Trisomy 21 in childhood acute lymphoblastic leukemia: a Pediatric Oncology Group study (8602)

Of 1,036 children with newly diagnosed non-T, non-B acute lymphoblastic leukemia (ALL) and a demonstrated cytogenetic abnormality treated on the frontline Pediatric Oncology Group (POG) therapeutic trial 8602, there were 33 patients with trisomy 21 as the sole abnormality. Of these 33, 14 had Down syndrome (DS). Although the non-DS (NDS) trisomy 21 cases tended to be older than the DS cases, there were no other significant differences in clinicobiologic features nor in treatment outcomes between the DS and NDS groups, nor between the entire trisomy 21 group and the other chromosome abnormality group. Among NDS patients with +21 and one additional abnormality, +X, +16, -20, and structural abnormalities involving 6q or 12p were common findings. Kaplan-Meier event-free survival (EFS) curves showed a 4-year EFS of 80% (SE, 12%) in NDS trisomy 21 cases, 71% (SE, 22%) in DS cases with trisomy 21 as the sole abnormality, and 69% (SE, 2%) in cases with other chromosome abnormalities. Trisomy 21 as a sole acquired abnormality in NDS patients suggests a good prognosis.     

Violation of the 12/23 rule of genomic V(D)J recombination is common in lymphocytes

V(D)J genomic recombination joins single gene segments to encode an extensive repertoire of antigen receptor specificities in T and B lymphocytes. This process initiates with double-stranded breaks adjacent to conserved recombination signal sequences that contain either 12- or 23-nucleotide spacer regions. Only recombination between signal sequences with unequal spacers results in productive coding genes, a phenomenon known as the “12/23 rule.” Here we present two novel genomic tools that allow the capture and analysis of immune locus rearrangements from whole thymic and splenic tissues using second-generation sequencing. Further, we provide strong evidence that the 12/23 rule of genomic recombination is frequently violated under physiological conditions, resulting in unanticipated hybrid recombinations in ∼10% of Tcra excision circles. Hence, we demonstrate that strict adherence to the 12/23 rule is intrinsic neither to recombination signal sequences nor to the catalytic process of recombination and propose that nonclassical excision circles are liberated during the formation of antigen receptor diversity.The adaptive immune system recognizes a seemingly unlimited array of antigens via a highly diverse repertoire of B and T cell antigen receptors (Sakano et al. 1979; Tonegawa 1983; Davis and Bjorkman 1988). These heterodimeric molecules contain a variable antigen-binding domain encoded through recombination of variable (V), diversity (D, only present in some loci), and joining (J) gene segments. Each gene segment is flanked by a canonical recombination signal sequence (RSS) composed of conserved heptamer and nonamer motifs separated by a less well-conserved spacer of either 12 or 23 base pair (bp) in length (for review, see Schatz and Ji 2011). V(D)J recombination is initiated by the lymphocyte-specific recombination activating gene (RAG) recombinase, a complex mainly composed of RAG1 and RAG2 proteins. The RAG recombinase introduces double-stranded breaks at RSS sites, resulting in the generation of covalently sealed hairpins at gene segment ends. Before re-ligation, these DNA ends may be processed further to produce local deletions or nontemplated nucleotide (N base) additions. Multiple enzymes, including components of the nonhomologous end joining (NHEJ) complex, are involved in the processing and repair of the final genomic coding junction (Fig. 1A). In parallel, a signal junction is generated by ligating the remaining DNA ends with few sequence modifications to form an excision circle (EC). Recombination between 12-bp and 23-bp RSSs, the 12/23 rule, ensures that productive coding rearrangements are formed from V, D, and J gene segments (Fig. 1A). Although junctions have been reported that do not keep to the 12/23 rule (Mansikka and Toivanen 1991; Shimizu et al. 1991), these are either largely confined to nonphysiological recombination events in the absence of regular RAG (Talukder et al. 2004) or NHEJ (Bogue et al. 1997; Han et al. 1997) complex expression, or they are triggered by cryptic RSS sequences (Davila et al. 2007). Non-12/23 junctions under physiological conditions are thought to be rare, the most common being in VDDJ rearrangements of the Igh locus that occur once per ∼800 cells (Briney et al. 2012). In addition to violating the 12/23 rule, other noncanonical rearrangements form hybrid signal-to-coding junctions. These are typically generated in artificial systems (Lewis et al. 1988; Morzycka-Wroblewska et al. 1988; Alexandre et al. 1991; Bogue et al. 1997; Han et al. 1997; Melek et al. 1998; Bredemeyer et al. 2006; Briney et al. 2012) but may also be detected at low frequency in vivo under physiological conditions (Alexandre et al. 1991; Carroll et al. 1993; Sollbach and Wu 1995; VanDyk et al. 1996).Open in a separate windowFigure 1.Schematic representation of RAG-mediated V(D)J recombination showing the relative mapping positions of DP and RF read-pairs from recombined genomic and excised circular DNA. (A) Hypothetical genomic locus containing variable (blue box) and joining (red box) elements flanked by recombination signal sequence (RSS) motifs (blue and red triangles) are bound and brought into close association by the recombination activating gene (RAG) complex (gray). RAG-mediated double-stranded cleavage at RSS sites precedes genomic deletion (coding) end processing by the nonhomologous end joining (NHEJ) complex. Coding ends are covalently hair-pinned (gray circle section) and reopened prior to ligation. Secondarily, the excision circle (EC; signal) junction is ligated from unprocessed DNA ends with little modification. (B) Sequencing library fragments from recombined EC and genomic (g) DNA are shown. Read-pair sequences from fragments are mapped back to the reference genome, allowing junction-spanning reads to be identified. Gray arrows represent “standard” read-pairs generated from EC DNA or gDNA and map to the reference genome in standard orientation separated by a mapping distance equal to the initial fragment length. Deletion read-pairs (DPs) spanning a coding junction map to the reference genome with standard relative orientation—the forward read (green) mapping 5′ of and facing the reverse read (red)—but are separated by mapping distances greater than the initial fragment length. Reverse-forward read-pairs (RFs) spanning the signal junction map to the reference genome in an inverted relative read orientation so that the reverse read (red) maps 5′ of and faces away from the forward read (green). RF read-pairs are separated by the full length of the circle from which they originate rather than the initial library fragment length.Most studies of V(D)J recombination have been limited to PCR amplification and Sanger sequencing of predefined coding, signal, or transgenic junctions. Second-generation sequencing technologies, which allow an unbiased capture of rearrangements, have only been used to study V(D)J recombination in T cell receptor (TCR)–derived mRNA sequences (Genolet et al. 2012). This approach is limited to analyses of coding junctions in productive, successfully expressed mRNAs and excludes quantitative insights into genomic recombination frequencies.We have developed two complementary techniques, excision circle (EC)-seq and immune region (IR)-seq, for direct second-generation sequencing analyses of V(D)J rearrangements in EC and chromosomal DNA. Using these techniques, we report that an abundance of unanticipated J-J and, to a lesser extent, V-V excision circles is produced under physiological conditions at multiple antigen receptor chain loci in both mice and humans, thus both violating the 12/23 rule of recombination and resulting in coding-to-signal hybrid junctions. Our data suggest that adherence to the 12/23 rule is not intrinsic to RSS motifs or the RAG recombinase but are conferred by additional factors and that these high-frequency nonclassical rearrangements are liberated during production of a diverse immune repertoire.     

Double bypass for inoperable pancreatic malignancy at laparotomy: postoperative complications and long-term outcome

INTRODUCTION

Between 4% and 13% of patients with operable pancreatic malignancy are found unresectable at the time of surgery. Double bypass is a good option for fit patients but it is associated with high risk of postoperative complications. The aim of this study was to identify pre-operatively which patients undergoing double bypass are at high risk of complications and to assess their long-term outcome.

METHODS

Of the 576 patients undergoing pancreatic resections between 2006 and 2011, 50 patients who underwent a laparotomy for a planned pancreaticoduodenectomy had a double bypass procedure for inoperable disease. Demographic data, risk factors for postoperative complications and pre-operative anaesthetic assessment data including the Portsmouth Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM) and cardiopulmonary exercise testing (CPET) were collected.

RESULTS

Fifty patients (33 men and 17 women) were included in the study. The median patient age was 64 years (range: 39–79 years). The complication rate was 50% and the in-hospital mortality rate was 4%. The P-POSSUM physiology subscore and low anaerobic threshold at CPET were significantly associated with postoperative complications (p=0.005 and p=0.016 respectively) but they were unable to predict them. Overall long-term survival was significantly shorter in patients with postoperative complications (9 vs 18 months). Postoperative complications were independently associated with poorer long-term survival (p=0.003, odds ratio: 3.261).

CONCLUSIONS

P-POSSUM and CPET are associated with postoperative complications but the possibility of using them for risk prediction requires further research. However, postoperative complications following double bypass have a significant impact on long-term survival and this type of surgery should therefore only be performed in specialised centres.     

雷洛昔芬对绝经后猴子冠状动脉粥样硬化的影响

已证实雷洛昔芬在骨和胆固醇代谢中起雌激素激动剂的作用，而在乳腺和子宫起雌激素拈抗剂的作用：本文研究雷洛昔芬是否具有雌激素激动剂作用，是否能预防冠状动脉粥样硬化，并与传统的结合雌激素治疗的疗效相比较。卵巢切除（即手术绝经）的短尾猴，喂食会导致冠状动脉粥样硬化的食物，然后分别以安慰剂、雷洛昔芬每日1mg、     

Clinical Features of Crohn''s Disease in Ireland

Irish men and women are at equal risk of developing Crohn's disease. Age at diagnosis (12--mean 30.5-75 yr) and duration of symptoms before diagnosis (1--mean 35.7-444 months) are similar to those for Crohn's disease in other countries. The proportion of patients with macroscopic involvement of the large bowel at diagnosis (68%) is increasing and this is probably a true increase. At the same time the incidence of perianal disease is probably decreasing. Extraintestinal manifestations probably occur more frequently than previously recognized. Crohn's disease and psoriasis, which occurred in 7% of the patients, are probably associated disorders.     

中国与澳大利亚老年冠心病患者左冠状动脉病变特点的对比研究

目的探讨中国南京和澳大利亚悉尼地区的老年冠心病患者左冠状动脉病变是否存在种族和性别差异。方法经冠状动脉造影确诊的冠心病患者,年龄≥60岁,中国南京地区黄种人入选1442例(男性72.0%)为中国组,澳大利亚悉尼当地白种人同期入选1309例(男性65.6%)为澳大利亚组。从左冠状动脉病变率和Gensini积分,左前降支(LAD)和左回旋支(LCX)各段及主要分支病变率及狭窄程度进行比较。结果2组男性患者左冠状动脉病变率显著高于同组女性(P<0.05),但2组患者左冠状动脉的Gensini积分无显著的性别差异(P>0.05)。中国组LAD和LCX近中段的病变率以及LAD和LCX各段及分支(除LCX远段外)的狭窄程度均显著高于澳大利亚组(P<0.001)。结论中国组与澳大利亚组在冠心病危险因素、左冠状动脉病变的分布、狭窄程度和Gensini积分方面存在种族差异。中国组较澳大利亚组具有更严重的左冠状动脉病变,而且没有明显的性别差异。