Bystander effectors of chondrosarcoma cells irradiated at different LET impair proliferation of chondrocytes

While the dose-response relationship of radiation-induced bystander effect (RIBE) is controversial at low and high linear energy transfer (LET), mechanisms and effectors of cell-to-cell communication stay unclear and highly dependent of cell type. In the present study, we investigated the capacity of chondrocytes in responding to bystander factors released by chondrosarcoma cells irradiated at different doses (0.05 to 8 Gy) with X-rays and C-ions. Following a medium transfer protocol, cell survival, proliferation and DNA damages were quantified in bystander chondrocytes. The bystander factors secreted by chondrosarcoma cells were characterized. A significant and major RIBE response was observed in chondrocyte cells (T/C-28a2) receiving conditioned medium from chondrosarcoma cells (SW1353) irradiated with 0.1 Gy of X-rays and 0.05 Gy of C-ions, resulting in cell survivals of 36% and 62%, respectively. Micronuclei induction in bystander cells was observed from the same low doses. The cell survival results obtained by clonogenic assays were confirmed using impedancemetry. The bystander activity was vanished after a heat treatment or a dilution of the conditioned media. The cytokines which are well known as bystander factors, TNF-alpha and IL-6, were increased as a function of doses and LET according to an ELISA multiplex analysis. Together, the results demonstrate that irradiated chondrosarcoma cells can communicate stress factors to non-irradiated chondrocytes, inducing a wide and specific bystander response related to both doses and LET

A multimodal treatment of carbon ions irradiation, miRNA-34 and mTOR inhibitor specifically control high-grade chondrosarcoma cancer stem cells

Background and purposeHigh-grade chondrosarcomas are chemo- and radio-resistant cartilage-forming tumors of bone that often relapse and metastase. Thus, new therapeutic strategies are urgently needed.Material and methodsChondrosarcoma cells (CH-2879) were exposed to carbon-ion irradiation, combined with miR-34 mimic and/or rapamycin administration. The effects of treatment on cancer stem cells, stemness-associated phenotype, radioresistance and tumor-initiating properties were evaluated.ResultsWe show that high-grade chondrosarcoma cells contain a population of radioresistant cancer stem cells that can be targeted by a combination of carbon-ion therapy, miR-34 mimic administration and/or rapamycin treatment that triggers FOXO3 and miR-34 over-expression. mTOR inhibition by rapamycin triggered FOXO3 and miR-34, leading to KLF4 repression.ConclusionOur results show that particle therapy combined with molecular treatments effectively controls cancer stem cells and may overcome treatment resistance of high-grade chondrosarcoma

Hélicase RecQ, syndrome de Werner, et réparation de l'ADN par recombinaison homologue

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Homologous recombination induced by replication inhibition, is stimulated by expression of mutant p53

International audienceCell cycle control, faithful DNA replication, repair and recombination are associated in a network of pathways controlling genome maintenance. In mammalian cells, inhibition of replication produces DNA breaks and induces RAD51-dependent recombination, in a late step. Here we examine whether the status of p53 aects this process in mouse L-cells containing a recombination substrate. We show that expression of the mutant His175 p53 strongly stimulates recombination induced by aphidicolin, in a late step (kinetically related to the RAD51 step). Mutant p53 stimulates recombination induced by the replication elongation inhibitors (aphidi-colin, hydroxyurea and Ara-C) but is without eect on recombination induced by the initiation inhibitors (mimosine and ciclopirox olamine). We compared the impact of several p53 mutations showing dierent eects on the G1 checkpoint and on recombination. We show that the mutant Pro273 p53 protein, which does not alter the G1 checkpoint, strongly stimulates recombination induced by elongation inhibitors. These results show that p53 can act on recombination induced by replication arrest independently of its role in the G1 checkpoint. An action of p53 via the RAD51 pathway is discussed

Werner Syndrome Protein - Unwinding Function to Explain Disease

International audienceWerner syndrome (WS) is one of three heritable human genetic instability/cancer predisposition syndromes that result from mutations in a member of the gene family encoding human RecQ helicases. Cellular defects are a prominent part of the WS phenotype. Here we review recent work to identify in vi-vo functions of the WS protein and discuss how loss of function leads to cellular defects. These new results provide clues to the origin of cell lineage-specific defects in WS patients and suggest a broader role for Werner protein function in determining disease risk in the general population

p53's double life: transactivation-independent repression of homologous recombination

International audienceThe tumor suppressor protein p53 controls cell cycle checkpoints and apoptosis via the transactivation of several genes. However, data from various laboratories suggest an additional role for p53: transcription-independent suppression of homologous recombination (HR). Genetic and physical interactions among p53, HR proteins (e.g. RAD51 and RAD54) and HR-DNA inter-mediates show that p53 acts directly on HR during the early and late steps of recombination. Complementary to the MSH2 mismatch-repair system, p53 appears to impair excess HR by controlling the minimal efficiency processing segment and by reversing recombination intermediates. By controlling the balance between the BLM and the RAD51 pathways, this direct role of p53 could maintain genome stability when replication forks are stalled at regions of DNA damage. In this article, we discuss the direct role of p53 on HR and the consequences for genome stability, tumor protection and speciation

Rôle direct de

Le gène suppresseur de tumeurs p53 contrôle l’expression d’une collection de gènes réglant le cycle cellulaire et l’apoptose, empêchant ainsi la prolifération de cellules porteuses de dommages et de remaniements génétiques. Cependant, une série de travaux a mis en évidence un nouveau mécanisme, indépendant de l’activité de transactivateur de transcription, par lequel p53 participe au maintien de la stabilité du génome: la répression de la recombinaison homologue. Ce rôle nouvellement décrit prévient l’instabilité génétique due à un excès de recombinaison homologue associé aux stress génotoxiques. Il s’exerce directement par l’interaction de la protéine p53 avec les protéines de recombinaison homologue et avec les structures d’ADN intermédiaires. Le domaine central de p53 est impliqué dans l’interaction avec Rad51, à une étape précoce de la recombinaison homologue, et le domaine carboxyterminal de p53 est nécessaire à son interaction avec Rad54 et avec les intermediaries de recombinaison homologue, à une étape tardive de la recombinaison homologue. L’implication potentielle de ce mécanisme parallèle de p53 pour la stabilité du génome, la speciation et la protection tumorale sera discutée

Réponse celluliare à l'exposition aux éléments chimiques stables ou radioacttifs

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