Potent estrogen receptor β agonists with inhibitory activity in vitro, fail to suppress xenografts of endocrine-resistant cyclin-dependent kinase 4/6 inhibitor-resistant breast cancer cells
Year: 2025
Type: article
Abstract: Objective: Seventy percent of newly diagnosed breast cancers are estrogen receptor-α positive and HER2/neu negative [1]. First-line treatments incorporate endocrine therapy and cyclin-dependent kinase 4/6 inhibitors [2]. However, therapy resistance occurs in most patients [3-5]. Hence, there is an urgent need for effective second-line treatments. We previously showed that the potent estrogen receptor-β agonists, OSU-ERb-12 and LY500307, synergized with the selective estrogen receptor modulator, tamoxifen, in vitro. Furthermore, we showed that these compounds inhibited endocrine-resistant and cyclin-dependent kinase 4/6-inhibitor-resistant estrogen receptor α-positive cell lines in vitro [6]. Here, we used fulvestrant- and abemaciclib-resistant T47D-derived cell line xenografts to determine the efficacy of the combination of OSU-ERb-12 and LY500307 with tamoxifen in vivo. Results: Despite efficacy in vitro, treatments failed to reduce xenograft tumor volumes. Hence, we conclude that this treatment strategy lacks direct cancer cell-intrinsic cytotoxic efficacy in vivo.
Source: Frontiers in Oncology
Language: English
Subfield: Pulmonary and Respiratory Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,801
OpenAlex ID: W4408875009