Maria Adelaide Pronzato

Reactive oxygen species (ROS) and their products are components of cell signaling pathways and play important roles in cellular physiology and pathophysiology. Under physiological conditions, cells control ROS levels by the use of scavenging systems such as superoxide dismutases, peroxiredoxins, and glutathione that balance ROS generation and elimination. Under oxidative stress conditions, excessive ROS can damage cellular proteins, lipids, and DNA, leading to cell damage that may contribute to carcinogenesis. Several studies have shown that cancer cells display an adaptive response to oxidative stress by increasing expression of antioxidant enzymes and molecules. As a double‐edged sword, ROS influence signaling pathways determining beneficial or detrimental outcomes in cancer therapy. In this review, we address the role of redox homeostasis in cancer growth and therapy and examine the current literature regarding the redox regulatory systems that become upregulated in cancer and their role in promoting tumor progression and resistance to chemotherapy.

Glutathione (GSH) plays an important role in a multitude of cellular processes, including cell differentiation, proliferation, and apoptosis, and disturbances in GSH homeostasis are involved in the etiology and progression of many human diseases including cancer. While GSH deficiency, or a decrease in the GSH/glutathione disulphide (GSSG) ratio, leads to an increased susceptibility to oxidative stress implicated in the progression of cancer, elevated GSH levels increase the antioxidant capacity and the resistance to oxidative stress as observed in many cancer cells. The present review highlights the role of GSH and related cytoprotective effects in the susceptibility to carcinogenesis and in the sensitivity of tumors to the cytotoxic effects of anticancer agents.

Intracellular redox state modulation can influence cell proliferation, differentiation or death. Here we show that Retinoic Acid (RA)‐induced neuroblastoma cell differentiation is accompanied by increased expression of anion superoxide generating enzyme NADPH oxidase, decreased SOD1 expression and increased catalase expression. Moreover, cell differentiation induced PKC alfa inactivation and PKC delta activation. We believe these alterations responsible for the observed cell sensitivity to glycoxidative stress: indeed, only the RA‐differentiated cell viability decreased after exposure to Advanced Glycation End Products (AGEs), via intracellular ROS overproduction, while undifferentiated cells proved insensitive. AGE‐induced effects on differentiated cells were prevented by pre‐treating cells with NADPH oxidase or PKC delta inhibitors. These observations may be useful in order to identify redox sensitive molecular targets responsible for cell growing rate modifications. Grants from PRIN n.2006065711_002

Previous studies have demonstrated that acute ethanol intoxication affects various steps of protein glycosylation at the level of rat liver endoplasmic reticulum and Golgi apparatus. The aim of this investigation was to demonstrate whether chronic ethanol intake can induce definitive changes of liver glycoprotein processing. Rats were given ethanol by liquid diet for 8 weeks. At the end of this period the triglyceride levels in liver homogenate and microsomes were significantly higher than in controls. Isolated hepatocytes prelabelled with [³H]Na palmitate and [¹⁴C]glucosamine showed a significant storage of the lipid and carbohydrate radioactivity in microsomes and Golgi apparatus and a significant impairment of labelled glycolipoprotein secretion. Changes of the glycosylation steps were observed both in endoplasmic reticulum and in Golgi apparatus: in the former the levels of dolichyl phosphate, which is rate-limiting for the synthesis of glycoprotein, showed a significant reduction; in the latter the activity of the main enzymes responsible for the terminal glycosylation process was significantly decreased. These data suggest that an impairment of glycoprotein maturation may be involved in the pathogenesis of liver injury induced by chronic ethanol intake.