The miR-509-5p inhibited cell proliferation, invasion, and migration via targeting the gene of MDM2 in testicular germ cell tumor,[36] pancreatic cancer,[37] cervical cancer,[41] and hepatocellular carcinoma.[41] A recent study reported that miR-509-5p acted as an antioncogene in breast cancer via targeting SOD2.[42] YWHAG and FOXM1 were identified as the target genes for miR-509-5p in nonsmall cell lung cancer.[39,43] The above studies provide the potential targets for miR-509-5p in OS and further careful investigation is necessary. The gene discussed is MDM2; the disease is testicular germ cell tumor.