Characterization and Targeting of Platelet-Derived Growth Factor Receptor alpha (PDGFRA) in Inflammatory Breast Cancer (IBC)1

PURPOSE Inflammatory breast cancer (IBC) is arguably the deadliest form of breast cancer due to its rapid onset and highly invasive nature. IBC carries 5- and 10-year disease-free survival rates of ~45% and <20%, respectively. Multiple studies demonstrate that in comparison with conventional breast cancer, IBC has a unique molecular identity. Here, we have identified platelet-derived growth factor receptor alpha (PDGFRA) as being uniquely expressed and active in IBC patient tumor cells. EXPERIMENTAL DESIGN Here we focus on characterizing and targeting PDGFRA in IBC. Using gene expression, we analyzed IBC patient samples and compared them with non-IBC patient samples. Further, using IBC cells in culture, we determined the effect of small molecules inhibitors in both in vitro and in vivo assays. RESULTS In IBC patients, we show more frequent PDGFRA activation signature than non-IBC samples. In addition, the PDGFRA activation signature is associated with shorter metastasis-free survival in both uni- and multivariate analyses. We also demonstrate that IBC cells express active PDGFRA. Finally, we show that PDGFRA targeting by crenolanib (CP-868-596), but not imatinib (STI571), two small molecule inhibitors, interferes with IBC cell growth and emboli formation in vitro and tumor growth in vivo. CONCLUSIONS Our data suggest that PDGFRA may be a promising target for therapy in IBC.