Cholesteryl Ester Promotes Mammary Tumor Growth in MMTV-PyMT Mice and Activates Akt-mTOR Pathway in Tumor Cells

The association between intratumoral cholesteryl ester (CE) and tumor progression has been reported previously. The objective of our study was to investigate a causal effect of CE on mammary tumor progression. Using MMTV-PyMT (MMTV-polyoma virus middle T) transgenic mice and breast tumor cell MCF-7, we show that both exogenous and endogenous CE can increase mammary tumor growth, that CE upregulates the AKT/mTOR pathway, and that CE synthesis blockade suppresses this signaling pathway. Our data suggest that SOAT1, a sterol O-acyltransferase, may be a potential target for the treatment of breast cancer.

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

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 suggest that MaTAR20 is likely an important driver of mammary tumor progression and represents a promising new therapeutic target.

Lysophosphatidic acid-RAGE axis promotes lung and mammary oncogenesis via protein kinase B and regulating tumor microenvironment

Background Receptor for advanced glycation end products (RAGE) is a multi-ligand transmembrane receptor of the immunoglobulin superfamily. Lysophosphatidic acid (LPA) is a ligand for RAGE and is involved in physiological and pathophysiological conditions including cancer. However, RAGE-LPA axis is unexplored in lung and mammary cancer. Methods RAGE was silenced in A549, MDA MB-231 and MCF7 using RAGE shRNA. For in vitro tumorigenesis, we performed wound healing, colony formation, cell proliferation and invasion assays. Evaluation of expression of oncogenes, EMT markers and downstream signaling molecules was done by using western blot and immunohistochemistry. For subcellular expression of RAGE, immunofluorescence was done. In vivo tumorigenesis was assessed by intraperitoneal injection of cancer cells in nude mice. Results Here we show RAGE mediated profound increase in proliferation, migration and invasion of lung and mammary cancer cells via LPA in Protein kinase B (PKB) dependent manner. LPA mediated EMT transition is regulated by RAGE. In vivo xenograft results show significance of RAGE in LPA mediated lung and mammary tumor progression, angiogenesis and immune cell infiltration to tumor microenvironment. Conclusion Our results establish the significance and involvement of RAGE in LPA mediated lung and mammary tumor progression and EMT transition via RAGE. RAGE-LPA axis may be a therapeutic target in lung and mammary cancer treatment strategies.