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A previous study has reported that knockdown of RING finger protein 2 (RNF2) increases the radiosensitivity of esophageal cancer cells both in vitro and in vivo. However, the effect of RNF2 knockdown on radiosensitivity in squamous cell carcinoma (SqCC) remains unknown. For this, NCI-H226 and SK-MES-1 cells were exposed to X-ray irradiation and then RNF2 levels were determined. RNF2 was knocked-down and stable transfectants were selected. Radiosensitivity, cell proliferation, apoptosis, cell cycle, and [gamma]-H2AX foci formation were evaluated. Interaction among ataxia telangiectasia mutated protein (ATM), mediator of DNA damage checkpoint 1 (MDC1), and H2AX were examined. Xenograft models were used to explore the effect of RNF2 knockdown on radiosensitivity in vivo. The results showed that RNF2 expression was significantly increased by X-ray irradiation. RNF2 knockdown combined with X-ray irradiation markedly inhibited cell proliferation, caused cell cycle arrest at the G1 phase, and induced cell apoptosis. In addition, RNF2 knockdown enhanced the radiosensitivity of SqCC cells, inhibited irradiation-induced [gamma]-H2AX foci formation, and impaired the interactions among ATM, MDC1, and H2AX. Furthermore, combination of RNF2 knockdown and X-ray irradiation suppressed tumor growth and promoted tumor cell apoptosis in vivo. RNF2 may be a new therapeutic target to enhance the radiosensitivity of SqCC cells in lung. Key words: ionizing radiation, lung squamous cell carcinoma, radiosensitivity, RNF2, [gamma]-H2AX foci. Une étude précédente a rapporté que le knockdown de la protéine RNF2 (RING finger protein 2) accroit la radiosensibilité des cellules de cancer oesophagien in vitro et in vivo. Toutefois, l'effet du knockdown de RNF2 sur la radiosensibilité du carcinome épidermoïde demeure inconnu. Les cellules NCI-H226 et SK-MES-1 ont été exposées à une irradiation aux rayons X et les niveaux de RNF2 ont été déterminés. RNF2 a été inactivé et des transfectants stables ont été sélectionnés. La radiosensibilité, la prolifération, l'apoptose, le cycle cellulaire et la formation de foyers de [gamma]-H2AX ont été évalués. Les interactions entre les protéines ATM (ataxia telangiectasia mutated protein), MDC1 (mediator of DNA damage checkpoint 1) et H2AX ont été examinées. Des modèles de xénogreffes ont été utilisés pour explorer les effets du knockdown de RNF2 sur la radiosensibilité in vivo. Les résultats ont montré que l'expression de RNF2 était significativement accrue par l'irradiation aux rayons X. Le knockdown de RNF2 combiné à l'irradiation aux rayons X inhibait de façon marquée la prolifération cellulaire, provoquait un arrêt du cycle cellulaire en phase G1 et induisait l'apoptose des cellules. De plus, le knockdown de RNF2 augmentait la radiosensibilité des cellules de carcinome épidermoïde, inhibait la formation de foyers de [gamma]-H2AX induits par l'irradiation et diminuait les interactions entre ATM, MDC1 et H2AX. Par ailleurs, la combinaison du knockdown de RNF2 et de l'irradiation aux rayons X supprimait la croissance tumorale et favorisait l'apoptose des cellules tumorales in vivo. RNF2 pourrait constituer une nouvelle cible thérapeutique pour accroitre la radiosensibilité des cellules de carcinome épidermoïde du poumon. [Traduit par la Rédaction] Mots-clés: radiation ionisante, carcinome épidermoïde du poumon, radiosensibilité, RNF2, foyers de [gamma]-H2AX., Introduction Lung cancer is the leading cause of cancer-related mortality worldwide (Swanton and Govindan 2016). An estimated 1.8 million new cases were diagnosed in 2012 (Torre et al. 2015). The [...]

The tumor suppressor p53, a master regulator of the cellular response to stress, is tightly regulated by the E3 ubiquitin ligase MDM2 via an autoregulatory feedback loop. In addition to its well-established role in tumorigenesis, p53 has also been associated with aging in mice. Several mouse models with aberrantly increased p53 activity display signs of premature aging. However, the relationship between dysfunction of the MDM2/p53 axis and human aging remains elusive. Here, we have identified an antiterminating homozygous germline mutation in MDM2 in a patient affected by a segmental progeroid syndrome. We show that this mutation abrogates MDM2 activity, thereby resulting in enhanced levels and stability of p53. Analysis of the patient's primary cells, genome-edited cells, and in vitro and in vivo analyses confirmed the MDM2 mutation's aberrant regulation of p53 activity. Functional data from a zebrafish model further demonstrated that mutant Mdm2 was unable to rescue a p53-induced apoptotic phenotype. Altogether, our findings indicate that mutant MDM2 is a likely driver of the observed segmental form of progeria., Introduction Two compelling lines of evidence establish p53 as a major tumor suppressor in humans. First, heterozygous germline mutations in the p53-encoding gene TP53 cause Li-Fraumeni syndrome, an autosomal-dominant and [...]

Byline: Bora. Uysal, Hakan. Gamsiz, Ferrat. Dincoglan, Selcuk. Demiral, Omer. Sager, Bahar. Dirican, Murat. Beyzadeoglu Background: Radiodermatitis is a frequent side effect of breast cancer radiotherapy (RT). Treating radiation oncologist [...]

Error-free repair of DNA double-strand breaks (DSBs) is achieved by homologous recombination (HR), and BRCA1 is an important factor for this repair pathway (1). In the absence of BRCA1-mediated HR, the administration of PARP inhibitors induces synthetic lethality of tumour cells of patients with breast or ovarian cancers (2,3). Despite the benefit of this tailored therapy, drug resistance can occur by HR restoration (4). Genetic reversion of BRCA1-inactivating mutations can be the underlying mechanism of drug resistance, but this does not explain resistance in all cases (5). In particular, little is known about BRCA1-independent restoration of HR. Here we show that loss of REV7 (also known as MAD2L2) in mouse and human cell lines re-establishes CTIP-dependent end resection of DSBs in BRCA1 deficient cells, leading to HR restoration and PARP inhibitor resistance, which is reversed by ATM kinase inhibition. REV7 is recruited to DSBs in a manner dependent on the H2AX-MDC1RNF8-RNF168-53BP1 chromatin pathway, and seems to block HR and promote end joining in addition to its regulatory role in DNA damage tolerance (6). Finally, we establish that REV7 blocks DSB resection to promote non-homologous end-joining during immunoglobulin class switch recombination. Our results reveal an unexpected crucial function of REV7 downstream of 53BP1 in coordinating pathological DSB repair pathway choices in BRCA1deficient cells., To identify mechanisms of BRCAl-independent restoration of the HR pathway, we carried out a loss-of-function short hairpin RNA (shRNA) screen using the KB1P-B11 and KB1P-G3 celllines that we previously derived [...]

The effect of electron beam (E-beam) radiation on a series of styrenic block copolymers (SBCs) was investigated. These SBCs included newly developed poly(styrene-block-isoprene/butadiene-block-styrene) (SIBS), poly(styrene-block-butadiene-block-styrene) (SBS), and poly(styrene-block-isoprene-block-styrene) (SIS). The tensile properties, stress relaxation, molecular weight, and dynamical mechanical properties were studied. Generally, the crosslink density and tensile moduli of SBCs increased with increasing of E-beam radiation dose. The tensile strength of SIBS and SIS was shown to first decrease at lower E-beam radiation dose (190 kGy). The tensile strength of SBS was significantly decreased at high E-beam radiation dose (>190 kGy). This was attributed to the differences between entanglement before E-beam radiation and the homogeneity of the crosslink network after exposure., INTRODUCTION Electron beam (E-beam) radiation as an efficient way to crosslink polymers has advantages of short residence time and initiation without use of initiator [l-3]. Commercial interest has led to [...]