Biomedical subjects

Cathy Staedel

Publications and source records attributed to Cathy Staedel.

9 recordsLinked to original sources

PubMed2006

Cell surface overexpression of alphavbeta5 integrin impedes alphavbeta3-mediated migration of the human ovarian adenocarcinoma cell line IGROV1.

Human ovarian surface epithelium and epithelial tumors express integrin alphavbeta5, which can interact with vitronectin. In addition, in vitro acquisition of cisplatin resistance by alphavbeta3-expressing IGROV1 cells is accompanied by cell-surface expression of integrin alphavbeta5. To further explore the role of alphavbeta5 in ovarian carcinoma cells, IGROV1 cells were stably transfected with a human beta5 integrin cDNA construct, and three beta5 transfectant clones were selected for the expression of alphavbeta5 integrin at their cell surface. Despite a delayed entry in the exponential phase of growth, beta5-transfectant cells kept a proliferation ability similar to that of parental cells, while their growth rate was hindered in the presence of an anti-alphavbeta5 blocking antibody. Only simultaneous blockade of alphavbeta3 and alphavbeta5 by specific antibodies impeded the adhesion to vitronectin of beta5 transfectants and of the beta5-expressing cisplatin-resistant variant IGROV1-R10, suggesting that the two heterodimers cooperated in the regulation of this process. Cell surface expression of alphavbeta5 resulted in an attenuation of alphavbeta3-mediated migration on vitronectin. Alphavbeta5 participated to migration events in the absence of exogenous growth factors only in one transfectant clone and in IGROV1-R10 cells. Finally, the response to cisplatin was not significantly modified in beta5 transfectants when compared to IGROV1 parental cells.

Adenocarcinoma↗

PubMed2004

The cyclin-dependent kinase inhibitor p21(cip1/waf1) enhances the cytotoxicity of ganciclovir in HSV-tk transfected ovarian carcinoma cells.

Suicide gene therapy could be an attractive addition to the treatment of ovarian carcinomas, for which acquired chemoresistance frequently results in treatment failure. Here we show that transfection of the HSV-tk gene, followed by incubation with up to 1 mM ganciclovir fails to induce cell death in SKOV3 chemoresistant human ovarian carcinoma cells. However, co-transfection of HSV-tk with Cip1/Waf1 encoding the p21(cip1/waf1) inhibitor of cdks, allows 100 microM ganciclovir to eradicate the population of tumor cells. Potentiation of a drug by co-transfer of HSV-tk with Cip1/Waf1could thus represent another therapeutic approach for tumours that are resistant to conventional therapy.

Adenocarcinoma↗

PubMed2003

alpha(v) integrins regulate cell proliferation through integrin-linked kinase (ILK) in ovarian cancer cells.

Integrins regulate both adhesion and signaling processes involved in proliferation and survival. alpha(v)beta(3) and alpha(v)beta(5) integrins have been shown to mediate cell adhesion and migration. Here we used human ovarian cancer cell lines (IGROV1, SKOV-3) that express alpha(v)beta(3) and alpha(v)beta(5) to study their role in cell proliferation and the signaling pathways involved. We found that alpha(v) integrins regulate cell proliferation through activation of integrin-linked kinase (ILK). An anti-alpha(v)-blocking antibody specifically inhibits the growth of IGROV1 and SKOV-3. The inhibition of cell proliferation involves alpha(v)beta(3) in IGROV1 cells, and both alpha(v)beta(3) and alpha(v)beta(5) in SKOV-3 cells. The reduced growth rate induced by alpha(v) integrin blockade is linked in both cell lines to G1/S cell cycle arrest. alpha(v) integrin blockade by neutralizing antibody as well as cyclic-RGD peptide caused an inhibition of ILK activity and phosphorylation of PKB/Akt on serine-473 but not on threonine-308, and was accompanied by an increase in p27(Kip1) expression. Overexpression of wild-type ILK rescued the phosphorylation of PKB/Akt on serine-473 in cells treated with anti-alpha(v) antibody. Inhibition of ILK by a pharmacological inhibitor results in inhibition of cell proliferation, PKB/Akt phosphorylation and increase of p27(Kip1). These results demonstrate that alpha(v) integrins regulate ovarian cancer cell proliferation through ILK.

Adenocarcinoma↗

PubMed2003

A promoter activity is present in the DNA sequence corresponding to the hepatitis C virus 5' UTR.

The hepatitis C virus (HCV) 5' untranslated region (UTR) has been extensively studied with regard to its internal ribosomal entry site (IRES) activity. In this work we present results suggesting the existence of a strong promoter activity carried by the DNA sequence corresponding to the HCV 5' UTR. This activity was not detected when the HCV 5' UTR sequence was replaced by HCV 3' UTR or poliovirus 5' UTR sequences. These results were further confirmed by using bicistronic constructions. We demonstrated the presence of an mRNA initiated in this 5' UTR sequence and located the initiation site by the 5' RACE method at nucleotide 67. Furthermore, northern experiments and flow cytometry analysis showed the unambiguous activity of such a promoter sequence in stably transfected cells. Our results strongly suggest that the data obtained using bicistronic DNA constructs carrying the HCV 5' UTR should be analyzed not only at the translational but also at the transcriptional level.

5' Untranslated Regions↗

PubMed2003

Antisense oligonucleotides targeted to the domain IIId of the hepatitis C virus IRES compete with 40S ribosomal subunit binding and prevent in vitro translation.

Initiation of protein synthesis on the hepatitis C virus (HCV) mRNA involves a structured element corresponding to the 5' untranslated region and constituting an internal ribosome entry site (IRES). The domain IIId of the HCV IRES, an imperfect RNA hairpin extending from nucleotides 253 to 279 of the viral mRNA, has been shown to be essential for translation and for the binding of the 40S ribosomal subunit. We investigated the properties of a series of antisense 2'-O-methyloligoribonucleotides targeted to various portions of the domain IIId. Several oligomers, 14-17 nt in length, selectively inhibited in vitro translation of a bicistronic RNA construct in rabbit reticulocyte lysate with IC(50)s <10 nM. The effect was restricted to the second cistron (the Renilla luciferase) located downstream of the HCV IRES; no effect was observed on the expression of the first cistron (the firefly luciferase) which was translated in a cap-dependent manner. Moreover, antisense 2'-O-methyloligoribonucleotides specifically competed with the 40S ribosomal subunit for binding to the IRES RNA in a filter- retention assay. The antisense efficiency of the oligonucleotides was nicely correlated to their affinity for the IIId subdomain and to their ability to displace 40S ribosomal subunit, making this process a likely explanation for in vitro inhibition of HCV-IRES-dependent translation.

Base Sequence↗

PubMed2002

Resistance of colon cancer cells to long-term 5-fluorouracil exposure is correlated to the relative level of Bcl-2 and Bcl-X(L) in addition to Bax and p53 status.

Defects in apoptosis have been implicated in chemoresistance of colon cancer cells. We report here the ability to resist to 5-fluorouracil-induced apoptosis of 8 colon cancer cell lines differing in p53 and bax status: p53(-/0)bax(+/+) for TC7, SW480, HT-29; p53(+/+)bax(-/-) for LS174T, LoVo; p53(+/+) bax(+/-) for HCT116; p53(+/+) or p53(+/0)bax(+/+) for LS513 or HCT-EB, respectively. To approximate to the in vivo therapy, the cell lines were exposed to a long-term treatment of 5-FU. The analysis of proteins implicated in the apoptotic pathway has shown that the independent analysis of p53 or bax status was not sufficient to predict the extent of drug-resistance of all cell lines. In p53(+/+) cell lines but not in p53(-/0) cell lines, a low level of the pro-apoptotic Bax protein was correlated with a greater resistance of cells to 5-FU. In addition, we found that high levels of anti-apoptotic Bcl-2 and Bcl-x(L) proteins combined with a low level of Bax were correlated to high 5-FU resistance of wild-type p53 cell lines. The same correlation was obtained for 2 out of 3 mutated p53 cell lines. In conclusion, the relative levels of Bcl-2, Bcl-x(L) and Bax may altogether contribute to determine the resistance of a majority of colon tumor cells to long-term 5-FU treatment, whatever their p53 status.

Antimetabolites, Antineoplastic↗

PubMed2002

Altered adhesion properties and alphav integrin expression in a cisplatin-resistant human ovarian carcinoma cell line.

In order to elucidate the mechanisms underlying the development of chemoresistance in ovarian cancer, we have previously established the IGROV1-R10 cisplatin-resistant cell line by mimicking a clinical protocol of drug administration on IGROV1 human ovarian carcinoma cells. Both IGROV1 and IGROV1-R10 cells were able to grow as a monolayer and to release cell clusters into the medium. However, IGROV1-R10 cells exhibited an enhanced capacity to detach from the monolayer as compared to the parental cells. When substrate adhesion was prevented, IGROV1-R10 cells were able to survive and to proliferate as cell clusters, even at a low cell density, whereas IGROV1 cells massively died. To explore the underlying mechanisms, we have been interested in alphav integrins, which have been implicated in some aspects of ovarian cancer biology. Both IGROV1 and IGROV1-R10 adherent cells expressed alphavbeta3 integrin. During cell growth, alphavbeta5 integrin accumulated at the surface of a majority of IGROV1-R10 cells from the monolayer, whereas only a faint expression of this integrin was observed in a minority of IGROV1 cells. The growth of IGROV1-R10 cells, but not of IGROV1 cells, was partly inhibited by a specific alphavbeta5-blocking antibody suggesting that alphavbeta5 integrin contributed to IGROV1-R10 cell proliferation.

Adenocarcinoma↗

PubMed2002

[Integrins, cell response to anti-tumor agents and chemoresistance].

Integrins are a family of heterodimeric transmembrane receptors that mediate cell-cell and cell-extracellular matrix adhesion. Integrin-mediated signaling is essential for the regulation of fundamental cellular functions, including proliferation and survival, and for tumor development. According to in vitro studies, integrin ligation by extracellular matrix proteins can modulate the cytotoxicity of anti-tumor agents, in a cell-type sensitive manner. Underlying molecular mechanisms are not well understood, but may be based on the interrelations between integrin signaling pathways and pathways that control cell cycle and apoptosis. On the other hand, alterations of integrin expression and/or function have been observed during the acquisition of chemoresistance in cells chronically exposed to cytotoxic agents. These data are in favor of a role of integrins in chemoresistance processes, and open new perspectives in the field of cancer therapy and prognosis.

Antineoplastic Agents↗

PubMedDate not supplied

Modulating viral gene expression by aptamers to RNA structures.

Oligonucleotides exhibiting a strong affinity and a high specificity for RNA hairpins were obtained by in vitro selection. Such oligomers give rise to loop-loop complexes with the target hairpins: the trans-activation responsive (TAR) element of the Human Immunodeficiency virus-1 (HIV-1) or subdomains of the Hepatitis C virus (HCV) mRNA. Chemically modified derivatives of an antiTAR aptamer were shown to compete out the binding of the viral protein Tat and to selectively inhibit the in vitro TAR-dependent transcription of a reporter gene. In addition, antisense oligomers derived from sequences selected against the domain IIId of the HCV internal ribosome entry site were shown to specifically block translation both in a cell-free assay and in cultured cells.

Animals↗