Abstract 3900: in Vivo Inhibition of Metastatic HER2 Positive Trastuzumab Resistant Breast Cancer Using Engineered Destabilized 3UTR ARE of HER2 Improves Survival Outcomes

Breast cancer is the most common form of cancer in women with mortality of about 58% in developing countries. HER2+ breast cancers are treated with trastuzumab in various forms in combination with chemotherapy and has been successful in targeting HER2 overexpression in HER2+ breast cancer and improving survival as a standard first line therapy for more than a decade. However, about 25% of early and 75% of late stage HER2 driven breast cancers are resistant to trastuzumab. For these patients, the clinical outcomes are grim. We report the destabilization of HER2 3‘UTR ARE which degraded oncogene HER2 transcript, protein expression, HER2 dependent kinases and interactome. In vitro, we transfected the engineered destabilizing HER2 constructs into BT474 clone 5 trastuzumab resistant breast cancer and within days, we inhibited cancer cell growth and degraded HER2 transcript and protein. The degradation of HER2 leads to loss of many kinases especially YES1 and WNK1 that are known causes of chemoresistance in HER2 positive trastuzumab resistant breast cancer. In vivo, we administered the destabilizing constructs as naked constructs or as complexed with nanocages to mice bearing tumors of BT474 clone 5 trastuzumab resistant cells. We found that our constructs, both the naked and nanocage-delivered, conferred significant survival (p values: 0.0178 and 0.00492) to about 60% of the exceptionally surviving mice compared to the controls. Taken together, we have developed a new therapy to target trastuzumab resistant HER2+ metastatic breast cancers with increased survival outcomes. Citation Format: Chidiebere U. Awah, Joo Sun Mun, Baris Boylu, Alooka Paragodaarachchi, Chika Ochu, Hiroshi Matsui, Olorunseun O. Ogunwobi. In vivo inhibition of metastatic HER2 positive trastuzumab resistant breast cancer using engineered destabilized 3UTR ARE of HER2 improves survival outcomes. [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 3900.