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Breast cancer is one of the most frequent of human malignancies, and it is therefore fundamental to identify the underlying molecular mechanisms leading to cancer transformation. Among other causative agents in the development of breast cancers, an important role for reactive oxygen species (ROS) has emerged. However, most studies on the role of ROS in cancer have not reached specific conclusions, and many issues remain controversial. In the present study, we show that methionine sulfoxide reductase A (MsrA), which is known to protect proteins from oxidation and which acts as a ROS scavenger, is down-regulated in a number of breast cancers. Moreover, levels of MsrA correlate with advanced tumor grade. We therefore investigated the functional role of MsrA in breast cancer cells. Our data show that reduction of MsrA levels results in increased cell proliferation and extracellular matrix degradation, and consequently in a more aggressive cellular phenotype, both in vivo and in vitro. We also show that the underlying molecular mechanisms involve increased ROS levels, resulting in reduction of phosphatase and tensin homolog deleted on chromosome ten protein (PTEN), and activation of the phosphoinositide 3-kinase pathway. In addition, MsrA down-regulation results in up-regulation of VEGF, providing additional support for tumor growth in vivo.

Original publication

DOI

10.1073/pnas.1010171107

Type

Journal article

Journal

Proc Natl Acad Sci U S A

Publication Date

26/10/2010

Volume

107

Pages

18628 - 18633

Keywords

Animals, Base Sequence, Breast Neoplasms, Cell Line, Tumor, Cell Proliferation, Down-Regulation, Female, Gene Knockdown Techniques, Humans, Hydrogen Peroxide, Methionine Sulfoxide Reductases, Mice, Mice, Nude, Neoplasm Invasiveness, Neoplasm Transplantation, Phenotype, RNA, Small Interfering, Reactive Oxygen Species, Transplantation, Heterologous, Vascular Endothelial Growth Factor A