*4.10. Ethical Approval and Consent to Participate*

All patients gave written informed consent for the collection of biomaterials. The study was approved by the Ethics Committee at the Medical Faculty of the Rheinische Friedrich-Wilhelms-University Bonn (number: 273/18; 013/20).

#### **5. Conclusions**

In total, our study could show for the first time that DONSON expression is strongly enhanced in phenotypically aggressive PCa and advanced metastatic samples and represents an interesting and robust prognostic biomarker. Further, DONSON could play an important role in the PCa progression and metastatic process supported by functional in vitro analyses.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-6694/12/11/3439/s1, Figure S1: DONSON overexpression is associated with an unfavorable OS in the PCa TCGA cohort, Figure S2: A, Immunocytochemical staining of DONSON in PC-3 control cells (NegA) compared to DONSON-knockdown. Images depicted in 10x objective magnification. B. The DONSON knockdown efficacy of the respective stained cells was confirmed via qPCR, Figure S3: Uncropped Western Blot images, Table S1: Clinical-pathological characteristics of the Prostate Cancer TCGA Cohort, Table S2: Clinical-pathological characteristics of the Bonn Prostate Cancer Tissue Microarray.

**Author Contributions:** Conceptualization, N.K., A.A., and J.E.; methodology, N.K., M.v.D., J.S., D.S., A.S., A.A., and J.E.; validation, N.K., M.v.D., J.S., D.S., A.S., G.K., M.M., M.H., M.R., A.A., and J.E.; investigation, N.K., M.v.D., and J.S.; resources, G.K., M.H., M.R., A.A., and J.E.; writing, N.K., M.v.D., A.A., and J.E.; review and editing, J.S., D.S., A.S., G.K., M.M., M.H., and M.R.; supervision, A.A. and J.E. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by a Ferdinand Eisenberger grant of the Deutsche Gesellschaft für Urologie (German society of Urology), grant ID KIN1/FE-19 (NK).

**Acknowledgments:** The tissue samples were collected within the framework of the Biobank of the Center for Integrated Oncology Cologne Bonn at the University Hospital Bonn.

**Conflicts of Interest:** The authors declare no conflict of interest.
