Investigating the Role of Nuclear EGFR in Regulating the Tumor Immune Microenvironment in Breast Cancer

Abstract

EGFR functions as an oncogene via multiple pathways, including kinase-dependent signal transduction, calcium release, and through its function as a nuclear transcription co-factor. These pathways are involved in proliferation, survival, migration, and regulation of the tumor immune microenvironment (TIME). Although much is known about how EGFR signaling alters the TIME, little is known about the effect nuclear EGFR (nEGFR) has on regulating TIME in breast cancer. Considering that both EGFR signaling and nEGFR are oncogenic, it is possible that both function to create a tumor microenvironment that is conducive for tumor growth.Our findings demonstrate the effect EGFR signaling has on regulating TIME via the activation of the NF-κB pathway and thus, secretion of cytokines like IL-6, IL-8, and CXCL1, which are involved in the inflammatory response and the recruitment of monocytes/macrophages and neutrophils to the tumor microenvironment. This effect can be inhibited using EGFR tyrosine kinase inhibitors like erlotinib and sapitinib. In addition, we demonstrated the role of nEGFR in regulating TIME using novel peptide therapeutics, SAH5-EJ1 and cSNX1.3, cells modified to lack a nuclear localization sequence (EGFRΔNLS), and cells with MUC1 knockdown, showing that nEGFR suppresses the expression of cytokines and ligands involved in leukocyte-mediated immunity. Specifically, we demonstrated nEGFR suppresses the expression of IL-6, a cytokine known to have anti-tumor properties due to its effects on leukocyte survival, proliferation, differentiation, and recruitment. Via RNA-Seq and spatial transcriptomics, we showed that nEGFR suppresses the expression of natural killer (NK) cell activating receptor ligands and cytokines important for NK cell-mediated killing and recruitment. To test the impact this has on NK cell- mediated immunity, we inhibited nEGFR with cSNX1.3 and demonstrated enhanced NK cell- mediated killing. Targeting EGFR signaling did not result in the regulation of these ligands, cytokines, and NK cell-mediated killing, thereby highlighting a potentially key role of nEGFR- mediated oncogenesis. Together, these data reveal how EGFR signaling and nEGFR impact TIME in breast cancer. Although both function to create a pro-tumorigenic microenvironment, it is important to note the distinct ways in which they regulate TIME. This dissertation analyzes both the signal transduction impact of EGFR on TIME through activation of the NF-κB pathway and the role of nEGFR on TIME in regulating tumor growth.