Role of tyrosyl-DNA phosphodiesterase 1 and inter-players in regulation of tumor cell sensitivity to topoisomerase I inhibition

Tyrosyl-DNA phosphodiesterase 1 (TDP1) plays a unique function as it catalyzes the repair of topoisomerase I-mediated DNA damage. Thus, ovarian carcinoma cell lines exhibiting increased TDP1 levels and resistance to the topoisomerase I poisons campthotecins were used to clarify the role of this enzyme. The camptothecin gimatecan was employed as a tool to inhibit topoisomerase I because it produces a persistent damage. The resistant sublines displayed an increased capability to repair drug-induced single-strand breaks and a reduced amount of drug-induced double-strand breaks, which was enhanced following TDP1 silencing. In loss of function studies using U2-OS cells, we found that TDP1 knockdown did not produce a change in sensitivity to camptothecin, whereas co-silencing of other pathways cooperating with TDP1 in cell response to topoisomerase I poisons indicated that XRCC1 and BRCA1 were major regulators of sensitivity. No change in cellular sensitivity was observed when TDP1 was silenced concomitantly to RAD17, which participates in the stabilization of collapsed replication forks. The expression of dominant-negative PARP1 in cells with reduced expression of TDP1 due to a constitutively expressed TDP1 targeting microRNA did not modulate cell sensitivity to camptothecin. Mild resistance to gimatecan was observed in cells over-expressing TDP1, a feature associated with decreased levels of drug-induced single-strand breaks. In conclusion, since TDP1 alone can account for mild levels of camptothecin resistance, repair of topoisomerase I-mediated DNA damage likely occurs through redundant pathways mainly implicating BRCA1 and XRCC1, but not RAD17 and PARP1. These findings may be relevant to define novel therapeutic strategies.     

Epidemiology of spondyloarthritis in Argentina

IntroductionSpondyloarthritis (SpA) includes a group of diseases that share immunogenetic, clinical and radiologic findings, with a particular involvement of the axial skeleton and the entheses.MethodsSpA patients attending ambulatory care in 11 rheumatology services located in 6 Argentine provinces were included in a prospective, observational multicentre cohort of SpA in Argentina (Iberoamerican Spondyloarthritis Registry [RESPONDIA]). Data collected were transmitted online and stored in the Spanish spondyloarthritis registry (REGISPONSER) Web site. Sociodemographic, clinical features and diagnosis, disease activity, functional status, quality of life, work status, radiographic changes and treatment data were collected by means of validated tools.ResultsA total of 402 patients were included; 59% were male, with median age of 48.3 years and median disease duration of 8 years; 68.7% of patients belonged to middle and lower-middle social classes. Eighty-six patients were diagnosed with ankylosing spondylitis (AS), 242 with psoriatic arthritis, 25 with reactive arthritis, 10 with SpA associated with inflammatory bowel disease, 33 with undifferentiated SpA and 6 with juvenile AS. The median score was 2.6 for the Bath AS Functional Index, 3.8 for the Bath AS Disease Activity Index and 5 for the Bath AS Radiology Index. The lower social class patients achieved a worse Bath AS Functional Index than other social classes and a worse Bath AS Disease Activity Index, compared with upper-middle class.ConclusionsThe sociodemographic distribution pattern observed in these SpA patients was similar to that expected in the general population of Argentina, with worse functional capacity and higher disease activity observed in the lower social classes.     

The RacGAP ArhGAP15 is a master negative regulator of neutrophil functions

In phagocytes, GTPases of the Rac family control crucial antimicrobial functions. The RacGAP ArhGAP15 negatively modulates Rac activity in leukocytes, but its in vivo role in innate immunity remains largely unknown. Here we show that neutrophils and macrophages derived from mice lacking ArhGAP15 presented higher Rac activity but distinct phenotypes. In macrophages, the loss of ArhGAP15 induced increased cellular elongation and membrane protrusions but did not modify chemotactic responses. Conversely, the lack of ArhGAP15 in neutrophils affected critical Rac-dependent antimicrobial functions, specifically causing enhanced chemotactic responses, straighter directional migration, amplified reactive oxygen species production, increased phagocytosis, and improved bacterial killing. In vivo, in a model of severe abdominal sepsis, these effects contributed to increase neutrophil recruitment to the site of infection, thereby limiting bacterial growth, controlling infection spread, reducing systemic inflammation, and ultimately improving survival in ArhGAP15-null mice. Altogether, these results demonstrate the relevance of ArhGAP15 in the selective regulation of multiple neutrophil functions, suggesting that ArhGAP15 targeting might be beneficial in specific pathologic settings like severe sepsis.     

Factors determining response to antiepileptic drugs in randomized controlled trials. A systematic review and meta-analysis

Purpose: Because of the lack of head‐to‐head adjunctive‐therapy trials of antiepileptic drugs (AEDs) in refractory partial epilepsy, meta‐analyses of placebo‐controlled randomized controlled trials (RCTs) represent a potentially important source of evidence to guide treatment decisions. However, such indirect comparisons raise various methodologic issues that may hamper their relevance. Methods: All RCTs in adult refractory partial epilepsy were analyzed to assess whether efficacy outcomes are influenced by: characteristics of patients and trials ; use of last observation carried forward (LOCF) analysis; evaluation period (entire period versus maintenance period); and year of publication. A meta‐analysis of these AEDs was then performed taking these factors into consideration. Key Findings: Sixty‐three RCTs evaluating 20 AEDs were included. The following variables influenced efficacy estimates: (1) responder rates correlated positively with duration of the entire treatment period (p = 0.038); (2) response to placebo was significantly greater in the maintenance period than in the entire treatment period (p = 0.005); (3) responder rates increased over the years both for AEDs (p < 0.001) and for placebo (p = 0.001); (4) LOCF analysis overestimated responder rates for AEDs (p < 0.001) and for placebo (p = 0.001) compared with completer‐based analysis, and the overestimation correlated positively with withdrawal rates (p < 0.001). A meta‐analysis of available data showed large differences in efficacy ranking in relation to dose selection and type of analysis, but these were mostly nonsignificant due to statistical power limitations. Significance: Several methodologic issues hamper the relevance of indirect comparisons of AEDs in the adjunctive‐therapy of refractory partial epilepsy. Some of these issues could be overcome by improved standardization in the reporting of efficacy outcomes.     

A functional polymorphism in the SCN1A gene does not influence antiepileptic drug responsiveness in Italian patients with focal epilepsy

A splice site variation (c.603-91G>A or rs3812718) in the SCN1A gene has been claimed to influence efficacy and dose requirements of carbamazepine and phenytoin. We investigated the relationship between c.603-91G>A polymorphism and response to antiepileptic drugs (AEDs) in 482 patients with drug-resistant and 401 patients with drug-responsive focal epilepsy. Most commonly used AEDs were carbamazepine and oxcarbazepine. The distribution of c.603-91G>A genotypes was similar among drug-resistant and drug-responsive subjects, both in the entire population and in the groups treated with carbamazepine or oxcarbazepine. There was no association between the c.603-91G>A genotype and dosages of carbamazepine or oxcarbazepine. These findings rule out a major role of the SCN1A polymorphism as a determinant of AED response.