title: Birt-Hogg-Dubé renal tumors are genetically distinct from other renal neoplasias and are associated with up-regulation of mitochondrial gene expression.
abstract: BACKGROUND
  Germline mutations in the folliculin (FLCN) gene are associated with the development of Birt-Hogg-Dubé syndrome (BHDS), a disease characterized by papular skin lesions, a high occurrence of spontaneous pneumothorax, and the development of renal neoplasias. The majority of renal tumors that arise in BHDS-affected individuals are histologically similar to sporadic chromophobe renal cell carcinoma (RCC) and sporadic renal oncocytoma. However, most sporadic tumors lack FLCN mutations and the extent to which the BHDS-derived renal tumors share genetic defects associated with the sporadic tumors has not been well studied.
  
  
  METHODS
  BHDS individuals were identified symptomatically and FLCN mutations were confirmed by DNA sequencing. Comparative gene expression profiling analyses were carried out on renal tumors isolated from individuals afflicted with BHDS and a panel of sporadic renal tumors of different subtypes using discriminate and clustering approaches. qRT-PCR was used to confirm selected results of the gene expression analyses. We further analyzed differentially expressed genes using gene set enrichment analysis and pathway analysis approaches. Pathway analysis results were confirmed by generation of independent pathway signatures and application to additional datasets.
  
  
  RESULTS
  Renal tumors isolated from individuals with BHDS showed distinct gene expression and cytogenetic characteristics from sporadic renal oncocytoma and chromophobe RCC. The most prominent molecular feature of BHDS-derived kidney tumors was high expression of mitochondria-and oxidative phosphorylation (OXPHOS)-associated genes. This mitochondria expression phenotype was associated with deregulation of the PGC-1α-TFAM signaling axis. Loss of FLCN expression across various tumor types is also associated with increased nuclear mitochondrial gene expression.
  
  
  CONCLUSIONS
  Our results support a genetic distinction between BHDS-associated tumors and other renal neoplasias. In addition, deregulation of the PGC-1α-TFAM signaling axis is most pronounced in renal tumors that harbor FLCN mutations and in tumors from other organs that have relatively low expression of FLCN. These results are consistent with the recently discovered interaction between FLCN and AMPK and support a model in which FLCN is a regulator of mitochondrial function.
authors.affiliation: Laboratory of Computational Biology, Van Andel Research Institute, Grand Rapids, MI, USA.
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Klomp
authors.forename: David
authors.initials: D
authors.lastname: Petillo
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Niemi
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Dykema
authors.forename: Jindong
authors.initials: J
authors.lastname: Chen
authors.forename: Ximing J
authors.initials: XJ
authors.lastname: Yang
authors.forename: Annika
authors.initials: A
authors.lastname: Sääf
authors.forename: Peter
authors.initials: P
authors.lastname: Zickert
authors.forename: Markus
authors.initials: M
authors.lastname: Aly
authors.forename: Ulf
authors.initials: U
authors.lastname: Bergerheim
authors.forename: Magnus
authors.initials: M
authors.lastname: Nordenskjöld
authors.forename: Sophie
authors.initials: S
authors.lastname: Gad
authors.forename: Sophie
authors.initials: S
authors.lastname: Giraud
authors.forename: Yves
authors.initials: Y
authors.lastname: Denoux
authors.forename: Laurent
authors.initials: L
authors.lastname: Yonneau
authors.forename: Arnaud
authors.initials: A
authors.lastname: Méjean
authors.forename: Viorel
authors.initials: V
authors.lastname: Vasiliu
authors.forename: Stéphane
authors.initials: S
authors.lastname: Richard
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: MacKeigan
authors.forename: Bin T
authors.initials: BT
authors.lastname: Teh
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Furge
mesh_terms: D018249:Adenoma, Oxyphilic / Q000235:genetics; D058249:Birt-Hogg-Dube Syndrome / Q000235:genetics*; D002292:Carcinoma, Renal Cell / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D050259:Genes, Mitochondrial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000378:metabolism; D010085:Oxidative Phosphorylation; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011518:Proto-Oncogene Proteins / Q000235:genetics; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; C476078:FLCN protein, human; D006360:Heat-Shock Proteins; D024101:Mitochondrial Proteins; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011518:Proto-Oncogene Proteins; C499631:TFAM protein, human; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins