Targeting PCNA with Peptide Mimetics for Therapeutic Purposes

Proliferating cell nuclear antigen (PCNA) is an excellent inhibition target to shut down highly proliferative cells and thereby develop a broad-spectrum cancer therapeutic. It interacts with a wide variety of proteins through a conserved motif referred to as the PCNA-interacting protein (PIP) box. There is large sequence diversity between high-affinity PCNA binding partners, but with conservation of the binding structure—a well-defined 3₁₀-helix. Herein, all current PIP-box peptides crystallised with human PCNA are collated to reveal common trends between binding structure and affinity. Key intra- and intermolecular hydrogen-bonding networks that stabilise the 3₁₀-helix of PIP-box partners are highlighted and related back to the canonical PIP-box motif. High correlation with the canonical PIP-box sequence does not directly afford high affinity. Instead, we summarise key interactions that stabilise the binding structure that leads to enhanced PCNA binding affinity. These interactions also implicate the “non-conserved” residues within the PIP-box that have previously been overlooked. Such insights will allow a more directed approach to develop therapeutic PCNA inhibitors.     

可溶性人类白细胞抗原G对丙型肝炎初治患者标准化治疗疗效的影响

目的: 探讨可溶性人类白细胞抗原G（sHLA-G）对慢性丙型肝炎（CHC）患者聚乙二醇干扰素联合利巴韦林抗病毒治疗疗效的影响。方法: 选择2013年10月至2015年10月就诊的63例CHC患者,分别采用基因芯片法、RT-PCR法和ELISA方法检测丙型肝炎病毒（HCV）基因型、HCV RNA和sHLA-G。所有患者接受聚乙二醇干扰素皮下注射,联合口服利巴韦林抗病毒治疗。分析获得持续病毒学应答（SVR）的影响因素。结果: SVR组女性和非基因1型比例均显著高于非持续病毒学应答（NSVR）组（女性：70.59% vs. 44.83%,χ2=4.285;非基因1型：82.76% vs. 55.88%,χ2=5.217,P均<0.05）,其余基线指标均无统计学差异（P均>0.05）。NSVR组患者治疗前血浆sHLA-G水平显著高于SVR组［1.85(1.49-16.00) ng/L vs. 1.53(1.36-2.80) ng/L;U=329.00,P<0.05］。经过多变量logistic回归分析,发现sHLA-G和HCV基因型是与治疗结局相关的独立影响因子,Exp(B)（95%CI）分别为0.922（0.868-0.978）、14.204（1.898-106.289）。结论: sHLA-G对丙型肝炎初治患者标准化治疗疗效有重要影响,特别是低水平者更容易获得持续病毒学应答。     

HuR and TIA1/TIAL1 Are Involved in Regulation of Alternative Splicing of SIRT1 Pre-mRNA

SIRT1 is a pleiotropic protein that plays critical and multifunctional roles in metabolism, senescence, longevity, stress-responses, and cancer, and has become an important therapeutic target across a range of diseases. Recent research demonstrated that SIRT1 pre-mRNA undergoes alternative splicing to produce different isoforms, such as SIRT1 full-length and SIRT1-ΔExon8 variants. Previous studies revealed these SIRT1 mRNA splice variants convey different characteristics and functions to the protein, which may in turn explain the multifunctional roles of SIRT1. However, the mechanisms underlying the regulation of SIRT1 alternative splicing remain to be elucidated. Our objective is to search for new pathways that regulate of SIRT1 alternative splicing. Here we describe experiments showing that HuR and TIA1/TIAL1, two kinds of RNA-binding proteins, were involved in the regulation of alternative splicing of SIRT1 pre-mRNA under normal and stress circumstances: HuR increased SIRT1-ΔExon8 by promoting SIRT1 exon 8 exclusion, whereas TIA1/TIAL1 inhibition of the exon 8 exclusion led to a decrease in SIRT1-ΔExon8 mRNA levels. This study provides novel insight into how the alternative splicing of SIRT1 pre-mRNA is regulated, which has fundamental implications for understanding the critical and multifunctional roles of SIRT1.     

前列腺特异性膜抗原(PSMA)的概况

近年来,前列腺癌特异性的分子标志物——前列腺特异性膜抗原（PSMA）受到国内外众多学者的关注。主要综述了前列腺特异性膜抗原的结构性质以及其在前列腺癌治疗中的应用。     

Lewis (y) Antigen Overexpression Increases the Expression of MMP-2 and MMP-9 and Invasion of Human Ovarian Cancer Cells

Lewis (y) antigen is a difucosylated oligosaccharide present on the plasma membrane, and its overexpression is frequently found in human cancers and has been shown to be associated with poor prognosis. Our previous studies have shown that Lewis (y) antigen plays a positive role in the process of invasion and metastasis of ovarian cancer cells. However, the mechanisms by which Lewis (y) antigen enhances the invasion and tumor metastasis are still unknown. In this study, we established a stable cell line constitutively expressing Lewis (y) antigen (RMG-1-hFUT) by transfecting the cDNA encoding part of the human α1,2-fucosyltransferase (α1,2-FUT) gene into the ovarian cancer cell line RMG-1, and investigated whether Lewis (y) antigen regulates the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9, and tissue inhibitors of metalloproteinases (TIMP-1) and TIMP-2. We found that RMG-1-hFUT cells exhibited higher invasive capacities than their control cells. In addition, expression of TIMP-1 and TIMP-2 was down-regulated and expression of MMP-2 and MMP-9 was up-regulated. Anti-Lewis (y) antigen antibody treatment significantly reversed the expression of TIMP-1, TIMP-2, MMP-2 and MMP-9. Taken together, we provide the first evidence that down-regulation of TIMP-1 and TIMP-2 and up-regulation of MMP-2 and MMP-9 represents one of the mechanisms by which Lewis (y) antigen promotes cell invasion.     

Integration of PEGylation and refolding for renaturation of recombinant proteins from insoluble aggregates produced in bacteria—Application to a single-chain Fv fragment

The conjugation of polyethylene glycol (PEGylation) with downsized compact antibodies is an effective method for overcoming the problem of rapid elimination of the compact antibodies from the body. We integrated site-specific PEGylation with the refolding of a single-chain Fv (scFv) of humanized monoclonal antibody 528 with affinity for the epidermal growth factor receptor, to prepare active PEGylated scFv from insoluble aggregates produced in an Escherichiacoli expression system. The insertion of a cysteine residue at the C-terminus of scFv to serve as the conjugation site for PEG led to the formation of highly multimeric scFv during the refolding process; however, PEGylation after refolding drastically dispersed the multimer into monomeric active scFv fragments. Further, the PEGylation of partially refolded scFv during the refolding process improved the PEGylation efficiency and suppressed the formation of highly multimeric scFv; consequently, monomeric active scFv fragments were obtained directly from the insoluble aggregates in E. coli. We show that in vitro refolding of PEGylated scFv should be useful for improving downstream processing performance in the production of clinically useful small antibodies from insoluble fractions.     

靶向PSMA放射性小分子药物研究进展

前列腺癌(PCa)是男性死亡的常见诱因,严重危害着人们的生命健康。随着靶向前列腺特异性膜抗原（PSMA）的放射性药物在PET/CT和SPECT/CT中的应用,前列腺癌诊断的灵敏度与精确度得到了有效提高。本文首先对靶向PSMA小分子药物的核心结构单元进行介绍,然后重点介绍基于脲基发展而来的靶向PSMA放射性药物（放射性核素包括：⁶⁸Ga、¹⁸F、¹¹C、^99mTc、⁶⁴Cu、¹²³I、¹²⁵I、¹³¹I、¹⁷⁷Lu、²²⁵Ac、²¹³Bi和²¹²Pb等）,以及在前列腺癌中的诊断与治疗研究进展,最后对该研究领域进行总结与展望。     

EV71抗原BA-ELISA检测方法的建立及应用

目的建立EV71抗原生物素-亲和素酶联免疫(BA-ELISA)检测方法,并进行验证及初步应用。方法以抗EV71抗体为包被抗体,利用生物素-亲和素系统建立双抗体夹心ELISA法,并对其灵敏度、特异性、准确性及精密性进行验证。采用该方法检测组织培养及临床样品中EV71抗原的含量。结果所建立的BA-ELISA法在EV71蛋白含量625～156.25ng/ml之间线性关系最佳,R2达0.9976,灵敏度为78.125～156.25ng;与包括CoxA16在内的42种肠道病毒及相关病毒均无交叉反应;检测10份EV71阳性样品和10份阴性样品,结果符合率均为100%;检测EV71原液和高、中浓度样品的变异系数分别为3.09%、6.69%和6.43%;可检出约103～104CCID50的活病毒及手足口病患者的大便悬液和部分咽拭子悬液中的病毒。结论用生物素标记EV71抗体与亲和素系统建立的双抗体夹心ELISA法具有较高的特异性、灵敏度、准确性和精密性,为临床检验及抗原分析提供了参考。