Abstract P2-06-11: TBK1 Promotes Growth of Aggressive Breast Cancer by Modulating the Tumor Microenvironment

Abstract Background: Triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC) are the most aggressive breast cancer subtypes. TANK-binding kinase 1 (TBK1), a member of the IKK family, regulates innate immune responses to viruses and other pathogens and functions as an immune-evasion gene. Studying TBK1 is crucial in the context of aggressive breast cancer due to its potentially significant role in tumorigenesis driven by regulation of the tumor microenvironment (TME). However, the molecular mechanisms of TBK1 signaling in regulating the tumorigenesis of TNBC and IBC remain unclear. To address this knowledge gap, we tested the hypothesis that TBK1 signaling promotes the aggressiveness of breast cancer by generating an immunosuppressive TME. Methods: We knocked out (KO) TBK1 expression in two human cancer cell lines [one IBC (SUM149) and one TNBC (HS578T)] and tested the effect on colony formation, migration, and invasion in vitro. Additionally, we performed RNA sequencing analysis on the control (Ctrl) and TBK1 KO clones to determine the underlying mechanism by which TBK1 regulates IBC and TNBC cell growth. Last, we inoculated Ctrl and TBK1 KO murine 4T1.2 TNBC cells into BALB/c mice and examined the effects of TBK1 KO on tumor growth and TME components. Results: TBK1 KO significantly reduced colony formation, migration, and invasion in both SUM149 and HS578T cells. RNA sequencing analysis of TBK1 KO clones revealed downregulation of pathways associated with the inflammatory response, such as IL-17 signaling and NF-kB signaling. Furthermore, cytokine-mediated signaling pathways and cytokine-stimulated cellular response were downregulated in these TBK1 KO clones. In the syngeneic murine 4T1.2 xenograft model, tumors derived from TBK1 KO cells exhibited slower growth (P = 0.0382) and had fewer M2 macrophages (P = 0.0068) than Ctrl cells. Additionally, TBK1 KO tumor samples showed a reduction in protein expression of immunosuppressive cytokines, including CCL27, CXCL1, CXCL2, and CCL2, compared to Ctrl tumors. These results collectively suggest that TBK1 can modulate the TME, promoting aggressive breast cancer tumorigenicity. Conclusion: TBK1 plays a critical role in the aggressiveness of aggressive breast cancers through generating an immunosuppressive TME. Further understanding TBK1's mechanisms can uncover novel therapeutic targets, potentially improving breast cancer treatment and patient outcomes. Citation Format: Lan Phi, Manuel Van Gijsel-Bonnello, James Long, Naoto T. Ueno, Xiaoping Wang. TBK1 Promotes Growth of Aggressive Breast Cancer by Modulating the Tumor Microenvironment [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P2-06-11.