title: Folliculin deficient renal cancer cells show higher radiosensitivity through autophagic cell death.
abstract: OBJECTIVE
  Mutations in the FLCN gene are responsible for fibrofolliculoma, pulmonary and renal cysts, and renal cell carcinoma in patients with Birt-Hogg-Dubé syndrome. To explore therapeutic approaches to renal cell carcinoma in patients with Birt-Hogg-Dubé syndrome we investigated the anticancer effects of irradiation on folliculin deficient renal cancer cells.
  
  
  METHODS
  Folliculin deficient (UOK257 and ACHN-5968) and folliculin expressing (UOK257-2 and ACHN-sc) cell lines were used in this study. Clonogenic assays were used to determine the radiosensitivity of folliculin deficient and expressing renal cell carcinoma cells. Apoptosis was detected in these cells by DAPI and TUNEL assays after irradiation. Monodansylcadaverine analysis, GFP-LC3 assay and Western blot were performed to monitor the autophagic process.
  
  
  RESULTS
  Folliculin deficient cells were more sensitive to irradiation than their folliculin expressing counterparts. The enhanced effects of irradiation on folliculin deficient cells were mediated by increased autophagy but not by apoptosis. An increased Beclin 1 protein level and an activated mitogen-activated protein kinase pathway were identified as the key regulators of increased autophagy in these folliculin deficient cells. Inhibiting autophagy with 3-methyladenine or beclin 1 siRNA obviously increased radioresistance in folliculin deficient cells. Moreover, irradiation combined with autophagic inducer rapamycin significantly increased autophagy and radiosensitivity in folliculin deficient renal cell carcinoma cells.
  
  
  CONCLUSIONS
  Findings suggest that folliculin deficient renal cell carcinoma cells are highly sensitive to irradiation due to increased autophagic cell death, unlike other types of renal cell carcinoma. Irradiation plus autophagy inducers, eg rapamycin, might be a potentially more effective therapeutic approach to folliculin deficient renal cell carcinoma.
authors.affiliation: Minimally Invasive Urology Center, Provincial Hospital Affiliated to Shandong University, Jinan, People's Republic of China; Department of Urology, University of Rochester Medical Center, Rochester, New York.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Urology, University of Rochester Medical Center, Rochester, New York.
authors.forename: Shuhui
authors.initials: S
authors.lastname: Si
authors.affiliation: Department of Urology, University of Rochester Medical Center, Rochester, New York.
authors.forename: Sue
authors.initials: S
authors.lastname: Schoen
authors.affiliation: Minimally Invasive Urology Center, Provincial Hospital Affiliated to Shandong University, Jinan, People's Republic of China.
authors.forename: Xun-Bo
authors.initials: XB
authors.lastname: Jin
authors.affiliation: Department of Urology, University of Rochester Medical Center, Rochester, New York. Electronic address: jindong_chen@urmc.rochester.edu.
authors.forename: Jindong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Urology, University of Rochester Medical Center, Rochester, New York; Department of Pathology, University of Rochester Medical Center, Rochester, New York; Wilmot Cancer Center, University of Rochester Medical Center, Rochester, New York. Electronic address: guan_wu@urmc.rochester.edu.
authors.forename: Guan
authors.initials: G
authors.lastname: Wu
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D001343:Autophagy; D058249:Birt-Hogg-Dube Syndrome; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020287:In Situ Nick-End Labeling; D007680:Kidney Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics*
chemical_list: C476078:FLCN protein, human; D011518:Proto-Oncogene Proteins; D012334:RNA, Neoplasm; D025521:Tumor Suppressor Proteins
keywords: Birt-Hogg-Dube syndrome; autophagy; carcinoma; estrone; kidney; renal cell