Purpose: The aim of this study was to investigate the microRNA (miRNA) profile in prostate carcinoma as biomarkers to identify high-risk prostate cancer patients who may benefit from post-prostatectomy radiation therapy using global miRNA profiling. Method: Tumor from Formalin-Fixed Paraffin-Embedded (FFPE) tissues were obtained from 9 radical prostatectomy specimens resected for high-risk prostate cancer, to perform a pilot study using the Nanostring miRNA platform from isolated RNA. An optimized protocol utilizing the Ambion RecoverAll digestion buffer and the Qiagen miRNeasy FFPE kit was used to isolate total RNA. Each prostatectomy specimen was marked by a genitourinary pathologist and 1 mm cores of enriched areas of tumor or normal epithelial or stromal tissue were obtained. To analyze global miRNA expression, the Nanostring nCounter human miRNA Expression Assay Kit was used. The data was further analyzed in collaboration with The Ohio State University Center for Biostatistics. Results: The expression of miRNA in prostate tumor samples was compared to normal epithelium. It showed that seven miRNAs (miR-375, miR-18a, miR-25, miR-183, miR-641, miR-15b, miR-548a-3p) that were >1.5-fold upregulated and 4 miRNAs (miR-660, miR-1915, miR-200b, miR-205) 3 and/or Gleason score ≥ 8) and five miRNAs (up-regulated: miR-10b, miR-205; down-regulated: miR-574-5p, miR-30c, miR-499-5p) with pathological tumor stage 2 and 3. Conclusion: Our results suggest great potential for the use of miRNA profiling as a novel diagnostic and prognostic biomarker in defining the signatures of prostate cancer at different stages. We are currently completing the RNA isolation and downstream analyses in correlation with clinical data for 80 additional high-risk prostate cancer cases from the University hospital of Freiburg, Germany. Citation Format: Petra Stegmaier, Simon Kirste, Xiaokui M. Mo, Debra L. Zynger, Arnab Chakravarti, Erica Hlavin Bell. Molecular markers of prostate cancer: Investigation of microRNA profiles as a marker in patients with high-risk prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3. doi:10.1158/1538-7445.AM2013-3