Development of a highly sensitive digital PCR assay to quantify long non-coding RNA in urine samples which exhibited great potential as an alternative diagnostic biomarker for prostate cancer.

Background: The diagnostic methods of prostate cancer (PCa) present major drawbacks in that serum prostate specific antigen (PSA) testing lacks specificity for PCa and prostate needle biopsy is a painful and highly invasive procedure for patients. Thus, new alternative screening methods which are specific and non-invasive both in the early detection and in the clinical definitive diagnosis of PCa are in urgent need. Long non-coding RNA has been shown to promote PCa cell proliferation and migration, and is significantly upregulated both at the cellular and tumor tissue level. Therefore, long non-coding RNA may be a new potential diagnostic biomarker for PCa.

Methods: In the present study, we successfully developed a highly sensitive digital PCR assay to detect long non-coding RNA in clinical urine samples. dPCR was carried out using Qx200 ddPCR EvaGreen Supermix (Bio-Rad) according to the manufacturer's instructions.

Results: Our results indicated that the digital PCR assay showed better linearity, repeatability, and reproducibility when compared with real-time quantitative PCR. In addition, we identified the normalized level and used the digital PCR assay to measure it in 100 clinical urine samples. Our study showed that the normalized level is a promising diagnostic biomarker for predicting and evaluating the malignancy of PCa.

Conclusions: Our findings presented a non-invasive liquid biopsy method to detect an alternative diagnostic parameter which can assist the diagnosis of PCa in clinical practice.