Abstract 3163: PR/STAT3 nuclear transcriptional complexes mediate aurora-A kinase-induced stemness plasticity in ER+ breast cancer

Abstract

Abstract Purpose: Emergence of de novo or acquired resistance to standard of care endocrine therapies represents a major challenge in the clinical management of estrogen receptor alpha positive (ER+) breast tumors. This process is characterized by high tumor plasticity that confers to cancer cells the ability to shift from a differentiated state, with limited tumorigenic potential, to an undifferentiated state which is responsible for drug resistance and tumor relapse. In ER+ breast tumors, this plasticity is manifest by the enrichment of breast tumor initiating cells (BTICs) with stemness features, such as self-renewal capacity, CD44 expression and high ALDH activity, and ER down-regulation. Development of clinically relevant ER+ breast tumor models to test novel therapeutic strategies that inhibit the enhanced tumor cell plasticity and restore or extend endocrine sensitivity are urgently needed. Experimental Design: Unique endocrine resistant and metastatic breast cancer models were utilized to define in vitro and in vivo the pivotal role of Aurora-A mitotic kinase (AURKA) in the induction of stemness plasticity, endocrine therapy resistance and tumor progression. Unbiased phospho-proteomic analysis was performed in the absence or presence of alisertib, a clinically relevant AURKA inhibitor, that was used to identify novel down-stream targets of AURKA signaling pathway. Results: Phospho-proteomic analysis showed that AURKA targeting reduced the phosphorylation of STAT3 transcription factor at the serine-727 site. Significantly, herein we define a novel mechanism by which AURKA-induced self-renewal capacity is mediated through the activation of a phosphorylated serine727-STAT3/serine294-progesterone receptor (PR) transcriptional complex that regulates the expression of KLF4 stemness reprogramming gene. Remarkable, pharmacologic and genetic targeting of AURKA/STAT3/PR oncogenic axis impairs self-renewal capacity of endocrine therapy resistant breast cancer cells. Conclusions: In this study we demonstrate the pivotal role of a novel AURKA/STAT3/PR oncogenic axis in promoting stemness plasticity and endocrine therapy resistance. These findings provide the strong preclinical rationale for the development of novel combinatorial therapeutic strategies targeting cooperative AURKA/serine727-STAT3 and serine294-PR pathways predicted to result in the selective eradication of CD44High/ALDHHigh BTICs from the bulk tumor with consequent benefits to the clinical outcomes of patients with advanced ER+ breast cancer refractory to standard of care endocrine therapy. Citation Format: Antonino B. D'Assoro. PR/STAT3 nuclear transcriptional complexes mediate aurora-A kinase-induced stemness plasticity in ER+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3163.