Augmenting Anti-Tumor Immunity by Targeting Macrophage Cox-2 in Breast Cancer

Thumbnail Image
Degree type
Doctor of Philosophy (PhD)
Graduate group
Breast Cancer
Tumor Microenvironment
Grant number
Copyright date
Related resources

Cyclooxygenase-2 (COX-2) expression is associated with poor prognosis across a range of human cancers, including breast. While the contributions of tumor cell-derived COX-2 are well studied, those of the stroma remain ill-defined. Macrophages, an essential component of the tumor microenvironment, exist within a range of two polar phenotypes, influenced by signals in their local environment: anti-tumorigenic M1 or pro-tumorigenic M2. M2-like tumor-associated macrophages (TAM) are positively associated with tumorigenesis. This thesis investigates the contribution of macrophage COX-2 in two models of HER2/neu-induced mammary tumorigenesis utilizing mice selectively lacking macrophage COX-2 (COX-2^MØKO) and the contribution of COX-2 derived products in modifying macrophage phenotype in vitro. Finally, a targeted macrophage COX-2 inhibitor is investigated in vitro and in vivo as a potential cancer therapeutic. Deletion of macrophage COX-2 led to reduced mammary tumorigenesis coincident with fewer TAMs and reduction in M2 characteristics of TAM. Further, depletion of CD8+ cytotoxic T lymphocytes (CTLs), but not CD4+ T helper and regulatory cells, restored tumor growth in COX-2^MØKO mice, suggesting enhanced CTL function caused by reduction in total and M2-like TAM. Investigation of COX-2-mediated polarization of bone marrow-derived macrophages (BMDM) in vitro revealed paracrine influences of prostaglandin (PG) E2 in modifying polarized macrophage phenotype to more closely resemble TAM. Interestingly, interference with macrophage COX-2 did not significantly modify BMDM polarization. This suggested that autocrine COX-2 minimally affects BMDM phenotype, and that polarization of COX-2^MØKO BMDM does not recapitulate reduced M2 characteristics observed in COX-2^MØKO TAM. Reconstituted high-density lipoprotein (rHDL) nanoparticles were utilized as a method to target macrophages in vitro and in vivo. rHDL conjugated to fluorescent dye DiR revealed efficient incorporation of rHDL nanoparticles with TAM. In preliminary experiments utilizing rHDL-celecoxib as a targeted macrophage COX-2 inhibitor, marked suppression of PGD2 and PGE2 generation was evident in lipopolysaccharide (LPS)-stimulated J774A.1 cells. Importantly, urinary prostaglandin levels were not altered in mice treated with rHDL-celecoxib, suggesting no systemic inhibition of COX-2 with this targeted approach. These studies provide rationale for targeting macrophage COX-2 in mammary tumorigenesis and provide essential preliminary experiments in translating these findings into a potential chemopreventative or chemotherapeutic agent.

Emer M. Smyth
Date of degree
Date Range for Data Collection (Start Date)
Date Range for Data Collection (End Date)
Digital Object Identifier
Series name and number
Volume number
Issue number
Publisher DOI
Journal Issue
Recommended citation