https://www.selleckchem.com/products/pt2399.html Similarly, clonal and spatial heterogeneity in tumor biopsies from a clinical patient with BRCA1-mutant HGSC with acquired PARPi resistance was observed. In an imaging-based drug screening, the clones showed heterogenous responses to targeted therapeutic agents, indicating that not all PARPi-resistant clones can be targeted with just one therapy. Furthermore, PARPi-resistant clones showed mechanism-dependent vulnerabilities to the selected agents, demonstrating that a deeper understanding on the mechanisms of resistance could lead to improved targeting and biomarkers for HGSC with acquired PARPi resistance. SIGNIFICANCE This study shows that BRCA1-deficient cells can give rise to multiple genomically and functionally heterogenous PARPi-resistant clones, which are associated with various vulnerabilities that can be targeted in a mechanism-specific manner.Inflammatory breast cancer (IBC) is a highly metastatic breast carcinoma with high frequency of estrogen receptor α (ERα) negativity. Here we explored the role of the second ER subtype, ERβ, and report expression in IBC tumors and its correlation with reduced metastasis. Ablation of ERβ in IBC cells promoted cell migration and activated gene networks that control actin reorganization, including G-protein-coupled receptors and downstream effectors that activate Rho GTPases. Analysis of preclinical mouse models of IBC revealed decreased metastasis of IBC tumors when ERβ was expressed or activated by chemical agonists. Our findings support a tumor-suppressive role of ERβ by demonstrating the ability of the receptor to inhibit dissemination of IBC cells and prevent metastasis. On the basis of these findings, we propose ERβ as a potentially novel biomarker and therapeutic target that can inhibit IBC metastasis and reduce its associated mortality. SIGNIFICANCE These findings demonstrate the capacity of ERβ to elicit antimetastatic effects in highly aggressive inflammatory br