Optimization of CRISPR-Cas system for clinical cancer therapy

Cancer is a genetic disease caused by alterations in genome and epigenome and is one of the leading causes for death worldwide. The exploration of disease development and therapeutic strategies at the genetic level have become the key to the treatment of cancer and other genetic diseases. The functional analysis of genes and mutations has been slow and laborious. Therefore, there is an urgent need for alternative approaches to improve the current status of cancer research. Gene editing technologies provide technical support for efficient gene disruption and modification in vivo and in vitro, in particular the use of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems. Currently, the applications of CRISPR-Cas systems in cancer rely on different Cas effector proteins and the design of guide RNAs. Furthermore, effective vector delivery must be met for the CRISPR-Cas systems to enter human clinical trials. In this review article, we describe the mechanism of the CRISPR-Cas systems and highlight the applications of class II Cas effector proteins. We also propose a synthetic biology approach to modify the CRISPR-Cas systems, and summarize various delivery approaches facilitating the clinical application of the CRISPR-Cas systems. By modifying the CRISPR-Cas system and optimizing its in vivo delivery, promising and effective treatments for cancers using the CRISPR-Cas system are emerging.

Targeted pharmacokinetics and bioinformatics screening strategy reveals JAK2 as the main target for Xin-Ji-Er-Kang in treatment of MIR injury

BACKGROUND AND PURPOSE

Xin-Ji-Er-Kang (XJEK) is traditional Chinese formula presented excellent protective effects on several heart diseases, but the potential components and targets are still unclear. The aim of this study is to elucidate the effective components of XJEK and reveal its potential mechanism of cardioprotective effect in myocardial ischemia-reperfusion (MIR) injury.

EXPERIMENTAL APPROACH

Firstly, the key compounds in XJEK, plasma and heart tissue were analyzed by high resolution mass spectrometry. Bioinformatics studies were also involved to disclose the potential targets and the binding sites for the key compounds. Secondly, to study the protective effect of XJEK on MIR injury and related mechanism, mice subjected to MIR surgery and gavage administered with XJEK for 6 weeks. Cardiac function parameters and apoptosis level of cardiac tissue were assessed. The potential mechanism was further verified by knock down of target protein in vitro.

RESULTS

Pharmacokinetics studies showed that Sophora flavescens alkaloids, primarily composed with matrine, are the key component of XJEK. And, through bioinformatic analysis, we speculated JAK2 could be the potential target for XJEK, and could form stable hydrogen bonds with matrine. Administration of XJEK and matrine significantly improved heart function and reduced apoptosis of cardiomyocytes by increasing the phosphorylation of JAK2 and STAT3. The anti-apoptosis effect of XJEK and matrine was also observed on AC16 cells, and could be reversed by co-treatment with JAK2 inhibitor AG490 or knock-down of JAK2.

CONCLUSION

XJEK exerts cardioprotective effect on MIR injury, which may be associated with the activation of JAK2/STAT3 signaling pathway.

Long-term exposure to copper induces mitochondria-mediated apoptosis in mouse hearts

Copper is a trace element necessary for the normal functioning of organisms, but excessive copper contents may be toxic to the heart. The goal of this study was to investigate the role of excessive copper accumulation in mitochondrial damage and cell apoptosis inhibition. In vivo, the heart copper concentration and cardiac troponin I (c-TnI) and N-terminal forebrain natriuretic peptide (NT-pro-BNP) levels increased in the copper-laden model group compared to those of the control group. Histopathological and ultrastructural observations revealed that the myocardial collagen volume fraction (CVF), perivascular collagen area (PVCA) and cardiomyocyte cross-sectional area (CSA) were markedly elevated in the copper-laden model group compared with the control group. Furthermore, transmission electron microscopy (TEM) showed that the mitochondrial double-layer membrane was incomplete in the copper-laden model groups. Furthermore, cytochrome C (Cyt-C) expression was downregulated in mitochondria but upregulated in the cytoplasm in response to copper accumulation. In addition, Bcl-2 expression decreased, while Bax and cleaved caspase-3 levels increased. These results indicate that copper accumulation in cardiomyocyte mitochondria induces mitochondrial injury, and Cyt-C exposure and induces apoptosis, further resulting in heart damage.

Functional role and molecular mechanisms underlying prohibitin 2 in platelet mitophagy and activation

Platelet mitophagy is a major pathway involved in the clearance of injured mitochondria during hemostasis and thrombosis. Prohibitin 2 (PHB2) has recently emerged as an inner mitochondrial membrane receptor involved in mitophagy. However, the mechanisms underlying PHB2-mediated platelet mitophagy and activation are not completely understood. PHB2 is a highly conserved inner mitochondrial membrane protein that regulates mitochondrial assembly and function due to its unique localization on the mitochondrial membrane. The present study aimed to investigate the role and mechanism underlying PHB2 in platelet mitophagy and activation. Phorbol-12-myristate-13-acetate (PMA) was used to induce MEG-01 cells maturation and differentiate into platelets following PHB2 knockdown. Cell Counting Kit-8 assays were performed to examine platelet viability. Flow cytometry was performed to assess platelet mitochondrial membrane potential. RT-qPCR and western blotting were conducted to measure mRNA and protein expression levels, respectively. Subsequently, platelets were exposed to CCCP and the role of PHB2 was assessed. The results of the present study identified a crucial role for PHB2 in platelet mitophagy and activation, suggesting that PHB2-mediated regulation of mitophagy may serve as a novel strategy for downregulating the expression of platelet activation genes. Although further research into mitophagy is required, the present study suggested that PHB2 may serve as a novel therapeutic target for thrombosis-related diseases due to its unique localization on the mitochondrial membrane.

[Distribution and drug-resistance of 3 500 gram-negative bacteria in Guangzhou]

OBJECTIVE

To investigate the distribution and drug-resistance of the common gram-negative bacteria in Guangzhou.

METHODS

From July 2001 to August 2003, the resistance of 3 500 strains of common gram-negative bacteria isolated from 13 hospitals in Guangzhou to 15 to 21 antibiotics was determined by standard Kirby-Bauer method according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS, 2000). WHONET-5 software was used to analyze the data.

RESULTS

Totally 3 500 gram-negative bacterial strains were isolated from 13 hospitals in Guangzhou in the past two years, and the top 3 most common pathogens of them were Escherichia coli (1 244 strains, 35.5%), Klebsiella pneumoniae (900 strains, 25.7%), and Pseudomonas aeruginosa (547 strains, 15.6 %). The total prevalence of extended-spectrum beta-lactamases (ESBLs)-producing strains was 31.0% (1 084/3 500). The prevalences of ESBLs-producing strains in the Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter cloacae, Acinetobacter SP., other Enterobacter SP., Stenotrophomonas maltophilia, and Proteus SP. in Guangzhou were 38.7%, 37.9%, 5.3%, 55.2%, 8.2%, 27.7%, 33.3% and 9.2%, respectively. Among them, 1 463 (41.8%) strains was isolated from the respiratory tract and 943 (26.9%) from the urinary tract. According to our surveillance, the clinical antibacterial drug with the lowest total drug-resistance rates of Gram-negative bacteria was imipenem (8.7%) followed by Cefoperazone/sulbactam (13.3%), while that with the highest resistance was ampicillin (90.9%) followed by nalidixic acid (69.3%). Imipenem was the most effective agents against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Acinetobacter SP., other Enterobacter SP., and Proteus SP. isolated from 13 hospitals in Guangzhou, with drug-resistant rates of 1.1%, 0.5%, 0.6%, 3.2%, 0.8% and 0%, respectively, whereas the most effective agents against Pseudomonas aeruginosa and Stenotrophomonas maltophilia was cefoperazone/sulbactam, with the drug-resistance rates of 10.8% and 15.9%, respectively. Most of the isolates were multi-drug resistant. The resistance rates of ESBLs-producing strains to 15 to 21 antimicrobial agents were much higher than those of non-ESBLs-producing strains (P<0.05).

CONCLUSIONS

Drug resistance of the clinical isolates is a serious problem in Guangzhou, and the increasing prevalence of ESBLs-producing strains of other bacteria should be given full attention. An unanimous and effective strategy for controlling this problem is urgently needed. Imipenem and cefoperazone/sulbactam are the most effective antibiotics against the gram-negative bacteria isolated from the 13 hospitals in Guangzhou.