Oxidative Stress Modulates DNA Methylation during Melanocyte Anchorage Blockade Associated with Malignant Transformation

Abstract

Both oxidative/nitrosative stress and alterations in DNA methylation are observed during carcinogenesis of different tumor types, but no clear correlation between these events has been demonstrated until now. Melanoma cell lines were previously established after submitting the nontumorigenicmelanocyte lineage, melan-a, to cycles of anchorage blockade. In this work, increased intracellular oxidative species and nitric oxide levels, as well as alterations in the DNA methylation, were observed after melan-a detachment, which were also associated with a decrease in intracellular homocysteine (Hcy), an element in the methionine (universal methyl donor) cycle. This alteration was accompanied by increase in glutathione (GSH) levels and methylated DNA content. Furthermore, a significant increase in dnmt1 and 3b expression was identified along melan-a anchorage blockade. L(G)-Nitro-L-arginine methyl esther (L-NAME), known as a nitric oxide synthase (NOS) inhibitor, and N-acetyl-L-cysteine (NAC) prevented the increase in global DNA methylation, as well as the increase in dnmt1 and 3b expression, observed during melan-a detachment. Interestingly, both L-NAME and NAC did not inhibit nitric oxide (NO) production in these cells, but abrogated superoxide anion production during anchorage blockade. In conclusion, oxidative stress observed during melanocyte anchorage blockade seems to modulate DNA methylation levels and may directly contribute to the acquisition of an anoikis-resistant phenotype through an epigenetic mechanism.

Angiopoietin-like Protein 2 Accelerates Carcinogenesis by Activating Chronic Inflammation and Oxidative Stress

“…Thus increased oxidative stress caused by Angptl2 overexpression may promote Msh2 promoter methylation. Previously, others have reported that ROS promotes development of human carcinogenesis through epigenetic regulation of gene expression (32). For example, ROS-induced oxidative stress reportedly silences promoters of tumor suppressors via hypermethylation (39).…”

“…Methylation of the Msh2 promoter in skin tissues of K14-Angptl2 Tg mice decreases following NAC treatment Oxidative stress has been associated with epigenetic modifications (30)(31)(32). Therefore, we asked whether decreased Msh2 expression seen in skin tissues of K14-Angptl2 Tg mice was due to oxidative stress and subsequent epigenetic modification of Msh2.…”

Eryngium foetidum Suppresses Inflammatory Mediators Produced by Macrophages

“…In addition, oxidative stress can involve gene silencing by hypermethylation of tumor suppressor gene promoter region and lead to malignant progression (Lim et al, 2008). Thus, both DNA hypo-and hypermethylation ROS-induced epigenetic on promoter of genes involve in malignant transformation and progression of several tumors (Campos et al, 2007). The E. foetidum leaf extract may reduce risk factors of carcinogenesis by reducing intracellular ROS accumulation.…”

Antioxidant Defense and UV-Induced Melanogenesis: Implications for Melanoma Prevention

“…Moreover, the presence of high levels of RNS, in particular nitric oxide (NO), and nitrosative products in cutaneous melanoma has been observed to be correlated with poor prognosis of patients and contributed to melanoma invasiveness (Chin & Deen, 2010). Thus, excessive ROS/ RNS-mediated imbalanced redox state and oxidative damage to the biomolecules of melanocytes might play a role in the pathogenesis of malignant melanoma by disturbing cellular machinery that further impairs cellular homeostasis and function involving differentiation, proliferation and malignant transformation of melanocytes (Campos et al, 2007;Kadekaro et al, 2005). Ultimately, UVR can initiate melanomagenesis via various pathways including mutagenicity of DNA photoproducts and interference in cell signaling that subsequently affects melanocyte apoptosis, proliferation, differentiation and functions including the regulation of melanogenesis (von Thaler et al, 2010;Wittgen & van Kempen, 2007).…”

“…Major endogenous antioxidants of the skin include GSH, a ubiquitous thiol antioxidant, which potentially maintains redox balance and serves as a substrate for GPx or glutathione-S-transferase (GST), and antioxidant enzymes including CAT and GPx that are primarily involved in the neutralization of H 2 O 2 , a byproduct of melanogenic process (Campos et al, 2007;Masaki et al, 1998). UVR could result in deficiency in antioxidant defenses in association with melanocyte damage and disturbance of melanin synthesis (Kvam & Dahle, 2003;Maresca et al, 2008).…”