miR-214 Promotes Aggressive Behavior in Triple-Negative Breast Cancer by Functionally Targeting the 3'-UTR of FRK.

Background/Objectives: MicroRNAs (miRNAs) are key regulators of gene expression and have been implicated in multiple aspects of cancer progression. However, the role of miR-214-3p in breast cancer remains controversial. In this study, we investigated the functional role of miR-214-3p and explored its potential regulatory target in breast cancer, particularly in triple-negative breast cancer (TNBC). Methods: miR-214-3p expression was evaluated in breast cancer cell lines. Luciferase reporter assays were performed to assess functional targeting of the FRK 3'-UTR. Functional assays, including proliferation, migration, and invasion assays, were conducted following miR-214-3p overexpression or FRK silencing. Results: miR-214-3p was markedly upregulated in TNBC cells (MDA-MB-231), while Fyn-related kinase (FRK), a potential tumor suppressor, showed an inverse expression trend. Luciferase reporter assays demonstrated that miR-214-3p functionally targets the 3'-UTR of FRK. Functional analyses revealed that overexpression of miR-214-3p significantly increased cell proliferation, migration, and invasion. Notably, silencing of FRK recapitulated these effects, supporting its role as a functional mediator of miR-214-3p. Conclusions: This study identifies a miR-214-FRK regulatory axis in breast cancer and suggests its contribution to aggressive tumor behavior. Targeting miR-214-3p or modulating FRK activity may represent a potential therapeutic strategy.