L-Selectin Facilitation of Metastasis Involves Temporal Induction of Fut7-Dependent Ligands at Sites of Tumor Cell Arrest

The role of platelet activation in tumor metastasis

Platelets are highly reactive components of the circulatory system, which exert not only haemostatic activity but also contribute to the modulation of various pathological conditions including inflammation, atherosclerosis and cancer metastasis through the release of cytokines, chemokines and the presentation of several adhesion molecules. During cancer metastasis, the formation of platelet-tumor cell aggregates in the circulation facilitates immune evasion and the microvascular arrest of tumor cells at distant sites. Several adhesion molecules, such as integrins and glycoproteins, were shown to be involved in this process. Recent findings indicate that P-selectin is another main mediator of platelet-tumor cell interactions. Other effects of activated platelets on cancer progression are associated with a release of platelet-derived factors stimulating tumor growth and angiogenesis. Any interference in platelet-tumor cell interactions resulted in attenuation of cancer metastasis. The well recognized, albeit not fully characterized function of platelets during cancer progression defines platelets as potential targets for cancer therapy. Specifically, the rapid expression of P-selectin on the cell surface of activated platelets and its strong association with metastasis provide a rationale for P-selectin inhibition as an antimetastatic treatment.

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.

Carcinoembryonic antigen and CD44 variant isoforms cooperate to mediate colon carcinoma cell adhesion to E- and L-selectin in shear flow

Selectin-mediated adhesion of tumor cells to platelets, leukocytes, and endothelial cells may regulate their hematogenous dissemination in the microvasculature. We recently identified CD44 variant isoforms (CD44v) as functional P-, but not E- or L-, selectin ligands on colon carcinoma cells. Moreover, an approximately 180-kDa sialofucosylated glycoprotein(s) mediated selectin binding in CD44-knockdown cells. Using immunoaffinity chromatography and tandem mass spectrometry, we identify this glycoprotein as the carcinoembryonic antigen (CEA). Blot rolling assays and flow-based adhesion assays using microbeads coated with CEA immunopurified from LS174T colon carcinoma cells and selectins as substrate reveal that CEA possesses E- and L-, but not P-, selectin ligand activity. CEA on CD44-knockdown LS174T cells exhibits higher HECA-452 immunoreactivity than CEA on wild-type cells, suggesting that CEA functions as an alternative acceptor for selectin-binding glycans. The enhanced expression of HECA-452 reactive epitopes on CEA from CD44-knockdown cells correlates with the increased CEA avidity for E- but not L-selectin. Through the generation of stable knockdown cell lines, we demonstrate that CEA serves as an auxiliary L-selectin ligand, which stabilizes L-selectin-dependent cell rolling against fluid shear. Moreover, CEA and CD44v cooperate to mediate colon carcinoma cell adhesion to E- and L-selectin at elevated shear stresses. The novel finding that CEA is an E- and L-selectin ligand may explain the enhanced metastatic potential associated with tumor cell CEA overexpression and the supportive role of selectins in metastasis.

Metastatic cancer cell

Metastasis is the result of cancer cell adaptation to a tissue microenvironment at a distance from the primary tumor. Metastatic cancer cells require properties that allow them not only to adapt to a foreign microenvironment but to subvert it in a way that is conducive to their continued proliferation and survival. Recent conceptual and technological advances have contributed to our understanding of the role of the host tissue stroma in promoting tumor cell growth and dissemination and have provided new insight into the genetic makeup of cancers with high metastatic proclivity.

Differential gene expression signature between primary and metastatic head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a world-wide malignancy. This study aimed to identify differential gene expression associated with the progression of disease from primary to metastatic HNSCC. Microdissection retrieved pure epithelial cells from paired primary tumours and cervical lymph node metastasis. cDNA microarray analysis and algorithm grouping identified differential mRNA expression of 301 genes. Quantitative reverse transcription-polymerase chain reaction analysis clarified the up-regulation of CCL19, CR2, EGR2, FUCA1, RGS1, and SELL, as well as the down-regulation of IGFBP6 and KLK8 in nodal metastasis compared to primary tumours. Immunohistochemistry confirmed the up-regulation of SELL and down-regulation of IGFBP6 in nodal metastasis relative to primary tumours. Interestingly, primary tumours exhibiting higher FUCA1 and SELL expression were associated with significantly worse patient survival. In OECM-1 HNSCC cells, inhibition of proliferation, migration, and anchorage-independent growth was noted following knockdown of SELL expression. In SAS HNSCC cells, expression of exogenous SELL resulted in increased invasion, anchorage-independent growth, and xenographic tumourigenesis in nude mice. Knockdown of FUCA1 and treatment with IGFBP6 inhibited the migration of OECM-1 cells. Knockdown of RGS1 inhibited the anchorage-independent growth of SAS cells. Our results provide a useful gene signature profile describing the factors underlying the metastasis of HNSCC to cervical lymph nodes, which may be beneficial for the treatment of HNSCC metastasis.

The dual role of CD44 as a functional P-selectin ligand and fibrin receptor in colon carcinoma cell adhesion

Selectins and fibrin(ogen) play key roles in the hematogenous dissemination of tumor cells, and especially of colon carcinomas. However, the fibrin(ogen) receptor(s) on colon carcinoma cells has yet to be defined along with its relative capacity to bind fibrinogen versus fibrin under flow. Moreover, the functional P-selectin ligand has yet to be validated using intact platelets rather than purified selectin substrates. Using human CD44-knockdown and control LS174T cells, we demonstrate the pivotal involvement of CD44 in the P-selectin-mediated binding to platelets in shear flow. Quantitative comparisons of the binding kinetics of LS174T versus P-selectin glycoprotein ligand-1 (PSGL-1)-expressing THP-1 cells to activated platelets reveal that the relative avidity of P-selectin-CD44 binding is more than sevenfold lower than that of P-selectin-PSGL-1 interaction. Using CD44-knockdown LS174T cells and microspheres coated with CD44 immunoprecipitated from control LS174T cells, and purified fibrin(ogen) as substrate, we provide the first direct evidence that CD44 also acts as the major fibrin, but not fibrinogen, receptor on LS174T colon carcinoma cells. Interestingly, binding of plasma fibrin to CD44 on the colon carcinoma cell surface interferes with the P-selectin-CD44 molecular interaction and diminishes platelet-LS174T heteroaggregation in the high shear regime. Cumulatively, our data offer a novel perspective on the apparent metastatic potential associated with CD44 overexpression on colon carcinoma cells and the critical roles of P-selectin and fibrin(ogen) in metastatic spread and provide a rational basis for the design of new therapeutic strategies to impede metastasis.

P-selectin: a common therapeutic target for cardiovascular disorders, inflammation and tumour metastasis

P-selectin belongs to the family of selectin adhesion molecules, and is expressed by platelets and endothelial cells on stimulation. This pattern of expression may indicate an involvement of this molecule in inflammation and coagulation. Data from mice lacking P-selectin expression confirmed this assumption. In addition, a key role of P-selectin in the formation of tumour metastases has been established. Apparently unrelated, clinical experience has pointed towards a detrimental interaction of inflammation and cancer with thromboembolic diseases and vice versa. Therefore, targeting molecules such as P-selectin contributing to coagulation, inflammation and metastasis may offer novel therapeutic strategies to treat chronic inflammatory diseases and metastatic cancer. The authors aim to critically evaluate the contribution of P-selectin in these diseases, and discuss the value of therapeutic inhibition of P-selectin functions in coagulation, inflammation and metastasis.

P-selectin- and heparanase-dependent antimetastatic activity of non-anticoagulant heparins

Vascular cell adhesion molecules, P- and L-selectins, facilitate metastasis of cancer cells in mice by mediating interactions with platelets, endothelium, and leukocytes. Heparanase is an endoglycosidase that degrades heparan sulfate of extracellular matrix, thereby promoting tumor invasion and metastasis. Heparin is known to efficiently attenuate metastasis in different tumor models. Here we identified modified, nonanticoagulant species of heparin that specifically inhibit selectin-mediated cell-cell interactions, heparanase enzymatic activity, or both. We show that selective inhibition of selectin interactions or heparanase with specific heparin derivatives in mouse models of MC-38 colon carcinoma and B16-BL6 melanoma attenuates metastasis. Selectin-specific heparin derivatives attenuated metastasis of MC-38 carcinoma, but heparanase-specific derivatives had no effect, in accordance with the virtual absence of heparanase activity in these cells. Heparin derivatives had no further effect on metastasis in mice deficient in P- and L-selectin, indicating that selectins are the primary targets of heparin antimetastatic activity. Selectin-specific and heparanase-specific derivatives attenuated metastasis of B16-BL6 melanomas to a similar extent. When mice were injected with a derivative containing both heparanase and selectin inhibitory activity, no additional attenuation of metastasis could be observed. Thus, selectin-specific heparin derivatives efficiently attenuated metastasis of both tumor cell types whereas inhibition of heparanase led to reduction of metastasis only in tumor cells producing heparanase.

Glycan-based interactions involving vertebrate sialic-acid-recognizing proteins

All cells in nature are covered by a dense and complex array of carbohydrates. Given their prominence on cell surfaces, it is not surprising that these glycans mediate and/or modulate many cellular interactions. Proteins that bind sialic acid, a sugar that is found on the surface of the cell and on secreted proteins in vertebrates, are involved in a broad range of biological processes, including intercellular adhesion, signalling and microbial attachment. Studying the roles of such proteins in vertebrates has improved our understanding of normal physiology, disease and human evolution.

The attenuation of experimental lung metastasis by a bile acid acylated-heparin derivative

The inhibitory efficacies of new bile acid acylated-heparin derivative (heparin-DOCA) were evaluated on experimental lung metastasis. We evaluated the effect of heparin-DOCA on intercellular interactions including those between B16F10 and thrombin-activated platelets and TNF-alpha-activated HUVECs, and between B16F10 and immobilized mouse P-selectin. In addition, the inhibitory effects of heparin-DOCA on adhesion and invasion of B16F10 to Matrigel were studied. In an animal mouse study, the blood clot formation and the retention of red fluorescence protein (RFP)-B16F10 in lungs were assessed after heparin-DOCA and RFP-B16F10 intravenous administration. Furthermore, we investigated the anti-metastatic effect of heparin-DOCA against lung metastasis induced by B16F10 and SCC7. Heparin-DOCA inhibited intercellular interactions between B16F10 and activated platelets or activated HUVECs by blocking P- and E-selectin-mediated interactions. Moreover, it reduced adhesion and invasion of B16F10 to ECM, thereby affecting the reduction of early retention of B16F10 in the lung. Heparin-DOCA attenuated lung colony formation on the surfaces and in interior of the lung, and attenuated metastasis by B16F10 and SCC7. These results suggest that heparin-DOCA may have potentials as therapeutic agent that prevents tumor metastasis and progression.

Eukaryotic expression of the broad-spectrum chemokine receptor antagonist vMIP-II and its effects on T-cell function in vitro and in vivo

Pro-inflammatory chemokines and their receptors exhibit elementary functions in cell migration and in Th1-driven inflammatory conditions. One therapeutic strategy to prevent accumulation of pro-inflammatory immune cells is the use of specific chemokine receptor antagonists. An interesting and promising candidate in this context is the viral antagonist MIP-II (vMIP-II) that acts on a broad spectrum of chemokine receptors. To study the in vitro and in vivo effects of vMIP-II on pro-inflammatory chemokine receptor function, we further characterized an ovalbumin-specific murine central memory Th1IF12 clone by using RT-PCR, cDNA array and cytometry. Using in vitro chemotaxis assays we show that eukaryotically generated vMIP-II strongly inhibited migration of CCL2- or CCL5-stimulated Th1 IF12 cells. Using intravital microscopy, we observed that CCL5 induced rolling of Th1 cells in the ear vasculature of C57Bl/6 mice. Pre-treatment with vMIP-II significantly reduced CCL5-induced rolling of Th1 cells to basal levels, indicating, that vMIP-II is also active in vivo (proportion of rolling cells: 19.4 +/- 3.8%, 39.8 +/- 2.9% and 26.1 +/- 3.2%). In addition, investigating the anti-inflammatory action of vMIP-II in adoptive transfer of immunity and dinitrofluorobenzene-induced cutaneous hypersensitivity reaction using C57Bl/6 mice, we show a direct inhibitory effect of vMIP-II on the sensitization phase [Delta ear swelling 62 and 37 cm x 10(-3) for controls and vMIP-II treated mice (2.5 mg/kg), respectively] and effector phase (Delta ear swelling 14.8 and 3.6 cm x 10(-3) for controls and vMIP-II treated mice (2.5 mg/kg), respectively) of cutaneous hypersensitivity. These data indicate that vMIP-II is a promising agent to interfere with chronic inflammatory (skin) diseases.

Diversity in cell surface sialic acid presentations: implications for biology and disease

Sialic acids (Sias) are typically found as terminal monosaccharides attached to cell surface glycoconjugates. They play many important roles in many physiological and pathological processes, including microbe binding that leads to infections, regulation of the immune response, the progression and spread of human malignancies and in certain aspects of human evolution. This review will provide some examples of these diverse roles of Sias and briefly address immunohistochemical approaches to their detection.