Targeting CARP-1 in breast cancer to decrease tumor growth and enhance immunogenicity

Abstract

Abstract Natural killer T (NKT) cells are important in antitumor immunity, but these cells are significantly reduced in breast cancer (BC) patients. The tumor-associated factors that lead to the reduction in NKT cells are unclear; however, it is known that during malignancy BCs upregulate pro-survival proteins in order to proliferate and evade immune detection. Cell Cycle and Apoptosis Regulatory Protein (CARP)-1, a perinuclear phosphoprotein that regulates cell growth and apoptosis, is overexpressed in chemotherapy-treated cancers and several BC cell lines, such as MCF-7. CARP functional mimetics (CFMs) are small molecule inhibitors that interfere with the interaction of CARP-1 and the anaphase promoting complex, causing cell cycle arrest and apoptosis. Thus, we hypothesize that targeting CARP-1 through the use of CFMs will induce apoptosis and restore anti-tumor immune responses. In this study, BC cell lines were treated with CFM-4&5 and proliferation, cytotoxicity, and immunogenicity were assessed. It was found that pretreatment of human MCF-7 and murine E0771 BC lines with 20μM CFM-4&5 resulted in 80–100% cell death within 48–72h. In order to assess immunogenicity in the absence of cytotoxicity, BC cell lines were pretreated with 10μm for 24h, washed and cultured in fresh medium. Conditioned medium was collected and used to treat CD1d-expressing cells for 4h prior to coculture with NKT cell hybridomas. To test the effects of CFMs on immune cell activation, peripheral blood mononuclear cells (PBMC) from healthy and BC patients were treated with CFM-4&5 in the presence of stimuli and immuno-activity was assessed by ELISA. Collectively, these data implicate a novel role for targeting CARP-1 for the treatment of BC.