Biomedical subjects

Fabien Calvo

Publications and source records attributed to Fabien Calvo.

At least 19 recordsLinked to original sources

PubMed2007

Extracellular matrix metalloproteinase inducer up-regulates the urokinase-type plasminogen activator system promoting tumor cell invasion.

Extracellular matrix metalloproteinase inducer (EMMPRIN) is a membrane glycoprotein overexpressed in many cancer tissues and is known for its ability to stimulate MMP expression. In this work, we show that EMMPRIN is also a regulator of the urokinase-type plasminogen activation (uPA) system of serine proteases, thus participating to the increase of the overall proteolytic function of the cancer cells. Enhanced EMMPRIN expression in a tumorigenic breast epithelial cell line NS2T2A increased the levels of uPA, uPA receptor, and the uPA inhibitor plasminogen activator inhibitor-1 (PAI-1), as measured by quantitative reverse transcription-PCR, Western blot, and plasminogen-casein zymography. This response was down-regulated by either EMMPRIN small interfering RNA or a blocking antibody to EMMPRIN. EMMPRIN-containing purified membrane fraction from Chinese hamster ovary cells when added exogenously to NS2T2A cells induced a similar activation of the uPA/PAI-1 system. Additionally, overexpression of EMMPRIN in NS2T2A cells increased uPA levels in cocultured endothelial cells, showing a paracrine regulation loop involving a tumor-stroma interaction. EMMPRIN-expressing cells also exhibited enhanced invasive potential in vitro, and the use of amiloride (uPA inhibitor) and marimastat (MMP inhibitor) showed that the two proteolytic systems reduced alone and in combination the invasive potential mediated through EMMPRIN. These data show a novel regulatory pathway for uPA activity and suggest that EMMPRIN is involved in uPA dysregulation observed in cancer.

Animals↗

PubMed2007

Potential opportunity in the development of new therapeutic agents based on endogenous and exogenous inhibitors of the proprotein convertases.

The proprotein convertases (PCs) are responsible for the endoproteolytic processing of various protein precursors (e.g., growth factors, receptors, adhesion molecules, and matrix metalloproteinases) implicated in several diseases such as obesity, diabetes, atherosclerosis, cancer, and Alzheimer disease. The potential clinical and pharmacological role of the PCs has fostered the development of various PC-inhibitors. In this review we summarized the recent findings on PCs inhibitors, their mode of actions and potential use in the therapy of various diseases.

Humans↗

PubMed2006

Platelets, thrombospondin-1 and human dermal fibroblasts cooperate for stimulation of endothelial cell tubulogenesis through VEGF and PAI-1 regulation.

During cutaneous wound repair, platelets, dermal fibroblasts (DF) and endothelial cells all cooperate. We have presently investigated the regulation of endothelial cell tubulogenesis by human platelet thrombospondin-1 (TSP-1), in comparison to transforming growth factor-beta1 (TGF-beta1) and total platelet lysates (PL), in a fibrin matrix cell culture system incorporating DF. TSP-1, TGF-beta1 and PL all stimulated VEGF expression in DF dose dependently at mRNA and protein level. TSP-1- and PL-treated DF supernatants significantly stimulated capillary-like structure formation (tubulogenesis) by dermal microvascular endothelial cells (HMEC-1 and HDMEC), in part via VEGF, as confirmed with neutralizing anti-VEGF antibodies. In contrast, TGF-beta1-treated DF supernatants did not induce tubulogenesis. This apparent discrepancy could be explained by the differential expression regulation in HMEC-1 of fibrinolysis and metalloproteinase mediators by TSP-1 and TGF-beta1. TSP-1 potently reduced the expression of plasminogen activator inhibitor-1 (PAI-1) (mRNA and protein), whereas TGF-beta1 enhanced it. The crucial role of PAI-1 in tubulogenesis was confirmed via the addition of active recombinant PAI-1, which abrogated tubulogenesis. In contrast, neutralizing PAI-1 antibodies enhanced tubulogenesis. Our results suggest that platelet TSP-1 released in a wound stimulates endothelial cell tubulogenesis through an upregulation of DF VEGF expression and a downregulation of endothelial cell PAI-1 expression.

Blood Platelets↗

PubMed2006

Consequences of fetal exposure to maternal diabetes in offspring.

CONTEXT: Type 2 diabetes is the result of both genetic and environmental factors. Fetal exposure to maternal diabetes is associated with a higher risk of abnormal glucose homeostasis in offspring beyond that attributable to genetic factors, and therefore, may participate in the excess of maternal transmission of type 2 diabetes. EVIDENCE ACQUISITION: A MEDLINE search covered the period from 1960-2005. EVIDENCE SYNTHESIS: Human studies performed in children and adolescents suggest that offspring who had been exposed to maternal diabetes during fetal life exhibit higher prevalence of impaired glucose tolerance and markers of insulin resistance. Recent studies that directly measured insulin sensitivity and insulin secretion have shown an insulin secretory defect even in the absence of impaired glucose tolerance in adult offspring. In animal models, exposure to a hyperglycemic intrauterine environment also led to the impairment of glucose tolerance in the adult offspring. These metabolic abnormalities were transmitted to the next generations, suggesting that in utero exposure to maternal diabetes has an epigenetic impact. At the cellular level, some findings suggest an impaired pancreatic beta-cell mass and function. Several mechanisms such as defects in pancreatic angiogenesis and innervation, or modification of parental imprinting, may be implicated, acting either independently or in combination. CONCLUSION: Thus, fetal exposure to maternal diabetes may contribute to the worldwide diabetes epidemic. Public health interventions targeting high-risk populations should focus on long-term follow-up of subjects who have been exposed in utero to a diabetic environment and on a better glycemic control during pregnancy.

Adult↗

PubMed2006

Kaposi's sarcoma-associated herpesvirus viremia is associated with the progression of classic and endemic Kaposi's sarcoma.

In order to gain further insight on the role of Kaposi's sarcoma-associated herpesvirus (KSHV) in classic and endemic Kaposi's sarcoma (KS) pathogenesis, we aimed to determine (i) whether KSHV is detectable in peripheral blood mononuclear cells (PBMCs), (ii) which PBMCs subpopulation harbor the virus, (iii) which clinical, histologic, and immunologic parameters are associated with KSHV viremia in a population of classic and endemic KS. KSHV viremia and various immunologic parameters were screened on 81 patients. KSHV viremia was positive in 58% of the patients. KSHV was detected in B cells, T cells, and monocytes. CD34+ cells depleted in circulating endothelial cells (CECs) were never infected and 50% of the patients tested had CECs infected by KSHV. We observed a significant increase of IL-2 and IFN-gamma production by CD4 T cells and an increase of IFN-gamma production by CD8 T cells compared to control patients. KS progression (P = 0.001) and KS staging (P = 0.03) were significantly and independently associated with positive KSHV viremia. Our results show that there is no specific immunosuppression in classic or endemic KS. We showed that KSHV can be detected within CECs and that KSHV viremia could be an indicator of circulating mature or precursor spindle cells.

Aged↗

PubMed2006

Preclinical and clinical development of novel agents that target the protein kinase C family.

Protein kinase C (PKC) family comprises more than 12 serine-/threonine-specific isoenzymes. PKC isoenzymes play a complex role in the transduction of signal from tyrosine kinase receptor modulating proliferation, cell cycle, apoptosis, invasion, differentiation, and senescence in both cancer cells and endothelial cells. Thereby, inhibition and/or activation of specific PKCs is thought to control tumor growth by interacting directly with cancer cells and indirectly by blocking tumor angiogenesis. Furthermore, PKCs are known to modulate multi-drug resistance, providing a rational for the combination of PKCs modulators with classical cytotoxic drugs. During the past few years, preclinical and clinical data with first-generation PKC inhibitors/activators provided insight that PKCs may indeed represent attractive targets for the discovery of small molecules with new anticancer properties. In this review, we will provide an overview on the current understanding of PKC participation in chemotherapeutic resistance, the possible implications in cancer treatment, and the potential of most recent PKC inhibitors in molecular cancer therapeutics.

Antineoplastic Agents↗

PubMed2006

Proprotein convertases: lessons from knockouts.

The physiological role of the subtilisin/kexin-like proprotein convertases (PCs) in rodents has been examined through the use of knockout mice. This review will summarize the major in vivo defects that result from the disruption of the expression of their genes. This includes abnormal embryonic development, hormonal disorder, infertility, and/or modified lipid/sterol metabolism. Members of the PC family play a central role in the processing of various protein precursors ranging from hormones and growth factors to bacterial toxins and viral glycoproteins. Proteolysis occurring at basic residues is mediated by the basic amino acid-specific proprotein convertases, namely: PC1/3, PC2, furin, PACE4, PC4, PC5/6, and PC7. In contrast, proteolysis at nonbasic residues is performed by the subtilisin/kexin-like isozyme-1 (SKI-1/S1P) and the newly identified neural apoptosis-regulated convertase-1 (PCSK9/NARC-1). In addition to their requirement for many physiological processes, these enzymes are also involved in various pathologies such as cancer, obesity, diabetes, lipid disorders, infectious diseases, atherosclerosis and neurodegenerative diseases.

Animals↗

PubMed2005

Regulation of the stepwise proteolytic cleavage and secretion of PDGF-B by the proprotein convertases.

Platelet-derived growth factor-B (PDGF-B) is important for normal tissue growth and maintenance and its overexpression has been linked to several diseases, including cancer, fibrotic disease and atherosclerosis. Here, we show that synthesized as a precursor, proPDGF-B is converted to a mature form by proteolytic cleavage at two sites and its N-terminal cleavage is a prerequisite for processing at its C-terminus. The first cleavage occurs at residues RGRR81/, and the second cleavage close to residues ARPVT190, just before the C-terminal amino-acid sequence crucial for PDGF-B retention to cell surface. Cotransfection of a Furin-deficient cell line LoVo-C5 with proPDGF-B and different PC members revealed that Furin, PACE4, PC5, and PC7 are candidate proPDGF-B convertases. This finding is consistent with the in vitro digestions of a synthetic peptide mimicking the cleavage site of proPDGF-B. The processing of proPDGF-B is blocked by site-directed mutagenesis of the RGRR81/ sequence and by various PC inhibitors. Mutation of the PDGF-A and/or PDGF-B convertase sites, revealed that processing of both A and B chains is required for the formation of mature PDGF-B dimers and that the processing of the B chain controls the level of secreted and matrix-bound PDGF-BB forms. Our findings emphasize the importance of the convertase-directed processing of proPDGF-B at the RGRR81/ sequence for PDGF-B maturation and secretion.

Amino Acid Sequence↗

PubMed2005

VEGF189 stimulates endothelial cells proliferation and migration in vitro and up-regulates the expression of Flk-1/KDR mRNA.

The vascular endothelial growth factor (VEGF) is a critical factor for development of the vascular system in physiological and pathological angiogenesis. This growth factor exists under at least three isoforms, VEGF120/121, VEGF164/165 and VEGF188/189 which are generated by alternative splicing. VEGF isoforms have different affinities for heparan sulphate as well as for VEGF receptors, and may play distinct roles in vascular development. The role of VEGF189 as an endothelial mitogen, however, remains controversial. VEGF189 is almost entirely bound to the cell surface or extracellular matrix, and is considered active after its cleavage and release from its extracellular binding site. In the present study, we demonstrate that VEGF189 induces endothelial cell proliferation and migration in vitro. The 30-60% increase observed with VEGF189 (10 ng/ml) in HUVEC proliferation was similar to that observed with VEGF165. However, the proliferative effect observed with VEGF189 appeared dependent on the origin of the endothelial cell, since the proliferation was clearly observed with HUVEC but not with BAEC or capillary endothelial cells from dermis (HMEC). The effect of VEGF189 on endothelial cell migration was also analyzed using the wound healing and the Boyden chamber assays. The migration effect was observed with BAEC which do not proliferate with VEGF189, suggesting that different mechanisms are involved in proliferation and migration. In addition, VEGF189 as well as VEGF165 induced a 2-fold increase of Flk-1/KDR expression in HUVEC, the receptor involved in proliferation and migration of endothelial cells. In the Matrigel plug assay in vivo, both VEGF189 and 165 (100 ng/ml) increased the infiltration of endothelial cells. These data suggest that VEGF189 induced endothelial cell migration and proliferation under certain circumstances.

Animals↗

PubMed2005

Characterizations of irofulven cytotoxicity in combination with cisplatin and oxaliplatin in human colon, breast, and ovarian cancer cells.

PURPOSE: This study assessed the cytotoxic effects of irofulven in combination with oxaliplatin and cisplatin in a panel of human cancer cell lines. METHODS: Growth inhibition studies were performed using the human HT29 colon cancer cell line, irofulven-resistant derivative HT29/IF2, breast cancer cell line MCF7, and ovarian cancer line CAOV3. Irofulven-oxaliplatin combinations were compared with irofulven-cisplatin combinations in the same cell lines using similar experimental settings. Cells were exposed for 1 h to irofulven and then for 24 h to oxaliplatin or cisplatin and vice versa. RESULTS: Single agent irofulven displayed cytotoxic effects against human colon HT29 cells, human breast cancer cell lines including MCF7, SKBR3, and ZR-75-1, and human ovarian cancer cell lines CAOV3, OVCAR3, and IGROV1, with OVCAR3 being the most sensitive cancer cell line (IC50: 2.4 microM). In all tested cell lines the oxaliplatin-irofulven combination led to clear evidence of synergistic activity. In HT29 and HT29/IF2, the sequence oxaliplatin followed by irofulven appears to be the most effective whereas in MCF7 cells, irofulven given prior to or simultaneously with oxaliplatin is more effective than the other schedule. The combination displays additive activity toward CAOV3 ovarian cells when irofulven was administered prior to or simultaneously with oxaliplatin and partially synergistic when oxaliplatin was followed by irofulven. In most of the cell lines, the sequence oxaliplatin followed by irofulven appears to be the most effective as compared to other schedules. A combination of irofulven with cisplatin has the same efficacy as with oxaliplatin for the same cell lines. Cell cycle studies show that irofulven increases the proportion of cells in the S phase. Cisplatin-irofulven and oxaliplatin-irofulven combinations block cells in G1/S and potently induce apoptosis. CONCLUSION: Irofulven displays synergistic antiproliferative and pro-apoptotic effects when combined with oxaliplatin over a broad range of concentrations in human colon and breast cancer cells. Acquired resistance to irofulven has limited impact on the effects of cisplatin-irofulven and oxaliplatin-irofulven combinations. Based on these data, irofulven-oxaliplatin and cisplatin-irofulven combinations will be further explored in clinical trials, favoring the use schedules of oxaliplatin given prior to irofulven in patients with cancer.

Algorithms↗

PubMed2005

Differential expression of extracellular matrix metalloproteinase inducer (CD147) in normal and ulcerated corneas: role in epithelio-stromal interactions and matrix metalloproteinase induction.

Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally identified on the tumor cell surface as an inducer of matrix metalloproteinase (MMP) production in neighboring fibroblasts. Here we demonstrate a role for EMMPRIN in MMP induction during corneal wound healing. MMP and EMMPRIN expression was analyzed in normal and ulcerated human corneas, as well as in corneal epithelial and stromal cells in culture using confocal microscopy, zymography, immunoblots, and real-time polymerase chain reaction. In normal cornea EMMPRIN was predominantly expressed in the epithelium but was markedly induced in the anterior stroma of ulcerated corneas. This coincided with MMP-2 induction that co-localized with EMMPRIN at the epithelio-stromal boundary. The role of epithelial-stromal interaction in MMP induction was investigated in an in vitro co-culture system and demonstrated an induction and co-localization of EMMPRIN and MMP-2 in the fibroblasts at the interface with epithelial cells. Direct contact of fibroblasts with EMMPRIN-containing purified epithelial cell membranes also induced MMP-1, MMP-2, and EMMPRIN and this was inhibited by a blocking anti-EMMPRIN antibody, suggesting that EMMPRIN was primarily responsible for this induction. These findings, and the up-regulation of EMMPRIN by epidermal growth factor and transforming growth factor-beta, demonstrate a role for EMMPRIN in wound healing and suggest that sustained local up-regulation of EMMPRIN and MMPs in chronic situations in which healing is delayed may lead to excessive matrix degradation and corneal melts.

Antigens, CD↗

PubMed2005

[Amphiregulin antisense RNA expression inhibits angiogenesis of human breast cancer in nude mice].

OBJECTIVE: To investigate the anti-angiogenic effect of amphiregulin (AR) antisense RNA expression in breast cancer. METHODS: Human AR cDNA antisense plasmid was transfected into NS2T2A1 cells (a human breast cancer cell line). Two selected clones expressed AR antisense RNA (AR AS1 and AR AS3 cell lines) in which AR protein expression was reduced. Control cell line NS2T2A1 V was obtained by empty vector transfection. These cells were injected subcutaneously into nude mice. The effects of conditioned media on proliferation of human microvascular endothelial cells (HMEC) were evaluated and VEGF secreted by the cells was measured by ELISA method. In tumor tissues, VEGF expression levels were measured by quantitative RT-PCR, and CD31-immunostaining was used for intra-tumoral vascular quantification. RESULTS: The proliferation index of HMEC cells grown in conditioned media with AR AS1 and AR AS3 was significantly reduced in comparison with that of control cells, accompanied by a decreased VEGF secretion. In tumors derived from AR AS1 and AR AS3 cells, intra-tumoral vascularization was reduced to about 50% of that derived from control cell line, accompanied with a decrease of VEGF expression. CONCLUSION: Amphiregulin antisense RNA expression inhibits efficiently the angiogenesis in breast cancer, suggesting this growth factor could represent a novel therapeutic target in breast cancer.

Adenocarcinoma↗

PubMed2004

Receptor for the globular heads of C1q (gC1q-R, p33, hyaluronan-binding protein) is preferentially expressed by adenocarcinoma cells.

Combinatorial Ig libraries with phage display allow in vitro generation of human Ig fragments without the need to maintain hybridomas in ongoing cell culture or to select circulating Ig from human serum. Identifying tumor-associated antigens on the surface of intact tumor cells, as opposed to purified proteins, presents a challenge due to the difficulty of preserving complex 3-D epitopic sites on the cell surface, the variable expression of antigens on different malignant cell types and the stereotactic interference of closely associated proteins on the intact membrane surface limiting accessibility to antigenic sites. A combinatorial Ig library of 10(10) clones was generated from the cDNA of PBMCs derived from patients with breast adenocarcinoma. Following subtractive panning, the library was enriched for Ig (Fab fragment) binding to intact adenocarcinoma cells and the resultant Fabs were screened against a cDNA expression library, itself generated from breast cancer cells. Using this approach, we isolated clones from the cDNA library expressing gC1q-R, a glycoprotein comprising the major structure of C1, the first component of the complement system. gC1q-R is a 33 kDa glycoprotein expressed not only on the cell surface but also intracellularly, with motifs that target it to mitochondria and complete homology with HABP and human HeLa cell protein p32, which is copurified with pre-mRNA SF2. Sequencing of the gene encoding tumor-associated gC1q-R did not reveal any consistent tumor-specific mutations. However, histochemical staining with anti-gC1q-R MAb demonstrated marked differential expression of gC1q-R in thyroid, colon, pancreatic, gastric, esophageal and lung adenocarcinomas compared to their nonmalignant histologic counterparts. In contrast, differential expression was not seen in endometrial, renal and prostate carcinomas. Despite high expression in breast carcinoma, gC1q-R was also expressed in nonmalignant breast tissue. Although the precise relation of gC1q-R to carcinogenesis remains unclear, our finding of tumor overexpression and the known multivalent binding of gC1q-R to not only C1q itself but also a variety of circulating plasma proteins as well as its involvement in cell-to-cell interactions suggest that gC1q-R may have a role in tumor metastases and potentially serve in molecule-specific targeting of malignant cells.

Adenocarcinoma↗

PubMed2004

Vascular endothelial growth factor-A is expressed both on lymphoma cells and endothelial cells in angioimmunoblastic T-cell lymphoma and related to lymphoma progression.

Vascular endothelial growth factor-A (VEGF-A), a main stimulator of endothelial cell proliferation, plays an important role on tumor angiogenesis. Angioimmunoblastic T-cell lymphoma (AITL) show the most prominent vascular component among lymphomas and their prognosis is difficult to predict. To assess the clinical significance of VEGF-A in AITL, VEGF-A gene expression was studied in the tumoral lymph nodes of 24 patients using laser microdissection and quantitative polymerase chain reaction. VEGF-A gene was overexpressed in both microdissected lymphoma and endothelial cells. Increased levels of VEGF-A gene expression in lymphoma cells, as in endothelial cells, were related to extranodal involvement and to short survival time. Accordingly, VEGF-A protein expression was also found in both types of cells in lymph nodes and bone marrows with lymphomatous involvement. Triple immunofluorescent labeling on lymph node sections showed that VEGF-A protein and its receptor VEGF-R1 were coexpressed on endothelial cells of microvessels in the areas of lymphoma invasion. In these areas, ultrastructural study showed dystrophic microvessels. Taken together, the value of VEGF-A gene expression as an adverse prognostic marker in AITL should thus be considered. In addition to lymphoma cells themselves, the vascular component, a critical pathologic characteristic in AITL, also contributes to lymphoma progression.

Adult↗

PubMed2003

SIAH-1 interacts with CtIP and promotes its degradation by the proteasome pathway.

SIAH-1 and SIAH-2 are the human members of an evolutionary highly conserved E3 ligase family. SIAH-1 is a p53 and p21(Waf-1/Cip-1) induced gene during apoptosis and tumor suppression. In stable-transfected clones of MCF-7 cells, SIAH-1 overexpression was associated with apoptosis, mitotic alterations and p21(Waf-1/Cip-1) induction of expression. Using a two-hybrid screening, we identified here the transcriptional corepressor CtBP-interacting protein (CtIP) as a SIAH-1-interacting protein. CtIP has been proposed as a regulator of p21(Waf-1/Cip-1) gene transcription through a protein complex involving BRCA1. We demonstrate that SIAH-1 associates with CtIP both in vitro and in vivo. This interaction led to CtIP degradation by the ubiquitin-proteasome pathway. As expected, SIAH-1 induced p21(Waf-1/Cip-1) transcription in Jurkat-T cell. Surprisingly, a SIAH protein deleted of its RING finger, SIAH-1DeltaN, which is able to interact with CtIP but does not promote its degradation, also induced transcription from the p21(Waf-1) promoter in a similar extent as did SIAH-1. Our results suggest that p21(Waf-1/Cip-1) induction by SIAH-1 could not be mediated by CtIP degradation.

Carrier Proteins↗

PubMed2003

Relationship between elevated levels of the alpha 1 acid glycoprotein in chronic myelogenous leukemia in blast crisis and pharmacological resistance to imatinib (Gleevec) in vitro and in vivo.

The Abl tyrosine kinase inhibitor imatinb is becoming a standard for the treatment of chronic myelogenous leukemia (CML). However, Bcr-Abl gene mutations have been reported mainly in relapsing or resistant patients. In primary resistant patients, only few mutations have been documented so far, suggesting alternative mechanisms. We aimed to investigate if alpha 1 acid glycoprotein (AGP), an acute phase drug binding protein, could be a biological marker for pharmacological resistance to imatinib in nine patients in acute phase CML. All patients (3/3) with high AGP dosages (2.31+/-0.17 mg/mL; normal values, 0.5-1.3mg/mL) were primary resistant to imatinib whereas an early clinical response was observed for the six patients with normal AGP levels (1.13+/-0.2mg/mL). No mutation in the adenosine triphosphate domain of Abl were detected before the initiation of imatinib therapy. By using in vitro tests combining various imatinib concentrations (1-10 microM) with purified human AGP (1 and 3 mg/mL), we demonstrate that imatinib-induced apoptosis of K562 or fresh leukemic CML cells is abrogated or reduced. The same effect was observed using sera from donors with high AGP levels (1.9-3.28 mg/mL). In patients with CML in blastic phase, AGP levels could reflect pharmacological resistance to imatinib, suggesting that increased dosage of imatinib or the use of a competitor to drug binding should be recommended to optimize the therapeutic effect of the drug.

Antineoplastic Agents↗

PubMed2003

Regulation of extracellular matrix metalloproteinase inducer and matrix metalloproteinase expression by amphiregulin in transformed human breast epithelial cells.

Amphiregulin (AR) and epidermal growth factor effects on expression and activity of the extracellular matrix metalloproteinase inducer (EMMPRIN) were examined in NS2T2A1 breast tumor cells. Both growth factors induced mRNA and protein expression of EMMPRIN, and matrix metalloproteinase (MMP) -2 and -9 enzymatic activity. The induction of EMMPRIN by AR was mediated by epidermal growth factor receptor (EGFR) tyrosine kinase activation and inhibited by ZD1839. AR and EGFR antisense (AS) cDNAs inhibited EMMPRIN expression and MMP activity. Coculture of NS2T2A1V expressing AR- or EGFR-AS with fibroblasts and endothelial cells showed a decreased MMP activity. In parallel, nude mice tumors derived from AR and EGFR-AS cells revealed reduced level of EMMPRIN and MMP activity. AR and epidermal growth factor, therefore, regulate EMMPRIN and its MMP-mediated expression, identifying EGFR signaling as critical to this regulation.

Amphiregulin↗

PubMed2003

Transforming growth factor beta-1 and amphiregulin act in synergy to increase the production of urokinase-type plasminogen activator in transformed breast epithelial cells.

Amphireguline (AR) is an epidermal growth factor (EGF)-related peptide that seems to play an important role in breast cancer progression. We have demonstrated recently that suppression of AR expression in transformed breast epithelial cells considerably reduced both size and neovascularization of tumors developed in nude mice. We show that the reduction of AR expression allowed to an important decrease of the levels of urokinase-type plasminogen activator (uPA) and transforming growth factor-beta1 (TGFbeta1). According to these data, exogenous AR (10(-10) M-10(-8) M) stimulated the production of uPA and TGFbeta1 in AR antisense-transfected A2-15 and A2-P17F25 cells. The addition of 2 x 10(-10) M TGFbeta1 into culture medium increased the level of uPA produced by AR-expressing parental cells but not by A2-15 and A2-P17F25 cell clones. Whereas AR alone stimulated uPA production to 200% of control, combined AR and TGFbeta1 treatment increased protease level in A2-15 and A2-P17F25 cells to 500-600% of control, demonstrating a synergism between TGFbeta1 and AR. This was accompanied by an important augmentation of the number of tumoral cells that invaded matrigel in vitro. The synergistic induction of uPA protein resulted of an early and transient augmentation of steady state mRNA level and was blocked in the presence of the MAP kinase kinase inhibitor PD098059, strongly suggesting that synergistic effect of AR and TGFbeta1 on uPA expression required MAPK pathway. This data demonstrates concerted action between AR and TGFbeta1 that may have profound effect on protease production and consequently on breast cancer progression.

Amphiregulin↗