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

Enhanced expression of hydroxylated ceramide in well-differentiated endometrial adenocarcinoma

Based on our previous analysis of neutral glycolipids in the human endometrium, the present authors already reported that the concentrations of glucosylceramide, lactosylceramide and globotriaosylceramide (Gb₃Cer), in which both fatty acids and sphingosines in the ceramides are hydroxylated, exhibit a marked increase during the luteal phase of the menstrual cycle. It is also well known that poorly differentiated endometrial adenocarcinoma exhibits a more rapid progression and a worse response to therapy than well-differentiated endometrial adenocarcinoma. To examine the molecular background of well-differentiated and poorly differentiated cancers, the levels of neutral glycolipids in tumor tissues from endometrial carcinoma displaying different degrees of differentiation were measured. The composition of neutral glycolipids in tumor tissues was determined, and ceramide structures that were specifically expressed in well-differentiated endometrial carcinomas were investigated using biochemical analytical methods, including lipid extraction, enzyme digestion, thin-layer chromatography (TLC), gas-liquid chromatography and mass spectrometry. Well-differentiated adenocarcinoma contained numerous structurally unknown glycolipids that exhibited slower migration than globotetraosylceramide (Gb₄Cer). In the case of Gb₃Cer, three bands appeared on TLC in well-differentiated cancer, but only two bands appeared in the poorly-differentiated cancer. This difference was associated with the fatty acid composition of ceramide, since non-hydroxy fatty acids with ≥20 carbon atoms were increased in well-differentiated cancer, while α-hydroxy fatty acids were increased in poorly differentiated cancer. Similarly, there were two bands on TLC of Gb₄Cer from well-differentiated cancer, but only one band in poorly differentiated cancer, and the long-chain base of ceramide was observed to contain phytosphingosine in well-differentiated cancer. It was demonstrated in endometrial cancer that the structure of ceramide molecules changes with the extent of tumor differentiation. These findings suggest that hydroxylated ceramides contribute to the well-differentiated phenotype of endometrial adenocarcinoma.

HSF1 and Sp1 regulate FUT4 gene expression and cell proliferation in breast cancer cells

Lewis Y (LeY) is a carbohydrate tumor-associated antigen. The majority of cancer cells derived from epithelial tissues express LeY type difucosylated oligosaccharides. Fucosyltransferase IV (FUT4) is an essential enzyme that catalyzes the synthesis of LeY oligosaccharides. In a previous study we reported that FUT4 is associated with cell proliferation; however, despite the important role of FUT4 in cancer proliferation and apoptosis, little is known about the mechanisms underlying the regulation of FUT4 transcription. In the current study we investigated the regulation of FUT4 transcription in human breast cancer. We compared the regulation of human FUT4 gene transcription in human breast cancer cells (MCF-7 and MDA-MB-231) using promoter/luciferase analyses. Using a series of promoter deletion constructs, we identified a potential regulatory site located between 0.8 and 1.6 kb of the FUT4 promoter. As shown by EMSA and ChIP analyses, heat-shock factor 1 (HSF1) and Sp1are required for FUT4 promoter activity. In addition, we explored the role of HSF1 and Sp1 on cell proliferation, and found that the ERK1/2 MAPK and PI3K/Akt signaling pathways regulate the expression of FUT4, which play a role in cell proliferation via HSF1 and Sp1. These results suggest that FUT4 is a target gene for HSF1 and Sp1 that is required for cell cycle progression in breast cancer epithelial cells.

Enhanced expression of sulfatide, a sulfated glycolipid, in well-differentiated endometrial adenocarcinoma

OBJECTIVES

It is well known that a poorly differentiated endometrial adenocarcinoma shows more rapid progression and a worse response to therapy than a well-differentiated endometrial adenocarcinoma. Qualitative and quantitative changes of cell surface glycolipids occur during neoplastic transformation. Sulfatide is one of the sulfated glycolipids in the cell membrane that may have an important role in various functions such as cell adhesion. To examine the molecular background of the morphological and biological features of well-differentiated and poorly differentiated cancer, we measured the levels of lipids, especially glycolipids, in tumor tissues from patients with endometrial carcinoma.

MATERIALS AND METHODS

We determined the composition of lipids and glycolipids in tumor tissues, investigated glycosyltransferase messenger RNA expression by the reverse transcription-polymerase chain reaction, and assessed the localization of galactosylceramide sulfotransferase (an enzyme involved in sulfatide biosynthesis) by immunohistochemical staining.

RESULTS

No significant differences were observed between well-differentiated and poorly differentiated cancer with respect to the levels of cholesterol ester, cholesterol, phospholipids, cholesterol sulfate, ceramides, neutral glycolipids of the globo series, and GM3 ganglioside. However, the amount of sulfatides in well-differentiated tumors was significantly greater than that in poorly differentiated tumors, which was confirmed by thin-layer chromatography and immunostaining with a monoclonal antisulfatide antibody. Altered expression of sulfatide was found to be secondary to a change of galactosylceramide sulfotransferase messenger RNA expression. Immunohistochemical staining revealed that galactosylceramide sulfotransferase expression was characteristically observed in glandular areas but not in solid areas.

CONCLUSION

These findings suggest that sulfatide contributes to the well-differentiated phenotype of endometrial adenocarcinoma and that it is being expressed in normal uterine endometrium at sites of gland formation during the luteal phase, as we have previously reported.

Tumor-associated glycans and their role in gynecological cancers: accelerating translational research by novel high-throughput approaches

Glycans are important partners in many biological processes, including carcinogenesis. The rapidly developing field of functional glycomics becomes one of the frontiers of biology and biomedicine. Aberrant glycosylation of proteins and lipids occurs commonly during malignant transformation and leads to the expression of specific tumor-associated glycans. The appearance of aberrant glycans on carcinoma cells is typically associated with grade, invasion, metastasis and overall poor prognosis. Cancer-associated carbohydrates are mostly located on the surface of cancer cells and are therefore potential diagnostic biomarkers. Currently, there is increasing interest in cancer-associated aberrant glycosylation, with growing numbers of characteristic cancer targets being detected every day. Breast and ovarian cancer are the most common and lethal malignancies in women, respectively, and potential glycan biomarkers hold promise for early detection and targeted therapies. However, the acceleration of research and comprehensive multi-target investigation of cancer-specific glycans could only be successfully achieved with the help of a combination of novel high-throughput glycomic approaches.

Construction and identification of human fucosyltransferase 4 eukaryotic fluorenscent expression vector

AIM: To construct and identify the eukaryotic expression vector pEGFP-N1-FUT4 with en-hanced green fluorescent protein (EGFP) gene.

METHODS: The full-length fucosyltransferase 4 (FUT4) cDNA was acquired by reverse transcription-polymerase chain reaction (RT-PCR) and cloned into pEGFP-N1vector. The obtained pEGFP-N1-FUT4 was transiently transfected into cell line A431. Then the expression of FUT4 was observed under fluorescence microscope and examined by semi-quantitative RT-PCR and Western blotting.

RESULTS: The full-length human FUT4 cDNA was obtained and identified correct through sequencing and enzyme digestion. The recombinant plasmid pEGFP-N1-FUT4 was successfully constructed and FUT4 cDNA was correctly inserted into pEGFP-N1-FUT4. The expression of EGFP in A431 cells transfected with pEGFP-N1-FUT4 was observed by fluorescence microscopy. Semi-quantitative RT-PCR and Western blotting showed that FUT4 expression significantly increased after pEGFP-N1-FUT4 transfection in A431 cells in comparison with that in the controls.

CONCLUSION: The prokaryotic expression plasmid pEGFP-N1-FUT4 vector is successfully constructed, which could express FUT4 in A431 cells.

Overexpression of fucosyltransferase IV in A431 cell line increases cell proliferation

Fucosyltransferase IV is an essential enzyme that catalyzes the synthesis of fucosylated oligosaccharides by transferring GDP-fucose to the terminal N-acetylglucosamine with the alpha1,3-linkage. Lewis Y oligosaccharide has a terminal alpha1,3-linked fucose residue and elevation of Lewis Y level is seen in many epithelial cancers. The mechanism of Lewis Y elevation in neoplastic cells is still largely unknown. To study the impact of fucosyltransferase IV on Lewis Y expression and its role on neoplastic cell proliferation, a pEGFP-N1-FUT4 recombinant plasmid was developed and stably transfected into A431 cells. We found that fucosyltransferase IV overexpression promoted cell proliferation and increased the expression of proliferating cell nuclear antigen that correlated with Lewis Y augmentation. Cell cycle analysis demonstrated that fucosyltransferase IV overexpression facilitated cell cycle progression. In conclusion, fucosyltransferase IV overexpression augments Lewis Y expression to trigger neoplastic cell proliferation. These studies suggest that fucosyltransferase IV may serve as a potential therapeutic target for the treatment of Lewis Y-positive epithelial cancers.

Alterations in the glycolipid composition and cellular properties of ovarian carcinoma-derived RMG-1 cells on transfection of the alpha1,2-fucosyltransferase gene

Transfection of the mouse Fut1 and Fut2, and human FUT1 genes into human ovarian carcinoma-derived RMG-1 cells resulted in 20-30-fold increases in cellular alpha1,2-fucosyltransferase activity, and in alteration of the glycolipid composition, including not only fucosylated products, but also precursor glycolipids. Although globo-series glycolipids were not significantly affected by the transfection, the major glycolipids belonging to the lacto-series type 1 chain family in RMG-1 cells and the transfectants were the Lc4Cer, Lewis a (Le)a and Leb, and H-1 glycolipids, respectively, suggesting that fucosylation of Lc4Cer to the H-1 glycolipid prevents the further modification of Lc4Cer to Lea and Leb in the transfectants. Also, the lacto-series type 2 chains in RMG-1 cells were LeX, NeuAc-nLc4Cer and NeuAc-LeX, and those in the transfectants were LeX and LeY, indicating that the sialylation of nLc4Cer and LeX is restricted by increased fucosylation of LeX. As a result, the amount of sialic acid released by sialidase from the transfectants decreased to 70% of that from RMG-1 cells, and several membrane-mediated phenomena, such as the cell-to-cell interaction between cancer cells and mesothelial cells, and the cell viability in the presence of an anticancer drug, 5-fluorouracil, for the transfectants was found to be increased in comparison to that for RMG-1 cells. These findings indicate that cell surface carbohydrates are involved in the biological properties, including cell-to-cell adhesion and drug resistance, of cancer cells.