sentence1: In many tumors, there is either overexpression of so-called oncogenic miRNAs (e.g., miR-155, miR-17−5p and miR-21)  or downregulation of tumor suppressor miRNAs (e.g., miR-34, miR-15a, miR-16−1 and let-7)
sentence2: Of note, miR-373 had been previously identified as a potential oncogene (together with miR-372) in testicular germ-cell tumors, although it has been proposed that the prometastatic and the oncogenic properties of this miRNA are due to the regulation of different genes (CD44 and LATS2, respectively)