Humoral immunity against a tandem repeat epitope of human mucin MUC-1 in sera from breast, pancreatic, and colon cancer patients.

Using synthetic peptides 60,80, and 105 residues long, corresponding to 3, 4, and 5.25 tandem repeats of human mucin MUC-1 protein core, as antigens in a solid-phase enzyme-linked immunosorbent assay, we screened sera from 24 breast cancer patients, 10 colon cancer patients, and 12 pancreatic cancer patients, at various stages of disease, for the presence of mucin-specific antibodies. The 105-residue peptide was superior in allowing detection of high levels of anti-mucin antibodies in 10.9% of sera in each cancer group. Another 4.3% showed intermediate reactivity. Lower levels of detection were achieved with the 80-residue peptide, and no specific reactivity was detectable with the 60-residue peptide. Anti-mucin antibodies were previously undetectable when this assay was performed with purified whole mucin or short synthetic peptides. The presence or absence of antibody did not correlate with the levels of circulating mucin or stage of disease. One highly reactive serum sample was used to identify more precisely the epitope on the long synthetic peptide to which the reactivity was directed. The reactivity of this serum specific for the 105-residue peptide was blocked by a 9-residue peptide from the NH2-terminal region of the 20-residue tandem repeat containing the previously identified immunogenic epitope APDTRP. Another 9-residue mucin peptide, from the COOH-terminal region of the tandem repeat which does not contain the APDTRP epitope, had no effect. All the mucin-specific reactivity was found to be of the IgM isotype, indicating a helper T-cell-independent response, unusual for an antibody against a peptide epitope, but not unexpected for tandemly repeated epitopes.

Expression of the human MUC1 mucin cDNA in a hamster pancreatic tumor cell line HP-1.

A full length cDNA for the human mucin gene, MUC1, under the control of human beta actin promoter, was transfected into a carcinogen induced hamster pancreatic ductal tumor cell line, HP-1. Transfectants were selected by resistance to geneticin. Integration of the foreign human MUC1 cDNA occurred at multiple sites in the genome of HP-1. Northern blot analysis showed MUC1 expression in cells transfected with MUC1 cDNA placed in the correct orientation, but not in control cells (HP-1 cells transfected with vector alone, or with the MUC1 cDNA placed in the antisense orientation). Western blot analysis using monoclonal antibody HMFG-2, which is reactive with the MUC1 protein, showed results consistent with the Northern blot data. Positive immunoperoxidase staining using HMFG-2 was seen in HP-1 cells transfected with MUC1 cDNA but not with untransfected or HP-1 control cells. The integration of human MUC1 mucin gene in HP-1 cells caused no significant change in the growth rate of HP-1 cells in vitro, but resulted in an enhanced growth rate for xenografts of MUC1 transfected HP-1 cells grown in nude mice.

Human Muc 1 mucin gene expression in the fetal pancreas.

The expression of the human Muc 1 mRNA was evaluated during fetal pancreatic development. Human fetal pancreatic tissues were collected at various stages from 13 to 24 weeks of age. Northern blot analysis of total RNA from these tissues showed that Muc 1 mRNA was not detectable until 18-19 weeks of age. Therefore, Muc 1 mucin expression can be detected in prenatal human pancreata at approximately 19 weeks of age and thereafter.

Growth modulatory effects of some 6-methylenic steroids on human and hamster pancreatic adenocarcinoma cells in vitro.

Similarities between pancreatic, prostate and mammary tumors in possession of steroidal receptors and enzymes led to investigation of the responsiveness of pancreatic cancer to steroids with potential for tumor inhibition. The compounds were tested in vitro against human (HPAF and PANC-1) and hamster (HP-1) pancreatic ductal tumor cell lines using a colorimetric enzyme-based assay (MTT) to assess both cytotoxic and cytostatic effects and the 3H-thymidine uptake assay for cytostatic effects. Only certain 6-methylenic steroidal 3-ketones and the anti-estrogen tamoxifen citrate exerted appreciable anti-tumor effects. Marked cytotoxic and cytostatic activity was shown by some 6-methylenic congeners of progesterone, testosterone and its acetate, and 4-androstene-3,17-dione on both human and hamster pancreatic tumor cell lines. In contrast to prostate cancer, testosterone, but not 5 alpha-dihydrotestosterone, enhanced growth of the well differentiated HPAF cell line as well as the poorly differentiated PANC-1 cell line. It is therefore surprising that the 6-methylene derivative of testosterone acetate, which is both a potent androgen and 5 alpha-reductase inhibitor, is a very active tumor inhibitor in our assay.

Transfection of the human Muc 1 mucin gene into a poorly differentiated human pancreatic tumor cell line, Panc1: integration, expression and ultrastructural changes.

Full-length cDNA for the human mucin Muc 1 gene under the control of the beta actin promoter was transfected into a morphologically poorly differentiated pancreatic tumor cell line, Panc 1, by the DEAE-dextran method. Integration of the foreign Muc 1 cDNA occurred at multiple sites in the genome of Panc 1. Northern blot analysis showed Muc 1 expression in cells transfected with the Muc 1 cDNA, but not in control cells transfected with vector alone or an antisense Muc 1 cDNA construct. Transfection of Panc 1 with Muc 1 cDNA did not cause any detectable alteration or rearrangements in the Muc 1 gene or cDNA. Western blot analysis of cell lysates from the transfected lines using a monoclonal antibody reactive with the Muc 1 protein (HMFG-2) demonstrated that Muc 1 protein expression correlated with the Northern blot data. Immunoperoxidase staining using HMFG-2 showed that Muc 1 protein was expressed in less than 5% of control Panc 1 cells, whereas greater than 95% of cells transfected with Muc 1 cDNA expressed the protein. Ultrastructural examination of Muc 1-transfected cells demonstrated the formation of dense core granules and increased amounts of rough endoplasmic reticulum.

Ultrastructural differentiation of sodium butyrate-treated human pancreatic adenocarcinoma cell lines.

The differentiation effects of sodium butyrate were examined in a series of human pancreatic adenocarcinoma cell lines: Panc-1, a poorly differentiated cell line; HPAF, a pleomorphic cell line isolated in this laboratory; and two clones of the parental HPAF cell line, well-differentiated CD11 and less-differentiated CD18. Incubation with 2 mM sodium butyrate induced a dramatic decrease in cell proliferation and saturation densities in culture and an increase in alkaline phosphatase activity. Of particular interest, incubation with sodium butyrate also caused a number of morphologic alterations in these cells, attributed to an induction of secretory differentiation. Following sodium butyrate treatment, CD18 cells were virtually indistinguishable from the more highly differentiated CD11 cells as evidenced by an increase in the number of profiles of rough endoplasmic reticulum and of Golgi. Intercellular and intracytoplasmic lumens, whose appearance is quite common in CD11 cells but nonexistent in untreated CD18 cells, appeared in these cells following only 5 days of sodium butyrate treatment. An increase in the cytoplasmic secretory elements was also observed in sodium butyrate-treated Panc-1 cells; however, lumen formation never occurred in these cells.

Isolation and characterization of a complementary DNA (PD-1) differentially expressed by human pancreatic ductal cell tumors.

A complementary DNA (cDNA) library from a cloned subline (CD-11) of a well differentiated human pancreatic tumor cell line, HPAF, was subjected to differential screening using single stranded cDNA probes synthesized from mRNA of the well differentiated cell clone CD-11 and a poorly differentiated pancreatic tumor cell line, Panc 1. A cDNA clone (PD-1) was identified which had an insert of 626 base pairs (bp). PD-1 cDNA hybridized to a transcript of about 650 bp on Northern blot analysis, suggesting that the cDNA was close to full length. Densitometric analysis of Northern blots showed that a well differentiated pancreatic tumor line had a 5-fold higher PD-1 expression as compared to the poorly differentiated line, Panc 1. Nucleotide sequence analysis of the PD-1 cDNA and its deduced amino acid sequence showed an open reading frame of 399 bp. In addition to the open reading frame, the sequence had a 5' untranslated region of 61 bp and a 3' untranslated tail of 147 bp. The nucleotide sequence did not show any significant homology to any other sequence in the GENBANK or EMBL databases; however, the translated protein showed 35% homology to bacterial ribosomal proteins over 112 amino acids. Sequence analysis of the PD-1 cDNA and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of its in vitro transcription/translation product suggest that this gene encoded a protein of 16,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple, effective method for the construction of subtracted cDNA libraries.

A simple method is described for the construction of subtracted cDNA libraries. The technique was used to create a human pancreatic tumor cDNA library that was screened using either hybridization with cDNA probes or antibodies. cDNA from a well-differentiated tumor cell line (CD-11) was subtracted against RNA from an undifferentiated tumor cell line (Panc-1). The subtracted cDNA was purified from RNA-cDNA hybrids by oligo-dA cellulose affinity chromatography. Single-stranded subtracted cDNA was used as a template for random primed second-strand synthesis using the Klenow's fragment of DNA polymerase. After ligation with Eco R1 adapters, cDNA was inserted into lambda gt11. A library of 140,000 primary pfu was obtained that contained 92% recombinants. A small portion of this library (40,000 pfu) was subjected to probe screening with a mucin cDNA probe known to be differentially expressed by CD-11 cells. The ratio of mucin cDNA clones to actin cDNA clones was increased by greater than 300-fold in the subtracted cDNA library compared to a standard cDNA library from the same cell line. The absolute number of mucin cDNA clones per 40,000 pfu was also increased 32-fold in the subtracted library. Pancreatic tumor mucin cDNAs were also identified in the subtracted library by antibody screening. The subtraction procedure yielded a 50-fold enrichment in differentially expressed cDNA detected by antibodies, compared to a nonsubtracted library from the same cell line.

Human cytotoxic lymphocytes reactive with pancreatic adenocarcinoma cells.

In this study we describe the establishment of long-term cytotoxic T lymphocyte (CTL) cell lines and clones from lymph nodes of 9 pancreatic cancer patients by stimulation with allogeneic pancreatic tumor cell lines. The CTL cells exhibited strong cytolytic activity against many, but not all, allogeneic pancreatic tumor cell lines, but showed little or no reactivity against most nonpancreatic tumor cells, indicating they were detecting non-HLA antigens. Most of the cells from the established CTL cell lines were CD3+, and the CD8 antigen was also expressed on the majority of the cells. Occasional cultures exhibited a broad spectrum of cytolytic activity, and such CTL cell lines showed high expression of the natural killer (NK) cell markers, Leu-19 and Leu-11b. Seven clones were established from two CTL cell lines (LT and RE). These clones exhibited functional and phenotypic heterogeneity. The cytolytic activity of CTL cell lines and clones was inhibited by antibodies to CD3 antigen. Immunoprecipitation experiments using an anti-CD3 monoclonal antibody (Leu4) or anti-alpha/beta T cell receptor antibody (beta f1) revealed the presence of two bands of Mr 40,000 and Mr 50,000 in clones positive for the alpha/beta T cell receptor. The in vivo effects of the LT cytotoxic clones were studied in the Winn assay using pancreatic tumor xenografts in nude mice. Subcutaneous injections of a mixture of the cytotoxic clones and pancreatic tumor cells resulted in a complete inhibition of tumor development, whereas mice given injections of tumor cells and CTL clones that lacked cytotoxic activity against pancreatic cells developed tumors.

Molecular cloning and sequence analysis of the human ribosomal protein S16.

A cDNA library from a poorly differentiated human pancreatic tumor cell line was screened for differentially expressed mRNAs using single-stranded cDNA probes synthesized from poly(A+) RNA of the poorly differentiated cell line Panc 1 and a very well differentiated cell line CD11. One of the cDNA clones isolated hybridized to a transcript size of 650 base pairs on Northern blot analysis and showed 30-fold higher expression in the poorly differentiated cell line as compared with the well differentiated cell line. Sequence analysis of this cDNA clone and its deduced amino acid sequence showed an open reading frame of 441 nucleotides with 100 and 98.6% homology to ribosomal protein S16 (rpS16) from rat and mouse, respectively. Northern blot analyses with a panel of 14 pancreatic cell lines, 2 breast cell lines, 2 colon cell lines, and several other tissues showed higher expression of rpS16 only in the poorly differentiated pancreatic tumor cell line Panc 1. The expression of mRNA for two other ribosomal proteins, rpL30 and rpL32, were not elevated in Panc 1. Southern blot analysis of genomic DNA showed a 20-fold amplification of a single band among the rpS16 family only in the Panc 1 cell line.

Analysis of pancreatic serum markers in patients with cystic fibrosis.

The occurrence of increased serum concentrations of pancreatic tumor markers CA 19-9, CA 50 and elastase 1 in cystic fibrosis (CF) prompted us to investigate the pancreatic markers DU-PAN-2 and TATI. DU-PAN-2 was measured in serum samples of 48 CF patients, 42 pediatric control patients, and 51 parents of CF children by a competition radioimmunoassay (RIA). A commercially available RIA test kit was used to measure TATI serum levels of 38 CF patients and 40 control patients. Nineteen percent of CF patients, 0% of the control group, and 6% of the parents exceeded the DU-PAN-2 threshold value of 300 U/ml. TATI concentrations were increased (greater than 20 micrograms/L) in 24% of CF patients and in 17% of control patients. The sensitivity-specificity curve of DU-PAN-2 was similar to those of CA 50 and elastase 1 but less discriminating than that of CA 19-9. However, the sensitivity-specificity profile of CA 19-9 can only be marginally enhanced in a range of low specificity by simultaneously determining elastase 1 and/or DU-PAN-2 antigens. TATI does not provide any diagnostic use in CF.

Radiolocalization of human pancreatic tumors in athymic mice by monoclonal antibody DU-PAN 1.

Monoclonal antibodies that selectively bind to pancreatic tumors may be useful in the therapy and diagnosis of pancreatic carcinoma. In this study we have examined the tumor localization of radioiodinated DU-PAN 1, a mouse monoclonal antibody that is selective for a human pancreatic cancer-associated antigen. After radiolabeling, both DU-PAN 1 intact monoclonal antibody and F(ab')2 fragments retained immunoreactivity and showed high affinity for the pancreatic tumor cell line CA13 in vitro. Paired-label biodistribution studies in nude mice bearing CA13 s.c. xenografts were performed. Mice received both 131I-labeled DU-PAN 1 immunoglobulin G2a or F(ab')2 fragment and 125I-labeled mouse myeloma immunoglobulin G2a or F(ab')2 fragment. Tumor uptake for 5-micrograms doses of DU-PAN 1 immunoglobulin ranged from 4.8 to 11.83% injected dose/g. Tumor uptake values for mice given 5-micrograms doses of DU-PAN 1 F(ab')2 ranged from 3.9 to 6.9% injected dose/g. Tumor uptakes of the respective myeloma controls were lower in all cases when compared with the DU-PAN 1 preparations. Tumor localization indices for 5-micrograms doses of DU-PAN 1 immunoglobulin were 3.0 and 24 h and 2.9 at 48 h. For 5-micrograms doses of DU-PAN 1 F(ab')2, tumor localization indices were 29.9 at 24 h and 90.0 at 48 h. In most cases, tumor:normal tissue ratios were greater than 3 at all time points, indicative of tumor selectivity for both DU-PAN 1 preparations, but the ratios were considerably higher using the DU-PAN 1 F(ab')2. The F(ab')2 fragment thus displays better tumor localization characteristics when compared with the intact immunoglobulin. Protein doses of DU-PAN 1 F(ab')2 of between 5 and 10 micrograms gave the best localization, although protein doses of up to 100 micrograms could be administered before apparent tumor saturation was seen.

Cloning and sequencing of a human pancreatic tumor mucin cDNA.

A monospecific polyclonal antiserum against deglycosylated human pancreatic tumor mucin was used to select human pancreatic mucin cDNA clones from a lambda gt11 cDNA expression library developed from a human pancreatic tumor cell line. The full-length 4.4-kilobase mucin cDNA sequence included a 72-base pair 5'-untranslated region and a 307-base pair 3'-untranslated region. The predicted amino acid sequence for this cDNA revealed a protein of 122,071 daltons containing 1,255 amino acid residues of which greater than 60% were serine, threonine, proline, alanine, and glycine. Approximately two-thirds of the protein sequence consisted of identical 20-amino acid tandem repeats which were flanked by degenerate tandem repeats and nontandem repeat sequences on both the amino-terminal and carboxyl-terminal ends. The amino acid sequence also contained five putative N-linked glycosylation sites, a putative signal sequence and transmembrane domain, and numerous serine and threonine residues (potential O-linked glycosylation sites) outside and within the tandem repeat position. The cDNA and deduced amino acid sequence of the pancreatic mucin sequence was over 99% homologous with a mucin cDNA sequence derived from breast tumor mucin, even though the native forms of these molecules are quite distinct in size and degree of glycosylation.

A novel ribonucleoprotein complex defined by monoclonal antibodies to NIH 3T3 cells transfected with human pancreatic adenocarcinoma DNA.

Three monoclonal antibodies elicited to NIH 3T3 cells transfected with DNA from a human pancreatic adenocarcinoma cell line recognized a novel ribonucleoprotein complex. Minimally, this ribonucleoprotein complex contained a Mr 240,000 protein (by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and two RNA species with apparent sizes of 1.5 and 3.0 kilobases (by formaldehyde agarose gel electrophoresis). In addition to a cytoplasmic and nuclear subcellular localization, the RNA antigen was secreted from human tumor cell lines and NIH 3T3 cells transfected with pancreatic tumor DNA (inhibitable by monensin) and was apparently not a viral or Mycoplasma contaminant. The ribonucleoprotein antigen was detected in some normal tissues by immunoperoxidase but was not found in or secreted from in vitro cultured normal human fibroblasts, nontransfected or spontaneously transformed NIH 3T3 cells, or normal peripheral blood leukocytes.

Polypeptide core of a human pancreatic tumor mucin antigen.

This work describes the molecular properties of the polypeptide core of a human pancreatic mucin antigen isolated from a human pancreatic adenocarcinoma cell line, HPAF. Pancreatic tumor mucin was isolated by a combination of molecular sieve chromatography and CsCl/4 M guanidine-HCl density gradient ultracentrifugation. Trifluoromethane sulfonic acid was used to remove carbohydrate units from purified mucin molecules. A rabbit monospecific polyclonal antibody was generated against pancreatic apomucin and reacted with a Mr greater than 200,000 species. The antibody binding data indicated that the rabbit antiserum raised against pancreatic apomucin cross-reacted with a breast mucin synthetic peptide. Northern blot and immunodot blot analyses of various cell line extracts revealed that a tandem repeat sequence and a similar mRNA were detected in both pancreatic and breast mucin-producing cell lines. These results suggest that pancreatic apomucin and breast apomucin share some similarity in tandem repeated nucleic acid and protein sequences.

Expression of CD9 antigen on normal activated human B cells.

The expression of the CD9 pre-B acute lymphoblastic leukemia (ALL)-associated antigen was studied. CD9-positive B cells were enriched in the in vivo-activated buoyant B cell population isolated from tonsils. Small tonsil B cells activated in vitro with either PWM, phorbol 12-myristate 13-acetate (TPA), or anti-Ig plus low Mr B cell growth factor (BCGF) also demonstrated increased CD9 expression. The peak of CD9 expression (30-40% positive cells) occurred after 4-6 days of activation. The kinetics of increased CD9 expression was similar to that of the 4F2 activation antigen. CD9 antigen expression on tonsillar B cells as well as on pre-B leukemic cell lines was associated with protein kinase C activation. Two phorbols that activate protein kinase C (TPA; phorbol 12,13-dibutyrate) induced expression of the CD9 antigen whereas a phorbol analogue that does not activate C kinase (4-alpha-phorbol 12,13-didecanoate) and an analogue that is a very weak agonist (phorbol 12-myristate 13-acetate-4-0-methyl ether) were unable to induce CD9 expression on tonsil B cells or on the cell lines. The effect of the anti-CD9 monoclonal antibody, DU-ALL-1, on B cell mitogenesis was studied. Dense or buoyant tonsillar B cells were cultured in the presence or absence of DU-ALL-1 antibody plus PWM, anti-Ig, and BCGF, DU-ALL-1 antibody did not inhibit or augment the mitogenic response of resting or activated B cells. These results indicate that the CD9 pre-B ALL antigen is present on a population of normal activated tonsillar B cells and that its induction of expression is associated with protein kinase C activation.

Specific, major histocompatibility complex-unrestricted recognition of tumor-associated mucins by human cytotoxic T cells.

We have previously reported the establishment of cytotoxic T-cell lines from pancreatic cancer patients, by continuously stimulating tumor-draining lymph node cells with allogeneic pancreatic tumor cell lines. After the preliminary characterization of their phenotype and tumor specificity, detailed studies performed with one of the cell lines, W.D., show that it recognizes a specific antigen, a large and heavily glycosylated mucin molecule, expressed on pancreatic and breast tumors and tumor cell lines. Although this recognition appears major histocompatibility complex (MHC)-unrestricted, the antigen receptor used by the cytotoxic T cell is the alpha/beta heterodimer, typically found on MHC-restricted T cells. The target antigen is atypical, however, in its ability to directly bind and activate the T cells in the absence of self MHC, presumably by abundant and regularly repeated antigenic epitopes. These findings are important because they demonstrate a specific T-cell response against a human tumor-associated antigen. In addition to pancreatic and breast tumors, various mucin molecules are known to be produced by other tumors of epithelial cell origin and could be expected to stimulate similar T-cell-mediated immune responses.

Characterization of clones of a human pancreatic adenocarcinoma cell line representing different stages of differentiation.

With a limiting dilution technique, clones have been established from the human pancreatic adenocarcinoma cell line, HPAF. Phenotypic analysis by a panel of murine monoclonal antibodies demonstrated distinct profiles of antigenic expression between the clones. However, identical isozyme patterns of different clones indicated their common origin from the parental HPAF cells. Two clones, CD11 and CD18, appeared to be arrested at different stages of secretory epithelial cell differentiation. CD11 cells demonstrated many characteristics of a well-differentiated state, including the formation of ductal structures with polarized, long columnar-shaped cells, the presence of secretory granules in the cytoplasm, high DU-PAN-2 antigen expression in nude mouse xenografts, and a longer doubling time (42 h) in tissue culture. In contrast, CD18 cells exhibited characteristics of a poorly differentiated state, including solid nests of isoprismatic cells without luminal spaces and cellular polarization, absence of secretory granules and DU-PAN-2 antigen expression in xenografts, and a shorter doubling time (26 h) in tissue culture. Since no culture systems of normal pancreatic ductal cells are currently available, these two pancreatic adenocarcinoma clones may provide a unique system to study genes and antigens related to pancreatic ductal cell differentiation.

Co-expression of CA 19-9, DU-PAN-2, CA 125, and TAG-72 in pancreatic adenocarcinoma.

Various tumor-associated antigens have been reported in pancreatic adenocarcinoma tissue. This study examines the incidence and co-expression of CA 19-9, DU-PAN-2, CA 125, and TAG-72 in serum and cancer tissue from patients with pancreatic cancer. In tissue, 83% of the cases demonstrated co-expression of three or more antigens. The incidence of antigen expression was comparably high for CA 19-9, DU-PAN-2, and TAG-72; however, significantly more cancer cells within each sample demonstrated CA 19-9. Serologic co-expression of elevated antigen levels was less common; only 39% of the patients showed increased circulating levels of three or more antigens. The predictive value of tissue immunoreactivity for elevated circulating levels of antigen was strongest for CA 19-9. Immunoreactivity patterns in cancer tissue suggest that the epitopes for these antigens are distinct, and DU-PAN-2 antigen was identified in patients who could not manufacture CA 19-9 (a sialylated Lea antigen). However, a strong correlation between circulating levels of CA 19-9 and DU-PAN-2 supports the contention that these two antigens are incidentally expressed on the same mucin molecule.