A self-inducible heterologous protein expression system in Escherichia coli

Escherichia coli is an important experimental, medical and industrial cell factory for recombinant protein production. The inducible lac promoter is one of the most commonly used promoters for heterologous protein expression in E. coli. Isopropyl-β-D-thiogalactoside (IPTG) is currently the most efficient molecular inducer for regulating this promoter’s transcriptional activity. However, limitations have been observed in large-scale and microplate production, including toxicity, cost and culture monitoring. Here, we report the novel SILEX (Self-InducibLe Expression) system, which is a convenient, cost-effective alternative that does not require cell density monitoring or IPTG induction. We demonstrate the broad utility of the presented self-inducible method for a panel of diverse proteins produced in large amounts. The SILEX system is compatible with all classical culture media and growth temperatures and allows protein expression modulation. Importantly, the SILEX system is proven to be efficient for protein expression screening on a microplate scale.

Quantifying Gp96/Grp94 complexes preparations for vaccines: a key step often inaccurate

Glycoprotein 96 (Gp96)-peptide complexes are highly investigated for vaccines preparation, particularly in cancer therapy. Gp96, formerly called tumor rejection antigen (TRA)-1, is able to elicit an immune response that can protect mice against tumors, when the mice share the same haplotype than those bearing the tumors from which Gp96 was purified. Secreted Gp96-peptide complexes act as danger signals thereby stimulating the innate immunity regardless of the chaperoned peptides. In contrast, the tumor rejection antigen role of Gp96-peptide complexes is held by the chaperoned peptides in a dose-dependent manner. The purification step is crucial both for insuring the quality and the quantity of Gp96-peptide complexes. To this aim, different methods have been described but they are often suboptimal for the quantification of these complexes. In this review, we discuss a hot topic: the use of the chaperone Gp96 for vaccination purposes in cancer, and also detail the current methods for quantifying Gp96-peptide preparations.

The small heat shock proteins family: the long forgotten chaperones

Small heat shock proteins are a rather heterogeneous family of ATP-independent chaperones, some of which have been proven to block protein aggregation and help the cells to survive stressful conditions. Although much less studied than high molecular weight HSPs like HSP70/HSPA or HSP90/HSPC, their implication in physio-pathological processes and human diseases is now well evidenced, as it will be discussed in the different reviews of this special issue. In this mini-review we will just present a general introduction about the small heat shock proteins family. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Robust prognostic value of a knowledge-based proliferation signature across large patient microarray studies spanning different cancer types

Tumour proliferation is one of the main biological phenotypes limiting cure in oncology. Extensive research is being performed to unravel the key players in this process. To exploit the potential of published gene expression data, creation of a signature for proliferation can provide valuable information on tumour status, prognosis and prediction. This will help individualising treatment and should result in better tumour control, and more rapid and cost-effective research and development. From in vitro published microarray studies, two proliferation signatures were compiled. The prognostic value of these signatures was tested in five large clinical microarray data sets. More than 1000 patients with breast, renal or lung cancer were included. One of the signatures (110 genes) had significant prognostic value in all data sets. Stratifying patients in groups resulted in a clear difference in survival (P-values <0.05). Multivariate Cox-regression analyses showed that this signature added substantial value to the clinical factors used for prognosis. Further patient stratification was compared to patient stratification with several well-known published signatures. Contingency tables and Cramer's V statistics indicated that these primarily identify the same patients as the proliferation signature does. The proliferation signature is a strong prognostic factor, with the potential to be converted into a predictive test. Furthermore, evidence is provided that supports the idea that many published signatures track the same biological processes and that proliferation is one of them.

Theoretical study of cardiac transient conduction blocks on reentries induction. Applications to antiarrhythmic drugs

Limitations of antiarrhythmic drugs on cardiac sudden death prevention appeared since the early 80's. The "Cardiac Arrhythmia Suppression Trial" (CAST) showed more recently that mortality was significantly higher in patients treated with some particular antiarrhythmic drugs than in non-treated patients. In this field, our group recently demonstrated that a bolus of a Class 1 B antiarrhythmic drug was able to trigger a ventricular fibrillation due to transient blocks induction. The aim of the present work was to systematically study, by use of the van Capelle and Durrer (VCD) model which allows to simulate ventricular activation wave propagation, the link between arrhythmogenic effects and the ability of transient blocks to possibly degenerate in severe arrhythmias. A fragment of the ventricular wall is represented by an array of 16384 elements electrically coupled. Effects of induction of one or several transient blocks, as the effects of their size and duration on possible induction of reentries have been studied. Results obtained show that various combinations between these different parameters may trigger reentries, ventricular tachycardia and/or more complex patterns assimilable to ventricular fibrillation. These results clearly evidence the fact that possible induction of transient blocks may directly be related to risk factor associated to arrhythmogenic effects of antiarrhythmic drugs.