title: Differential expression of KAI1 metastasis suppressor protein in renal cell tumor histological subtypes.
abstract: OBJECTIVE
  The similar appearance of renal tumor histological subtypes can complicate differential diagnoses. This problem is most notable for the chromophobe subtype of renal cell carcinoma, which can be histologically indistinguishable from oncocytoma with investigational molecular markers failing to provide reliable differentiation. KAI1 is a metastasis suppressor gene whose expression correlates inversely with the metastatic potential of most solid tumor cancer types. We tested the hypothesis that KAI1 is differentially expressed among renal tumor histological subtypes.
  
  
  METHODS
  Immunohistochemical staining for KAI1 protein was performed in 152 nephrectomy specimens, including 48 clear cell, 35 papillary and 31 chromophobe renal cell carcinoma samples, 28 oncocytomas and 10 tumor-free kidneys. Staining was scored as none/minimal, low, moderate or high. KAI1 mRNA levels were compared by quantitative reverse transcriptase-polymerase chain reaction in an additional 22 chromophobe renal cell carcinoma and oncocytoma samples.
  
  
  RESULTS
  In all 10 tumor-free kidneys KAI1 protein was detected exclusively in distal tubule cell membranes. Of the tumor specimens KAI1 protein was absent in all papillary renal cell carcinoma specimens. It was present in only 1 of 48 clear cell renal cell carcinomas (2%) and 2 of 28 oncocytomas (7%) but only at low levels. In contrast, 27 of 31 chromophobe renal cell carcinoma specimens (87%) expressed KAI1 protein, most at moderate or high levels. The diagnostic accuracy of KAI1 immunostaining for discerning chromophobe renal cell carcinoma from oncocytoma was 90% with similar results observed at the RNA level.
  
  
  CONCLUSIONS
  KAI1 is an accurate biomarker for chromophobe renal cell carcinoma that may aid in the diagnostic differentiation of chromophobe renal cell carcinoma from oncocytoma. It remains to be determined whether KAI1 expression contributes to the low metastatic potential of chromophobe renal cell carcinoma.
authors.affiliation: Department of Urology, New York Presbyterian Hospital-Weill Medical College of Cornell University, New York, New York, USA. erk9005@nyp.org
authors.forename: E C
authors.initials: EC
authors.lastname: Kauffman
authors.forename: D A
authors.initials: DA
authors.lastname: Barocas
authors.forename: Y T
authors.initials: YT
authors.lastname: Chen
authors.forename: X J
authors.initials: XJ
authors.lastname: Yang
authors.forename: D S
authors.initials: DS
authors.lastname: Scherr
authors.forename: J J
authors.initials: JJ
authors.lastname: Tu
mesh_terms: D018249:Adenoma, Oxyphilic / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D014408:Biomarkers, Tumor / Q000235:genetics; D001707:Biopsy, Needle; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D008297:Male; D009392:Nephrectomy; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011379:Prognosis; D012016:Reference Values; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity
chemical_list: C076266:ANOS1 protein, human; D014408:Biomarkers, Tumor; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins