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Abstract 1951: Role of mitochondrial peptide Humanin in the response of experimental breast cancer to chemotherapy

Humanin (HN) is a mitochondrial-derived peptide with potent cytoprotective effect in many cell types. Administration of HN has been proposed as a therapeutic approach for several chronic diseases, such as diabetes, neurodegenerative conditions and cardiovascular diseases. Although HN has been shown to protect normal tissues against the toxic effects of chemotherapy, its role in tumor chemoresistance is poorly understood. Here, we aimed to elucidate the role of HN in the progression and cytotoxic response of experimental triple negative breast cancer (TNBC). We detected HN expression in murine and human TNBC cells, which was upregulated in the presence of chemotherapeutic drugs, i.e. Doxorubicin (DOXO) and Cisplatin, as assessed by flow cytometry. Addition of HN protected TNBC cells from various cytotoxic insults, such as serum deprivation, proapoptotic cytokine TNF-α or chemotherapy with DOXO. We next evaluated the role of endogenous HN in the apoptotic response of TNBC cells, using a plasmid encoding a short hairpin RNA to inhibit HN expression (pUC.shHN). To readily assess transduction efficiency, the plasmid also encodes the red fluorescent protein dTomato as a reporter gene. Transfection of TNBC 4T1 tumor cells with pUC.shHN increased the percentage of apoptotic cells when compared to cells transfected with control plasmid, as assessed by flow cytometry after staining with propidium iodide. When transfected 4T1 cells were incubated with different concentrations of DOXO, pUC.shHN reduced their clonogenic capacity. We also evaluated the effect of HN in the progression of experimental mouse 4T1 TNBC treated with DOXO. HN was readily detected in tumor samples and lung metastases. Systemic administration of HN reduced tumor apoptotic rate, accelerated tumor progression and increased the development of lung metastases. In addition, administration of HN impaired the antitumor and antimetastatic effect of chemotherapy. In summary, our findings suggest that HN inhibits the response of TNBC cells to cytotoxic stimuli, facilitating tumor progression and chemoresistance. Thus, blockade of HN could constitute a therapeutic strategy to improve the efficacy of chemotherapy in breast cancer. Citation Format: Camila Zuccato, Mariela A. Moreno Ayala, Maria F. Gottardo, Matias Luis Pidre, Antonela S. Asad, Alejandro J. Nicola Candia, Victor Romanowski, Adriana Seilicovich, Marianela Candolfi. Role of mitochondrial peptide Humanin in the response of experimental breast cancer to chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1951.