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The metastatic breast cancer cell line, 4T1, abundantly expresses the oligosaccharide sialylated Lewis x (sLe x ). SLe x oligosaccharide on tumor cells can be recognized by E-and P-selectin, contributing to tumor metastatic process. We observed that both selectins reacted with this cell line. However, contrary to the E-selectin reactivity, which was sLe x dependent, P-selectin reactivity with this cell line was sLe x -independent. The sLe x -Neg variant of the 4T1 cell line with markedly diminished expression of sLe x and lack of sLe a , provided a unique opportunity to characterize Pselectin ligands and their contribution to metastasis in the absence of overlapping selectin ligands and E-selectin binding. We observed that P-selectin binding was Ca 21-independent and sulfation-dependent. We found that P-selectin reacted primarily with cell surface chondroitin sulfate (CS) proteoglycans, which were abundantly and stably expressed on the surface of the 4T1 cell line. P-selectin binding to the 4T1 cells was inhibited by heparin and CS glycosaminoglycans (GAGs). Moreover, Heparin administration significantly inhibited experimental lung metastasis. In addition, the data suggest that surface CS GAG chains were involved in P-selectin mediated adhesion of the 4T1 cells to murine platelets and human umbilical vein endothelial cells. The data suggest that CS GAGs are also the major P-selectin-reactive ligands on the surface of human MDA-MET cells. The results warrant conducting clinical studies on the involvement of cell surface CS chains in breast cancer metastasis and evaluation of various CS types and their biosynthetic pathways as target for development of treatment strategies for antimetastatic therapy of this disease. ' 2006 Wiley-Liss, Inc.Key words: P-selectin; chondroitin sulfate; breast cancer; cell-cell adhesion Breast cancer metastasis represents a terrible milestone associated with a poor prognosis. The multistep process of metastasis includes release of malignant cells from the primary neoplasm, migration of cancer cells into the blood circulation, interaction with platelets and leukocytes in circulation, adhesion to the vascular endothelium in distant organs and growth of the disseminated cancer cells within the vessels or within the tissue following extravasation.1-3 Each step in this process requires different types of interactions between cancer cells and the host microenvironment.A widely accepted hypothesis is that cancer cells exploit the adhesion molecules used by hematopoietic cells to migrate into distant organs. 4 In particular, the selectin family of adhesion molecules whose ligands, sialyl Lewis x (sLe x ) and sialyl Lewis a (sLe a ), are expressed at elevated levels on various cancer cells of human and murine origin 5-9 and play a significant role in cancer metastasis. The oligosaccharides sLe x and sLe a are the prime ligands for P-and E-selectin and many published works underscore the relative importance of interactions between sLe x/a and these vascular receptors in the hematogenous spread ...

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The selective targeting of tumor-associated carbohydrate Ags by the induction of serum Abs that trigger apoptosis of tumor cells as a means to reduce circulating tumor cells and micrometastases would be an advantage in cancer vaccine development. Some plant lectins like Griffonia simplicifolia lectin I and wheat germ agglutinin mediate the apoptosis of tumor cells. We investigated the possibility of using these lectins as templates to select peptide mimotopes of tumor-associated carbohydrate Ags as immunogens to generate cross-reactive Abs capable of mediating apoptosis of tumor cells. In this study, we show that immunization with a mimotope selected based on its reactivity with Griffonia simplicifolia lectin I and wheat germ agglutinin induced serum IgM Abs in mice that mediated the apoptosis of murine 4T1 and human MCF7 cell lines in vitro, paralleling the apoptotic activity of the lectins. Vaccine-induced anti-carbohydrate Abs reduced the outgrowth of micrometastases in the 4T1 spontaneous tumor model, significantly increasing survival time of tumor-bearing animals. This finding parallels suggestions that carbohydrate-reactive IgM with apoptotic activity may have merit in the adjuvant setting if the right carbohydrate-associated targets are identified.

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 5 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. ' 2005 Wiley-Liss, Inc.Key words: sialyl Lewis x antigen; metastasis; 4T1 cells; breast cancer Tumor metastasis is a multistep process requiring detachment of malignant cells from the primary tumor, penetration of blood or lymph vessels, attachment to endothelium of distant organs and formation of new tumor foci. 1,2 Tissue invasion and metastasis of tumor cells are highly dependent on cell-cell interactions, many of which involve alterations in cell surface glycosylation patterns. 3,4 Although adhesion pathways utilized by tumor cells show considerable diversity, members of the selectin family of molecules and numerous neolactoseries antigens highly expressed on the tumor cell surface are involved in tumor metastasis by mediating binding of blood-borne tumor cells via E-and/or P-selectin to vascular endothelium. [5][6][7][8][9][10] Much of what we know about selectin interactions comes from studies of leukocytes. 11,12 Functionally, the binding of selectins to leukocytes requires sialylated and fucosylated carbohydrate structures; their prototypes are SAa2-3Galb1-4(Fuca1-3)GlcNAc and SAa2-3Galb1-3(Fuca1-4)GlcNAc, referred to as sLe x and sLe a , respectively. [13][14][15] Both sLe x and sLe a are involved in selectin-mediated adhesion of cancer cells to vascular endothelium, and these determinants are thought to be closely associated with hematogenous metastasis of cancers. [16][17][18][19] These determinants not only are markers for cancer but also are functionally implicated ...

Aberrant glycosylation is a universal feature of cancer cells, and certain glycan structures are well-known markers for tumor progression. Availability and composition of sugars in the microenvironment may affect cell glycosylation. Recent studies of human breast tumor cell lines indicate their ability to take up and utilize fructose. Here we tested the hypothesis that adding fructose to culture as a carbon source induces phenotypic changes in cultured human breast tumor cells that are associated with metastatic disease. MDA-MB-468 cells were adapted to culture media in which fructose was substituted for glucose. Changes in cell surface glycan structures, expression of genes related to glycan assembly, cytoskeleton F-actin, migration, adhesion and invasion were determined. Cells cultured in fructose expressed distinct cell-surface glycans. The addition of fructose affected sialylation and fucosylation patterns. Fructose feeding also increased binding of leukoagglutinating Phaseolus vulgaris isolectin, suggesting a possible rise in expression of branching β-1, 6 GlcNAc structures. Rhodamine-phalloidin staining revealed an altered F-actin cytoskeletal system. Fructose accelerated cellular migration and increased invasion. These data suggest that changing the carbon source of the less aggressive MDA-MB-468 cell line induced characteristics associated with more aggressive phenotypes. These data could be of fundamental importance due to the markedly increased consumption of sweeteners containing free fructose in recent years, as they suggest that the presence of fructose in nutritional micro-environment of tumor cells may negatively affect the outcome for some breast cancer patients.