Abstract 1078: Hypoxic microenvironment promotes resistance to targeted therapies in HER2-overexpressing breast cancer involving epithelial-to-mesenchymal transition features

Trastuzumab and trastuzumab emtansine (T-DM1) targeted therapies are the main choice for the treatment of HER2-overexpressing breast cancer patients. However, de novo or acquired resistance is still the major obstacle in clinical practice. It has been shown that several pathways, including HER2, can lead to HIF-α stabilization in breast cancer cells. Thus, the purpose of our study was to analyse the effect of hypoxia in acquired resistance to anti-HER2 therapies. We used HER2-overexpressing BT-474 and non-overexpressing MCF-7 human breast cancer cell lines. As an acute hypoxia model, we added CoCl2 (100 µM) to cell culture medium. The hypoxic status of the cells was evaluated by a Western blot analysis, showing a peak of HIF-1α expression after 6 hours of CoCl2 exposure. This result correlated with VEGF induction, as measured by RT-qPCR (p Citation Format: Virginia Judith Wolos, Ivana Jaqueline Tapia, Marianela Abrigo, Ezequiel Lacunza, Elisa Dora Bal de Kier Joffe, Gabriel Leon Fiszman. Hypoxic microenvironment promotes resistance to targeted therapies in HER2-overexpressing breast cancer involving epithelial-to-mesenchymal transition features [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1078.