Abstract 4960: COX-2 inhibition with celecoxib delays the progression of invasive mammary carcinoma in a murine model of collagen dense stroma.

Abstract

Abstract Breast cancer is the most common invasive cancer in women causing over 40,000 deaths yearly in the United States. Increased mammographic density correlates with over four-fold greater risk for breast cancer, making it one of the most important risk factors known for this disease. High breast density is correlated to increased collagen in the breast tissue, and we have found that increased collagen in the Col1a1tm1jae mouse model promotes mammary tumor formation and progression. Elevated collagen density in vitro increases expression of PTGS2 (prostaglandin-endoperoxide synthase 2), the gene for COX-2, by over four fold. COX-2 over-expression is observed in 40% of invasive breast carcinoma cases and correlates with poor prognosis. Based on these findings, we hypothesized that inhibition of COX-2 may be an effective therapy in the context of mammary tumors arising in dense tissue. Celecoxib is a selective non-steroidal anti-inflammatory drug (NSAID) that specifically inhibits COX-2. To understand the mechanism by which COX-2 affects cell signaling and response to collagen matrix density, we utilized our previously characterized model of MMTV-PyVT tumors on a wild type (wt) or Col1a1tm1jae background. Col1a1tm1jae heterozygote and wt littermates were randomly assigned at 11 weeks of age to treatment with placebo or celecoxib at 400mg per kilogram body weight. Oral treatment was given daily for 21 days. We found that MMTV-PyVT tumors responded to celecoxib in a manner that is regulated by matrix density (p-value <.0001). Tumors that arose on the dense Col1a1tm1jae background were larger and more invasive (p-value <.0001). Endpoint tumor size was diminished in mice treated with a daily dose of celecoxib, which delayed the development of tumors and changed the structure of the dense matrix. The effect of celecoxib was not as prominent for masses which developed on the low density wt background. Immunohistochemistry of relevant markers in these tissues is ongoing and will further our understanding of the effects of COX-2 inhibition in dense matrices. These findings suggest that COX-2 has a direct role in modulating the configuration of dense matrices which promote a more invasive cancer effect. Moreover, these findings suggest that COX-2 may be an effective therapeutic target for women with dense breast tissue. Citation Format: Karla Esbona, David R. Inman, Kevin W. Eliceiri, Lee G. Wilke, Patricia J. Keely. COX-2 inhibition with celecoxib delays the progression of invasive mammary carcinoma in a murine model of collagen dense stroma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4960. doi:10.1158/1538-7445.AM2013-4960