Immunohistochemistry of Carbonic Anhydrase Isozyme IX (MN/CA IX) in Human Gut Reveals Polarized Expression in the Epithelial Cells with the Highest Proliferative Capacity

Abstract

SUMMARY MN/CA IX is a recently discovered member of the carbonic anhydrase (CA) gene family that has been identified in the plasma membranes of certain tumor and epithelial cells and found to promote cell proliferation when transfected into NIH3T3 cells. This study presents localization of MN/CA IX in human gut and compares its distribution to those of CA I, II, and IV, which are known to be expressed in the intestinal epithelium. The specificity of the monoclonal antibody for MN/CA IX was confirmed by Western blots and immunostaining of COS-7 cells transfected with MN/CA IX cDNA. Immunohistochemical stainings of human gut revealed prominent polarized staining for MN/CA IX in the basolateral surfaces of the enterocytes of duodenum and jejunum, the reaction being most intense in the crypts. A moderate reaction was also seen in the crypts of ileal mucosa, whereas the staining became generally weaker in the large intestine. The results indicate isozyme-specific regulation of MN/CA IX expression along the cranial-caudal axis of the human gut and place the protein at the sites of rapid cell proliferation. The unique localization of MN/CA IX on the basolateral surfaces of proliferating crypt enterocytes suggests that it might serve as a ligand or a receptor for another protein that regulates intercellular communication or cell proliferation. Furthermore, MN/CA IX has a completely conserved active site domain of CAs suggesting that it could also participate in carbon dioxide/bicarbonate homeostasis. (J Histochem Cytochem 46:497-504, 1998)

Expression of a Novel Transmembrane Carbonic Anhydrase Isozyme XII in Normal Human Gut and Colorectal Tumors

“…Based on the present investigations and earlier ones, several CA isozymes can be said to be expressed in the human gut, each of them manifesting a characteristic distribution pattern with respect to segmental, cellular, and subcellular localization. 18 The schematic model for CA isozyme expression in the human jejunum and ascending colon shown in Figure 5 indicates that the enterocytes of the colonic surface epithelial cuff appear to contain CA I, II, IV, and XII. The existence of at least four CA isozymes in this region (CA I and II in the cytosol, CA IV in the apical brush border, and CA XII in the basolateral plasma membrane) makes it difficult to define the individual role of each, but their cellular distribution suggests an important role in the absorption of water, which is the major physiological function of the colon.…”

Expression of Carbonic Anhydrase IX in Astrocytic Tumors Predicts Poor Prognosis

“…The monoclonal M75 antibody against human CA IX has been described previously (13). The antibody has been characterized for specificity and it has shown no cross-reactivity with other CAs (14). The CA IX enzyme was immunostained by the biotin-streptavidin complex method from the multitissue blocks by following this procedure: (a) pretreatment of the sections with undiluted cow colostral whey (Biotop Oy, Oulu, Finland) for 30 minutes and washed in PBS, (b) incubation for 1 hour with M75 antibody (1:10) in 1% bovine serum albumin-PBS, (c) incubation for 1 hour in biotinylated goat anti-mouse IgG (Zymed Laboratories, Inc., South San Francisco, CA) diluted 1:300 in 1% bovine serum albumin-PBS, and then (d) incubation for 30 minutes with peroxidaseconjugated streptavidin (Zymed) diluted 1:500 in PBS; (e) thereafter, incubation was done for 2 minutes in DAB solution containing 9 mg 3,3V -diaminobenzidine tetrahydrochloride (Fluka, Buchs, Switzerland) in 15 mL PBS and 5 AL 30% H 2 O 2 .…”

Therapeutic Mechanism and Efficacy of the Antibody–Drug Conjugate BAY 79-4620 Targeting Human Carbonic Anhydrase 9

“…4,9), and, to a lesser degree, breast carcinomas (4,10). By contrast, the expression of CAIX on normal tissues is largely restricted to the apical surface of cells of the stomach, bile duct mucosa (4,11), and small intestine (4,12). The extracellular domain of this type I transmembrane protein comprises both a proteoglycan domain implicated in cell adhesion through homotypic interaction (13) and the carbonic anhydrase domain that catalyzes the reversible hydration of carbon dioxide to bicarbonate and protons (14) and is involved in the regulation of the pH within the tumor environment (15).…”