Cancer cells upregulate glycolysis, increasing glucose uptake to meet energy needs. A small fraction of a cell's glucose enters the hexosamine biosynthetic pathway (HBP), which regulates levels of O-linked b-N-acetylglucosamine (O-GlcNAc), a carbohydrate posttranslational modification of diverse nuclear and cytosolic proteins. We discovered that breast cancer cells upregulate the HBP, including increased O-GlcNAcation and elevated expression of O-GlcNAc transferase (OGT), which is the enzyme catalyzing the addition of O-GlcNAc to proteins. Reduction of O-GlcNAcation through RNA interference of OGT in breast cancer cells leads to inhibition of tumor growth both in vitro and in vivo and is associated with decreased cell-cycle progression and increased expression of the cellcycle inhibitor p27 Kip1 . Elevation of p27Kip1 was associated with decreased expression and activity of the oncogenic transcription factor FoxM1, a known regulator of p27 Kip1 stability through transcriptional control of Skp2. Reducing O-GlcNAc levels in breast cancer cells decreased levels of FoxM1 protein and caused a decrease in multiple FoxM1-specific targets, including Skp2. Moreover, reducing O-GlcNAcation decreased cancer cell invasion and was associated with the downregulation of matrix metalloproteinase-2, a known FoxM1 target. Finally, pharmacological inhibition of OGT in breast cancer cells had similar anti-growth and anti-invasion effects. These findings identify O-GlcNAc as a novel mechanism through which alterations in glucose metabolism regulate cancer growth and invasion and suggest that OGT may represent novel therapeutic targets for breast cancer.

The Hexosamine Biosynthetic Pathway leads to elevated post-translation addition of O-linked-βN-acetylglucosamine (O-GlcNAc) on intracellular proteins. Cancer cells elevate total O-GlcNAcylation by increasing O-GlcNAc transferase (OGT) and/or decreasing O-GlcNAcase (OGA) levels. Reducing O-GlcNAcylation in cancer cells inhibits oncogenesis. Here, we demonstrate that O-GlcNAcylation regulates glycolysis in cancer cells via HIF-1α and its transcriptional target GLUT1. Reducing O-GlcNAcylation increases α-ketoglutarate, HIF-1 hydroxylation and interaction with VHL resulting in HIF-1α degradation. Reducing O-GlcNAcylation in cancer cells results in activation of ER stress and apoptosis of cancer cells mediated through CHOP induction of BCL2-family proteins. HIF-1α and GLUT1 are critical for OGT-mediated regulation of metabolic stress as overexpression of stable HIF-1 or GLUT1 rescues metabolic defects and apoptosis. Human basal-like breast cancers with high levels of HIF-1α contain elevated OGT, O-GlcNAcylation and lower OGA levels correlate independently with poor patient outcome. Thus, O-GlcNAcylation regulates cancer cell metabolic reprograming and survival stress signaling via regulation of HIF-1α.

Background: Cancer cells display altered metabolism and expression of the nutrient sensor O-linked ␤-N-acetylglucosamine transferase (OGT). Results: Through regulation of FoxM1, OGT contributes to increased invasion, angiogenesis, and metastasis of prostate cancer cells. Conclusion: OGT plays a critical role in prostate cancer. Significance: OGT may provide a novel therapeutic target for treating prostate cancer.

SUMMARY Highly proliferating cells are particularly dependent on glucose and glutamine for bioenergetics and macromolecule biosynthesis. The signals that respond to nutrient fluctuations to maintain metabolic homeostasis remain poorly understood. Here, we found that mTORC2 is activated by nutrient deprivation due to decreasing glutamine catabolites. We elucidate how mTORC2 modulates a glutamine-requiring biosynthetic pathway, the hexosamine biosynthesis pathway (HBP) via regulation of expression of GFAT1 (glutamine:fructose-6-phosphate amidotransferase 1), the rate-limiting enzyme of the HBP. GFAT1 expression is dependent on sufficient amounts of glutaminolysis catabolites particularly α-ketoglutarate, which are generated in an mTORC2-dependent manner. Additionally, mTORC2 is essential for proper expression and nuclear accumulation of the GFAT1 transcriptional regulator, Xbp1s. Thus, while mTORC1 senses amino acid abundance to promote anabolism, mTORC2 responds to declining glutamine catabolites in order to restore metabolic homeostasis. Our findings uncover the role of mTORC2 in metabolic reprogramming and have implications for understanding insulin resistance and tumorigenesis.

This paper presents an integrated optimal control model that optimizes economic performance of reservoir management in watersheds in which there are significant economic and hydrologic interdependencies. The model is solved using the General Algebraic Modeling System (GAMS). Results show that application of this model to New Mexico's Rio Chama basin can increase total system benefits over historical benefits by exploiting complementarities between hydroelectricity production, instream recreation, and downstream lake recreation.

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ACKNOWLEDGMENTWe thank the MGH tumor bank for their assistance with this project.

A general approach to the speciation of metals present in mixed oxidation states is described. It employs the use of sequential spectrophotometric and atomic-absorption detectors in a flow injection system.The application of this approach is illustrated by two examples.(1) The determination of chromium(V1) and total chromium in corrosion test sea water: this system can operate at up to 120 injections per hour with an injected sample volume of 30yl. The working ranges are 1-50 p.p.m. of total chromium and 0.1-20 p.p.m. of chromium(V1). ( 2) The determination of iron(l1) and total iron in mineral process solutions: this system can also operate at up to 120 injections per hour using either a 20or a 100-yl sample. A 20-$ sample gave linear working ranges of 5-120 p.p.m. of total iron and 0.5-120 p.p.m. of iron(ll), and a 100-yl sample gave working ranges of 0.5-25 p.p.m. of total iron and 0.2-25 p.p.m. of iron(l1).