Abstract Long non-coding RNAs (lncRNAs) are an emerging class of regulatory molecules that have been shown to play important roles in tumorigenesis and cancer progression. Here, we studied the recently identified lncRNA Mammary Tumor Associated RNA 20 ( MaTAR20 ) in mammary cancer progression. A CRISPR/Cas9 knockout of MaTAR20 in the metastatic 4T1 cell line led to reduced cancer cell proliferation and increased cell surface adhesion compared to control cells. Consistent with these knockout results antisense oligonucleotide (ASO) mediated knockdown of MaTAR20 resulted in reduced growth and invasion in 4T1 cells, and in primary mammary tumor organoids derived from the MMTV-PyMT mouse model of breast cancer. Injection of MaTAR20 -specific ASOs subcutaneously into tumor bearing MMTV-PyMT mice resulted in smaller and highly necrotic tumors in comparison to mice injected with a scrambled control ASO. To investigate the molecular mechanism by which MaTAR20 acts to advance mammary tumor progression, we applied a combination of RNA-sequencing and RNA-pulldown coupled to DNA-sequencing. These analyses demonstrated that the nuclear retained lncRNA is associated with several essential cancer signaling pathways such as VEGF signaling. In particular, MaTAR20 directly binds to and regulates the expression of Tnfsf15 . Our results indicate that MaTAR20 is an important driver of mammary tumor progression and represents a promising new therapeutic target.

The long non-coding RNA MaTAR20 promotes mammary tumor growth by regulating angiogenesis pathways