Abstract PR06: Uncovering nuclear expulsion: chromatin-bound signals from dying cancer cells accelerate metastatic outgrowth through S100A4-RAGE pathway

Abstract

Abstract Tumor cells are highly heterogeneous, exhibiting diverse responses when exposed to different environments. We have recently observed this heterogeneity in tumor cell apoptosis by which some tumor cell die for the benefits of the population’s survival. Majority of tumor cells undergo apoptosis in response to immune surveillance, various treatments, and a hostile microenvironment, both in circulation and at metastatic organ sites. However, the full range of apoptotic signals, or "last words," that dying cells communicate to the surviving cancer cell community remains incompletely understood. While apoptotic cell death is often perceived as a favorable therapeutic outcome, tumor cells can exploit it to enhance their metastatic capabilities, leading to poor prognoses in certain cancers. Here, we present a remarkable discovery of an altered apoptotic program in tumor cells characterized by nuclear expulsion and citrullinated chromatin, promoting metastatic outgrowth in the lungs in a Padi4-dependent manner. We further identified a calcium spike during apoptosis as the trigger for Padi4 activation, resulting in rapid chromatin de-condensation, nuclear content expulsion, followed by the generation of nuclear expulsion products (NEPs). This process was observed in various types of human cancer tissues. Profiling of proteins bound to the NEP complex unveiled an enrichment of receptor for advanced glycation end-products (RAGE) pathway proteins, such as S100a4 in mouse NEPs and high-mobility group-binding (HMGB) proteins in human NEPs. These chromatin-bound RAGE ligands activated RAGE receptors in neighboring surviving tumor cells, leading to Erk pathway activation. This, in turn, promotes proliferation through the RAGE-MAPK pathway. A nuclear expulsion signature was associated with worse prognoses in cancer patients, underscoring the clinical efficacy in the context of apoptosis-inducing treatments. As we continue our investigations, we are particularly interested in understanding how dying tumor cell-derived NEPs from chemotherapy may affect therapy outcomes. Taken together, our studies uncover a novel mechanism by which tumor cells come together as a community and that the apoptotic tumor cells help live tumor cells metastasize. This insight is likely a step forward to understand the mechanisms of metastatic spread, treatment resistance and relapse. Citation Format: Wooyong Park, Justin M Gray, Ronald J Holewinski, Thorkell Andresson, Jae Young So, Carmelo M Carmona-Rivera, Mariana J Kaplan, Steven D Cappell, Li Yang. Uncovering nuclear expulsion: chromatin-bound signals from dying cancer cells accelerate metastatic outgrowth through S100A4-RAGE pathway [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr PR06.