FOXF2 deficiency accelerates the visceral metastasis of basal-like breast cancer by unrestrictedly increasing TGF-ß and miR-182-5p

The mesenchymal transcription factor forkhead box F2 (FOXF2) is a critical regulator of embryogenesis and tissue homeostasis. Our previous studies demonstrated that FOXF2 is ectopically expressed in basal-like breast cancer (BLBC) cells and that FOXF2 deficiency promotes the epithelial–mesenchymal transition and aggressiveness of BLBC cells. In this study, we found that FOXF2 controls transforming growth factor-beta (TGF-ß)/SMAD signaling pathway activation through transrepression of TGF-ß-coding genes in BLBC cells. FOXF2-deficient BLBC cells adopt a myofibroblast-/cancer-associated fibroblast (CAF)-like phenotype, and tend to metastasize to visceral organs by increasing autocrine TGF-ß signaling and conferring aggressiveness to neighboring cells by increasing paracrine TGF-ß signaling. In turn, TGF-ß silences FOXF2 expression through upregulating miR-182-5p, a posttranscriptional regulator of FOXF2and inducer of metastasis. In addition to mediating a reciprocal repression loop between FOXF2 and TGF-ß through direct transrepression by SMAD3, miR-182-5p forms a reciprocal repression loop with FOXF2 that directly transrepresses MIR182expression. Therefore, FOXF2 deficiency accelerates the visceral metastasis of BLBC through unrestricted increases in autocrine and paracrine TGF-ß signaling, and miR-182-5p expression. Our findings provide novel mechanisms underlying the roles of TGF-ß, miR-182-5p, and FOXF2 in accelerating BLBC dissemination and metastasis, and may facilitate the development of therapeutic strategies for aggressive BLBC.