LAUSR

Breast tumors are known to undergo high levels of mitochondrial oxidative phosphorylation leading to accumulation of reactive oxygen species (ROS), which in turn potentiate cancer stem cells and chemoresistance. This was shown to be due to HIF1α stabilization by ROS; however, the signaling events downstream of HIF1α regulating the cancer stem cell (CSC) phenotype remain unknown. Kaplan Meier survival curves upon the gene profiling database of breast cancer patients showed that reduced levels of the ROS scavenging enzyme, glutathione peroxidase 2 (GPx2) in breast cancers was associated with shorter patient survival duration. Consistent with this idea, we found that GPx2 was downregulated in metastatic mammary tumor cells, suggesting GPx2 loss enhances metastasis. Indeed, GPx2 knockdown in poorly metastatic cells increased ROS production, shortened tumor latency, and stimulated dramatic mammary tumor growth and metastasis. These effects were associated with marked increases in angiogenesis, CSC-like properties, and chemoresistance. Here, we show that GPx2 downregulation in mammary epithelial cells increases ROS production and HIF1α stabilization which were accompanied by VEGF upregulation and enhanced angiogenesis. On the other hand, GPx2 loss caused dramatic mammosphere formation and resistance to doxorubicin, implying effects on stemness leading to chemoresistance. These data suggest that GPx2 loss is a critical event that drives mammary tumorigenesis and metastasis via HIF1α signaling leading to stimulation of angiogenesis and stemness properties. Understanding the ramifications of GPx2 loss in breast cancer will allow us to identify key regulators of stemness and chemoresistance, with the goal of identifying novel drug targets in metastasis. Citation Format: Zuen Ren, Huizhi Liang, Outhiriaradjou Benard, Kimita Suyama, Joseph M. Albanese, Larry Norton, Wei Zheng, Rachel B. Hazan. Gluthathione peroxidase 2 downregulation in the PyMT mammary tumor model leads to an aggressive phenotype due to stimulation of angiogenesis and tumor stemness via HIF1 alpha signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1993.