Survie cellulaire : différences et différenciation

Les mécanismes de la régulation de la survie cellulaire et de l’apoptose sont d’une nature très complexe, impliquant de nombreux intervenants et de nombreuses voies de signalisation aussi bien dans la prise de décision de survivre (ou de mourir) que dans l’exécution de l’apoptose proprement dite. Il en va de même pour l’anoïkose, une forme d’apoptose régulée principalement par les interactions cellule-matrice extracellulaire médiées par les intégrines. Or, la survie cellulaire, l’apoptose et l’anoïkose comportent des différences mécanistiques supplémentaires dépendant des tissus et des types cellulaires spécifiquement concernés. Incidemment, des études de la survie cellulaire effectuées dans un tissu particulier, l’épithélium intestinal humain, ont mis au jour un degré additionnel de complexité dans la régulation de ces processus : l’activation de mécanismes distincts selon l’état de différenciation cellulaire.The regulatory mechanisms of cell survival and apoptosis are very complex in nature, implicating numerous players and signaling pathways not only in the decision-making process of surviving (or dying), but as well as in the execution of apoptosis itself. The same complex nature applies with regards to anoikis, a form of apoptosis that is largely regulated by integrin-mediated, cell-extracellular matrix interactions. However, cell survival, apoptosis and anoikis also happen to implicate further mechanistic distinctions according to the specific tissue and/or cell type concerned. Incidentally, recent studies in a particular tissue, the human intestinal epithelium, have unearthed yet another layer of complexity in the regulation of these three cellular processes, namely the implication of differentiation state-specific mechanisms. Although our understanding of the molecular underpinnings of this new concept of differentiation state-distinct regulation of cell survival, apoptosis and/or anoikis is in its infancy, there is already evidence that such principle applies as well to cell types other than intestinal epithelial cells. Further studies on the differentiation state-specific regulation of these three cellular processes, either under normal or physiopathological situations, should prove crucial in increasing our understanding of pathologies which implicate a dysregulation of apoptosis and/or anoikis – such as cancer

Integrin Signaling, Cell Survival, and Anoikis: Distinctions, Differences, and Differentiation

Cell survival and apoptosis implicate an increasing complexity of players and signaling pathways which regulate not only the decision-making process of surviving (or dying), but as well the execution of cell death proper. The same complex nature applies to anoikis, a form of caspase-dependent apoptosis that is largely regulated by integrin-mediated, cell-extracellular matrix interactions. Not surprisingly, the regulation of cell survival, apoptosis, and anoikis furthermore implicates additional mechanistic distinctions according to the specific tissue, cell type, and species. Incidentally, studies in recent years have unearthed yet another layer of complexity in the regulation of these cell processes, namely, the implication of cell differentiation state-specific mechanisms. Further analyses of such differentiation state-distinct mechanisms, either under normal or physiopathological contexts, should increase our understanding of diseases which implicate a deregulation of integrin function, cell survival, and anoikis

Implication de la laminine dans la modulation de la différentiation entérocytaire humaine

L'objectif du présent travail était d'analyser, au niveau cellulaire, l'influence de la laminine et de la mérosine (une forme variante de la laminine) sur la différenciation des cellules de la lignée carcinomateuse de côlon humain Caco-2, un modèle cellulaire reconnu pour son utilité dans l'analyse de la différenciation entérocytaire humaine. Dans un premier temps, nous avons caractérisé la propriété des cellules Caco-2 à exprimer de manière hétérogène les hydrolases intestinales, comme la sucrase-isomaltase (SI). Pour ce faire, nous avons effectué une analyse comparée de la différenciation morphologique (polarisation, développement de la bordure en brosse) et fonctionnelle (expression de la SI) au cours du processus graduel de différenciation entérocytaire de ces cellules. Cette analyse a révélé que la différenciation morphologique et fonctionnelle s'effectuent selon un patron hétérogène ("mosaïque") transitoire, chez les cellules Caco-2. De plus, nous avons mis en évidence une absence de corrélation, au niveau cellulaire, entre le degré de développement de la bordure en brosse et l'expression de la SI. Par conséquent, cette propriété des cellules Caco-2 à se différencier morphologiquement et fonctionnellement selon un patron de type mosaïque transitoire représenterait un phénomène global d'expression découplée de gènes, associés à la différenciation entérocytaire. Dans un second volet, nous avons vérifié la capacité des cellules Caco-2 à synthétiser et à déposer les principaux constituants de la lame basale intestinale humaine (en particulier la laminine), tant en mono-culture que sous l'influence de cellules mésenchymateuses ("HIM") dérivées d'intestin humain. Lorsque cultivées seules, les cellules Caco-2 expriment la laminine et la fibronectine. De leur côté, les cellules HIM expriment le collagène de type IV, la laminine, la fibronectine et la ténascine. Dans les co-cultures Caco-2/HIM, une déposition de tous les constituants de la lame basale est observée à l'interface épithélio-mésenchymateuse, incluant le protéoglycan de type héparan sulfate dont l'expression, par les cellules Caco-2, est induite par les cellules HIM. De plus, une redistribution, à la surface membranaire basale, de la sous-famille B1 des intégrines est observée chez les cellules Caco-2, en co-culture. Par conséquent, les cellules Caco-2, malgré leur origine cancéreuse, sont d'une part aptes à une expression in vitro des constituants de la lame basale intestinale lorsqu'en co-culture avec les cellules HIM et, de l'autre, d'interagir de manière fonctionnelle avec ces mêmes constituants. Dans un troisième temps, nous avons analysé la distribution in vivo de la laminine et de la mérosine le long de l'axe crypte-villosité de l'intestin humain. Nous avons observé une localisation préférentielle de la laminine en association avec les cellules épithéliales différenciées des villosités, à l'opposé d'une distribution restreinte de la mérosine au niveau des cellules immatures de la crypte, suggérant ainsi une implication différentielle de ces deux constituants de la lame basale dans la différenciation entérocytaire. Cette hypothèse a été vérifiée, au niveau cellulaire, chez les cellules Caco-2 dans le quatrième et dernier volet. Tout d'abord, l'analyse détaillée de l'expression de la laminine a révélé une déposition cumulative de celle-ci en fonction du processus graduel de différenciation des cellules. De plus, nous avons observé une relation étroite entre l'expression mosaïque transitoire de la SI et une expression hétérogène également transitoire de la chaîne A de la Iaminine. Au niveau cellulaire, nous avons démontré une corrélation directe entre l'expression basale de cette chaîne et celle de la SI à la région apicale. Cependant, la mérosine n'est exprimée à aucun moment par les cellules Caco-2 au cours de leur différenciation. Enfin, la culture des cellules Caco-2 sur la Iaminine ainsi que sur la mérosine a non seulement démontré un effet promoteur direct de la Iaminine dans l'expression des hydrolases intestinales (SI, lactase, aminopeptidase N, phosphatase alcaline), mais cela nous a également permis de mettre en évidence l'aspect modulateur différentiel de ces deux molécules. En effet, nous avons observé que la mérosine influence positivement l'expression de l'aminopeptidase N et de la phosphatase alcaline, mais non pas celle de la SI et de la lactase. Par conséquent, ces observations identifient la Iaminine comme un modulateur prépondérant de la différenciation entérocytaire humaine et supportent le concept d'une implication de la Iaminine et de la mérosine dans une modulation différentielle de ce processus in vivo, le long de l'axe crypte-villosité

Integrin/Fak/Src-mediated regulation of cell survival and anoikis in human intestinal epithelial crypt cells: selective engagement and roles of PI3-K isoform complexes

In human intestinal epithelial crypt (HIEC) cells, the PI3-K/Akt-1 pathway is crucial for the promotion of cell survival and suppression of anoikis. Class I PI3-K consists of a complex formed by a catalytic (C) and regulatory (R) subunit. Three R (p85α, β, and p55γ) and four C (p110α, β, γ and δ) isoforms are known. Herein, we analyzed the expression of PI3-K isoforms in HIEC cells and determined their roles in cell survival, as well as in the β1 integrin/Fak/Src-mediated suppression of anoikis. We report that: (1) the predominant PI3-K complexes expressed by HIEC cells are p110α/p85β and p110α/p55γ; (2) the inhibition and/or siRNA-mediated expression silencing of p110α, but not that of p110β, γ or δ, results in Akt-1 down-activation and consequent apoptosis; (3) the expression silencing of p85β or p55γ, but not that of p85α, likewise induces Akt-1 down-activation and apoptosis; however, the impact of a loss of p55γ on both Akt-1 activation and cell survival is significantly greater than that from the loss of p85β; and (4) both the p110α/p85β and p110α/p55γ complexes are engaged by β1 integrin/Fak/Src signaling; however, the engagement of p110α/p85β is primarily Src-dependent, whereas that of p110α/p55γ is primarily Fak-dependent (but Src-independent). Hence, HIEC cells selectively express PI3-K isoform complexes, translating into distinct roles in Akt-1 activation and cell survival, as well as in a selective engagement by Fak and/or Src within the context of β1 integrin/Fak/Src-mediated suppression of anoikis

Cognitive Information Processing

Contains goals, background, research activities on one research project and reports on three research projects.Center for Advanced Television StudiesAmerican Broadcasting CompanyAmpex CorporationColumbia Broadcasting SystemsHarris CorporationHome Box OfficePublic Broadcasting ServiceNational Broadcasting CompanyRCA CorporationTektronix3M CompanyProvidence Gravure Co. (Grant)International Business Machines, Inc

Polymorphisms in a Putative Enhancer at the 10q21.2 Breast Cancer Risk Locus Regulate NRBF2 Expression.

Genome-wide association studies have identified SNPs near ZNF365 at 10q21.2 that are associated with both breast cancer risk and mammographic density. To identify the most likely causal SNPs, we fine mapped the association signal by genotyping 428 SNPs across the region in 89,050 European and 12,893 Asian case and control subjects from the Breast Cancer Association Consortium. We identified four independent sets of correlated, highly trait-associated variants (iCHAVs), three of which were located within ZNF365. The most strongly risk-associated SNP, rs10995201 in iCHAV1, showed clear evidence of association with both estrogen receptor (ER)-positive (OR = 0.85 [0.82-0.88]) and ER-negative (OR = 0.87 [0.82-0.91]) disease, and was also the SNP most strongly associated with percent mammographic density. iCHAV2 (lead SNP, chr10: 64,258,684:D) and iCHAV3 (lead SNP, rs7922449) were also associated with ER-positive (OR = 0.93 [0.91-0.95] and OR = 1.06 [1.03-1.09]) and ER-negative (OR = 0.95 [0.91-0.98] and OR = 1.08 [1.04-1.13]) disease. There was weaker evidence for iCHAV4, located 5' of ADO, associated only with ER-positive breast cancer (OR = 0.93 [0.90-0.96]). We found 12, 17, 18, and 2 candidate causal SNPs for breast cancer in iCHAVs 1-4, respectively. Chromosome conformation capture analysis showed that iCHAV2 interacts with the ZNF365 and NRBF2 (more than 600 kb away) promoters in normal and cancerous breast epithelial cells. Luciferase assays did not identify SNPs that affect transactivation of ZNF365, but identified a protective haplotype in iCHAV2, associated with silencing of the NRBF2 promoter, implicating this gene in the etiology of breast cancer.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.ajhg.2015.05.002

A case-only study to identify genetic modifiers of breast cancer risk for BRCA1/BRCA2 mutation carriers

Breast cancer (BC) risk for BRCA1 and BRCA2 mutation carriers varies by genetic and familial factors. About 50 common variants have been shown to modify BC risk for mutation carriers. All but three, were identified in general population studies. Other mutation carrier-specific susceptibility variants may exist but studies of mutation carriers have so far been underpowered. We conduct a novel case-only genome-wide association study comparing genotype frequencies between 60,212 general population BC cases and 13,007 cases with BRCA1 or BRCA2 mutations. We identify robust novel associations for 2 variants with BC for BRCA1 and 3 for BRCA2 mutation carriers, P < 10−8, at 5 loci, which are not associated with risk in the general population. They include rs60882887 at 11p11.2 where MADD, SP11 and EIF1, genes previously implicated in BC biology, are predicted as potential targets. These findings will contribute towards customising BC polygenic risk scores for BRCA1 and BRCA2 mutation carriers

Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus

A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 × 10-20), ER-negative BC (P=1.1 × 10-13), BRCA1-associated BC (P=7.7 × 10-16) and triple negative BC (P-diff=2 × 10-5). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 × 10-3) and ABHD8 (P<2 × 10-3). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3′-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk

Genome-wide association study identifies 32 novel breast cancer susceptibility loci from overall and subtype-specific analyses.

Breast cancer susceptibility variants frequently show heterogeneity in associations by tumor subtype1-3. To identify novel loci, we performed a genome-wide association study including 133,384 breast cancer cases and 113,789 controls, plus 18,908 BRCA1 mutation carriers (9,414 with breast cancer) of European ancestry, using both standard and novel methodologies that account for underlying tumor heterogeneity by estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 status and tumor grade. We identified 32 novel susceptibility loci (P < 5.0 × 10-8), 15 of which showed evidence for associations with at least one tumor feature (false discovery rate < 0.05). Five loci showed associations (P < 0.05) in opposite directions between luminal and non-luminal subtypes. In silico analyses showed that these five loci contained cell-specific enhancers that differed between normal luminal and basal mammary cells. The genetic correlations between five intrinsic-like subtypes ranged from 0.35 to 0.80. The proportion of genome-wide chip heritability explained by all known susceptibility loci was 54.2% for luminal A-like disease and 37.6% for triple-negative disease. The odds ratios of polygenic risk scores, which included 330 variants, for the highest 1% of quantiles compared with middle quantiles were 5.63 and 3.02 for luminal A-like and triple-negative disease, respectively. These findings provide an improved understanding of genetic predisposition to breast cancer subtypes and will inform the development of subtype-specific polygenic risk scores