Intragenic expression profile in tissue and plasma for the detection of TMPRSS2 rearrangements associated with prostate cancer

5162 Background: TMPRSS2 gene rearrangements have been reported in 40%-85% of prostate cancer (PCa) patients and have not been found in normal individuals or those with benign prostate hyperplasia (BPH). However, multiple partner genes, including ETS transcription genes, and breakpoints have been reported. We developed an assay based on TMPRSS2 5′ and 3′ intragenic differential expression (IDE) to potentially serve as a diagnostic or prognostic marker for PCa. Methods: We analyzed TMPRSS2 in FFPE tissue from 20 patients (9 PCa and 11 BPH) and plasma from 42 patients (32 PCa and 10 BPH). IDE was expressed as a ratio of 3′:5′ transcript levels which were determined by real-time RT-PCR using distinct primer/probe sets. A normal 3′:5′ ratio (≥30) was established by comparing nonmalignant cells to tumor cells from FFPE tissue. This cutoff was subsequently used to identify abnormal ratios in plasma specimens. Results: In FFPE tissue, 100% of PCa samples had a 3′:5′ratio <30 and 91% of BPH samples were ≥30 ( Table ). RNA in 48% of plasma samples passed our QC criteria for acceptability. The 3′:5′ ratios were <30 in 47% and ≥30 in 6.7% PCa plasma. Conclusions: By measuring IDE, we are not limited to screening for known TMPRSS2/ETS gene translocations. In tissue, this approach enabled us to identify patients with PCa vs. BPH with high specificity. Although work is needed to improve plasma RNA quality, IDE of plasma TMPRSS2 may be a useful non-invasive diagnostic or prognostic tool. [Table: see text] No significant financial relationships to disclose.