urine-based assay would have a great advantage because the cells from multiple cancerous foci of whole prostate could be released and collected. 69 Laxman et al 12 reported that a multiplex panel of urine transcripts outperforms PCA3 transcript and serum PSA alone in detecting CaP. Expression of seven putative prostate cancer biomarkers was measured (PCA3, PSA, GOLPH2, SPINK1, AMACR, TMPRSS2/ERG, TFF3) by qRT-PCR in urine samples.…”

“…For example, the most commonly used FISH 50,57,61 has relatively low resolution and, therefore, cannot accurately determine different fusion variants in highly heterogeneous samples with small percentages of tumor cells. Quantitative RT-PCR and sequencing are relatively easy to perform; 56,59,69,76 however, multiple sets of primers/probes are required for assessing multiple potential fusion variants. Array CGH (comparative genome hybridization) has a high resolution but often fails when there is normal cell contamination.…”