Abstract 1352: High-throughput matrix screening reveals synergistic chemotherapeutic combinations with blockade of CD47 to enhance cytotoxicity in breast cancer

CD47 is a widely expressed cell surface receptor that serves as a counter-receptor for SIRPα in recognition of self by the innate immune system. On the other hand CD47 also serves as a signaling receptor for the matricellular protein thrombospondin-1 (TSP-1), regulating cell growth and survival. Clinical studies consistently show that increased expression of CD47 is an independent poor prognosis factor in several types of cancer, including breast cancer. Moreover elevated expression of CD47 is associated with development of resistance to chemotherapy by inhibiting cell death pathways. Therefore, agents targeting CD47 are attractive to overcome therapeutic resistance in breast cancer. Using a high-throughput assay in a 1536-well microplate format we screened a comprehensive set of approved and late stage development oncology drugs in combination with an anti-CD47 morpholino to find combinatorial strategies that are more cytotoxic against breast cancer cells. Potency and efficacy measurements during the primary screen identified compounds that synergized with anti-CD47 to augment their cytotoxicity effect. One of the compound groups that demonstrated increased synergism with CD47 were the anthracycline family of drugs. We further validated these results in a syngeneic model of breast cancer and demonstrated that blockade of CD47 in combination with doxorubicin improves chemotherapeutic response when compared to mice administered doxorubicin alone. Furthermore the anti-tumor response with anti-CD47 combination is associated with a reduction in glycolytic flux and a selective up regulation of mitophagy. Overall this indicates that blockade of CD47 in the clinic may synergize with chemotherapeutic strategies to improve patient curative responses. Citation Format: David D. Roberts, Ashley Smith, John M. Sipes, Adam Wilson, Lesley Mathews-Griner, Rajarshi Guha, Craig J. Thomas, Marc Ferrer, David R. Soto-Pantoja. High-throughput matrix screening reveals synergistic chemotherapeutic combinations with blockade of CD47 to enhance cytotoxicity in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1352.