Background: MicroRNAs (miRNAs or miR-) have been linked to factors associated with aggressive prostate cancer such as biochemical recurrence and metastasis. We investigated whether circulating miRNAs in plasma could be used as diagnostic biomarkers for more aggressive prostate cancer at prostate biopsy. Methods: Men, aged 40 years and above, newly diagnosed with prostate cancer were categorized into two risk groups, low-grade (Gleason score, 6 or 7 [3 + 4] and serum prostate-specific antigen [PSA], <20 ng/mL) and high-grade (Gleason score, ≥7 (4 + 3) and serum PSA, ≥20 ng/mL) prostate cancers. The limma R package was used to compare the expression of miRNAs in plasma between the two risk groups, adjusting for age. Results: There were 66 men, aged 46-86 years, included: 40 men with low-grade and 26 men with high-grade prostate cancers. There were lower expressions of miR-28, miR-100, miR-942, and miR-28-3p, and higher expressions of miR-708, miR-1298, miR-886-3p, miR-374, miR-376c, miR-202, miR-128a, and miR-185 in high-grade compared to low-grade prostate cancer cases at biopsy, after adjusting for age (P < 0.05). These differences were no longer statistically significant after adjusting the P values for multiple comparisons. Conclusion: There was no circulating miRNA associated with high-grade prostate cancer at biopsy after adjusting for age and multiple comparisons. Nevertheless, relationships between these circulating miRNAs and high-grade prostate cancer were observed, which suggest them as promising prostate cancer biomarkers. Further investigation in a larger cohort may provide insight into their diagnostic potential for aggressive prostate cancer.
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