Abstract P1-05-09: FH535 inhibited migration and growth of breast cancer cells
Authors: Dorchak JA , Iida J , Clancy R , Luo C , Chen Y , Hu H , Mural RJ , Shriver CD 
Published: August 2014

Background: Given the lack of effective targeted therapies for triple-negative (TN) breast cancer patients, a better understanding of the mechanisms of growth and invasion of these tumors will provide valuable insight into developing novel approaches to lower the mortality associated with TN breast cancer. There is substantial evidence indicating that the canonical Wnt signaling pathway is activated in TN breast cancer tissues. Previous studies report that FH535, a small molecule inhibitor of the Wnt signaling pathway, decreases growth of cancer cells but not normal fibroblast cells, suggesting this pathway plays a role in tumor progression and metastasis. In this study, we test FH535 as a potential inhibitor of migration, invasion, and growth against malignant phenotypes of breast cancer.

Methods and Results: We show that FH535 significantly inhibits growth, migration, and invasion of TN breast cancer cells (MDA-MB-231 and HCC38) using established protocols, implicating the Wnt signaling pathway plays a role in tumor progression and metastasis. FH535 is a potent growth inhibitor for TN breast cancer cells (MDA-MB-231 and HCC38), but not in other breast cancer cells (MCF-7, T-47D, or SK-BR-3) when cultured in three dimensional type I collagen gel. Additionally, western blotting analysis shows that treatment of MDA-MB-231 cells with FH535 markedly inhibits the expression of NEDD9, but not FAK, Src, or p130Cas, suggesting specificity of the Wnt signaling pathway in regulating gene expressions. Co-immunoprecipitation studies suggest that NEDD9 is specifically immunoprecipitated with CSPG4, but not with β1 integrin or CD44, implying CSPG4 and NEDD9 form a molecular complex for facilitating tumor migration, invasion, and growth. Statistical analysis (ANOVA) of The Cancer Genome Atlas (TCGA) project gene expression data (https://tcga-data.nci.nih.gov/) suggests that tumors from patients with basal-type breast cancer had significantly higher CSPG4 expression than tumors from patients with other subtypes, with all the p values &lt;0.0001. Moreover, Luminal A tumors also had a significantly higher CSPG4 expression than Luminal B tumors (p = 0.0006).

Discussion: In this study, we demonstrate the pivotal role of the canonical Wnt signaling pathway in enhancing tumor migration, invasion, and growth of TN breast cancer cells MDA-MB-231 and HCC38. We identified NEDD9 as a potential downstream target of the Wnt signaling pathway and found an association between NEDD9 and CSPG4 in MDA-MB-231 cells. Our results suggest a novel mechanism of migration, invasion, and growth of tumor cells involving a molecular complex between CSPG4 and NEDD9, which could be drug targets in TN and possibly Luminal A breast cancer patients. More comprehensive characterization of canonical Wnt signaling pathway by genomic and biological studies of breast cancer cells are clearly required for generating better treatments.

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Defense, or U.S. Government.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-05-09.