Posani, Sai Harshita2023-09-192023-09-192023-05https://hdl.handle.net/11299/256943University of Minnesota M.S. thesis. May 2023. Major: Pharmacology. Advisor: Carol Lange. 1 computer file (PDF); iv, 71 pages.Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks expression of hormone receptors and HER2 (Human epidermal growth factor 2) receptor overexpression. Even in the face of initially effective treatments, TNBC patients relapse and develop therapy resistance. One prime cause for this is the activation of cellular stress signaling pathways. The glucocorticoid receptor (GR) is a mediator of this endocrine/host stress response. The Lange lab has previously demonstrated that p38 MAP kinase phosphorylates GR at serine 134 (Ser134) in response to tumor microenvironment-derived growth factors and cytokines, such as HGF and TGFβ1, potent inputs of p38 MAPK signaling. Phospho-Ser134-GR (p-Ser134-GR) then upregulates gene sets whose protein products include the components of inducible signaling pathways that promote cancer cell survival, chemoresistance, altered metabolism, and migratory/invasive behavior in TNBC. In addition to binding with GR, glucocorticoids also bind with another closely related member of the steroid hormone receptor family - the mineralocorticoid receptor (MR). Functional responses upon activation of MR or post translational modifications of MR in TNBC are untapped areas. Our probe into public datasets (METABRIC, TCGA, and GEO) demonstrated significantly higher expression of MR transcripts in TNBC relative to luminal breast cancer. Additionally, the combined high expression of MR and GR predicted worse relapse-free survival in ERα-negative breast cancer patients compared to the cohort having a combined low expression. We hypothesize that MR, in partnership with GR, is a key player in advancing cancer phenotypes in TNBC. Inhibition of MR was carried out by siRNA-mediated knockdown and treatment with spironolactone, a competitive MR inhibitor. Interestingly, MR knockdown significantly reduced the TGFβ1-induced migratory capacity of breast cancer cells compared to the wild-type cells. For the first time, physical MR-GR complexation was observed upon corticosteroid and TGFβ1 treatment. In summary, the overarching goal of this study is to elucidate if MR is a required GR binding-partner and potential therapeutic target in GR-driven metastatic processes in TNBC.enThesis or Dissertation