Abstract P6-12-11: Celecoxib inhibits the growth of IBC tumors by suppressing the regulation of cancer stem-like cells by nodal

Abstract

Abstract Background: Inflammatory breast cancer (IBC) is an aggressive type of breast cancer with no known molecular targets for treatment. Although erythema is commonly associated with IBC, the molecular mechanism of inflammation in the pathogenesis of IBC remains unknown. We have previously shown that EGFR is an emerging target in IBC (Zhang D. et al Clin Can Res 2009). As crosstalk between EGFR and COX-2 plays an important role in the inflammatory response in several cancers, including breast cancer, we hypothesized that COX-2 promotes the tumorigenesis and metastasis of IBC cells. Methods: Using clinically derived IBC and non-IBC tumor samples, a Spearman's Rank correlation coefficient analysis was performed to analyze the expression levels of COX-2 and EGFR in IBC and non-IBC. The levels of COX-2 metabolites, prostaglandins (PGs) PGE2 and PGF2α, were measured in IBC and non-IBC cell lines by HPLC/MS method. Cell migration and invasion assays were performed using SUM149 and KPL-4 IBC cell lines treated with PGs or the COX-2 inhibitor, celecoxib. We evaluated the epithelial to mesenchymal transition (EMT)-like phenotype in 3D culture of SUM149 cells treated with celecoxib, and the stem-like population by mammosphere formation, and CD44+/CD24− and aldefluor+ population by FACS. We treated preclinical IBC xenograft mice with celecoxib and measured tumor growth, PGs levels, and the expression of EMT protein markers. Nodal, a stem cell regulator and potential biomarker for breast cancer progression, was evaluated in IBC cells following treatment with celecoxib and recombinant Nodal or transfection with Nodal cDNA. Results: EGFR and COX-2 expression levels positively correlated within IBC, but not non-IBC tumors. Elevated levels of PGE2 and PGF2α were identified in multiple IBC cell lines suggesting that COX activity is elevated within IBC compared to non-IBC cells. PGs altered EMT protein markers and promoted cell migration and invasion, while Celecoxib inhibited EMT and migration and invasion in SUM149 and KPL-4 cells. Celecoxib treatment inhibited tumor growth in mice, and downregulated the expression of EMT protein markers, including Nodal. Celecoxib decreased the stem-like CD44+/CD24−, and aldefluor+ population and the formation of mammospheres. Exogenous Nodal mitigated the effects of celecoxib on cell migration and invasion and the stem-like population in SUM149 cells. Conclusion: We conclude that activation of the COX-2 inflammatory signaling pathway is critical in the development and progression of IBC. This study provides a novel insight into how inflammation may regulate cancer stem cells via Nodal, and will guide future research into the development of stem cell targeted therapies for IBC. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-12-11.