Disease relevance of CA12

• Reintroduced wild-type VHL strongly inhibited the overexpression of the CA12 gene in the parental renal cell carcinoma cell lines [1].
• The interplay between the functional pVHL and CA IX/CA XII in colorectal tumors seems rather complex and is not evident merely at the expression levels [2].
• Both CA9 and CA12 were strongly induced by hypoxia in a range of tumor cell lines [3].
• These findings indicate that expression of CA9, but not CA12, in tumors is associated with the presence of LN metastases and poorer prognosis [4].
• In comparison, CA XII was frequently expressed in normal breast tissues (89%), in DCIS (84%), and in invasive breast lesions (71%) [5].
• We further showed by Western blotting that anti-CA XII antibody recognized both isoforms in the glioblastoma cell lines, and we then evaluated the expression of CA XII in astrocytomas using immunohistochemistry and correlated the results with various clinicopathological and molecular factors [6].

High impact information on CA12

• By using GroEL-containing extracts from a DeltanifHDK strain of A. vinelandii CA12 along with FeMoco, Fe protein, and MgATP, we were able to supply all required proteins and/or factors and obtained a fully active reconstituted E146D nifH MoFe protein [7].
• We have determined the three-dimensional structure of the extracellular catalytic domain of human CA XII by x-ray crystallographic methods at 1.55-A resolution [8].
• Purification and kinetic analysis of recombinant CA XII, a membrane carbonic anhydrase overexpressed in certain cancers [9].
• The catalysis of CO(2) hydration by soluble CA XII has a maximal value of k(cat)/K(m) at 34 microM(-1) small middle dots(-1), which is similar to those of the membrane-associated CA IV and to soluble CA I [9].
• These observations suggest a role for CA XII in CO(2)/HCO(3)(-) homeostasis in cells in which it is normally expressed [9].

Chemical compound and disease context of CA12

• A spontaneous mutant derivative of Azotobacter vinelandii CA12 (delta nif HDK), which vanadium-dependent nitrogen fixation is not inhibited by molybdenum (A. vinelandii CARR), grows profusely on BNF-agar containing 1 microM Na2MoO4, alone or supplemented with 1 microM V2O5 [10].

Biological context of CA12

• We mapped CA12 and CA9 loci to chromosome bands 15q22 and 17q21.2 respectively, regions prone to amplification in some human cancers [1].
• Additional experiments are needed to define the role of CA IX and CA XII enzymes in the regulation of pH in the extracellular microenvironment and its potential impact on cancer cell growth [1].
• A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluorophenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII [11].
• The newly identified CA IX (previously called MN) and CA XII are related to cell proliferation and oncogenesis [12].
• Tn5 insertions were obtained in this clone and the mutagenized plasmid was used for marker exchange with A. vinelandii strain CA12 (delta nifHDK) to obtain Tn5 mutants [13].

Anatomical context of CA12

• Large-scale RNA differential display technology applied to these cell lines identified several differentially expressed genes, including an alpha carbonic anhydrase gene, termed CA12 [1].
• METHODS: CAIX and CAXII expression in 16 normal and 10 glaucomatous eyes, and in cultured non-pigmented ciliary epithelial cells (NPE) from normal and glaucoma eye donors was assessed by immunostaining [14].
• We show by immunohistochemistry that CA XII is expressed in the basolateral plasma membrane of epithelial cells of normal human endometrium [15].
• Identification of carbonic anhydrase XII as the membrane isozyme expressed in the normal human endometrial epithelium [15].
• Detergent-solubilized CA XII was isolated from human endometrium by inhibitor affinity chromatography and characterized by isoelectric focusing and Western blot as a polypeptide with a pI of 6 [15].

Associations of CA12 with chemical compounds

• In addition, topiramate and zonisamide were observed to behave as weak hCA XII inhibitors, while zonisamide was an effective hCA IX inhibitor (K(I) of 5.1 nM) [16].
• The full-length hCA XIV is an enzyme showing a medium-low catalytic activity, quite similar to that of hCA XII, with the following kinetic parameters at 20 degrees C and pH 7.5, for the CO2 hydration reaction: k(cat) = 3.12 x 10(5) s(-1) and k(cat)/K(M) = 3.9 x 10(7) M(-1) s(-1) [16].
• One study localizes CA XII to the distal nephron, while another places it in proximal tubules and inner medullary collecting ducts; confirmatory studies are needed for CA XII [17].
• These mutants exhibited a Nif- phenotype in the presence of vanadium, unlike CA12 which was Nif+ on vanadium-containing medium [13].
• The adenine auxotrophic mutants, which were readily isolated after UV irradiation of C. albicans CA12, were proved to be the segregants of mitotic recombination as they remained as diploid, not hemizygous or haploid, cells and were homozygous for ade2 [18].

Other interactions of CA12

• Membrane polarity is apical for CAXIV, basolateral for CAXII, and apical and basolateral for CAIV [19].
• In the epididymal duct, CA XII was detected only in sporadic cells, which also contained CA II, thus suggesting that they are apical mitochondria-rich cells [20].
• CA XII expression was present in 77 out of 103 (75%) cases and was associated with lower grade (P=0.001), positive estrogen receptor status (P<0.001), and negative epidermal growth factor receptor status (P<0.001) [21].
• RESULTS: On univariate Cox regression analysis certain markers were statistically significant predictors of survival, namely CA9 (p < 0.00001), p53 (p = 0.0072), gelsolin (p = 0.030), Ki67 (p = 0.036) and CA12 (p = 0.043) [22].
• These studies and initial results with docking to the crystal structure of the extracellular domain of hCAXII indicate that the STS sulphamate ester inhibitors should also be interesting candidates to pursue as inhibitors of CA isozymes that are over-expressed in human tumours [23].

Analytical, diagnostic and therapeutic context of CA12

• Using Northern blot analysis and immunostaining with specific antibodies we analyzed the expression of CA9 and CA12 genes and their products in a large sample of cancer cell lines, fresh and archival tumor specimens, and normal human tissues [24].
• CA9 expression in the primary tumors was significantly associated with LN metastasis (P = 0.03) and poorer disease-free survival (relative risk, 6.1; 95% confidence interval, 1.3-28.3, P = 0.02, multivariate analysis), whereas CA12 expression did not show such a relationship [4].
• CA9/CA12 expression was evaluated histochemically in primary cervical cancer tissues of 73 patients who underwent laparoscopic LN staging and two patients with clinical staging before definitive radiotherapy at the National Cancer Center, Korea. We also evaluated CA9 expression in 33 patients with pathologically confirmed metastatic LN [4].
• The CA XII gene was mapped by using fluorescence in situ hybridization to 15q22 [25].
• CA XII expression was studied by immunohistochemistry in a series of 103 cases of invasive breast cancer and any association with recognised prognostic factors or relation with the outcome was examined [21].

References