Loss of miR-634 contributes to the formation FOXA1-positive triple negative breast cancer subtype.

Background: Triple-negative breast cancer (TNBC), the most aggressive subtype of breast cancer, lacks targeted therapies, posing a substantial challenge for treatment. Therefore, investigating its pathogenesis is a crucial research focus. FOXA1 and miR-634 are involved in tumorigenesis. However, the molecular mechanisms underlying the aberrant upregulation of FOXA1 expression in TNBC remain unclear. Therefore, we explore the role of miR-634 in the FOXA1-positive TNBC subtype.

Methods: Quantitative reverse transcription polymerase chain reaction was used to detect miR-634 expression in breast cancer tissues and cell lines. Aberrantly activated signaling pathways and related genes in TNBC were analyzed using The Cancer Genome Atlas. The potential target of miR-634 was predicted by TargetScan, the TNBC cell proliferation rate was detected using an MTT assay, the in vitro metastatic capacity was determined by transwell assay and the cell cycle distribution was tested using flow cytometry. Western blotting was performed to measure the expression of proteins involved in the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway.

Results: The expression of miR-634 was significantly down-regulated in both TNBC tissues and cells, compared with adjacent non-cancerous tissues and MCF10A, respectively. Ectopic expression of miR-634 inhibits breast cancer cell proliferation and in vitro metastasis. The TCGA-based expression profile analysis of TNBC revealed that aberrantly activated PI3K/AKT signaling may contribute to its malignant phenotype. FOXA1, the top hit of aberrantly upregulated genes in TNBC, was a direct target of miR-643. Moreover, forced expression of miR-643 drastically suppressed FOXA1 expression by the inactivation PI3K/AKT signaling.

Conclusion: MiR-634 suppresses FOXA1 to inhibit the proliferation and metastasis of TNBC cells by inactivating the PI3K/AKT signaling pathway.