Molecular chaperone Hsp90 as a target for oxidant-based anticancer therapies.

Hsp90 is a molecular chaperone involved in the stabilization of many oncoproteins that are required for the acquisition and maintenance of the so-called six major hallmarks of cancer cells. Various strategies have, therefore, been developed to inhibit the chaperone activity of Hsp90 and induce cancer cell death through the destabilization of its client proteins. Among these strategies, we have shown that generation of oxidative stress leads to the cleavage and deactivation of Hsp90. Because cancer cells are often deficient in antioxidant enzymes and exhibit higher basal levels of reactive oxygen species (ROS) than their normal counterparts, inducing a selective oxidative stress may be a promising approach for cancer treatment. Thus, many redox-modulating agents have, therefore, been developed or are undergoing clinical trials and Hsp90 represents a new target for oxidative stress-generating agents. The purpose of this article is to review the current state of knowledge about Hsp90 and the use of oxidative stress-generating agents in cancer treatment. We will illustrate the review with some of our results concerning the effects of oxidative stress on Hsp90 using various oxidative stress-generating systems based on different quinones in combination with a well-known reducing agent (i.e., ascorbate). Our results show that oxidative stress provokes the cleavage of Hsp90 in CML cells, as well as the degradation of its client protein Bcr-Abl and the deactivation of its downstream signaling pathways, namely MAPK and STAT5. Overall, these results highlight the potential interest of using oxidative stress to target Hsp90.

Redox-active quinones and ascorbate: an innovative cancer therapy that exploits the vulnerability of cancer cells to oxidative stress.

Cancer cells are particularly vulnerable to treatments impairing redox homeostasis. Reactive oxygen species (ROS) can indeed play an important role in the initiation and progression of cancer, and advanced stage tumors frequently exhibit high basal levels of ROS that stimulate cell proliferation and promote genetic instability. In addition, an inverse correlation between histological grade and antioxidant enzyme activities is frequently observed in human tumors, further supporting the existence of a redox dysregulation in cancer cells. This biochemical property can be exploited by using redox-modulating compounds, which represent an interesting approach to induce cancer cell death. Thus, we have developed a new strategy based on the use of pharmacologic concentrations of ascorbate and redox-active quinones. Ascorbate-driven quinone redox cycling leads to ROS formation and provoke an oxidative stress that preferentially kill cancer cells and spare healthy tissues. Cancer cell death occurs through necrosis and the underlying mechanism implies an energetic impairment (ATP depletion) that is likely due to glycolysis inhibition. Additional mechanisms that participate to cell death include calcium equilibrium impairment and oxidative cleavage of protein chaperone Hsp90. Given the low systemic toxicity of ascorbate and the impairment of crucial survival pathways when associated with redox-active quinones, these combinations could represent an original approach that could be combined to standard cancer therapy.

Transcriptomic analysis of aorta from a short-term high-fat diet fed mouse reveals changes in the expression of vessel structure genes.

High-density microarrays were recently used to identify the genomic profiles of vascular cells during atherogenesis. This strategy succeeded in identifying both biomarkers and underlying biological processes of the pathological development. However, data documenting the early stages of disease are sparse. To identify the mechanisms involved in atherogenesis, we examined differential gene expression in the aorta of C57BL/6J mice fed a high-fat diet (HFD) or a low-fat diet (LFD), for a short period of time of three weeks. The cDNAmicroarray analysis revealed that the expression of 448 genes was significantly different between the two groups. As expected, key genes involved in lipid synthesis or catabolism were down- and upregulated, respectively, representing a normal gene expression response to increased cellular lipid levels. Overrepresented biological processes were identified by Gene Ontology (GO) analysis, which revealed that aortic cells differentiate into a new phenotype in mice fed the HFD. This phenotype was represented by changes in the expression of 81 genes associated with extracellular matrix and cytoskeletal modifications. Some of these genes were previously shown to be involved in the cardiovascular diseases process. In conclusion, short-term HFD consumption results in metabolic disturbances leading to a broad induction of genes involved in vessel architecture remodelling.

In situ modulation of oxidative stress: a novel and efficient strategy to kill cancer cells.

Cancer cells show an up-regulation of glycolysis, they readily take up vitamin C, and they appear more susceptible to an oxidative stress than the surrounding normal cells. Here we compare, analyse and discuss these particular hallmarks by performing experiments in murine hepatomas (TLT cells) and freshly isolated mouse hepatocytes. The results show that rates of lactate formation are higher in TLT cells as compared to mouse hepatocytes, but their ATP content represents less than 25% of that in normal cells. The uptake of vitamin C is more important in hepatoma cells as compared to normal hepatocytes. This uptake mainly occurs through GLUT1 transporters. Hepatoma cells have less than 10% of antioxidant enzyme activities as compared to normal hepatocytes. This decrease includes not only the major antioxidant enzymes, namely catalase, superoxide dismutase and glutathione peroxidase, but also the GSH content. Moreover, catalase is almost not expressed in hepatoma cells as shown by western blot analysis. We explored therefore a selective exposure of cancer cells to an oxidative stress induced by pro-oxidant mixtures containing pharmacological doses of vitamin C and a redox active compound such as menadione (vitamin K(3)). Indeed, the combination of vitamin C (which accumulates in hepatoma cells) and a quinone undergoing a redox cycling (vitamin K(3)) leads to an oxidative stress that kills cancer cells in a selective manner. This differential sensitivity between cancer cells and normal cells may have important clinical applications, as it has been observed with other pro-oxidants like Arsenic trioxide, isothiocyanates, Adaphostin.

Plasma proteome analysis: 2D gels and chips.

The knowledge of concentration, modification and interaction of proteins is fundamental in determining the phenotype of living organisms. Plasma, the primary clinical specimen, contains numerous and diverse proteins. The functions of these proteins are as manifold as the diversity of the protein themselves. Many of them have been largely used for many years as biomarkers of diseases and indicators of the physiological functions. The study of plasma proteome promises to be a significant advance in various areas of biological and clinical research. Two-dimensional polyacrylamide gel electrophoresis is considered as a primary tool in separating thousand of plasma proteins. This approach enables comparing normal and diseased samples revealing differently expressed proteins. Other proteomic techniques suitable for plasma analysis such as protein microarrays are now either established or are still being improved. This article briefly reviews the application of two-dimensional electrophoresis and the current status of technical aspects for plasma proteome.