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Reduced expression of miRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11.

ABSTRACT: Resistance to cisplatin-based chemotherapy is a major obstacle to bladder cancer treatment. We aimed to identify microRNAs (miRNA) that are dysregulated in cisplatin-resistant disease, ascertain how these contribute to a drug-resistant phenotype, and how this resistance might be overcome.miRNA expression in paired cisplatin-resistant and -sensitive cell lines was measured. Dysregulated miRNAs were further studied for their ability to mediate resistance. The nature of the cisplatin-resistant phenotype was established by measurement of cisplatin/DNA adducts and intracellular glutathione (GSH). Candidate miRNAs were examined for their ability to (i) mediate resistance and (ii) alter the expression of a candidate target protein (SLC7A11); direct regulation of SLC7A11 was confirmed using a luciferase assay. SLC7A11 protein and mRNA, and miRNA-27a were quantified in patient tumor material.A panel of miRNAs were found to be dysregulated in cisplatin-resistant cells. miRNA-27a was found to target the cystine/glutamate exchanger SLC7A11 and to contribute to cisplatin resistance through modulation of GSH biosynthesis. In patients, SLC7A11 expression was inversely related to miRNA-27a expression, and those tumors with high mRNA expression or high membrane staining for SLC7A11 experienced poorer clinical outcomes. Resistant cell lines were resensitized by restoring miRNA-27a expression or reducing SLC7A11 activity with siRNA or with sulfasalazine.Our findings indicate that miRNA-27a negatively regulates SLC7A11 in cisplatin-resistant bladder cancer, and shows promise as a marker for patients likely to benefit from cisplatin-based chemotherapy. SLC7A11 inhibition with sulfasalazine may be a promising therapeutic approach to the treatment of cisplatin-resistant disease.

SUBMITTER: Drayton RM

PROVIDER: S-EPMC3974662 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Reduced expression of miRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11.

Drayton Ross M RM Dudziec Ewa E Peter Stefan S Bertz Simone S Hartmann Arndt A Bryant Helen E HE Catto James Wf JW

Clinical cancer research : an official journal of the American Association for Cancer Research 20140210 7

<h4>Purpose</h4>Resistance to cisplatin-based chemotherapy is a major obstacle to bladder cancer treatment. We aimed to identify microRNAs (miRNA) that are dysregulated in cisplatin-resistant disease, ascertain how these contribute to a drug-resistant phenotype, and how this resistance might be overcome.<h4>Experimental design</h4>miRNA expression in paired cisplatin-resistant and -sensitive cell lines was measured. Dysregulated miRNAs were further studied for their ability to mediate resistance ...[more]

PMID: 24516043

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Project description:The cystine/glutamate exchanger (xCT, SLC7A11) is a component of the system Xc amino-acid antiporter that is able to export glutamate and import cysteine into cells. The xCT amino acid exchanger has received a lot of attention, due to the fact that cysteine is an essential substrate for the synthesis of glutathione (GSH), an endogenous antioxidant in cells. The objective of this research was to clone the full-length cDNA of chicken xCT, and to investigate the gene expression of xCT in different tissues, including intestinal segments of broiler chickens during development. The full-length cDNA of chicken xCT (2,703 bp) was obtained from the jejunum by reverse transcription-PCR and sequenced. Homology tests showed that chicken xCT had 80.4%, 80.2%, and 71.2% homology at the nucleotide level with humans, cattle, and rats, respectively. Likewise, amino acid sequence analysis showed that chicken xCT protein is 86.4%, 79.3%, and 75.6% homologous with humans, cattle, and rats, respectively. Additionally, phylogenetic analysis indicated that chicken xCT genes share a closer genetic relationship with humans and cattle, than with rats. The chicken xCT protein has 12 transmembrane helixes, 6 extracellular loops, and 5 intracellular loops. The mRNA of xCT was detected in all tissues, including intestinal segments, in which the mRNA expression of xCT was significantly higher (P < 0.05) within the colon, compared to the jejunum and ileum. During development, a linear pattern of changes regarding the levels of the xCT mRNA was found, indicating that there was an abundance of xCT within the duodenum (P < 0.05). Furthermore, there were changes of the xCT mRNA abundance in the colon during development, which displayed linear and cubic patterns (P < 0.05). These results indicated that xCT is widely expressed both in intestinal segments, as well as other organs that are not associated with nutrient absorption. Further investigation is needed to characterize the functional relevance of xCT activity in oxidative stress and inflammation in the small intestine of broiler chickens.

Project description:BackgroundFerroptosis is a newly generated regulatory cell death promoted by the accumulated lipid-based reactive oxygen species (ROS). Solute carrier family 7 member 11 (SLC7A11), the cystine/glutamate antiporter, is known as a ferroptosis executor that exhibits a positive correlation with carcinoma progression because of antioxidant function. Nonetheless, it is yet unclear on the understanding of ferroptosis regulation in lung cancer.MethodsDatabase, qRT-PCR, Western-blot (WB), and immunohistochemistry were utilized to determine SLC7A11 expression and function, as well as gene iron related to necrosis in clinical tissue specimens and cells; a ferroptosis inducer, inhibitors, and SLC7A11 lentivirus were used to confirm SLC7A11's biological activity in cell viability, oxidative stress, lipid peroxidation, and iron ion enrichment in non-small cell lung cancer (NSCLC) in different cells; lentivirus was used to infect lung adenocarcinoma cell lines to acquire miR-27a-3p overexpression and knockdown cell lines, and to detect SLC7A11 level through qRT-PCR and WB. The influence of upregulated/downregulated miR-27a-3p on ferroptosis and other related biological characteristics of lung adenocarcinoma cell lines was detected.ResultsUpregulated SLC7A11 was shown in NSCLC patients and cells, and increased SLC7A11 had a relation to the poorly prognostic status of NSCLC patients. Besides, a novel miRNA, miR-27a-3p, was an essential modulator of ferroptosis via directly targeting SLC7A11 in NSCLC cells. Overexpressing miR-27a-3p led to SLC7A11 suppression via directly binding to its 3'-UTR, followed by the reduction of erastin-caused ferroptosis. In contrast, inhibited miR-27a-3p resulted in an increase in NSCLC cells' sensitivity to erastin. Of importance, the accumulated lipid ROS and cell death of iron peptide mediated by anti-miR-27a-3p can be eliminated by impeding the glutamylation process. Our literature collectively uncovered that miR-27a-3p modulated ferroptosis by targeting SLC7A11 in NSCLC cells, illustrating the important role of miRNA in ferroptosis.ConclusionMiR-27a-3p modulates ferroptosis via targeting SLC7A11 in NSCLC cells, implying the significant role of miR-27a-3p/SLC7A11 in ferroptosis.

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Project description:Oxidative stress figures prominently in retinal diseases, including diabetic retinopathy, and glaucoma. Ligands for ?1R, a unique transmembrane protein localized to the endoplasmic reticulum, mitochondria, and nuclear and plasma membranes, have profound retinal neuroprotective properties in vitro and in vivo. Studies to determine the mechanism of ?1R-mediated retinal neuroprotection have focused mainly on neurons. Little is known about the effects of ?1R on Müller cell function, yet these radial glial cells are essential for homeostatic support of the retina. Here we investigated whether ?1R mediates the oxidative stress response of Müller cells using wild-type (WT) and ?1R-knockout (?1RKO) mice. We observed increased endogenous reactive oxygen species (ROS) levels in ?1RKO Müller cells compared to WT, which was accompanied by decreased expression of Sod1, catalase, Nqo1, Hmox1, Gstm6, and Gpx1. The protein levels of SOD1, CAT, NQO1, and GPX1 were also significantly decreased. The genes encoding these antioxidants contain an antioxidant response element (ARE), which under stress is activated by NRF2, a transcription factor that typically resides in the cytoplasm bound by KEAP1. In the ?1RKO Müller cells Nrf2 expression was decreased significantly at the gene (and protein) level, whereas Keap1 gene (and protein) levels were markedly increased. NRF2-ARE binding affinity was decreased markedly in ?1RKO Müller cells. We investigated system xc(-), the cystine-glutamate exchanger important for synthesis of glutathione (GSH), and observed decreased function in ?1RKO Müller cells compared to WT as well as decreased GSH and GSH/GSSG ratios. This was accompanied by decreased gene and protein levels of xCT, the unique component of system xc(-). We conclude that Müller glial cells lacking ?1R manifest elevated ROS, perturbation of antioxidant balance, suppression of NRF2 signaling, and impaired function of system xc(-). The data suggest that the oxidative stress-mediating function of retinal Müller glial cells may be compromised in the absence of ?1R. The neuroprotective role of ?1R may be linked directly to the oxidative stress-mediating properties of supportive glial cells.

Dataset Information

Reduced expression of miRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11.

Publications

Reduced expression of miRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11.

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