DNA replication stress and its impact on chromosome segregation and tumorigenesis.

Genome instability and cell cycle dysregulation are commonly associated with cancer. DNA replication stress driven by oncogene activation during tumorigenesis is now well established as a source of genome instability. Replication stress generates DNA damage not only during S phase, but also in the subsequent mitosis, where it impacts adversely on chromosome segregation. Some regions of the genome seem particularly sensitive to replication stress-induced instability; most notably, chromosome fragile sites. In this article, we review some of the important issues that have emerged in recent years concerning DNA replication stress and fragile site expression, as well as how chromosome instability is minimized by a family of ring-shaped protein complexes known as SMC proteins. Understanding how replication stress impacts on S phase and mitosis in cancer should provide opportunities for the development of novel and tumour-specific treatments.

Inducible Degradation of the Human SMC5/6 Complex Reveals an Essential Role Only during Interphase.

The cohesin- and condensin-related SMC5/6 complex has largely been studied in the context of DNA repair. Nevertheless, SMC5/6 has an undefined essential function even in the absence of cellular stress. Through the use of an auxin-inducible degradation system for rapidly depleting subunits of the SMC5/6 complex, we show that SMC5/6 is essential for viability in cancer-derived and normal human cells. Impairment of SMC5/6 function is associated with spontaneous induction of DNA damage, p53 activation, cell-cycle arrest, and senescence, as well as an increased frequency of various mitotic chromosome segregation abnormalities. However, we show that this chromosome missegregation is apparent only when SMC5/6 function is impaired during the preceding S and G2 phases. In contrast, degradation of SMC5/6 immediately prior to mitotic entry has little or no impact on the fidelity of chromosome segregation, highlighting the importance of the complex during interphase in order to ensure faithful sister chromatid disjunction.

The RIF1-PP1 Axis Controls Abscission Timing in Human Cells.

Abscission is the final step of cell division when the cytokinetic furrow ingresses completely, leading to midbody formation and plasma membrane fission [1]. In human cells, the Aurora-B-driven abscission checkpoint delays cytokinesis until any residual chromatin spanning the midbody is removed [2-5]. If this does not occur efficiently, uneven segregation of daughter genomes can occur. The mechanism by which the abscission checkpoint becomes satisfied to permit cytokinesis is poorly defined. Here, we identify RIF1 and its binding partner, protein phosphatase 1 (PP1), as being critical for regulation of abscission timing in human cells. We show that RIF1 promotes cytokinesis through recruitment of PP1 to the midbody, which then counteracts Aurora B kinase activity, leading to dephosphorylation of a regulator of abscission timing, CHMP4C [6-10]. Although RIF1 binds to unresolved DNA bridges that persist into telophase [11], we show that this cytokinetic function of the RIF1-PP1 axis is not limited to instances where cell division is perturbed by the presence of bridges. Nevertheless, we show that altering the balance of the opposing Aurora B kinase and PP1 phosphatase activities makes cells unresponsive to DNA bridges and sensitizes cells to agents that induce bridge formation. Our data define a new mechanism for regulation of abscission timing and emphasize how antagonism between kinases and phosphatases is a widespread mechanism for determining the timing of mitotic transactions. Because cancer cells experiencing oncogene-induced replication stress generate excessive mitotic DNA bridging [12], targeting this new regulatory pathway could be a promising therapeutic strategy.

Prolonged Activation of Invariant Natural Killer T Cells and TH2-Skewed Immunity in Stroke Patients.

BACKGROUND: Infection is highly prevalent and contribute significantly to mortality of stroke patients. In addition to the well described robust systemic lymphocytopenia and skewed T helper 2 (TH2)-immunity after stroke, emerging experimental evidence demonstrate that the development of infection poststroke is attributed by the activation of invariant natural killer T (iNKT) cells. In this prospective study, we examined the levels of a broad spectrum of inflammatory mediators, the activation status of iNKT cell in the blood of patients with various degree of stroke severity, and investigate whether these parameters differ in patients who later develop poststroke infections. METHODS AND RESULTS: We obtained blood from stroke patients and matching controls to perform flow cytometry and multiplex measurement of inflammatory mediators. Our data suggest a pronounced activation of iNKT cells in stroke patients as compared with matched Healthy and Hospital control patients. The magnitude of iNKT activation is positively correlated with the severity of stroke, supporting the hypothesis that iNKT cells may contribute in the modulation of the host immune response after stroke-associated brain injury. In addition, stroke severity is closely correlated with decreased TH1/TH2 ratio, increased production of interleukin (IL)-10, with infected stroke patients showing exacerbated production of IL-10. CONCLUSION: Stroke triggers a robust and sustained shift in systemic immunity in patients, including specific lymphopenia, robust activation of iNKT cells, systemic production of IL-10, and a prolonged TH2-skewed immunity, all are potential contributors to severe immune suppression seen in patients after stroke. Future studies with large sample size will provide potential causality relationship insights.

Translocation and dissemination of commensal bacteria in post-stroke infection.

Bacterial infection is highly prevalent in patients who have had a stroke. Despite the potential contribution of micro-aspiration in post-stroke pneumonia, we found that the majority of the microorganisms detected in the patients who developed infections after having a stroke were common commensal bacteria that normally reside in the intestinal tracts. In a mouse model of ischemic stroke, post-stroke infection was only observed in mice that were born and raised in specific-pathogen-free facilities; this was not seen in mice that were born and raised in germ-free facilities. Using high-throughput 16S rRNA gene amplicon sequencing and bioinformatics analyses, we provide evidence demonstrating that the source of the bacteria forming the microbial community in the lungs of post-stroke mice was indeed the host small intestine. Additionally, stroke-induced gut barrier permeability and dysfunction preceded the dissemination of orally inoculated bacteria to peripheral tissues. This study identifies a novel pathway in which stroke promotes the translocation and dissemination of selective strains of bacteria that originated from the host gut microbiota.

Nefrostomía percutánea ecoguiada con catéter Arrow: experiencia en el servicio de urología del Hospital Carlos Van Buren de Valparaíso entre los años 2008-2011 / Ecographic guiden percutaneus nephrostomy with Arrow catheter: experience in the urology service of the Carlos Van Buren of Valparaiso between 2008-2011

La nefrostomía es una técnica urológica que permite la derivación temporal de la vía urinaria buscando con esto preservar la función renal, aliviar el dolor y/o drenar la orina infectada. En el servicio de urología del Hospital Van Buren se implementó una técnica de nefrostomía percutánea ecoguiada con catéter Arrow 14 que ha permitido tratar precozmente a pacientes con patología urinaria obstructiva, con complicaciones menores y bajo costo...

Nephrostomy is an urologic technique that allows the temporary derivation of the urinary tract allowing with this to preserve the renal function, to alleviate the pain, to drain tinkles it infected. ln the Service of Urology of the Hospital Van Buren a percutaneous technique of nefrostomy has been ¡implemented guided by echography that has allowed treats to tens about patients with obstructive urinary pathology in precocious form, with smaller complications and low cost...

Uso de malla de polipropileno subalbugínea en orquiectomía bilateral por cáncer de próstata / Use of a testicular intralbugineal polypropylene mesh in bilateral orchiectomy for prostate cancer

Se presenta la experiencia del Servicio de Urología del Hospital Carlos Van Büren en el uso de malla de polipropileno intralbugínea como prótesis testicular, contemporánea a la orquiectomía subalbugínea bilateral por cáncer de próstata. Nuestra serie es de 30 pacientes, con un total de 60 testículos, correspondientes al período comprendido entre noviembre de 2001 y septiembre de 2002. Los resultados iniciales son alentadores.