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The leading cause of death in cancer patients is metastasis, for which an effective treatment is still necessary. During metastasis, cancer cells aberrantly express several glycans that are correlated with poor patient outcome. This study was aimed toward exploring the effects of O-GlcNAcylation on membranous N-glycans that are associated with the progression of cholangiocarcinoma (CCA). Global O-GlcNAcylation in CCA cells was depleted using specific siRNA against O-GlcNAc transferase (OGT), which transfers GlcNAc to the acceptor proteins. Using an HPLC-Chip/Time-of-Flight (Chip/TOF) MS system, the N-glycans associated with O-GlcNAcylation were identified by comparing the membranous N-glycans of siOGT-treated cells with those of scramble siRNA-treated cells. In parallel, the membranous N-glycans of the parental cells (KKU-213 and KKU-214) were compared with those of the highly metastatic cells (KKU-213L5 and KKU-214L5). Together, these data revealed that high mannose (Hex9HexNAc2) and biantennary complex (Hex5HexNAc4Fuc1NeuAc1) N-linked glycans correlated positively with metastasis. We subsequently demonstrate that suppression of O-GlcNAcylation decreased the expression of these two N-glycans, suggesting that O-GlcNAcylation mediates their levels in CCA. In addition, the ability of highly metastatic cells to migrate and invade was reduced by the presence of Pisum Sativum Agglutinin (PSA), a mannose-specific lectin, further indicating the association of high mannose type N-glycans with CCA metastasis. The molecular mechanism of O-GlcNAc-mediated progression of CCA was shown to proceed via a series of signaling events, involving the activation of Akt/Erk (i), an increase in FOXO3 phosphorylation (ii), which results in the reduction of MAN1A1 expression (iii) and thus the accumulation of Hex9HexNAc2 N-glycans (iv). This study demonstrates for the first time the association between O-GlcNAcylation, high mannose type N-glycans, and the progression of CCA metastasis, suggesting a novel therapeutic target for treatment of metastatic CCA.

Two novel estrogen receptor ß (ERß) mRNA isoforms that diverge in their 5'-untranslated regions, ERß mRNA (0K-1) and ERß mRNA (0N-1), have recently been identified. This indicates that transcription of the human ERß gene occurs from at least two different promoters, named promoter 0K and promoter 0N. The aim of this study was to investigate the expression of ERß isoforms in primary cultures of normal breast epithelial cells, a panel of breast cancer cell lines and in normal breast and breast cancer tissues; and to examine whether methylation of the two ERß promoters is involved in regulation of ERß gene expression. Using quantitative real-time PCR techniques, we found that ERß mRNA levels were significantly lower in breast cancer cell lines than in primary cultures of normal breast epithelial cells. Bisulfite genomic sequencing analysis revealed that two promoters of the ERß gene exhibit distinct methylation patterns. Promoter 0N was unmethylated in normal breast epithelial cells, but extensively methylated in breast cancer cell lines. In contrast, promoter 0K was unmethylated in both normal and malignant breast epithelial cells. We demonstrated a significant correlation between promoter 0N hypermethylation and loss of ERß mRNA expression in breast cancer cell lines. Treatment of breast cancer cells with demethylating agent effectively reactivated the expression of ERß mRNA. The observations from the cell lines were also reflected in primary breast cancer tumors. Thus, expression of ERß mRNA in breast tumors was found to be inversely associated with the degree of methylation of promoter 0N. Our results suggest that a decreased level of ERß mRNA may be associated with breast tumorigenesis, and that DNA methylation is an important mechanism for ERß gene silencing in breast cancer.Oncogene (2003) 22, 7600-7606. doi:10.1038/sj.onc.1207100 [ABSTRACT FROM AUTHOR]

Cross-linking of the B cell antigen receptor (BCR) on immature WEHI 231 B cells results in G1 cell cycle arrest and apoptosis. Here we investigated the molecular mechanisms that are necessary and sufficient for these changes to occur. We show that BCR stimulation of WEHI 231 cells results in down-regulation of cyclin D2 and up-regulation of p27Kip1, which are associated with pocket protein hypophosphorylation and E2F inactivation. Ectopic expression of p27Kip1 by TAT-fusion protein or retroviral transduction is sufficient to cause G1 cell cycle arrest, followed by apoptosis. In contrast, over-expression of cyclin D2 overcomes the cell cycle arrest and apoptosis induced by anti-IgM, indicating that down-regulation of cyclin D2 is necessary for the cell cycle arrest and apoptosis activated by BCR stimulation. Thus, cyclin D2 and p27Kip1 have opposing roles in these pathways and our data also suggest that cyclin D2 functions upstream of p27Kip1 and the pRB pathway and therefore plays an essential part in integrating the signals from BCR with the cell cycle machinery. We next investigated which signal transduction pathways triggered by the BCR regulate cell proliferation and apoptosis via cyclin D2 and p27Kip1. Inhibition of PI3-K signalling by LY294002 down-regulated cyclin D2 and up-regulated p27Kip1 expression at both protein and RNA levels, mimicking the effects of BCR-stimulation. Furthermore, ectopic expression of a constitutively active form of AKT blocked the cell cycle arrest and apoptosis triggered by anti-IgM and also abrogated down-regulation of cyclin D2 and up-regulation of p27Kip1 expression induced by BCR-engagement. These results indicate that BCR activation targets p27Kip1 and cyclin D2 to mediate cell cycle arrest and apoptosis and that down-regulation of PI3-K/AKT activity post BCR stimulation is necessary for these to occur. Oncogene (2001) 20, 7352–7367. [ABSTRACT FROM AUTHOR]