Abstract 2066: Targeting NUPR1: Response to a common compensatory pathway in triple negative breast cancer

Introduction: Triple negative breast cancer (TNBC) is a devastating disease responsible for a higher rate of morbidity and mortality compared to all other breast cancer subtypes. With few effective treatments, many have moved towards combination therapies. Using a genomically driven methodology, we show that Nuclear Protein 1 (NUPR1) is upregulated and activated in response to several targeted therapies and to standard chemotherapy. In this work, we show that targeting NUPR1 in conjunction with the chemotherapeutic paclitaxel, results in a synergistic combination. Methods: To evaluate a cohort of individuals with TNBC, 58 tumors were analyzed pre- versus post-chemotherapy using Ingenuity Pathway Analysis (IPA, Qiagen) after whole transcriptome sequencing. Six TNBC cell lines were utilized for in vitro work to reflect the heterogeneity of disease presentation. Four targeted therapies (Dasatinib, Erlotinib, Everolimus, and Trametinib) were chosen based on prior data suggesting activation of SRC, EGFR, mTOR, and MEK1/2 in TNBC respectively. Paclitaxel was also used as a standard chemotherapy. IC50s were calculated using standard log dose escalations and Prism 7 (GraphPad). Next, whole transcriptome sequencing and pathway analysis using IPA was performed on treated cells at their designated IC50s for each drug and compared to vehicle controls. Trifluoperazine (TFP, a small molecule inhibitor of NUPR1) and paclitaxel combination experiments were completed on TNBC cell lines and CI values were determined using the Chou-Talalay method. To observe the effects of NUPR1 inhibition, a NUPR1 siRNA was utilized in combination with paclitaxel at increasing doses with mock transfected cells for control. Results: We observed NUPR1 activation and RNA overexpression in all six cell lines treated with four targeted therapies. Combining the RNA sequencing analysis of these cell lines and focusing on common responses, NUPR1 was in the top three responses across all treatments. Our analysis of TNBC patient tumors (N=58) before and after chemotherapy resulted in observing an activation of NUPR1 (p=5.32E-10). In TFP and paclitaxel combination experiments, we observed CI values across cell lines ranging from .45-.90 denoting synergy. Experiments performed that knocked down NUPR1 with a siRNA displayed similar significant synergy with paclitaxel. Conclusion: Heterogeneous cell lines treated with targeted therapies as well as patients treated with chemotherapy demonstrate upregulation of the somatic pathway governing NUPR1. Targeting NUPR1’s ability to communicate using TFP in combination with paclitaxel increased the potency of paclitaxel at nanomolar doses. While further in vivo experiments testing this combination are an obligate next step, the combination of TFP and paclitaxel has the potential to be a viable treatment for TNBC that may be effective in a wider population. Citation Format: Jeffrey P. Solzak, Milan Radovich. Targeting NUPR1: Response to a common compensatory pathway in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2066.