Characterization of mucin antigens recognized by monoclonal antibodies raised against human colon cancer cells

Two monoclonal antibodies, MLS 102, which recognizes cancer-associated mucin antigens, and MLS 103, which recognizes normal mucin, were used to isolate, by immunoaffinity chromatography, the corresponding antigens from cell lysates and spent medium of a human colorectal carcinoma cell line, LS 180. The MLS 102 antigen contained serine, threonine, and proline as major amino acids. The carbohydrate chains of the MLS 102 antigen were composed of O-linked NeuAc alpha 2----6GalNAc (56%), N-acetylgalactosamine (25%), and longer oligosaccharide chains. The MLS 103 antigen differed from the MLS 102 antigen in both amino acid and carbohydrate composition. Most O-linked oligosaccharides of the MLS 103 antigen were longer than the disaccharide found in the MLS 102 antigen. Immunostaining of LS 180 cells using MLS 102 and MLS 103 revealed that the cells are heterogeneous with respect to the expression of the antigens.     

Enhanced cytotoxicity against colon carcinoma by combinations of noncompeting monoclonal antibodies to the 17-1A antigen

The purpose of this report was to investigate the binding specificities and ability to generate antibody dependent cell mediated cytotoxicity (ADCC) or antibody dependent complement mediated cytotoxicity of three novel monoclonal antibodies (mAbs), designated M74, M77, and M79, raised against the colorectal carcinoma antigen 17-1A. As determined by indirect radioimmunoassay, all three mAbs, as well as mAb 17-1A, bound to a similar extent to adherent cultures of the human colon carcinoma cell line, HT-29. Scatchard analysis of direct binding data for mAbs 17-1A, M74, M77, and M79 to HT-29 cells demonstrated equivalent association constants (7.54-9.77 X 10(7) liters/mol) and molecules bound per cell (2.15-2.69 X 10(5)). In contrast to mAbs M77 and M79, mAb M74 inhibited the binding of 125I-labeled mAb 17-1A to HT-29 cells. Similar to mAb 17-1A, incubation of human lymphocytes and blood monocytes with mAbs M74, M77, or M79 generated ADCC activity against HT-29 colon carcinoma cells. Various combinations of noncompeting mAbs to the 17-1A antigen (17-1A and M74; M77 and M79; M74 and either M77 or M79) but not competing mAbs (17-1A and M74; M77 and M79) resulted in a heightened level of ADCC activity. Under optimum conditions (saturation of antigenic sites with mAb), ADCC generated by the combination of noncompeting mAbs to the 17-1A antigen was additive to the activity seen with the respective mAbs alone. Under suboptimum conditions, the combination of noncompeting mAbs to the 17-1A antigen resulted in tumor cell cytotoxicity which was synergistic to the lysis obtained with the respective mAbs alone. No mAb used alone was able to generate antibody dependent complement mediated cytotoxicity against a panel of 17-1A positive colon carcinoma cells. Similarly, no antibody dependent complement mediated cytotoxicity activity was obtained with the combination of competing mAbs to the 17-1A antigen. However, HT-29 cells treated with noncompeting mAbs to the 17-1A antigen antigen were rendered susceptible to lysis by human complement. We conclude that the combination of mAbs recognizing different epitopes on the same tumor antigen could have important implications for the passive immunotherapy of cancer.     

Expression of phospholipases γ1, β1, and δ1 in primary human colon carcinomas and colon carcinoma cell lines

The levels of expression of phosphoinositide-specific phospholipase Cs (PLCs) were examined in a series of primary human colon carcinomas and in eight colon carcinoma cell lines by using monoclonal antibodies and cDNA probes for PLCγ1, PLCβ1, and PLCδ1. Western and northern blot analyses of PLCγ1 revealed elevated expression of this isozyme at both the protein and mRNA levels in most tumors when compared with paired adjacent normal mucosa samples (in 11 of 13 pairs in the western blots and 8 of 9 pairs in the northern blots). On the other hand, decreased levels of the PLCδ1 protein were seen in most colon carcinomas (12 of 13 paired samples). The levels of PLCβ1 protein were too low to detect possible differences between the carcinoma and normal mucosa samples. Relatively high expression of PLCγ1 was found in almost all of the eight human colon carcinoma cell lines at both the protein and mRNA levels. Only weak expression of PLCβ1 was detected in these cell lines, by both western and northern blot analyses, and PLCδ1 protein was not detected in any of the carcinoma cell lines. These findings provide evidence that colon carcinomas display altered expression of individual isoforms of PLCs and suggest that increased expression of PLCγ1 may play an important role in colon carcinogenesis. © 1995 Wiley-Liss Inc.     

Conformational epitopes specific to carcinoembryonic antigen defined by monoclonal antibodies raised against colon cancer xenografts

Four monoclonal antibodies (MoAbs) reactive with carcinoembryonic antigen (CEA) were obtained by hybridizing mouse myeloma cells (P3-X63-Ag8-U1) with spleen cells from nude mice (BALB/c, nu/nu) that had rejected transplanted human colonic adenocarcinomas Co-3 and Co-4 following intraperitoneal injection of spleen cells from immunocompetent mice (BALB/c). By solid-phase RIA with purified CEA and its related antigens, NCC-CO-413 (IgG2a, kappa) was shown to react with NCA and BGP-I as well as with CEA, whereas the reactivities of three other MoAbs, NCC-CO-308 (IgG1, kappa), -432 (IgG1 lambda), and -411 (IgG1, kappa) were limited to CEA. Immunohistochemical reactivities of these MoAbs to colonic carcinomas, granulocytes, and liver bile canaliculi on acetone-fixed paraffin-embedded sections ("AMeX" sections) confirmed the specificities of these MoAbs shown by the solid-phase RIA. By competition solid-phase RIA, the epitopes recognized by NCC-CO-308 and -432 were shown to be shared or located close to each other, whereas the other MoAbs were shown to recognize different epitopes. Thus, two epitopes specific to CEA and one shared by NCA and BGP-I as well as CEA were identified. Furthermore, reactivities of MoAbs with the two CEA-specific epitopes were easily abolished by heat denaturation or reduction of CEA, as revealed by solid-phase RIA and SDS-PAGE-immunoblotting, indicating that these two CEA-specific epitopes are based on the conformational structure of the CEA molecule.     

Identification by monoclonal antibodies of an antigen shed by human bladder cancer cells

The reactivities of two anti-bladder cancer monoclonal antibodies, AN43 and BB369, were characterized. AN43 and BB369 reacted with a majority (greater than 50%) of bladder cancer tissue sections tested by immunoperoxidase staining. When tested against a panel of 27 normal human tissues, AN43 and BB369 reacted only with urothelium and stomach. AN43 and BB369 showed identical binding patterns and competed for binding on bladder cancer cells, suggesting that the two antibodies react with identical or spatially close epitopes. Bound BB369 antibody was rapidly shed from the surface of viable UM-UC-9 human bladder cancer cells. The antigen was found in spent tissue culture medium from the UM-UC-9 human bladder cancer cell line. AN43 and BB369 define a shed bladder tumor-associated antigen with limited distribution on normal tissues. The antigen is different from bladder tumor-associated antigens defined by other monoclonal antibodies and may be useful for the diagnosis and follow-up of patients with bladder cancer.     

Tumor-associated antigen defined by a monoclonal antibody against neuraminidase-treated human cancer cells

A monoclonal antibody, MH-A6, was produced by immunization with a human gastric cancer cell line, MKN 74, treated with neuraminidase. The antigen defined by the monoclonal antibody was detected on various tumor tissues and a limited number of normal tissues in immunoperoxidase assay, and the expression of MH-A6 antigen was not influenced by neuraminidase treatment except for some cases of tumor tissues. Interestingly, neuraminidase treatment enhanced binding of the antibody on some adenocarcinomas, but diminished binding of the antibody on squamous cell carcinomas. Both treatment of the immunizing tissues with trypsin and periodic acid diminished binding of the antibody. In isolation of MH-A6 antigen from MKN 74 cells by the monoclonal antibody coupled-affinity column, the epitope exists on molecules with molecular weights of 30,000 and 72,000, and with an acidic pH range in two-dimensional electrophoresis. CEA and CA 19-9 activities were not detected in purified MH-A6 antigen by solid-phase radioimmunoassay, and the reactivity of the MH-A6 antibody with CEA and CA 19-9 was not detected in enzyme-linked immunosorbent assay. Hemagglutination observed between erythrocytes (Lewisa, Lewisb, or NE-treated) and anti-Lewisa, anti-Lewisb sera, or anti-T-agglutinin (peanut lectin), respectively, was not inhibited by MH-A6 antigen. The results suggest that MH-A6 antigen is a tumor-associated antigen, probably glycoprotein, and different from CEA, CA 19-9, Lewisa, Lewisb, and Thomsen-Friedreich (T) antigen.     

Preparation and identification of monoclonal antibodies against pea albumin 1b (PA 1b)

PA 1b (pea albumin 1b), extracted from pea seeds, is thermostable and is multifunctional. It has an attractive peros toxicity, and is also involved in the regulation of callus growth and cell proliferation. Here we report the preparation of monoclonal antibodies (MAbs) against this peptide for further investigation of peptide distribution and functions. PA 1b was coupled to carrier protein using the two-step glutaraldehyde method as an immunal antigen. Five stable cell lines producing anti-PA 1b MAbs were obtained. We analyzed their isotypes, titer, and affinity and found that those MAbs belong to the G(1) and G(2b) subclasses with kappa light chain, respectively. Using these antibodies, a competitive inhibition ELISA was developed, and approximately 15 nmol/L of antigen was detected.     

Stimulation of glioma-cell migration by laminin and inhibition by anti-α3 and anti-β1 integrin antibodies

An induction of laminin in the confrontation zone between tumor cells and normal brain tissue has been observed in our model systems in vivo and in vitro. In order to study the effects of ECM components on glioma-cell migration and invasion, we have used 2 lacZ-transfected glioma cell lines, ANI/lacZ and U-251/lacZ. Cell migration from multicellular spheroids was studied using different types of media: DMEM with 10% serum, Ultra Culture medium, and filtrated DMEM with serum in which the protein fraction > 100 kDa had been removed by ultrafiltration. Laminin, fibronectin and collagen type-IV were individually added to the different media, and cell migration from the spheroids was studied. The results show that cell migration in both cell lines, was stimulated by laminin and fibronectin. Collagen type-IV stimulated only cell migration of U-251/lacZ cells. Scanning electron microscopy revealed an extensive change in cell shape as a result of laminin stimulation. Flow-cytometric studies showed that both ANI/lacZ and U-251/lacZ strongly express the α3β1 integrin receptor, which can bind to several ECM components (laminin, fibronectin, collagen). Immunofluorescence microscopy demonstrated that the same integrin sub-units were expressed in multicellular spheroids. When monoclonal antibodies to α3 and β1 were added to the laminin-stimulated cultures, cell migration was significantly reduced. This indicates that the α3β1 integrin receptor plays an important role during glioma-cell migration. © 1996 Wiley-Liss, Inc.     

Synergistic actions of atorvastatin with γ‐tocotrienol and celecoxib against human colon cancer HT29 and HCT116 cells

The synergistic actions of atorvastatin (ATST) with γ‐tocotrienol (γ‐TT) and celecoxib (CXIB) were studied in human colon cancer cell lines HT29 and HCT116. The synergistic inhibition of cell growth by ATST and γ‐TT was demonstrated by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and isobologram analysis. δ‐TT exhibited a similar inhibitory action when combined with ATST. Mevalonate and geranylgeranyl pyrophosphate eliminated most of the growth inhibitory effect of ATST, but only marginally decreased that of γ‐TT; whereas farnesyl pyrophosphate and squalene exhibited little effect on the inhibitory action of ATST and γ‐TT, indicating protein geranylgeranylation, but not farnesylation are involved in the inhibition of colon cancer cell growth. Both mevalonate and squalene restored the cellular cholesterol level that was reduced by ATST treatment, but only mevalonate eliminated the cell growth inhibitory effect, suggesting that the cholesterol level in cells does not play an essential role in inhibiting cancer cell growth. Protein level of HMG‐CoA reductase increased after ATST treatment, and the presence of γ‐TT attenuated the elevated level of HMG‐CoA reductase. ATST also decreased membrane‐bound RhoA, possibly due to a reduced level of protein geranylgeranylation; addition of γ‐TT enhanced this effect. The mediation of HMG‐CoA reductase and RhoA provides a possible mechanism for the synergistic action of ATST and γ‐TT. The triple combination of ATST, γ‐TT and CXIB showed a synergistic inhibition of cancer cell growth in MTT assays. The synergistic action of these three compounds was also illustrated by their induction of G₀/G₁ phase cell cycle arrest and apoptosis.     

Common human melanoma-associated antigen(s) detected by monoclonal antibodies

Hybridoma cells have been derived from a fusion between mouse myeloma cells (P3-NSI/1Ag4) and spleen cells from a mouse immunized with membrane-enriched fractions from the human melanoma cell line Me-43. Of the 26 hybrids obtained, seven secreted antibodies which reacted with the melanoma cell line used for immunoassay. The specificity of the antibodies produced by the seven positive hybrids was further investigated on 16 melanoma cell lines, 15 other tumors, and 14 lymphoblastoid cell lines. The antibodies from four positive hybrids showed a broad reactivity, whereas those from three hybrids reacted exclusively with melanoma cells. The antibodies from two of these three hybrids, alpha-Mel/5 and alpha-Mel/14, seem to be directed against common melanoma antigen(s) since they reacted with all (with one exception) of the 16 melanoma cell lines tested only with five of the 16 melanoma lines. Reciprocal binding inhibition tests using [3H]leeucine-labeled antibodies showed that alpha-Mel/5 and alpha-Mel/14 antibodies were directed against different antigenic determinants.     

Detection of human osteosarcoma-associated antigen(s) by monoclonal antibodies

Hybrid cell lines have been derived from a fusion between mouse myeloma cells, NS1, and spleen cells from mice immunized with freshly resected osteosarcoma cells from an untreated patient. Of the 276 hybrids obtained, five secreted antibodies which bound to osteosarcoma tissues but not to autologous skin fibroblasts. The antibodies from three of these five hybrids, OST6, OST7, and OST15, reacted with all of five osteosarcoma tissues and with one chondrosarcoma tissue but not with other malignant or benign tumors. Tests of various normal tissues were negative, except for weak binding to a subpopulation of chondrocytes in articular cartilage. The reciprocal binding inhibition test showed that OST6, OST7, and OST15 antibodies were directed against different antigenic determinants.     

miR‐335 inhibited cell proliferation of lung cancer cells by target Tra2β

Accumulating evidence has suggested that the dysregulation of miRNA is an important factor in the pathogenesis of lung cancer. Here, we demonstrate that miR‐335 expression is reduced in non‐small cell lung cancer (NSCLC) tumors relative to non‐cancerous adjacent tissues, while the expression of Tra2β is increased. In addition, clinical data revealed that the increased Tra2β and decreased miR‐335 expression observed in NSCLC cells was associated with poor patient survival rates. In vitro experimentation showed that the overexpression of miR‐335 inhibited the growth, invasion and migration capabilities of A459 lung cancer cells, by targeting Tra2β. In contrast, inhibition of miR‐335 or overexpression of the Tra2β target gene stimulated the growth, invasion and migratory capabilities of A459 lung cancer cells in vitro. Furthermore, overexpression of miR‐335 or inhibition of Tra2β decreased the phosphorylation of Rb‐S780 and Rb‐AKT. Overall, these findings suggest that the downregulation of miR‐335 in A459 lung cancer cells promoted cell proliferation through upregulation of Tra2β, mediated via activation of the AKT/mTOR signaling pathway, and suggest that miR‐335 may have potential as a novel therapeutic target for NSCLC.     

Pregnancy-associated glycoprotein (α2-pag) - A possible marker in breast cancer?

Serum levels of pregnancy-associated α-glycoprotein (α²-PAG) and estradiol-17β (E₂) and the estrogen receptor content (ER) in the tumor cytosol were measured in 174 women aged 24 to 94 years with primary breast cancer and the values were related to patient age, tumor size and clinical stage. While E₂, levels were significantly lower and ER values significantly higher in older women, no significant correlation was found between α-PAG on one hand and the patients' age, E₂, or ER values or tumor size on the other. A significant positive correlation (p= 0.016, Pearson correlation test) was found between α₂-PAG values and the clinical stage of the tumor. The results suggest the possible use of α₂-PAG as a marker for the monitoring of disseminated breast cancer during systemic therapy.