A New Model for Predicting Non-Sentinel Lymph Node Status in Chinese Sentinel Lymph Node Positive Breast Cancer Patients

Background

Our goal is to validate the Memorial Sloan-Kettering Cancer Center (MSKCC) nomogram and Stanford Online Calculator (SOC) for predicting non-sentinel lymph node (NSLN) metastasis in Chinese patients, and develop a new model for better prediction of NSLN metastasis.

Methods

The MSKCC nomogram and SOC were used to calculate the probability of NSLN metastasis in 120 breast cancer patients. Univariate and multivariate analyses were performed to evaluate the relationship between NSLN metastasis and clinicopathologic factors, using the medical records of the first 80 breast cancer patients. A new model predicting NSLN metastasis was developed from the 80 patients.

Results

The MSKCC and SOC predicted NSLN metastasis in a series of 120 patients with an area under the receiver operating characteristic curve (AUC) of 0.688 and 0.734, respectively. For predicted probability cut-off points of 10%, the false-negative (FN) rates of MSKCC and SOC were both 4.4%, and the negative predictive value (NPV) 75.0% and 90.0%, respectively. Tumor size, Kiss-1 expression in positive SLN and size of SLN metastasis were independently associated with NSLN metastasis (p<0.05). A new model (Peking University People''s Hospital, PKUPH) was developed using these three variables. The MSKCC, SOC and PKUPH predicted NSLN metastasis in the second 40 patients from the 120 patients with an AUC of 0.624, 0.679 and 0.795, respectively.

Conclusion

MSKCC nomogram and SOC did not perform as well as their original researches in Chinese patients. As a new predictor, Kiss-1 expression in positive SLN correlated independently with NSLN metastasis strongly. PKUPH model achieved higher accuracy than MSKCC and SOC in predicting NSLN metastasis in Chinese patients.     

The lock-washer: a reconciliation of the RIG-I activation models

RIG-I belongs to a type of intracellular pattern recognition receptors involved in the recognition of viral RNA by the innate immune system. A report by Peisley et al. published in Nature provides the crystal structure of human RIG-I revealing a tetrameric architecture of the RIG-I 2-CARD domain bound by three K63-linked ubiquitin chains, uncovering its activation mechanism for downstream signaling.The recognition of microbial-derived nucleic acids and the correct and specific activation of the molecular machinery governing the mammalian immune response are paramount to host survival during viral infection. Viral RNA represents a key trigger for the activation and mobilization of a series of pattern recognition receptors (PRRs) such as the Toll-like receptor (TLR) and retinoic acid-inducible gene 1 (RIG-I)-like receptor (RLR) families. While the TLRs are restricted to the cell surface or inside endosomal compartments, the RLRs are present in the cytosol and act as the key sentinels of actively invading and replicating viruses.The RLR family of receptors, RIG-I and Melanoma Differentiation-Associated protein 5 (MDA-5), are characterised by 3 distinct signaling domains critical for viral RNA recognition and response. The C-terminal repressor domain and the internal ATPase-containing DExD/H-box helicase domain of RIG-I function together to facilitate binding of viral dsRNA which contain either a 5′-ppp motif or 5′ blunt-end base-paired RNA with a triphosphate motif, moieties absent on self-nucleic acids¹. Upon viral RNA ligation, two N-terminal caspase activation and recruitment domains (CARD), known as 2-CARD, on RIG-I propagate signal transduction via interactions with mitochondrial antiviral signaling protein (MAVS)². Recent molecular and structural studies have elucidated the mechanisms by which RLR-activated MAVS mediates the antiviral response. During RIG-I signaling, MAVS forms large multimeric prion-like filaments on the mitochondrial membrane which are essential for RIG-I-mediated type I interferon (IFN) production³. Such functional aggregates are capable of recruiting key downstream signaling components such as members of TNF receptor associated factors (TRAF) family, resulting in the activation of the MAPKs, the NF-κB pathway and interferon regulatory factor 3/7 (IRF3/7) and consequently culminating in the upregulation of protective IFNs and pro-inflammatory cytokines. Viral infection is sufficient to convert nearly all endogenous detectable MAVS to functionally active aggregates, and interestingly this phenomenon can be recapitulated in vitro using only mitochondria, RIG-I and K63-linked ubiquitin chains, underscoring the functional importance of polyubiquitination events during RIG-I signaling⁴.In contrast to the well-documented and -accepted paradigm of MAVS activation, the model of RIG-I-mediated activation has remained incompletely understood. The classical model holds that RIG-I remains in an auto-repressed state in the absence of ligand. Upon viral recognition, the E3 ubiquitin ligase tripartite motif 25 (TRIM25) binds to the 2-CARD domain of RIG-I, resulting in the covalent conjugation of K63-linked polyubiquitin chains to induce a conformation change in the receptor and facilitate a “release” of the 2-CARD domain for MAVS interaction and activation⁵. However, this simple release model of the 2-CARD domain does not reconcile with recent compelling reports that RIG-I can act as a receptor for unanchored, non-covalently attached ubiquitin chains and that polyubiquitination of RIG-I induces the oligomerization of a heterotetrameric complex consisting of 4 RIG-I and 4 K63-ubiqutin chain molecules^6,7. In addition, although K63-ubiquitination is essential for the signaling potential of isolated 2-CARD molecules, full-length RIG-I can form filaments around the ends of dsRNA molecules, allowing 2-CARD regions of RIG-I molecules to come into close proximity to each other and facilitate MAVS aggregation in an ubiquitin-independent manner⁸.Although such conflicting reports seem to propose vastly different models of RIG-I activation, an elegent study published in Nature by Peisley et al.⁹ uses biochemical and structural studies to reconcile the different models and they finally offer a unified understanding of RIG-I receptor activation. They resolved the crystal structure of human RIG-I 2-CARD in complex with K63-ubiquitin at 3.7 Å. The structure revealed the tetrameric architecture of RIG-I 2-CARD bound by three K63 ubiquitin chains (Figure 1). Crystallization and structure determination reveal that four 2-CARD subunits form a tetrameric helical assembly, termed the “lock washer”, with the two ends displaced by half the thickness of 2-CARD.Open in a separate windowFigure 1A model of RIG-I-mediated antiviral response.Two key questions arise from the RIG-I 2-CARD structure. First, how does the tetrameric architecture of RIG-I serve as a platform to activate downstream signaling? The CARD domain belongs to the death domain (DD) superfamily, members of which have a similar three-dimensional fold. The structures of other DD oligomers such as Myddosome, PIDDosome, or FAS-FADD complex have recently been resolved. The assembly of DD oligomers is usually mediated at six surface areas, with the helical oligomeric structure of upstream signaling molecules serving as a scaffold to assemble the downstream DD oligomers through helical extension. In the current study, the authors show that the assembly and stability of the tetramer and its IFN-β signaling potential are dependent on several intermolecular and intramolecular CARD interactions by generating mutants on different interaction surfaces and analyzing their tetramer formation and IFN-β induction abilities. MAVS filament formation assays indicate that the helical tetrameric structure of RIG-I 2-CARD serves as the platform for MAVS-CARD filament assembly, with the top surface of the second CARD as the primary site for MAVS recruitment⁹.The second pertinent question addressed is how the interaction between ubiquitin and 2-CARD contributes to downstream signaling? Unlike other DD oligomers, tetramer formation of isolated RIG-I 2-CARD requires K63-linked ubiquitin chains. The structure predicts that longer ubiquitin chains might wrap around the 2-CARD tetramer at 1:4 or 2:4 molar ratios to stabilize the 2-CARD tetramerization. Another key problem addressed in this study is the relationship between the covalent conjugation and non-covalent binding of K63-ubiquitin in stabilizing 2-CARD tetramers during RIG-I signaling. The authors challenge previous publications on the significance of 6 lysine (K) residues in both covalent conjugation and non-covalent K63-ubiquitin binding.The authors show that only K6 is covalently conjugated with K63-ubiquitin chains and that non-covalent binding of K63-ubiquitin to 2-CARD can induce a further stabilization of the tetramer complex. RIG-I filament formation on dsRNA with appropriate length can also compensate for the requirement of both covalent and non-covalent K63-ubiquitin binding. Thus they arrive at the conclusion that these three mechanisms might act synergistically for signal activation. This compensatory mechanism could guarantee the detection of foreign pathogen RNA in case of the absence of one or two of the mechanisms or may allow an amplification of the signal potential. One could speculate that such functional redundancy in the initiation stage of signal activation may be a common theme in other innate immunity pathways.The significance of this study lies in the resolution of the structural basis of the activated RIG-I 2-CARD tetramer and its initiation of MAVS aggregation and filament formation — the first elements of the dsRNA sensing signaling cascade that lead to production of type I IFNs and pro-inflammatory cytokines. It provides another detailed example of DD oligomers and adds to the growing realization of a common role of oligomeric molecular scaffolds in mediating innate immune signaling. Such exciting findings will no doubt instigate further study into the exact molecular interactions and mechanisms controlling dsRNA sensing. For example, the authors use a crystallized K115A/R117A 2-CARD double mutant for structural analysis; although it retains the ability to tetramerize with K63-ubiquitin and activate type I IFNs, the structure might still not be consistent with the wild-type 2-CARD and this may warrant further investigation. Furthermore, whether the RIG-I signaling activation mechanism that derived from this structure could be generalized and applied to other CARD domain receptors such as MDA-5, NOD1, NOD2, IPAF and NLRP1 will require further investigation. By utilizing advanced structural determination techniques coupled with sophisticated in vitro assays such as those described in this study, these questions will no doubt be addressed in the near future.     

Ultrastructural characterization of avian influenza A(H7N9) virus infecting humans in China

正Dear Editor,In March 2013,the first 3 cases of severe disease dueto a novel avian-origin influenza A(H7N9)virus weredetected in the Chinese provinces of Shanghai and Anhui(Gao R,et al.,2013).A total of 339 laboratory-confirmedcases with 100 deaths were reported until January 142014(WHO,2014).To the best of our knowledge,thisis the first time that human infection with the avian in-fluenza A H7N9 subtype has been detected.Prior to this     

乙型脑炎病毒可视化分型基因芯片的制备

目的:制备乙型脑炎病毒(JEV)可视化分型基因芯片。方法:根据JEV的基因组序列,应用生物学软件设计JEV分型引物及探针,制备其可视化分型基因芯片;用生物素标记的引物PCR扩增目的片段,并与固定于玻片上的探针杂交,加入链霉亲和素标记的纳米金,银增强实现可视化;进行特异性、灵敏性及重复性试验。结果:探针特异地与相应的标记目的基因片段杂交,并在芯片上呈现较强的阳性杂交信号;2号探针能特异性检出JEV,3、4号探针可分别对Ⅰ型和Ⅲ型JEV进行分型;芯片对JEV质粒检测的灵敏度达105拷贝/mL;以蓝耳病病毒等5种病毒为对照,芯片只对JEV响应,具有特异性;制备的基因芯片具有批间、批内重复性。结论:制备的基因芯片具有高特异性、灵敏性及重复性,可以快速、准确、高通量地对JEV进行可视化分型检测。     

Biochemical and biological properties of cortexillin III,a component of Dictyostelium DGAP1–cortexillin complexes

Cortexillins I–III are members of the α-actinin/spectrin subfamily of Dictyostelium calponin homology proteins. Unlike recombinant cortexillins I and II, which form homodimers as well as heterodimers in vitro, we find that recombinant cortexillin III is an unstable monomer but forms more stable heterodimers when coexpressed in Escherichia coli with cortexillin I or II. Expressed cortexillin III also forms heterodimers with both cortexillin I and II in vivo, and the heterodimers complex in vivo with DGAP1, a Dictyostelium GAP protein. Binding of cortexillin III to DGAP1 requires the presence of either cortexillin I or II; that is, cortexillin III binds to DGAP1 only as a heterodimer, and the heterodimers form in vivo in the absence of DGAP1. Expressed cortexillin III colocalizes with cortexillins I and II in the cortex of vegetative amoebae, the leading edge of motile cells, and the cleavage furrow of dividing cells. Colocalization of cortexillin III and F-actin may require the heterodimer/DGAP1 complex. Functionally, cortexillin III may be a negative regulator of cell growth, cytokinesis, pinocytosis, and phagocytosis, as all are enhanced in cortexillin III–null cells.     

Evaluation of an immune-privileged scaffold for In vivo implantation of tissue-engineered trachea

Forty tracheas were harvested from donor New Zealand rabbits. Thirty of the tracheas were randomly divided into four treatment groups corresponding to 4, 5, 6, or 7% NaClO₄ and one untreated group (n = 6 each group). Scanning electron microscopy distinctly revealed the cilium of epithelial cells in the fresh trachea. The internal surface of the trachea was rough in the 4% treatment group and smooth in the 5% treatment group, whereas the matrix was fractured in the 6% treatment group and highly fractured in the 7% treatment group. We observed that the number of nuclei in the cells of the 4, 5, 6, and 7% treatment groups decreased compared to the cells of the untreated group (p < 0.05). Although there was a significant decrease in maximum tensile strength, tensile strain at fracture and the elastic modulus (p < 0.05) with increasing concentrations of NaClO₄, the content of glycosaminoglycans (GAGs) did not significantly decline (p > 0.05) in the 5% treatment group. In addition, histopathological analysis showed that the fiber component and basement membrane of the matrix in the 5% treatment group were retained after optimal decellularization. Despite the preserved cartilage, in vitro immunohistochemical analysis revealed that the matrix did not show the presence of major histocompatibility complex (MHC) antigens. The remaining ten donor tracheas, which were divided into a positive control group and an optimal decellularized group, were used for allogeneic transplantation. Blood samples were taken regularly, and histologic examinations were performed at 30 days postimplantation, which showed no significant immune rejection. In conclusion, we surveyed the structural integrity through morphological observation and compared the biomechanical and immunogenic changes in the tracheal matrix under the different treatments. The optimal decellularized tracheal matrix with preserved cartilage, which was acquired via 5% NaClO4 treatment, exhibited structural integrity, antigen cell removal and immune privilege and would be suitable for use as a tissue-engineered trachea for in vivo transplantation in rabbit models.     

特异小干扰RNA敲除PLK1基因的表达

为研究特异小干扰RNA（siRNA）作用于大肠癌细胞株SW480中PLK1 (Polo-like kinase 1)基因表达的mRNA对该细胞分裂生长的影响,设计了对应于PLK1基因表达mRNA不同位点的10种特异siRNA,经化学合成后,用脂质体转染SW480细胞,实时定量PCR检测PLK1基因的表达,观察不同的siRNA作用强度,并计数细胞了解相应细胞的生长情况,western-blot观察PLK1表达蛋白的变化和流式细胞计数分析细胞周期改变。发现10种siRNA均可敲除PLK1基因表达的20 %以上,其中P1、P4和P9 3组敲除mRNA达80 ％以上,这3种siRNA及其混合物对PLK1基因mRNA的作用具有相应浓度效应,在25 nmol/L时达到最佳作用效果,而且相同浓度的混合物作用效果更好（超过95%）,PLK1表达蛋白质明显降低,细胞周期在G2期受到阻碍。72 h后的各种siRNA浓度下细胞生长变化与PLK1基因的mRNA水平变化相一致。结果表明化学合成的特异siRNA对SW480细胞中PLK1基因表达具有消除作用,混合物作用更强,在细胞水平上抑制了SW480细胞的分裂生长。