Overexpression of Bcl-2 is associated with apoptotic resistance to the G-quadruplex ligand 12459 but is not sufficient to confer resistance to long-term senescence

The triazine derivative 12459 is a potent G-quadruplex interacting agent that inhibits telomerase activity. This agent induces time- and dose-dependent telomere shortening, senescence-like growth arrest and apoptosis in the human A549 tumour cell line. We show here that 12459 induces a delayed apoptosis that activates the mitochondrial pathway. A549 cell lines selected for resistance to 12459 and previously characterized for an altered hTERT expression also showed Bcl-2 overexpression. Transfection of Bcl-2 into A549 cells induced a resistance to the short-term apoptotic effect triggered by 12459, suggesting that Bcl-2 is an important determinant for the activity of 12459. In sharp contrast, the Bcl-2 overexpression was not sufficient to confer resistance to the senescence-like growth arrest induced by prolonged treatment with 12459. We also show that 12459 provokes a rapid degradation of the telomeric G-overhang in conditions that paralleled the apoptosis induction. In contrast, the G-overhang degradation was not observed when apoptosis was induced by camptothecin. Bcl-2 overexpression did not modify the G-overhang degradation, suggesting that this event is an early process uncoupled from the final apoptotic pathway

The G-Quadruplex Ligand Telomestatin Impairs Binding of Topoisomerase IIIα to G-Quadruplex-Forming Oligonucleotides and Uncaps Telomeres in ALT Cells

In Alternative Lengthening of Telomeres (ALT) cell lines, specific nuclear bodies called APBs (ALT-associated PML bodies) concentrate telomeric DNA, shelterin components and recombination factors associated with telomere recombination. Topoisomerase IIIα (Topo III) is an essential telomeric-associated factor in ALT cells. We show here that the binding of Topo III to telomeric G-overhang is modulated by G-quadruplex formation. Topo III binding to G-quadruplex-forming oligonucleotides was strongly inhibited by telomestatin, a potent and specific G-quadruplex ligand. In ALT cells, telomestatin treatment resulted in the depletion of the Topo III/BLM/TRF2 complex and the disruption of APBs and led to the segregation of PML, shelterin components and Topo III. Interestingly, a DNA damage response was observed at telomeres in telomestatin-treated cells. These data indicate the importance of G-quadruplex stabilization during telomere maintenance in ALT cells. The function of TRF2/Topo III/BLM in the resolution of replication intermediates at telomeres is discussed

b thalassémie- état des connaissances, nouvelles perspectives thérapeutiques (les espoirs de la thérapie génique)

REIMS-BU Santé (514542104) / SudocSudocFranceF

MODE D'ACTION DE DEUX ALCALOIDES ANTITUMORAUX, LA FAGARONINE ET L'ETHOXYDINE, SUR LES PROGRAMMES DE DIFFERENCIATION, D'APOPTOSE ET DE MIGRATION DE CELLULES LEUCEMIQUES HUMAINES (DOCTORAT (BIOLOGIE CELLULAIRE ET MOLECULAIRE))

REIMS-BU Santé (514542104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

La pharmacogénétique en psychiatrie

REIMS-BU Santé (514542104) / SudocSudocFranceF

Etude de ligands de l'ADN G-quadruplexe sur l'intégralité des télomères : voies des dommages à l'ADN au cours de l'apoptose et de la senescence dans des lignées tumorales humaines

REIMS-BU Santé (514542104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Etude analytique des troubles neurologiques comportementaux, cognitifs et psychiatriques suite a un traumatisme crânien

REIMS-BU Santé (514542104) / SudocSudocFranceF

[Dental carie as chronic disease, a new therapeutic approach.]

International audienceFor many decades, oral health has been improving considerably in France. Caries indicators have decreased strongly. However, some "high risk" populations accumulate the majority of tooth decay. For them, health education and public health policies are inefficient. Tooth decay starts early and continues throughout their lives. Describing dental caries as a chronic pathology enables us to envisage alternative therapies, such as therapeutic patient education

Transcriptional and Posttranscriptional Regulation of Erythroid Gene Expression in Anthracycline-induced Differentiation of Human Erythroleukemic Cells

International audienceAclacinomycin (ACLA) and doxorubicin (DOX) were used at subtoxic concentrations to induce erythroid differentiation in the human leukemic cell line K562. Cell hemoglobinization was accompanied by the increased expression of genes encoding y-globin and porphobilinogen deaminase (PBGD), an enzyme of heme synthesis. By using run-on assays, ACLA was shown to induce an enhancement of the transcription of erythroid genes, including 'y-globin, PBGD, erythropoietin receptor, and GATA-1 transcription factor. In contrast, in DOX-treated cells, the transcription rate of these genes was unchanged in comparison with control cells. In addition, inhibition of mRNA synthesis with actinomycin D indicated that DOX induced an increased stability of PBGD and GATA-1 mRNAs, whereas ACLA did not affect the half-lives of these mRNAs. Because the increase in erythroid mRNA steady-state level in anthracycline-treated cells was inhibited by cycloheximide, this suggests that transcriptional activation in ACLA-treated cells and mRNA stabilization in DOX-treated cells were dependent on de novo protein synthesis. Finally, GATA-1 protein level was shown to be increased in ACLA-treated but not in DOX-treated cells. These two anthracyclines, although closely related in their structures, appeared to act as differentiation inducers by distinct mechanisms. Indeed, erythroid gene expression was demonstrated to be regulated transcriptionally by ACLA and mainly posttranscriptionally by DOX

Relative contribution of NF-kappaB and AP-1 in the modulation by curcumin and pyrrolidine dithiocarbamate of the UVB-induced cytokine expression by keratinocytes.

Following ultraviolet B treatment, expression of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-8 by NCTC 2544 keratinocyte cell line was significantly enhanced both at the mRNA and protein level. The UVB also increased the IL-10 steady-state mRNAs level. Radiation-induced cytokine overexpression was accompanied by NF-kappaB and AP-1 transcription factors activation as assessed by electrophoretic mobility shift assays. To investigate in keratinocytes the relative contributions of those transcription factors on UVB-mediated cytokine induction, cell cultures were supplemented with curcumin and pyrrolidine dithiocarbamate (PDTC), agents known to modulate NF-kappaB and AP-1 activation. Both compounds significantly inhibited NF-kappaB activation by UVB, but AP-1 activation was unaffected by curcumin while PDTC further stimulated its activation. In parallel, curcumin decreased, in a dose-dependent manner, the UVB-mediated overexpression of all three pro-inflammatory cytokines and only exhibited a moderate enhancing influence on IL-10 expression. In turn, the inhibitory influence of PDTC on radiation-induced TNF-alpha and IL-6 expression is much lower and in contrast to curcumin, it stimulated IL-8. Taken together, our data indicated that control of proinflammatory cytokine expression induced by UVB in keratinocytes required the selective inhibition of NF-kappaB activation. Simultaneous AP-1 activation by agents like PDTC might, partially or totally, depending on cytokine-type, counterbalanced the inhibitory effect exerted on UVB-induced NF-kappaB activation in keratinocytes