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Antioxidants Accelerate Lung Cancer Progression in Mice

ABSTRACT: Antioxidants are widely used to protect cells from damage induced by reactive oxygen species (ROS). The concept that antioxidants can help fight cancer is deeply rooted in the general population, promoted by the food supplement industry, and supported by some scientific studies. However, clinical trials have reported inconsistent results. Here, we show that supplementing the diet with the antioxidants N-acetylcysteine (NAC) and vitamin E markedly increases tumor progression and reduces survival in mouse models of B-RAF- and K-RAS-induced lung cancer. RNA sequencing revealed that NAC and vitamin E, which are structurally unrelated, produce highly coordinated changes in tumor transcriptome profiles, dominated by reduced expression of endogenous antioxidant genes. NAC and vitamin E increase tumor cell proliferation by reducing ROS, DNA damage, and p53 expression in mouse and human lung tumor cells. Inactivation of p53 increases tumor growth to a similar degree as antioxidants and abolishes the antioxidant effect. Thus, antioxidants accelerate tumor growth by inactivating the ROS-p53 axis. Because p53 inactivation occurs late in tumor progression, antioxidants may accelerate the growth of early tumors or precancerous lesions in high-risk populations such as smokers and patients with chronic obstructive pulmonary disease who receive NAC to relieve mucus production.

ORGANISM(S): Mus musculus

PROVIDER: GSE52594 | GEO | 2014/01/31

SECONDARY ACCESSION(S): PRJNA229429

REPOSITORIES: GEO

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Project description:The molecular mechanisms of exercise-induced cardiovascular protection are poorly understood. There is growing evidence that reactive oxygen species (ROS) are necessary for some of these adaptations and antioxidants may be used to investigate this effect. This study aimed to determine the effects of exercise and/or antioxidant supplementation on myocardial and vascular endothelium gene expression. Male Wistar rats were divided into four groups: i) endurance exercise (90min of treadmill running 4d/week, 14 weeks); ii) antioxidant-treated; iii) antioxidant and endurance exercise and iv) control. The supplemented animals received Vitamin E (1000 IU/kg diet) and ï¡-lipoic acid (1.6 g/kg diet) mixed with rat chow. cDNA microarray analysis was performed using purified endothelial RNA from myocardial and coronary artery endothelial cells and showed that the expression levels of 35, 40 and 40 genes were altered for groups i, ii, and iii respectively compared to control. Differentially expressed genes were analysed using the KEGG pathway database, hierarchical cluster and DAVID analysis. These analyses revealed that a gene involved in cardiovascular disease progression, Ras homolog gene family member A (RhoA) was down-regulated by exercise, upregulated by antioxidant supplementation and the combination of exercise and antioxidant blunted both effects. These findings were confirmed by real-time PCR. In summary, exercise and antioxidant supplementation affect endothelial cell gene expression and ROS appear necessary for some of these adaptations. 48 Male Wistar rats were divided into four groups: i) endurance exercise (90min of treadmill running 4d/week, 14 weeks); ii) antioxidant-treated; iii) antioxidant and endurance exercise and iv) control. The supplemented animals received Vitamin E (1000 IU/kg diet) and ï¡-lipoic acid (1.6 g/kg diet) mixed with rat chow. cDNA microarray analysis was performed using purified endothelial RNA from myocardial and coronary artery endothelial cells. Based on the limited material available, it was necessary to combine the RNA into three pools per treatment group for CAEC (approx 400 ng of total RNA), and four pools for LVEC (approx 1 Î¼g of total RNA) with an additional reference pool from each control group.

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Antioxidants Accelerate Lung Cancer Progression in Mice

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