Overexpression of the RNA binding protein HuR impairs tumor growth in triple negative breast cancer associated with deficient angiogenesis

• Published in: Cell cycle (Georgetown, Tex.) Vol. 9; no. 16; pp. 3357 - 3366
• Main Authors: Gubin, Matthew M, Calaluce, Robert, Davis, Justin Wade, Magee, Joseph D, Strouse, Connie S., Shaw, Daniel P., Ma, Lixin, Brown, Ashley, Hoffman, Timothy, Rold, Tammy L., Atasoy, Ulus
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 15.08.2010; Landes Bioscience
• Subjects: Animals; Antigens, Surface - genetics; Antigens, Surface - metabolism; Antigens, Surface - physiology; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors - metabolism; Binding; Biology; Bioscience; Breast Neoplasms - blood supply; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Calcium; Cancer; Cell; Cell Line, Tumor; Cycle; ELAV Proteins; ELAV-Like Protein 1; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Landes; Mice; Mice, Nude; Neovascularization, Pathologic - metabolism; Organogenesis; Proteins; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; RNA, Messenger - metabolism; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; RNA-Binding Proteins - physiology; Thrombospondin 1 - metabolism; Transplantation, Heterologous; Vascular Endothelial Growth Factor A - metabolism
• ISSN: 1538-4101; 1551-4005
• DOI: 10.4161/cc.9.16.12711

Interactions between RNA binding proteins (RBPs) and genes are not well understood, especially in regulation of angiogenesis. The RBP HuR binds to the AU-rich (ARE) regions of labile mRNAs, facilitating their translation into protein and has been hypothesized to be a tumor-maintenance gene. Elevated levels of cytoplasmic HuR directly correlate with increased invasiveness and poor prognosis for many cancers, including those of the breast. HuR controls the expression of multiple genes involved in angiogenesis including VEGFa, HIF1a, and thrombospondin 1 (TSP1). We investigated the role of HuR in estrogen receptor negative (ER-) breast cancer. MDA-MB-231 cells with higher levels of HuR have alterations in cell cycle kinetics and faster growth. Unexpectedly, HuR overexpression significantly interfered with tumor growth in orthotopic mouse models. The putative mechanism seems to be an anti-angiogenetic effect by increasing expression of TSP1 but also surprisingly, down-regulation of VEGF, a target of HuR which it normally increases. Our findings reveal that HuR may be regulating a cluster of genes involved in blood vessel formation which controls tumor angiogenesis. An approach of modulating HuR levels may overcome limitations associated with monotherapies targeting tumor vessel formation.