Breast Cancer Projects

Cyclooxygenase-2 Inhibitor Enhances the Efficacy of a Breast Cancer Vaccine: Role of Indoleamine 2,3-Dioxygenase

We have used the oncogenic mice that carry the polyoma virus middle T antigen driven by the MMTV promoter (PyV MT mice) in this study. These mice develop spontaneous tumors of the breast, which metastasize to the lungs and bone marrow. Tumors arise with synchronous kinetics and are highly fibrotic with dense connective tissue separating individual nests of tumor cells, a pathology that closely resembles scirrhous carcinomas of the human breast.

The PyV MT mouse model is therefore an appropriate model for human metastatic breast cancer, in which to evaluate therapeutic strategies as well as understand the mechanisms associated with therapy-induced growth inhibition. We have shown that celecoxib, a specific cyclooxygenase-2 (COX-2) inhibitor when administered in combination with a dendritic cell (DC)-based breast cancer vaccine (DCs pulsed with PyV MT tumor lysate) significantly augments the effectiveness of the vaccine in reducing primary tumor burden, preventing metastasis, and increasing survival. Reduction in mammary tumor burden was associated with increased tumor cell apoptosis and decreased proliferation in vivo. In vivo apoptosis correlated with significant decrease in activation of protein kinase B, Akt, a cell-survival signaling kinase, with increased expression of pro-apoptotic protein, Bax, and decreased expression of anti-apoptotic proteins, Bcl-2 and survivin. In addition, combination treatment reduced levels of pro-angiogenic factor, vascular endothelial growth factor (VEGF), and reduced angiogenesis in this model. Improved vaccine potency was associated with an increase in tumor-specific cytotoxic T lymphocytes (CTLs).

We determined that enhanced CTL activity was due to a significant decrease in expression of tumor-associated indoleamine 2, 3- dioxygenase (IDO), a negative regulator of T cells. We report that inhibiting tumor-associated COX-2 activity in vivo can regulate IDO expression within the tumor microenvironment. Thus, a novel mechanism of COX-2 induced immunosuppression via regulation of IDO has emerged that may have implications in designing future cancer vaccines. Inhibition of IDO in combination with immunotherapy may be a plausible option for the treatment of human metastatic breast cancer. This is especially relevant since clinical trials with COX-2 inhibitors are under fire and alternative, safer agents are required.

Reduced T Cell and Dendritic Cell Function is Related to COX-2 Overexpression and PGE2 Secretion in Patients with Breast Cancer

In several neoplastic diseases, including breast cancer, immunosuppression correlates with disease stage, progression and outcome. Thus, thorough analysis of immune parameters in breast cancer patients may be beneficial in designing effective anti-cancer immune-based therapies. We have investigated dendritic cell (DC) and T cell function from breast cancer patients at various stages of the disease and age-matched controls. We also evaluated cyclooxygenase 2 (COX-2) expression and prostaglandin E2 (PGE2) levels within the tumor milieu and in the circulation. T cells from cancer patients showed decreased proliferation in response to CD3 antibody stimulation. Analysis of Th1/Th2 cytokines revealed reduced levels of IFN-γ, TNF-α, IL-12 and IL-2 and increased levels of IL-10 and IL-4. DCs from these patients showed significantly reduced expression of co-stimulatory molecules (B7 and CD40) and demonstrated reduced phagocytic ability, reduced antigen presentation to T cells, and reduced ability to mature in response to lipopolysaccharide (LPS). Data revealed increased synthesis of PGE2, an immune suppressor, along with increased expression of COX-2, a key regulator of PGE2 synthesis. COX-2-induced PGE2 may contribute to the immunosuppression and may directly block anti-tumor immunity while promoting tumor growth, providing us with the rationale for using COX-2 inhibition combined with immunotherapy.

The Influence of Arthritis On Breast Cancer-Associated Bone Metastasis

The preference of breast cancer cells for bone as a metastatic site is underscored by the fact that 65-75 percent of patients with advanced disease develop bone metastases. We hypothesize that chronic inflammatory milieu and osteoclastic bone resorption caused by autoimmune arthritis may influence the recruitment, retention, and proliferation of tumor cells in the bone and promote metastasis.

The arthritic bone milieu is comprised of inflammatory cells, cytokines, chemokines, cyclooxygenases (COX), lipooxygenase (LOX), and various eicosanoids, that may attract and foster tumor cells to the inflamed site. IL-17 is identified as a crucial cytokine for osteoclastic bone resorption in autoimmune arthritis patients. IL-17 acts on osteoblasts by stimulating COX-2–dependent prostaglandin E2 (PGE2), and osteoclast differentiation factor which differentiates osteoclast progenitors into mature osteoclasts, causing bone resorption. PGE2 interacts with its eicosanoid receptors to induce the damage.

Aims are to determine:

1. The incidence of bone metastasis in a spontaneous model of autoimmune arthritis that are induced to develop breast carcinomas;
2. The incidence of bone metastasis in mouse models of spontaneous breast cancer that are induced to develop autoimmune arthritis;
3. The efficacy of anti-IL-17 antibody treatment alone, or in combination with COX-2 inhibitor or eicosanoid receptor antagonists in the prevention of bone metastasis; and
4. Retrospectively, the incidence of arthritis in breast cancer patients with or without bone metastasis. If the proposed study is conclusive, it could be used in the prevention of bone metastasis, in combination drug delivery, or as a risk-assessment tool for possible future bone metastasis.

Funded by Susan G. Komen For the Cure, the Department of Defense Congressionally Directed Medical Research Program in Breast Cancer Concept Award, and a National Cancer Institute-sponsored Specialized Program of Research Excellence (SPORE) grant for breast cancer.