Neu5Ac:GalNAc␣2,6-sialyltransferase: CMP-Neu5Ac: R-GalNAc␣1-O-Ser/Thr ␣2,6-sialyltransferase (EC ... more Neu5Ac:GalNAc␣2,6-sialyltransferase: CMP-Neu5Ac: R-GalNAc␣1-O-Ser/Thr ␣2,6-sialyltransferase (EC 2.4.99.3) (ST6GalNAc I), which transfers a sialic acid residue in ␣2,6linkage to the GalNAc␣1-O-Ser/Thr structure. However, established breast cancer cell lines express neither ST6GalNAc I nor sialyl-Tn. We have previously shown that stable transfection of MDA-MB-231, a human breast cancer cell line, with ST6GalNAc I cDNA induces sialyl-Tn antigen (STn) expression. We report here the modifications of the O-glycosylation pattern of a MUC1-related recombinant protein secreted by MDA-MB-231 sialyl-Tn positive cells. We also show that sialyl-Tn expression and concomitant changes in the overall O-glycan profiles induce a decrease of adhesion and an increase of migration of MDA-MB-231. Moreover, STn positive clones exhibit an increased tumour growth in severe combined immunodeficiency (SCID) mice. These observations suggest that modification of the O-glycosylation pattern induced by ST6GalNAc I expression are sufficient to enhance the tumourigenicity of MDA-MB-231 breast cancer cells.
The discovery of cancer stem cells (CSCs) fundamentally advanced our understanding of the mechani... more The discovery of cancer stem cells (CSCs) fundamentally advanced our understanding of the mechanisms governing breast cancer development. However, the stimuli that control breast CSC self-renewal and differentiation have still not been fully detailed. We previously showed that nerve growth factor (NGF) and its precursor proNGF can stimulate breast cancer cell growth and invasion in an autocrine manner. In this study, we investigated the effects of NGF and proNGF on the breast CSC compartment and found that NGF or proNGF enrich for CSCs in several breast cancer cell lines. This enrichment appeared to be achieved by increasing the number of symmetric divisions of quiescent/slow-proliferating CSCs. Interestingly, in vitro NGF pretreatment of MCF-7 luminal breast cancer cells promoted epithelial to mesenchymal transition in tumors of severe combined immunodeficient mice. Furthermore, p75(NTR), the common receptor for both neurotrophins and proneurotrophins, mediated breast CSC self-renewal by regulating the expression of pluripotency transcription factors. Our data indicate, for the first time, that the NGF/proNGF/p75(NTR) axis plays a critical role in regulating breast CSC self-renewal and plasticity.
Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue 2,6-linked to GalNA... more Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue 2,6-linked to GalNAc-O-Ser/Thr. The biosynthesis of STn is mediated by a specific sialyltransferase termed ST6GalNAc I, which competes with O-glycans elongating glycosyltransferases and prevents cancer cells from exhibiting longer O-glycans. While weakly expressed by fetal and normal adult tissues, STn is expressed by more than 80% of human carcinomas and in all cases, STn detection is associated with adverse outcome and decreased overall survival for the patients. Because of its pan-carcinoma expression associated with an adverse outcome, an anti-cancer vaccine, named Theratope, has been designed towards the STn epitope. In spite of the great enthusiasm around this immunotherapy, Theratope failed on Phase III clinical trial. However, in lieu of missing this target, one should consider to revise the Theratope design and the actual facts. In this review, we highlight the many lessons that can be learned from this failure from the immunological standpoint, as well as from the drug design and formulation and patient selection. Moreover, an irrefutable knowledge is arising from novel immunotherapies targeting other carbohydrate antigens and STn carrier proteins, such as MUC1, that will warrantee the future development of more successful anti-STn immunotherapy strategies.
ABSTRACT Sialic acids are nine-carbon acidic monosaccharides found in terminal position of glycan... more ABSTRACT Sialic acids are nine-carbon acidic monosaccharides found in terminal position of glycan chains. The sialylation of cell surface glycoconjugates is frequently altered in cancers, resulting in the expression of sialylated tumor-associated carbohydrate antigens that are specific markers for this disease. Because sialylated glycans are involved in many biological processes, their expression by tumor cells is often associated with increased aggressiveness and metastatic potential of the tumors. The sialylated tumor-associated carbohydrate antigens are usually weakly expressed by healthy tissues and can be therefore used as immunotherapeutic targets for anticancer vaccines. This chapter summarizes the main tumor-associated sialylated structures and their role in cancer cells biology as well as their use for the development of anticancer vaccines.
Recent data have underlined a possible role of G D3 synthase (GD3S) and complex gangliosides in E... more Recent data have underlined a possible role of G D3 synthase (GD3S) and complex gangliosides in Estrogen Receptor (ER) negative breast cancer progression. Here, we describe the main transcript of the GD3S coding gene ST8SIA1 expressed in breast tumors. We characterized the corresponding core promoter in Hs578T breast cancer cells and showed that estradiol decreases ST8SIA1 mRNA expression in ER-positive MCF-7 cells and ERa-transfected ER-negative Hs578T cells. The activity of the core promoter sequence of ST8SIA1 is also repressed by estradiol. The core promoter of ST8SIA1 contains two putative Estrogen Response Elements (ERE) that were not found to be involved in the promoter activity pathway. However, NFkB was shown to be involved in ST8SIA1 transcriptional activation and we demonstrated that estradiol prevents NFkB to bind to ST8SIA1 core promoter in ERa expressing breast cancer cells by inhibiting p65 and p50 nucleus localization. The activation of NFkB pathway in ER-negative tumors, due to the absence of estradiol signaling, might explain the overexpression of G D3 synthase in this tumor subtype.
Gangliosides, the glycosphingolipids carrying one or several sialic acid residues, are located on... more Gangliosides, the glycosphingolipids carrying one or several sialic acid residues, are located on the outer leaflet of the plasma membrane in glycolipid-enriched microdomains, where they interact with molecules of signal transduction pathways including receptors tyrosine kinases (RTKs). The role of gangliosides in the regulation of signal transduction has been reported in many cases and in a large number of cell types. In this review, we summarize the current knowledge on the biosynthesis of gangliosides and the mechanism by which they regulate RTKs signaling.
Background: Aberrant glycosylation is a common feature of breast cancer. Results: Cyclooxygenase-... more Background: Aberrant glycosylation is a common feature of breast cancer. Results: Cyclooxygenase-2 (COX-2), an enzyme associated with tumorigenesis in breast cancer, up-regulated the sialyltransferase ST3Gal-I. Conclusion: COX-2 can regulate the expression of ST3Gal-I in breast cancer Significance: Some of the tumorigenic properties associated with COX-2 may be the result of up-regulating ST3Gal-I that can alter the O-linked glycosylation of tumors.
The glycome acts as an essential interface between cells and the surrounding microenvironment. Ho... more The glycome acts as an essential interface between cells and the surrounding microenvironment. However, changes in glycosylation occur in nearly all breast cancers, which can alter this interaction. Here, we report that profiles of glycosylation vary between ER-positive and ER-negative breast cancers. We found that genes involved in the synthesis of sialyl-Lewis x (sLe x ; FUT3, FUT4, and ST3GAL6) are significantly increased in estrogen receptor alpha-negative (ER-negative) tumors compared with ER-positive ones. SLe x expression had no influence on the survival of patients whether they had ER-negative or ER-positive tumors. However, high expression of sLe x in ERpositive tumors was correlated with metastasis to the bone where sLe x receptor E-selectin is constitutively expressed. The ER-positive ZR-75-1 and the ER-negative BT20 cell lines both express sLe x but only ZR-75-1 cells could adhere to activated endothelial cells under dynamic flow conditions in a sLe x and E-selectin-dependent manner. Moreover, L/P-selectins bound strongly to ER-negative MDA-MB-231 and BT-20 cell lines in a heparan sulfate (HS)-dependent manner that was independent of sLe x expression. Expression of glycosylation genes involved in heparan biosynthesis (EXT1 and HS3ST1) was increased in ER-negative tumors. Taken together, our results suggest that the context of sLe x expression is important in determining its functional significance and that selectins may promote metastasis in breast cancer through protein-associated sLe x and HS glycosaminoglycans. Cancer Res; 71(24); 7683-93. Ó2011 AACR.
One of the hallmarks of breast adenocarcinomas is the over expression and aberrant localization o... more One of the hallmarks of breast adenocarcinomas is the over expression and aberrant localization of membranebound mucins, such as MUC1 and MUC4 . Mucins are characterized by a large number of tandem repeated domains, rich in serine and threonine, which are therefore densely O-glycosylated.
Introduction: Detection of serum biomarkers for early diagnosis of breast cancer remains an impor... more Introduction: Detection of serum biomarkers for early diagnosis of breast cancer remains an important goal. Changes in the structure of O-linked glycans occur in all breast cancers resulting in the expression of glycoproteins that are antigenically distinct. Indeed, the serum assay widely used for monitoring disease progression in breast cancer (CA15.3), detects a glycoprotein (MUC1), but elevated levels of the antigen cannot be detected in early stage patients. However, since the immune system acts to amplify the antigenic signal, antibodies can be detected in sera long before the antigen. We have exploited the change in O-glycosylation to measure autoantibody responses to cancer-associated glycoforms of MUC1 in sera from early stage breast cancer patients.
Distant metastases account for the majority of cancer-related deaths in breast cancer. The rate a... more Distant metastases account for the majority of cancer-related deaths in breast cancer. The rate and site of metastasis differ between estrogen receptor (ER)-negative and ER-positive tumours, and metastatic fate can be very diverse even within the ER-negative group. Characterisation of new pro-metastatic markers may help to identify patients with higher risk and improve their care accordingly. Selectin ligands aberrantly expressed by cancer cells promote metastasis by enabling interaction between circulating tumour cells and endothelial cells in distant organs. These ligands consist in carbohydrate molecules, such as sialyl-Lewis x antigen (sLex), borne by glycoproteins or glycolipids on the cancer cell surface. We have previously demonstrated that the molecular scaffold presenting sLex to selectins (e.g. glycolipid vs. glycoproteins) was crucial for these interactions to occur. Moreover, we reported that detection of sLex alone in breast carcinomas was only of limited prognostic val...
Around 7-17% of metastatic breast cancer patients will develop brain metastases, associated with ... more Around 7-17% of metastatic breast cancer patients will develop brain metastases, associated with a poor prognosis. To reach the brain parenchyma, cancer cells need to cross the highly restrictive endothelium of the Blood-Brain Barrier (BBB). As treatments for brain metastases are mostly inefficient, preventing cancer cells to reach the brain could provide a relevant and important strategy. For that purpose an in vitro approach is required to identify cellular and molecular interaction mechanisms between breast cancer cells and BBB endothelium, notably at the early steps of the interaction. However, while numerous studies are performed with in vitro models, the heterogeneity and the quality of BBB models used is a limitation to the extrapolation of the obtained results to in vivo context, showing that the choice of a model that fulfills the biological BBB characteristics is essential. Therefore, we compared pre-established and currently used in vitro models from different origins (bovine, mice, human) in order to define the most appropriate tool to study interactions between breast cancer cells and the BBB. On each model, the BBB properties and the adhesion capacities of breast cancer cell lines were evaluated. As endothelial cells represent the physical restriction site of the BBB, all the models consisted of endothelial cells from animal or human origins. Among these models, only the in vitro BBB model derived from human stem cells both displayed BBB properties and allowed measurement of meaningful different interaction capacities of the cancer cell lines. Importantly, the measured adhesion and transmigration were found to be in accordance with the cancer cell lines molecular subtypes. In addition, at a molecular level, the inhibition of ganglioside biosynthesis highlights the potential role of glycosylation in breast cancer cells adhesion capacities.
Changes in cell surface glycosylation are common modifications that occur during oncogenesis, lea... more 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.
H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play ... more H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play key roles in the progression and metastasis of cancers from different tissue origins. We have previously shown that the H19 gene is activated by growth factors and increases breast cancer cell invasion. In this study, we established H19/ miR-675 ectopic expression models of MDA-MB-231 breast cancer cells to further investigate the underlying mechanisms of H19 oncogenic action. We showed that overexpression of H19/miR-675 enhanced the aggressive phenotype of breast cancer cells including increased cell proliferation and migration in vitro, and increased tumor growth and metastasis in vivo. Moreover, we identified ubiquitin ligase E3 family (c-Cbl and Cbl-b) as direct targets of miR-675 in breast cancer cells. Using a luciferase assay, we demonstrated that H19, through its microRNA, decreased both c-Cbl and Cbl-b expression in all breast cancer cell lines tested. Thus, by directly binding c-Cbl and Cbl-b mRNA, miR-675 increased the stability and the activation of EGFR and c-Met, leading to sustained activation of Akt and Erk as well as enhanced cell proliferation and migration. Our data describe a novel mechanism of protumoral action of H19 in breast cancer.
H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play ... more H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play key roles in the progression and metastasis of cancers from different tissue origins. We have previously shown that the H19 gene is activated by growth factors and increases breast cancer cell invasion. In this study, we established H19/ miR-675 ectopic expression models of MDA-MB-231 breast cancer cells to further investigate the underlying mechanisms of H19 oncogenic action. We showed that overexpression of H19/miR-675 enhanced the aggressive phenotype of breast cancer cells including increased cell proliferation and migration in vitro, and increased tumor growth and metastasis in vivo. Moreover, we identified ubiquitin ligase E3 family (c-Cbl and Cbl-b) as direct targets of miR-675 in breast cancer cells. Using a luciferase assay, we demonstrated that H19, through its microRNA, decreased both c-Cbl and Cbl-b expression in all breast cancer cell lines tested. Thus, by directly binding c-Cbl and Cbl-b mRNA, miR-675 increased the stability and the activation of EGFR and c-Met, leading to sustained activation of Akt and Erk as well as enhanced cell proliferation and migration. Our data describe a novel mechanism of protumoral action of H19 in breast cancer.
Neu5Ac:GalNAc␣2,6-sialyltransferase: CMP-Neu5Ac: R-GalNAc␣1-O-Ser/Thr ␣2,6-sialyltransferase (EC ... more Neu5Ac:GalNAc␣2,6-sialyltransferase: CMP-Neu5Ac: R-GalNAc␣1-O-Ser/Thr ␣2,6-sialyltransferase (EC 2.4.99.3) (ST6GalNAc I), which transfers a sialic acid residue in ␣2,6linkage to the GalNAc␣1-O-Ser/Thr structure. However, established breast cancer cell lines express neither ST6GalNAc I nor sialyl-Tn. We have previously shown that stable transfection of MDA-MB-231, a human breast cancer cell line, with ST6GalNAc I cDNA induces sialyl-Tn antigen (STn) expression. We report here the modifications of the O-glycosylation pattern of a MUC1-related recombinant protein secreted by MDA-MB-231 sialyl-Tn positive cells. We also show that sialyl-Tn expression and concomitant changes in the overall O-glycan profiles induce a decrease of adhesion and an increase of migration of MDA-MB-231. Moreover, STn positive clones exhibit an increased tumour growth in severe combined immunodeficiency (SCID) mice. These observations suggest that modification of the O-glycosylation pattern induced by ST6GalNAc I expression are sufficient to enhance the tumourigenicity of MDA-MB-231 breast cancer cells.
The discovery of cancer stem cells (CSCs) fundamentally advanced our understanding of the mechani... more The discovery of cancer stem cells (CSCs) fundamentally advanced our understanding of the mechanisms governing breast cancer development. However, the stimuli that control breast CSC self-renewal and differentiation have still not been fully detailed. We previously showed that nerve growth factor (NGF) and its precursor proNGF can stimulate breast cancer cell growth and invasion in an autocrine manner. In this study, we investigated the effects of NGF and proNGF on the breast CSC compartment and found that NGF or proNGF enrich for CSCs in several breast cancer cell lines. This enrichment appeared to be achieved by increasing the number of symmetric divisions of quiescent/slow-proliferating CSCs. Interestingly, in vitro NGF pretreatment of MCF-7 luminal breast cancer cells promoted epithelial to mesenchymal transition in tumors of severe combined immunodeficient mice. Furthermore, p75(NTR), the common receptor for both neurotrophins and proneurotrophins, mediated breast CSC self-renewal by regulating the expression of pluripotency transcription factors. Our data indicate, for the first time, that the NGF/proNGF/p75(NTR) axis plays a critical role in regulating breast CSC self-renewal and plasticity.
Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue 2,6-linked to GalNA... more Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue 2,6-linked to GalNAc-O-Ser/Thr. The biosynthesis of STn is mediated by a specific sialyltransferase termed ST6GalNAc I, which competes with O-glycans elongating glycosyltransferases and prevents cancer cells from exhibiting longer O-glycans. While weakly expressed by fetal and normal adult tissues, STn is expressed by more than 80% of human carcinomas and in all cases, STn detection is associated with adverse outcome and decreased overall survival for the patients. Because of its pan-carcinoma expression associated with an adverse outcome, an anti-cancer vaccine, named Theratope, has been designed towards the STn epitope. In spite of the great enthusiasm around this immunotherapy, Theratope failed on Phase III clinical trial. However, in lieu of missing this target, one should consider to revise the Theratope design and the actual facts. In this review, we highlight the many lessons that can be learned from this failure from the immunological standpoint, as well as from the drug design and formulation and patient selection. Moreover, an irrefutable knowledge is arising from novel immunotherapies targeting other carbohydrate antigens and STn carrier proteins, such as MUC1, that will warrantee the future development of more successful anti-STn immunotherapy strategies.
ABSTRACT Sialic acids are nine-carbon acidic monosaccharides found in terminal position of glycan... more ABSTRACT Sialic acids are nine-carbon acidic monosaccharides found in terminal position of glycan chains. The sialylation of cell surface glycoconjugates is frequently altered in cancers, resulting in the expression of sialylated tumor-associated carbohydrate antigens that are specific markers for this disease. Because sialylated glycans are involved in many biological processes, their expression by tumor cells is often associated with increased aggressiveness and metastatic potential of the tumors. The sialylated tumor-associated carbohydrate antigens are usually weakly expressed by healthy tissues and can be therefore used as immunotherapeutic targets for anticancer vaccines. This chapter summarizes the main tumor-associated sialylated structures and their role in cancer cells biology as well as their use for the development of anticancer vaccines.
Recent data have underlined a possible role of G D3 synthase (GD3S) and complex gangliosides in E... more Recent data have underlined a possible role of G D3 synthase (GD3S) and complex gangliosides in Estrogen Receptor (ER) negative breast cancer progression. Here, we describe the main transcript of the GD3S coding gene ST8SIA1 expressed in breast tumors. We characterized the corresponding core promoter in Hs578T breast cancer cells and showed that estradiol decreases ST8SIA1 mRNA expression in ER-positive MCF-7 cells and ERa-transfected ER-negative Hs578T cells. The activity of the core promoter sequence of ST8SIA1 is also repressed by estradiol. The core promoter of ST8SIA1 contains two putative Estrogen Response Elements (ERE) that were not found to be involved in the promoter activity pathway. However, NFkB was shown to be involved in ST8SIA1 transcriptional activation and we demonstrated that estradiol prevents NFkB to bind to ST8SIA1 core promoter in ERa expressing breast cancer cells by inhibiting p65 and p50 nucleus localization. The activation of NFkB pathway in ER-negative tumors, due to the absence of estradiol signaling, might explain the overexpression of G D3 synthase in this tumor subtype.
Gangliosides, the glycosphingolipids carrying one or several sialic acid residues, are located on... more Gangliosides, the glycosphingolipids carrying one or several sialic acid residues, are located on the outer leaflet of the plasma membrane in glycolipid-enriched microdomains, where they interact with molecules of signal transduction pathways including receptors tyrosine kinases (RTKs). The role of gangliosides in the regulation of signal transduction has been reported in many cases and in a large number of cell types. In this review, we summarize the current knowledge on the biosynthesis of gangliosides and the mechanism by which they regulate RTKs signaling.
Background: Aberrant glycosylation is a common feature of breast cancer. Results: Cyclooxygenase-... more Background: Aberrant glycosylation is a common feature of breast cancer. Results: Cyclooxygenase-2 (COX-2), an enzyme associated with tumorigenesis in breast cancer, up-regulated the sialyltransferase ST3Gal-I. Conclusion: COX-2 can regulate the expression of ST3Gal-I in breast cancer Significance: Some of the tumorigenic properties associated with COX-2 may be the result of up-regulating ST3Gal-I that can alter the O-linked glycosylation of tumors.
The glycome acts as an essential interface between cells and the surrounding microenvironment. Ho... more The glycome acts as an essential interface between cells and the surrounding microenvironment. However, changes in glycosylation occur in nearly all breast cancers, which can alter this interaction. Here, we report that profiles of glycosylation vary between ER-positive and ER-negative breast cancers. We found that genes involved in the synthesis of sialyl-Lewis x (sLe x ; FUT3, FUT4, and ST3GAL6) are significantly increased in estrogen receptor alpha-negative (ER-negative) tumors compared with ER-positive ones. SLe x expression had no influence on the survival of patients whether they had ER-negative or ER-positive tumors. However, high expression of sLe x in ERpositive tumors was correlated with metastasis to the bone where sLe x receptor E-selectin is constitutively expressed. The ER-positive ZR-75-1 and the ER-negative BT20 cell lines both express sLe x but only ZR-75-1 cells could adhere to activated endothelial cells under dynamic flow conditions in a sLe x and E-selectin-dependent manner. Moreover, L/P-selectins bound strongly to ER-negative MDA-MB-231 and BT-20 cell lines in a heparan sulfate (HS)-dependent manner that was independent of sLe x expression. Expression of glycosylation genes involved in heparan biosynthesis (EXT1 and HS3ST1) was increased in ER-negative tumors. Taken together, our results suggest that the context of sLe x expression is important in determining its functional significance and that selectins may promote metastasis in breast cancer through protein-associated sLe x and HS glycosaminoglycans. Cancer Res; 71(24); 7683-93. Ó2011 AACR.
One of the hallmarks of breast adenocarcinomas is the over expression and aberrant localization o... more One of the hallmarks of breast adenocarcinomas is the over expression and aberrant localization of membranebound mucins, such as MUC1 and MUC4 . Mucins are characterized by a large number of tandem repeated domains, rich in serine and threonine, which are therefore densely O-glycosylated.
Introduction: Detection of serum biomarkers for early diagnosis of breast cancer remains an impor... more Introduction: Detection of serum biomarkers for early diagnosis of breast cancer remains an important goal. Changes in the structure of O-linked glycans occur in all breast cancers resulting in the expression of glycoproteins that are antigenically distinct. Indeed, the serum assay widely used for monitoring disease progression in breast cancer (CA15.3), detects a glycoprotein (MUC1), but elevated levels of the antigen cannot be detected in early stage patients. However, since the immune system acts to amplify the antigenic signal, antibodies can be detected in sera long before the antigen. We have exploited the change in O-glycosylation to measure autoantibody responses to cancer-associated glycoforms of MUC1 in sera from early stage breast cancer patients.
Distant metastases account for the majority of cancer-related deaths in breast cancer. The rate a... more Distant metastases account for the majority of cancer-related deaths in breast cancer. The rate and site of metastasis differ between estrogen receptor (ER)-negative and ER-positive tumours, and metastatic fate can be very diverse even within the ER-negative group. Characterisation of new pro-metastatic markers may help to identify patients with higher risk and improve their care accordingly. Selectin ligands aberrantly expressed by cancer cells promote metastasis by enabling interaction between circulating tumour cells and endothelial cells in distant organs. These ligands consist in carbohydrate molecules, such as sialyl-Lewis x antigen (sLex), borne by glycoproteins or glycolipids on the cancer cell surface. We have previously demonstrated that the molecular scaffold presenting sLex to selectins (e.g. glycolipid vs. glycoproteins) was crucial for these interactions to occur. Moreover, we reported that detection of sLex alone in breast carcinomas was only of limited prognostic val...
Around 7-17% of metastatic breast cancer patients will develop brain metastases, associated with ... more Around 7-17% of metastatic breast cancer patients will develop brain metastases, associated with a poor prognosis. To reach the brain parenchyma, cancer cells need to cross the highly restrictive endothelium of the Blood-Brain Barrier (BBB). As treatments for brain metastases are mostly inefficient, preventing cancer cells to reach the brain could provide a relevant and important strategy. For that purpose an in vitro approach is required to identify cellular and molecular interaction mechanisms between breast cancer cells and BBB endothelium, notably at the early steps of the interaction. However, while numerous studies are performed with in vitro models, the heterogeneity and the quality of BBB models used is a limitation to the extrapolation of the obtained results to in vivo context, showing that the choice of a model that fulfills the biological BBB characteristics is essential. Therefore, we compared pre-established and currently used in vitro models from different origins (bovine, mice, human) in order to define the most appropriate tool to study interactions between breast cancer cells and the BBB. On each model, the BBB properties and the adhesion capacities of breast cancer cell lines were evaluated. As endothelial cells represent the physical restriction site of the BBB, all the models consisted of endothelial cells from animal or human origins. Among these models, only the in vitro BBB model derived from human stem cells both displayed BBB properties and allowed measurement of meaningful different interaction capacities of the cancer cell lines. Importantly, the measured adhesion and transmigration were found to be in accordance with the cancer cell lines molecular subtypes. In addition, at a molecular level, the inhibition of ganglioside biosynthesis highlights the potential role of glycosylation in breast cancer cells adhesion capacities.
Changes in cell surface glycosylation are common modifications that occur during oncogenesis, lea... more 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.
H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play ... more H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play key roles in the progression and metastasis of cancers from different tissue origins. We have previously shown that the H19 gene is activated by growth factors and increases breast cancer cell invasion. In this study, we established H19/ miR-675 ectopic expression models of MDA-MB-231 breast cancer cells to further investigate the underlying mechanisms of H19 oncogenic action. We showed that overexpression of H19/miR-675 enhanced the aggressive phenotype of breast cancer cells including increased cell proliferation and migration in vitro, and increased tumor growth and metastasis in vivo. Moreover, we identified ubiquitin ligase E3 family (c-Cbl and Cbl-b) as direct targets of miR-675 in breast cancer cells. Using a luciferase assay, we demonstrated that H19, through its microRNA, decreased both c-Cbl and Cbl-b expression in all breast cancer cell lines tested. Thus, by directly binding c-Cbl and Cbl-b mRNA, miR-675 increased the stability and the activation of EGFR and c-Met, leading to sustained activation of Akt and Erk as well as enhanced cell proliferation and migration. Our data describe a novel mechanism of protumoral action of H19 in breast cancer.
H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play ... more H19 is a long non-coding RNA precursor of miR-675microRNA. H19 is increasingly described to play key roles in the progression and metastasis of cancers from different tissue origins. We have previously shown that the H19 gene is activated by growth factors and increases breast cancer cell invasion. In this study, we established H19/ miR-675 ectopic expression models of MDA-MB-231 breast cancer cells to further investigate the underlying mechanisms of H19 oncogenic action. We showed that overexpression of H19/miR-675 enhanced the aggressive phenotype of breast cancer cells including increased cell proliferation and migration in vitro, and increased tumor growth and metastasis in vivo. Moreover, we identified ubiquitin ligase E3 family (c-Cbl and Cbl-b) as direct targets of miR-675 in breast cancer cells. Using a luciferase assay, we demonstrated that H19, through its microRNA, decreased both c-Cbl and Cbl-b expression in all breast cancer cell lines tested. Thus, by directly binding c-Cbl and Cbl-b mRNA, miR-675 increased the stability and the activation of EGFR and c-Met, leading to sustained activation of Akt and Erk as well as enhanced cell proliferation and migration. Our data describe a novel mechanism of protumoral action of H19 in breast cancer.
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Papers by Sylvain Julien