Chronic Oxidative Stress Leads to Malignant Transformation Along With Acquisition of Stem Cell Characteristics, and Epithelial to Mesenchymal Transition in Human Renal Epithelial Cells

Abstract

Oxidative injury to cellular macromolecules has been suggested as a common pathway shared by multiple etiological factors for kidney cancer. Whether the chronic oxidative stress alone is sufficient to induce malignant transformation in human kidney cells is not clear. Therefore, the objective of this study was to evaluate the effect of H2O2-induced chronic oxidative stress on growth, and malignant transformation of HK-2 normal kidney epithelial cells. This study revealed that chronic oxidative stress causes increased growth and neoplastic transformation in normal kidney epithelial cells at non-cytotoxic dose and increased adaptation to cytotoxic level. This was confirmed by gene expression changes, cell cycle analysis, anchorage independent growth assay and in vivo tumorigenicity in nude mice. Stem cells characteristics as revealed by up-regulation of stem cell marker genes, and morphological changes indicative of EMT with up regulation of mesenchymal markers were also observed in cells exposed to chronic oxidative stress. Antioxidant NAC did not reverse the chronic oxidative stress-induced growth, and adaptation suggesting that perturbed biological function in these cells are permanent. Partial reversal of oxidative stress-induced growth, and adaptation by silencing of Oct 4 and Snail1, respectively, suggest that these changes are mediated by acquisition of stem cell and EMT characteristics. In summary, this study for the first time suggests that chronic exposure to elevated levels of oxidative stress is sufficient to induce malignant transformation in kidney epithelial cells through acquisition of stem cell characteristics. Additionally, the EMT plays an important role in increased adaptive response of renal cells to oxidative stress.

Role of thioredoxin reductase 1 in dysplastic transformation of human breast epithelial cells triggered by chronic oxidative stress

“…Therefore, it is of great possibility that TrxR1 drives the progression of breast cancer by catalyzing Trx1 along with its related EMT processes, though this hypothesis clearly needs more evidence to be supported. Stemness characteristics are also usually observed promoted in the process of dysplastic transformation and tumorigenic potential enhancement induced by H 2 O 2 394041. In this study, four stem cell markers, (i.e.…”

Posttranscriptional silencing of the lncRNA MALAT1 by miR-217 inhibits the epithelial–mesenchymal transition via enhancer of zeste homolog 2 in the malignant transformation of HBE cells induced by cigarette smoke extract

“…The EMT, which is involved in increased cell survival and the adaptive response of cells to environmental carcinogens (Xu et al, 2012;Mahalingaiah et al, 2015), is viewed as a step in tumor invasion and metastasis (Thiery and Sleeman, 2006). A wide range of proteins, including cell-surface proteins (E-cadherin, N-cadherin, and integrins), cytoskeletal proteins (α-smooth muscle actin, vimentin, and β-catenin), extracellular matrix proteins (collagens, fibronectin, and laminin), and transcription factors (SNAIL1, SNAIL2, TWIST, and LEF-1), relate to the EMT (Gheldof and Berx, 2013).…”

Chronic Oxidative Stress Increases Resistance to Doxorubicin-Induced Cytotoxicity in Renal Carcinoma Cells Potentially Through Epigenetic Mechanism

“…Kidney is a well known target organ for adverse effects of oxidative stress that lead to many pathologic changes, including cancer (Forbes et al, 2008;Mahalingaiah et al, 2015). Normal kidney cells produce low levels of ROS that get detoxified by naturally occurring antioxidants.…”

“…Additionally, several chemotherapeutic agents, including doxorubicin itself, also generate ROS and thereby increase the oxidative stress burden (Ferlini et al, 1999;Pervaiz and Clement, 2004;Sullivan and Graham, 2008). Although the adverse effects of oxidative stress in malignant transformation of kidney cells are known (Mahalingaiah et al, 2015), the influence of oxidative stress on the sensitivity/efficacy of doxorubicin-induced cytotoxicity in cancer cells is not well understood. It is in this context that the present study evaluated sensitivity to doxorubicin in kidney cancer cells adapted to chronic oxidative stress.…”

“…For this anchorage-independent growth assay, Caki-1 cells exposed to chronic oxidative stress were treated with doxorubicin and 5-Aza-2dC, as in the treatment protocol described for the cytotoxicity assay, then used for seeding on soft agar. The base layer of soft agar (0.5%) and the top layer of agar (0.35%) mixed with cells (5000 cells) in McCoy's medium were prepared as reported previously by us (Mahalingaiah et al, 2015). Plates were incubated at 37°C in an incubator with 5% CO 2 and observed daily for colony formation by microscopic observation until the soft agar colonies reach clearly visible size.…”