Reduced JAG1 expression through miR-200 overexpression or Crispr-Cas mediated knockout impairs TNBC growth and metastasis.

Studies from our lab and others demonstrated that increasing miR-200 expression in TNBC cell lines reduced proliferation and invasion in vitro and tumor growth and metastasis in vivo. However, the mechanisms through which miR-200s suppress TNBC growth and metastasis remains incompletely characterized. In this study, we found that overexpression of miR-200s in MDA-MB-231 and MDA-MB-436 cells significantly reduced the expression of several Notched-Jagged genes including JAG1. To further investigate the importance of JAG1, JAG1 was knocked out using Crispr-Cas in MDA-MB-231 cells which express high endogenous JAG1. Loss of JAG1 in MDA-MB-231 cells significantly reduced proliferation and invasion as well as increasing apoptosis in vitro. Moreover, loss of JAG1 delayed mammary tumor onset, mammary tumor growth rate and metastatic dissemination in vivo. RNA sequencing of control and MDA-231JAG1KO tumors revealed that knocking out JAG1 altered the expression of genes associated with the extracellular matrix, angiogenesis, and epithelial to mesenchymal transition. These results imply that miR-200s may mediate some of their anti-tumor actions through reducing JAG1 expression. In addition, the loss of JAG1 dramatically suppressed TNBC growth and metastasis thus suggesting that agents targeting JAG1 should be further evaluated as a therapeutic strategy for TNBC.