CD44v4 is a major E-selectin ligand that mediates breast cancer cell transendothelial migration

Characterization of CD44 variant expression in head and neck squamous cell carcinomas

CD44 is a complex family of molecules, associated with aggressive malignancies and cancer stem cells. However, the role of CD44 variants in tumor progression and treatment resistance is not clear. In this study, the expression of CD44 and its variants was assessed in head and neck squamous cell carcinomas (HNSCC). Furthermore, subpopulations of cells expressing high amounts of CD44 variants were identified and characterized, for e.g., cell cycle phase and radioresistance. Results revealed high and homogenous CD44 and CD44v7 expression in four cell lines and CD44v4 and CD44v6 in three cell lines. CD44v3 was highly expressed in two cell lines, whereas CD44v5, CD44v7/8, CD44v10, CD133, and CD24 demonstrated no or moderate expression. Moreover, a subpopulation of very high CD44v4 expression was identified, which is independent of cell phase, demonstrating increased proliferation and radioresistance. In cell starvation experiments designed to enrich for cancer stem cells, a large population with dramatically increased expression of CD44, CD44v3, CD44v6, and CD44v7 was formed. Expression was independent of cell phase, and cells demonstrated increased radioresistance and migration rate. Our results demonstrate that the heterogeneity of tumor cells has important clinical implications for the treatment of HNSCC and that some of the CD44 variants may be associated with increased radioresistance. Highly expressed CD44 variants could make interesting candidates for selective cancer targeting.

Nitric oxide inhibits hetero-adhesion of cancer cells to endothelial cells: restraining circulating tumor cells from initiating metastatic cascade

Adhesion of circulating tumor cells (CTCs) to vascular endothelial bed becomes a crucial starting point in metastatic cascade. We hypothesized that nitric oxide (NO) may prevent cancer metastasis from happening by its direct vasodilation and inhibition of cell adhesion molecules (CAMs). Here we show that S-nitrosocaptopril (CAP-NO, a typical NO donor) produced direct vasorelaxation that can be antagonized by typical NO scavenger hemoglobin and guanylate cyclase inhibitor. Cytokines significantly stimulated production of typical CAMs by the highly-purified human umbilical vein endothelial cells (HUVECs). CAP-NO inhibited expression of the stimulated CAMs (particularly VCAM-1) and the resultant hetero-adhesion of human colorectal cancer cells HT-29 to the HUVECs in a concentration-dependent manner. The same concentration of CAP-NO, however, did not significantly affect cell viability, cell cycle and mitochondrial membrane potential of HT-29, thus excluding the possibility that inhibition of the hetero-adhesion was caused by cytotoxicity by CAP-NO on HT-29. Hemoglobin reversed the inhibition of CAP-NO on both the hetero-adhesion between HT-29 and HUVECs and VCAM-1 expression. These data demonstrate that CAP-NO, by directly releasing NO, produces vasorelaxation and interferes with hetero-adhesion of cancer cells to vascular endothelium via down-regulating expression of CAMs. The study highlights the importance of NO in cancer metastatic prevention.

Curcumin-induced Aurora-A suppression not only causes mitotic defect and cell cycle arrest but also alters chemosensitivity to anticancer drugs

Overexpression of oncoprotein Aurora-A increases drug resistance and promotes lung metastasis of breast cancer cells. Curcumin is an active anticancer compound in turmeric and curry. Here we observed that Aurora-A protein and kinase activity were reduced in curcumin-treated human breast chemoresistant nonmetastatic MCF-7 and highly metastatic cancer MDA-MB-231 cells. Curcumin acts in a similar manner to Aurora-A small interfering RNA (siRNA), resulting in monopolar spindle formation, S and G2/M arrest, and cell division reduction. Ectopic Aurora-A extinguished the curcumin effects. The anticancer effects of curcumin were enhanced by Aurora-A siRNA and produced additivity and synergism effects in cell division and monopolar phenotype, respectively. Combination treatment with curcumin overrode the chemoresistance to four Food and Drug Administration (FDA)-approved anticancer drugs (ixabepilone, cisplatin, vinorelbine, or everolimus) in MDA-MB-231 cells, which was characterized by a decrease in cell viability and the occurrence of an additivity or synergy effect. Ectopic expression of Aurora-A attenuated curcumin-enhanced chemosensitivity to these four tested drugs. A similar benefit of curcumin was observed in MCF-7 cells treated with ixabepilone, the primary systemic therapy to patients with invasive breast cancer (stages IIA-IIIB) before surgery. Antagonism effect was observed when MCF-7 cells were treated with curcumin plus cisplatin, vinorelbine or everolimus. Curcumin-induced enhancement in chemosensitivity was paralleled by significant increases (additivity or synergy effect) in apoptosis and cell cycle arrest at S and G2/M phases, the consequences of Aurora-A inhibition. These results suggest that a combination of curcumin with FDA-approved anticancer drugs warrants further assessment with a view to developing a novel clinical treatment for breast cancer.

Remodeling of marrow hematopoietic stem and progenitor cells by non-self ST6Gal-1 sialyltransferase

Glycans occupy the critical cell surface interface between hematopoietic cells and their marrow niches. Typically, glycosyltransferases reside within the intracellular secretory apparatus, and each cell autonomously generates its own cell surface glycans. In this study, we report an alternate pathway to generate cell surface glycans where remotely produced glycosyltransferases remodel surfaces of target cells and for which endogenous expression of the cognate enzymes is not required. Our data show that extracellular ST6Gal-1 sialyltransferase, originating mostly from the liver and released into circulation, targets marrow hematopoietic stem and progenitor cells (HSPCs) and mediates the formation of cell surface α2,6-linked sialic acids on HSPCs as assessed by binding to the specific lectins Sambucus nigra agglutinin and Polysporus squamosus lectin and confirmed by mass spectrometry. Marrow HSPCs, operationally defined as the Lin-c-Kit+ and Lin-Sca-1+c-Kit+ populations, express negligible endogenous ST6Gal-1. Animals with reduced circulatory ST6Gal-1 have marrow Lin-Sca-1+c-Kit+ cells with reduced S. nigra agglutinin reactivity. Bone marrow chimeras demonstrated that α2,6-sialylation of HSPCs is profoundly dependent on circulatory ST6Gal-1 status of the recipients and independent of the ability of HSPCs to express endogenous ST6Gal-1. Biologically, HSPC abundance in the marrow is inversely related to circulatory ST6Gal-1 status, and this relationship is recapitulated in the bone marrow chimeras. We propose that remotely produced, rather than the endogenously expressed, ST6Gal-1 is the principal modifier of HSPC glycans for α2,6-sialic acids. In so doing, liver-produced ST6Gal-1 may be a potent systemic regulator of hematopoiesis.

Integrating physical sciences perspectives in cancer research

Cancer research integrated a physical sciences perspective through team science, which fostered communication, trust, joint publication, and open access to data.

Y-box binding protein 1--a prognostic marker and target in tumour therapy

Y-box binding protein 1 (YB-1) is a multifunctional protein involved in various cellular processes including both transcriptional and translational regulation of target gene expression. Significantly increased YB-1 levels have been reported in a number of human malignancies and shown to be associated with poor prognosis and disease recurrence. Indeed, YB-1 can act as a versatile oncoprotein playing an important role in tumour cell proliferation and progression. Consequently, YB-1 not only proves to be a good prognostic tumour marker, but also may be a promising emerging molecular target for the development of new therapeutical strategies. In this review, we discuss both the role of YB-1 in cancer and specifically in malignant melanoma as well as possible translations into the clinics derived thereof.

Crossing the endothelial barrier during metastasis

During metastasis, cancer cells disseminate to other parts of the body by entering the bloodstream in a process that is called intravasation. They then extravasate at metastatic sites by attaching to endothelial cells that line blood vessels and crossing the vessel walls of tissues or organs. This Review describes how cancer cells cross the endothelial barrier during extravasation and how different receptors, signalling pathways and circulating cells such as leukocytes and platelets contribute to this process. Identification of the mechanisms that underlie cancer cell extravasation could lead to the development of new therapies to reduce metastasis.

Human fucosyltransferase 6 enables prostate cancer metastasis to bone

Background:

The interaction between human prostate cancer (PCa) cells and bone marrow (BM) endothelium follows a rolling-and-adhesion cascade mediated by E-selectin ligand (ESL): E-selectin. This adhesion is enabled by elevated expression of α-1,3-fucosyltransferases (FTs), enzymes responsible for ESL-mediated bone metastasis in humans. In contrast, the incidence of bone metastasis in mice is rare.

Methods:

FT 3, 6 and 7 were overexpressed in mouse PCa cells. The rolling cell number, cell-rolling velocity and transendothelial migration were characterised in vitro. Fucosyltransferases-transduced mouse PCa cells expressing luciferase were inoculated into mice via left ventricle to compare the capability of bone metastasis. Mass spectrometry and immunoprecipitation were utilised for identification of ESLs.

Results:

Overexpression of FT3, FT6 or FT7 restored ESLs and enabled mouse PCa cells to roll and adhere in E-selectin-functionalised microtubes, similar to trafficking of circulating PCa cells in BM vessels. Following intracardiac inoculation, FT6-transduced cells induced robust bone metastasis in mice. Inhibition of FT6 by a fucose mimetic significantly reduced bone metastasis. Importantly, comparison of FT3, FT6 and FT7 gene expression in existing clinical samples showed significant upregulation of FT6 in PCa-distant metastases.

Conclusion:

FT6 is a key mediator of PCa cells trafficking to the BM. It may serve as a viable drug target in preclinical tests of therapeutics for reduction of PCa bone metastasis.

A physical sciences network characterization of non-tumorigenic and metastatic cells

To investigate the transition from non-cancerous to metastatic from a physical sciences perspective, the Physical Sciences–Oncology Centers (PS-OC) Network performed molecular and biophysical comparative studies of the non-tumorigenic MCF-10A and metastatic MDA-MB-231 breast epithelial cell lines, commonly used as models of cancer metastasis. Experiments were performed in 20 laboratories from 12 PS-OCs. Each laboratory was supplied with identical aliquots and common reagents and culture protocols. Analyses of these measurements revealed dramatic differences in their mechanics, migration, adhesion, oxygen response, and proteomic profiles. Model-based multi-omics approaches identified key differences between these cells' regulatory networks involved in morphology and survival. These results provide a multifaceted description of cellular parameters of two widely used cell lines and demonstrate the value of the PS-OC Network approach for integration of diverse experimental observations to elucidate the phenotypes associated with cancer metastasis.

Mechanisms of tumor cell extravasation in an in vitro microvascular network platform

A deeper understanding of the mechanisms of tumor cell extravasation is essential in creating therapies that target this crucial step in cancer metastasis. Here, we use a microfluidic platform to study tumor cell extravasation from in vitro microvascular networks formed via vasculogenesis. We demonstrate tight endothelial cell-cell junctions, basement membrane deposition and physiological values of vessel permeability. Employing our assay, we demonstrate impaired endothelial barrier function and increased extravasation efficiency with inflammatory cytokine stimulation, as well as positive correlations between the metastatic potentials of MDA-MB-231, HT-1080, MCF-10A and their extravasation capabilities. High-resolution time-lapse microscopy reveals the highly dynamic nature of extravasation events, beginning with thin tumor cell protrusions across the endothelium followed by extrusion of the remainder of the cell body through the formation of small (~1 μm) openings in the endothelial barrier which grows in size (~8 μm) to allow for nuclear transmigration. No disruption to endothelial cell-cell junctions is discernible at 60×, or by changes in local barrier function after completion of transmigration. Tumor transendothelial migration efficiency is significantly higher in trapped cells compared to non-trapped adhered cells, and in cell clusters versus single tumor cells.

Epithelial-mesenchymal transition: focus on metastatic cascade, alternative splicing, non-coding RNAs and modulating compounds

Epithelial-mesenchymal transition (EMT) is a key process in embryonic development and metastases formation during malignant progression. This review focuses on transcriptional regulation, non-coding RNAs, alternative splicing events and cell adhesion molecules regulation during EMT. Additionally, we summarize the knowledge with regard to the small potentially druggable molecules capable of modulating EMT for cancer therapy.

Lipopolysaccharide-induced toll-like receptor 4 signaling enhances the migratory ability of human esophageal cancer cells in a selectin-dependent manner

BACKGROUND

Esophageal cancer is an aggressive malignancy, and emerging data suggest that postoperative infections may promote cancer progression. Systemic exposure to lipopolysaccharide (LPS), a Gram-negative bacterial antigen involved in such infections, has been shown to increase cancer cell adhesion to the hepatic sinusoids in vivo. We investigated the direct impact of LPS on the migratory ability of esophageal cancer cells via the LPS receptor toll-like receptor 4 (TLR4).

METHODS

Human esophageal squamous carcinoma cell lines and immortalized normal esophageal mucosa cells were tested for TLR4 surface expression by reverse transcription polymerase chain reaction (RT-PCR) and flow cytometry. TLR4 signaling in response to LPS stimulation was tested in these cells by measuring p38 MAP kinase phosphorylation on Western blot. The impact of TLR4 signaling was measured by static adhesion assays in vitro and on early in vivo migration by intravital microscopy of the liver.

RESULTS

Upon LPS stimulation, phosphorylation of p38 was detected in the human esophageal cancer cells HKESC-2. Also, LPS-stimulated HKESC-2 cells showed a twofold increased adhesion to fibronectin and to hepatic sinusoidal endothelium. These effects were abolished by TLR4 inhibition using the small-molecule inhibitor eritoran. Adhesion to fibronectin and hepatic sinusoidal endothelium was also diminished by blockade of p38 phosphorylation and inhibitors of selectin-selectin ligand binding.

CONCLUSION

LPS can increase the migratory ability of human esophageal cancer cells by increasing their adhesive properties through TLR4 signaling and selectin ligands. TLR4, p38, and selectin blockade may therefore prove to be a new therapeutic strategy for this aggressive malignancy.

Anti-metastatic and anti-tumor growth effects of Origanum majorana on highly metastatic human breast cancer cells: inhibition of NFκB signaling and reduction of nitric oxide production

Background

We have recently reported that Origanummajorana exhibits anticancer activity by promoting cell cycle arrest and apoptosis of the metastatic MDA-MB-231 breast cancer cell line. Here, we extended our study by investigating the effect of O. majorana on the migration, invasion and tumor growth of these cells.

Results

We demonstrate that non-cytotoxic concentrations of O. majorana significantly inhibited the migration and invasion of the MDA-MB-231 cells as shown by wound-healing and matrigel invasion assays. We also show that O. majorana induce homotypic aggregation of MDA-MB-231 associated with an upregulation of E-cadherin protein and promoter activity. Furthermore, we show that O. majorana decrease the adhesion of MDA-MB-231 to HUVECs and inhibits transendothelial migration of MDA-MB-231 through TNF-α-activated HUVECs. Gelatin zymography assay shows that O. majorana suppresses the activities of matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9). ELISA, RT-PCR and Western blot results revealed that O. majorana decreases the expression of MMP-2, MMP-9, urokinase plasminogen activator receptor (uPAR), ICAM-1 and VEGF. Further investigation revealed that O. majorana suppresses the phosphorylation of IκB, downregulates the nuclear level of NFκB and reduces Nitric Oxide (NO) production in MDA-MB-231 cells. Most importantly, by using chick embryo tumor growth assay, we also show that O. majorana promotes inhibition of tumor growth and metastasis in vivo.

Conclusion

Our findings identify Origanummajorana as a promising chemopreventive and therapeutic candidate that modulate breast cancer growth and metastasis.

Development of quinic acid-conjugated nanoparticles as a drug carrier to solid tumors

Nanometer-sized drug carriers including polymeric nanoparticles (NPs) have been used to increase biodistribution of a drug in tumors, thereby reducing the effective dose of chemotherapy. NPs increase drug delivery to tumors to a certain extent, but the amount reaching tumors is only a small fraction of the total administered NPs because they depend on passive accumulation via the leaky vasculature surrounding tumors. In an attempt to further increase the drug delivery to tumors, we develop a polymeric NP system that interacts with an endothelial tumor marker. The NPs are decorated with quinic acid, a synthetic mimic of sialyl Lewis-x, which binds to E-selectin, overexpressed on the surface of endothelial cells surrounding solid tumors. The NPs selectively bind to endothelial cells activated with tumor necrosis factor-α, with weak affinity at a relatively high shear stress. These properties may help NPs reach tumors by increasing the encounter of NPs with the peritumoral endothelium without hindering subsequent transport of the NPs.

All-thermoplastic nanoplasmonic microfluidic device for transmission SPR biosensing

Early and accurate disease diagnosis still remains a major challenge in clinical settings. Biomarkers could potentially provide useful tools for the detection and monitoring of disease progression, treatment safety and efficacy. Recent years have witnessed prodigious advancement in biosensor development with research directed towards rapid, real-time, label-free and sensitive biomarker detection. Among emerging techniques, nanoplasmonic biosensors pose tremendous potential to accelerate clinical diagnosis with real-time multiplexed analysis, rapid and miniaturized assays, low sample consumption and high sensitivity. In order to translate these technologies from the proof-of-principle concept level to point of care clinical diagnosis, integrated, portable devices having small footprint cartridges that house low-cost disposable consumables are sought. Towards this goal, we developed an all-polymeric nanoplasmonic microfluidic (NMF) transmission surface plasmon resonance (SPR) biosensor. The device was fabricated in thermoplastics using a simple, single step and cost-effective hot embossing technique amenable to mass production. The novel 3D hierarchical mold fabrication process enabled monolithic integration of blazed nanogratings within the detection chambers of a multichannel microfluidic system. Consequently, a single hard thermoplastic bottom substrate comprising plasmonic and fluidic features allowed integration of active fluidic elements, such as pneumatic valves, in the top soft thermoplastic cover, increasing device functionality. A simple and compact transmission-based optical setup was employed with multiplexed end-point or dual-channel kinetic detection capability which did not require stringent angular accuracy. The sensitivity, specificity and reproducibility of the transmission SPR biosensor was demonstrated through label-free immunodetection of soluble cell-surface glycoprotein sCD44 at clinically relevant picomolar to nanomolar concentrations.

CD44 integrates signaling in normal stem cell, cancer stem cell and (pre)metastatic niches

The stem cell niche provides a regulatory microenvironment for cells as diverse as totipotent embryonic stem cells to cancer stem cells (CSCs) which exhibit stem cell-like characteristics and have the capability of regenerating the bulk of tumor cells while maintaining self-renewal potential. The transmembrane glycoprotein CD44 is a common component of the stem cell niche and exists as a standard isoform (CD44s) and a range of variant isoforms (CD44v) generated though alternative splicing. CD44 modulates signal transduction through post-translational modifications as well as interactions with hyaluronan, extracellular matrix molecules and growth factors and their cognate receptor tyrosine kinases. While the function of CD44 in hematopoietic stem cells has been studied in considerable detail, our knowledge of CD44 function in tissue-derived stem cell niches remains limited. Here we review CD44s and CD44v in both hematopoietic and tissue-derived stem cell niches, focusing on their roles in regulating stem cell behavior including self-renewal and differentiation in addition to cell-matrix interactions and signal transduction during cell migration and tumor progression. Determining the role of CD44 and CD44v in normal stem cell, CSC and (pre)metastatic niches and elucidating their unique functions could provide tools and therapeutic strategies for treating diseases as diverse as fibrosis during injury repair to cancer progression.

Phenotypic switch in blood: effects of pro-inflammatory cytokines on breast cancer cell aggregation and adhesion

Hematogeneous metastasis can occur via a cascade of circulating tumor cell adhesion events to the endothelial lining of the vasculature, i.e. the metastatic cascade. Interestingly, the pro-inflammatory cytokines IL-6 and TNF-α, which play an important role in potentiating the inflammatory cascade, are significantly elevated in metastatic breast cancer (BCa) patients. Despite their high metastatic potential, human breast carcinoma cells MDA-MB-231 lack interactions with E-selectin functionalized surfaces under physiological shear stresses. We hypothesized that human plasma, 3-D tumor spheroid culture, and cytokine-supplemented culture media could induce a phenotypic switch that allows BCa cells to interact with E-selectin coated surfaces under physiological flow. Flow cytometry, immunofluorescence imaging, and flow-based cell adhesion assay were utilized to investigate the phenotypic changes of MDA-MB-231 cells with various treatments. Our results indicate that plasma, IL-6, and TNF-α promote breast cancer cell growth as aggregates and induce adhesive recruitment of BCa cells on E-selectin coated surfaces under flow. 3-D tumor spheroid culture exhibits the most significant increases in the interactions between BCa and E-selectin coated surfaces by upregulating CD44V4 and sLe(x) expression. Furthermore, we show that IL-6 and TNF-α concentrations in blood may regulate the recruitment of BCa cells to the inflamed endothelium. Finally, we propose a mechanism that could explain the invasiveness of 'triple-negative' breast cancer cell line MDA-MB-231 via a positive feedback loop of IL-6 secretion and maintenance. Taken together, our results suggest that therapeutic approaches targeting cytokine receptors and adhesion molecules on cancer cells may potentially reduce metastatic load and improve current cancer treatments.

YB-1: oncoprotein, prognostic marker and therapeutic target?

Hanahan and Weinberg have proposed the ‘hallmarks of cancer’ to cover the biological changes required for the development and persistence of tumours [Hanahan and Weinberg (2011) Cell 144, 646–674]. We have noted that many of these cancer hallmarks are facilitated by the multifunctional protein YB-1 (Y-box-binding protein 1). In the present review we evaluate the literature and show how YB-1 modulates/regulates cellular signalling pathways within each of these hallmarks. For example, we describe how YB-1 regulates multiple proliferation pathways, overrides cell-cycle check points, promotes replicative immortality and genomic instability, may regulate angiogenesis, has a role in invasion and metastasis, and promotes inflammation. We also argue that there is strong and sufficient evidence to suggest that YB-1 is an excellent molecular marker of cancer progression that could be used in the clinic, and that YB-1 could be a useful target for cancer therapy.

Association of SELE genotypes/haplotypes with sE-selectin levels in Taiwanese individuals: interactive effect of MMP9 level

Background

E-selectin is implicated in various inflammatory processes and related disorders. We aimed to investigate the role of SELE-gene genotypes/haplotypes on plasma levels of MMP9 and sE-selectin in Taiwanese individuals.

Methods

Five hundred twenty individuals were enrolled. Seven tagging SELE single nucleotide polymorphisms were analyzed.

Results

SELE genotypes were found associated with MMP9 and sE-selectin levels. Multivariate analysis identified that the most significant genetic polymorphism (rs5368 genotype) was independently associated with MMP9 levels (P < 0.001). One haplotype (GGAGAGT) was marginally associated with MMP9 levels (P = 0.0490). One SELE SNP, (rs3917406, P = 0.031) was associated with sE-selectin levels after adjusting for MMP9 and sICAM1 levels. Subgroup and interaction analysis revealed association of SELE SNP rs10800469 with sE-selectin levels only in the highest quartile of MMP9 level (P = 0.002, interaction P = 0.023). Haplotype analysis showed one haplotype (AAAAAGC) borderline associated with sE-selectin level (P = 0.0511).

Conclusion

SELE genotypes/haplotypes are independently associated with MMP9 and E-selectin levels in Taiwanese individuals. The associations of SELE genotypes/haplotypes with sE-selectin levels are affected by MMP9 levels.

Effect of homotypic and heterotypic interaction in 3D on the E-selectin mediated adhesive properties of breast cancer cell lines

Hematogenous metastasis involves a glycoprotein mediated adhesion cascade of tumor cells with E-selectin on the endothelial layer of the blood vessels. Cell-cell interactions play a major role in cancer metastasis and invasiveness. Intercellular communication between two cancer cells or between a cancer cell with a stromal cell in the microenvironment such as fibroblasts or inflammatory cells play an important role in metastatic invasion. Culturing tumor cells as 3D spheroids can recapitulate these physiologically relevant cell-cell interactions. The heterogeneity in primary tumors is attributed to cell subpopulations with varying degree of invasiveness. Co-culturing cancer cells with different phenotypes as 3D spheroids can mimic this heterogeneity. Here we report the effect of homotypic and heterotypic interactions in breast cancer cells cultured as 3D spheroids on polydimethylsiloxane (PDMS) on the adhesion phenotype to E-selectin. We show that breast cancer cell lines (BT20 and MCF7) propagating as 3D spheroids on PDMS exhibit a stronger interaction with human recombinant E-selectin when compared to their respective monolayer grown counterparts on tissue culture plate (TCP). Matrigel invasion assay also indicated that BT20 and MCF7 spheroids were more invasive than BT20 and MCF7 cells grown as monolayers. To mimic tumor heterogeneity in vitro, a co-culture model included tumorigenic cell lines BT20, MCF7 and a non-tumorigenic mammary epithelial cell line MCF10A. These cell lines were cultured together in equal seeding ratio on PDMS to generate co-culture spheroids. The heterotypic interactions in the co-culture model resulted in enhancement of the adhesion of the most invasive BT20 cell line to E-selectin. BT20 cells in co-culture bound to the greatest degree to soluble E-selectin compared to MCF7 and MCF10A cells in co-culture. Co-invasion assay with co-culture spheroids indicated that BT20 cells in co-culture were more invasive than MCF7 and MCF10A cells. The results presented here indicate that homotypic and heterotypic interaction of cancer cells favor adhesion to E-selectin thus representing a complexity beyond planar cell culture. Also, when cells of different phenotypes are mixed, the heterogeneity enhances the adhesive phenotype and invasiveness of the most invasive cell population. The results challenge the classic use of planar cell culture for evaluating the adhesion of cancer cells to E-selectin and establish our co-culture technique as a model that can help investigative studies in metastasis and invasiveness of breast and other types of cancers.

Mac-2 binding protein is a novel E-selectin ligand expressed by breast cancer cells

Hematogenous metastasis involves the adhesion of circulating tumor cells to vascular endothelium of the secondary site. We hypothesized that breast cancer cell adhesion is mediated by interaction of endothelial E-selectin with its glycoprotein counter-receptor(s) expressed on breast cancer cells. At a hematogenous wall shear rate, ZR-75-1 breast cancer cells specifically adhered to E-selectin expressing human umbilical vein endothelial cells when tested in parallel plate flow chamber adhesion assays. Consistent with their E-selectin ligand activity, ZR-75-1 cells expressed flow cytometrically detectable epitopes of HECA-452 mAb, which recognizes high efficiency E-selectin ligands typified by sialofucosylated moieties. Multiple E-selectin reactive proteins expressed by ZR-75-1 cells were revealed by immunoprecipitation with E-selectin chimera (E-Ig chimera) followed by Western blotting. Mass spectrometry analysis of the 72 kDa protein, which exhibited the most prominent E-selectin ligand activity, corresponded to Mac-2 binding protein (Mac-2BP), a heretofore unidentified E-selectin ligand. Immunoprecipitated Mac-2BP expressed sialofucosylated epitopes and possessed E-selectin ligand activity when tested by Western blot analysis using HECA-452 mAb and E-Ig chimera, respectively, demonstrating that Mac-2BP is a novel high efficiency E-selectin ligand. Furthermore, silencing the expression of Mac-2BP from ZR-75-1 cells by shRNA markedly reduced their adhesion to E-selectin expressing cells under physiological flow conditions, confirming the functional E-selectin ligand activity of Mac-2BP on intact cells. In addition to ZR-75-1 cells, several other E-selectin ligand positive breast cancer cell lines expressed Mac-2BP as detected by Western blot and flow cytometry, suggesting that Mac-2BP may be an E-selectin ligand in a variety of breast cancer types. Further, invasive breast carcinoma tissue showed co-localized expression of Mac-2BP and HECA-452 antigens by fluorescence microscopy, underscoring the possible role of Mac-2BP as an E-selectin ligand. In summary, breast cancer cells express Mac-2BP as a novel E-selectin ligand, potentially revealing a new prognostic and therapeutic target for breast cancer.

Expression of E-selectin ligands on circulating tumor cells: cross-regulation with cancer stem cell regulatory pathways?

Although significant progress has been made in the fight against cancer, successful treatment strategies have yet to be developed to combat those tumors that have metastasized to distant organs. Poor characterization of the molecular mechanisms of cancer spread is a major impediment to designing predictive diagnostics and effective clinical interventions against late stage disease. In hematogenous metastasis, it is widely suspected that circulating tumor cells (CTCs) express specific adhesion molecules that actively initiate contact with the vascular endothelium lining the vessel walls of the target organ. This "tethering" is mediated by ligands expressed by CTCs that bind to E-selectin expressed by endothelial cells. However, it is currently unknown whether expression of functional E-selectin ligands on CTCs is related to cancer stem cell regulatory or maintenance pathways, particularly epithelial-to-mesenchymal transition and the reverse, mesenchymal-to-epithelial transition. In this hypothesis and theory article, we explore the potential roles of these mechanisms on the dynamic regulation of selectin ligands mediating CTC trafficking during metastasis.

Three to Tango: MUC1 as a Ligand for Both E-Selectin and ICAM-1 in the Breast Cancer Metastatic Cascade

Cancer cell tethering and rolling on the vascular wall is facilitated by various selectin: glycoprotein interactions which lead to eventual extravasation and metastases. The aberrantly underglycosylated mucin MUC1 has been shown to both abundantly express selectin binding moieties (sialyl Lewis x and a) and to consistently expose its core epitope. Flow cytometry was used to determine MUC1 expression on ZR-75-1 and MCF7 cells, while immunofluorescence microscopy was used to confirm the aberrant form of MUC1 and MUC1:ICAM-1 interactions. Each cell line was then perfused through combined E-selectin and ICAM-1 coated microtubes, as a model of the microvascular endothelium. ZR-75-1 and MCF7 were found to express abundant and low levels of underglycosylated MUC1, respectively. The rolling/adhesion profiles showed that ZR-75-1 cells, when compared to MCF7 cells, interact with E-selectin more efficiently resulting in sufficiently slow rolling velocities to form MUC1:ICAM-1 interactions thereby facilitating firm adhesion. The purpose and novelty of this work is the demonstration of the synergistic adhesion capabilities of MUC1 in the metastatic adhesion cascade, where the observed differential adhesion is consistent with the relative metastatic potential of the ZR-75-1 (highly metastatic) and MCF7 (weakly metastatic) cell lines.

Selectins and Associated Adhesion Proteins in Inflammatory disorders

Inflammation is defined as the normal response of living tissue to injury or infection. It is important to emphasize two components of this definition. First, that inflammation is a normal response and, as such, is expected to occur when tissue is damaged. Infact, if injured tissue does not exhibit signs of inflammation this would be considered abnormal and wounds and infections would never heal without inflammation. Secondly, inflammation occurs in living tissue, hence there is need for an adequate blood supply to the tissues in order to exhibit an inflammatory response. The inflammatory response may be triggered by mechanical injury, chemical toxins, and invasion by microorganisms, and hypersensitivity reactions. Three major events occur during the inflammatory response: the blood supply to the affected area is increased substantially, capillary permeability is increased, and leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury. The inflammatory response represents a complex biological and biochemical process involving cells of the immune system and a plethora of biological mediators. Cell-to-cell communication molecules such as cytokines play an extremely important role in mediating the process of inflammation. Inflammation and platelet activation are critical phenomena in the setting of acute coronary syndromes. An extensive exposition of this complex phenomenon is beyond the scope of this article (Rankin 2004).

Oxidative stress and lectin-like ox-LDL-receptor LOX-1 in atherogenesis and tumorigenesis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, monocytes, platelets, cardiomyocytes, and vascular smooth muscle cells. Its expression is minimal under physiological conditions but can be induced under pathological conditions. The upregulation of LOX-1 by ox-LDL appears to be important for physiologic processes, such as endothelial cell proliferation, apoptosis, and endothelium remodeling. Pathophysiologic effects of ox-LDL in atherogenesis have also been firmly established, including endothelial cell dysfunction, smooth muscle cell growth and migration, monocyte transformation into macrophages, and finally platelet aggregation-seen in atherogenesis. Recent studies show a positive correlation between increased serum ox-LDL levels and an increased risk of colon, breast, and ovarian cancer. As in atherosclerosis, ox-LDL and its receptor LOX-1 activate the inflammatory pathway through nuclear factor-kappa B, leading to cell transformation. LOX-1 is important for maintaining the transformed state in developmentally diverse cancer cell lines and for tumor growth, suggesting a molecular connection between atherogenesis and tumorigenesis.

The emerging importance of α-L-fucose in human breast cancer: a review

Breast cancer cells incorporate the simple sugar alpha-L-fucose (fucose) into glycoproteins and glycolipids which, in turn, are expressed as part of the malignant phenotype. We have noted that fucose is not simply a bystander molecule, but, in fact, contributes to many of the fundamental oncologic properties of breast cancer cells. Here, we summarize the evidence from us and others that fucose is necessary for key functions of neoplastic progression including hematogenous metastasis, tumor invasion through extracellular matrices including basement membranes and up-regulation of the Notch signaling system, with implications for epithelial-to-mesenchymal transition and activation of breast cancer stem cells. Additionally, certain breast cancer biomarkers are fucose-rich while a well-known marker of breast cancer progression, soluble E-selectin, is a known counter-receptor of fucosylated selectin ligands. We provide illustrative examples and supportive evidence drawn from work with human breast cancer cell lines in vitro as well as clinical studies with human pathologic material. And finally, we discuss evidence that fucose (or its absence) is central to the mechanisms of action of several experimental targeted therapies which may prove useful in breast cancer treatment. We propose that alpha-L-fucose is essential in order to construct first, the malignant and then the metastatic phenotype of many human breast cancers. This knowledge may inform the search for novel treatment approaches in breast cancer.

CD44 and HCELL: preventing hematogenous metastasis at step 1

Despite great strides in our knowledge of the genetic and epigenetic changes underlying malignancy, we have limited information on the molecular basis of metastasis. Over 90% of cancer deaths are caused by spread of tumor cells from a primary site to distant organs and tissues, highlighting the pressing need to define the molecular effectors of cancer metastasis. Mounting evidence suggests that circulating tumor cells (CTCs) home to specific tissues by hijacking the normal leukocyte trafficking mechanisms. Cancer cells characteristically express CD44, and there is increasing evidence that hematopoietic cell E-/L-selectin ligand (HCELL), a sialofucosylated glycoform of CD44, serves as the major selectin ligand on cancer cells, allowing interaction of tumor cells with endothelium, leukocytes, and platelets. Here, we review the structural biology of CD44 and of HCELL, and present current data on the function of these molecules in mediating organ-specific homing/metastasis of CTCs.

Survival advantages conferred to colon cancer cells by E-selectin-induced activation of the PI3K-NFκB survival axis downstream of Death receptor-3

Background

Extravasation of circulating cancer cells is a key event of metastatic dissemination that is initiated by the adhesion of cancer cells to endothelial cells. It requires interactions between adhesion receptors on endothelial cells and their counter-receptors on cancer cells. Notably, E-selectin, a major endothelial adhesion receptor, interacts with Death receptor-3 present on metastatic colon carcinoma cells. This interaction confers metastatic properties to colon cancer cells by promoting the adhesion of cancer cells to endothelial cells and triggering the activation of the pro-migratory p38 and pro-survival ERK pathways in the cancer cells. In the present study, we investigated further the mechanisms by which the E-selectin-activated pathways downstream of DR3 confer a survival advantage to colon cancer cells.

Methods

Cell survival has been ascertained by using the WST-1 assay and by evaluating the activation of the PI3 kinase/NFκB survival axis. Apoptosis has been assayed by determining DNA fragmentation by Hoechst staining and by measuring cleavage of caspases-8 and -3. DR3 isoforms have been identified by PCR. For more precise quantification, targeted PCR reactions were carried out, and the amplified products were analyzed by automated chip-based microcapillary electrophoresis on an Agilent 2100 Bioanalyzer instrument.

Results

Interaction between DR3-expressing HT29 colon carcinoma cells and E-selectin induces the activation of the PI3K/Akt pathway. Moreover, p65/RelA, the anti-apoptotic subunit of NFκB, is rapidly translocated to the nucleus in response to E-selectin. This translocation is impaired by the PI3K inhibitor LY294002. Furthermore, inhibition of the PI3K/Akt pathway increases the cleavage of caspase 8 in colon cancer cells treated with E-selectin and this effect is still further increased when both ERK and PI3K pathways are concomitantly inhibited. Intriguingly, metastatic colon cancer cell lines such as HT29 and SW620 express higher levels of a splice variant of DR3 that has no trans-membrane domain and no death domain.

Conclusion

Colon cancer cells acquire an increased capacity to survive via the activation of the PI3K/NFκB pathway following the stimulation of DR3 by E-selectin. Generation of a DR3 splice variant devoid of death domain can further contribute to protect against apoptosis.

Glycan changes: cancer metastasis and anti-cancer vaccines

Complex carbohydrates, which are major components of the cell membrane, perform important functions in cell-cell and cell-extracellular matrix interactions, as well as in signal transduction. They comprise three kinds of biomolecules: glycoproteins, proteoglycans and glycosphingolipids. Recent studies have also shown that glycan changes in malignant cells take a variety of forms and mediate key pathophysiological events during the various stages of tumour progression. Glycosylation changes are universal hallmarks of malignant transformation and tumour progression in human cancer, which take place on the whole cells or some specific molecules. Accordingly, those changes make them prominent candidates for cancer biomarkers in the meantime. This review mainly focuses on the correlation between glycosylation and the metastasis potential of tumour cells from comprehensive aspects to further address the vital roles of glycans in oncogenesising. Moreover, utilizing these glycosylation changes to ward off tumour metastasis by means of anti-adhesion approach or devising anti-cancer vaccine is one of promising targets of future study.

Signaling mechanism of cell adhesion molecules in breast cancer metastasis: potential therapeutic targets

Metastasis is responsible for the majority of breast cancer-related deaths. The metastatic spread of cancer cells is a complicated process that requires considerable flexibility in the adhesive properties of both tumor cells and other interacting cells. Cell adhesion molecules (CAMs) are membrane receptors that mediate cell-cell and cell-matrix interactions, and are essential for transducing intracellular signals responsible for adhesion, migration, invasion, angiogensis, and organ-specific metastasis. This review will discuss the recent advances in our understanding on the biological functions, signaling mechanisms, and therapeutic potentials of important CAMs involved in breast cancer metastasis.

Gangliosides expressed on breast cancer cells are E-selectin ligands

Cancer cell adhesion to vascular endothelium is a critical process in hematogenous metastasis. We hypothesized that breast cancer cells express ligands that bind under blood flow conditions to E-selectin expressed by endothelial cells. At a hemodynamic wall shear rate, BT-20 and MDA-MB-468 breast cancer cells adhered to cytokine-activated human umbilical cord vein endothelial cells (HUVECs) but not to anti-E-selectin monoclonal antibody treated HUVECs, demonstrating that adhesion was specifically mediated by E-selectin. Characterization of glycans expressed on breast cancer cells by a panel of antibodies revealed that BT-20 cells expressed sialyl Lewis X (sLe(x)) and sialyl Lewis A (sLe(a)) but MDA-MB-468 cells did not, suggesting that the former possess classical glycans involved in E-selectin mediated adhesion while the latter have novel binding epitopes. Protease treatment of the breast cancer cells failed to significantly alter the carbohydrate expression profiles, binding to soluble E-selectin-Ig chimera, or the ability of the cells to tether and roll on E-selectin expressed by HUVECs, indicating that glycosphingolipids are functional E-selectin ligands on these cells. Furthermore, extracted breast cancer cell gangliosides supported binding of E-selectin-Ig chimera and adhesion of E-selectin transfected cells under physiological flow conditions. In summary, our results demonstrate that breast cancer cells express sialylated glycosphingolipids (gangliosides) as E-selectin ligands that may be targeted for prevention of metastasis.

Direct measurements on CD24-mediated rolling of human breast cancer MCF-7 cells on E-selectin

Tumor cell rolling on the endothelium plays a key role in the initial steps of cancer metastasis, i.e., extravasation of circulating tumor cells (CTCs). Identification of the ligands that induce the rolling of cells is thus critical to understanding how cancers metastasize. We have previously demonstrated that MCF-7 cells, human breast cancer cells, exhibit the rolling response selectively on E-selectin-immobilized surfaces. However, the ligand that induces rolling of MCF-7 cells on E-selectin has not yet been identified, as these cells lack commonly known E-selectin ligands. Here we report, for the first time to our knowledge, a set of quantitative and direct evidence demonstrating that CD24 expressed on MCF-7 cell membranes is responsible for rolling of the cells on E-selectin. The binding kinetics between CD24 and E-selectin was directly measured using surface plasmon resonance (SPR), which revealed that CD24 has a binding affinity against E-selectin (K(D) = 3.4 ± 0.7 nM). The involvement of CD24 in MCF-7 cell rolling was confirmed by the rolling behavior that was completely blocked when cells were treated with anti-CD24. A simulated study by flowing microspheres coated with CD24 onto E-selectin-immobilized surfaces further revealed that the binding is Ca(2+)-dependent. Additionally, we have found that actin filaments are involved in the CD24-mediated cell rolling, as observed by the decreased rolling velocities of the MCF-7 cells upon treatment with cytochalasin D (an inhibitor of actin-filament dynamics) and the stationary binding of CD24-coated microspheres (the lack of actins) on the E-selectin-immobilized slides. Given that CD24 is known to be directly related to enhanced invasiveness of cancer cells, our results imply that CD24-based cell rolling on E-selectin mediates, at least partially, cancer cell extravasation, resulting in metastasis.

Migratory strategies of normal and malignant stem cells

The regulated migration of stem cells is critical for organogenesis during development and for tissue -homeostasis and repair during adulthood. Human bone marrow (BM) represents an accessible reservoir containing regenerative cell types from hematopoietic, endothelial, and mesenchymal-stromal lineages that together coordinate hematopoiesis and promote the repair of damaged vasculature and tissues throughout the body. Thus, a detailed understanding of lineage-specific stem cell mobilization, homing, and subsequent engraftment in areas of injury or disease is of critical importance to the rational development of novel cell-mediated regenerative therapies. Stem cell trafficking via the circulation from site of origin to peripheral tissues requires fundamental molecular pathways governing (1) niche-specific deadhesion of progenitor cells; (2) chemoattraction to guide progenitor cell homing; and (3) interstitial navigation and adhesion/retention of recruited progenitor cells. This overview chapter summarizes the diversity of migratory strategies employed by hematopoietic, endothelial, and mesenchymal-stromal progenitor cells during repair and regeneration after tissue damage. Further elucidation of stem cell homing and migration pathways will allow greater application of stem cells for targeted cell therapy and/or drug delivery for tissue repair. Strikingly similar migratory mechanisms appear to govern the in vivo migration of recently characterized cancer stem cells (CSC) in leukemias and solid tumors, indicating that conserved principles of stem cell migration and niche specificity will provide new information to target CSC in anticancer therapy.

Identification of thioaptamer ligand against E-selectin: potential application for inflamed vasculature targeting

Active targeting of a drug carrier to a specific target site is crucial to provide a safe and efficient delivery of therapeutics and imaging contrast agents. E-selectin expression is induced on the endothelial cell surface of vessels in response to inflammatory stimuli but is absent in the normal vessels. Thus, E-selectin is an attractive molecular target, and high affinity ligands for E-selectin could be powerful tools for the delivery of therapeutics and/or imaging agents to inflamed vessels. In this study, we identified a thiophosphate modified aptamer (thioaptamer, TA) against E-selectin (ESTA-1) by employing a two-step selection strategy: a recombinant protein-based TA binding selection from a combinatorial library followed by a cell-based TA binding selection using E-selectin expressing human microvascular endothelial cells. ESTA-1 selectively bound to E-selectin with nanomolar binding affinity (K_D = 47 nM) while exhibiting minimal cross reactivity to P- and L-selectin. Furthermore, ESTA-1 binding to E-selectin on the endothelial cells markedly antagonized the adhesion (over 75% inhibition) of sLe^x positive HL-60 cells at nanomolar concentration. ESTA-1 also bound specifically to the inflamed tumor-associated vasculature of human carcinomas derived from breast, ovarian, and skin but not to normal organs, and this binding was highly associated with the E-selectin expression level. Similarly, intravenously injected ESTA-1 demonstrated distinct binding to the tumor vasculature in a breast cancer xenograft model. Together, our data substantiates the discovery of a thioaptamer (ESTA-1) that binds to E-selectin with high affinity and specificity, thereby highlighting the potential application of ESTA-1 for E-selectin targeted delivery.

Knockdown of fucosyltransferase III disrupts the adhesion of circulating cancer cells to E-selectin without affecting hematopoietic cell adhesion

Adhesive interactions between selectins and their ligands play an essential role during cancer extravasation. Fucosylation of these proteins by fucosyltransferases, or FUTs, is critical for their functions. Using quantitative RT-PCR, we demonstrated that FUT4 and FUT7 are the predominant FUTs expressed in hematopoietic cell line, while FUT3 is heavily expressed by multiple cancer cell lines including the prostate cancer cell line MDA PCa2b. Knockdown of FUT3 expression in MDA PCa2b cells by small interference RNA (siRNA) significantly reduced FUT3 expression. Cell-surface sialyl Lewis antigens were largely abolished. Cell adhesion and cell rolling on the blood vessel wall were simulated by perfusing cancer cells through microtubes coated with recombinant human E-selectin. At physiological levels of wall shear stress, the number of flowing cancer cells recruited to the microtube surface was dramatically reduced by FUT3 knockdown. Higher rolling velocity was also observed, which is consistent with reduced E-selectin binding activity. Interestingly, FUT3 siRNA treatment also significantly reduced the cell growth rate. Combined with the novel siRNA delivery platform recently developed in our laboratory, FUT3 siRNA could be a promising conjunctive therapy aiming at reducing the metastatic virulence of circulating epithelial cancer cells.

Enhanced tumor cell isolation by a biomimetic combination of E-selectin and anti-EpCAM: implications for the effective separation of circulating tumor cells (CTCs)

The selective detection of circulating tumor cells (CTCs) is of significant clinical importance for the clinical diagnosis and prognosis of cancer metastasis. However, largely because of the extremely low number of CTCs (as low as 1 in 10(9) hematologic cells) in the blood of patients, effective detection and separation of the rare cells remain a tremendous challenge. Cell rolling is known to play a key role in physiological processes such as the recruitment of leukocytes to sites of inflammation and selectin-mediated CTC metastasis. Furthermore, because CTCs typically express the epithelial-cell adhesion molecule (EpCAM) on the surface whereas normal hematologic cells do not, substrates with immobilized antibody against EpCAM may specifically interact with CTCs. In this article, we created biomimetic surfaces functionalized with P- and E-selectin and anti-EpCAM that induce different responses in HL-60 (used as a model of leukocytes in this study) and MCF-7 (a model of CTCs) cells. HL-60 and MCF-7 cells showed different degrees of interaction with P-/E-selectin and anti-EpCAM at a shear stress of 0.32 dyn/cm(2). HL-60 cells exhibited rolling on P-selectin-immobilized substrates at a velocity of 2.26 +/- 0.28 microm/s whereas MCF-7 cells had no interaction with the surface. Both cell lines, however, had interactions with E-selectin, and the rolling velocity of MCF-7 cells (4.24 +/- 0.31 microm/s) was faster than that of HL-60 cells (2.12 +/- 0.15 microm/s). However, only MCF-7 cells interacted with anti-EpCAM-coated surfaces, forming stationary binding under flow. More importantly, the combination of the rolling (E-selectin) and stationary binding (anti-EpCAM) resulted in substantially enhanced separation capacity and capture efficiency (more than 3-fold enhancement), as compared to a surface functionalized solely with anti-EpCAM that has been commonly used for CTC capture. Our results indicate that cell-specific detection and separation may be achieved through mimicking the biological processes of combined dynamic cell rolling and stationary binding, which will likely lead to a CTC detection device with significantly enhanced specificity and sensitivity without a complex fabrication process.

PCBP-1 regulates alternative splicing of the CD44 gene and inhibits invasion in human hepatoma cell line HepG2 cells

BACKGROUND

PCBP1 (or alpha CP1 or hnRNP E1), a member of the PCBP family, is widely expressed in many human tissues and involved in regulation of transcription, transportation process, and function of RNA molecules. However, the role of PCBP1 in CD44 variants splicing still remains elusive.

RESULTS

We found that enforced PCBP1 expression inhibited CD44 variants expression including v3, v5, v6, v8, and v10 in HepG2 cells, and knockdown of endogenous PCBP1 induced these variants splicing. Invasion assay suggested that PCBP1 played a negative role in tumor invasion and re-expression of v6 partly reversed the inhibition effect by PCBP1. A correlation of PCBP1 down-regulation and v6 up-regulation was detected in primary HCC tissues.

CONCLUSIONS

We first characterized PCBP1 as a negative regulator of CD44 variants splicing in HepG2 cells, and loss of PCBP1 in human hepatic tumor contributes to the formation of a metastatic phenotype.

Consequences of the expression of sialylated antigens in breast cancer

Changes in cell surface glycosylation are common modifications that occur during oncogenesis, leading to the over-expression of tumour-associated carbohydrate antigens (TACA). Most of these antigens are sialylated and the increase of sialylation is a well-known feature of transformed cells. In breast cancer, expression of TACA such as sialyl-Lewis(x) or sialyl-Tn is usually associated with a poor prognosis and a decreased overall survival of patients. However, the specific role of these sialylated antigens in breast tumour development and aggressiveness is not clearly understood. These glycosylation changes result from the modification of the expression of genes encoding specific glycosyltransferases involved in glycan biosynthesis and the level of expression of sialyltransferase genes has been proposed to be a prognostic marker for the follow-up of breast cancer patients. Several human cellular models have been developed in order to explain the mechanisms by which carbohydrate antigens can reinforce breast cancer progression and aggressiveness. TACA expression is associated with changes in cell adhesion, migration, proliferation and tumour growth. In addition, recent data on glycolipid biosynthesis indicate an important role of G(D3) synthase expression in breast cancer progression. The aim of this review is to summarize our current knowledge of sialylation changes that occur in breast cancer and to describe the cellular models developed to analyze the consequences of these changes on disease progression and aggressiveness.

Protein modifications as potential biomarkers in breast cancer

A variety of post-translational protein modifications (PTMs) are known to be altered as a result of cancer development. Thus, these PTMs are potentially useful biomarkers for breast cancer. Mass spectrometry, antibody microarrays and immunohistochemistry techniques have shown promise for identifying changes in PTMs. In this review, we summarize the current literature on PTMs identified in the plasma and tumor tissue of breast-cancer patients or in breast cell lines. We also discuss some of the analytical techniques currently being used to evaluate PTMs.

Effects of a synonymous variant in exon 9 of the CD44 gene on pre-mRNA splicing in a family with osteoporosis

In a previous linkage study, suggestive linkage to osteoporosis was observed in marker D11S1392 on chromosome 11p12. The CD44 gene, found at this locus, was sequenced in one of the families studied. Sequencing all coding regions and promoter in affected and non-affected family members revealed a number of sequence variants, one of which was found to be linked and inherited identical by descent together with the linked STR allele. This G to A variant, which does not cause an amino acid change, was found in exon 9 of the CD44 gene, 32 base pairs upstream from the exon-intron junction. Preliminary analysis using a bioinformatics tool suggested that the presence of the A allele abolished an exon splicing enhancer (ESE) site, thus possibly affecting RNA splicing. It was observed using an exon-trapping vector, that in the presence of the A allele, only one transcript was observed in RAW264.7 cells, as opposed to two transcripts transcribed in the presence of the G allele. These observations suggest that the linked synonymous variant found in exon 9 of the CD44 gene might be increasing susceptibility to osteoporosis in this family by affecting the splicing mechanism.

Glycosylation in immune cell trafficking

Leukocyte recruitment encompasses cell adhesion and activation steps that enable circulating leukocytes to roll, arrest, and firmly adhere on the endothelial surface before they extravasate into distinct tissue locations. This complex sequence of events relies on adhesive interactions between surface structures on leukocytes and endothelial cells and also on signals generated during the cell-cell contacts. Cell surface glycans play a crucial role in leukocyte recruitment. Several glycosyltransferases such as alpha1,3 fucosyltransferases, alpha2,3 sialyltransferases, core 2 N-acetylglucosaminlytransferases, beta1,4 galactosyltransferases, and polypeptide N-acetylgalactosaminyltransferases have been implicated in the generation of functional selectin ligands that mediate leukocyte rolling via binding to selectins. Recent evidence also suggests a role of alpha2,3 sialylated carbohydrate determinants in triggering chemokine-mediated leukocyte arrest and influencing beta1 integrin function. The recent discovery of galectin- and siglec-dependent processes further emphasizes the significant role of glycans for the successful recruitment of leukocytes into tissues. Advancing the knowledge on glycan function into appropriate pathology models is likely to suggest interesting new therapeutic strategies in the treatment of immune- and inflammation-mediated diseases.

Integrins in mammary-stem-cell biology and breast-cancer progression--a role in cancer stem cells?

Cancer cells with stem cell-like properties (cancer stem cells) are believed to drive cancer and are associated with poor prognosis. Data from mouse models have demonstrated that integrins, the major cellular receptors for extracellular-matrix components, have essential roles both during cancer initiation and progression, and during cell differentiation in normal development. By presenting an overview of the role of integrins in stem-cell biology and in cancer progression, this Commentary aims to present evidence for a role of integrins in the biology of cancer stem cells. Given the recent interest in the role of integrins in breast-cancer initiation and progression, we focus on the role of the members of the integrin family and their coupled signaling pathways in mammary-gland development and tumorigenesis.