title: Reduced expression of miRNA-27a modulates cisplatin resistance in bladder cancer by targeting the cystine/glutamate exchanger SLC7A11.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: Authors' Affiliations: Academic Unit of Molecular Oncology and Academic Urology Unit, University of Sheffield, Sheffield, United Kingdom; Nuffield Department of Surgery, University of Oxford, Oxford, United Kingdom; and Department of Pathology, University of Erlangen, Germany.
authors: Ross M
authors: RM
authors: Drayton
authors: Ewa
authors: E
authors: Dudziec
authors: Stefan
authors: S
authors: Peter
authors: Simone
authors: S
authors: Bertz
authors: Arndt
authors: A
authors: Hartmann
authors: Helen E
authors: HE
authors: Bryant
authors: James Wf
authors: JW
authors: Catto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D027182:Amino Acid Transport System y+ / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000008:administration & dosage; D018736:DNA Adducts / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000096:biosynthesis / Q000235:genetics*; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology
chemical_list: D027182:Amino Acid Transport System y+; D018736:DNA Adducts; C531388:MIRN27 microRNA, human; D035683:MicroRNAs; C118895:SLC7A11 protein, human; C057270:cisplatin-DNA adduct; D002945:Cisplatin