Optimizations of an ELISA-like high-throughput screening assay for the discovery of β-catenin/TCF4 interaction antagonists / 生物工程学报

In canonical Wnt/β-catenin signaling pathway, β-catenin/TCF4 (T-cell factor 4) interaction plays an important role in the pathogenesis and development of non-small cell lung cancer (NSCLC), and it is tightly associated with the proliferation, chemoresistance, recurrence and metastasis of NSCLC. Therefore, suppressing β-catenin/TCF4 interaction in Wnt/β-catenin signaling pathway would be a new therapeutic avenue against NSCLC metastasis. In this study, considering the principle of enzyme-linked immunosorbent assay (ELISA), an optimized high-throughput screening (HTS) assay was developed for the discovery of β-catenin/TCF4 interaction antagonists. Subsequently, this ELISA-like screening assay was performed using 2 μg/mL GST-TCF4 βBD and 0.5 μg/mL β-catenin, then a high Z' factor of 0.83 was achieved. A pilot screening of a natural product library using this ELISA-like screening assay identified plumbagin as a potential β-catenin/TCF4 interaction antagonist. Plumbagin remarkably inhibited the proliferation of A549, H1299, MCF7 and SW480 cell lines. More importantly, plumbagin significantly suppressed the β-catenin-responsive transcription in TOPFlash assay. In short, this newly developed ELISA-like screening assay will be vital for the rapid screening of novel Wnt inhibitors targeting β-catenin/TCF4 interaction, and this interaction is a potential anticancer target of plumbagin in vitro.

Prenatal ultrasonic diagnosis of umbilical cord ulcer: analysis of three cases and literature review / 中华围产医学杂志

Objective:To investigate the features, diagnostic value and clinical significance of prenatal ultrasound for umbilical cord ulcer (UCU).Methods:Ultrasonographic characteristics of three fetuses with UCU diagnosed at Guangzhou Women and Children's Medical Center from January 2014 to June 2020 were reviewed. Relevant articles published from January 1, 1990, to June 1, 2020, were retrieved from Wanfang, CNKI and PubMed databases and analyzed. Likelihood ratio, adjusted Chi-square test and Fisher's exact test were used to analyze the association between the pathological results and fetal outcomes. Results:(1) Among the three fetuses with UCU, two were complicated by upper gastrointestinal obstruction and one by intrauterine infection. Two of them survived and one died after birth. Prenatal ultrasound examination of the umbilical cord and amniotic cavity showed one case was normal, while the other two showing features such as flocculent hypoechoic sign around the umbilical cord, cloudy hyperechoic sign ejecting from the umbilical cord lesion in dynamic observation, exposed umbilical vessels and ribbon-like echo around the umbilical cord. (2) No reported case of UCU had been found in any publications in China. A total of 39 reported cases of UCU complicated by duodenal or jejunal obstruction were retrieved from English literature, among which intrauterine fetal death, neonatal death and live births accounted for 30.8% (12/39), 28.2% (11/39) and 41.0% (16/39), respectively. Six cases with intrauterine abnormalities detected by prenatal ultrasound survived after emergent cesarean section, showing a positive detection rate of 15.4% (6/39), of which three obtained a snapshot of umbilical cord bleeding and three were characterized by lamellar and linear echoes around the amniotic cavity or umbilical cord. Hemorrhagic amniotic fluid was observed in 66.7% (26/39) of the fetuses and decreased heart rate occurred in 35.9%(14/39). The site, number and pathological grade of UCU were not related to the pregnancy outcomes (all P>0.05). Conclusions:Prenatal ultrasound for detecting abnormalities in umbilical cord and amniotic cavity is of a certain value in the diagnosis of UCU. Lamellar and linear echoes around the umbilical cord may be the ultrasonographic characteristics of UCU. The real-time detection of UCU bleeding by prenatal ultrasound can provide direct evidence for timely clinical treatment.

Optimization of expression conditions and determination the proteolytic activity of codon-optimized SARS-CoV-2 main protease in Escherichia coli / 生物工程学报

The main protease (Mpro) of SARS-CoV-2 is a highly conserved and mutation-resistant coronaviral enzyme, which plays a pivotal role in viral replication, making it an ideal target for the development of novel broad-spectrum anti-coronaviral drugs. In this study, a codon-optimized Mpro gene was cloned into pET-21a and pET-28a expression vectors. The recombinant plasmids were transformed into E. coli Rosetta(DE3) competent cells and the expression conditions were optimized. The highly expressed recombinant proteins, Mpro and Mpro-28, were purified by HisTrapTM chelating column and its proteolytic activity was determined by a fluorescence resonance energy transfer (FRET) assay. The FRET assay showed that Mpro exhibits a desirable proteolytic activity (25 000 U/mg), with Km and kcat values of 11.68 μmol/L and 0.037/s, respectively. The specific activity of Mpro is 25 times that of Mpro-28, a fusion protein carrying a polyhistidine tag at the N and C termini, indicating additional residues at the N terminus of Mpro, but not at the C terminus, are detrimental to its proteolytic activity. The preparation of active SARS-CoV-2 Mpro through codon-optimization strategy might facilitate the development of the rapid screening assays for the discovery of broad-spectrum anti-coronaviral drugs targeting Mpro.

Mining Polo-Box domain of Polo-like kinase 1 as a new therapeutic target for cancer / 生物工程学报

Polo-like kinase 1 (Plk1) is widely regarded as one of the most promising targets for cancer therapy due to its essential role in cell division and tumor cell survival. At present, most Plk1 inhibitors have been developed based on kinase domain, some of which are in clinical trial. However, inhibitors targeting kinase domain face off-target effect and drug resistance owing to the conserved nature and the frequent mutations in the ATP-binding pocket. In addition to a highly conserved kinase domain, Plk1 also contains a unique Polo-Box domain (PBD), which is essential for Plk1's subcellular localization and mitotic functions. Inhibitors targeting Plk1 PBD show stronger selectivity and less drug resistance for cancer therapy. Therefore, Plk1 PBD is an attractive target for the development of anti-cancer agents. In this review, we will summarize the up-to date drug discovery for targeting Plk1 PBD, including the molecular structure and cellular functions of Plk1 PBD. Small-molecule inhibitors targeting Plk1 PBD not only provide an opportunity to specifically inhibit Plk1 activity for cancer treatment, but also unveil novel biological basis regarding the molecular recognition of Plk1 and its substrates.

Development of an ELISA-based high throughput screening method for novel anticancer agents targeting β-catenin/Lef1 interaction / 生物工程学报

To develop an enzyme-linked immunosorbent assay (ELISA)-based high throughput screening (HTS) method for β-catenin/Lef1 interaction antagonists screening, Escherichia coli Rosetta (DE3) competent cells were transformed with β-catenin-pET-30a(+) plasmid. β-catenin protein was expressed after induction and purified using affinity chromatography. The biological activity of purified β-catenin was further analyzed by GST Pulldown assay. The β-catenin/GST-Lef1 binding model was established using ELISA principle, and the ELISA-based HTS method was further optimized through determination of an optimal coated concentration of GST-Lef1 and working concentration of β-catenin. The results showed that β-catenin protein was successfully expressed and purified. The GST Pulldown assay demonstrated a perfect biological activity for purified β-catenin. Subsequently, the ELISA-based HTS method was performed using 10 μg/mL GST-Lef1 and 6 μg/mL β-catenin, with the Z factor of 0.76. Taken together, we have successfully developed a simple, robust and reliable ELISA-based HTS method for screening of novel Wnt inhibitors targeting β-catenin/Lef1 interaction.

Bacterial expression, preparation and identification of polyclonal antibody against Escherichia coli FtsZ / 生物工程学报

To prepare polyclonal antibody (PcAb) against Escherichia coli filamentous thermosensitive protein Z (Ec-FtsZ), the artificially synthesized gene fragment coding Ec-FtsZ was subcloned into pET-22b(+) plasmid, and Ec-FtsZ protein was expressed in E. coli BL21(DE3) cell under an optimal bacterial expression condition. Then Ec-FtsZ protein was purified by HisTrap affinity chromatography, and the GTPase (Guanosine triphosphatase) activity of purified Ec-FtsZ protein was further analyzed by malachite green assay. Subsequently, the purified Ec-FtsZ protein was used to immunize rat subcutaneously for preparation of anti-Ec-FtsZ PcAb. The results of enzyme-linked immunosorbent assay (ELISA), Western blotting analysis and immunofluorescence assay showed that the titer of PcAb was 1:256 000, and PcAb exhibited a perfect antigenic specificity against purified and endogenous Ec-FtsZ protein. All these data indicated that the anti-Ec-FtsZ PcAb is successfully prepared, which can be used for further cellular function study and biochemical analysis of Ec-FtsZ protein in vivo.

Preparation and identification of anti-human ICAM-1 scFv / 生物工程学报

To screen the specific anti-human intercellular adhesion molecule-1 (ICAM-1) single chain fragment variable (scFv) using phage display library technology and to identify its biological activity. P1 peptide was used as antigen, and the phage antibodies against human ICAM-1 antigen were panned by four binding-eluting-amplifying cycles using Tomlinson I+J phage display library. After four rounds of selective enrichment screening, the positive clones were determined by PCR, enzyme linked immunosorbent assay (ELISA)-based antigenic cross reaction and Dot blotting. Then the binding specificity and biological activity of purified scFv were identified by Western blotting, competitive ELISA and cell adhesion inhibition assay respectively. Furthermore, four positive clones were first panned through P1 peptide coated-ELISA assay, and then J-A1 was obtained and identified by PCR, ELISA-based antigenic cross reaction and Dot blotting, which could show a specific binding between P1 peptide and human ICAM-1 protein antigen. Subsequently, the purified scFv showed a satisfactory specificity and anti-adhesive activity in competitive ELISA and the cell adhesion inhibition assay. The specific anti-human ICAM-1 scFv was prepared successfully from Tomlinson I+J phage display library, which pave the way for further application of anti-human ICAM-1 scFv for inflammation diseases therapeutics.

Imaging of secondary damage in remote regions after focal cerebral infarction / 国际脑血管病杂志

After ischemic stroke, secondary damages such as neuron loss, gliosis, and axonal degeneration occur in the nonischemic remote brain regions that have synaptic connections with the primary infarction site.These secondary damages in the remote brain regions may affect the recovery of neurological function.Several advanced neuroimaging techniques have been used to detect these secondary damages.This article reviews the research progress in this field.

Clinical analysis of thrombolytic therapy with ischemic in-hospital stroke / 中国神经精神疾病杂志

Objective To analyze the clinical effects of thrombolytic therapy in patients with ischemic in-hos-pital stroke (IHS). Methods The clinical data were collected from patients with ischemic IHS in the last five years. The patients were divided into thrombolysis group and non-thrombolysis group, according to the use of recombinant tissue plasminogen activator (r-tPA) treatment. The clinical outcomes were measured by the modified Rankin scale (mRS) at discharge. Results There were a total of 121 patients in this study. There were 6 patients in thrombolysis group and 115 patients in the non-thrombolysis group, respectively. Six patients (100%) in the thrombolysis group achieved favor-able outcomes (mRS 0~2) at discharge whereas only 42 patients (36.5%) in the non-thrombolysis group achieved fa-vourable outcomes. The rate of favorable outcomes was significantly higher in the thrombolysis group than in the non-thrombolysis group (P<0.05). Conclusions R-tPA thrombolytic therapy can improve the prognosis of patients with ischemic IHS.