Supplementary Material for: MicroRNA miR-371a-3p - A Novel Serum Biomarker of Testicular Germ Cell Tumors: Evidence for Specificity from Measurements in Testicular Vein Blood and in Neoplastic Hydrocele Fluid

<br><strong><em>Background:</em></strong> microRNAs (miRs)-371-3 are suggested to be novel biomarkers of germ cell tumors (GCTs), but their specificity is unresolved. We aimed at clarifying the origin of miR 371a-3p by measuring this miR in peripheral vein blood, and in fluids present in the vicinity of GCTs. <b><i>Methods:</i></b> miR-371a-3p levels were measured by quantitative PCR in 9 tumor surrounding hydroceles and in cubital vein blood (CVB) and testicular vein blood (TVB) of 64 GCT patients, 51 with clinical stage (CS) 1, 13 with CS2-3. Thirty three CS1 cases had also postoperative CVB measurement. TVB miR levels were compared with those of CVB. Associations with clinical factors were analyzed statistically. <b><i>Results:</i></b> TVB miR levels were 294-fold, 80-fold and 4.6-fold higher than those in CVB of CS1 patients, CS2-3 patients and controls, respectively. Neoplastic hydrocele fluid comprised of very high miR levels. In CS1, miR levels dropped to normal postoperatively. Statistically, CVB miR levels are significantly associated with tumor size (p = 0.0211) and testis length (p = 0.0493). TVB miR levels are associated with testis length (p = 0.0129). <b><i>Conclusions:</i></b> This study provides evidence for the origin of circulating miR 371a-3p molecules from GCT cells. miR-371a-3p represents a specific serum biomarker for germ cell cancer.