Abstract 6800: Extracellular ATPase inhibitor-chemotherapy treatment of macrophages increases danger signal extracellular ATP to induce inflammatory pyroptotic cell death

Abstract Among cancers in women worldwide, breast cancer has the highest incidence and takes the most women’s lives. Patients with triple negative breast cancer (TNBC) experience worse outcomes than the patients diagnosed with hormone-dependent and human epidermal growth factor receptor-positive breast cancers because of the aggressive and rapidly progressive nature of breast cancer and the shortfall in the availability of specifically targeted therapies for TNBCs. Therefore, there is a demand for unique and fresh therapeutic approaches especially for TNBCs. Extracellular ATP (eATP) has been demonstrated to cause cell death in an autocrine and paracrine manner and is also a known danger signal that causes immune activation. Our previously published data reveals that at high micromolar concentrations eATP can induce cell death through the purinergic P2RX7 and P2RX4 receptors. We also demonstrated that eATP modulates TNBC cell death in the presence of chemotherapy. Despite this, eATP is rapidly degraded to adenosine by extracellular ATPases (eATPases). It should be noted that eATP release and activation of its receptor, P2XR7, are prerequisites for the activation of a complex of proteins known as the NLRP3 inflammasome and subsequent activation of caspase 1 which can lead to the induction of a highly inflammatory form of programmed cell death known as pyroptosis. It is particularly notable that the cell type most associated with this inflammatory form of cell death is macrophages, so we found it compelling to evaluate the effects of ATP signaling in macrophages. The objective of this study was to examine if the application of eATPase inhibitors will augment eATP release from chemotherapy-treated monocytic THP-1 and differentiated THP-1 cells and induce an inflammatory form of cell death known as pyroptosis. We previously showed that heparan sulfate inhibits multiple families of extracellular ATPases. Hence, we treated differentiated THP-1 cells with increasing concentrations of paclitaxel in the presence and absence of five different heparinoids that inhibit heparinase with cell viability and eATP being assessed. Furthermore, we found that there was an increase in caspase 1 activity, indicating increased pyroptosis, in monocytic THP-1 and differentiated THP-1 cells with the combined treatment of the E-NTPDase inhibitors PSB 069 or POM-1 and paclitaxel compared to paclitaxel treatment alone. These results show that eATP modulates monocytic THP-1 and differentiated THP-1 cells responses to chemotherapy, which could be advantageous to sensitize the anticancer effects of macrophages on TNBC cells. The development of efficacious therapies could stimulate an increase the depth and length of responses to chemotherapy and immunotherapy in TNBCs through pyroptosis induction of tumor associate macrophages through enhanced eATP. Citation Format: Jasmine M. Manouchehri, Mathew A. Cherian. Extracellular ATPase inhibitor-chemotherapy treatment of macrophages increases danger signal extracellular ATP to induce inflammatory pyroptotic cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6800.