Sera of patients with spontaneous tumour regression and elevated anti‐CA I autoantibodies change the gene expression of ECM proteins

Spontaneous tumour regression after high‐dose therapy and autologous stem cell transplantation is associated with the aplastic anaemia‐like syndrome and the presence of polyclonal autoantibodies against carbonic anhydrase I (CA I). When tumour cells were grown in vitro in the presence of patients’ sera positive for anti‐CA I autoantibodies, their morphological pattern was altered. These changes were accompanied by modifications in the gene expression profile. We observed downregulation of genes of the basal lamina assembly (collagen type IV alpha 4, the laminin subunit gamma 2), the extracellular matrix (collagen type I alpha 1), the cytoskeleton (keratin 14 type I), the collagen triple helix repeat containing 1 and the proto‐oncogene WNT7B. On the other hand, the expression of the CA 1 gene was increased in the tumour cells. It was also noticed that the presence of anti‐CA I autoantibodies did not impair tumour cell proliferation and cell viability in vitro. These findings were observed only in the presence of patients’ sera positive for anti‐CA I autoantibodies.     

Antigen levels of urokinase-type plasminogen activator receptor and its gene polymorphism related to microvessel density in colorectal cancer

We determined the distribution of genotypes and frequencies of alleles of the (CA)(n) repeat polymorphism in intron 3 of the urokinase plasminogen activator receptor (uPAR) gene, uPAR antigen levels and microvessel density (MVD) in tumour and distant mucosa samples from 52 patients with colorectal cancer. The uPAR level was higher for patients with high MVD comparing to patients with lower MVD which may suggest that uPAR can be correlated with progression of colorectal cancer. The significant relationship between the high MVD and uPAR antigen level appeared to be independent of the (CA)(n) repeat polymorphism because no differences in the level of uPAR antigen between carriers of alleles were found. The received results, indicate that uPAR might be considered as a target in colorectal cancer patients' therapy.     

Carbonic anhydrase inhibitors: design of thioureido sulfonamides with potent isozyme II and XII inhibitory properties and intraocular pressure lowering activity in a rabbit model of glaucoma

A new series of thioureido-substituted sulfonamides were prepared by reacting 4-isothiocyanato- or 4-isothiocyanatoethyl-benzenesulfonamide with amines, hydrazines, or amino acids bearing moieties that can lead to an enhanced hydrosolubility, such as 2-dimethylamino-ethylamine, fluorine-containing aromatic amines/hydrazines, an aminodiol, heterocyclic polyamines (derivatives of morpholine and piperazine), 4-aminobenzoic acid, or natural amino acids (Gly, Cys, Asn, Arg, and Phe). The new compounds showed good inhibitory properties against three physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isozymes, with K(I)s in the range of 24-324 nM against the cytosolic isoform CA I, of 6-185 nM against the other cytosolic isozyme CA II, and of 1.5-144 nM against the transmembrane isozyme CA XII. Some of the new derivatives were also very effective in reducing elevated intraocular pressure in hypertensive rabbits as a glaucoma animal model. Considering that this is the first study in which potent CA II/CA XII inhibitors are designed and investigated in vivo, it may be assumed that the target isozymes of the antiglaucoma sulfonamides are indeed the cytosolic CA II and the transmembrane CA XII.     

Pathogenic roles of cardiac autoantibodies in dilated cardiomyopathy

Whether autoimmunity could cause dilated cardiomyopathy (DCM) was disputed for more than half a century. Autoantibodies against various cardiac antigens have been found in the sera of patients with DCM but none of these autoantibodies has been shown to have a substantial role in the development of DCM. It was recently reported that the injection of autoantibodies against cardiac troponin I (cTnI) can induce DCM in normal mice. This observation showed that autoantibodies can cause DCM and put an end to the controversy. Clinical trials of immunoglobulin-adsorption therapy for DCM have already started in Germany and the results seem promising. Here, we discuss the recent findings and possibilities of immunoglobulin-adsorption therapy for this deadly disease.     

Epitope mapping of human aromatic L-amino acid decarboxylase

Autoimmune polyendocrine syndrome type I (APS I) is a rare hereditary condition considered a model disease for organ specific autoimmunity. A wide range of autoantibodies targeting antigens present in the affected organs have been identified. Autoantibodies against aromatic L-amino acid decarboxylase (AADC) are present in about 50% of APS I patients. In order to increase our understanding of autoantibody specificity in APS I, the aim of the present study was to localize target regions on AADC recognized by sera from APS I patients. Using several complementing strategies, we have shown that autoantibodies against AADC mainly recognize conformational epitopes. The major antigenic determinants were detected N-terminally to amino acid residue 237. Replacement of amino acids 227-230 (ERDK) with alanine residues reduced the reactivity towards AADC by >80% in all patient sera tested, suggesting that amino acids 227-230 are an important part of an immunodominant epitope.     

Autoantibodies against the tumour-associated antigen GA733-2 in patients with colorectal carcinoma

The tumour-associated antigen (TAA) GA733-2 is expressed as a non-secreted surface molecule on the majority of human colorectal carcinoma cells. The antigen has been used as a target for passive and active immunotherapy during the last decade. To determine the incidence of autoantibodies against this antigen, sera from 1068 patients with colorectal carcinoma were analysed for naturally occurring IgG antibodies against the baculovirus-produced GA733-2E protein. A total of 14.5% of the patients had IgG antibodies against the antigen. In 519 patients, sera were collected at the time of diagnosis and 15% of those patients had anti-GA733-2E IgG antibodies. There was a tendency to a higher frequency of patients with antibodies among those in the advanced Dukes stages: 11% in stage A and 32% in stage D respectively (P = 0.06). Antibodies could be detected for up to 10 years after the diagnosis. Patients with Crohn's disease or colitis ulcerosa (n = 20) did not elicit anti-GA733-2E antibodies. No healthy control donor (n = 45) had detectable antibodies against the antigen. The specificity of GA733-2E-reactive serum IgG was indicated by significant inhibition of mAb17-1A (originally used to define GA733-2) binding to the GA733-2E antigen. Sera of positive patients bound to the GA733-2-expressing human colorectal carcinoma cell line, SW948. No significant correlation was found between the presence of antibodies and survival in the present patient population. However, the high incidence of autoantibodies against this tumour antigen in colorectal carcinoma patients confirms its antigenicity in humans and supports the use of the GA733-2 antigen as a target for immunotherapy. Received: 25 May 1998 / Accepted: 26 November 1998     

Metronidazole-coumarin conjugates and 3-cyano-7-hydroxy-coumarin act as isoform-selective carbonic anhydrase inhibitors

Reaction of 6-/7-hydroxycoumarin with metronidazole afforded conjugates which incorporate two interesting chemotypes which may inhibit carbonic anhydrases (CAs, EC 4.2.1.1) due to the presence of the coumarin moiety and possess radiosensitizing effects due to the presence of the nitroazole. Another dual action compound, which may act both as CA inhibitor as well as monocarboxylate transporter inhibitor, is 3-cyano-7-hydroxy-coumarin. These compounds have been investigated as inhibitors of 11 human CA isoforms. Submicromolar inhibition was observed against hCA VA, hCA VB, hCA VI, hCA VII, hCA IX, hCA XII and hCA XIV, whereas isoforms hCA I, II and XIII were not inhibited by these compounds. These coumarins thus act as isoform-selective CA inhibitors with the possibility to target isoforms involved in pathologies such as obesity (CA VA/VB) or cancer (CA IX and XII) without inhibiting the physiologically dominant, highly abundant hCA I and II.     

Cytochrome P450 enzymes and UDP-Glucuronosyltransferases as hepatocellular autoantigens

Cytochromes P450 and UDP-Glucuronosyltransferases (UGT) are targets of microsomal autoantibodies in liver and kidney (LKM). LKM autoantibodies are observed in autoimmune hepatitis, in some patients with viral hepatitis, drug-induced hepatitis and autoimmune hepatitis as disease component of the autoimmune polyglandulars syndrome type 1 (APS-1). In autoimmune hepatitis LKM antibodies are markers of autoimmune hepatitis type 2. The major target of LKM-1 antibodies is cytochrome P450 2D6; a second less frequent target was the described UGTs of family 1. In autoimmune hepatitis LKM-1 autoantibodies are usually directed against small linear epitopes. LKM autoantibodies are also associated with infection with hepatitis viruses C and D. In hepatitis C about 1–2% of patients develop LKM-1 autoantibodies. About 60% of these autoantibodies are conformation dependent. The presence of LKM autoantibodies in hepatitis C may be associated with an increased risk in interferon treatment. LKM-3 autoantibodies are found in about 8% of patients with hepatitis D and are directed against conformational epitopes. Patients treated with certain drugs may develop drug induced hepatitis. In hepatitis induced by tienilic acid, tienilic acid is activated by and covalently bound to cytochrome P450 2C9. Activation of the immune system results in the formation of autoantibodies against cytochrome P450 2C9 (LKM-2) and infiltration of the liver with immune cells. A similar mechanism has been described for dihydralazine induced hepatitis, where autoantibodies are directed against P450 1A2 (LM). Autoantibodies directed against cytochrome P450 1A2 also are found in patients suffering from hepatitis as a disease component of APS-1.Abbreviations AIH autoimmune hepatitis - APS1 autoimmune polyendocrine syndrome type 1 - APS-1 autoimmune polyglandular syndrome type 1 - LKM microsomal autoantibodies in liver and kidney - HSV-1 herpes simplex virus type 1 - UGT UDP-glucuronosyltransferases     

Identification of tyrosine hydroxylase as an autoantigen in autoimmune polyendocrine syndrome type I

Patients with the autosomal recessively inherited autoimmune polyendocrine syndrome type I (APS I) have autoantibodies directed against several endocrine and nonendocrine organs. In this study a new autoantigen related to this syndrome, tyrosine hydroxylase, was identified in sera from patients with alopecia areata through immunoscreening of a scalp cDNA library. Immunoreactivity against in vitro expressed tyrosine hydroxylase was found in 41 (44%) of the 94 APS I patients studied and this reactivity correlated with the presence of alopecia areata (P = 0.02). These findings further stress the importance of enzymes involved in neurotransmitter biosynthesis as important immune targets in APS I.     

The specificity of disease-associated anti-fibrillarin autoantibodies compared with that of HgCl2-induced autoantibodies

Autoantibodies against nucleolar components are a common serological feature of patients suffering from scleroderma, a collagen vascular autoimmune disease. An important target of these autoantibodies is a protein with an apparent molecular weight of 36 kDa and a pI value of 8.5, located in the dense fibrillar component of the nucleolus and therefore termed fibrillarin. Animal models in which abundant anti-nucleolar antibodies appear spontaneously have not yet been described; however, high levels of anti-fibrillarin antibodies can be induced by treating susceptible strains of mice with sub-toxic amounts of mercuric chloride. In this study, we have analysed the specificity of anti-fibrillarin autoantibodies of human and murine origin. Our results suggest that both species have similar, if not identical conformational epitopes that are the target of anti-fibrillarin autoantibodies; these epitopes require the presence of a 30-kDa fragment of the fibrillarin molecule. Post-translational modifications such as the dimethylation of arginines in the N terminus of the protein are not essential for antibody recognition.Abbreviations ANA Antinuclear autoantibodies - ANolA Antinucleolar autoantibodies - snoRNA small nucleolar RNA - snoRNP small nucleolar ribonucleoprotein     

Carbonic anhydrase inhibitors: inhibition of cytosolic/tumor-associated isoforms I, II, and IX with iminodiacetic carboxylates/hydroxamates also incorporating benzenesulfonamide moieties

The synthesis of a new class of sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors (CAIs), also possessing carboxylate/hydroxamate moieties in their molecule, is reported. These compounds may act on dual antitumor targets, the tumor-associated CA isozymes (CA IX) and some matrix metalloproteinases (MMPs). The compounds were prepared by an original method starting from iminodiacetic acid, and assayed as inhibitors of three isozymes, hCA I, II (cytosolic), and IX (transmembrane). The new derivatives showed weak inhibitory activity against isozyme I (K(I)s in the range of 95-8300 nM), were excellent to moderate CA II inhibitors (K(I)s in the range of 8.4-65 nM), and very good and selective CA IX inhibitors (K(I)s in the range of 3.8-26 nM). The primary sulfonamide moiety is a better zinc-binding group in the design of CAIs as compared to the carboxylate/hydroxamate one, but the presence of hydroxamate functionalities in the molecule of CAIs leads to selectivity for the tumor-associated isozyme IX over the ubiquitous, cytosolic isoform II.     

Autoantibodies against serotoninergic 5-HT(4) receptor in patients with heart failure

Serotoninergic 5-HT(4) receptors have been detected in several tissues including the heart. An autoimmune mechanism may underline the pathogenesis of heart failure. The aim of this work was to look for autoantibodies to the 5-HT(4) receptor in patients with heart failure. We looked for the presence of autoantibodies against 5-HT(4) receptor as well as angiotensin II type (AT1), β(1)-adrenoceptor, and muscarinic M2 receptors in the sera of 176 patients with heart failure (female: n=96, male: n=80) and in 108 controls (female: n=69; male: n=39). The prevalence of 5-HT(4) receptor autoantibodies was 18.8% (n=33) in the group of patients with heart failure and 4.6% (n=5) in the control group (p<0.002). The prevalence of autoantibodies against AT1 was 1.7 (n=3), β(1)-adrenoreceptor 0.6 (n=1), and muscarinic-receptor M2 4.2 (n=5). Female patients with diabetes and heart failure had a positive trend (p=0.07) to the presence of 5-HT(4) receptor autoantibodies. In the group of female heart failure patients we found a significant correlation with the presence of coronary heart disease (p=0.05). The clinical relevance of 5-HT(4) receptor autoantibodies has to be further studied. The prevalence of 5-HT(4) receptor autoantibodies was highly significant in patients with chronic heart failure. It was also a significant correlation between these autoantibodies and the female subgroup with coronary heart disease. It is conceivable that the increased prevalence of autoantibodies against the 5-HT(4) receptor in patients with heart failure is more than just an epiphenomenon.     

Plasmatic carbonic anhydrase IX as a diagnostic marker for clear cell renal cell carcinoma

Carbonic anhydrase (CA, EC 4.2.1.1) IX is regarded as a tumour hypoxia marker and CA inhibitors have been proposed as a new class of antitumor agents, with one such agent in Phase II clinical trials. The expression of some CAs, in particular the isoforms CA IX and CA XII, has been correlated with tumour aggressiveness and progression in several cancers. The aim of this study was to evaluate the possibility that CA IX could represent a marker related to clear cell Renal Cell Carcinoma (ccRCC). Bcl-2 and Bax, and the activity of caspase-3, evaluated in tissue biopsies from patients, were congruent with resistance to apoptosis in ccRCCs with respect to healthy controls, respectively. In the same samples, the CA IX and pro-angiogenic factor VEGF expressions revealed that both these hypoxia responsive proteins were strongly increased in ccRCC with respect to controls. CA IX plasma concentration and CA activity were assessed in healthy volunteers and patients with benign kidney tumours and ccRCCs. CA IX expression levels were found strongly increased only in plasma from ccRCC subjects, whereas, CA activity was found similarly increased both in plasma from ccRCC and benign tumour patients, compared to healthy volunteers. These results show that the plasmatic level of CA IX, but not the CA total activity, can be considered a diagnostic marker of ccRCCs. Furthermore, as many reports exist relating CA IX inhibition to a better outcome to anticancer therapy in ccRCC, plasma levels of CA IX could be also predictive for response to therapy.     

Immunohistochemical demonstration of human carbonic anhydrase isoenzyme II in brain tumours

Summary Carbonic anhydrase (CA) is a functionally important enzyme in the central nervous system (CNS), where it is involved in the control of the acid-base balance and regulates the production of cerebrospinal fluid (CSF). Isoenzyme II (CA II) is the most widely distributed CA in the CNS, being present in at least myelin, oligodendrocytes, astrocytes and the choroid plexus. This study was undertaken to examine the presence of CA II in different brain tumours from 31 patients. Specific antibodies recognizing CA II were used in immunoperoxidase staining of tumour specimens. Anti-CA I and VI sera and normal rabbit serum were used as controls. CA II-positive staining was observed in all the astrocytic tumours (n = 9), oligodendrogliomas (n = 3) and medulloblastomas (n = 3). The most malignant tumours exhibited the strongest staining. In addition, four acoustic neurinomas, one plexiform neurofibroma, one choroid plexus papilloma, one ependymoblastoma and one subependymoma expressed the enzyme. Meningiomas (n = 4) and neuronal tumours (N = 4), including one dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos), were negative. Anti-CA I, VI and normal rabbit sera showed no specific staining in tumour cells. The presence of CA II in the astrocytomas was confirmed by Western blotting, which revealed a distinct 29 kDa polypeptide band corresponding the CA II. Anti-CA I serum showed similarly a single 29 kDa band, recognizing the enzyme which is abundantly present in the erythrocytes. The present results demonstrate that despite the malignant transformation of the cells, the expression of CA II is sustained in astrocytic tumours, oligodendrogliomas, ependymal and choroid plexus tumours and tumours of nerve sheath cell origin. Our results suggest that some tumours contain abundant CA II, which might leak into the CSF.     

Vanillin enones as selective inhibitors of the cancer associated carbonic anhydrase isoforms IX and XII. The out of the active site pocket for the design of selective inhibitors?

New C-glycosides and α,β-unsaturated ketones incorporating the 4-hydroxy-3-methoxyphenyl (vanillin) moiety as inhibitors of carbonic anhydrase (CA, EC 4.2.1.1) isoforms have been investigated. The inhibition profile of these compounds is presented against four human CA (hCA) isozymes, comprising hCAs I and II (cytosolic, ubiquitous enzymes) and hCAs IX and XII (tumour associated isozymes). Docking analysis of the inhibitors within the active sites of these enzymes has been performed and is discussed, showing that the observed selectivity could be explained in terms of an alternative pocket out of the CA active site where some of these compounds may bind. Several derivatives were identified as selective inhibitors of the tumour-associated hCA IX and XII. Their discovery might be a step in the strategy for finding an effective non-sulfonamide CA inhibitor useful in therapy/diagnosis of hypoxic tumours or other pathologies in which CA isoforms are involved.     

The specificity of human anti-cytochrome c autoantibodies that arise in autoimmune disease.

Cytochromes c (cyt c) are among the best characterized model Ag because their amino acid sequences and tertiary structures are well defined. One unique aspect of cyt c as an immunogen is its ability to induce autoantibody responses in animal models, although no pathology resulting from these responses has been reported. In this study, the presence and specificity of autoantibodies to cyt c were investigated in patients with SLE and related connective tissue diseases. Anti-cyt c antibodies were found in approximately 7% of patient sera and were statistically associated with the expression of antimitochondrial antibodies but were not statistically associated with any disease subset among those represented. Anti-cyt c was not associated with the presence of autoantibodies to DNA, histones, Ro, La, or Sm autoantigens. Most of the autoantibodies were specific for native or native-like forms of cyt c but antibodies to denatured forms were also apparent. Autoantibody binding was shown to be directed predominantly at selected sites of evolutionary variability within cyt c. The specificity of the human anti-cyt c autoantibodies appear to be similar to that of mouse anti-human cyt c antibodies and to autoantibodies elicited in mice against rat (mouse) cyt c.     

Enhancement of carbonic anhydrase activity by erythrocyte membranes

The human erythrocyte membrane is an efficient enhancer of both high (CA II) and low (CA I) activity isozymes of red blood cell carbonic anhydrase. The presence of membrane increased CO2 hydration catalyzed by bovine CA II 1.6-fold, human CA II 3.5-fold, and human CA I 1.6-fold. With the high activity CA isozymes, maximal stimulation was observed in the presence of 1-3 micrograms membrane protein/ml. The Vmax for bovine CA II (4 nM) rose from 0.302 to 0.839 mM/s, while that for human CA II (6 nM) increased from 0.113 to 0.414 mM/s in the absence and presence of membrane, respectively. The apparent Km for CO2 increased from 13.2 to 51.2 mM for bovine CA II, and from 6.5 to 38.5 mM for human CA II. Mixtures of membrane plus enzyme, upon centrifugation through linear sucrose density gradients, displayed enhanced Ca activity only in membrane-containing gradient fractions, verifying the stimulatory ability of membranes on enzyme activity and indicating tight and stable complex formation. Membrane enhancement of CA activity appears to be a general phenomenon in that mouse hepatocyte membranes also stimulated CA activity, although less efficiently than erythrocyte membranes. Of the many soluble putative effectors assayed, only imidazole enhanced CA II activity to an extent comparable with erythrocyte membranes; imidazole did not, however, stimulate the activity of human CA I. The data are consistent with a model of CA II activation by membrane association that may effect a distortion of the enzyme conformation in such a way as to facilitate intra- and/or intermolecular proton transfer between membrane-bound and enzyme-bound proton shuttling residues (perhaps the imidazole moiety of histidine) and the Zn-bound hydroxide at the catalytic site of the enzyme.     

Carbonic anhydrase inhibitors: inhibition of human cytosolic isozymes I and II and tumor-associated isozymes IX and XII with S-substituted 4-chloro-2-mercapto-5-methyl-benzenesulfonamides

A series of S-substituted 4-chloro-2-mercapto-5-methyl-benzenesulfonamides has been investigated as inhibitors of four isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), that is, the cytosolic, ubiquitous isozymes CA I and II, as well as the transmembrane, tumor-associated isozymes CA IX and XII. The new derivatives were inefficient inhibitors of isoform I (K(I)s in the range of 2.7-18.7 microM) but generally had low nanomolar affinity for the inhibition of the other three isoforms (K(I)s in the range of 2.4-214 nM against hCA II; 1.4-47.5 nM against hCA IX, and 1.7-569 nM against hCA XII, respectively). Some selectivity for the inhibition of the tumor-associated versus the cyctosolic isoform II with some of these compounds has also been evidenced. As CA IX is an important marker of tumor hypoxia and its predictive, prognostic, and druggability potentials for designing antitumor therapies were recently validated, detection of selective, potent CA IX inhibitors may be relevant in the fight against cancers overexpressing CA isozymes.     

Tumour-specific Antibodies in Human Malignant Melanoma and their Relationship to the Extent of the Disease

Biopsy specimens and sera were obtained from 103 melanoma patients. Autoantibodies were demonstrated by (1) complement-dependent cytotoxicity of autologous melanoma cells in short-term culture; (2) complement-dependent inhibition of ribonucleic acid synthesis; (3) immunofluorescent staining of the cytoplasm of killed melanoma cells and of the surface membrane of viable melanoma cells. Over one-third of the sera studied had antibodies to autologous melanoma cells. Although for technical reasons all three tests could not be performed with the cells from every melanoma, whenever multiple testing was possible there was complete concordance. The autoantibodies were virtually confined to patients in whom the disease was not widely disseminated, and over 80% of such patients had positive sera. In a limited number of patients who have been followed autoantibodies disappeared as the disease progressed to become widely disseminated. Two patients with generalized disease developed autoantibodies following inoculation by their own irradiated tumour cells.Two types of autoantibodies were recognized: one, active against antigen(s) in the cell surface membrane, was specific for each tumour—that is, only the autologous serum reacted—and was concerned in the cytotoxic activity; the other reacted with cytoplasmic antigens which appeared to be present in most or all melanoma cells.