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Biomedical subjects

Charles Theillet

Publications and source records attributed to Charles Theillet.

15 recordsLinked to original sources
PubMed2006

Snail and slug play distinct roles during breast carcinoma progression.

PURPOSE: Carcinoma progression is linked to a partially dedifferentiated epithelial cell phenotype. As previously suggested, this regulation could involve transcription factors, Snail and Slug, known to promote epithelial-mesenchymal transitions during development. Here, we investigate the role of Snail and Slug in human breast cancer progression. EXPERIMENTAL DESIGN: We analyzed Snail, Slug, and E-cadherin RNA expression levels and protein localization in large numbers of transformed cell lines and breast carcinomas, examined the correlation with tumor histologic features, and described, at the cellular level, Snail and Slug localization in carcinomas using combined in situ hybridization and immunolocalization. RESULTS: In contrast with transformed cell lines, Slug was found to colocalize with E-cadherin at the cellular level in normal mammary epithelial cells and all tested carcinomas. Snail also colocalized at the cellular level with E-cadherin in tumors expressing high levels of Snail RNA. In addition, Snail was significantly expressed in tumor stroma, varying with tumors. Slug and Snail genes were significantly overexpressed in tumors associated with lymph node metastasis. Finally, the presence of semidifferentiated tubules within ductal carcinomas was linked to Slug expression levels similar to or above normal breast samples. CONCLUSIONS: These results suggest that Snail or Slug expression in carcinoma cells does not generally preclude significant E-cadherin expression. They emphasize a link between Snail, Slug, and lymph node metastasis in a large sampling of mammary carcinomas, and suggest a role for Slug in the maintenance of semidifferentiated structures. Snail and Slug proteins seem to support distinct tumor invasion modes and could provide new therapeutic targets.

Animals↗
PubMed2006

Coactivator-associated arginine methyltransferase 1 (CARM1) is a positive regulator of the Cyclin E1 gene.

The Cyclin E1 gene (CCNE1) is an ideal model to explore the mechanisms that control the transcription of cell cycle-regulated genes whose expression rises transiently before entry into S phase. E2F-dependent regulation of the CCNE1 promoter was shown to correlate with changes in the level of H3-K9 acetylation/methylation of nucleosomal histones positioned at the transcriptional start site region. Here we show that, upon growth stimulation, the same region is subject to variations of H3-R17 and H3-R26 methylation that correlate with the recruitment of coactivator-associated arginine methyltransferase 1 (CARM1) onto the CCNE1 and DHFR promoters. Accordingly, CARM1-deficient cells lack these modifications and present lowered levels and altered kinetics of CCNE1 and DHFR mRNA expression. Consistently, reporter gene assays demonstrate that CARM1 functions as a transcriptional coactivator for their E2F1/DP1-stimulated expression. CARM1 recruitment at the CCNE1 gene requires activator E2Fs and ACTR, a member of the p160 coactivator family that is frequently overexpressed in human breast cancer. Finally, we show that grade-3 breast tumors present coelevated mRNA levels of ACTR and CARM1, along with their transcriptional target CCNE1. All together, our results indicate that CARM1 is an important regulator of the CCNE1 gene.

Activin Receptors, Type I↗
PubMed2006

The clinical value of somatic TP53 gene mutations in 1,794 patients with breast cancer.

To investigate the clinical value of somatic TP53 mutations in breast cancer, we assembled clinical and molecular data on 1,794 women with primary breast cancer with long-term follow-up and whose tumor has been screened for mutation in exons 5 to 8 of TP53 by gene sequencing. TP53 mutations were more frequent in tumors of ductal and medullar types, aggressive phenotype (high grade, large size, node positive cases, and low hormone receptor content) and in women <60 years old. TP53 mutations within exons 5 to 8 conferred an elevated risk of breast cancer-specific death of 2.27 (relative risk >10 years; P < 0.0001) compared with patients with no such mutation. The prognostic value of TP53 mutation was independent of tumor size, node status, and hormone receptor content, confirming and reconciling previous findings in smaller series. Moreover, an interaction between TP53 mutation and progesterone receptor (PR) status was revealed, TP53 mutation combined with the absence of progesterone receptor being associated with the worst prognosis. Whereas previous studies have emphasized the fact that missense mutations in the DNA-binding motifs have a worse prognosis than missense mutations outside these motifs, we show that non-missense mutations have prognostic value similar to missense mutations in DNA-binding motifs. Nonetheless, specific missense mutants (codon 179 and R248W) seem to be associated with an even worse prognosis. These results, obtained on the largest series analyzed thus far, show that TP53 mutations identified by gene sequencing have an independent prognostic value in breast cancer and could have potential uses in clinical practice.

Aged↗
PubMed2005

Comprehensive profiling of 8p11-12 amplification in breast cancer.

In human carcinomas, especially breast cancer, chromosome arm 8p is frequently involved in complex chromosomal rearrangements that combine amplification at 8p11-12, break in the 8p12-21 region, and loss of 8p21-ter. Several studies have identified putative oncogenes in the 8p11-12 amplicon. However, discrepancies and the lack of knowledge on the structure of this amplification lead us to think that the actual identity of the oncogenes is not definitively established. We present here a comprehensive study combining genomic, expression, and chromosome break analyses of the 8p11-12 region in breast cell lines and primary breast tumors. We show the existence of four amplicons at 8p11-12 using array comparative genomic hybridization. Gene expression analysis of 123 samples using DNA microarrays identified 14 genes significantly overexpressed in relation to amplification. Using fluorescence in situ hybridization analysis on tissue microarrays, we show the existence of a cluster of breakpoints spanning a region just telomeric to and associated with the amplification. Finally, we show that 8p11-12 amplification has a pejorative effect on survival in breast cancer.

Breast Neoplasms↗
PubMed2004

Genomic and expression profiling of chromosome 17 in breast cancer reveals complex patterns of alterations and novel candidate genes.

Chromosome 17 is severely rearranged in breast cancer. Whereas the short arm undergoes frequent losses, the long arm harbors complex combinations of gains and losses. In this work we present a comprehensive study of quantitative anomalies at chromosome 17 by genomic array-comparative genomic hybridization and of associated RNA expression changes by cDNA arrays. We built a genomic array covering the entire chromosome at an average density of 1 clone per 0.5 Mb, and patterns of gains and losses were characterized in 30 breast cancer cell lines and 22 primary tumors. Genomic profiles indicated severe rearrangements. Compiling data from all samples, we subdivided chromosome 17 into 13 consensus segments: 4 regions showing mainly losses, 6 regions showing mainly gains, and 3 regions showing either gains or losses. Within these segments, smallest regions of overlap were defined (17 for gains and 16 for losses). Expression profiles were analyzed by means of cDNA arrays comprising 358 known genes at 17q. Comparison of expression changes with quantitative anomalies revealed that about half of the genes were consistently affected by copy number changes. We identified 85 genes overexpressed when gained (39 of which mapped within the smallest regions of overlap), 67 genes underexpressed when lost (32 of which mapped to minimal intervals of losses), and, interestingly, 32 genes showing reduced expression when gained. Candidate genes identified in this study belong to very diverse functional groups, and a number of them are novel candidates.

Breast Neoplasms↗
PubMed2004

Amplification of the BRCA2 pathway gene EMSY in sporadic breast cancer is related to negative outcome.

DNA amplification at band q13 of chromosome 11 is common in breast cancer, and CCND1 and EMS1 remain the strongest candidate genes. However, amplification patterns are consistent with the existence of four cores of amplification, suggesting the involvement of additional genes. Here we present evidence strongly suggesting the involvement of the recently characterized EMSY gene in the formation of the telomeric amplicon. EMSY maps at 11q13.5, 100 kb centromeric to the GARP gene, which has been mapped within the core of the distal amplicon. The EMSY protein was shown to interact with BRCA2 and has a role in chromatin remodeling. This makes EMSY a strong candidate oncogene for the 11q13.5 amplicon. DNA amplification was studied in a total of 940 primary breast tumors and 39 breast cancer cell lines. Amplification profiles were consistent with the EMSY-GARP locus being amplified independently of CCND1 and/or EMS1. EMSY RNA expression levels were studied along with those of five other genes located at 11q13.5 by real-time quantitative PCR in the 39 cell lines and a subset of 65 tumors. EMSY overexpression correlated strongly with DNA amplification in both primary tumors and cell lines. In a subset of 296 patients, EMSY amplification was found by both uni- and multivariate analyses to correlate with shortened disease-free survival. These data indicate that EMSY is a strong candidate oncogene for the 11q13.5 amplicon.

BRCA2 Protein↗
PubMed2003

EMSY links the BRCA2 pathway to sporadic breast and ovarian cancer.

The BRCA2 gene is mutated in familial breast and ovarian cancer, and its product is implicated in DNA repair and transcriptional regulation. Here we identify a protein, EMSY, which binds BRCA2 within a region (exon 3) deleted in cancer. EMSY is capable of silencing the activation potential of BRCA2 exon 3, associates with chromatin regulators HP1beta and BS69, and localizes to sites of repair following DNA damage. EMSY maps to chromosome 11q13.5, a region known to be involved in breast and ovarian cancer. We show that the EMSY gene is amplified almost exclusively in sporadic breast cancer (13%) and higher-grade ovarian cancer (17%). In addition, EMSY amplification is associated with worse survival, particularly in node-negative breast cancer, suggesting that it may be of prognostic value. The remarkable clinical overlap between sporadic EMSY amplification and familial BRCA2 deletion implicates a BRCA2 pathway in sporadic breast and ovarian cancer.

BRCA2 Protein↗
PubMed2003

Genetic variability in MCF-7 sublines: evidence of rapid genomic and RNA expression profile modifications.

BACKGROUND: Both phenotypic and cytogenetic variability have been reported for clones of breast carcinoma cell lines but have not been comprehensively studied. Despite this, cell lines such as MCF-7 cells are extensively used as model systems. METHODS: In this work we documented, using CGH and RNA expression profiles, the genetic variability at the genomic and RNA expression levels of MCF-7 cells of different origins. Eight MCF-7 sublines collected from different sources were studied as well as 3 subclones isolated from one of the sublines by limit dilution. RESULTS: MCF-7 sublines showed important differences in copy number alteration (CNA) profiles. Overall numbers of events ranged from 28 to 41. Involved chromosomal regions varied greatly from a subline to another. A total of 62 chromosomal regions were affected by either gains or losses in the 11 sublines studied. We performed a phylogenetic analysis of CGH profiles using maximum parsimony in order to reconstruct the putative filiation of the 11 MCF-7 sublines. The phylogenetic tree obtained showed that the MCF-7 clade was characterized by a restricted set of 8 CNAs and that the most divergent subline occupied the position closest to the common ancestor. Expression profiles of 8 MCF-7 sublines were analyzed along with those of 19 unrelated breast cancer cell lines using home made cDNA arrays comprising 720 genes. Hierarchical clustering analysis of the expression data showed that 7/8 MCF-7 sublines were grouped forming a cluster while the remaining subline clustered with unrelated breast cancer cell lines. These data thus showed that MCF-7 sublines differed at both the genomic and phenotypic levels. CONCLUSIONS: The analysis of CGH profiles of the parent subline and its three subclones supported the heteroclonal nature of MCF-7 cells. This strongly suggested that the genetic plasticity of MCF-7 cells was related to their intrinsic capacity to generate clonal heterogeneity. We propose that MCF-7, and possibly the breast tumor it was derived from, evolved in a node like pattern, rather than according to a linear progression model. Due to their capacity to undergo rapid genetic changes MCF-7 cells could represent an interesting model for genetic evolution of breast tumors.

Breast Neoplasms↗
PubMed2003

A recurrent chromosome translocation breakpoint in breast and pancreatic cancer cell lines targets the neuregulin/NRG1 gene.

The 8p11-21 region is a frequent target of alterations in breast cancer and other carcinomas. We surveyed 34 breast tumor cell lines and 9 pancreatic cancer cell lines for alterations of this region by use of multicolor fluorescence in situ hybridization (M-FISH) and BAC-specific FISH. We describe a recurrent chromosome translocation breakpoint that targets the NRG1 gene on 8p12. NRG1 encodes growth factors of the neuregulin/heregulin-1 family that are ligands for tyrosine kinase receptors of the ERBB family. Breakpoints within the NRG1 gene were found in four of the breast tumor cell lines: ZR-75-1, in a dic(8;11); HCC1937, in a t(8;10)(p12;p12.1); SUM-52, in an hsr(8)(p12); UACC-812, in a t(3;8); and in two of the pancreatic cancer cell lines: PaTu I, in a der(8)t(4;8); and SUIT-2, in a del(8)(p). Mapping by two-color FISH showed that the breaks were scattered over 1.1 Mb within the NRG1 gene. It is already known that the MDA-MB-175 breast tumor cell line has a dic(8;11), with a breakpoint in NRG1 that fuses NRG1 to the DOC4 gene on 11q13. Thus, we have found a total of seven breakpoints, in two types of cancer cell lines, that target the NRG1 gene. This suggests that the NRG1 locus is a recurring target of translocations in carcinomas. PCR analysis of reverse-transcribed cell line RNAs revealed an extensive complexity of the NRG1 transcripts but failed to detect a consistent pattern of mRNA isoforms in the cell lines with NRG1 breakpoint.

Breast Neoplasms↗
PubMed2002

MYEOV: a candidate gene for DNA amplification events occurring centromeric to CCND1 in breast cancer.

Rearrangements of chromosome 11q13 are frequently observed in human cancer. The 11q13 region harbors several chromosomal breakpoint clusters found in hematologic malignancies and exhibits frequent DNA amplification in carcinomas. DNA amplification patterns in breast tumors are consistent with the existence of at least 4 individual amplification units, suggesting the activation of more than 1 gene in this region. Two candidate oncogenes have been identified, CCND1 and EMS1/CORTACTIN, representing centrally localized amplification units. Genes involved in the proximal and distal amplicons remain to be identified. Recently we reported on a putative transforming gene, MYEOV, mapping 360 kb centromeric to CCND1. This gene was found to be rearranged and activated concomitantly with CCND1 in a subset of t(11;14)(q13;q32)-positive multiple myeloma (MM) cell lines. To evaluate the role of the MYEOV gene in the proximal amplification core, we tested 946 breast tumors for copy number increase of MYEOV relative to neighboring genes or markers. RNA expression levels were studied in a subset of 72 tumors for which both RNA and DNA were available. Data presented here show that the MYEOV gene is amplified in 9.5% (90/946) and abnormally expressed in 16.6% (12/72) of breast tumors. Amplification patterns showed that MYEOV was most frequently coamplified with CCND1 (74/90), although independent amplification of MYEOV could also be detected (16/90). Abnormal expression levels correlated only partially with DNA amplification. MYEOV DNA amplification correlated with estrogen and progesterone receptor-positive cancer, invasive lobular carcinoma type and axillary nodal involvement. In contrast to CCND1 amplification, no association with disease outcome could be found. Our data suggest that MYEOV is a candidate oncogene activated in the amplification core located proximal to CCND1.

Breast Neoplasms↗
PubMed2002

Concordance of allelic imbalance profiles in synchronous and metachronous bilateral breast carcinomas.

Bilateral breast cancer (biBC) is a common form of breast cancer; however, it has not been subjected to systematic comparative genetic studies. We allelotyped 28 biBCs on 14 chromosomal arms, addressing 2 lines of questions: (i) does comparison of genetic profiles disclose contralateral metastases misdiagnosed as second primaries? and (ii) do shared environmental and host factors drive the development of true biBC along similar genetic routes? Allelotyping provided unambiguous proof for distinct clonality in 23 of 28 cases. In another 4 biBCs, the genotyping data did not exclude the hypothesis of metastatic spread, whereas clinical and histologic data were in favor of bilaterality. Thus the question of clonality remained open only for 1 case, in which the paired tumors shared both histologic features and allelotypes. We conclude that the vast majority if not all biBCs are of independent clonal origin. Next, we assessed the similarity of genetic pathways in distinct categories of biBC. It was assumed that the coexistence of allelic imbalance (AI) in 1 tumor and retention of heterozygosity (N) in the contralateral neoplasm corresponds to the distinct genetic profiles, whereas the remaining combinations (AI/AI or N/N) suggest a match of allelic status for a given polymorphic marker. When these allelic matches were pooled, it turned out that synchronous biBC displayed a significantly higher similarity score than metachronous biBC (64/77 [83%] vs. 162/267 [61%]; p = 0.0003). In addition, an increased similarity of allelic profiles was observed in the premenopausal biBC (76/101 [75%]) compared with postmenopausal cases (111/173 [64%]) or tumor pairs separated by the onset of menopause (39/70 [56%]; p = 0.014). Overall, our data suggest that sharing natural histories of the disease, which is more evident in synchronous and/or premenopausal forms of biBC, may result in a similarity of molecular portraits in bilateral breast tumors.

Allelic Imbalance↗
PubMed2002

Reciprocal translocations in breast tumor cell lines: cloning of a t(3;20) that targets the FHIT gene.

All molecular alterations that lead to breast cancer are not precisely known. We are evaluating the frequency and consequences of reciprocal translocations in breast cancer. We surveyed 15 mammary cell lines by multicolor fluorescence in situ hybridization (M-FISH). We identified nine apparently reciprocal translocations. Using mBanding FISH and FISH with selected YAC clones, we identified the breakpoints for four of them, and cloned the t(3;20)(p14;p11) found in the BrCa-MZ-02 cell line. We found that the breakpoint targets the potential tumor-suppressor gene FHIT (fragile histidine triad) in the FRA3B region; it is accompanied by homozygous deletion of exon 5 of the gene and absence of functional FHIT and fusion transcripts, which leads to the loss of FHIT protein expression. Additional experiments using comparative genomic hybridization provided further information on the genomic context in which the t(3;20)(p14;p11) reciprocal translocation was found.

Acid Anhydride Hydrolases↗
PubMed2002

Involvement of ATM missense variants and mutations in a series of unselected breast cancer cases.

It has been proposed that women carrying heterozygous mutations of the ATM gene could be at increased risk of developing breast cancer. However, data in the literature are contrasting and no firm conclusion has been reached. Our aim was to verify whether ATM inactivation could play a role in breast tumor development. Following the classical tumor suppressor inactivation scheme, tumors showing loss of heterozygosity (LOH) at the ATM locus should present an increased proportion of mutated ATM forms. We screened a cohort of 173 nonselected primary breast tumors for LOH in a 4 cM region at 11q23 spanning the ATM gene. We analyzed 25 tumors presenting LOH within the ATM locus for mutations in the ATM coding sequence using an RT-PCR-SSCP approach. Five patients were found to bear a coding missense variant, out of which four corresponded to a frequent polymorphism in exon 39. One patient presented a previously unreported variant in exon 19 (2614C>T) resulting in a nonconservative change (Pro>Ser) at aa 872. This variant was not found in any of the other 172 patients nor in 63 healthy controls tested, indicating that it is a rare ATM variant. LOH involved the ATM wild-type allele in the tumor presenting variant 2614. However, because the ATM gene presents a relatively large number of rare coding polymorphism it is difficult, in the absence of familial data, to be conclusive on the significance of this variant. Searching for further variants in exons 19 and 39 in the whole set of 173 breast tumors, we found one tumor showing an acquired deletion of four bases in the ATM gene. Somatic mutations affecting the ATM gene thus seem rare in breast cancer. In our cohort of breast cancer patients, tumors presenting LOH at the ATM locus did not show an increased frequency of sequence variants. Furthermore, allelic imbalance profiles in a 4-cM region of chromosome arm 11q spanning the ATM locus revealed that hot spots of LOH were more likely to correspond to a region localized telomeric to the gene. Therefore, these data suggest that other target genes for genetic inactivation exist in the 11q23 region.

Alleles↗