Chromosomal instability (CIN) is a major hallmark of human cancer and might contribute to tumorigenesis. Genes required for the normal progression of mitosis represent potential CIN genes and, as such, are important tumour suppressors. The Chk2 kinase and its downstream targets p53 and Brca1 are tumour suppressors that have been functionally linked to the DNA damage response pathway. Here, we report a function of Chk2, independent of p53 and DNA damage, that is required for proper progression of mitosis, and for the maintenance of chromosomal stability in human somatic cells. Depletion of Chk2 or abrogation of its kinase activity causes abnormal mitotic spindle assembly associated with a delay in mitosis, which promotes the generation of lagging chromosomes, chromosome missegregation and CIN, while still allowing survival and growth. Furthermore, we have identified Brca1 as a mitotic target of the Chk2 kinase in the absence of DNA damage. Accordingly, loss of BRCA1 or its Chk2-mediated phosphorylation leads to spindle formation defects and CIN. Thus, the CHK2-BRCA1 tumour suppressor pathway is required for chromosomal stability, which might contribute to their tumour suppressor function.

Conventional nonsteroidal antiinflammatory drugs (NSAIDs) are associated with acute renal failure, but cyclooxygenase-2 inhibitors have not been comparatively evaluated. The authors conducted a nested case-control study to assess the association between exposure to NSAIDs, including cyclooxygenase-2 inhibitors, and hospitalization for acute renal failure. They identified 121,722 new NSAID users older than age 65 years from the administrative health care databases of Quebec, Canada, in 1999-2002. Data for 4,228 cases and 84,540 controls matched on age and follow-up time were analyzed by using conditional logistic regression, adjusted for sex, age, health status, health care utilization measures, exposure to contrast agents, and nephrotoxic medications. The risk of acute renal failure for all NSAIDs combined was highest within 30 days of treatment initiation (adjusted rate ratio (RR) = 2.05, 95% confidence interval (CI): 1.61, 2.60) and receded thereafter. The association with acute renal failure within 30 days of therapy initiation was comparable for rofecoxib (RR = 2.31, 95% CI: 1.73, 3.08), naproxen (RR = 2.42, 95% CI: 1.52, 3.85), and nonselective, non-naproxen NSAIDs (RR = 2.30, 95% CI: 1.60, 3.32) but was borderline lower for celecoxib (RR =1.54, 95% CI: 1.14, 2.09; test for interaction comparing celecoxib with rofecoxib, p = 0.057). There was a significant association for both selective and nonselective NSAIDs with acute renal failure, but confirmatory studies are required.

Background:The association between the use of proton pump inhibitors and the risk of Clostridium difficile-associated disease (CDAD) is controversial. In this study we re-examined a previously reported association between the use of proton pump inhibitors and the development of community-acquired CDAD, this time using an alternative case definition of the disease. Methods:We performed a case-control study of community-acquired CDAD using a United Kingdom clinical research database. Patients receiving oral vancomycin therapy were identified as having CDAD, the only indication for this drug. Each case subject was matched with up to 10 control subjects. Neither the cases nor the controls had been admitted to hospital in the year before the date of the vancomycin prescription (index date). Conditional logistic regression analysis was used to adjust for key covariates. Results:We identified 317 cases of community-acquired CDAD treated with oral vancomycin therapy and 3167 matched control subjects. Exposure to a proton pump inhibitor in the 90 days before the index date was associated with an increased risk of CDAD (odds ratio [OR] 3.5, 95% confidence interval [CI] 2.3-5.2). Antibiotic exposure in the 90 days before the index date was also a significant risk factor for community-acquired CDAD (OR 8.2, 95% CI 6.1-11.0), even though 45% of the case subjects had not received a prescription for an antibiotic during that period. Certain comorbidities, in particular renal failure, inflammatory bowel disease and malignant disease, as well as prior methicillinresistant Staphylococcus aureus infection, were also associated with an increased risk.Interpretation: Proton pump inhibitor use was associated with an increased risk of community-acquired CDAD, when cases were defined by receipt of prescription for oral vancomycin therapy. Prior antibiotic exposure was also a significant risk factor, but a significant proportion of the patients with community-acquired CDAD had no such exposure. CMAJ 2006;175(7):745-8 Abstract

Highlights d Comparison of chromatin accessibility between murine und human tissue Treg cells d TCR tracking revealed clonal relationship between tissue and blood BATF + CCR8 + Tregs d Treg cells from healthy tissues were similar to CCR8 + Treg cells from tumors d Tfh-like differentiation program induces tissue Treg cell repair characteristics

Marietta Blau Grant (Austrian Agency for International Cooperation in Education and Research; OeAD-GmbH) and mobility scholarship (Medical University of Graz).

About 80% to 90% of females are informative for X- inactivation/methylation analysis with the probe M27 beta, which would therefore seem attractive in assessing clonality in hematologic cell populations. Eighteen acute lymphoid or myeloid leukemias, three chronic lymphocytic leukemias, and three chronic myelogenous leukemias as well as 12 malignant non-Hodgkin's lymphomas mostly showed extremely skewed clonal X inactivation (median allelic cleavage ratio [ACR] of unmethylated/inactive M27 beta alleles was 50, range 1 to 100) or hypermethylation of both alleles. Two lymphomas showed random M27 beta X inactivation but clonal antigen-receptor gene rearrangements. In normal peripheral blood leukocytes from 105 healthy females aged 2 to 96 years, the median ACR was 2 (range 1 to 100). Thus, it was significantly lower than in the leukemias (P = .0001, Mann-Whitney test), but extremely skewed patterns (ACR > 10.8, ie, >80th percentile) were seen not only in the leukemias but also in 21/105 samples (20%) of normal leukocytes, and significantly more frequent in a population of elderly women (aged 75 to 96 years) compared with healthy children (aged 2 to 8 years) and younger women (aged 20 to 58 years) (P =.00125; chi 2 test). We conclude that in a population of cells derived from the hematopoietic system where clonality is uncertain, skewed M27 beta patterns are not reliable indicators for the presence of a clonal neoplastic disorder. The basis for severe X-inactivation skewing is unclear at present, but this finding raises interesting questions regarding the composition of the hematopoietic stem cell pool.

No abstract

Decreased cellular accumulation of cisplatin is a frequently observed mechanism of resistance to the drug. Beside passive diffusion, several cellular proteins using ATP hydrolysis as an energy source are assumed to be involved in cisplatin transport in and out of the cell. This investigation aimed at clarifying the contribution of intracellular ATP as an indicator of energy-dependent transport to cisplatin resistance using the A2780 human ovarian adenocarcinoma cell line and its cisplatin-resistant variant A2780cis. Depletion of intracellular ATP with oligomycin significantly decreased cellular platinum accumulation (measured by flameless atomic absorption spectrometry) in sensitive but not in resistant cells, and did not affect cisplatin efflux in both cell lines. Inhibition of Na(+),K(+)-ATPase with ouabain reduced platinum accumulation in A2780 cells but to a lesser extent compared with oligomycin. Western blot analysis revealed lower expression of Na(+),K(+)-ATPase α(1) subunit in resistant cells compared with sensitive counterparts. The basal intracellular ATP level (determined using a bioluminescence-based assay) was significantly higher in A2780cis cells than in A2780 cells. Our results highlight the importance of ATP-dependent transport, among other processes mediated by Na(+),K(+)-ATPase, for cisplatin influx in sensitive cells. Cellular platinum accumulation in resistant cells is reduced and less dependent on energy sources, which may partly result from Na(+),K(+)-ATPase downregulation. Our data suggest the involvement of other ATP-dependent processes beside those regulated by Na(+),K(+)-ATPase. Higher basal ATP level in cisplatin-resistant cells, which appears to be a consequence of enhanced mitochondrial ATP production, may represent a survival mechanism established during development of resistance.