Inhibition of angiogenesis is an important new modality for cancer treatment. 2-methoxyestradiol (2ME2) is a novel antitumor and antiangiogenic agent, currently in clinical trials, whose molecular mechanism of action remains unclear. Herein, we report that 2ME2 inhibits tumor growth and angiogenesis at concentrations that efficiently disrupt tumor microtubules (MTs) in vivo. Mechanistically, we found that 2ME2 downregulates hypoxia-inducible factor-1 (HIF) at the posttranscriptional level and inhibits HIF-1-induced transcriptional activation of VEGF expression. Inhibition of HIF-1 occurs downstream of the 2ME2/tubulin interaction, as disruption of interphase MTs is required for HIF-alpha downregulation. These data establish 2ME2 as a small molecule inhibitor of HIF-1 and provide a mechanistic link between the disruption of the MT cytoskeleton and inhibition of angiogenesis.

Neoplastic lesions typically express specific carbohydrate antigens on glycolipids, mucins, and other glycoproteins. Such antigens are often under epigenetic control and are subject to reversion and loss upon therapeutic selective pressure. We report here that two of the most common tumor-associated carbohydrate antigens, Tn and sialyl Tn (STn), result from somatic mutations in the gene Cosmc that encodes a molecular chaperone required for formation of the active T-synthase. Diverse neoplastic lesions, including colon cancer and melanoma-derived cells lines, expressed both Tn and STn antigen due to loss-of-function mutations in Cosmc. In addition, two human cervical cancer specimens that showed expression of the Tn/STn antigens were also found to have mutations in Cosmc and loss of heterozygosity for the cross-linked Cosmc locus. This is the first example of somatic mutations in multiple types of cancers that cause global alterations in cell surface carbohydrate antigen expression. [Cancer Res 2008;68(6):1636-46]

CXC chemokine receptor 4 (CXCR4) has been shown to play a critical role in chemotaxis and homing, which are key steps in cancer metastasis. There is also increasing evidence that links this receptor to angiogenesis; however, its molecular basis remains elusive. Vascular endothelial growth factor (VEGF), one of the major angiogenic factors, promotes the formation of leaky tumor vasculatures that are the hallmarks of tumor progression. Here, we investigated whether CXCR4 induces the expression of VEGF through the PI3K/Akt pathway. Our results showed that CXCR4/ CXCL12 induced Akt phosphorylation, which resulted in upregulation of VEGF at both the mRNA and protein levels. Conversely, blocking the activation of Akt signaling led to a decrease in VEGF protein levels; blocking CXCR4/CXCL12 interaction with a CXCR4 antagonist suppressed tumor angiogenesis and growth in vivo. Furthermore, VEGF mRNA levels correlated well with CXCR4 mRNA levels in patient tumor samples. In summary, our study demonstrates that the CXCR4/ CXCL12 signaling axis can induce angiogenesis and progression of tumors by increasing expression of VEGF through the activation of PI3K/Akt pathway. Our findings suggest that targeting CXCR4 could provide a potential new anti-angiogenic therapy to suppress the formation of both primary and metastatic tumors.

Tissue hypoxia is a common feature in solid tumors. Hypoxia-inducible factor 1 (HIF-1) is a critical transcription factor that regulates the expression of genes encoding factors that influence tumor growth including vascular endothelial growth factor. Previous studies have demonstrated that post-transcriptional modification events are important for regulation of HIF-1␣ protein expression and HIF-1 transcriptional activity. Prostaglandin E 2 (PGE 2 ), a major end product of the cyclooxygenase-2 (COX-2) enzyme, induces the basal and hypoxia-induced nuclear relocalization of HIF-1␣. This is suppressed by NS398, a COX-2 selective inhibitor. NS398 also inhibits hypoxia-induced angiogenesis, which may be mediated by the inhibition of HIF-1 function in a COX-2-dependent manner. Here, we show that NS398 reduces HIF-1␣ and HIF-1 transcriptional function in both COX-2 positive PC-3 cells and COX-2 negative HCT116 cells under normoxic and hypoxic conditions. On the one hand, NS398 decreases the expression of HIF-1␣ mRNA and reduces HIF-1␣ synthesis in a COX-2/PGE 2 dependent way, which can be restored by addition of exogenous PGE 2 that activates the phosphatidylinositol 3-kinase/AKT/p70 s6k signaling pathway. On the other hand, NS398 accelerates HIF-1␣ degradation by moderately increasing ubiquitination and remarkably promoting the clearance of ubiquitylated protein, an effect most likely independent of COX-2/PGE 2 since exogenous PGE 2 fails to reverse it. Finally, NS398 decreases hypoxia-induced shifted form of HIF-1␣ and attenuates HIF-1 activation in greater extent under hypoxic than normoxic conditions. These data not only confirm the inhibitory effect of NS398 on HIF-1␣ and HIF-1 transcriptional activity but also demonstrate that such an effect occurs at multiple levels involving both COX-2 dependent and independent mechanisms. © 2004 Wiley-Liss, Inc. Key words: cell hypoxia, hypoxia-inducible factor-1␣; nonsteroidal anti-inflammatory drugs; cyclooxygenase-2; prostaglandin E 2 ; vascular endothelial growth factor; angiogenesis; protein ubiquitinationThe role of hypoxia-inducible factor 1 (HIF-1) in angiogenesis and cellular adaptation to decreased oxygen availability has been well-established. 1-3 HIF-1 is composed of HIF-1␣ and HIF-1␤ subunits, both of which are members of the basic helix-loop-helix (bHLH)-PAS (PER, ARNT, SIM) protein family. 4 HIF-1␣ is inducible by low O 2 tension and growth factor, while HIF-1␤ is constitutively expressed. HIF-1 initiates transcriptional activity by forming a HIF-1␣/HIF-1␤ heterodimer and binding to hypoxia response elements (HRE) located in the promoter regions of HIF-1-regulated genes, 5,6 including the gene that encodes vascular endothelial growth factor (VEGF). 7 Interaction between HIF-1␣ transactivation domains and coactivators ensures the transcriptional activation of HIF-1. 8,9 Under normoxic conditions, the oxygen-dependent degradation domain (ODDD) of HIF-1␣ interacts with the von Hippel-Lindau protein (pVHL) that is the recognition component of an E3 ubiquitin-protein...

Glycan microarray technology has become a successful tool for studying protein-carbohydrate interactions, but a limitation has been the laborious synthesis of glycan structures by enzymatic and chemical methods. Here we describe a new method to generate quantifiable glycan libraries from natural sources by combining widely used protease digestion of glycoproteins and Fmoc chemistry. Glycoproteins including chicken ovalbumin, bovine fetuin, and horseradish peroxidase (HRP) were digested by pronase, protected by FmocCl, and efficiently separated by 2D-HPLC. We show that glycans from HRP glycopeptides separated by HPLC and fluorescence monitoring retained their natural reducing end structures, mostly core α1,3-fucose and core α1,2-xylose. After simple Fmoc-deprotection, the glycans were printed on NHS-activated glass slides. The glycans were interrogated using plant lectins and antibodies in sera from mice infected with Schistosoma mansoni, which revealed the presence of both IgM and IgG antibody responses to HRP-glycopeptides. This simple approach to glycopeptide purification and conjugation allows for the development of natural glycopeptide microarrays without the need to remove and derivatize glycans and potentially compromise their reducing end determinants.