既往疾病史和胆道癌关系的全人群病例对照研究

目的　研究分析既往疾病史和胆道癌 (包括胆囊癌、肝外胆管癌和壶腹部癌 )的关系。方法　自 1997年 6月～ 2 0 0 1年 5月 ,在上海市区开展了一项大规模的基于全人群的胆道癌的病例对照研究 ,共收集、调查了 6 6 4例胆道癌新病例和 894例人群对照。结果　研究发现既往有胆囊炎疾病史者患胆囊癌、肝外胆管癌的危险性升高 ,调整的比数比分别为 2 .2 (95 %CI =1.3～ 3.6 )和 1.9(95 %CI=1.0～ 3.3)。糖尿病患者患胆囊癌的危险性增加 ,调整的比数比为 1.5 (95 %CI=0 .9～ 2 .5 ) ,在非胆结石者中调整的比数比为 2 .0 (95 %CI=0 .9～ 4 .5 ) ;此外 ,研究还发现肝硬化者患肝外胆管癌的危险性明显增加 ,调整的比数比为 3.0 (95 %CI=1.0～ 9.1) ,在非胆结石者中调整的比数比为 4 .9(95 %CI=1.2～ 19.8)。结论　该项研究为论证胆囊炎症增加患胆道癌的危险性提供了依据 ,研究还提示糖尿病和肝硬化分别提高患胆囊癌和肝外胆管癌的危险性。     

Notch induces human T-cell receptor γδ+ thymocytes to differentiate along a parallel, highly proliferative and bipotent CD4 CD8 double-positive pathway

In wild-type mice, T-cell receptor (TCR) γδ(+) cells differentiate along a CD4 CD8 double-negative (DN) pathway whereas TCRαβ(+) cells differentiate along the double-positive (DP) pathway. In the human postnatal thymus (PNT), DN, DP and single-positive (SP) TCRγδ(+) populations are present. Here, the precursor-progeny relationship of the various PNT TCRγδ(+) populations was studied and the role of the DP TCRγδ(+) population during T-cell differentiation was elucidated. We demonstrate that human TCRγδ(+) cells differentiate along two pathways downstream from an immature CD1(+) DN TCRγδ(+) precursor: a Notch-independent DN pathway generating mature DN and CD8αα SP TCRγδ(+) cells, and a Notch-dependent, highly proliferative DP pathway generating immature CD4 SP and subsequently DP TCRγδ(+) populations. DP TCRγδ(+) cells are actively rearranging the TCRα locus, and differentiate to TCR(-) DP cells, to CD8αβ SP TCRγδ(+) cells and to TCRαβ(+) cells. Finally, we show that the γδ subset of T-cell acute lymphoblastic leukemias (T-ALL) consists mainly of CD4 SP or DP phenotypes carrying significantly more activating Notch mutations than DN T-ALL. The latter suggests that activating Notch mutations in TCRγδ(+) thymocytes induce proliferation and differentiation along the DP pathway in vivo.     

Age- and gender-specific risk of death after first hospitalization for heart failure

Background  

Hospitalization for heart failure (HF) is associated with high-in-hospital and short- and long-term post discharge mortality. Age and gender are important predictors of mortality in hospitalized HF patients. However, studies assessing short- and long-term risk of death stratified by age and gender are scarce.     

A restricted clonal T-cell receptor αβ repertoire in Sézary syndrome is indicative of superantigenic stimulation

Background Sézary syndrome (SS) is a cutaneous T‐cell lymphoma characterized by erythroderma, lymphadenopathy and malignant clonal T cells in the skin, lymph nodes and peripheral blood. A role for superantigens in the pathogenesis of SS has been postulated before. Objectives To investigate a putative involvement of chronic (super‐)antigenic stimulation in driving T‐cell expansion in SS. Methods Antigenic specificity of the T‐cell receptor (TCR) was assayed by molecular analysis of the TCRA (n = 11) and TCRB (n = 28) genes, followed by detailed in silico analysis. Results Sequence analysis of clonally rearranged TCRB genes showed over‐representation of Vβ8, Vβ13, Vβ17, Vβ21 and Vβ22, and under‐representation of Vβ2 and Jβ1.1 when compared with healthy controls. No similarity was detected in amino acid motifs of the complementarity determining region 3 (CDR3). Analysis of TCRA rearrangements showed that there was no common Vα or Jα gene usage, and that TCRA CDR3 amino acid motifs were not highly similar. Conclusions The lack of clear stereotypic TCRA and TCRB CDR3 amino acid motifs would argue against involvement of a single common antigen in the pathogenesis of SS. Nevertheless, the skewing of Vβ and Jβ gene usage does seem to point to a restricted TCR repertoire, possibly as a result of superantigenic selection prior to neoplastic transformation.     

Familial aggregation of malignant mesothelioma in former workers and residents of Wittenoom,Western Australia

Clustering of cases of malignant mesothelioma within families has often been observed, but disentangling genetic and exposure effects has not been done. Former workers and residents exposed to crocidolite at Wittenoom, Western Australia, where many families shared exposure to asbestos, have had high rates of mesothelioma. Our study aimed to estimate the additional risk of mesothelioma in relatives, after allowance for common exposure to crocidolite. More than 11,000 former asbestos workers and residents from Wittenoom have been followed up in cancer and death registries. Levels of exposure for all members of the Wittenoom cohorts have been estimated previously. Relationships between family members of all mesothelioma cases were established from questionnaires, birth and death certificates. Expected numbers of cases of mesothelioma were estimated by fitting a Weibull survival model to all data, based on time from first asbestos exposure, duration and intensity of exposure and age. For each family group, the earliest case was considered the index case. Predicted risk was estimated for each subject from the time of diagnosis of the index case. Familial risk ratios were estimated by dividing observed cases by the sum of risks of all same degree relatives of index cases. There were 369 family groups with at least one case of mesothelioma and a further 25 cases of mesothelioma among relatives in the same families, with 12.9 expected. The risk ratio for blood relatives was 1.9 (95% confidence interval [CI] = 1.3–2.9, p = 0.002). These findings suggest an important, but not large, genetic component in mesothelioma, similar to many other cancers.     

Dependence of nucleotide substitutions on Ung2, Msh2, and PCNA-Ub during somatic hypermutation

During somatic hypermutation (SHM), B cells introduce mutations into their immunoglobulin genes to generate high affinity antibodies. Current models suggest a separation in the generation of G/C transversions by the Ung2-dependent pathway and the generation of A/T mutations by the Msh2/ubiquitinated proliferating cell nuclear antigen (PCNA-Ub)–dependent pathway. It is currently unknown whether these pathways compete to initiate mutagenesis and whether PCNA-Ub functions downstream of Ung2. Furthermore, these models do not explain why mice lacking Msh2 have a more than twofold reduction in the total mutation frequency. Our data indicate that PCNA-Ub is required for A/T mutagenesis downstream of both Msh2 and Ung2. Furthermore, we provide evidence that both pathways are noncompetitive to initiate mutagenesis and even collaborate to generate half of all G/C transversions. These findings significantly add to our understanding of SHM and necessitate an update of present SHM models.To generate high affinity antibodies, germinal center (GC) B cells are enabled to introduce point mutations into the variable region of their rearranged Ig genes. This process of somatic hypermutation (SHM) occurs at an astonishing rate of one per thousand bases per generation, six orders of magnitude greater than spontaneous mutagenesis (Di Noia and Neuberger, 2007). SHM is initiated by the activation-induced cytidine deaminase (AID), an enzyme found to be differentially expressed in B cells of the GC (Muramatsu et al., 2000). AID deaminates C to U within single-stranded DNA, and targets both DNA strands in the variable and switch regions of Ig genes. To establish point mutations at and around the U, three alternative pathways can handle this initial lesion (Fig. 1). (a) Replication across a U instructs a template T to DNA polymerases and generates G/C to A/T transitions (Rada et al., 2004; Shen et al., 2006). (b) The U can be excised from the DNA backbone by the base excision repair (BER) protein Ung2, and an abasic or apyrimidinic (AP) site is generated, causing replicative DNA polymerases to stall. To continue replication, specialized translesion synthesis (TLS) polymerases can be recruited, enabling a direct replicative bypass of AP sites. As AP sites are noninstructive, these TLS polymerases generate G/C transversions and may contribute to G/C transitions (Ung2-dependent SHM). Accordingly, Ung mutant B cells lack most G/C transversions (Rada et al., 2002). (c) Alternatively, the U can be recognized as a U:G mismatch by the mismatch repair complex Msh2–Msh6, resulting in Exo-1 activation and the formation of a single-stranded gap around the initial mismatch. Interestingly, Msh2-, Msh6-, and Exo-1–deficient B cells lack 80–90% of all A/T mutations, suggesting that the gap-filling process is executed by TLS polymerases predominantly generating A/T mutations (Msh2-dependent SHM; Rada et al., 1998; Wiesendanger et al., 2000; Bardwell et al., 2004). As a significant fraction of A/T mutations (10–20%) are found in Msh2-deficient GC B cells but not in Ung2/Msh2 double-deficient GC B cells, Ung2-dependent mutagenesis generates the described fraction of A/T mutations (Rada et al., 2004). Whether Ung2-dependent A/T mutations are generated during long-patch BER (i.e., within the strand containing the AP site) or, alternatively, during the extension phase of TLS across the AP site is currently unknown. In summary, these data suggest a specific role of these pathways in recruiting and activating selective TLS polymerases to establish defined mutations. The combination of these pathways enables hypermutating B cells to generate the entire spectrum of nucleotide substitutions.Open in a separate windowFigure 1.Current model: pathways of SHM downstream of AID. The three pathways: (a) replication across U, (b) Ung2-dependent SHM, and (c) Msh2-dependent SHM. Known and unknown (?) polymerases involved in the generation of specific mutations are indicated. TS, transitions; TV, transversions.In contrast to replicative DNA polymerases, TLS polymerases lack proofreading activity. The capacity of TLS polymerases to accommodate non–Watson–Crick base pairs within their catalytic center is beneficial regarding the accurate replication across modified bases, such as UV-C–induced cyclic pyrimidine dimers by polymerase η. However, TLS polymerases are highly mutagenic when replicating across undamaged DNA and defined lesions such as AP sites (Prakash et al., 2005; Jansen et al., 2007). Because each polymerase displays its own mutagenic signature, alterations in the mutation spectrum can often be attributed retrospectively to the absence of, or failure in activating, specific polymerases. The Y family of DNA polymerases comprises four members, of which at least polymerase η, Rev1, and to some degree polymerase κ are implicated in SHM. Rev1-deficient B cells display reduced frequencies of G/C to C/G transversions (Jansen et al., 2006; Ross and Sale, 2006), suggesting that Rev1 functions downstream of Ung2. In agreement, Rev1 is an effective cytidyl transferase when bypassing abasic sites in vitro (Nelson et al., 1996). In contrast, polymerase η is ineffective in handling abasic sites (Haracska et al., 2001) and preferentially inserts mismatched nucleotides opposite template T (Rogozin et al., 2001). Consistent with these in vitro data, the mutation spectra of polymerase η–deficient B cells from humans and mice lack a significant fraction of A/T mutations, suggesting polymerase η to be used mainly downstream of Msh2 (Zeng et al., 2001; Delbos et al., 2005; Martomo et al., 2005). In addition to its role downstream of Msh2, polymerase η was responsible for the remaining A/T mutations downstream of Ung2, as shown in Msh2-deficient mice (Delbos et al., 2007). Although the lack of polymerase κ had no effect on SHM (Schenten et al., 2002), polymerase κ was found to generate A/T mutations in case of polymerase η deficiency (Faili et al., 2009). Thus, polymerase κ can substitute polymerase η, whereas Rev1 cannot, as revealed by the normal generation of G to C transversions in polymerase η–deficient mice.The question remains how and when these error-prone polymerases become used to establish specific nucleotide substitutions. During replication, the DNA sliding clamp proliferating cell nuclear antigen (PCNA) functions as a critical processivity factor by tethering the DNA polymerases to the DNA template. Studies in yeast and subsequently in mammalian cells revealed an important role for site-specific monoubiquination of PCNA at lysine 164 (ubiquitinated PCNA [PCNA-Ub]) in recruiting and activating TLS polymerases upon replication fork stalling (Hoege et al., 2002; Stelter and Ulrich, 2003; Kannouche et al., 2004). In mice and chicken DT40 B cells homozygous for a PCNA^K164R mutation, we and others recently demonstrated a critical role for PCNA-Ub in SHM (Arakawa et al., 2006; Langerak et al., 2007; Roa et al., 2008). As shown in memory B cells of PCNA^K164R knockin mice, the failure to modify PCNA at lysine 164 caused a 10-fold decrease in mutations at template A/T, normally accounting for 50% of all mutations in WT mice. This decrease was accompanied by an overall 25% reduction in the mutation frequency. The lack of A/T mutations indicated a role for PCNA-Ub downstream of Msh2. In strong contrast, data from DT40 cells suggested a role for PCNA-Ub in generating the vast majority of G/C transversions, placing PCNA-Ub downstream of Ung2.To dissect the role of PCNA-Ub in Ung2- and Msh2-dependent SHM, we intercrossed the PCNA^K164R knockin strain of mice with mice deficient for Ung or Msh2. Comparing the efficacy of Ung2- and Msh2-dependent mutagenesis revealed that both pathways strongly depend on PCNA-Ub to generate mutations at template A/T but not at G/C. Furthermore, in addition to its role in the generation of A/T mutations, we identified a previously unknown role for Msh2 in generating 50% of all G/C transversions. Finally, we provide evidence for the employment of Ung2 and Msh2 in a noncompetitive manner in processing uracils downstream of AID, supporting the idea of a temporal separation of these pathways (Weill and Reynaud, 2008).     

Concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia in a 2-year-old child

We present a case of a 2-year-old girl, who developed concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia (JMML). JMML was initially not recognized because of predominant B-cell proliferation. The activating N-RAS mutation was retrospectively already detectable at this early stage. Our findings support the hypothesis that EBV may contribute to JMML pathogenesis by stimulating pre-existing malignant clones. However, such stimulation of leukemic clone does not require the direct incorporation of the virus into myeloid progenitors. Most probably a cytokine burst resulting from EBV infection allows expansion of pre-existing malignant myeloid progenitors. Further studies are required to delineate exact mechanisms of EBV-related promotion of the JMML clone.     

Support of human cord blood progenitor cells on human stromal cell lines transformed by SV40 large T antigen under the influence of an inducible (metallothionein) promoter

We describe the development of a human bone marrow (BM) culture system which allows study of the interaction of stromal cell lines (SCL) and highly purified hematopoietic progenitor cells. Normal BM stromal cells were electroporated with a plasmid containing the simian virus 40 (SV40) large T antigen (SV40 T Ag) under the control of a synthetic metallothionein promoter (MT4); this construct is designated MT4 SV40 T Ag. SCL in which the rate of proliferation could be controlled by altering the zinc (Zn) concentration were characterized, demonstrating that the SCL were heterogeneous with respect to G-CSF and GM-CSF production. Suppression of SCL proliferation on removal of Zn made it possible to use these lines in coculture with purified CD34+ progenitor cells from umbilical cord blood. The ability to control proliferation of SCL has allowed us to maintain the survival and expansion of colony- forming cells in culture for up to 2 months. These lines have enabled us to test for stromal cell characteristics at a clonal level and provided us with a tool to analyze the events leading to lineage commitment and hematopoietic differentiation, as demonstrated by suppression of hematopoiesis by an antibody directed against the c-kit molecule.