Breast tumors in PyMT transgenic mice expressing mitochondrial catalase have decreased labeling for macrophages and endothelial cells.

We show by immunohistochemical labeling that prominent cell types in the tumor microenvironment of PyMT transgenic mice are tumor-associated macrophages (TAMs) and endothelial cells, and that both populations are decreased in the presence of mitochondrial targeted catalase (mCAT). This observation suggests that mitochondrial ROS can drive tumor invasiveness in conjunction with the presence of TAMs and increased angiogenesis. Since primary PyMT tumor cells expressing mCAT undergo increased apoptosis, mitochondrial antioxidants might be attractive anti-tumor agents.