Abstract 6124: Recombinant apurinic/apyrimidinic endonuclease-1/redox factor-1 plus acetylsalicylic acid combination therapy inhibits tumorigenesis in an orthotopic xenograft murine model of triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is characterized with hormone receptor negative and frequently exhibits inherently aggressive clinical behavior, resulting in poor prognoses. TNBCs are highly heterogenic, leading to obstacles in identifying new therapeutic targets and performing targeted therapy. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1), a multifunctional protein, is mainly involved in DNA repair and redox regulation; it is upregulated in various cancers and is extracellularly secreted because of hyperacetylation. We previously reported that hyperacetylation induced APE1/Ref-1 release causes apoptosis in TNBCs. In the current study, we aimed to assess the therapeutic efficacy of combination treatment involving recombinant human APE1/Ref-1 (rhAPE1/Ref-1) plus acetylsalicylic acid (ASA) in TNBC xenograft mice. ASA co-treatment was used to induce and lasting acetylation of rhAPE1/Ref-1. For in vivo analysis, we constructed an orthotopic xenograft in vivo model of TNBC by using MDA-MB-231 cells. We performed combination therapy involving intravenous injection of purified rhAPE1/Ref-1 (1 mg/kg) and oral administration of ASA (20 mg/kg) thrice a week for 6 weeks in TNBC xenograft mice. This rhAPE1/Ref-1 plus ASA combination therapy inhibited tumor formation and growth, without damaging liver or kidney tissue, and decreased plasma levels of the cancer marker CEA and breast cancer-specific markers CA27-29 and CA15-3 in the TNBC xenograft mice. The TNBC group, which underwent combination therapy, had more apoptotic cells and greater inflammatory cell infiltration in tumor tissues than the vehicle group did. Additionally, in tumor tissue of TNBC with combination therapy exhibits increased apoptosis following upregulation of Bax, cleaved-caspase-3, and cleaved-PARP. Thus, we found that rhAPE1/Ref-1 plus ASA combination therapy enhanced antitumor effects in TNBCs via inflammatory cell infiltration and apoptosis signaling pathways. Our findings indicate the therapeutic potential of rhAPE1/Ref-1 plus ASA combination therapy for TNBC. Citation Format: Yu Ran Lee, Hee Kyoung Joo, Eun-Ok Lee, Sungmin Kim, Hao Jin, Yeon Hee Choi, Eun Ju Choi, Byeong Hwa Jeon. Recombinant apurinic/apyrimidinic endonuclease-1/redox factor-1 plus acetylsalicylic acid combination therapy inhibits tumorigenesis in an orthotopic xenograft murine model of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6124.