Disrupting Cholesterol-FOXO3-KRT14 axis suppresses metastasis of triple-negative breast cancer

High metastatic propensity is a devastating challenge to effective therapy of solid tumors, including triple-negative breast cancer (TNBC). In this study, we performed a genome-scale screen and found that cholesterol homeostasis is essential for tumor progression in immunocompetent mice. In an orthotopic TNBC model, intracellular cholesterol promoted lung metastasis by sustaining the expression of keratin 14 (KRT14) and decreasing MHC II, which was indispensable for the cluster metastasis of TNBC. Mechanistic studies demonstrated that FOXO3a regulated the transcription of KRT14. FOXO3a recognized and directly bound to the promoter of KRT14 to inhibit its expression. Cholesterol disrupted the nuclear translocation of FOXO3a by sustaining its phosphorylation, which was regulated by IKK, one of the major upstream kinases of FOXO3a. Apolipoprotein A1 (ApoA1) increased cholesterol efflux and inhibited TNBC metastasis by regulating the IKK-FOXO3a-KRT14 axis. The recombinant adenovirus encoding ApoA1 (ADV-ApoA1) promoted cholesterol efflux, dampened metastasis, and prolonged survival in mice bearing TNBC. Finally, we provided preliminary data showing that high doses of ADV-ApoA1 were well tolerated in rhesus monkeys and Syrian hamsters injected both intravenously and hypodermically. Taken together, cholesterol promotes metastasis via the IKK-FOXO3a-KRT14 axis in TNBC, and facilitating cholesterol efflux from TNBC cells is a promising therapeutic strategy for TNBC clinical treatment.