Candidate tumor suppressor gene IRF6 is involved in human breast cancer pathogenesis via modulating PI3K-regulatory subunit PIK3R2 expression.

Background/Aims: The tumor-suppressive functions of interferon regulatory factor 6 (IRF6) in some tumors have been preliminarily established, but its pathogenesis and underlying molecular mechanisms in breast cancer, the most common malignancy in women, remains poorly understood. Methods: Pairs of typical breast cancer cell lines (high- and low-aggressive) in addition to 27 breast cancer tissue samples and 31 non-cancerous breast tissues were used to investigate the expression level of IRF6 and Lentivirus-mediated gain-of-function studies, short hairpin RNA-mediated loss-of-function studies in vivo and in vitro were used to validate the role of IRF6 in breast cancer. Next, we performed RNA-Seq analysis to identify the molecular mechanisms of IRF6 involved in breast cancer progression. Results: Our findings showed that IRF6 was downregulated in highly invasive breast cancer cell lines but upregulated in poorly aggressive ones. Functional assays revealed that elevated IRF6 expression could suppress cell proliferation and tumorigenicity, and enhanced cellular chemotherapeutic sensitivity. To identify the molecular mechanisms involved, we performed a genome-wide and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis in breast cancer cells using RNA sequencing of gene expression profiles following the overexpression of IRF6. Genome-wide and KEGG analyses showed that IRF6 might mediate the PI3K-regulatory subunit PIK3R2, which in turn modulated the PI3K/AKT pathway to control breast cancer pathogenesis. Conclusion: We provide the first evidence of the involvement of IRF6 in breast cancer pathogenesis, which was found to modulate the PI3K/AKT pathway via mediating PIK3R2; indicating that IRF6 can be targeted as a potential therapeutic treatment of breast cancer.