Microarray Analysis and Biochemical Correlations of Oxidative Stress Responsive Genes in Retinoblastoma

Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, Chennai, India.
Current eye research (Impact Factor: 1.64). 06/2012; 37(9):830-41. DOI: 10.3109/02713683.2012.678544
Source: PubMed


Oxidative stress, which refers to the biological damage caused by free radicals produced in excess of innate antioxidant defenses, is indicated in the ocular cancer retinoblastoma (RB). Here we have analysed the differential expression of oxidative stress responsive genes in oxidant-induced RB cells, and in RB tumor tissues.
The study included cultured RB cells, and four RB tumor tissues. The reactive oxygen species (ROS) levels in Y79 cells and the RB tumor induced by hydrogen peroxide were quantified by Dichlorofluorescein (DCF) fluorescence assay. We then analysed the gene expression profile of cultured RB cells induced with hydrogen peroxide (400 µM H(2)O(2) for 8 h) by microarray analysis, and the expression of select genes were validated in Y79 cells and RB tumor tissues by real-time PCR analysis.
The oxidant-induced RB tumors showed an average increase in ROS levels of 44-fold compared to induced non-neoplastic donor retina. H(2)O(2)-induced RB cell line showed a 3-fold increase in ROS levels. Microarray analysis on RB cell line induced with H(2)O(2) showed differentially regulated genes involved in cellular processes such as: oxidative stress, angiogenesis, lipid metabolism, cell proliferation, and cell signaling pathways. Several up-regulated genes such as SOD, GPX, CAT, CDC25A, CREBBP, JUN, MMP-2, iNOS, CRYAA, RXRA, ACACB and HMGCR were validated by real-time PCR. These results corroborated with the gene expression analysis in RB tumor tissues. Relating the antioxidant gene expression with the clinico-pathologic features of the tumor tissues, we found that the tumor with invasion of choroid, optic nerve and retinal pigment epithelium, had relatively higher ROS levels and minimal antioxidant gene expression, when compared with the tumor with only choroidal invasion.
The study suggests active involvement of redox signaling pathways in the pathogenesis of RB. Consideration of oxidative stress components in the clinical management of RB patients is emphasized.

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    • "We earlier reported the pro-oxidant state of RB tumor cells, in which cancer cells contained increased amounts of malondialdehyde and reactive oxygen species (ROS) levels compared to non-neoplastic donor retina. Oxidative stress levels correlated with the tumor cell invasiveness [40] [41]. Enhanced lipogenesis in tumor cells is an adaptive response to redox imbalance during glycolysis. "
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    ABSTRACT: Retinoblastoma (RB) is a malignant intra-ocular neoplasm that affects children (usually below the age of 5 years). In addition to conventional chemotherapy, novel therapeutic strategies that target metabolic pathways such as glycolysis and lipid metabolism are emerging. Fatty acid synthase (FASN), a lipogenic multi-enzyme complex, is over-expressed in retinoblastoma cancer. The present study evaluated the biochemical basis of FASN inhibition induced apoptosis in cultured Y79 RB cells. FASN inhibitors (cerulenin, triclosan and orlistat) significantly inhibited FASN enzyme activity (P < 0.05) in Y79 RB cells. This was accompanied by a decrease in palmitate synthesis (end-product depletion), and increased malonyl CoA levels (substrate accumulation). Differential lipid profile was biochemically estimated in neoplastic (Y79 RB) and non-neoplastic (3T3) cells subjected to FASN inhibition. The relative proportion of phosphatidyl choline to neutral lipids (triglyceride + total cholesterol) in Y79 RB cancer cells was found to be higher than the non-neoplastic cells, indicative of altered lipid distribution and utilization in tumour cells. FASN inhibitors treated Y79 RB and fibroblast cells showed decrease in the cellular lipids (triglyceride, cholesterol and phosphatidyl choline) levels. Apoptotic DNA damage induced by FASN inhibitors was accompanied by enhanced lipid peroxidation.
    Full-text · Article · Jun 2013 · Biochimica et Biophysica Acta
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    ABSTRACT: Background: Oxidative stress damages to cells or tissues, however, cellular defense systems including heme oxygenase-1 (HO-1) protects them against oxidative stress. Flavonoid compounds can activate cellular defense mechanisms against oxidative stress and it can reduce cell damages. In the present study, the cytoprotective effects of morin (3,5,7,2’,4’-pentahydroxyflavone), in terms of HO-1 enzyme, against the oxidative stress and its involved mechanisms was elucidated. Methods: RT-PCR and western blot analysis were assessed to detect the mRNA and protein expression, respectively. Cell viability was measured by using MTT test. The immunocytochemistry was performed to define location of target protein. Electrophoretic mobility shift assay performed to measure transcription factor-promoter site binding activity. Results: Morin elevated mRNA and protein levels of HO-1 in human lens epithelial cells (HLE-B3). HO-1 inhibitor ZnPP attenuated the protective effect of morin against H2O2-induced cytotoxicity. Morin increased the protein level of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which up-regulates HO-1 expression by binding to the antioxidant response element (ARE) within the HO-1 gene promoter. Moreover, morin induced the translocation of Nrf2 from the cytosol into the nucleus. Morin activated extracellular-regulated kinase (ERK), while ERK inhibitor attenuated morin-enhanced Nrf2 and HO-1 expression. Conclusions: Morin activates ERK-Nrf2 signaling cascades in HLE-B3 cells, leading to the up-regulation of HO-1 and cytoprotection against oxidative stress.
    Full-text · Article · Sep 2013
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