PTHrP Regulates Fatty Acid Metabolism via Novel lncRNA in Breast Cancer Initiation and Progression Models.

Simple Summary: The 5-year survival rate for women with metastatic breast cancer is 29%. Potential biomarker identification is important for new treatment modalities in affected patients. Previous studies have shown that Parathyroid hormone-related peptide (PTHrP) plays a critical role in breast cancer growth and metastasis. Our study aimed to use a genetically modified breast cancer mouse model to precisely examine the role of PTHrP from early primary breast cancer initiation to late progression. We identified a novel long non-coding RNA (lncRNA), a new target for fatty acid metabolism that can be regulated via PTHrP in our unique mouse breast cancer model. We confirmed that a potential human lncRNA, OLMALINC, plays a similar role in fatty acid metabolism that can be regulated via PTHrP and validated our mouse findings in human breast cancer cell lines. Genetically engineered mouse models provide valuable tools to study the molecular metabolism for breast cancer progression. Parathyroid hormone-related peptide (PTHrP) is the primary cause of malignancy-associated hypercalcemia (MAH). We previously showed that PTHrP ablation, in the MMTV-PyMT murine model of breast cancer (BC) progression, can dramatically prolong tumor latency, slow tumor growth, and prevent metastatic spread. However, the signaling mechanisms using lineage tracing have not yet been carefully analyzed. Here, we generated Pthrpflox/flox; Cre+ mT/mG mice (KO) and Pthrpwt/wt; Cre+ mT/mG tumor mice (WT) to examine the signaling pathways under the control of PTHrP from the early to late stages of tumorigenesis. GFP+ mammary epithelial cells were further enriched for subsequent RNA sequencing (RNAseq) analyses. We observed significant upregulation of cell cycle signaling and fatty acid metabolism in PTHrP WT tumors, which are linked to tumor initiation and progression. Next, we observed that the expression levels of a novel lncRNA, GM50337, along with stearoyl-Coenzyme A desaturase 1 (Scd1) are significantly upregulated in PTHrP WT but not in KO tumors. We further validated a potential human orthologue lncRNA, OLMALINC, together with SCD1 that can be regulated via PTHrP in human BC cell lines. In conclusion, these novel findings could be used to develop targeted strategies for the treatment of BC and its metastatic complications. [ABSTRACT FROM AUTHOR]