Downregulation of Chromosome 19 miRNA Cluster and the Tumor-Suppressive Role of miR-517a-3p in Choriocarcinoma.

Choriocarcinoma is a rare gynecologic malignancy. MicroRNAs, which are noncoding RNAs approximately 22 nucleotides in length, are known to regulate gene expression and play important roles in various cancers; however, their functions in choriocarcinoma remain largely unknown. This study aimed to identify disease-specific microRNAs involved in choriocarcinoma development. Eleven cases of choriocarcinoma and five cases of complete hydatidiform mole treated at our institution were analyzed. Total RNA was extracted from trophoblast cells in formalin-fixed, paraffin-embedded specimens using laser capture microdissection, and microRNA sequencing was performed. The analysis revealed that 87 microRNAs were significantly upregulated, whereas 28 were downregulated in choriocarcinoma compared to complete hydatidiform mole. Notably, 13 of the 28 downregulated microRNAs belonged to the chromosome 19 microRNA cluster. In vitro experiments demonstrated that overexpression of miR-517a-3p, a representative member of this cluster, significantly suppressed cell proliferation, migration, and invasion in JEG-3 and BeWo cell lines. Further transcriptome sequencing and computational analysis identified SRSF1 as a target gene of miR-517a-3p, which was validated by dual-luciferase reporter assays. Knockdown of SRSF1 also led to significant reductions in proliferation, migration, and invasion, supporting its functional relevance. Immunohistochemical analysis confirmed that SRSF1 protein was highly expressed in choriocarcinoma tissues compared to complete hydatidiform mole. These findings indicate that downregulation of the chromosome 19 microRNA cluster is a characteristic feature of choriocarcinoma and that miR-517a-3p functions as a tumor suppressor by directly regulating SRSF1 expression.