Diverse Roles and Targets of miRNA in the Pathogenesis of Testicular Germ Cell Tumour

Simple Summary Testicular germ cell tumour (TGCT) is the most common malignancy among young males in many parts of the world. Although it is highly remediable, treatments lead to long-term comorbidities, and therefore, it warrants a better prognosis. The presence of several risk loci in non-coding regions supports a functional role of miRNAs in TGCT development, and recent studies point to the emerging roles of miRNA and the complexity of miRNA-mediated gene regulation in TGCTs. miRNAs may act as oncogenes or tumour suppressors in TGCT by regulating targets involved in cell proliferation, apoptosis, and metastasis. Here, we summarise the gene regulation and function of miRNAs involved in TGCT pathogenesis. Testicular germ cell tumour (TGCT) is the most common cancer type among young adults in many parts of the world. Although the pathogenesis of TGCT is not well understood, the involvement of heritable components is evident, and the risk is polygenic. Genome-wide association studies have so far found 78 susceptibility loci for TGCT, and many of the loci are in non-coding regions indicating the involvement of non-coding RNAs in TGCT pathogenesis. MicroRNAs (miRNAs), a class of non-coding RNAs, have emerged as important gene regulators at the post-transcriptional level. They are crucial in controlling many cellular processes, such as proliferation, differentiation, and apoptosis, and an aberrant miRNA expression may contribute to the pathogenesis of several cancers, including TGCT. In support of this notion, several studies reported differential expression of miRNAs in TGCTs. We previously demonstrated that miRNAs were the most common group of small non-coding RNAs in TGCTs, and several functional studies of miRNAs in TGCTs suggest that they may act as either oncogene or tumour suppressors. Moreover, individual miRNA targets and downstream pathways in the context of TGCT development have been explored. In this review, we will focus on the diverse roles and targets of miRNAs in TGCT pathogenesis.