Researchers Develop Simple Prostate Cancer Assays for ERG

Researchers Develop Simple Prostate Cancer Assays for ERG

shutterstock_166437050In terms of early prostate cancer detection methods, more is better. Researchers at Pacific Northwest National Laboratory in Richland, Washington determined that the ETS-related gene (ERG) is a reliable biomarker for prostate cancer and can be detected using simple assays available in the clinic.

Standard procedure for detecting prostate cancer includes a serum analysis for prostate-specific antigen (PSA), a urine analysis for prostate cancer antigen 3 (PCA3), and a tissue analysis for alpha-methylacyl-coA racemase (AMACR), all of which are proteins that are over produced in cases of prostate cancer. However, other proteins are associated with prostate cancer, including the oncoprotein ERG. The researchers at Pacific Northwest National Laboratory noted that there are no commercially available serological-based assays for ERG and investigated how they could develop one in the study “Analytical Platform Evaluation for Quantification of ERG in Prostate Cancer Using Protein and mRNA Detection Methods,” published in Journal of Translational Medicine.

After considering a variety of technologies capable of analyzing proteins, the research team chose to develop multiple platforms that could detect both protein and the genetic material used to make proteins (mRNA). First, the team looked at the method of high-pressure high-resolution separations with intelligent selection and multiplexing (PRISM) selected reaction monitoring mass spectrometry (SRM-MS). Essentially, the value of PRISM-SRM is its ability to accurately quantify distinct peptides. Using this technology, the team obtained highly sensitive measurements of three ERG peptide units in prostate cancer cells with detection limits as low as 20 picograms. Importantly, the method was able to detect peptide levels in urine samples.

Next, the team used enzyme-linked immunosorbant assays (ELISAs) and western blots to detect whole ERG. ELISA had a comparable (to PRSIM-SRM) limit of detection at 30 picograms, while western blots had a higher limit of detection at 195 picograms. Both should be sufficient to detect ERG in cases of prostate cancer.

Finally, since protein extraction is not always possible, the team also looked at two modes of detecting mRNA. They found that one technique, quantitative real-time polymerase chain reaction (qRT-PCR), could detect mRNA in urine samples, but Nanodrop/Nanochip could not detect ERG using the experimental design executed by the research team.

“In summary the data presented here suggest that qRT-PCR and PRISM-SRM platforms are highly sensitive in detecting [ERG] transcripts and proteins, respectively,” wrote the authors. “[This provides] an opportunity for its use in the clinical setting for detection in prostate cancer patients, and define treatment strategies in accordance.”