Adhesion to carcinoembryonic antigen by human colorectal carcinoma cells involves at least two epitopes

Aberrant Glycosylation as Immune Therapeutic Targets for Solid Tumors

Glycosylation occurs at all major types of biomolecules, including proteins, lipids, and RNAs to form glycoproteins, glycolipids, and glycoRNAs in mammalian cells, respectively. The carbohydrate moiety, known as glycans on glycoproteins and glycolipids, is diverse in their compositions and structures. Normal cells have their unique array of glycans or glycome which play pivotal roles in many biological processes. The glycan structures in cancer cells, however, are often altered, some having unique structures which are termed as tumor-associated carbohydrate antigens (TACAs). TACAs as tumor biomarkers are glycan epitopes themselves, or glycoconjugates. Some of those TACAs serve as tumor glyco-biomarkers in clinical practice, while others are the immune therapeutic targets for treatment of cancers. A monoclonal antibody (mAb) to GD2, an intermediate of sialic-acid containing glycosphingolipids, is an example of FDA-approved immune therapy for neuroblastoma indication in young adults and many others. Strategies for targeting the aberrant glycans are currently under development, and some have proceeded to clinical trials. In this review, we summarize the currently established and most promising aberrant glycosylation as therapeutic targets for solid tumors.

Clinical implication of tissue carcinoembryonic antigen expression in association with serum carcinoembryonic antigen in colorectal cancer

This study aimed to evaluate the prognostic significance of carcinoembryonic antigen (CEA) expression in tumor tissues of patients with colorectal cancer (CRC). The cohort included 7,412 patients with CRC from January 2010 to December 2015. Survival outcomes were assessed based on tissue CEA (t-CEA) patterns and intensities. Three-year (76.7% versus 81.3%) and 5-year (71.7% versus 77.6%, p < 0.001) disease-free survival (DFS) rates were significantly (p < 0.001) poorer in patients with a diffuse-cytoplasmic pattern than an apicoluminal pattern. Three-year (79% versus 86.6%) and 5-year (74.6% versus 84.7%) DFS rates were also significantly (p < 0.001) poorer in patients with high than low t-CEA intensity. Three-year (84.6% versus 88.4%) and 5-year (77.3% versus 82.6%) overall survival (OS) rates were significantly (p < 0.001) poorer in patients with diffuse-cytoplasmic than apicoluminal pattern of CEA expression, and both 3-year (86.7% versus 91.2%) and 5-year (80.1% versus 87.7%) OS rates were significantly (p < 0.001) poorer in patients with high than low t-CEA intensity. Multivariate analyses showed that high-intensity t-CEA was independently associated with DFS (p = 0.02; hazard ratio [HR] = 1.233) and OS (p = 0.032; HR = 1.228). Therefore, high-intensity t-CEA is a significant prognostic factor in CRC, independent of serum CEA (s-CEA), and can complement s-CEA in predicting survival outcomes after CRC resection.

Blocking the attachment of cancer cells in vivo with DNA aptamers displaying anti-adhesive properties against the carcinoembryonic antigen

The formation of metastatic foci occurs through a series of cellular events, initiated by the attachment and aggregation of cancer cells leading to the establishment of micrometastases. We report the derivation of synthetic DNA aptamers bearing anti-adhesive properties directed at cancer cells expressing the carcinoembryonic antigen (CEA). Two DNA aptamers targeting the homotypic and heterotypic IgV-like binding domain of CEA were shown to block the cell adhesion properties of CEA, while not recognizing other IgV-like domains of CEACAM family members that share strong sequence and structural homologies. More importantly, the pre-treatment of CEA-expressing tumour cells with these aptamers prior to their intraperitoneal implantation resulted in the prevention of peritoneal tumour foci formation. Taken together, these results highlight the effectiveness of targeting the cell adhesion properties of cancer cells with aptamers in preventing tumour implantation.

A focused immune response targeting the homotypic binding domain of the carcinoembryonic antigen blocks the establishment of tumor foci in vivo

Metastatic forms of cancers remain the main cause of death in cancer patients. In this study, we demonstrate that directing a sustained antibody response towards the homotypic binding function of CEA interferes with the implantation and development of tumor foci in CEA-expressing transgenic (CEA.Tg) mice. Specifically, vaccinating CEA.Tg mice with a recombinant, altered self-form of the CEA Ig V-like N domain led to the production of circulating IgG1 and IgG2a antibodies that inhibited CEA-mediated adhesion of murine carcinoma expressing CEA (MC38.CEA) and mediated antibody-dependent lysis of tumor cells. Moreover, vaccinated CEA.Tg mice were resistant to the development of tumor nodules in the lungs and the peritoneal cavity, suggesting that mounting a focused antibody response to the CEA N domain may represent a simple therapeutic strategy to control the establishment of metastatic foci in cancer patients.

Isolation of carcinoembryonic antigen N-terminal domains (N-A1) from soluble aggregates

Carcinoembryonic antigen (CEA) was identified as a prominent tumor-associated antigen in human colorectal cancer and it is still intensively investigated. However, its physiological role remains unclear. The CEA molecule is composed of seven highly hydrophobic, immunoglobulin-like domains, six of which contain a single disulphide bridge. The production of recombinant protein containing Ig-like domains in bacterial expression systems often results in partial degradation or insolubility due to aggregation hampering the analysis of their native structure and function. Here, we present a new method of expression and purification of CEA N-terminal domains (N-A1) fused to MBP in Escherichia coli. In order to optimize the expression and purification of CEA N-A1 domains we evaluated bacteria cultivation conditions, the length of N-A1 domains, fusion systems (GST- and MBP-tag), IPTG concentrations and protein purification conditions. We have found that MBP-N-A1 fusion protein digested with TEV protease forms soluble aggregates composed of N-A1 domains and incompletely digested MBP-N-A1 fusion protein. Using 1.25 M guanidinium chloride (GdmCl) as a component of the elution buffer we were able to achieve an almost complete dissociation of the aggregates. The dissociation was monitored by circular dichroism and fluorescence measurements. The CD spectra and Ellman's assay suggest that the conformation of N-A1 domains and their disulphide bonds are correct.

Interdependency of CEACAM-1, -3, -6, and -8 induced human neutrophil adhesion to endothelial cells

Members of the carcinoembryonic antigen family (CEACAMs) are widely expressed, and, depending on the tissue, capable of regulating diverse functions including tumor promotion, tumor suppression, angiogenesis, and neutrophil activation. Four members of this family, CEACAM1, CEACAM8, CEACAM6, and CEACAM3 (recognized by CD66a, CD66b, CD66c, and CD66d mAbs, respectively), are expressed on human neutrophils. CD66a, CD66b, CD66c, and CD66d antibodies each increase neutrophil adhesion to human umbilical vein endothelial cell monolayers. This increase in neutrophil adhesion caused by CD66 antibodies is blocked by CD18 mAbs and is associated with upregulation of CD11/CD18 on the neutrophil surface. To examine potential interactions of CEACAMs in neutrophil signaling, the effects on neutrophil adhesion to human umbilical vein endothelial cells of a set of CD66 mAbs was tested following desensitization to stimulation by various combinations of these mAbs. Addition of a CD66 mAb in the absence of calcium results in desensitization of neutrophils to stimulation by that CD66 mAb. The current data show that desensitization of neutrophils to any two CEACAMs results in selective desensitization to those two CEACAMs, while the cells remain responsive to the other two neutrophil CEACAMs. In addition, cells desensitized to CEACAM-3, -6, and -8 were still responsive to stimulation of CEACAM1 by CD66a mAbs. In contrast, desensitization of cells to CEACAM1 and any two of the other CEACAMs left the cells unresponsive to all CD66 mAbs. Cells desensitized to any combination of CEACAMs remained responsive to the unrelated control protein CD63. Thus, while there is significant independence of the four neutrophil CEACAMs in signaling, CEACAM1 appears to play a unique role among the neutrophil CEACAMs. A model in which CEACAMs dimerize to form signaling complexes could accommodate the observations. Similar interactions may occur in other cells expressing CEACAMs.

Carcinoembryonic antigen inhibits anoikis in colorectal carcinoma cells by interfering with TRAIL-R2 (DR5) signaling

Carcinoembryonic antigen (CEA) is a tumor marker that is associated with metastasis, poor response to chemotherapy of colorectal cancer (CRC), and anoikis, a form of apoptosis caused by cell detachment from matrix that is dependent on TRAIL-R2 (DR5) and caspase-8 activation in CRC. Although CEA is a homophilic binding protein that may provide survival signals through homotypical cell aggregation, we now report that CEA binds TRAIL-R2 (DR5) directly in two-hybrid assays to decrease anoikis through the extrinsic pathway. Deletion of the PELPK sequence (delPELPK) of CEA (delPELPK CEA) restores sensitivity to anoikis while it maintains its cell aggregation function. Wild-type (WT) CEA also increases experimental hepatic metastasis, whereas the delPELPK CEA does not. Thus, membrane CEA interacts with DR5 to inhibit anoikis and increase metastatic potential in CRC.

Expression patterns of CEACAM5 and CEACAM6 in primary and metastatic cancers

BACKGROUND

Many breast, pancreatic, colonic and non-small-cell lung carcinoma lines express CEACAM6 (NCA-90) and CEACAM5 (carcinoembryonic antigen, CEA), and antibodies to both can affect tumor cell growth in vitro and in vivo. Here, we compare both antigens as a function of histological phenotype in breast, pancreatic, lung, ovarian, and prostatic cancers, including patient-matched normal, primary tumor, and metastatic breast and colonic cancer specimens.

METHODS

Antigen expression was determined by immunohistochemistry (IHC) using tissue microarrays with MN-15 and MN-3 antibodies targeting the A1B1- and N-domains of CEACAM6, respectively, and the MN-14 antibody targeting the A3B3 domain of CEACAM5. IHC was performed using avidin-biotin-diaminobenzide staining. The average score +/- SD (0 = negative/8 = highest) for each histotype was recorded.

RESULTS

For all tumors, the amount of CEACAM6 expressed was greater than that of CEACAM5, and reflected tumor histotype. In breast tumors, CEACAM6 was highest in papillary > infiltrating ductal > lobular > phyllodes; in pancreatic tumors, moderately-differentiated > well-differentiated > poorly-differentiated tumors; mucinous ovarian adenocarcinomas had almost 3-fold more CEACAM6 than serous ovarian adenocarcinomas; lung adenocarcinomas > squamous tumors; and liver metastases of colonic carcinoma > primary tumors = lymph nodes metastases > normal intestine. However, CEACAM6 expression was similar in prostate cancer and normal tissues. The amount of CEACAM6 in metastatic colon tumors found in liver was higher than in many primary colon tumors. In contrast, CEACAM6 immunostaining of lymph node metastases from breast, colon, or lung tumors was similar to the primary tumor.

CONCLUSION

CEACAM6 expression is elevated in many solid tumors, but variable as a function of histotype. Based on previous work demonstrating a role for CEACAM6 in tumor cell migration, invasion and adhesion, and formation of distant metastases (Blumenthal et al., Cancer Res 65: 8809-8817, 2005), it may be a promising target for antibody-based therapy.

Inhibition of adhesion, invasion, and metastasis by antibodies targeting CEACAM6 (NCA-90) and CEACAM5 (Carcinoembryonic Antigen)

CEACAM5 and CEACAM6 are overexpressed in many cancers and are associated with adhesion and invasion. The effects of three monoclonal antibodies targeting different epitopes on these antigens (NH2-terminal [MN-3] and A1B1 domains [MN-15] shared by CEACAM5 and CEACAM6 and the A3B3 domain [MN-14] restricted to CEACAM5) were evaluated in migration, invasion, and adhesion assays in vitro using a panel of human pancreatic, breast, and colonic cancer cell lines, and in the GW-39 human colonic micrometastasis model in vivo. MN-3 Fab' and MN-15 Fab' were both effective at inhibiting cell migration. MN-15 Fab' treatment inhibited invasion, reducing cell penetration through an extracellular matrix (ECM). MN-3 Fab' also decreased invasion but was less effective than MN-15 Fab' in four of five cell lines. All three monoclonal antibody (mAb) Fabs decreased adhesion of tumor cells to endothelial cells by 49% to 58%. MN-15 Fab' but not MN-3 or MN-14 Fabs induced a decrease in adhesion of three of six cell lines to the ECM protein, fibronectin, but adhesion to vitronectin, laminin, collagen-I, and collagen-IV was not affected. In vivo studies showed that treatment with MN-3 Fab' or MN-15 Fab' of mice implanted with GW-39 human colonic cancer cells increased their survival (P < 0.025 and P < 0.01, respectively). These studies show that antibody Fabs that target either CEACAM5 or CEACAM6 affect cell migration, cell invasion, and cell adhesion in vitro, and that MN-15 and MN-3 Fabs have antimetastatic effects in vivo, resulting in improved survival of mice with metastases. Thus, blocking the N and A1B1 domains of CEACAM5/CEACAM6 can impede the metastatic process.

[Diagnosis of septic loosening of hip prosthesis with LeukoScan. SPECT scan with 99mTc-labeled monoclonal antibodies]

Diagnosis of septic loosening of hip endoprosthesis with antigranulocyte scintigraphy (AGS) was analysed. Twenty-one hip prostheses were studied using laboratory tests and, in cases of elevated values, three-phase bone scan (BS) and AGS. Elective SPECT/CT scans were performed. Histologic and microbiologic exams verified the diagnosis. The AGS analysis revealed sensitivity, specificity and accuracy of value 1, while positive and negative predictive values were also 1. BS showed sensitivity of 1 and specificity of 0.33. In three cases, SPECT/CT scans corroborated the AGS interpretation. This diagnostic algorithm proved effective in the detection of septic loosening of hip prostheses. AGS can be avoided without risk of infection being overlooked.

Carcinoembryonic antigen promotes tumor cell survival in liver through an IL-10-dependent pathway

Most circulating tumor cells die within 24 h of entering the hepatic microvasculature because their arrest initiates an ischemia-reperfusion (I/R) injury that is cytotoxic. Human colorectal carcinomas (CRC) produce the glycoprotein Carcinoembryonic Antigen (CEA) that increases experimental liver metastasis in nude mice. Since CEA induces release of IL-6 and IL-10, we hypothesized that CEA inhibits the I/R injury through a Kupffer cell-mediated cytokine-dependent pathway. We assessed cytokine effects in CRC co-cultured with liver and in vivo. Human CRC prelabeled with fluorescent dyes were incubated with a reoxygenated suspension of ischemic nude mouse liver fragments in a bioreactor. CEA, rhIL-6 or rhIL-10 were either administered to the donor mice prior to hepatic ischemia or during co-culture. Liver donors were athymic nude or iNOS, IL-6 or IL-10 knock out mice. Ischemic-reoxygenated liver kills Clone A CRC through production of nitric oxide (NO) and superoxide anion. Treatment of liver donors with CEA prior to hepatic ischemia inhibited this in vitro cytotoxicity through an IL-10 and Kupffer cell dependent pathway that inhibited NF-kappaB activation, NO production and iNOS upregulation. IL-10 but not IL-6 enhanced CRC survival in nude mouse liver in vivo. Thus, CEA enhanced metastasis by inducing IL-10 to inhibit iNOS upregulation in host liver.

Carcinoembryonic antigen facilitates experimental metastasis through a mechanism that does not involve adhesion to liver cells

Carcinoembryonic antigen (CEA) injected intravenously into athymic nude mice increases the ability of weakly metastatic human colorectal carcinoma (CRC) cells to colonize liver in an experimental metastasis assay. Since CEA acts as an intercellular adhesion molecule in vitro, several investigators have postulated that this facilitation of experimental metastasis may be mediated through adhesion between CEA on CRC and CEA-binding proteins on Kupffer or other cells lining the hepatic sinusoid. The present work tested this postulate both by intravital fluorescence videomicroscopy in vivo and in adhesion assays in vitro to enriched populations of Kupffer cells and hepatic sinusoidal endothelial cells (SEC). The data indicate that CEA expression does not effect adhesion to enriched Kupffer cells or SEC in vitro. These data suggest that CEA enhances liver colonization through another mechanism, possibly one that involves modulation of the hepatic response to tumor cell implantation.

Carcino-embryonic antigen may function as a chemo-attractant in colorectal-carcinoma cell lines

Locomotion of colorectal-carcinoma cells was tested in order to establish whether it might be affected by carcino-embryonic antigen (CEA). CEA production, cell growth and DNA ploidy were measured in 22 colorectal-carcinoma cell lines. A cell-invasion assay was adapted using a transfilter chamber, the lower surface of which was coated with various substrates in the amount of 5 microgram/filter (CEA, type-IV collagen, laminin). Cells infiltrated into the lower surface of the filter were counted over 9-microscope fields (x400). All cell lines produced CEA, 9 producing more than 100 ng/ml medium. Of the total, 8 cell lines were diploid and 14 were aneuploid. Invasiveness, measured by the number of infiltrated cells, was highest in CEA-coated filters, and next highest in type-IV-collagen- and laminin-coated filters, in descending order (p < 0.001-0.05). Invasiveness of each cell line was closely correlated with 2 substrates. Poorly differentiated or advanced-stage tumors were more invasive than well-differentiated or early-stage tumors (p < 0.001-0. 05). However, invasiveness was not associated with DNA ploidy or CEA production. CEA may function as a chemo-attractant as well as an adhesion molecule in colorectal-carcinoma cell lines. In addition, adhesion to CEA appears to be related to type-IV collagen and laminin.

Involvement of circulating CEA in liver metastases from colorectal cancers re-examined in a new experimental model

Both experimental and clinical data show evidence of a correlation between elevated blood levels of carcinoembryonic antigen (CEA) and the development of liver metastases from colorectal carcinomas. However, a cause-effect relationship between these two observations has not been demonstrated. For this reason, we developed a new experimental model to evaluate the possible role of circulating CEA in the facilitation of liver metastases. A CEA-negative subclone from the human colon carcinoma cell line CO115 was transfected either with CEA-cDNA truncated at its 3' end by the deletion of 78 base pairs leading to the synthesis of a secreted form of CEA or with a full-length CEA-cDNA leading to the synthesis of the entire CEA molecule linked to the cell surface by a GPI anchor. Transfectants were selected either for their high CEA secretion (clone CO115-2C2 secreting up to 13 microg CEA per 10(6) cells within 72 h) or for their high CEA membrane expression (clone CO115-5F12 expressing up to 1 x 10(6) CEA molecules per cell). When grafted subcutaneously, CO115-2C2 cells gave rise to circulating CEA levels that were directly related to the tumour volume (from 100 to 1000 ng ml(-1) for tumours ranging from 100 to 1000 mm3), whereas no circulating CEA was detectable in CO115 and CO115-5F12 tumour-bearing mice. Three series of nude mice bearing a subcutaneous xenograft from either clone CO115-2C2 or the CO115-5F12 transfectant, or an untransfected CO115 xenograft, were further challenged for induction of experimental liver metastases by intrasplenic injection of three different CEA-expressing human colorectal carcinoma cell lines (LoVo, LS174T or CO112). The number and size of the liver metastases were shown to be independent of the circulating CEA levels induced by the subcutaneous CEA secreting clone (CO115-2C2), but they were directly related to the metastatic properties of the intrasplenically injected tumour cells.

Distribution of carcinoembryonic antigen and biologic behavior in colorectal carcinoma

PURPOSE

Carcinoembryonic antigen is assumed from the results of several experiments to be associated with invasion of colorectal carcinoma by adhesion or contact inhibition. The patterns and the intensity of carcinoembryonic antigen distribution in colorectal carcinoma were assessed to verify whether they were correlated with malignant potential from those biologic characteristics.

METHODS

Carcinoembryonic antigen distribution was tested in the archival samples of 149 colorectal carcinomas by immunohistochemistry, using three characterized anti-carcinoembryonic antigen monoclonal antibodies: T84.66, PR1A3, and PR3B10. The distribution patterns in neoplastic tissue were categorized into unstained, apicoluminal, and diffuse cytoplasmic patterns. Tumor, invasive tumor margin, and tissue surrounding the tumor were examined.

RESULTS

Although all three antibodies revealed a positive correlation, T84.66 showed better discrimination than the others. Although none of the negative staining of the tumor or invasive tumor margin showed recurrence, the apicoluminal pattern showed recurrence, and the diffuse pattern showed the most frequent recurrence (P < 0.01). Recurrence was also associated with staining intensity in the apicoluminal pattern in both the tumor and invasive tumor margin (P < 0.05). Infiltrative tumor growth and lymph node metastasis were more frequent in cases of positive staining in tissue surrounding the tumor. Patients with the apicoluminal pattern achieved longer survival than patients with the diffuse-cytoplasmic pattern in the invasive tumor margin (P = 0.024) by a multivariate analysis including tumor stage and histologic differentiation.

CONCLUSION

The distribution of carcinoembryonic antigen in tumors and surrounding tissue seems to be closely correlated with invasiveness and metastatic behavior in colorectal carcinoma. Carcinoembryonic antigen immune staining can be considered as an efficient tool to determine groups with risk of recurrence.

Epitope mapping of monoclonal antibodies against N-domain of carcinoembryonic antigen

Monoclonal antibodies (MoAbs) against N-domain of carcinoembryonic antigen (CEA), C249, K348, K1338, and K1444, that inhibit CEA-mediated cell adhesion, did not crossreact with nonspecific cross-reacting antigen (NCA). To determine amino acid sequences involved in the adhesion, epitopes of the MoAbs were mapped with recombinant NCAs carrying CEA-NCA chimeric N-domain. The data showed that the epitopes of C249, K1338, K1444 are located within the regions 1-32, 1-32, and 33-59 of CEA, respectively, and that two discrete regions 1-32 and 60-93 may be related to the epitope of K348. Comparison of amino acid sequences between CEA and NCA suggested that four residues (21, 27-29), eight residues (21, 27-29, 66, 78, 79, 89), and three residues (43, 44, 46) are important for recognition by C249 (or K1338), K348, and K1444, respectively. These residues seem to participate in the cell adhesion mediated by CEA.

Oligomerization of N-terminal domain of carcinoembryonic antigen (CEA) expressed in Escherichia coli

The N-terminal domain of CEA, which is essential for cell adhesion activity and lacks cysteine residue, was expressed in Escherichia coli and purified from the solubilized inclusion bodies by DEAE-Sepharose and gel filtration chromatographies. The purified N-domain migrated in SDS-PAGE as a single 13-kDa band, whereas it migrated in non-SDS-PAGE as five distinct bands. The N-domain, analyzed by two-dimensional PAGE after cross-linking with DSS, migrated in multiple forms ranging from monomer to pentamer, showing unequivocally the presence of multimers in each band. The amount of monomer was distinctively the least among the oligomers in the non-SDS-PAGE. These results suggest that the N-domain of CEA molecule has a strong tendency to self-assemble that may convey the homophilic cell adhesion of CEA.

Adhesive function of carcinoembryonic antigen in the liver metastasis of KM-12c colon carcinoma cell line

PURPOSE

Both experimental and clinical results reveal that carcinoembryonic antigen (CEA) seems to mediate some important role in the liver metastasis of colorectal carcinoma cells. The intent of this study was to verify whether adhesive function of CEA might affect liver metastasis in the CEA-expressing colon carcinoma cell line, KM-12c.

METHODS

The hepatic binding of [125I]iododeoxyuridine KM-12c cells was measured with or without intravenous CEA pretreatment in four nude mice each. Then, 2 x 10(6) cells of KM-12c were injected into the splenic subcapsule of 57 CEA-pretreated nude mice. KM-12c cells were prepared in phosphate-buffered saline (control, 27 mice) or anti-CEA monoclonal antibody, T84.66 (30 mice). All mice were killed at the end of the eighth week after implant, and tumor nodules were confirmed histologically.

RESULTS

Marginal differences of hepatic sequestration were found between the CEA-pretreated mice and the control group. Splenic tumor occurred in 75 percent (18/24) of the control group and in 40 percent (10/25) of the T84.66-pretreated group (P = 0.0107). Forty-two percent (10/24) incurred liver metastasis in the control group, whereas 20 percent (5/25) did so in the T84.66-pretreated group. The number of splenic tumor cells was significantly related to the number and volume of liver metastasis (P = 0.0065).

CONCLUSIONS

CEA enhanced liver metastasis predominantly by successful primary tumor implant, whereas primary hepatic entrapment also supported it to some extent in a weakly metastatic colon carcinoma cell line, KM-12c. Tumor cell aggregates seem to be mediated by homophilic binding of CEA molecules, and it is an important mechanism to yield liver metastasis.

Induction of carcinoembryonic antigen expression in a three-dimensional culture system

MIP-101 is a poorly differentiated human colon carcinoma cell line established from ascites that produces minimal amounts of carcinoembryonic antigen (CEA), a 180 kDa glycoprotein tumor marker, and nonspecific cross-reacting antigen (NCA), a related protein that has 50 and 90 kDa isoforms, in monolayer culture. However, MIP-101 produces CEA when implanted into the peritoneum of nude mice but not when implanted into subcutaneous tissue. We tested whether three-dimensional (3D) growth was a sufficient stimulus to produce CEA and NCA 50/90 in MIP-101 cells, because cells grow in 3D in vivo rather than in two-dimensions (2D) as occurs in monolayer cultures. To do this, MIP-101 cells were cultured on microcarrier beads in 3D cultures, either in static cultures as nonadherent aggregates or under dynamic conditions in a NASA-designed low shear stress bioreactor. MIP-101 cells proliferated well under all three conditions and increased CEA and NCA production three- to four-fold when grown in 3D cultures compared to MIP-101 cells growing logarithmically in monolayers. These results suggest that 3D growth in vitro simulates tumor function in vivo and that 3D growth by itself may enhance production of molecules that are associated with the metastatic process.

Association between sucrase-isomaltase and p53 expression in colorectal cancer

BACKGROUND

Sucrase-isomaltase (SI) is a tissue-based phenotypic marker that is an independent prognostic factor in colorectal cancer (CRC). DF3 and galectin 3 are two other tissue-based markers that are upregulated during neoplastic transformation. Because p53 mutations are acquired during neoplastic progression, we reasoned that alterations in SI and p53 may be associated despite an apparent lack of biological interaction.

METHODS

Paraffin sections from 183 patients who underwent surgery at New England Deaconess Hospital (NEDH) between 1965 and 1977 were analyzed first by immunohistochemistry (IHC) for the expression of the markers SI, DF3, and galectin 3, which were scored as absent or present. Paraffin sections from a second group of 59 patients who underwent surgery at NEDH between 1985 and 1992 were analyzed by IHC for the expression of p53 as well as SI, DF3, and galectin 3. p53 nuclear staining was scored as absent or present. Previous work has shown that p53 is mutated in all cells with nuclear staining and in 10% of tumors that are unstained.

RESULTS

SI expression was not associated with the expression of either DF3 or galectin 3, and neither DF3 nor galectin 3 were prognostic factors in CRC. None of the phenotypic markers were associated with any of the clinicopathologic variables. However, 21 of 24 p53-positive cases (88%) expressed SI, whereas 15 of 35 p53-negative cases (43%) were also SI negative (p = 0.02, Fisher exact test). p53 expression was not associated with expression of DF3 or galectin 3.

CONCLUSIONS

SI expression and p53 mutation are associated significantly in CRC. Although the mechanism underlying such an association in presently unknown, the association may define a subset of patients with a worse prognosis.

Binding reactivity of monoclonal anti-carcinoembryonic antigen (CEA) antibodies with cell membrane-bound CEA and with free CEA in solution

Binding reactivities of 62 anti-CEA MAbs from 10 different research groups with cell membrane-bound CEA and with free CEA in solution were compared by inhibition of MAb binding to CEA-expressing tumor cells by free CEA. Bindings of 30 MAbs to the cell membrane-bound CEA (280 ng CEA/2 x 10(5) cells) were inhibited by approximately equal amounts of free CEA, indicating that binding affinities of about half the MAbs for cell membrane-bound CEA are similar to those for free CEA, respectively. Bindings of 15 MAbs to the cell membrane-bound CEA were easily inhibited by free CEA of less than half the amount of the cell membrane-bound CEA, while inhibition of bindings of the remaining 17 MAbs required twice more free CEA than the amount of cell membrane-bound CEA, showing that about one-fourth of the MAbs have higher affinities for free CEA and the remaining about one-fourth of the MAbs possess higher affinities for cell membrane-bound CEA. These results help form the basis for selecting the anti-CEA MAbs for use in clinical applications, such as serum CEA assay, tumor imaging and immunotherapy.

Adhesion or anti-adhesion in cancer: what matters more?

The regulation of adhesion processes between normal epithelial cells is an essential condition for the maintenance of appropriate tissular architecture and differentiation. Quantitative and qualitative alterations in these homotypic adhesions occur during the transformation of normal into malignant epithelium. How these complex alterations in various homotypic adhesions modify the ability of tumor cells to detach from the original neoplastic site, to grow and move as single or clumped cells, and to invade the stroma are current issues in tumor biology. This review contrasts tumor cell adhesion mediated by E-cadherin which is consistently decreased in carcinomas, with adhesion mediated by CD44 and CEA which are increased in the tumors. A model proposing to resolve the apparent paradox of simultaneous adhesion and anti-adhesion mediated by the same protein is proposed.

A reference of the GOLD classification of monoclonal antibodies against carcinoembryonic antigen to the domain structure of the carcinoembryonic antigen molecule

The epitopes of 42 well-characterized monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) from 10 different research groups were mapped in terms of domain structure (domains N, A1-B1, A2-B2, and A3-B3) of the CEA molecule on the basis of the reactivities with recombinant CEA proteins expressed in Chinese hamster ovary cells. Thirty-six of the 42 MAbs tested have previously been classified into 5 essentially nonoverlapping epitope groups (GOLD 1-5) by cross-competition assays among MAbs for CEA binding (Hammarström S, et al.: Cancer Res. 1989; 49:4852-4858). The epitopes recognized by GOLD 2 MAbs were all present on domain A2-B2, those for GOLD 5 MAbs were all on domain N, and those for GOLD 4 were mapped around domains A1-B1 and A2-B2. On the other hand, the epitopes for GOLD 1 MAbs were distributed into domains N, A2-B2, and A3-B3, and those for GOLD 3 MAbs were separated into domains N and A3-B3. Although the exact reasons for the dispersed patterns of GOLD 1 and 3 MAbs on the domain structure of the CEA molecule are unclear at present, several factors, such as a spatial relation or a close proximity of epitopes, conformation dependency, and repetitivity of epitopes, may be considered as possible explanations. The epitope mapping reported here helps form the basis for understanding the relation between the chemical structure and antigenic activities of the CEA molecule and may be useful to study the functions of the CEA molecule, especially those of the respective domains.

A rapid colorimetric assay for carcinoembryonic antigen (CEA)-mediated cell adhesion and analysis of CEA domains involved in the adhesion

A colorimetric microadhesion assay that allows the quantitative determination of carcinoembryonic antigen (CEA)-mediated homophilic cell adhesion to CEA immobilized on 96-well polyvinyl chloride plates is described. Chinese hamster ovary (CHO) cells transfected with a full-length CEA cDNA were used as indicator cells. After dislodging nonadherent cells, specifically bound cells were quantified by a colorimetric analysis based on the ability of live cells to reduce the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to a blue formazan product. The domains of CEA responsible for the homophilic cell adhesion were analyzed by inhibition assays using anti-CEA monoclonal antibodies whose reactive domains were already known. The involvement of domain N and possibly subdomain A3 of CEA in the homophilic cell adhesion has been suggested.

Normal colonic epithelium adheres to carcinoembryonic antigen and type IV collagen

BACKGROUND/AIMS

Human colorectal carcinoma cells bind to collagen and laminin in the basement membrane as well as to carcinoembryonic antigen (CEA) on neighboring cells. The purpose of this study was to determine whether normal colonic epithelial cells bind to CEA, collagen, or laminin.

METHODS

Intact colonic crypts were isolated from normal mucosa in 13 specimens resected for colorectal carcinoma or colonic diverticulitis. Colonocytes were released from the crypts by treatment with collagenase and deoxyribonuclease and tested for adhesion to CEA, type IV collagen, and laminin in a solid-phase adhesion assay.

RESULTS

Twelve percent to 25% of colonocytes in all specimens bound to CEA. Colonocytes from seven specimens also bound to type IV collagen, but none of the colonocyte preparations bound significantly to laminin. Monoclonal antibodies to CEA and to the hyaluronate receptor CD44 and enzymatic removal of membrane CEA blocked the adhesion of colonocytes to CEA.

CONCLUSIONS

First, colonocytes use the same epitopes on CEA and CD44 as colorectal carcinoma cells to adhere to solid-phase CEA. Second, colonocytes bind to solid-phase CEA through CEA-to-CEA homophilic binding. Third, CEA and type IV collagen, but not laminin, are adhesion ligands for human colonocytes.