Abstract 1267: Metabolic sensor O-GlcNAc Transferase is a novel regulator of prostate cancer invasion and angiogenesis via regulation of FoxM1

Abstract

Abstract Cancer cells universally increase glucose and glutamine consumption, leading to the altered metabolic state known as the Warburg effect. One metabolic pathway highly dependent on glucose and glutamine is the Hexosamine Biosynthetic Pathway (HBP). Increased flux through the HBP leads to increases in the post-translational addition of O-linked-β-N-acetylglucosamine (O-GlcNAc) on a diverse population of nuclear and cytosolic proteins. A number of these target proteins are implicated in cancer, yet the role of O-GlcNAc modifications in cancer remains poorly defined. Here, we show that OGT is overexpressed in prostate cancer tissue compared to normal prostate epithelium and, that OGT protein and O-GlcNAc levels are elevated in prostate carcinoma cell lines compared to non-transformed prostate cells. Decreasing O-GlcNAc levels using OGT-targeted RNAi in the metastatic prostate cancer cell line PC3-ML inhibited growth in three-dimensional (3D) culture, as well as decreased colony formation in soft agar assays. Furthermore, decreasing O-GlcNAc levels was also associated with cell cycle arrest at G1 and increased expression of the CDK inhibitors p27 and p21. However, reducing O-GlcNAc levels in the non-tumorigenic prostate epithelial cell line RWPE-1 had minimal effects on growth in 3D culture. In addition to growth inhibition, reducing O-GlcNAcation in PC3-ML cells was associated with reduced expression of matrix metalloproteinase-2 (MMP-2), MMP-9 and vascular endothelial growth factor (VEGF), resulting in the inhibition of invasion and angiogenesis. OGT regulation of invasion and angiogenesis was dependent upon regulation of the oncogenic transcription factor FoxM1, as reducing OGT expression led to increased FoxM1 proteasomal degradation. Moreover, overexpression of a FoxM1 degradation-resistant mutant abrogated OGT RNAi inhibition of invasion, MMP levels, as well as angiogenesis and VEGF expression. Finally, the use of novel second-generation small molecule inhibitor of OGT led to the similar reduction in growth, invasion and inhibition of MMPs and VEGF levels. Current experiments are underway to test whether targeting OGT blocks prostate cancer metastasis. Altogether, these data suggest that as prostate cancer cells alter glucose and glutamine levels, O-GlcNAcation serves as nutrient sensitive modification contributing to oncogenesis and suggest that OGT is positioned as a novel target for therapeutic intervention for the treatment of human prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1267. doi:10.1158/1538-7445.AM2011-1267