PCA3 and TMPRSS2-ERG gene fusions as diagnostic biomarkers for prostate cancer

The incidence of prostate cancer （PCa） is rising steadily among males in many countries. Serum prostate-specific antigen （PSA） is widely applied to clinical diagnosis and screening of PCa. However, the so-called grey area of PSA levels 4.0-10.0 ng/mL has a low specificity of 25-40% resulting in a high rate of negative biopsy and overtreatment. So in order to treat PCa patients in early stage, there is an urgent need for new biomarkers in PCa diagnosis. The PCA3 gene, a non-coding RNA （ncRNA） that is highly expressed in prostate cancer （PCa） cells, has been identified as a molecular biomarkers to detect PCa, of which PCA3 has already under clinical application. PCA3 is strongly overexpressed in malignant prostate tissue compared to benign or normal adjacent one. Newly, PCA3 is considered to be a promising biomarker in clinical diagnosis and targeted therapy. The diagnostic significance of PCA3, however, is awaiting further researches. Moreover, it has been demonstrated recently that TMPRSS2-ERG gene fusion is identified as the predominant genetic change in patients diagnosed with PCa. Recent study revealed that combination of the PC43 and TMPRSS2-ERG gene fusion test optimizes PCa detection compared with that of single biomarker, which would lead to a considerable reduction of the number of prostate biopsies. In this review, we focused on the potential use of PCA3 and TMPRSS2-ERG gene fusion detection in the diagnosis of PCa.

Detection of TMPRSS2：ERG fusion gene in circulating prostate cancer cells

Aim： To investigate the existence of TMPRSS2：ERG fusion gene in circulating tumor cells （CTC） from prostate cancer patients and its potential in monitoring tumor metastasis. Methods- We analyzed the frequency of TMPRSS2： ERG and TMPRSS2：ETV1 transcripts in 27 prostate cancer biopsies from prostatectomies, and TMPRSS2：ERG transcripts in CTC isolated from 15 patients with advanced androgen independent disease using reverse transcription polymerase chain reaction （RT-PCR）. Fluorescence in situ hybridization （FISH） was applied to analyze the genomic truncation of ERG, which is the result of TMPRSS2：ERG fusion in 10 of the 15 CTC samples. Results： TMPRSS2： ERG transcripts were found in 44% of our samples, but we did not detect expression of TMPRSS2：ETV1. Using FISH analysis we detected chromosomal rearrangements affecting the ERG gene in 6 of 10 CTC samples, including 1 case with associated TMPRSS2：ERG fusion at the primary site. However, TMPRSS2：ERG transcripts were not detected in any of the 15 CTC samples, including the 10 cases analyzed by FISH. Conclusion： Although further study is required to address the association between TMPRSS2：ERG fusion and prostate cancer metastasis, detection of genomic truncation of the ERG gene by FISH analysis could be useful for monitoring the appearance of CTC and the potential for prostate cancer metastasis.

ETS rearrangements in prostate cancer

Prostate cancer is a clinically and molecularly heterogeneous disease. Understanding the biologic underpinning of prostate cancer is necessary to best determine how biology is associated with the risk of disease progression and how this understanding might provide insight into the development of novel therapeutic approaches. The focus of this review is on the recently identified common ETSand non-ETS gene rearrangements in prostate cancer. Although multiple molecular alterations have been detected in prostate cancer, a basic understanding of gene fusion prostate cancer should help explain the clinical and biologic diversity, providing a rationale for a molecular subclassification of the disease.