A preclinical study comparing approaches for augmenting the immunogenicity of a heptavalent KLH-conjugate vaccine against epithelial cancers

Previously using a series of monovalent vaccines, we demonstrated that the optimal method for inducing an antibody response against cancer cell-surface antigens is covalent conjugation of the antigens to keyhole limpet hemocyanin (KLH) and the use of a saponin adjuvant. We have prepared a heptavalent-KLH conjugate vaccine containing the seven epithelial cancer antigens GM2, Globo H, Lewis(y), TF(c), Tn(c), STn(c), and glycosylated MUC1. In preparation for testing this vaccine in the clinic, we tested the impact on antibody induction of administering the individual conjugates plus adjuvant compared with a mixture of the seven conjugates plus adjuvant, and of several variables thought to augment immunogenicity. These include approaches for decreasing suppressor cell activity or increasing helper T-lymphocyte activity (low dose cyclophosphamide or anti-CTLA-4 MAb), different saponin adjuvants at various doses (QS-21 and GPI-0100), and different methods of formulation (lyophilization and use of polysorbate 80). We find that: (1). Immunization with the heptavalent-KLH conjugate plus GPI-0100 vaccine induces antibodies against the seven antigens of comparable titer to those induced by the individual-KLH conjugate vaccines, high titers of antibodies against Tn (median ELISA titer IgM/IgG 320/10240), STn (640/5120), TF (320/10240), MUC1 (80/20480), and globo H (640/40); while lower titers of antibodies against Lewis(y)()(160/0) and only occasional antibodies against GM2 are induced. (2). These antibodies reacted with the purified synthetic antigens by ELISA, and with naturally expressed antigens on the cancer cell surface by FACS. (3). None of the approaches for further altering the suppressor cell/helper T-cell balance nor changes to the standard formulation by lyophilization or use of polysorbate 80 had any impact on antibody titers. (4). An optimal dose of saponin adjuvant, QS-21 (50 microg) or GPI-0100 (1000 microg), is required for optimal antibody titers. This heptavalent vaccine is sufficiently optimized for testing in the clinic.

Biochemical characterization of soluble Tn glycoproteins from malignant effusions of patients with carcinomas

The Tn determinant (GalNAc-O-Ser/Thr) is one of the most specific human tumor markers. In normal cells Tn is a cryptic structure in the peptide core of mucin type O-glycoproteins, and it is detected in an unmasked form in most human carcinomas evaluated by immunohistochemistry. Scarce data are available regarding the characteristics of soluble Tn bearing glycoproteins. We herein report the first comparative characterization of soluble Tn glycoproteins derived from different kinds of human tumors (breast, colon, gastric, ovarian and liver). Considerable heterogeneity was observed in the physicochemical properties of Tn soluble glycoproteins from all the tumor-associated effusions evaluated. In SDS-PAGE analysis Tn glycoproteins from liver and colon effusions migrated as a broad single major component (>500 kDa), while several components of >200 kDa were identified in samples from breast, ovarian, and gastric cancer. The results of perchloric acid (PCA) treatment and CsCl gradient ultracentrifugation indicated that the Tn glycoproteins in effusion fluids correspond predominantly to mucin-like glycoproteins. However, in samples from patients with colon and liver cancer, a fraction of Tn glycoproteins formed part of the immune complexes that precipitated in PCA, suggesting that the anti-Tn immune response in vivo could modify their physicochemical properties. The four apomucins evaluated (MUC1, MUC2, MUC5AC and MUC6) carried Tn epitopes in each of the effusions, indicating that soluble apomucin detection may reflect the abnormal expression of MUC genes inherent to these tumors. Taking together, these results indicate that apomucin expression profile is responsible, at least in part, for the high heterogeneity of soluble Tn glycoproteins, and suggest that the identification of Tn determinant on the different soluble apomucins could be useful for the development of new diagnostic tools as well as to evaluate the anti-tumor immune response in patients with cancer.

Polypeptide GalNAc-transferases, ST6GalNAc-transferase I, and ST3Gal-transferase I expression in gastric carcinoma cell lines

Mucin O-glycosylation in cancer is characterized by aberrant expression of immature carbohydrate structures leading to exposure of simple mucin-type carbohydrate antigens and peptide epitopes. Glycosyltransferases controlling the initial steps of mucin O-glycosylation are responsible for the altered glycosylation observed in cancer. We studied the expression in gastric cell lines of six UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-T1, T2, T3, T4, T6, T11) that catalyze the initial key step in the regulation of mucin O-glycosylation, the transfer of GalNAc from UDP-GalNAc to serine and threonine residues. We also studied the expression of ST6GalNAc-I, the enzyme responsible for the synthesis of Sialyl-Tn antigen (NeuAcalpha2,6GalNAc) and the ST3Gal-I, the enzyme responsible for the synthesis of Sialyl-T antigen (NeuAcalpha2,3Galbeta1,3GalNAc). This study was done using specific monoclonal antibodies, enzymatic assays, and RT-PCR. Our results showed that GalNAc-T1, -T2, and -T3 have an ubiquitous expression in all gastric cell lines, whereas GalNAc-T4, -T6, and -T11 show a restricted expression pattern. The immunoreactivity with MAb VU-2-G7 suggests that, apart from GalNAc-T4, another GalNAc transferase is involved in the glycosylation of the Thr in the PDTR region of the MUC1 tandem repeat. The expression of ST3Gal-I correlates with the expression of the Sialyl-T antigen in gastric cell lines and in the control cell lines studied. The expression of ST6GalNAc-I is low in gastric cell lines, in accordance with the low/absent expression of the Sialyl-Tn antigen.

Functional conservation of subfamilies of putative UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferases in Drosophila, Caenorhabditis elegans, and mammals. One subfamily composed of l(2)35Aa is essential in Drosophila

The completed fruit fly genome was found to contain up to 15 putative UDP-N-acetyl-alpha-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-transferase) genes. Phylogenetic analysis of the putative catalytic domains of the large GalNAc-transferase enzyme families of Drosophila melanogaster (13 available), Caenorhabditis elegans (9 genes), and mammals (12 genes) indicated that distinct subfamilies of orthologous genes are conserved in each species. In support of this hypothesis, we provide evidence that distinctive functional properties of Drosophila and human GalNAc-transferase isoforms were exhibited by evolutionarily conserved members of two subfamilies (dGalNAc-T1 (l(2)35Aa) and GalNAc-T11; dGalNAc-T2 (CG6394) and GalNAc-T7). dGalNAc-T1 and novel human GalNAc-T11 were shown to encode functional GalNAc-transferases with the same polypeptide acceptor substrate specificity, and dGalNAc-T2 was shown to encode a GalNAc-transferase with similar GalNAc glycopeptide substrate specificity as GalNAc-T7. Previous data suggested that the putative GalNAc-transferase encoded by l(2)35Aa had a lethal phenotype (Flores, C., and Engels, W. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 2964-2969), and this was substantiated by sequencing of three lethal alleles l(2)35Aa(HG8), l(2)35Aa(SF12), and l(2)35Aa(SF32). The finding that subfamilies of GalNAc-transferases with distinct catalytic functions are evolutionarily conserved stresses that GalNAc-transferase isoforms may serve unique biological functions rather than providing functional redundancy, and this is further supported by the lethal phenotype of l(2)35Aa.

Expression of mucins (MUC1, MUC2, MUC5AC, and MUC6) and type 1 Lewis antigens in cases with and without Helicobacter pylori colonization in metaplastic glands of the human stomach

Helicobacter pylori (H. pylori) causes gastritis and intestinal metaplasia (TM) that may evolve to gastric carcinoma. Paradoxically, IM leads to clearing of H. pylori, except for some cases in which it persists in damaging the mucosa. The objective of this study was to compare the profile of mucins and type 1 Lewis antigens in IM cases with and without H. pylori. Gastric biopsies (n=32) were double-stained using immunohistochemistry (MUC1, MUC2, MUC5AC, MUC6, Le(a), sialyl-Le(a), and Le(b)) and histochemistry for H. pylori. H. pylori was observed in association with IM in 4 of 22 biopsies with IM (complete IM - 6; incomplete IM - 16). The four biopsies with IM and H. pylori displayed a particular pattern of incomplete IM: expression of MUC1 and MUC5AC and little/no expression of MUC2. The 18 biopsies with IM and without H. pylori had high levels of MUC2 expression, regardless of the IM type. The pattern of expression of type 1 Lewis antigens was similar in IM, regardless of the presence or absence of H. pylori. It is concluded that H. pylori is able to colonize incomplete IM whenever it contains foci expressing MUCI and MUC5AC and no MUC2, independently from Le(a), sialyl-Le(a) and Le(b). The results suggest, furthermore, that MUC2 expression affects the ability of H. pylori to colonize IM areas, regardless of the levels of expression of MUC1 and MUC5AC.

Mucins MUC1, MUC2, MUC5AC and MUC6 expression in the evaluation of differentiation and clinico-biological behaviour of gastric carcinoma

Normal gastric mucosa expresses MUC1 and MUC5AC in foveolar epithelium and MUC6 in mucous neck cells of the body and deep glands of the antrum. Several studies have reported aberrant expression of an under-glycosylated form of MUC1, decreased expression of "gastric" mucins and aberrant expression of "non-gastric" mucins in gastric carcinoma. In this study, we analysed the expression profile of mucins MUC1, MUC2, MUC5AC and MUC6 in 94 gastric carcinomas using immunohistochemistry. Our results showed that: (1) mucin expression is associated with tumour type (MUC5AC with diffuse and infiltrative carcinomas and MUC2 with mucinous carcinomas) but not with the clinico-biological behaviour of the tumours; and (2) mucin expression is associated with tumour location (MUC5AC with antrum carcinomas and MUC2 with cardia carcinomas), indirectly reflecting differences in tumour differentiation according to tumour location.

Mucins as key molecules for the classification of intestinal metaplasia of the stomach

Mucins and mucin-associated carbohydrates have a distinct expression pattern that can be modified under pathological conditions. Normal gastric mucosa expresses MUC1 and MUC5AC in foveolar epithelium and MUC6 in the glands. Lewis type-1 chain antigens (Le(a) and Le(b)) are expressed in foveolar epithelium, whereas Lewis type-2 chain antigens (Le(x) and Le(y)) are expressed in the glands. In this study we used monoclonal antibodies to evaluate the pattern of mucins and Lewis type-1 carbohydrates in intestinal metaplasia (IM) and compared it with IM types determined using histochemistry. In type-I or complete IM we found expression of MUC2 intestinal mucin and decreased/absent expression of MUC1, MUC5AC and MUC6. In type-II/III or incomplete IM there was co-expression of MUC2 and the mucins expressed in the stomach. No major differences were detected among the three IM types regarding expression of Lewis antigens. Furthermore we observed that sialylated compounds other than sialyl-Le(a) are responsible for histochemical detection of sialomucins and that sulpho-Le(a/c) is expressed in the presence or absence of sulphomucins detected using histochemistry. We conclude that mucin immunohistochemistry may replace classic histochemistry for the classification of IM into complete and incomplete types. The present study challenges the distinction of type-II from type-III IM since we did not observe major differences in the expression profile of mucins and Lewis type-1 carbohydrates. Finally, it seems necessary to evaluate the predictive value of IM according to the presence of specific sulphated carbohydrates (e.g. sulpho-Le(a/c)) rather than histochemically detected sulphomucins.

Chemoenzymatic synthesis of sialylated glycopeptides derived from mucins and T-cell stimulating peptides

The Tn, T, sialyl-Tn, and 2,3-sialyl-T antigens are tumor-associated carbohydrate antigens expressed on mucins in epithelial cancers, such as those affecting the breast, ovary, stomach, and colon. Glycopeptides carrying these antigens are of interest for development of cancer vaccines and a short, chemoenzymatic strategy for their synthesis is reported. Building blocks corresponding to the Tn (GalNAc alpha-Ser/Thr) and T [Gal beta(1-->3)GalNAc alpha-Ser/Thr] antigens, which are relatively easy to obtain by chemical synthesis, were prepared and then used in the synthesis of glycopeptides on the solid phase. Introduction of sialic acid to give the sialyl-Tn [Neu5Ac alpha(2-->6)GalNAc alpha-Ser/Thr] and 2,3-sialyl-T [Neu5Ac alpha(2-->3)Gal beta(1-->3)GalNAc alpha-Ser/Thr] antigens is difficult when performed chemically at the building block level. Sialylation was therefore carried out with recombinant sialyltransferases in solution after cleavage of the Tn and T glycopeptides from the solid phase. In the same manner, the core 2 trisaccharide [Gal beta 1-->3(GlcNAc beta 1-->6)GalNAc] was incorporated in glycopeptides containing the T antigen by using a recombinant N-acetylglucosaminyltransferase. The outlined chemoenzymatic approach was applied to glycopeptides from the tandem repeat domain of the mucin MUC1, as well as to neoglycosylated derivatives of a T cell stimulating viral peptide.

Evidence for glycosylation-dependent activities of polypeptide N-acetylgalactosaminyltransferases rGalNAc-T2 and -T4 on mucin glycopeptides

We present evidence that site-specific O-glycosylation by recombinant polypeptide N-acetylgalactosaminyltransferases rGalNAc-T2 and -T4 is controlled by the primary sequence context, as well as by the position and structure of previously introduced O-glycans. Synthetic mucin-type (glyco)peptides corresponding to sections of the tandem repeat regions of MUC1, MUC2, and MUC4 were used as substrates for recombinant polypeptide N-acetylgalactosaminyltransferases, rGalNAc-T2 and -T4. By concerted and sequential action the two transferases are able to fully glycosylate MUC1 but only partially MUC2 and MUC4 tandem repeat peptides. GalNAc residues on MUC1 acceptor peptides trigger activity of rGalNAc-T4 directed to Ser in VTSA and Thr in PDTR and of rGalNAc-T2 to Ser/Thr within the GSTA motif of variant MUC1 peptides. However, elongation of GalNAc by beta3-galactosylation inhibits rGalNAc-T4 activity completely and rGalNAc-T2 activity with respect to the acceptor site GSTA. These findings are in accord with the inhibition of rGalNAc-T2 and -T4 by fully GalNAc-substituted MUC1 repeat peptide and support a glycosylation-dependent activity induction or enhancement of both enzymes.

Advantages of external accumulation for electron capture dissociation in Fourier transform mass spectrometry

A combination of external accumulation (XA) with electron capture dissociation (ECD) improves the electron capture efficiency, shortens the analysis time, and allows for rapid integration of multiple scans in Fourier transform mass spectrometry. This improves the signal-to-noise ratio and increases the number of detected products, including structurally important MS3 fragments. With XA-ECD, the range of the labile species amenable to ECD is significantly extended. Examples include the first-time determination of the positions of six GalNAc groups in a 60-residue peptide, five sialic acid and six O-linked GalNAc groups in a 25-residue peptide, and the sulfate group position in a 11-residue peptide. Even weakly bound supramolecular aggregates, including nonspecific peptide complexes, can be analyzed with XA-ECD. Preliminary results are reported on high-rate XA-ECD that uses an indirectly heated dispenser cathode as an electron source. This shortens the irradiation time to > or = 1 ms and increases the acquisition rate to 3 scans/s, an improvement by a factor of 10-100.

Immunohistochemical study of the expression of MUC5AC and MUC6 in breast carcinomas and adjacent breast tissues

AIM

To study the protein expression patterns of MUC5AC and MUC6 in normal and diseased breast tissues and to compare their expression with that of a mucin (MUC1) normally expressed in mammary tissues.

METHODS

Formalin fixed, paraffin wax embedded tissue from 69 cases of invasive breast carcinoma and surrounding breast tissue was studied immunohistochemically with monoclonal antibodies against MUC1 (SM3), MUCSAC (CLH2), and MUC6 (CLH6), using the avidin-biotin-peroxidase method.

RESULTS

MUC5AC was detected in five of 68 cases of invasive carcinoma including one of three cases of pure colloid carcinoma. MUCSAC expression in the adjacent normal breast epithelium was present in one of 29 cases and in one of two cases of ductal carcinoma in situ. None of 15 cases of ductal hyperplasia without atypia was positive for MUCSAC. MUC6 was present in 15 of 65 cases of invasive carcinoma, in four of 29 cases of normal adjacent epithelium, two of 15 cases of ductal hyperplasia without atypia, and one of two cases of ductal carcinoma in situ. MUC1 immunoreactivity detected by the SM3 antibody was present in 50 of the 67 cases of invasive carcinoma, but expression was also detected in benign epithelium. All invasive carcinomas expressing MUCSAC were positive for MUC1 and four were positive for MUC6. No significant association was found between the expression of these mucins and tumour size, histological grade, node status, oestrogen receptor status, p53 positivity, or c-ErbB-2 overexpression.

CONCLUSIONS

This study documents the expression of two different mucins (MUCSAC and MUC6) not described as being expressed by normal breast tissues in a minority of breast carcinomas, as well as in normal and hyperplastic epithelium. Although the role of mucins in malignant transformation and the progression of breast cancer is not well understood, in some cases, there is probably an upregulation of several genes that encode distinct mucin proteins.

Expression and localization of immunoreactive-sialomucin complex (Muc4) in salivary glands

Sialomucin Complex (SMC; Muc4) is a heterodimeric glycoprotein consisting of two subunits, the mucin component ASGP-1 and the transmembrane subunit ASGP-2. Northern blot and immunoblot analyses demonstrated the presence of SMC/Muc4 in submaxillary, sublingual and parotid salivary glands of the rat. Immunocytochemical staining of SMC using monoclonal antisera raised against ASGP-2 and glycosylated ASGP-1 on paraffin-embedded sections of parotid, submaxillary and sublingual tissues was performed to examine the localization of the mucin in the major rat salivary glands. Histological and immunocytochemical staining of cell markers showed that the salivary glands consisted of varying numbers of serous and mucous acini which are drained by ducts. Parotid glands were composed almost entirely of serous acini, sublingual glands were mainly mucous in composition and a mixture of serous and mucous acini were present in submaxillary glands. Since immunoreactive (ir)-SMC was specifically localized to the serous cells, staining was most abundant in parotid glands, intermediate levels in submaxillary glands and least in sublingual glands. Ir-SMC in sublingual glands was localized to caps of cells around mucous acini, known as serous demilunes, which are also present in submaxillary glands. Immunocytochemical staining of SMC in human parotid glands was localized to epithelial cells of serous acini and ducts. However, the staining pattern of epithelial cells was heterogeneous, with ir-SMC present in some acinar and ductal epithelial cells but not in others. This report provides a map of normal ir-SMC/Muc4 distribution in parotid, submaxillary and sublingual glands which can be used for the study of SMC/Muc4 expression in salivary gland tumors.

The lectin domain of UDP-N-acetyl-D-galactosamine: polypeptide N-acetylgalactosaminyltransferase-T4 directs its glycopeptide specificities

The initiation step of mucin-type O-glycosylation is controlled by a large family of homologous UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferases). Differences in kinetic properties, substrate specificities, and expression patterns of these isoenzymes provide for differential regulation of O-glycan attachment sites and density. Recently, it has emerged that some GalNAc-transferase isoforms in vitro selectively function with partially GalNAc O-glycosylated acceptor peptides rather than with the corresponding unglycosylated peptides. O-Glycan attachment to selected sites, most notably two sites in the MUC1 tandem repeat, is entirely dependent on the glycosylation-dependent function of GalNAc-T4. Here we present data that a putative lectin domain found in the C terminus of GalNAc-T4 functions as a GalNAc lectin and confers its glycopeptide specificity. A single amino acid substitution in the lectin domain of a secreted form of GalNAc-T4 selectively blocked GalNAc-glycopeptide activity, while the general activity to peptides exerted by this enzyme was unaffected. Furthermore, the GalNAc-glycopeptide activity of wild-type secreted GalNAc-T4 was selectively inhibited by free GalNAc, while the activity with peptides was unaffected.

Characterization of a panel of monoclonal antibodies using GalNAc glycosylated peptides and recombinant MUC1

A panel of 56 murine monoclonal antibodies submitted to the ISOBM TD-4 (MUC1) Workshop was analysed for reactivity against nonglycosylated and in vitro GalNAc glycosylated peptides. Twenty-six antibodies reacted with nonglycosylated MUC1 peptides containing 3-5 tandem repeats. The reactivities of most of the antibodies were not affected by GalNAc glycosylation of the peptides. Antibody #147 (decoded as BCP9) reactivity was inhibited when 3 mol of GalNAc per repeat were incorporated in the peptide (at sites T in GVTSA and ST in GSTAP), whereas the reactivity with GalNAc glycosylated peptides with 2 mol of GalNAc per repeat (sites T in GVTSA and T in GSTAP) was unaffected. This is in agreement with the epitope defined as GSTAP.

Role of fucosyltransferases in the association between apomucin and Lewis antigen expression in normal and malignant gastric epithelium

BACKGROUND

In normal gastric epithelium, MUC5AC is detected in superficial epithelium associated with Lewis type 1 antigens and MUC6 is detected in antral glands with Lewis type 2. Therefore, the stomach constitutes an excellent model to examine the role of glycosyltransferases in determining the specificity of apomucin glycosylation.

AIMS

To determine the molecular basis of this association and to examine changes in expression of gastric and intestinal apomucins and their association with Lewis antigens during the gastric carcinogenesis process.

METHODS

Fucosyltransferase (FUT1, FUT2, FUT3) and mucin (MUC5AC, MUC6) transcripts were detected using reverse transcription-polymerase chain reaction. Apomucin (MUC2, MUC4, MUC5AC, MUC6) and Lewis antigen (types 1 and 2) expression were analysed using single and double immunohistochemistry and in situ hybridisation.

RESULTS

In the normal stomach, FUT1 is exclusively detected associated with MUC6; FUT2 is only detected when MUC5AC is present. This co-regulation is lost in gastric tumours, as is differential expression of MUC5AC and MUC6 in normal gastric epithelial cells. In gastric tumours, especially those with the intestinal phenotype, MUC2 and MUC4 genes are upregulated, and gastric-type and intestinal-type mucins are coexpressed. These changes are early events in the gastric carcinogenesis process, as they are detected in intestinal metaplasia.

CONCLUSIONS

The glycosylation pattern found in normal gastric epithelium is dictated by the specific set of fucosyltranferases expressed by the cells rather than by the apomucin sequence. The development of intestinal metaplasia and gastric cancer is associated with the appearance of cellular phenotypes that are absent from normal epithelium.

Reactivity of natural and induced human antibodies to MUC1 mucin with MUC1 peptides and n-acetylgalactosamine (GalNAc) peptides

Antibodies (Abs) to MUC1 occur naturally in both healthy subjects and cancer patients and can be induced by MUC1 peptide vaccination. We compared the specificity of natural and induced MUC1 Abs with the objective of defining an effective MUC1 vaccine for active immunotherapy of adenocarcinoma patients. Serum samples, selected out of a screened population of 492 subjects for their high levels of IgG and/or IgM MUC1 Abs, were obtained from 55 control subjects and from 26 breast cancer patients before primary treatment, as well as from 19 breast cancer patients immunized with MUC1 peptides coupled to keyhole limpet hemocyanin (KLH) and mixed with QS-21. The samples were tested with enzyme-linked immunoassays for reactivity with (1) overlapping hepta- and 20-mer peptides spanning the MUC1 tandem repeat sequence; (2) two modified 60-mer peptides with substitutions in the PDTR (PDTA) or in the STAPPA (STAAAA) sequence of each tandem repeat; and (3) four 60-mer glycopeptides with each 1, 2, 3 and 5 mol N-acetylgalactosamine (GalNAc) per repeat. More than one minimal epitopic sequence could be defined, indicating that Abs directed to more than one region of the MUC1 peptide core can coexist in one and the same subject. The most frequent minimal epitopic sequence of natural MUC1 IgG and IgM Abs was RPAPGS, followed by PPAHGVT and PDTRP. MUC1 peptide vaccination induced high titers of IgM and IgG Abs predominantly directed, respectively, to the PDTRPAP and the STAPPAHGV sequences of the tandem repeat. Natural MUC1 Abs from breast cancer patients reacted more strongly with the N-acetylgalactosamine (GalNAc) peptides than with the naked 60-mer peptide, while reactivity with the GalNAc-peptides was significantly reduced (2-tailed p < 0.0001) in the MUC1 IgG and IgM Abs induced by MUC1 peptide vaccination. Whereas in cancer patients glycans appear to participate in epitope conformation, the epitope(s) recognized by MUC1 Abs induced by peptide vaccination are already masked by minimal glycosylation. Therefore, our results indicate that a MUC1 glycopeptide would be a better vaccine than a naked peptide.

Gastric carcinoma exhibits distinct types of cell differentiation: an immunohistochemical study of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6)

The expression of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6) has previously been described in gastric polyps. In the present study, the expression profile of these trefoil peptides and mucins was characterized in 96 gastric carcinomas, in an attempt to further the understanding of the histogenesis and cell differentiation of gastric carcinoma. Taking together the co-expression of trefoil peptides and mucins, three phenotypes were defined: complete gastric, incomplete gastric, and non-gastric phenotype. Gastric differentiation (complete and incomplete) was observed in 30 out of 33 (90.9%) diffuse carcinomas and in 38 out of 53 (71.7%) intestinal carcinomas. Non-gastric differentiation was observed in only three (9.1%) diffuse carcinomas and in 15 (28.3%) intestinal carcinomas. The phenotypes observed in intestinal carcinomas were similar to those previously observed in adenomatous polyps, whereas most diffuse carcinomas mimicked the phenotype of hyperplastic polyps. The percentage of cases displaying a non-gastric phenotype was higher, though not significantly, in tumours that had invaded the gastric wall than in T1 tumours, regardless of histotype. It is concluded that gastric-type differentiation is retained in the majority of gastric carcinomas, being more prominent in diffuse than in intestinal carcinomas, and in early than in advanced carcinomas.

Gastric carcinoma exhibits distinct types of cell differentiation: an immunohistochemical study of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6)

The expression of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6) has previously been described in gastric polyps. In the present study, the expression profile of these trefoil peptides and mucins was characterized in 96 gastric carcinomas, in an attempt to further the understanding of the histogenesis and cell differentiation of gastric carcinoma. Taking together the co-expression of trefoil peptides and mucins, three phenotypes were defined: complete gastric, incomplete gastric, and non-gastric phenotype. Gastric differentiation (complete and incomplete) was observed in 30 out of 33 (90.9%) diffuse carcinomas and in 38 out of 53 (71.7%) intestinal carcinomas. Non-gastric differentiation was observed in only three (9.1%) diffuse carcinomas and in 15 (28.3%) intestinal carcinomas. The phenotypes observed in intestinal carcinomas were similar to those previously observed in adenomatous polyps, whereas most diffuse carcinomas mimicked the phenotype of hyperplastic polyps. The percentage of cases displaying a non-gastric phenotype was higher, though not significantly, in tumours that had invaded the gastric wall than in T1 tumours, regardless of histotype. It is concluded that gastric-type differentiation is retained in the majority of gastric carcinomas, being more prominent in diffuse than in intestinal carcinomas, and in early than in advanced carcinomas.

Patterns of expression of trefoil peptides and mucins in gastric polyps with and without malignant transformation

The expression of two trefoil peptides (TFF1 and TFF2) and four mucins (MUC1, MUC2, MUC5AC, and MUC6) was evaluated by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) in 29 gastric polyps, 10 hyperplastic and 19 adenomatous, eight of which displayed malignant transformation. The aims of this study were to characterize the expression profile of these molecules in each type of polyp and to investigate possible modifications of the profile during the process of malignant transformation. All hyperplastic polyps displayed immunoreactivity for TFF1, MUC5AC, and MUC1 in more than 75 per cent of the cells. In adenomatous polyps, three main phenotypes could be identified: complete gastric phenotype (co-expression of TFF1 and MUC5AC)-nine cases (47.4 per cent); incomplete gastric phenotype (TFF1-positive and MUC5AC-negative)-seven cases (36.8 per cent); non-gastric (intestinal) phenotype (no expression of TFF1 or MUC5AC)-three cases (15.8 per cent). Data yielded by immunohistochemistry and RT-PCR showed a good correlation for both TFF1 and TFF2. One hyperplastic and seven adenomatous polyps with villous architecture displayed foci of diffuse and intestinal-type carcinoma, respectively; in all of these cases, MUC1 expression and signs of gastric differentiation were observed in both the non-malignant and the carcinomatous component. It is concluded that gastric differentiation is a feature of hyperplastic polyps and of a subset of adenomatous polyps which is shared by early carcinomas arising in some of these polyps, regardless of the histological type of polyp and of carcinoma.

Immunohistochemical study of the expression of MUC6 mucin and co-expression of other secreted mucins (MUC5AC and MUC2) in human gastric carcinomas

To investigate the expression of MUC6 mucin in gastric carcinomas, we generated a novel monoclonal antibody (MAb CLH5) using an MUC6 synthetic peptide. MAb CLH5 reacted exclusively with the MUC6 peptide and with native and deglycosylated mucin extracts from gastric tissues. MAb CLH5 immunoreactivity was observed in normal gastric mucosa restricted to pyloric glands of the antrum and mucopeptic cells of the neck zone of the body region. In a series of 104 gastric carcinomas, 31 (29.8%) were immunoreactive for MUC6. The expression of MUC6 was not associated with histomorphological type or with clinicopathological features of the carcinomas. Analysis of the co-expression of MUC6 with other secreted mucins (MUC5AC and MUC2) in 20 gastric carcinomas revealed that different mucin core proteins are co-expressed in 55% of the cases. MUC6 was co-expressed and co-localized with MUC5AC in 45% and with MUC2 in 5% of the cases. Expression of MUC2 alone was observed in 25% of the cases. All carcinomas expressing MUC2 mucin in more than 50% of the cells were of the mucinous type according to the WHO classification. The co-expression of mucins was independent of the histomorphological type and stage of the tumors. In conclusion, we observed, using a novel well-characterized MAb, that MUC6 is a good marker of mucopeptic cell differentiation and is expressed in 30% of gastric carcinomas, independent of the clinicopathological features of the cases. Furthermore, we found that co-expression and co-localization of mucins in gastric carcinomas is independent of histomorphology and staging. Finally, we observed that intestinal mucin MUC2 is expressed as the most prominent mucin of the mucins tested in mucinous-type gastric carcinomas.

Gastric carcinoma exhibits distinct types of cell differentiation: an immunohistochemical study of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6)

The expression of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6) has previously been described in gastric polyps. In the present study, the expression profile of these trefoil peptides and mucins was characterized in 96 gastric carcinomas, in an attempt to further the understanding of the histogenesis and cell differentiation of gastric carcinoma. Taking together the co-expression of trefoil peptides and mucins, three phenotypes were defined: complete gastric, incomplete gastric, and non-gastric phenotype. Gastric differentiation (complete and incomplete) was observed in 30 out of 33 (90.9%) diffuse carcinomas and in 38 out of 53 (71.7%) intestinal carcinomas. Non-gastric differentiation was observed in only three (9.1%) diffuse carcinomas and in 15 (28.3%) intestinal carcinomas. The phenotypes observed in intestinal carcinomas were similar to those previously observed in adenomatous polyps, whereas most diffuse carcinomas mimicked the phenotype of hyperplastic polyps. The percentage of cases displaying a non-gastric phenotype was higher, though not significantly, in tumours that had invaded the gastric wall than in T1 tumours, regardless of histotype. It is concluded that gastric-type differentiation is retained in the majority of gastric carcinomas, being more prominent in diffuse than in intestinal carcinomas, and in early than in advanced carcinomas.

Mucins and mucin-associated carbohydrate antigens expression in gastric carcinoma cell lines

Mucins are high-molecular-mass glycoproteins with high carbohydrate content and marked heterogeneity both in the apoprotein and in the oligosaccharide side chains. Mucin genes are expressed in a regulated manner, namely in the human stomach. The first aim of the present study was to characterise the expression of mucins and mucin-associated carbohydrate antigens in seven gastric carcinoma cell lines, and to compare their expression profiles with those of normal gastric tissues and human gastric carcinomas. Secondly, we aimed to see whether or not there is an association between the expression of mucins and mucin-associated carbohydrate antigens. Our results show that mucin expression in gastric carcinoma cell lines: (a) follows in part the mucin expression profile of normal gastric mucosa and gastric carcinomas with wide expression of MUC1 and MUC5AC; (b) parallels the aberrant pattern of mucin expression observed in human gastric carcinomas with occasional expression of MUC2, MUC3, MUC4 and MUC5B; (c) does not include, at least in our series, the expression of MUC6 mucin; and (d) follows in part the differentiation pattern of the carcinomas from which the cell lines originated, keeping S-Tn expression in cell lines derived from glandular carcinomas. Our results further demonstrate that there is no apparent relationship between the mucin core proteins and the simple mucin-type or Lewis carbohydrate antigens.