Abstract 3922: NR2F1 limits dissemination and stemness of early breast cancer cells

Abstract

Abstract Tumor cells derived from MMTV-Neu mouse models or human ErBb2+ primary tumors are known to be able to complete all steps of the metastatic cascade. However, new evidence show that Neu+ early cancer cells derived from early stages of tumor progression (before detection of palpable tumors), can disseminate and, as disseminated cancer cells (early DCCs), enter a non-proliferative state for prolonged periods of time at secondary organs. We recently showed that early DCCs contributed to metastasis formation together with late-arriving DCCs (those coming from overt tumors). However, the mechanisms that would allow these early cancer cells, considered sessile and with few genetic alterations, to complete all steps of metastasis are unknown. Here we report that downregulation of the orphan nuclear receptor NR2F1 in Neu+ early cancer mammary epithelial cells (MECs) further activated a motile phenotype and this was coincident with previously described detection of circulating cancer cells (CCCs) and lung and bone marrow DCCs in MMTV-Neu mouse model. Knock down of basal NR2F1 levels in Neu+ early cancer cells induced cell motility, loss of laminin-V deposition, β-catenin delocalization from the membrane, dramatic loss of E-cadherin junctions and increased percentage of leader cells positive for CK14 and PRRX1 staining. Interestingly, TWIST and PRRX1 levels became upregulated upon NR2F1 depletion in 3D structures. These results suggest that NR2F1 expression maintains epithelial identity and suppresses epithelial-mesenchymal transition (EMT). Knock down of NR2F1 in Neu+ early cancer cells enhanced mammosphere formation efficiency and this was accompanied by upregulation of the pluripotency transcription factor NANOG and EMT master regulator TWIST. Interestingly, early dormant DCCs (negative for proliferation markers) showed re-expression of NR2F1 levels while micrometastases (cycling cells) had reduced levels of NR2F1. This result suggests that downregulation of NR2F1 in early DCCs may contribute to the dormancy escape of early DCCs and consequently metastatic relapse. Our findings provide for the first time evidence that NR2F1 functions as a suppressor of stemness and dissemination during early stages of tumor progression. We propose that therapies that restore expression of NR2F1 might limit early dissemination and the progression of early and late-arriving DCCs toward metastatic outgrowth. Citation Format: Maria Soledad Sosa. NR2F1 limits dissemination and stemness of early breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3922. doi:10.1158/1538-7445.AM2017-3922