title: Quantification of carbonic anhydrase IX expression in serum and tissue of renal cell carcinoma patients using enzyme-linked immunosorbent assay: prognostic and diagnostic potentials.
abstract: OBJECTIVE
  To validate enzyme-linked immunosorbent assay (ELISA) as an accurate and objective method to measure carbonic anhydrase IX (CAIX) expression in RCC tissue specimens and to also investigate the diagnostic and prognostic utility of serum CAIX levels. Recent studies found protein levels of CAIX, quantified using immunohistochemistry, correlated with clinical outcomes and therapeutic response to immunotherapy in advanced stage clear cell renal cell carcinoma (CCRCC).
  
  
  METHODS
  A CAIX ELISA kit was used to measure the CAIX levels in the serum and tissue of 21 CCRCCs and 19 non-CCRCCs. CAIX immunohistochemical stains were performed on the corresponding formalin fixed, paraffin embedded tumor tissues.
  
  
  RESULTS
  Tissue CAIX levels measured by ELISA highly correlated with the CAIX levels detected by immunohistochemistry (Pearson correlation coefficient = .802, P <.001). The CCRCC tumor tissue had significantly higher CAIX levels than non-CCRCC tissue (77 023 vs 938 pg/mL, P <.001) detected by ELISA. Serum CAIX levels in CCRCC patients were significantly higher than in non-CCRCC patients (126.1 vs 2.1 pg/mL, P = .013). The serum CAIX levels detected by ELISA correlated with the tumor size in CCRCC patients (Pearson correlation coefficient = .498, P = .036).
  
  
  CONCLUSIONS
  ELISA provides a quantitative and objective method to measure CAIX levels in renal tumors. The tissue CAIX levels measured with ELISA highly correlate with the results obtained with the standard immunohistochemistry. Serum CAIX levels are significantly higher in CCRCC than in non-CCRCC and may aid the differential diagnosis of RCC. Serum CAIX levels also correlate with the tumor size in CCRCC patients.
authors: Department of Immunology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors: Grace X
authors: GX
authors: Zhou
authors: Joanna
authors: J
authors: Ireland
authors: Patricia
authors: P
authors: Rayman
authors: James
authors: J
authors: Finke
authors: Ming
authors: M
authors: Zhou
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000032:analysis* / Q000096:biosynthesis* / Q000097:blood; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000032:analysis* / Q000096:biosynthesis* / Q000097:blood; D002292:Carcinoma, Renal Cell / Q000097:blood / Q000737:chemistry / Q000175:diagnosis* / Q000201:enzymology*; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000097:blood / Q000737:chemistry / Q000175:diagnosis* / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D055815:Young Adult
chemical_list: D000951:Antigens, Neoplasm; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases