A specific agonist of the orphan nuclear receptor NR2F1 suppresses metastasis through the induction of cancer cell dormancy
AO_SCPLOWBSTRACTC_SCPLOWDisseminated tumor cells (DTCs) in secondary organs often remain dormant for a long period of time before re-awakening and growing into overt metastases. We have previously identified NR2F1/COUP-TF1, an orphan nuclear receptor, as a master regulator of tumor cell dormancy in head and neck squamous cell carcinoma (HNSCC) and other cancer types. Here we describe the identification and function of a novel NR2F1 agonist herein referred to as compound 26 (C26). C26 was found to specifically activate NR2F1 in HNSCC cells, leading to increased NR2F1 transcription and nuclear protein accumulation. C26-mediated activation of NR2F1 induced growth arrest of HNSCC PDX line and cell lines in 3D cultures in vitro and on chicken embryo chorioallantoic membrane (CAM) in vivo. The effect of C26 on growth arrest was lost when NR2F1 was knocked out by CRISPR/Cas9. C26-induced growth arrest was mediated by activation of an NR2F1-regulated dormancy program, including upregulation of cyclin-dependent kinase (CDK) inhibitor p27 and the transcription factors retinoic acid receptor {beta} (RAR{beta}) and Sox9. In mice bearing HNSCC PDX tumors, combined adjuvant and neo-adjuvant treatment with C26 resulted in complete inhibition of lethal lung metastasis. Mechanistic analysis showed that lung DTCs in C26-treated mice displayed an NR2F1hi/p27hi/Ki-67lo phenotype, which kept them dormant in a single-cell state preventing their outgrowth into overt metastases. Our work reveals a novel NR2F1 agonist and provides a proof of principle strategy supporting that inducing DTC dormancy using NR2F1 agonists could be used as a therapeutic strategy to prevent metastasis.