title: Carbonic anhydrase IX is a marker of hypoxia and correlates with higher Gleason scores and ISUP grading in prostate cancer.
abstract: BACKGROUND
  Carbonic anhydrase IX is a member of α-carbonic anhydrases that is preferentially expressed in solid tumors. It enables bicarbonate transport across the plasma membrane, neutralizing intracellular pH and conferring to cancer cells a survival advantage in hypoxic/acidic microenvironments. Overexpression of carbonic anhydrase IX in cancer tissues is regulated by hypoxia inducible factor 1α - mediated transcription and the enzyme is considered a marker of tumor hypoxia and poor outcome. The role of carbonic anhydrase IX in prostate cancer has not been fully clarified and controversy has arisen on whether this enzyme is overexpressed in hypoxic prostate cancer tissues.
  
  
  METHODS
  We analyzed the expression of carbonic anhydrase IX and hypoxia inducible factor 1α in two prostate cancer cell lines, LNCaP and PC-3, and in 110 cancer biopsies, by western blotting and immunocyto/histochemistry.
  
  
  RESULTS
  In LNCaP and PC-3 cells, carbonic anhydrase IX was mostly cytoplasmic/nuclear, with very limited membrane localization. Nuclear staining became stronger under hypoxia. When we analyzed carbonic anhydrase IX expression in human prostate cancer biopsies, we found that protein staining positively correlated with hypoxia inducible factor 1α and with Gleason pattern and score, as well as with the novel grading system proposed by the International Society of Urological Pathology for prostate cancer. Once more, carbonic anhydrase IX was mainly cytoplasmic in low grade carcinomas, whereas in high grade tumors was strongly expressed in the nucleus of the neoplastic cell. An association between carbonic anhydrase IX expression level and the main clinic-pathological features involved in prostate cancer aggressiveness was identified.
  
  
  CONCLUSIONS
  There was a statistically significant association between carbonic anhydrase IX and hypoxia inducible factor 1α in prostate cancer tissues, that identifies the enzyme as a reliable marker of tumor hypoxia. In addition, carbonic anhydrase IX expression positively correlated with prostate cancer grading and staging, and with outcome, suggesting that the protein may be an independent prognosticator for the disease. The nuclear translocation of the enzyme in hypoxic cancer cells may epitomize a biological switch of the tumor towards a less favorable phenotype.
authors.affiliation: Department of Medical Biotechnology, Section of Pathology, University of Siena, Via delle Scotte 6, 53100, Siena, Italy. maradot@libero.it.
authors.forename: Maria Raffaella
authors.initials: MR
authors.lastname: Ambrosio
authors.affiliation: Department of Clinical and Experimental Medicine, Research Unit of Medicine of Ageing, University of Florence, Florence, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Di Serio
authors.affiliation: Department of Clinical Physiopathology, Endocrine Unit, University of Florence, Florence, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Danza
authors.affiliation: Department of Medical Biotechnology, Section of Pathology, University of Siena, Via delle Scotte 6, 53100, Siena, Italy.|Section of Pathology, Ospedale di Circolo di Busto Arsizio, Presidio Ospedaliero di Saronno, Saronno, Italy.
authors.forename: Bruno Jim
authors.initials: BJ
authors.lastname: Rocca
authors.affiliation: Department of Medical Biotechnology, Section of Pathology, University of Siena, Via delle Scotte 6, 53100, Siena, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ginori
authors.affiliation: Center for Molecular Medicine, Maine Medical Center Research Institute (MMCRI), Scarborough, ME, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Prudovsky
authors.affiliation: Department of Clinical and Experimental Medicine, Research Unit of Medicine of Ageing, University of Florence, Florence, Italy.
authors.forename: Niccolò
authors.initials: N
authors.lastname: Marchionni
authors.affiliation: Department of Medicine, Science and Neurosciences, University of Siena, Siena, Italy.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Del Vecchio
authors.affiliation: Department of Clinical and Experimental Medicine, Research Unit of Medicine of Ageing, University of Florence, Florence, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tarantini
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001706:Biopsy; D000071231:Carbonic Anhydrase IX / Q000378:metabolism*; D002277:Carcinoma / Q000175:diagnosis / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D000860:Hypoxia / Q000175:diagnosis / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D011467:Prostate / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000378:metabolism*
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX
keywords: Carbonic anhydrase; Gleason score; HIF-1α; Hypoxia; Prostate cancer