Abstract P3-06-03: NR2F1 is a barrier to dissemination of early-evolved mammary cancer cells

Abstract

Abstract Pre-malignant cells disseminate during very early and sometimes asymptomatic stages of tumor progression. Once settled in permissive environments at secondary organs, they can act as a source for metastasis (e.g. in breast, pancreatic, colon, melanoma and lung carcinomas), thus emerging as important players in future prognosis. Granted that biological barriers to tumorigenesis exist, there must also be limiting steps to early dissemination in pre-malignant cells, all of which remain largely unknown. We report that the orphan nuclear receptor NR2F1/COUP-TF1, downstream of Her2 signaling via p38alpha serves as a barrier to early dissemination in pre-malignant breast cells. Our work shows that NR2F1 expression is positively regulated by p38α-MAPK pathway and inhibited by HER2 oncogenic signaling pathway. Furthermore, NR2F1 downregulation in human and murine pre-malignant cell lines led to a partial epithelial-to-mesenchymal transition characterized by decreased E-cadherin expression and β-catenin membrane localization, disorganized laminin 5 deposition, and increased expression of CK14, TWIST1, ZEB1 and PRRX1, thus explaining an increased motility and dissemination of early cells upon loss of NR2F1. Interestingly, NR2F1 lost also maintained epithelial markers (like CK18), suggesting an hybrid luminal-mesenchymal phenotype that could favor cellular plasticity to adapt to distant sites. We also showed that NR2F1 blocked b-catenin nuclear localization via a WNT-dependent pathway. Significantly, downregulation of NR2F1 increased the in vivo dissemination potential of pre-malignant cells to lungs in a HER2-dependent manner. Lastly, Nr2f1 expression was downregulated in non-invasive DCIS biopsies when compared to benign adjacent tissue, and its expression was inversely correlated to Prrx1 levels. The inverse correlation between Nr2f1 and Prrx1 levels was lost in genetically evolved primary tumors, which suggests that a unique inhibitory mechanism of dissemination dominates at early stages of tumor progression. Overall, our data suggest the existence of an inhibitory mechanism of dissemination regulated by NR2F1 downstream of HER2 signaling in premalignant breast cells and propose that therapeutic strategies that aim to maintain NR2F1 expression could reduce dissemination of premalignant cells and delay relapses. Citation Format: Carolina Rodriguez-Tirado, Nupura Kale, Maria Jose Carlini, Nitisha Shrivastava, Alcina Rodrigues, Bassem Khalil, Jose Javier Bravo-Cordero, Melissa Alexander, Jiayi Ji, Maria Soledad Sosa. NR2F1 is a barrier to dissemination of early-evolved mammary cancer cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-06-03.