Identification of Tumor-Suppressive miR-139-3p- Regulated Genes: TRIP13 as a Therapeutic Target in Lung Adenocarcinoma.

Simple Summary: Based on the miRNA expression signature of LUAD, we focused on miR-139-3p, a passenger strand, and clarified its tumor-suppressive function in lung adenocarcinoma (LUAD) cells. A total of the 21 target genes (KRT80, CENPM, SPC24, ORC1, MYEOV, TRIP13, GPX8, ARHGEF39, MKI67, KIF18B, CHAF1B, CP, GPRIN1, UCK2, CHEK1, HELLS, CTSV, FAM111B, SLC16A3, MELK, and CENPF) were identified as miR-139-3p targets in LUAD, and the expression of these genes was as independent prognostic factor for patient survival. Moreover, inhibition of TRIP13 using a specific inhibitor (DCZ0415) enhanced the sensitivity of LUAD cells to anticancer drugs. Analyses of our microRNA (miRNA) expression signature combined with The Cancer Genome Atlas (TCGA) data revealed that both strands of pre-miR-139 (miR-139-5p, the guide strand, and miR-139-3p, the passenger strand) are significantly downregulated in lung adenocarcinoma (LUAD) clinical specimens. Functional analyses of LUAD cells ectopically expressing miR-139-3p showed significant suppression of their aggressiveness (e.g., cancer cell proliferation, migration, and invasion). The involvement of the passenger strand, miR-139-3p, in LUAD pathogenesis, is an interesting finding contributing to the elucidation of unknown molecular networks in LUAD. Of 1108 genes identified as miR-139-3p targets in LUAD cells, 21 were significantly upregulated in LUAD tissues according to TCGA analysis, and their high expression negatively affected the prognosis of LUAD patients. We focused on thyroid hormone receptor interactor 13 (TRIP13) and investigated its cancer-promoting functions in LUAD cells. Luciferase assays showed that miR-139-3p directly regulated TRIP13. siRNA-mediated TRIP13 knockdown and TRIP13 inhibition by a specific inhibitor (DCZ0415) attenuated the malignant transformation of LUAD cells. Interestingly, when used in combination with anticancer drugs (cisplatin and carboplatin), DCZ0415 exerted synergistic effects on cell proliferation suppression. Identifying the molecular pathways regulated by tumor-suppressive miRNAs (including passenger strands) may aid in the discovery of diagnostic markers and therapeutic targets for LUAD. [ABSTRACT FROM AUTHOR]

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