Exploring the regulatory role of FBXL19‐AS1 in triple‐negative breast cancer through the miR‐378a‐3p/OTUB2 axis

Abstract The regulatory potential of long noncoding RNA (lncRNA) FBXL19‐AS1 has been highlighted in various cancers, but its effect on triple‐negative breast cancer (TNBC) remains unclear. Here, we aimed to elucidate the role of FBXL19‐AS1 in TNBC and its underlying mechanism. RT‐qPCR was employed to detect the expressions of FBXL19‐AS1 and miR‐378a‐3p in tissues and cells. Immunohistochemical staining and western blot were utilized to detect the expression levels of proteins. Cell activities were detected using flow cytometry, CCK‐8, and transwell assay. Dual‐luciferase reporter and RNA immunoprecipitation (RIP) assays were deployed to investigate interactions of different molecules. Protein–protein interaction (PPI) network, gene ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) pathways were used to analyze the downstream pathway. In vivo xenograft model was conducted to detect the effect of FBXL19‐AS1 on tumor growth. FBXL19‐AS1 was overexpressed in TNBC tissues and cell lines compared with counterparts. FBXL19‐AS1 knockdown suppressed TNBC cell activities, whereas its overexpression exhibited the opposite effect. Mechanistically, FBXL19‐AS1 was found to interact with miR‐378a‐3p. Further analysis revealed that miR‐378a‐3p exerted tumor‐suppressive effects in TNBC cells. Additionally, miR‐378a‐3p targeted and downregulated the expression of ubiquitin aldehyde binding 2 (OTUB2), a deubiquitinase associated with TNBC progression. In vivo experiments substantiated the inhibitory effects of FBXL19‐AS1 knockdown on TNBC tumorigenesis, and a miR‐378a‐3p inhibitor partially rescued these effects. The downstream pathway of the miR‐378a‐3p/OTUB2 axis was explored, revealing connections with proteins involved in modifying other proteins, removing ubiquitin molecules, and influencing signaling pathways, including the Hippo signaling pathway. Western blot analysis confirmed changes in YAP and TAZ expression levels, indicating a potential regulatory network. In summary, FBXL19‐AS1 promotes exacerbation in TNBC by suppressing miR‐378a‐3p, leading to increased OTUB2 expression. The downstream mechanism may be related to the Hippo signaling pathway. These findings propose potential therapeutic targets for TNBC treatment.