Biomedical subjects

Sylvie Chevillard

Publications and source records attributed to Sylvie Chevillard.

11 recordsLinked to original sources

PubMed2006

Transcriptional response of wild-type and ataxia telangiectasia lymphoblasts following exposure to equitoxic doses of ionizing radiation.

Experiments were designed to compare the transcriptional response to ionizing radiation (IR) of wild-type (WT) and ataxia telangiectasia (AT) cells. mRNA levels were assessed 2, 4 and 24 h after exposure to equitoxic doses using cDNA microarrays. Data reveal distinct patterns of gene expression between AT and WT cells since IR-responsive genes were mostly cell-type specific, this group representing 87 and 94% of the responding genes in WT and AT cells, respectively. In both cell lines, transcriptional alterations of genes associated with proliferation correlated with the observed cell cycle and growth data. Deregulated genes involved in apoptosis suggest that wild-type cells were more prone to cell death by apoptosis than AT cells. Furthermore, genes associated with the response to oxidative stress were particularly deregulated in wild-type cells whereas alterations of genes related to unexpected pathways including RNA processing, protein synthesis and lipid metabolism were specifically found in irradiated AT cells. These data suggest that under radiation conditions leading to a similar survival of WT and AT cells, the mechanisms triggered after radiation were mainly dependent on ATM status and thus on the intrinsic radiosensitivity.

Ataxia Telangiectasia↗

PubMed2006

Redox regulation of human OGG1 activity in response to cellular oxidative stress.

8-Oxoguanine (8-oxoG), a common and mutagenic form of oxidized guanine in DNA, is eliminated mainly through base excision repair. In human cells its repair is initiated by human OGG1 (hOGG1), an 8-oxoG DNA glycosylase. We investigated the effects of an acute cadmium exposure of human lymphoblastoid cells on the activity of hOGG1. We show that coinciding with alteration of the redox cellular status, the 8-oxoG DNA glycosylase activity of hOGG1 was nearly completely inhibited. However, the hOGG1 activity returned to normal levels once the redox cellular status was normalized. In vitro, the activity of purified hOGG1 was abolished by cadmium and could not be recovered by EDTA. In cells, however, the reversible inactivation of OGG1 activity by cadmium was strictly associated with reversible oxidation of the protein. Moreover, the 8-oxoG DNA glycosylase activity of purified OGG1 and that from crude extracts were modulated by cysteine-modifying agents. Oxidation of OGG1 by the thiol oxidant diamide led to inhibition of the activity and a protein migration pattern similar to that seen in cadmium-treated cells. These results suggest that cadmium inhibits hOGG1 activity mainly by indirect oxidation of critical cysteine residues and that excretion of the metal from the cells leads to normalization of the redox cell status and restoration of an active hOGG1. The results presented here unveil a novel redox-dependent mechanism for the regulation of OGG1 activity.

Cadmium↗

PubMed2006

Specific TP53 mutation pattern in radiation-induced sarcomas.

The mutagenic properties of ionizing radiation are well known, but the presence of specific mutations in human radiation-induced tumours is not established. We have studied a series of 36 secondary sarcomas arising in the irradiation field of a primary tumour following radiotherapy. The allelic status and the presence of mutations of the TP53 gene were investigated. The mutation pattern was compared with data from sporadic sarcomas recorded in the IARC TP53 somatic mutations database. A high proportion (58%) of the radiation-induced sarcomas exhibited a somatic inactivating mutation for one allele of TP53, systematically associated with a loss of the other allele. The high frequency (52%) of short deletions observed in the mutation pattern of radiation-induced sarcomas may be related to the induction of DNA breaks by ionizing radiation. The lack of hyper-reactivity of CpG dinucleotides and the presence of recurrent sites of mutation at codons 135 and 237 seem also to be specific for radiation tumorigenesis.

Adult↗

PubMed2005

Non-homologous end-joining genes are not inactivated in human radiation-induced sarcomas with genomic instability.

DNA double-strand break (DSB) repair pathways are implicated in the maintenance of genomic stability. However the alterations of these pathways, as may occur in human tumor cells with strong genomic instability, remain poorly characterized. We analyzed the loss of heterozygosity (LOH) and the presence of mutations for a series of genes implicated in DSB repair by non-homologous end-joining in five radiation-induced sarcomas devoid of both active Tp53 and Rb1. LOH was recurrently observed for 8 of the 9 studied genes (KU70, KU80, XRCC4, LIG4, Artemis, MRE11, RAD50, NBS1) but not for DNA-PKcs. No mutation was found in the remaining allele of the genes with LOH and the mRNA expression did not correlate with the allelic status. Our findings suggest that non-homologous end-joining repair pathway alteration is unlikely to be involved in the high genomic instability observed in these tumors.

DNA Damage↗

PubMed2004

Gene expression profiling of differentiated thyroid neoplasms: diagnostic and clinical implications.

PURPOSE: The purpose of this research was to identify novel genes that can be targeted as diagnostic and clinical markers of differentiated thyroid tumors. EXPERIMENTAL DESIGN: Gene expression analysis using microarray platform was performed on 6 pathologically normal thyroid samples and 12 primary follicular and papillary thyroid neoplasms. Microarrays containing probes for 5,760 human full-length cDNAs were used for hybridization with total RNA from normal and tumor thyroid samples labeled with Cy3-dUTP and Cy5-dUTP, respectively. Scanned array images were recorded, and data analysis was performed. Selected sets of differentially expressed genes were analyzed using quantitative real-time reverse transcription-PCR for verification. RESULTS: We identified 155 genes that differentiate histologically normal thyroid tissues from benign and malignant thyroid neoplasms. Of these 75 genes were differentiated between follicular neoplasms (adenoma and carcinoma) and the follicular variant of papillary carcinoma. Purely follicular neoplasms (adenomas and carcinomas) shared many genetic profiles, and only 43 genes were distinctly different between these tumors. Hierarchical cluster analysis also differentiated conventional papillary carcinoma from its follicular variant and follicular tumors. The differentially expressed genes were composed of members of cell differentiation, adhesion, immune response, and proliferation associated pathways. Quantitative real-time reverse transcription-PCR analysis of selected genes corroborated the microarray expression results. CONCLUSIONS: Our study show the following: (1) differences in gene expression between tumor and nontumor bearing normal thyroid tissue can be identified, (2) a set of genes differentiate follicular neoplasm from follicular variant of papillary carcinoma, (3) follicular adenoma and carcinoma share many of the differentiated genes, and (4) gene expression differences identify conventional papillary carcinoma from the follicular variant.

Adenocarcinoma, Follicular↗

PubMed2004

Progesterone prevents radiation-induced apoptosis in breast cancer cells.

Sex steroid hormones play an essential role in the control of homeostasis in the mammary gland. Although the involvement of progesterone in cellular proliferation and differentiation is well established, its exact role in the control of cell death still remains unclear. As dysregulation of the apoptotic process plays an important role in the pathogenesis of breast cancer, we investigated the regulation of apoptosis by progesterone in various breast cancer cell lines. Our results show that progesterone treatment protects against radiation-induced apoptosis. This prevention appears to be mediated by the progesterone receptor and is unrelated to p53 status. There is also no correlation with the intrinsic hormonal effect on cell proliferation, as the presence of cells in a particular phase of the cell cycle. Surprisingly, progesterone partly allows bypassing of the irradiation-induced growth arrest in G(2)/M in PgR+ cells, leading to an increase in cell proliferation after irradiation. One consequence of this effect is a higher rate of chromosome damage in these proliferating progesterone-treated cells compared to what is observed in untreated irradiated cells. We propose that progesterone, by inhibiting apoptosis and promoting the proliferation of cells with DNA damage, potentially facilitates the emergence of genetic mutations that may play a role in malignant transformation.

Apoptosis↗

PubMed2003

In vitro aging of rat lung cells. Downregulation of telomerase activity and continuous decrease of telomere length are not incompatible with malignant transformation.

Most normal mammalian somatic cells cultivated in vitro enter replicative senescence after a finite number of divisions, as a consequence of the progressive shortening of telomeres during proliferation that reflects one aspect of organism/cellular aging. The situation appears more complex in rodent cells due to physiological telomerase expression in most somatic normal tissues, great telomere length, and the difficulties of finding suitable in vitro culture conditions. To study in vitro aging of rat lung epithelial cells, we have developed primary culture conditions adapted to rat fresh lung explants and have studied for 1 year (50 passages) the changes in cellular proliferation and mortality, genetic instability, telomerase activity, telomere length, and tumorigenic potential. We have observed an absence of senescence and/or crisis, a transient genetic instability, the persistence of a differentiated Clara cell phenotype, a steady decrease in telomerase activity followed by a low residual activity together with a continuous decrease in telomere length, a constant rate of proliferation, and the acquisition of tumorigenic potential. The bypass of the growth arrest and the acquisition of long-term growth properties could be explained by the loss of p16(INK4a) expression, the ARF/p53 pathway not being altered. In conclusion, these results clearly indicate that, in rat lung epithelial cells, in vitro transformation and acquisition of tumorigenic properties can occur even if the telomere length is still decreasing and telomerase activity remains downregulated.

Animals↗

PubMed2003

Global genome repair is required to activate KIN17, a UVC-responsive gene involved in DNA replication.

UV light provokes DNA lesions that interfere with replication and transcription. These lesions may compromise cell viability and usually are removed by nucleotide excision repair (NER). In humans, inactivation of NER is associated with three rare autosomal recessive inherited disorders: xeroderma pigmentosum (XP), Cockayne syndrome, and trichothiodystrophy. The NER earliest step is lesion recognition by a complex formed by XPC and HHR23B proteins. In a subsequent step, XPA protein becomes associated to the repair complex. Here we investigate whether XPA and XPC proteins, involved in global genome repair, may contribute to a signal transduction pathway regulating the response to UVC-induced lesions. We monitored the expression of several UVC-induced genes in cells deficient in either a transduction pathway or mutated on an NER gene. Expression of the KIN17 gene is induced after UVC irradiation independently of p53 and of activating transcription factor 2. However, in human cells derived from XPA or XPC patients the UVC-induced accumulation of KIN17 RNA and protein is abolished. Our results indicate that the presence of functional XPA and XPC proteins is essential for the up-regulation of the KIN17 gene after UVC irradiation. They also show that the integrity of global genome repair is required to trigger KIN17 gene expression and probably other UVC-responsive genes.

Activating Transcription Factor 2↗

PubMed2002

Single static view 99mTc-sestamibi scintimammography predicts response to neoadjuvant chemotherapy and is related to MDR expression.

We examined the relevance of a pre-treatment single static view 99mTc-sestamibi scintimammography and expression of multidrug resistance proteins as predictors of response to neoadjuvant chemotherapy for invasive breast cancer. Forty-five patients affected by primary breast cancer underwent clinical examination, mammography, sonography, 99mTc-sestamibi scintimammography, and biopsy for histopathological diagnosis before neoadjuvant chemotherapy. Expression of MDR1 and MRP mRNA were determined by RT-PCR on fine-needle aspirations. Following completion of anthracycline-based chemotherapy, clinical, mammographic, sonographic and pathological responses were determined. 99mTc-sestamibi scintimammography predicted the reduction of tumor size measured by sonography and the pathological response according to Sataloff classification (p<0.05) and tend to predict pathological response according to Chevallier (p<0.1). A negative 99mTc-sestamibi scintimammography predicted chemoresistance with a specificity of 100%. Uptake of 99mTc-sestamibi was inversely correlated to the expression of MDR1 (p<0.05) in invasive ductal carcinoma. A pre-treatment single-view 99mTc-sestamibi scintimammography is an excellent predictor of MDR1 chemoresistance and was highly specific of a lack of pathological response to chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Expression of genes involved in chemoresistance, proliferation and apoptosis in clinical samples of renal cell carcinoma and correlation with clinical outcome.

This study investigated the multidrug resistance, proliferation and apoptosis expression in renal cell carcinomas compared to adjacent normal kidney (ANK) tissues. Multidrug resistance (MDR1), multidrug resistance-associated protein (MRP), glutathione-S-transferase-pi (GST-pi), Topoisomerase-II alpha (TOPO-IIalpha), thymidylate synthase (TS), thymidine kinase (TK), Ki67, BAX and BCL-2 genes were analysed in a series of 30 renal cell carcinomas (RCC) and 16 biopsies from adjacent normal kidney (ANK) tissue using reverse-transcription-PCR (rt-PCR). The mean MDR1 expression was significantly lower in RCC than that of ANK (0.4 +/- 0.2 sd versus 0.75 +/- 0.19, p = 0.0008). The expression of MRP, GST-pi and TOPO-IIalpha was not significantly different in RCC as compared with ANK. The mean TK expression in RCC was significantly higher than in ANK (0.31 +/- 0.15 versus 0.09 +/- 0.08, p = 0.002). The TS and Ki67 expression in RCC was significantly higher than in ANK (87.5%, IC95% 71-100% versus 0%, p = 0.001; 56% IC95% 32-81% versus 0%, p = 0.004, respectively). BAX and BCL-2 expression in RCC was significantly higher than that of ANK (0.51 +/- 0.08 versus 0.18 +/- 0.12, p = 0.0001; 0.73 +/- 0.16 versus 0.5 +/- 0.22, p = 0.01, respectively). No significant correlation was found between MDR1, MRP, GST-pi, TOPO-IIalpha, TS, TK and BAX expression with the grade and the clinical stage in RCC.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Down-regulation of telomerase activity after progesterone treatment of human breast cancer cells: essential role of the cell cycle status.

Steroid hormones have been implicated in the regulation of cellular proliferation and of telomerase activity. Because progestin modulates cell cycle progression in vitro, we investigated if the regulation of telomerase activity by progesterone could be cell cycle-dependent. We found that progesterone treatment of the T47D breast cancer cell line induced both the down-regulation of hTERT (human telomerase reverse transcriptase) mRNA expression and telomerase activity together with a cell cycle blockage characterized by a accumulation of cells in G0/G1-phase. For the first time, after the analysis of cells sorted by flow cytometry, we showed that telomerase activity is lower in the G0/G1-phase than in the S- or G2/M-phase, with or without hormone treatment. These results indicated that the hTERT gene is not a direct target of progesterone; after treatment the down-regulation of telomerase activity is mainly related to the accumulation of cells in the G0/G1-phase of the cell cycle.

Breast Neoplasms↗