Presentation description

Breast cancer is responsible for 15% of cancer-related deaths in women and comprises various subtypes that influence tumor behavior. Our focus is on Triple Negative Breast Cancer (TNBC), which accounts for 15-20% of breast cancer cases and lacks targeted drugs. To explore new therapies for TNBC, we employed Patient-Derived Xenograft Organoids (PDxOs) derived from Patient-Derived Xenografts (PDXs), creating 3D in vitro models. Using PDxOs, we assessed potential therapies by analyzing cell viability after treatment, revealing distinct drug responses among PDxOs. Notably, some PDxOs exhibited initial resistance (BR) or sensitivity (BS) to Birinapant, a SMAC mimetic targeting Cellular Inhibitor of Apoptosis Proteins (IAPs) to induce cell death via the Tumor Necrosis Factor Receptor (TNFR) extrinsic apoptosis pathway. As BR-PDxOs lacked apoptosis, we investigated the overlapping signaling pathway of cell viability (NF-𝜅B), which might impede birinapant-mediated apoptosis. Our hypothesis suggests that BR-PDxOs exhibit higher baseline and/or Birinapant-induced NF-𝜅B signaling compared to BS-PDxOs. To validate this, we treated 2D cells and BR-PDxOs with TNF-𝛼, performing Western blots for NF-𝜅B signaling proteins. We observed desired protein presence, high NF-𝜅B induction in 2D lines after treatment, and slight induction in BR-PDxOs before and after treatment. However, we were unsure if these differences resulted from the culturing format or explained birinapant resistance linked to TNFR involvement in apoptosis signaling. To further investigate, we treated BS- and BR-PDxOs with TNF-𝛼 to compare NF-𝜅B signaling induction via Western Blot. Subsequent experiments will involve treating PDxOs with Birinapant and caspase inhibition to determine how NF-𝜅B signaling varies and contributes to Birinapant resistance. Our future directions include studying protein recruitment to the TNFR through ubiquitin and TNFR co-immunoprecipitation, thereby enhancing our understanding of apoptosis signaling and the overall mechanism of birinapant resistance.