Redox Regulation Of Tumor Cell Heterogeneity In The Pymt Mammary Tumor Model Revealed By Single Cell Rna Sequencing

Tumor heterogeneity is known to drive breast cancer progression and metastasis. Current therapies target mostly inter-tumor heterogeneity (different patients) without taking into consideration intratumor heterogeneity (individual tumor). Hypoxia is a hallmark of aggressive tumors that is known to select for intratumor cells that are prone for metastasis. Here we show that knockdown of a ROS scavenging enzyme, Glutathione Peroxidase 2, in the PyMT mammary tumor model results in highly hypoxic and metastatic tumors. Single cell RNA-seq on both GPx2 knockdown and control tumors revealed a high degree of intratumor heterogeneity resulting in several clusters that were either of luminal/epithelial or basal-like/mesenchymal type shared by both tumors. Interestingly, GPx2 loss caused increases in a mesenchymal-like/quiescent and a highly proliferative luminal population, implying that GPx2 loss might drive a cancer stem-like population that is conducive of metastasis. Metascape pathway analysis of differentially expressed genes identified pathways that were significantly overrepresented in GPx2 knockdown tumors involving mitochondrial oxidative phosphorylation and response to hypoxia, consistent with the high levels of reactive oxygen species in these tumors. Finally, differential gene expression analysis on mesenchymal and luminal subpopulations predicts novel candidate gene signatures stimulated by GPx2 loss, that might be used to identify or target metastatic cells in tumors. In sum, our data imply that oxidative stress conveys a metastatic phenotype via effects on tumor cell heterogeneity. Citation Format: Zuen Ren, Malindrie Dharmaratne, Ameya Kulkarni, Atefeh Taherian Fard, Jessica Mar, Phillip M. Galbo, Yang Liu, Deyou Zheng, Huizhi Liang, Outhiriaradjou Benard, Kimita Suyama, Michael B. Prystowsky, Larry Norton, Rachel B. Hazan. Redox regulation of tumor cell heterogeneity in the PyMT mammary tumor model revealed by single cell RNA sequencing [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4426.