Characterization of human colonic mucoprotein antigen

Rh-I-UEA-1 polymerized liposomes target and image adenomatous polyps in the APC(Min/+) mouse using optical colonography

Mutated adenomatous polyposis coli (APC) genes predispose transformations to neoplasia, progressing to colorectal carcinoma. Early detection facilitates clinical management and therapy. Novel lectin-mediated polymerized targeted liposomes (Rh-I-UEA-1), with polyp specificity and incorporated imaging agents were fabricated to locate and image adenomatous polyps in APC(Min/+) mice. The biomarker α-L-fucose covalently joins the liposomal conjugated lectin Ulexeuropaeus agglutinin (UEA-1), via glycosidic linkage to the polyp mucin layer. Multispectral optical imaging (MSI) corroborated a global perspective of specific binding (rhodamine B 532 nm emission, 590-620 nm excitation) of targeted Rh-I-UEA-1 polymerized liposomes to polyps with 1.4-fold labeling efficiency. High-resolution coregistered optical coherence tomography (OCT) and fluorescence molecular imaging (FMI) reveal the spatial correlation of contrast distribution and tissue morphology. Freshly excised APC(Min) bowels were incubated with targeted liposomes (UEA-1 lectin), control liposomes (no lectin), or iohexol (Omnipaque) and imaged by the three techniques. Computed tomographic quantitative analyses did not confirm that targeted liposomes more strongly bound polyps than nontargeted liposomes or iohexol (Omnipaque) alone. OCT, with anatomic depth capabilities, along with the coregistered FMI, substantiated Rh-I-UEA-1 liposome binding along the mucinous polyp surface. UEA-1 lectin denotes α-l-fucose biomarker carbohydrate expression at the mucin glycoprotein layer; Rh-I-UEA-1 polymerized liposomes target and image adenomatous polyps in APC(Min) mice.

Micro- and macrorheology of mucus

Mucus is a complex biological material that lubricates and protects the human lungs, gastrointestinal (GI) tract, vagina, eyes, and other moist mucosal surfaces. Mucus serves as a physical barrier against foreign particles, including toxins, pathogens, and environmental ultrafine particles, while allowing rapid passage of selected gases, ions, nutrients, and many proteins. Its selective barrier properties are precisely regulated at the biochemical level across vastly different length scales. At the macroscale, mucus behaves as a non-Newtonian gel, distinguished from classical solids and liquids by its response to shear rate and shear stress, while, at the nanoscale, it behaves as a low viscosity fluid. Advances in the rheological characterization of mucus from the macroscopic to nanoscopic levels have contributed critical understanding to mucus physiology, disease pathology, and the development of drug delivery systems designed for use at mucosal surfaces. This article reviews the biochemistry that governs mucus rheology, the macro- and microrheology of human and laboratory animal mucus, rheological techniques applied to mucus, and the importance of an improved understanding of the physical properties of mucus to advancing the field of drug and gene delivery.

Monoclonal antibody G47 engineered to be reactive with colorectal tumor mucin

We have previously shown that the normal adult colon produces a sialomucin containing the core trisaccharide 1,3 N-acetylgalactosamine. This structure was shown to be the epitope for a polyclonal antiserum that demonstrated colon "specific" activity. Antiserum binding is dependent upon the presence of O-acetylated sialic acids present at high concentrations in normal adult colon tissue. However, O-acetylation of sialic acids is decreased in colorectal cancer. Indeed, approximately 50% of colorectal carcinomas are nonreactive with this antiserum. In the current work, we used a de-O-acetylated, normal colon mucin as immunogen to generate monoclonal antibody (MAb) G47. Untreated normal colon mucins having a high O-acetylated sialic acid content were essentially nonreactive with G47. Removal of O-acetyl groups by saponification generated a reactive mucin derivative while subsequent treatment with neuraminidase abolished reactivity. By immunoperoxidase procedures MAb-G47 was reactive with approximately 85% of colorectal tumors while exhibiting relatively low reactivity with normal colon tissue. Mucins isolated from normal colon had on average less than 10% of the specific epitope as compared with mucins derived from colorectal tumors (p < 0.01). Initial immunohistochemical studies on tumors of noncolonic origin revealed few positive cases. The potential of MAb-G47 to assist in the diagnosis and/or prognosis of colorectal cancer is now being studied.

Characterization of monoclonal antibody PAM4 reactive with a pancreatic cancer mucin

A monoclonal antibody (MAb), PAM4, having reactivity with pancreatic carcinoma has been developed. PAM4 is an IgG1 immunoglobulin produced by immunization of mice with mucin purified from the xenografted RIP1 human pancreatic carcinoma. An immunohistochemical study of normal adult tissues showed the PAM4 reactive epitope to be restricted to the gastrointestinal tract and absent from normal pancreas. In neoplastic tissue, PAM4 was reactive with 85% of the pancreatic carcinomas, approximately half of the colon cancers and none of the breast, ovarian, prostate, renal and liver cancers. PAM4 was, in general, non-reactive with pancreatitis specimens whereas CA19.9 and DUPAN2 were strongly reactive with each one. Treatment of the mucin antigen by heating, reduction of disulfide bonds, or protease digestion abolished immunoreactivity with PAM4. Treatment of the mucin by neuraminidase or periodate oxidation reduced immunoreactivity but did not completely abolish it. Our data are consistent with the proposal that the PAM4 epitope is a conformationally dependent peptide epitope and that certain carbohydrate structures are necessary in order to maintain the correct peptide conformation. The high specificity and intense reactivity of PAM4 with pancreatic carcinoma tissue suggests that the antibody may prove useful for in vitro diagnostic assays as well as in vivo targeting of diagnostic and therapeutic agents.

Biochemical characterization of rat colonic mucins secreted in response to Entamoeba histolytica

Invasion of the colonic mucosa by Entamoeba histolytica trophozoites is preceded by colonic mucus depletion. The aim of our studies was to determine whether E. histolytica caused a differential secretion of mucin species in a rat colonic loop model. Mucus secretion in response to amoebae was followed by release of acid-precipitable 3H-glucosamine metabolically labelled glycoproteins and in vitro labelling of glycoprotein secretion with NaB3H4. The secretory response consisted of high-Mr goblet cell mucins and an increase in the secretion of low-Mr nonmucin glycoproteins as determined by Sepharose 4B column chromatography. High-Mr mucins subfractionated by Cellex-E (ECTEOLA) ion-exchange chromatography demonstrated a minor neutral and a major acidic mucin (greater than 98%) species. Marked differences between the neutral and acidic mucin species were indicated by immunogenicity and amino acid compositions. Thin-section histochemistry of rat colons confirmed secretion of neutral and acidic mucins in response to E. histolytica and demonstrated secretory activity from goblet cells from both the crypts and interglandular epithelium. E. histolytica mucus secretagogue activity was generalized and may function to deplete the host's protective mucus layer, facilitating invasion by the parasites.

Deglycosylation of neutral and acidic human colonic mucin

Human colonic mucin has been isolated from normal colonic mucosa by a phenol-water extraction procedure and purified by Sepharose 2B column chromatography. The mucin was further purified by cesium bromide density gradient centrifugation. Sodium dodecyl sulfate-polyacrylamide gel (5%) electrophoresis of this material showed high-molecular-weight mucin component(s) at the top of the gel. Chemical analyses of this preparation indicated a typical mucin profile of amino acids and carbohydrates. Ion-exchange chromatography resulted in the separation of two major fractions, one being more acidic than the other. Chemical deglycosylation of the purified preparation at 20 degrees C for 3 1/2 showed loss of sialic acid, fucose, galactose, and N-acetylglucosamine, whereas traces of N-acetylgalactosamine were still detected. High-pressure liquid chromatography of the deglycosylated material resulted in the purification of a major peptide, P1, with high levels of threonine, serine, and proline, resembling, in most respects, the profile of native mucin. The molecular weight of the peptide was determined to be approximately 97 kDa and serine was the single NH2 terminus.

Aberrant expression of monoclonal antibody-defined colonic mucosal antigens in inflammatory bowel disease

Human proximal colon from patients with inflammatory bowel disease and from controls was studied by two techniques to detect tumor-associated antigen expression. A panel of four murine monoclonal antibodies that recognize tumor-associated antigens was used to test purified colonic mucins for epitope expression by radioimmunoassay and to test formalin-fixed, deparaffinized sections of colon by the immunoperoxidase technique. The panel included monoclonal antibodies 19-9, B72.3, DU-PAN-2, and CSLEX1. Colonic mucins were purified from uninvolved surgical specimens by gel filtration with Sepharose 4B and cesium chloride-guanidine hydrochloride density gradient ultracentrifugation. Purified mucins from uninvolved colonic mucosal specimens from 4 of 7 patients with ulcerative colitis expressed one or more of these epitopes by radioimmunoassay, whereas mucins from 6 disease controls did not. Reactivity patterns were heterogeneous. Immunoperoxidase testing demonstrated staining with two or more antibodies in 14 of 18 involved inflammatory bowel disease segments, whereas control sections rarely stained with these antibodies, with the exception of 19-9. Sections of uninvolved mucosa from 4 of 9 patients with ulcerative colitis stained with two or more antibodies. Staining patterns were heterogeneous. The results demonstrate that colonic expression of tumor-associated epitopes occurs frequently in involved segments from both patients with ulcerative colitis and with Crohn's disease, whereas only patients with ulcerative colitis frequently expressed these epitopes in uninvolved segments.

Characterization and reactivity of a monoclonal antibody that recognizes a 76 kilodalton human colon tumor antigen

A monoclonal antibody (MAb 76) was produced by immunizing mice with a soluble cytoplasmic protein fraction from a human adenocarcinoma of the colon. MAb 76 showed specific immunoreactivity against a 76 kDa protein in immunoblot studies using total colon tumor cytosol proteins. Immunoprecipitation of phosphorylated cytosolic protein products with MAb 76 and subsequent analysis on SDS containing polyacrylamide gels revealed a single 38 kDa band, indicating that the 76 kDa antigen is associated with a 38 kDa phosphoprotein species. Indirect immunofluorescence analysis of primary tumor specimens and human colon tumor cell lines showed positive immunoreactivity with 6/7 human colon adenocarcinoma tissues and 15/18 human colon tumor cell lines. MAb 76 was unreactive with normal colon, liver and lung specimens from human, mouse and hamster. The epitope-bearing monomer detected by MAb 76 is immunologically conserved in a high percentage of colon tumor cells and tissues and may represent a cellular product that is characteristic of the transformed colon cell phenotype.

Immunological characterization of a novel human colon-associated antigen (CAA) by a monoclonal antibody

We have generated a monoclonal antibody (MAb), designated anti-CAA (colon-associated antigen), using as immunogen a membrane-enriched fraction of a biopsy from a moderately-differentiated human colonic adenocarcinoma. The molecular weight of this reactive antigen was determined by Western blotting to be greater than 200 kDa. When immunohistochemical techniques were used, MAb anti-CAA reacted with epithelium in the majority of normal, dysplastic and malignant colon specimens tested (greater reactivity was observed in normal colon than in benign or malignant lesions). Cell sorter analyses demonstrated a heterogeneous distribution of CAA on the cell surface of the well-differentiated LS-174T cell line. Antigen positive and antigen-negative cells were separated by means of flow cytometric techniques. These two subpopulations were then inoculated into immunosuppressed rats, resulting in xenograft tumors which differed significantly in their degree of histologic differentiation. Antigen-positive cells developed into well-differentiated adenocarcinomas, while antigen-negative cells developed into poorly differentiated adenocarcinomas. These results, along with immunohistochemical studies, indicate that the antigen detected by MAb anti-CAA has characteristics of a colon-associated antigen whose expression correlates with cellular differentiation. Moreover, differences in molecular weight as well as tissue distribution indicate that CAA may be a novel antigen different from those previously described.

Organ specific antigens of the human gastrointestinal tract

We previously reported the characterization of a normal adult colonic mucin antigen which contained an organ specific immunodeterminant [Tissue Antigen 11, 362 (1978)]. In the present study we have investigated mucins produced at other levels of the gastrointestinal tract in order to determine if regional specificities exist. Mucins were isolated from normal adult stomach, jejunum, ileum and colon and used to prepare antisera in rabbits. By radioimmunoassay at least four distinct specificities were observed. Gastric, ileal and colonic mucins were shown to contain immunodeterminants which were organ specific. Antiserum directed toward jejunal mucin determinants was reactive with the entire gastrointestinal tract. However, by heterologous inhibition analyses employing purified mucins as inhibiting antigens, the anti-jejunum antiserum was shown to be capable of discriminating a determinant present in much higher epitope density within small intestinal mucins as compared to mucins of the stomach and colon. Thus, it appeared that immunologic determinants present within mucin type glycoproteins of the gastrointestinal tissues exhibit anatomic specificity. In each case the structure of the immunodeterminant was, or was dependent upon the presence of a sialic acid derivative.

Antibodies to normal human colon membranes: preparation, characterization and tissue distribution

Rabbit antisera were raised to a membrane fraction of normal human colonic epithelium. After absorption, two antisera appeared to show restricted epithelial specificity when tested on routine paraffin wax-embedded histological sections by the indirect immunoperoxidase technique. The reaction was intense on epithelial cells of large and small intestine, and positive on stomach and duodenum, bile ducts in liver, gall bladder, pancreas and salivary gland. A very weak reaction was also seen in the bronchus and lung. There was no reaction with stromal, vascular or muscle components. All other tissues tested were negative, including hepatocytes, ectodermally-derived glandular epithelia, urogenital tissues and lymphoid organs. The antigen was also detected in 21 primary and metastatic large bowel carcinomata. By immunofluorescence, the antisera reacted with the colon adenocarcinoma-derived HT29 cell line and with primary colon epithelium explant cultures, but not with cultured fibroblasts. By immunoblotting of HT29 whole cell lysates, a triplet of polypeptides of approximate molecular weight range 55 000 to 60 000 were detected. This specificity appeared to be unrelated to previously described normal or tumour-associated antigens by criteria of tissue distribution, immunolocalization, molecular weight, and either absorption or radiobinding assays, or both.

Chemical and histochemical studies of normal and diseased human gastrointestinal tract. I. A comparison between histologically normal colon, colonic tumours, ulcerative colitis and diverticular disease of the colon

Chemical and histochemical methods were used to compare the epithelial glycoproteins from formalin-fixed surgical specimens of normal human large intestine, colonic tumours, ulcerative colitis and diverticular disease. All the epithelial glycoproteins contained fucose, galactose, glucosamine, galactosamine and, in addition, sialic acids both with and without O-acyl substituents in the side chain and/or at position C4. The glycoproteins of the normal ascending and descending colons differed significantly with respect to the percentage of the sialic acids released following digestion of the de-O-acylated glycoprotein with Vibrio cholera neuraminidase and to the molar fucose-sialic acid ratio. Statistical analysis of the chemical data showed that (a) compared to normal, the sialic acids of the tumour and ulcerative colitis glycoproteins from the descending colon were significantly less substituted in the side chain and at position C4; (b) the O-acetyl substitution pattern of the sialic acids of the ulcerative colitis glycoproteins from the ascending colon and the quantitative composition of the carbohydrate prosthetic groups of the ulcerative colitis glycoproteins from both ascending and descending colons differed from normal; (c) it was not always possible to distinguish between the ulcerative colitis and tumour glycoproteins on the basis of the O-acetyl substitution pattern of their sialic acids; and (d), there were minor differences between normal glycoproteins and those from cases of diverticular disease.

Purification and characterization of a pancreatic cancer-associated antigen (PCAA) from normal colonic mucosa

The same antigenic substance as pancreatic cancer-associated antigen (PCAA), sharing an identical immunogenicity with Gelder's POA, was isolated and purified from normal colonic mucosa. Purified colonic PCAA (PCAAc) is a glycoprotein with a molecular weight of approximately 600,000; it consists of 30% carbohydrates and 70% peptides, and appears to be an N-glycosidic glycoprotein. Antiserum raised against purified PCAAc showed one fused line with our original anti-PCAA antiserum to ascites fluid from patients with pancreatic cancer and extract from normal colonic mucosa. Circulating PCAAc levels assayed by rocket immunoelectrophoresis showed significant elevation in sera of patients with carcinoma of the pancreas. It is concluded that PCAA might be a new tumor-associated antigen which is produced ectopically during oncogenesis.

Composition of human colonic mucin. Selective alteration in inflammatory bowel disease

Human colonic mucin has been isolated from mucosal scrapings of fresh surgical specimens of normal controls as well as patients with Crohn's colitis and ulcerative colitis. Following sonication and ultracentrifugation, mucin fractions were separated from other soluble colonic glycoproteins by Sepharose 4B chromatography. After nuclease digestion, cesium chloride gradient centrifugation of the excluded material yielded colonic mucin with an average buoyant density of 1.52 g/ml. Subsequent chromatography of the apparently homogeneous colonic mucin on DEAE-cellulose revealed the presence of at least six distinct mucin species (mucin I-VI). Each mucin species was found to have a distinctive hexose, hexosamine, sialic acid, and sulfate content as well as blood group substance activities. Mucin from five patients with Crohn's colitis was found to represent a mixture of at least six discrete species comparable to those isolated from normal colonic specimens. However, in mucin from eight patients with ulcerative colitis there was a marked and selective reduction of one component mucin subclass, designated species IV. Normal mucin and mucin from patients with Crohn's disease contained 48 +/- 17 and 42 +/- 12 mg of species IV/g, while mucin from patients with ulcerative colitis had 5 +/- 3 mg/g solubilized glycoprotein. The selective absence of species IV was found in preparations from both sigmoid (n = 7) and ascending (n = 4) colon and could not be accounted for by an overall decrease in total mucin content. The selective reduction of species IV was also found in mucin isolated from relatively noninflamed colonic mucosa of patients with ulcerative colitis. The carbohydrate composition and blood group activities of the remaining five mucin species were similar to their normal counterparts. Based on the results to date, there appears to be an underlying selective decrease of one colonic mucin subclass in ulcerative colitis.

Purification and composition of colonic epithelial mucin

Colonic mucin was purified from homogenized scrapings of rat colonic epithelial cells using gel filtration and ion-exchange chromatography. High molecular weight water-soluble mucin was separated from low molecular weight proteins by gel exclusion chromatography on Sepharose 4B, and was further separated into two major mucin fractions and several non-mucin fractions on DEAE-cellulose. Fraction IV, the major mucin, was a sulphated glycoprotein with 62% carbohydrate by weight, and high concentrations of serine and threonine. A more acidic mucin, fraction V, had similar composition. Approx. 85% of the sialic acid of fractions IV and V were removed after incubation with Clostridium perfringens neuraminidase. Blood group A but not group H activity was present in fractions III, IV, and V. Ultracentrifugation experiments showed that fraction IV migrated as a single peak, whereas fraction V contained two components. Our study indicates that colonic mucin consists of at least two closely related acidic high molecular weight glycoproteins which can be separated from non-mucin contaminants by ion-exchange chromatography.

A histochemical comparison of the O-acylated sialic acids of the epithelial mucins in ulcerative colitis, Crohn's disease, and normal controls

Two histochemical techniques, the PAT/KOH/PAS and the PBT/KOH/PAS, were used to investigate the side chain O-acyl substitution patterns of the sialic acids of the colonic epithelial mucins in cases of ulcerative colitis and Crohn's disease. In both diseases there was, as compared to normal, a reduction in the proportion of sialic acids O-acylated at C7C8, the reduction being greater in ulcerative colitis. Further, there appeared to be an association between the severity of the disease and the reduction in the staining of O-acylated sialic acids. This relationship was more marked in ulcerative colitis. In some cases of both diseases there was evidence for epithelial mucins containing predominantly C7-substituted sialic acids. This study has confirmed our previous conclusion that, in Crohn's disease of the terminal ileum, the disease is associated with an increase in the proportion of sialic acids bearing side chain substituents.

Purification of human intestinal goblet cell antigen (GOA), its immunohistological demonstration in the intestine and in mucus producing gastrointestinal adenocarcinomas

Goblet cell antigen (GOA) was purified from gastric signet ring cell carcinoma. It was immunogenic and was used to produced antisera which stained goblet cells of the small and large intestine and of intestinalized gastric mucosa by indirect immunological methods. Various types of gastric and colonic cancer contained GOA. These findings demonstrate a histiogenic relationship between intestinal goblet cells, various gastrointestinal cancers and associated premalignant conditions.

Further characterization of CSAp, an antigen associated with gastrointestinal and ovarian tumors

Colon-specific antigen-p, or CSAp, was originally extracted from GW-39 tumors, which are human colonic carcinomas serially transplanted in golden hamsters, and antibodies to CSAp have been produced in the same animal hosts. By means of immunodiffusion and a hemagglutination-inhibition assay, CSAp has been found to be restricted to adult and fetal small intestine, neoplastic gastric and colonic tissues, inflamed colon, and cystic mucinous tumors of the ovary. CSAp was shown to be distinct from blood group antigens, including Lea and Leb blood group substances, liver ferritin, AFP, CEA, CSA, CMA, ZGM, and BOFA, and to have the electrophoretic mobility of an alpha2-globulin. Gel filtration studies indicated that CSAp in GW-39 tumor, primary human colonic carcinoma, and ovarian cancer mucinous cyst fluid had a peak molecular size range of 70,000--110,000. Quantitation of CSAp in 214 tissue specimens by the hemagglutination-inhibition assay revealed a progressive increase in fetal, inflamed, and neoplastic intestine, such that CSAp in colonic tumors was increased over normal colon tissue. Thus, CSAp appears to be an organ-specific antigen showing increased levels in some gastrointestinal and ovarian neoplasms, as well as in specimens with colitis.

Sialic acids of human large bowel mucosa: o-acylated variants in normal and malignant states

Five sialic acid variants have been demonstrated in normal, 'transitional', and tumour extracts of human large bowel mucosa by thin-layer chromatography. Two-dimensional thin-layer chromatography, with intermediate alkaline hydrolysis, confirmed that the variants were N-acetyl neuraminic acids with additional O-acylation. Cases studied so far show changes in the proportions of these variants in malignancy.

A mucoprotein with colon-specific determinants

The tissue specificity of colonic mucoprotein antigen (CMA) was examined to determine whether the antigen might have a role as a tissue marker. The immunofluorescent technique, using a rabbit anti-CMA antiserum, was employed to examine a wide range of tissues. Gastrointestinal mucosae as well as non-gastrointestinal mucin producing tissues were positive; however, non-gastrointestinal reactivity could be eliminated by the appropriate absorptions. Mucoproteins were purified separately from each gastrointestinal anatomic region and used to absorb the antiserum. This analysis demonstrated the existence of a family of mucoproteins with a common gastrointestinal specific determinant(s). Mucoproteins from neighboring regions, as seen by this antiserum, showed a greater structural similarity than did mucoproteins from distant regions. Absorption of the antiserum with ileal or cecal mucoprotein allowed the detection of a colon specific determinant present on CMA.

Isolation of a sulfated glycopeptidic antigen from human gastric tumors: its localization in normal and cancerous gastrointestinal tissues

A sulfated glycopeptidic antigen (SGA) was purified from papain-digested cancerous human gastric mucosa. The amino acid composition of this antigen was characterized by a high percentage of threonine and proline. Serine was present in small quantities and aromatic amino acids were absent. The amount of sulfate present was evaluated at 7.5%. Fucose, galactose, N-acetyl glucosamine, N-acetyl galactosamine and sialic acid were found to be present in the molar ratio 1:4.6:3.0:6.2:5.0. With immunofluorescence techniques, a rabbit antiserum against the sulfated glycopeptide stained adult gastric mucosa when this tissue had intestinal metaplasia and stained the goblet cells of the intestinal tract (small and large intestines). About 50% of colonic carcinomas and some gastric carcinomas contained SGA. This sulfated antigen was present in well-differentiated tumors and there was a good correlation between tumoral acid mucous secretory activity and the SGA positivity.

Definition in man of a polymorphic system of the normal colonic secretions

A study conducted in 30 normal human colons, obtained from cadaveric kidney donors, has evidenced the presence of two polymorphic antigenic specificities, W and Z, in the secretory cells of the colon mucosa. Three phenotypes have been demonstrated so far: W-Z- (frequency: 0.17), W-Z+ (frequency: 0.23), and W+Z+ (frequency: 0.60). Specific anti-WZ and anti-W alloantibodies, independent of anti-A and B agglutinins, were found in normal sera from blood donors. No apparent correlation was found between the WZ specificities and the ABH Lewis specificities, the other blood group systems specificities, and the leucocyte group (HL-A) specificities.