Transfection of the c-erbB2/neu gene upregulates the expression of sialyl Lewis X, alpha1,3-fucosyltransferase VII, and metastatic potential in a human hepatocarcinoma cell line

Posttranslational Modifications in Thyroid Cancer: Implications for Pathogenesis, Diagnosis, Classification, and Treatment

There is evidence that posttranslational modifications, including phosphorylation, acetylation, methylation, ubiquitination, sumoylation, glycosylation, and succinylation, may be involved in thyroid cancer. We review recent reports supporting a role of posttranslational modifications in the tumorigenesis of thyroid cancer, sensitivity to radioiodine and other types of treatment, the identification of molecular treatment targets, and the development of molecular markers that may become useful as diagnostic tools. An increased understanding of posttranslational modifications may be an important supplement to the determination of alterations in gene expression that has gained increasing prominence in recent years.

Lectin drug conjugate therapy for colorectal cancer

Drug resistance represents an obstacle in colorectal cancer (CRC) treatment because of its association with poor prognosis. rBC2LCN is a lectin isolated from Burkholderia that binds cell surface glycans that have fucose moieties. Because fucosylation is enhanced in many types of cancers, this lectin could be an efficient drug carrier if CRC cells specifically present such glycans. Therefore, we examined the therapeutic efficacy and toxicity of lectin drug conjugate therapy in CRC mouse xenograft models. The affinity of rBC2LCN for human CRC cell lines HT-29, LoVo, LS174T, and DLD-1 was assessed in vitro. The cytocidal efficacy of a lectin drug conjugate, rBC2LCN-38 kDa domain of pseudomonas exotoxin A (PE38) was evaluated by MTT assay. The therapeutic effects and toxicity for each CRC cell line-derived mouse xenograft model were compared between the intervention and control groups. LS174T and DLD-1 cell lines showed a strong affinity for rBC2LCN. In the xenograft model, the tumor volume in the rBC2LCN-PE38 group was significantly reduced compared with that using control treatment alone. However, the HT-29 cell line showed weak affinity and poor therapeutic efficacy. No significant toxicities or adverse responses were observed. In conclusion, we demonstrated that rBC2LCN lectin binds CRC cells and that rBC2LCN-PE38 significantly suppresses tumor growth in vivo. In addition, the efficacy of the drug conjugate correlated with its binding affinity for each CRC cell line. These results suggest that lectin drug conjugate therapy has potential as a novel targeted therapy for CRC cell surface glycans.

FUT7 promotes the malignant transformation of follicular thyroid carcinoma through α1,3-fucosylation of EGF receptor

Aberrant protein glycosylation is involved in many diseases including cancer. This study investigated the role of fucosyltransferase VII (FUT7) in the progression of follicular thyroid carcinoma (FTC). FUT7 expression was found to be upregulated in FTC compared to paracancerous thyroid tissue, and in FTC with T2 stage of TMN classification compared to FTC with T1 stage. FUT7 overexpression promoted cell proliferation, epithelial-mesenchymal transition (EMT), and the migration and invasion of primary FTC cell line FTC-133. Consistently, FUT7 knock-down inhibited cell proliferation, EMT, as well as the migration and invasion of the metastatic FTC cell line FTC-238. Mechanistic investigation revealed that FUT7 catalyzed the α1,3-fucosylation of epidermal growth factor receptor (EGFR) in FTC cells. The extent of glycan α1,3-fucosylation on EGFR was positively correlated with the activation of EGFR in the presence/absence of epidermal growth factor (EGF) treatment. Furthermore, FUT7 was shown to enhance EGF-induced progression of FTC cells through mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways. These findings provide a new perspective on FUT7 that may be a novel diagnostic and therapeutic target of FTC.

The Diverse Contributions of Fucose Linkages in Cancer

Fucosylation is a post-translational modification of glycans, proteins, and lipids that is responsible for many biological processes. Fucose conjugation via α(1,2), α(1,3), α(1,4), α(1,6), and O'- linkages to glycans, and variations in fucosylation linkages, has important implications for cancer biology. This review focuses on the roles that fucosylation plays in cancer, specifically through modulation of cell surface proteins and signaling pathways. How L-fucose and serum fucosylation patterns might be used for future clinical diagnostic, prognostic, and therapeutic approaches will be discussed.

ST3Gal III modulates breast cancer cell adhesion and invasion by altering the expression of invasion-related molecules

Changes in the carbohydrate structure on the surface of tumor cells is an important feature of cancer metastasis. The specific role of sialic acids in the glycoconjugate terminal has not yet been clearly elucidated in these processes. Previously, we reported that α2,3-sialic acid residues in breast cancer are associated with metastatic potential. The α2,3-sialyltransferase ST3Gal III, which adds α2,3-sialic acids to glycoproteins, is overexpressed in various tumors, and enzyme activity is correlated with tumor metastasis, yet its mechanistic role has not been fully evaluated. In the present study, we aimed to investigate the influence of ST3Gal III on key steps in the process of breast cancer metastasis. ST3Gal III-overexpressing and ST3Gal III-silenced breast cancer MDA-MB-231 cell lines were generated. They showed an increase or decrease in the tumor-associated antigen sialyl-Lewis X (SLeX). The E-selectin binding capacity of the transfectants was proportional to cell surface SLeX levels. Cell migration and invasion were positively correlated with ST3Gal III levels. Moreover, ST3Gal III expression modulated the protein expression of invasion-related molecules, including β1 integrin, matrix metalloproteinase (MMP)-2, MMP-9 and cyclooxygenase-2, which may account for the mechanism involved in the effects of ST3Gal III on breast cancer invasiveness. In conclusion, our findings in these novel models of ST3Gal III expression revealed a critical requirement for ST3Gal III in several steps of breast cancer metastasis. ST3Gal III modulates breast cancer cell adhesion and invasion by altering the expression of invasion-related molecules. This study provides novel insights into the mechanisms underlying metastasis and suggests a new target for the effective drug treatment of breast cancer metastasis.

Relationship Between Increased Fucosylation and Metastatic Potential in Colorectal Cancer

BACKGROUND

Fucose is utilized for the modification of different molecules involved in blood group determination, immunological reactions, and signal transduction pathways. We have recently reported that enhanced activity of the fucosyltransferase 3 and/or 6 promoted TGF-ß-mediated epithelial mesenchymal transition and was associated with increased metastatic potential of colorectal cancer (CRC), suggesting that fucose is required by CRC cells. With this in mind, we examined requirement of L-fucose in CRC cells and developed fucose-bound nanoparticles as vehicles for delivery of anticancer drugs specific to CRC.

METHODS

In this study, we first examined the expression of fucosylated proteins in 50 cases of CRC by immunochistochemical staining with biotinylated Aleuria aurantia lectin (AAL). Then we carried out an L-fucose uptake assay using three CRC cell lines. Finally, we developed fucose-bound nanoparticles as vehicles for the delivery of an anticancer drug, SN38, and examined tumor growth inhibition in mouse xenograft model (n = 6 mice per group). All statistical tests were two-sided.

RESULTS

We found a statistically significant relationship between vascular invasion, clinical stage, and intensity score of AAL staining (P≤ .02). L-fucose uptake assay revealed that L-fucose incorporation, as well as fucosylated protein release, was high in cells rich in fucosylated proteins. L-fucose-bound liposomes effectively delivered Cy5.5 into CRC cells. The excess of L-fucose decreased the efficiency of Cy5.5 uptake through L-fucose-bound liposomes, suggesting an L-fucose receptor dependency. Intravenously injected, L-fucose-bound liposomes carrying SN38 were successfully delivered to CRC cells, mediating efficient tumor growth inhibition (relative tumor growth ratio: no treatment group [NT], 8.29 ± 3.09; SN38-treated group [SN38], 3.53 ± 1.47; liposome-carrying, SN38-treated group [F0], 3.1 ± 1.39; L-fucose-bound, liposome-carrying, SN38-treated group [F50], 0.94 ± 0.89; F50 vs NT,P= .003; F50 vs SN38,P= .02, F50 vs F0,P= .04), as well as prolonging survival of mouse xenograft models (log-rank test,P< .001).

CONCLUSIONS

Thus, fucose-bound liposomes carrying anticancer drugs provide a new strategy for the treatment of CRC patients.

Erbb2 up-regulation of ADAM12 expression accelerates skin cancer progression

Solar ultraviolet (UV) radiation can cause severe damage to the skin and is the primary cause of most skin cancer. UV radiation causes DNA damage leading to mutations and also activates the Erbb2/HER2 receptor through indirect mechanisms involving reactive oxygen species. We hypothesized that Erbb2 activation accelerates the malignant progression of UV-induced skin cancer. Following the induction of benign squamous papillomas by UV exposure of v-ras(Ha) transgenic Tg.AC mice, mice were treated topically with the Erbb2 inhibitor AG825 and tumor progression monitored. AG825 treatment reduced tumor volume, increased tumor regression, and delayed the development of malignant squamous cell carcinoma (SCC). Progression to malignancy was associated with increased Erbb2 and ADAM12 (A Disintegin And Metalloproteinase 12) transcripts and protein, while inhibition of Erbb2 blocked the increase in ADAM12 message upon malignant progression. Similarly, human SCC and SCC cell lines had increased ADAM12 protein and transcripts when compared to normal controls. To determine whether Erbb2 up-regulation of ADAM12 contributed to malignant progression of skin cancer, Erbb2 expression was modulated in cultured SCC cells using forced over-expression or siRNA targeting, demonstrating up-regulation of ADAM12 by Erbb2. Furthermore, ADAM12 transfection or siRNA targeting revealed that ADAM12 increased both the migration and invasion of cutaneous SCC cells. Collectively, these results suggest Erbb2 up-regulation of ADAM12 as a novel mechanism contributing to the malignant progression of UV-induced skin cancer. Inhibition of Erbb2/HER2 reduced tumor burden, increased tumor regression, and delayed the progression of benign skin tumors to malignant SCC in UV-exposed mice. Inhibition of Erbb2 suppressed the increase in metalloproteinase ADAM12 expression in skin tumors, which in turn increased migration and tumor cell invasiveness.

α2,3-Sialyltransferase ST3Gal IV promotes migration and metastasis in pancreatic adenocarcinoma cells and tends to be highly expressed in pancreatic adenocarcinoma tissues

Sialyltransferases have received much attention recently as they are frequently up-regulated in cancer cells. However, the role played by each sialyltransferase in tumour progression is still unknown. α2,3-Sialyltransferases ST3Gal III and ST3Gal IV are involved in sialyl-Lewis(x) (SLe(x)) synthesis. Given that the role of ST3Gal III in pancreatic adenocarcinoma cells has been previously reported, in this study we have focused on investigating the role of ST3Gal IV in the acquisition of adhesive, migratory and metastatic capabilities and, secondly, in analyzing the expression of ST3Gal III and ST3Gal IV in pancreatic adenocarcinoma tissues versus control tissues. ST3Gal IV overexpressing pancreatic adenocarcinoma MDAPanc-28 cell lines were generated. They showed a heterogeneous increase in SLe(x), and enhanced E-selectin adhesion and migration. Furthermore, when injected into nude mice, increased metastasis and decreased survival were found in comparison with controls. The behaviour of MDAPanc-28 ST3Gal IV overexpressing cells in these processes was similar to the already reported MDAPanc-28 ST3Gal III overexpressing cells. Furthermore, pancreatic adenocarcinoma tissues tended to express high levels of ST3Gal III and ST3Gal IV together with other fucosyltransferase genes FUT3 and FUT6, all involved in the last steps of sialyl-Lewis(x) biosynthesis. In conclusion, both α2,3-sialyltransferases are involved in key steps of pancreatic tumour progression processes and are highly expressed in most pancreatic adenocarcinoma tissues.

A positive feedback loop between HER2 and ADAM12 in human head and neck cancer cells increases migration and invasion

Increased activation of epidermal growth factor receptor (EGFR) family members such as HER2/Erbb2 can result in more aggressive disease, resistance to chemotherapy and reduced survival of head and neck squamous cell carcinoma (HNSCC) patients. In order to identify mechanisms through which these receptor tyrosine kinases accelerate tumor progression, the regulation of metalloprotease expression by EGFR family members was investigated in 11 SCC cell lines. HER2 expression was significantly correlated with ADAM12 (A Disintegrin And Metalloprotease 12) expression in these cell lines and was co-expressed in human head and neck cancers. Inhibition of HER2 or EGFR decreased ADAM12 transcripts while HER2 transfection up-regulated ADAM12 expression. To understand the molecular mechanisms underlying HER2 regulation of ADAM12, we investigated the signaling pathways directing ADAM12 production in SCC cells. Inhibition of phosphatidyl inositol-3-kinase (PI3K) or mammalian Target of Rapamycin (mTOR) decreased ADAM12 transcripts in HER2-expressing SCC cells, while transfection with AKT increased ADAM12 mRNA. Experiments utilizing ADAM12 transfection or siRNA targeting of ADAM12 revealed that the protease increased both the migration and invasiveness of oral SCC cells. Surprisingly, ADAM12 also increased HER2 message, protein levels, and activity through an Ets1-dependent mechanism. Collectively, these results reveal a novel positive activation loop between ADAM12 and HER2 that may contribute to HNSCC progression.

alpha2,3-sialyltransferase ST3Gal III modulates pancreatic cancer cell motility and adhesion in vitro and enhances its metastatic potential in vivo

Background

Cell surface sialylation is emerging as an important feature of cancer cell metastasis. Sialyltransferase expression has been reported to be altered in tumours and may account for the formation of sialylated tumour antigens. We have focused on the influence of alpha-2,3-sialyltransferase ST3Gal III in key steps of the pancreatic tumorigenic process.

Methodology/Principal Findings

ST3Gal III overexpressing pancreatic adenocarcinoma cell lines Capan-1 and MDAPanc-28 were generated. They showed an increase of the tumour associated antigen sialyl-Lewis^x. The transfectants' E-selectin binding capacity was proportional to cell surface sialyl-Lewis^x levels. Cellular migration positively correlated with ST3Gal III and sialyl-Lewis^x levels. Moreover, intrasplenic injection of the ST3Gal III transfected cells into athymic nude mice showed a decrease in survival and higher metastasis formation when compared to the mock cells.

Conclusion

In summary, the overexpression of ST3Gal III in these pancreatic adenocarcinoma cell lines underlines the role of this enzyme and its product in key steps of tumour progression such as adhesion, migration and metastasis formation.

Increased expression of ErbB-2 in liver is associated with hepatitis B x antigen and shorter survival in patients with liver cancer

Hepatitis B x antigen, or HBxAg, contributes importantly to the pathogenesis of hepatocellular carcinoma (HCC). Given that HBxAg constitutively activates beta-catenin and that upregulated ErbB-2 promotes beta-catenin signaling in other tumor types, experiments were designed to ask whether HBxAg was associated with upregulated expression of ErbB-2. When HBxAg positive and negative HepG2 cells were subjected to proteomics analysis, ErbB-2 was shown to be upregulated in HepG2X but not control cells. ErbB-2 was also strongly upregulated in HB infected liver, and weakly in some HCC nodules, where it correlated with HBxAg expression. Among tumor bearing patients, strong ErbB-2 staining in the liver was associated with dysplasia, and a shorter survival after tumor diagnosis. This implies that elevated ErbB-2 is an early marker of HCC. Treatment of HepG2X cells with ErbB-2 specific siRNA not only reduced ErbB-2 expression, but also reduced the expression of beta-catenin, suggesting that ErbB-2 contributed to the stabilization of beta-catenin. ErbB-2 specific siRNA also partially blocked the ability of HBxAg to promote DNA synthesis and growth of HepG2 cells. These results suggest that ErbB-2/beta-catenin up-regulation contributes importantly to the mechanism of HBxAg mediated hepatocellular growth.

alpha1,3 fucosyltransferase-VII up-regulates the mRNA of alpha5 integrin and its biological function

After transfection of alpha1,3fucosyltransferase (FucT)-VII cDNA into H7721 human hepatocarcinoma cells, the expression of alpha5, but not beta1 integrin was significantly up-regulated. This was evidenced by the increase of alpha5 integrin on cell surface as well as the increase of alpha5 mRNA and protein in the cells. However, the expressions of sialyl Lewis X (SLe(x), the product of alpha1,3FucT-VII) on both alpha5 and beta1 integrin subunits were unchanged. Concomitantly, the tyrosine autophosphorylated FAK and dephosphorylated Src (FAK and Src involve in the signal transduction of integrin alpha5beta1) were up-regulated, while the Tyr-527 phosphorylated Src was down-regulated. The above-mentioned alterations were correlated to the expressions of alpha1,3FucT-VII in different alpha1,3FucT-VII transfected H7721 cell lines. In addition, after alpha1,3FucT-VII transfection, cell adhesion to fibronectin (Fn) and chemotaxic cell migration were obviously promoted. The cell adhesion could be blocked by alpha5 integrin antibody, and cell migration was obviously attenuated by the antibodies to both alpha5 integrin and SLe(x). These findings suggest that the increased surface alpha5 integrin caused by the up-regulation of alpha5 mRNA promotes the cell adhesion to Fn, cell migratiom, and Fn-induced signaling of alpha5beta1 integrin. The up-regulation of surface SLe(x) originated from the over expression of alpha1,3FucT-VII also led to the stimulation of cell migration. This is the first time to report that alpha1,3FucT-VII can regulate the mRNA expression of integrin.

FUT7 antisense sequence inhibits the expression of FUT7/sLeX and adhesion between embryonic and uterine cells

Implantation is a complex developmental event that is initiated by recognition and adhesion of the embryo to the endometrial epithelium. sLeX is an oligosaccharide antigen acting as the ligand of L-selectin, and is stage-specifically expressed in the endometrial epithelium. The adhesion system mediated by L-selectin and sLeX oligosaccharide plays an important role in this process. FUT7 is a key enzyme for sLeX synthesis, and the regulation of sLeX through FUT7 may influence maternal-fetal recognition. In this study, we observed the effect of FUT7 antisense oligodeoxynucleotide on the expression of FUT7 and sLeX, as well as adhesion in an in vitro implantation model consisting of the human uterine epithelial cell line RL95-2 and the human embryonic cell line JAR. Results showed that the expression of FUT7 was significantly decreased, compared with controls, after FUT7 antisense oligodeoxynucleotide transfection into RL95-2 cells, as determined by RT-PCR, Western blotting, and indirect immunofluorescence. Synthesis of sLeX was also decreased, consistent with the FUT7 decrease, as shown by indirect immunofluorescence. The adhesion of embryonic cells to uterine epithelial cells was significantly reduced (P < 0.01) compared with the control. These data indicate that the use of a FUT7 antisense oligodeoxynucleotide can cause a significant reduction of both FUT7 and sLeX antigen, and thereby inhibit the adhesion of embryo cells to endometrium. This approach may provide a new way to regulate reproduction.

Overexpression of fucosyltransferase VII (FUT7) promotes embryo adhesion and implantation

OBJECTIVE

To investigate the effect of increased fucosyltransferase VII (FUT7) on sialyl Lewis X (sLeX) synthesis and their impact on embryo implantation.

DESIGN

Cell and animal study.

SETTING

Liaoning Provincial Core Lab of Glycobiology and Glycoengineering, Department of Biochemistry and Molecular Biology, Dalian Medical University.

ANIMAL(S)

Adult female mice of Kunming species.

INTERVENTION(S)

A pIRES2-EGFP-FUT7 expression plasmid containing full-length human FUT7 cDNA was constructed and transiently transfected into RL95-2 or injected into the uteri of early pregnant mice. Control subjects received the mock pIRES2-EGFP or anti-sLeX antibody.

MAIN OUTCOME MEASURE(S)

The expression of FUT7 and sLeX was detected by reverse transcriptase polymerase chain reaction (RT-PCR) and indirect immunofluorescence. The embryo adhesion rate was assayed in vitro with the cocultured RL95-2 and JAR implantation model. In vivo embryo implantation was investigated using a mouse model.

RESULT(S)

Expression of FUT7 was significantly increased after transfection of pIRES2-EGFP-FUT7 into RL95-2 cells compared with the parental control and mock vector transfectants, as demonstrated by fluorescent microscopy and RT-PCR. Expression of sLeX was also increased in FUT7 overexpressers, as detected by indirect immunofluorescence. Consistent with the elevated expression of FUT7 and sLeX, embryo adhesion rate and embryo implantation competence were significantly increased (P<.01) in both in vitro and in vivo models.

CONCLUSION(S)

Overexpression of FUT7 up-regulates sLeX synthesis and enhances sLeX-mediated embryo implantation.

Introducing alpha(1,2)-linked fucose into hepatocarcinoma cells inhibits vasculogenesis and tumor growth

The glycoantigen sialyl-Lewis x (sLex) and its isomer sialy-Lewis a (sLea) are frequently associated with advanced states of cancer and metastasis. In a previous work, we have shown that hepatocarcinoma cells (HCC) HepG2 interact with the endothelial E-selectin exclusively through sLe(x) oligosaccharides, the synthesis of which could be completely prevented by the alpha(1,2)-fucosyltransferase-I (FUT1), thus resulting in a strong inhibition of adhesion and rolling on activated endothelial cells. The purpose of the present study was to evaluate the impact of inhibiting sLex synthesis and the subsequent E-selectin adhesion, on HCC tumor growth in nude mice. Four weeks after subcutaneous transplantation of cells, no FUT1-derived tumor could be detected, whereas 75% of control animals developed large size tumor nodules. Between the 4th and the 8th week postinoculation, 33% tumors arose from FUT1-transduced cells but showed a slow growth (nodule volumes less than 500 mm(3)), while more than 50% of control tumors reached volumes between 1,500 and 3,000 mm(3). Several parameters were examined, including cell division and proliferation, apoptosis, adhesion to extracellular matrix components and angiogenesis/vasculogenesis. We provide evidence that among all, vasculogenesis was the most clearly affected by FUT1 expression, suggesting that tumor angiomorphogenesis may, at least partly, depend on E-selectin-mediated interaction between HCC and endothelial cells, the inhibition of which remarkably retards tumor growth.

Alpha1,3 Fucosyltransferase-VII modifies the susceptibility of apoptosis induced by ultraviolet and retinoic acid in human hepatocarcinoma cells

The role of alpha1,3fucosyltransferase-VII (alpha1,3 FucT-VII) in cell apoptosis was studied in human hepatocellular carcinoma H7,721 cells. After the cells were transfected with alpha1,3 FucT-VII cDNA, the expression of apoptotic protease, procaspase-3, was decreased, while the anti-apoptotic proteins, phospho-PKB and phospho-Bad were increased as compared with mock (vector) transfected cells, indicating that alpha1,3FucT-VII is a potential anti-apoptotic factor in H7,721 cells. After "alpha1,3FucT-VII" cells were irradiated by UV to induce apoptosis, the anti-apoptotic potential of alpha1,3FucT-VII became more apparent, as evidenced by the less apoptotic cell % and active cleaved caspase-3, more phospho-p38 MAPK and JNK (two anti-apoptotic signaling molecules in H7,721 cells responsible to UV stress) when compared with the "Mock" cells. In contrast, "alpha1,3FucT-VII" cells facilitated the apoptosis induced by all-trans retinoic acid (ATRA), which was verified by the greater sub-G1 (apoptotic cells) peak in flow cytometry analysis, more expressions of active caspase-3 and pro-apoptotic protein Bax, as well as less expressions of anti-apoptotic proteins, Bcl-2 and Bcl-X(L). The up regulation of alpha1,3FucT-VII mRNA and cell surface SLe(x) (alpha1,3FucT-VII product) by UV and down regulation of them by ATRA was speculated to be one of the mechanisms that alpha1,3FucT-VII decreased and increased the susceptibility of apoptosis induced by UV and ATRA respectively.

Alpha 1,3-fucosyltransferase-VII regulates the signaling molecules of the insulin receptor pathway

Two H7721 human hepatocarcinoma cell lines showing moderate and high expression of alpha1,3-fucosyltransferase (FucT)-VII cDNA were established and designated FucTVII-M and FucTVII-H, respectively. In alpha1,3-FucT-VII-transfected cells, expression of insulin receptor (InR) alpha- and beta subunits and epidermal growth factor receptor (EGFR) on the cell surface and in cells, as well as the sialyl Lewis X (SLe(x), the product of alpha1,3-FucT-VII) content of the EGFR were unchanged. However the level of SLe(x) on the InR alpha subunit (InR-alpha) was increased dramatically. Tyrosine autophosphorylation of InR-beta , but not EGFR, was elevated. Concomitantly, tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), Ser/Thr phosphorylation of protein kinase B (PKB; Akt), p42/44 mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), and the protein of some other signaling molecules, such as phosphoinositide-dependent kinase-1 (PDK-1), novel protein kinase (PKN), c-Raf-1 and beta-catenin were also upregulated. The activities of PKB and transcription factor TCF were concomitantly stimulated. Upregulation of InR signaling molecules and their phosphorylation was correlated with the level of SLe(x) on InR-alpha and alpha1,3-FucT-VII expression in cells. In addition, the phosphorylation intensity and difference in phosphorylation intensity between cells with different levels of alpha1,3-FucT-VII expression were attenuated significantly by the inhibitor of InR tyrosine kinase and by the mAb to SLe(x). Furthermore, insulin-induced signaling was facilitated in alpha1,3-FucT-VII-transfected cells, particularly FucTVII-H. These findings provide strong evidence that alpha1,3-FucT-VII may affect insulin signaling by upregulating the phosphorylation and expression of some signaling molecules involved in the InR-signaling pathway. These effects are likely mediated by its product, SLe(x), on the glycans of the InR. This is the first study to report that changes in the terminal structure of glycans on a surface receptor can modify cell signaling.

Regulation of metastasis-suppressive gene Nm23-H1 on glycosyl-transferases involved in the synthesis of sialyl Lewis antigens

By using reverse transcriptase-polymerase chain reaction (RT-PCR), the mRNA expressions of three families of glycosyltransferases involved in the synthesis of sialyl Lewis antigens were determined in H7721 human hepatocarcinoma cell line before and after the transfection of metastasis-suppressive gene nm23-H1. These glycosyltransferases included alpha1,3fucosyltransferase (alpha1,3FucT)-III, -IV, -VI, -VII, and -IX, alpha2,3-sialyltransferase (ST3Gal)-I, -II, -III, and -IV as well as O-glycan core 2 beta1,6 N-acetylglucosaminyltransferase (C2GnT)-I and -II. In mock cells transfected with the vector, the expression-order of alpha1,3FucTs was IV>VI>III>VII>IX, that of ST3Gals was IV>I>II>III, and that of C2GnT was I>II. Nm23-H1 downregulated the mRNA expressions of all five subtypes of alpha1,3FucT and -I, -III, -IV subtypes of ST3Gal, but not ST3Gal-II and C2GnT-I, II. On the other hand, the expressions of cell surface sialyl Lewis X (SLe(x)) and alpha2,3 sialyl residues were decreased on nm23-H1 transfected cells as detected with monoclonal antibody of SLe(x) and enzyme-labeled lectins, respectively. Since SLe(x) was reported to be a metastasis-associated glycan structure, the reduced expressions of SLe(x) and some enzymes related to its synthesis may be one of the mechanisms to explain the metastasis-suppressive effect of nm23-H1.

Molecular mechanism for cancer-associated induction of sialyl Lewis X and sialyl Lewis A expression-The Warburg effect revisited

Cell adhesion mediated by selectins and their carbohydrate ligands, sialyl Lewis X and sialyl Lewis A, figures heavily in cancer metastasis. Expression of these carbohydrate determinants is markedly enhanced in cancer cells, but the molecular mechanism that leads to cancer-associated expression of sialyl Lewis X/A has not been well understood. Results of recent studies indicated involvement of two principal mechanisms in the accelerated expression of sialyl Lewis X/A in cancers; 'incomplete synthesis' and ' neo synthesis.' As to 'incomplete synthesis,' we have recently found further modified forms of sialyl Lewis X and sialyl Lewis A in non-malignant colonic epithelium, which have additional 6-sulfation or 2 --> 6 sialylation. The impairment of GlcNAc 6-sulfation and 2 --> 6 sialylation upon malignant transformation leads to accumulation of sialyl Lewis X/A in colon cancer cells. Epigenetic changes such as DNA methylation and/or histone deacetylation are suggested to lie behind such incomplete synthesis. As to the mechanism called ' neo synthesis,' recent studies have indicated that cancer-associated alterations in the sugar transportation and intermediate carbohydrate metabolism play important roles. Cancer cells are known to exhibit a metabolic shift from oxidative to elevated anaerobic glycolysis (Warburg effect), which is correlated with the increased gene expression of sugar transporters and glycolytic enzymes induced by common cancer-specific genetic alterations. The increased sialyl Lewis X/A expression in cancer is a link in the chains of these events because our recent results indicated that these events accompany transcriptional induction of a set of genes closely related to its expression.

Deficiency in surface expression of E-selectin ligand promotes lung colonization in a mouse model of breast cancer

Expression of sialyl Lewis(x) (sLe(x)) and sLe(a) on tumor cells is thought to facilitate metastasis by promoting cell adhesion to selectins on vascular endothelial cells. Experiments supporting this concept usually bypass the early steps of the metastatic process by employing tumor cells that are injected directly into the blood. We investigated the relative role of sLe(x) oligosaccharide in the dissemination of breast carcinoma, employing a spontaneous murine metastasis model. An sLe(x) deficient subpopulation of the 4T1 mammary carcinoma cell line was produced by negative selection using the sLe(x)-reactive KM93 MAb. This subpopulation was negative for E-selectin binding but retained P-selectin binding. Both sLe(x)-negative and -positive cells grew at the same rate; however, sLe(x)-negative cells spread more efficiently on plates and had greater motility in wound-scratch assays. Mice inoculated in the mammary fat pad with sLe(x)-negative and -positive variants produced lung metastases. However, the number of lung metastases was significantly increased in the group inoculated with the sLe(x)-negative variant (p = 0.0031), indicating that negative selection for the sLe(x) epitope resulted in enrichment for a subpopulation of cells with a high metastatic phenotype. Cell variants demonstrated significant differences in cellular morphology and pattern of tumor growth in primary and secondary tumor sites. These results strongly suggest that loss of sLe(x) may facilitate the metastatic process by contributing to escape from the primary tumor mass.

Expression of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase-12 in gastric and colonic cancer cell lines and in human colorectal cancer

OBJECTIVE

The expression of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase-12 (pp-GalNAc-T12) was studied in 3 normal human tissues (stomach, small intestine and colon), 3 stomach and 6 colon cancer cell lines, as well as in the resected cancer tissues and normal tissues (control) from 19 patients with colorectal cancer.

METHODS

Marathon Ready cDNAs were used as the templates of normal tissues. mRNA was extracted from the cell lines and resected tissues, and reverse-transcribed to cDNA. The expression of pp-GalNAc-T12 was determined with a real-time polymerase chain reaction (PCR).

RESULTS

It was found that the expression of pp-GalNAc-T12 was strong in 3 normal tissues, weak or negligible in 9 cancer cell lines, and down-regulated in all of the colorectal cancer tissues as compared with normal control samples. Moreover, the expression of pp-GalNAc-T12 tended to inversely correlate with the TNM stage, and statistically was much lower in the samples with metastasis than in those without. However, the expression in the tissues did not correlate with the concentration of serum CA 19-9 routinely applied in the diagnosis and assessment of prognosis in patients with colonic cancers.

CONCLUSION

the expression of pp-GalNAc-T12 seems to be a negative marker especially of metastatic gastric and colorectal cancer.

Forskolin up-regulates metastasis-related phenotypes and molecules via protein kinase B, but not PI-3K, in H7721 human hepato-carcinoma cell line

Forskolin (FSK) is known as an up-regulator of intracellular cAMP and inhibitor of cancer growth and metastasis. The effects of FSK on the metastasis potential and its mechanisms were studied using a human hepatocarcinoma cell line, H7721. It was found that FSK stimulated cell growth, increased cAMP in the cells, and enhanced the metastasis-related phenotypes, including adhesion to laminin (Ln) and human umbilical vein epithelial cells (HUVEC), chemotactic migration and invasion. These effects were supposed to result from the increase of the SLex expression induced by FSK, since only the monoclonal antibody of SLex showed a significant attenuation of the enhanced metastasis-associated phenotypes. Using H7721 cells transfected with the sense or antisense cDNA of protein kinase B (PKB) and some inhibitors of signal transduction, it was discovered that FSK up-regulated the expression of SLex via PKB, but it was independent of phosphotidylinositide-3-kinase (PI-3K). A subtype of atypical protein kinase C (a-PKC) might also participate in the up-regulation of SLex expression by FSK, and cAMP/PKA pathway is a negative regulator of SLex expression on H7721 cells. It can be concluded that FSK shows a metastasis-promoting effect ex vivo.

Hypoxia induces adhesion molecules on cancer cells: A missing link between Warburg effect and induction of selectin-ligand carbohydrates

Cancer cells undergo distinct metabolic changes to cope with their hypoxic environment. These changes are achieved at least partly by the action of transcriptional factors called hypoxia-inducible factors (HIFs). We investigated gene expression in cultured human colon cancer cells induced by hypoxic conditions with special reference to cell-adhesion molecules and carbohydrate determinants having cell-adhesive activity by using DNA-microarray and RT-PCR techniques. Hypoxic culture of colon cancer cells induced a marked increase in expression of selectin ligands, the sialyl Lewis x and sialyl Lewis a determinants at the cell surface, which led to a definite increase in cancer cell adhesion to endothelial E-selectin. The transcription of genes for fucosyltransferase VII (FUT7), sialyltransferase ST3Gal-I (ST3O), and UDP-galactose transporter-1 (UGT1), which are all known to be involved in the synthesis of the carbohydrate ligands for E-selectin, was significantly induced in cancer cells by hypoxic culture. In addition, a remarkable induction was detected in the genes for syndecan-4 (SDC4) and alpha5-integrin (ITGA5), the cell-adhesion molecules involved in the enhanced adhesion of cancer cells to fibronectin. The transcriptional induction by hypoxia was reproduced in the luciferase-reporter assays for these genes, which were significantly suppressed by the co-transfection of a dominant-negative form of HIF. These results indicate that the metabolic shifts of cancer cells partly mediated by HIFs significantly enhance their adhesion to vascular endothelial cells, through both selectin- and integrin-mediated pathways, and suggest that this enhancement further facilitates hematogenous metastasis of cancers and tumor angiogenesis.

Effect of N-acetylglucosaminyltransferase V on the expressions of other glycosyltransferases

Transfection of sense cDNA of N-acetylglucosaminyltransferase V (GnTV) into H7721 human hepatocellular carcinoma cells resulted in the decreased expression of surface sialyl Lewis X (SLe(x)), a sialylated fucose-containing antigen. The enzymatic mechanisms were speculated to be the concomitantly decreased expression of alpha1,3-fucosyltransferase (FucT)-III, -VI, -VII and the branching enzyme of O-glycans, core 2-beta1,6-N-acetylglucosaminyltransferase (C2GnT)-I, -II. These two glycosyltransferase families were suggested to be the key enzymes in the synthesis of SLe(x). The expression of alpha2,3-sialyltransferase (ST3)-IV, but not ST3-I, -II and -III was elevated by sense GnTV. However, it did not cause the increase of SLe(x) synthesis. Transfection of antisense GnTV into H7721 cells showed entirely opposite effects on the expression of above-mentioned SLe(x) and glycosyltransferases as the sense GnTV.

Dephosphorylation of microtubule-associated protein tau by protein phosphatase 5

Protein phosphatase 5 (PP5) is a 58-kDa novel phosphoseryl/phosphothreonyl protein phosphatase. It is ubiquitously expressed in all mammalian tissues examined, with a high level in the brain, but little is known about its physiological substrates. We found that this phosphatase dephosphorylated recombinant tau phosphorylated with cAMP-dependent protein kinase and glycogen synthase kinase-3beta, as well as abnormally hyperphosphorylated tau isolated from brains of patients with Alzheimer's disease. The specific activity of PP5 toward tau was comparable to those reported with other protein substrates examined to date. The PP5 activity toward tau was stimulated by arachidonic acid by 30- to 45-fold. Immunostaining demonstrated that PP5 was primarily cytoplasmic in PC12 cells and in neurons of postmortem human brain tissue. A small pool of PP5 associated with microtubules. Expression of active PP5 in PC12 cells resulted in reduced phosphorylation of tau, suggesting that PP5 can also dephosphorylate tau in cells. These results suggest that PP5 plays a role in the dephosphorylation of tau and might be involved in the molecular pathogenesis of Alzheimer's disease.

Insulin/protein kinase B signalling pathway upregulates metastasis-related phenotypes and molecules in H7721 human hepatocarcinoma cell line

The effect of insulin on cancer metastatic potential was studied in a human hepatocarcinoma cell line, H7721. Cell adhesion to human umbilical vein endothelial cells (HUVECs) and laminin as well as chemotactic cell migration and invasion were selected as the indices of metastasis-related phenotypes for assessment of metastatic potential ex vivo. The results indicated that insulin enhanced all of these metastasis-related phenotypes. After the cells were treated with specific inhibitor of PI3K (LY294002) or transfected with antisense cDNA of PKB (AS-PKB), all of the above phenotypes were attenuated, and they could not be significantly stimulated by insulin, indicating that the insulin effect on metastatic potential was mediated by PI3K and PKB. Only the monoclonal antibody to the sialyl Lewis X (SLe(x)), but not antibodies to other Lewis antigens, significantly blocked the cell adhesion to HUVECs, cell migration and invasion, suggesting that SLe(x) played a crucial role in the metastatic potential of H7721 cells. The upregulation of cell surface SLe(x) and alpha-1,3-fucosyltransferase-VII (alpha-1,3 Fuc T-VII, enzyme for SLe(x) synthesis) was also mediated by PI3K and PKB, since LY294002 and AS-PKB also reduced the expressions of SLe(x) and alpha-1,3 FucT-VII, and attenuated the response to insulin. Furthermore, the alterations in the expressions of PKB protein and activity were correlated to the changes of metastatic phenotypes and SLe(x) expression. Taken together, the insulin/PKB signalling pathway participated in the enhancement of metastatic potential of H7721 cells, which was mediated by the upregulation of the expression of SLe(x) and alpha-1,3 FucT-VII.

Expression levels of FUT6 gene transfected into human colon carcinoma cells switch two sialyl-Lewis X-related carbohydrate antigens with distinct properties in cell adhesion

A human colon carcinoma cell line KM12-LX, expressing low levels of monoclonal antibody (mAb) FH6 epitope, was transfected with alpha 1,3-fucosyltransferase VI cDNA. Clonal populations with high or intermediate expression levels of the mRNA, shown by RT-PCR (FT6hi and FT6in cells, respectively) were obtained. FT6hi cells were found to express both mAb FH6 and KM93 epitopes by flow-cytometric analysis, whereas FT6in cells expressed mAb FH6 epitopes but not mAb KM93 epitopes. The mAb FH6-binding was abrogated by endo-beta-galactosidase treatment of FT6in, but not FT6hi, cells. FT6hi but not FT6in cells adhered to Chinese-hamster-ovary cells expressing human E-selectin. FT6in cells adhered to sections of mouse liver and the adhesion was blocked by treatment of the cells with endo-beta-galactosidase. The results indicate that endo-beta-galactosidase-sensitive and mAb FH6-reactive carbohydrate chains are generated under the control of expression levels of FUT6 and involved in the adhesion of colon carcinoma cells to liver sections.

Diverse expression of ErbB receptor proteins during rat liver development and regeneration

BACKGROUND & AIMS

The protein expression and interactions of the ErbB receptors were examined in different liver proliferation models in vivo and in vitro, including ontogeny and regeneration following partial hepatectomy.

METHODS

Expression and tyrosine phosphorylation status of specific ErbB proteins were studied by immunologic methods.

RESULTS

The epidermal growth factor receptor, ErbB2, and ErbB3 were the only ErbB proteins detected in the liver parenchyma on embryonic day 19. ErbB2 disappeared by the third week after birth and could not be appreciably induced in the adult animal by partial hepatectomy. ErbB2 was also detected in multipotent stem (RLE) and hepatoma (H4IIe) cell lines as well as in fetal, but not adult, hepatocyte cultures. Only epidermal growth factor receptor and ErbB3 were detected in adult liver, and both showed circadian variation in protein expression. ErbB4 was not detected in any model. Patterns of ligand-induced ErbB phosphorylation differed between fetal and adult hepatocytes.

CONCLUSIONS

Complex and independent programs regulate the ErbB receptors, with implications for differential cell signaling in hepatic development and regeneration.

Expression of glycolipids bearing Lewis phenotypes in tissues and cultured cells of human gynecological cancers

Transformation-associated expression of Le(b) (Lewis antigen-b) or Le(Y) in human colorectal carcinomas has been well described. To examine the expression of glycosphingolipids (GSLs) bearing Lewis-phenotypes in human gynecological carcinoma-derived cells, we determined the concentrations of all GSLs. Although neither Le(b) nor Le(Y) was present in HEC-108 cells established from the poorly differentiated type of endometrial adenocarcinoma, other cell lines from moderately or well-differentiated types expressed either Le(b) or Le(Y), or both, at concentrations of 0.01 to 0.03 microg per mg of dry cells, which comprised 0.3 to 1.3% of the total GSLs. In the cervical and ovarian carcinoma-derived cell lines, Lewis phenotypes tended to be carried by nLc(4)Cer, which was accumulated in the cells without sialylation or fucosylation. These results indicated that expression of Le(b)- or Le(Y)-phenotypes was strongly dependent on the metabolic ability to supply the precursor GSLs. Both Le(b) and Le(Y) were successfully detected by monoclonal antibody MSN-1, which was a useful probe for the simultaneous detection of Le(b) and Le(Y). On application of MSN-1, either Le(b) or Le(Y) was detected in tissues from patients with well- and moderately differentiated types of endometrial adenocarcinoma at concentrations of 0.01 to 0.04 microg per mg of dry tissues, but not in the tissues of poorly differentiated type. Normal endometria at the follicular and luteal phases also contained the antigens, but the concentrations and the frequency of antigen expression were lower than those in the well- and moderately differentiated types of endometrial adenocarcinoma.