Active production and membrane anchoring of carcinoembryonic antigen observed in normal colon mucosa

Clinical utility of the carcinoembryonic antigen level in patients with stage III colon cancer after surgery and adjuvant chemotherapy

PURPOSE

The association between perioperative and post-adjuvant carcinoembryonic antigen (CEA) levels and recurrence and prognosis remains unclear. We aimed to evaluate whether perioperative CEA levels are an integral component of the assessment of recurrence and prognosis of patients with stage III colon cancer (CC).

METHODS

This retrospective study was conducted at the Cancer Institute Hospital of the Japanese Foundation for Cancer Research from 2005 to 2013. We enrolled patients with stage III CC who underwent complete resection of a primary tumor and received adjuvant chemotherapy. We analyzed the association between perioperative and post-adjuvant CEA levels and recurrence-free survival (RFS) and overall survival (OS).

RESULTS

A total of 564 consecutive patients were included in the analysis. The RFS and OS of patients with high postoperative CEA levels were significantly worse than those of patients with normal postoperative CEA levels. In the multivariate analysis, high postoperative CEA levels were associated with shorter RFS and OS. The number of risk factors, postoperative CEA levels, and T/N-stage all had a cumulative effect on RFS and OS.

CONCLUSIONS

High postoperative CEA levels and the number of risk factors are associated with recurrence and worse prognosis for patients with stage III CC.

A case of stercoral colitis with marked elevation of serum carcinoembryonic antigen

It should be noted that the serum CEA level can become elevated in severe stercoral colitis. Marked elevation of the serum CEA level in stercoral colitis may suggest the necessity of surgery in patients with stercoral colitis.

Healthy individuals have T-cell and antibody responses to the tumor antigen cyclin B1 that when elicited in mice protect from cancer

We previously identified the aberrantly expressed cell cycle regulator cyclin B1 as a tumor antigen recognized by antibodies and T cells from patients with breast, lung, and head and neck cancers. Ordinarily expressed only transiently in the G2/M stage of the cell cycle in normal cells, cyclin B1 is constitutively expressed at high levels in the cytoplasm of these and many other tumor types, leading to its recognition by the cancer patient's immune system. We report here an unexpected observation that cyclin B1-specific antibody and memory CD4 and CD8 T cells are also found in many healthy individuals who have no history of cancer. Moreover, young as well as older healthy people have these responses suggesting that events other than cancer, which occur either early in life or throughout life, may lead to aberrant cyclin B1 expression and anti-cyclin B1 immunity. The role, if any, of immunity to this tumor-associated antigen is not known. We wanted to determine specifically whether immunity to cyclin B1 might be important in the immunosurveillance of cyclin B1+ tumors. We therefore tested in mice the effectiveness of vaccine-elicited anti-cyclin B1 immunity against a cyclin B1+ mouse tumor that was chosen based on our published observation that cyclin B1 overexpression is associated with the lack of p53 function. We found that cyclin B1 DNA prime-protein boost vaccine protected mice from a challenge with a tumor cell line that was established from a tumor arising in the p53(-/-) mouse that spontaneously overexpresses cyclin B1.

Eotaxin-2 and colorectal cancer: a potential target for immune therapy

PURPOSE

To study the production of chemokines by colorectal hepatic metastases.

EXPERIMENTAL DESIGN

Biopsies of resected colorectal hepatic metastases and nonneoplastic adjacent liver tissue were screened for chemokines using protein arrays and results were confirmed by ELISA and immunohistochemistry.

RESULTS

Two chemokines, eotaxin-2 and MCP-1, were found at elevated levels within the tumor biopsy compared with adjacent liver. The relative increase in expression from tumor was much higher for eotaxin-2 than MCP-1, with 10 of 25 donors having a >100-fold increase in expression compared with 0 of 24 donors for MCP-1. In a parallel analysis, eotaxin-2 was also found at elevated levels in the tumor region of primary colorectal cancer biopsies. Immunohistochemical staining indicated that carcinoembryonic antigen-positive tumor cells stained strongly for eotaxin-2, implicating these cells as the predominant source of the chemokine. In vitro studies confirmed that several colorectal tumor lines produce eotaxin-2 and that secretion of this chemokine could be depressed by IFN-gamma and enhanced by the Th2-type cytokines interleukin-4 and interleukin-13. Jurkat T cells were engineered to express the receptor for eotaxin-2 (CCR3). These cells effectively migrated in response to eotaxin-2 protein, suggesting that immune cells gene modified to express a chemokine receptor may have improved abilities to home to tumor.

CONCLUSIONS

Taken together, these observations confirm eotaxin-2 as a chemokine strongly associated with primary and metastatic tumors of colorectal origin. Furthermore, the importance of this result may be a useful tool in the development of targeted therapeutic approaches to colorectal tumors.

Different Forms of Helper Tolerance to Carcinoembryonic Antigen: Ignorance and Regulation

PURPOSE

Understanding the mechanisms of immune tolerance to tumor-associated antigens (TAA) is an important step in the design of cancer immunotherapy. The aim was to determine how T helper (Th) cell tolerance is mediated for a prototypic TAA, carcinoembryonic antigen (CEA).

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells from 50 healthy volunteers were stimulated with CEA, and the type and fine specificity of any Th cell responses were identified. The inhibitory effects of T regulatory (Tr) populations were determined by depleting "natural" CD25(+) Tr cells or neutralizing cytokine produced by the "induced" Tr form.

RESULTS

Proliferative Th cell responses were consistently induced by CEA in 22 of 50 individuals. Responding cells were drawn from the CD45RA(+) "naive" or quiescent population. Depleting the CD25(+) fraction did not enhance CEA responsiveness. However, CEA elicited secretion of the Tr cytokine interleukin-10 (IL-10) in 23 of 50 donors, including 20 of 22 where no proliferation was induced. Neutralizing IL-10 revealed previously unseen proliferation to CEA by CD45RO(+) "memory" Th cells. Epitope maps revealed differences in the fine specificities of Th cells capable of proliferating or secreting IL-10.

CONCLUSIONS

There are at least two major forms of CEA tolerance in different individuals. One is "ignorance," a failure of specific Th cells to respond to antigen presented in vivo. The other, seen when ignorance is lost, is mediated by IL-10-secreting Tr cells that recognize CEA. TAA tolerance, for example to colorectal carcinoma cells expressing CEA, may be overcome by peptide vaccines that exploit the differences in epitopes recognized by effector and Tr responses.

Tissue ischemia time affects gene and protein expression patterns within minutes following surgical tumor excision

The aim of this study was to determine the impact of ischemia on gene and protein expression profiles of healthy and malignant colon tissue and, thus, on screening studies for identification of molecular targets and diagnostic molecular patterns. Healthy and malignant colon tissue were snap-frozen at various time points (3-30 min) after colon resection. Gene and protein expression were determined by microarray (HG-U133A chips) and surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) technology (CM10 chips, SAX2 chips, and IMAC3Ni chips), respectively. Real-time reverse transcription PCR (RT-PCR) was used for comparative measurement of expression of particular genes. Initial changes of gene and protein expression profiles were already observed 5-8 min after colon resection. Fifteen minutes after surgery, 10%-15% of molecules, and after 30 min, 20% of all detectable genes and proteins, respectively, differed significantly from the baseline values. Significant changes of expression were found in most functional groups. As confirmed by real-time RT-PCR, this included not only known hypoxia-related molecules (HIF-1 alpha, c-fos, HO-1) but also cytoskeletal genes (e.g., CK20) and tumor-associated antigens (e.g., CEA). In conclusion, preanalytical factors, such as tissue ischemia time, dramatically affect molecular data. Control of these variables is mandatory to obtain reliable data in screening programs for molecular targets and diagnostic molecular patterns.

Replacement and Suicide Gene Therapy for Targeted Treatment of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the developed world; consequently, novel therapeutic strategies are in high demand. A major problem with the present treatment modalities is the lack of tumor specificity giving rise to dose-limiting toxicity and side effects. Gene therapy constitutes an experimental approach gaining increased attention as a putative future cancer therapeutic strategy. Using this strategy, cancer cytotoxicity can be obtained by replacing mutated genes with functional analogues or introducing a suicide gene into the malignant cells. Insight into the molecular biology of cancer cells has identified a number of regulatory gene sequences, which can be used to selectively activate the therapeutic gene specifically in cancer cells, thereby reducing nonspecific toxicity. Although further improvements are necessary, recent encouraging results have shown promise for future clinical application of gene therapy. This article presents an update on the experimental and clinical results obtained within the field of lung cancer gene therapy, concentrating on strategies to specifically activate expression of the therapeutic gene in cancer cells. Furthermore, status of the development of delivery vector constructs for lung cancer gene therapy will be presented.

Ascitic fluid carcinoembryonic antigen and alkaline phosphatase levels for the differentiation of primary from secondary bacterial peritonitis with intestinal perforation

BACKGROUND/AIMS

In cirrhotic patients, spontaneous bacterial peritonitis (SBP) may be difficult to distinguish from secondary peritonitis with occult intestinal perforation; Runyon's criteria (based on ascitic fluid glucose, protein and lactate dehydrogenase levels) are sensitive but not specific. Ascitic fluid carcinoembryonic antigen (CEA) and alkaline phosphatase (AP) are potential markers for secondary peritonitis.

METHODS

Ascitic fluid CEA and AP levels were prospectively compared among three subject groups--cirrhotic patients with sterile ascites, cirrhotic patients with SBP, and patients (cirrhotic and non-cirrhotic) with perforation-related secondary peritonitis.

RESULTS

The secondary peritonitis group (n = 38 including 11 cirrhotic patients) had significantly higher mean CEA and AP levels than the SBP (n = 34) and sterile ascites patients (n = 63). Of secondary peritonitis patients, 92% fulfilled predetermined criteria (either CEA >5 ng/ml or AP >240 units/l) versus only 12% of SBP patients; sensitivity was 92% and specificity 88% for differentiating secondary peritonitis from SBP. Runyon's criteria had a sensitivity of 97% and specificity of 56%. Stratification of secondary peritonitis patients by the presence or absence of cirrhosis did not alter our results.

CONCLUSIONS

Ascitic fluid CEA or AP elevations appear to be sensitive and specific markers for perforation-related secondary peritonitis in cirrhotic as well as non-cirrhotic patients.

Carcinoembryonic antigen family members CEACAM6 and CEACAM7 are differentially expressed in normal tissues and oppositely deregulated in hyperplastic colorectal polyps and early adenomas

Four members of the carcinoembryonic antigen (CEA) family, CEA, CEACAM1 (BGP), CEACAM6 (NCA-50/90), and CEACAM7 (CGM2), are coexpressed in normal colorectal epithelia but are deregulated in colorectal cancers, where they could play a role in tumorigenesis. As a basis for functional studies, their expression patterns in normal tissues first need to be clarified. This is well documented for CEACAM1 and CEA but not for CEACAM6 or CEACAM7. We have now carried out immunohistochemical expression studies on 35 different organs, using CEACAM6-specific (9A6) and CEACAM7-specific (BAC2) monoclonal antibodies. CEACAM7 was only found on the apical surface of highly differentiated epithelial cells in the colorectal mucosa and on isolated ductal epithelial cells within the pancreas. CEACAM6 was expressed in granulocytes and epithelia from various organs. CEACAM6 and CEACAM7 expression correlated with apoptosis at the table region of the normal colon, and both were absent from highly proliferating cells at the base of colonic crypts. CEACAM6 revealed a broader expression zone in proliferating cells in hyperplastic polyps and adenomas compared with normal mucosa, whereas CEACAM7 was completely absent. Down-regulation of CEACAM7 and up-regulation of CEACAM6 expression in hyperplastic polyps and early adenomas represent some of the earliest observable molecular events leading to colorectal tumors.

Comparison of carcinoembryonic antigen promoter regions isolated from human colorectal carcinoma and normal adjacent mucosa to induce strong tumor-selective gene expression

To establish in vivo gene therapy against cancer, it is requisite to induce strong, cancer cell-selective expression of a therapeutic gene. Comparison of the promoter activity of 5' flanking regions of the carcinoembryonic antigen (CEA) gene isolated from various origins is therefore of considerable interest. The 5' flanking region of the CEA gene between -135 and +69 bp upstream from the transcriptional start site, which is recognized as the core promoter region, was isolated from CEA-producing human colorectal carcinoma (CRC), normal adjacent mucosa, CEA-producing cell lines and CEA-non-producing cell lines. No mutations were observed by single-strand conformation polymorphism in the CEA promoter regions. Subsequent sequence analysis revealed that there were no mutations in the CEA promoter regions isolated from CEA-producing CRC and normal adjacent mucosa. Furthermore, nuclear extracts prepared from CEA-producing human CRC cells could equally bind to both the CEA promoter fragments isolated from CEA-producing CRC and normal mucosa. Both CEA promoter regions could direct 5- to 20-fold higher expression of a luciferase reporter gene in CEA-producing cells than in CEA-non-producing cells. Therefore, we suggest that the use of either CEA promoter region isolated from CRC or normal mucosa is equally effective to induce strong, CEA-producing cancer-selective expression of a therapeutic gene.

Spread of colorectal cancer micrometastases in regional lymph nodes by reverse transcriptase-polymerase chain reactions for carcinoembryonic antigen and cytokeratin 20

BACKGROUND AND OBJECTIVES

Lymph node metastasis is known as a significant predictor of prognosis in colorectal cancer patients. Recently, reverse transcriptase polymerase chain reaction (RT-PCR) has been applied to detecting micrometastasis. To assess the risk of recurrence and accurately determine the spread of tumor cells, we examined lymph node micrometastases in a series of colorectal cancer patients.

METHODS

We examined 202 lymph nodes obtained from 13 colorectal cancer patients who underwent curative operation and were histologically diagnosed to be node-negative, using RT-PCR to amplify mRNAs for two epithelial markers, carcinoembryonic antigen (CEA) and cytokeratin 20 (CK-20).

RESULTS

All the cases, including early stage patients, had micrometastases. A total of 102 among 202 lymph nodes (50.5%) were positive for either CEA or CK-20, or both (47.0, 40.1, and 36.6% respectively). Positive lymph nodes were spread along the courses of vascular trunks as well as being located in more distant regions.

CONCLUSIONS

Even in histologically negative lymph nodes, there is a considerable possibility that micrometastases may exist. Their detection by RT-PCR may improve clinical staging and indications for cancer therapy. We should also take care in the choice of surgical approach.

Expression of four CEA family antigens (CEA, NCA, BGP and CGM2) in normal and cancerous gastric epithelial cells: up-regulation of BGP and CGM2 in carcinomas

Four human carcinoembryonic antigen (CEA) family members, CEA (CD66e), non-specific cross-reacting antigen (NCA, CD66c), biliary glycoprotein (BGP, CD66a) and CEA gene-family member 2 (CGM2), are expressed in normal mucosal epithelia of the colon. Expression of BGP and CGM2 has recently been demonstrated to be down-regulated in colorectal adenocarcinomas. We have now investigated the expression of the 4 CEA family antigens in gastric adenocarcinoma and carcinoma cell lines in comparison with adjacent normal gastric mucosa. The transcripts of the CEA, NCA and BGP genes evaluated by reverse transcription-polymerase chain reaction were detectable at various levels in all the gastric adenocarcinoma cell lines tested, while CGM2 mRNA was detectable in the cell lines of poorly differentiated but not of well-differentiated carcinomas. The levels of CEA mRNA in normal gastric mucosa were variable but mostly increased in adenocarcinomas. The sparse expression of NCA observed in the normal tissues was markedly up-regulated in the carcinomas. In contrast to previous findings on normal and cancerous colonic tissues, the transcripts of CGM2 were totally undetectable and those of BGP were recognized only marginally, if at all, in normal gastric mucosa, while both messages were detected at significant levels in most of the gastric adenocarcinomas. This was confirmed by in situ hybridization. Our findings indicate that expression of the CEA family antigens, particularly that of BGP and CGM2, is differently regulated in epithelial cells of the colon and the stomach.

Identification of a new isoform of cell-cell adhesion molecule 105 (C-CAM), C-CAM4: a secretory protein with only one Ig domain

A series of Southern blot hybridization experiments using probes derived from different regions of the rat liver cell-cell adhesion molecule 105 (C-CAM) cDNA revealed the presence of a 9.6 kb EcoRI genomic fragment that seemed to encode a unique C-CAM isoform. An RNase protection study showed that this c-CAM transcript was expressed in placenta, spleen, lung and large intestine. In contrast, the other C-CAM isoforms, C-CAM1 and C-CAM2, are expressed in liver and small intestine. This result also suggests that the new isoform, which we named C-CAM4, was indeed encoded by a new C-CAM gene. A rat placenta cDNA library was then screened and the full-length cDNA coding for C-CAM4 was isolated. The deduced protein contained 142 amino acids and had a calculated molecular mass of 15 kDa. C-CAM4 was composed of a leader sequence and the first V-like Ig domain typical of C-CAM-family proteins. However, C-CAM4 lacked the C-like Ig domains, the transmembrane domain, and the cytoplasmic domain found in other C-CAM isoforms. Thus, C-CAM4 is different from the other known C-CAMs in that it is a secreted protein. We have previously shown that the first Ig domain of C-CAM1 is crucial for its adhesion function. The V-like Ig domain of C-CAM4 had 92% and 89% sequence identity with the corresponding regions of C-CAM1 and C-cam2 respectively. Together these results suggest that C-CAM4 may play a role in regulating the function of other C-CAM family proteins.

Lectin histochemistry and carcinoembryonic antigen in spontaneous colonic cancers of cotton-top tamarins (Saguinus oedipus)

The glycoconjugate-binding properties and the expression of carcinoembryonic antigen in colonic cancers of cotton-top tamarins at the German Primate Center are described. Deviating from findings in non-tumorous colonic epithelia of cotton-top tamarins was the presence of UEA-, SBA-, or DBA-binding sites in the infranuclear cytoplasm of colonic epithelial cells, staining of entire cells, and the occurrence of subepithelial extracellular glycoconjugates in and adjacent to colonic cancers. Carcinoembryonic antigen, which normally was limited to the fuzzy coat of the colonic epithelium, was demonstrated in the cytoplasm of the cancer cells.

Immunoelectron microscopic localization of carcinoembryonic antigen in gastric adenocarcinoma cell lines

The distribution of carcinoembryonic antigen (CEA) in human gastric adenocarcinoma cell lines (HPE-GAC-3 cells and HPE-GAC-2 cells) was determined immunohistochemically by indirect peroxidase-labeled antibody method at the light and electron microscopic levels. In GAC-3 cells that proliferated as non-adherent single cells, CEA was located in the perinuclear spaces, the endoplasmic reticulum, Golgi apparatus, vesicles, multivesicular body (MVB) and entire plasma membrane. Membrane CEA was shown to be internalized into MVB in GAC-3 cells. In GAC-2 cells that form an acinus, CEA was predominantly present along the microvilli of the luminal surface and in glycocalyceal bodies, the vesicles which bud from the microvilli into the lumen. These results suggest that in poorly differentiated cancer cells CEA is transported over the entire cell surface, retained on the membrane and accumulated into the cell by way of the MVB, but in well differentiated cancer cells the newly synthesized CEA is rapidly and predominantly transported to the luminal surface and rapidly released from the membrane into the lumen by way of the glycocalyceal body.

Non-proteolytic release of carcinoembryonic antigen from normal human colonic epithelial cells cultured in collagen gel

Recent studies have shown that, even with a minimal content of carcinoembryonic antigen (CEA), normal human colonic epithelial cells express substantial amounts of CEA mRNA and colonic mucosal fragments cultured in vitro produce CEA quite actively, indicating that CEA should no longer be considered to be of an oncofetal nature. To understand the basis of the usefulness of CEA as a tumor marker, we analyzed the release of CEA, a glycosyl-phosphatidylinositol (GPI)-anchored protein, from colonic epithelial cells, by culturing isolated colonic crypts in collagen gel. The crypts appeared to preserve their morphological and biochemical integrity in the gel for at least 16 hr, and released CEA spontaneously. Three forms of CEA--spontaneously released CEA, CEA liberated with phosphatidylinositol-specific phospholipase C (PI-PLC) and CEA in cell lysates--were indistinguishable on SDS-PAGE. This is in contrast to recombinant CEA spontaneously released from CHO transfectants, which showed a smaller molecular mass than that of PI-PLC-cleaved recombinant CEA. By phase separation using Triton X-114, CEA in the cell lysates of crypts was separated mostly into the detergent phase, while the spontaneously released and the PI-PLC-cleaved CEA were separated into the aqueous phase. When the cells were metabolically labeled with the precursors of the GPI-anchor, 3H-ethanolamine but not 3H-palmitic acid was found in the spontaneously released CEA. These findings suggest that, in contrast to the proteolysis-like release of the recombinant CEA from CHO cells, CEA in normal colonic epithelial cells is released by a non-proteolytic cleavage, which probably occurs through the action of some endogenous phospholipase.

Fractionation of carcinoembryonic antigen and related antigens in normal adult feces using a gradient medium Percoll

Fresh normal human feces were fractionated using Percoll gradients and phosphatidylinositol-specific phospholipase C. Studies concerning how cells or cell membrane fragments are fractionated with CEA activity indicate that fecal associated CEA activity is not primarily associated with soluble antigens but with whole cells or fragmented cell membranes.

Production of basic fetoprotein in human peripheral lymphocytes during blastic transformation

To clarify the significance of basic fetoprotein (BFP) in lymphocytes, we investigated whether BFP is produced in lymphocytes during blastic transformation. Peripheral blood lymphocytes obtained from 14 adults were cultured under the stimulation of lectins. The concentration of BFP in the culture medium (extracellular BFP) was estimated serially. The incorporation of [6-3H]-thymidine was assayed simultaneously. The intracellular BFP was measured by dual flow cytometry for DNA and BFP. A lymph node was studied immunohistochemically. Serum BFP was measured in four cases of lymphocytic leukaemia. In two cases, dual staining was performed. The intracellular BFP of the mitogen-stimulated lymphocytes was increased within 24 h. The extracellular BFP was increased exponentially from 72 h. The extracellular BFP at 96 h did not correlate with the [3H]-thymidine incorporation. The intracellular BFP increase began in G1 phase. Immunostaining showed that the B cells also produced BFP. The serum BFP level in leukaemia was high in 1 of 4 cases and the leukaemic cells in two cases showed high intracellular BFP content. These observations indicate that BFP is produced in activated human lymphocytes and in lymphocytic leukaemic cells. The production of BFP during blastic transformation will be a useful new in vitro model for studying the biological role of BFP, and BFP labelling may offer some new possibilities for the study of lymphocytes.

Epitopes predominantly retained on the carcinoembryonic antigen molecules in plasma of patients with malignant tumors but not on those in plasma of normal individuals

We have previously reported that a group of monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA), designated Group F MAbs, are able to discriminate CEA in tumor tissues from normal fecal antigen-2, a soluble form CEA-counterpart in normal adult feces, and that the protein epitopes recognized by them are present on the domain A3-B3 of the CEA molecule. In this study, we further investigated the molecular localization of the epitopes recognized by the Group F MAbs using three new recombinant CEA proteins with restricted domain structures expressed in Chinese hamster ovary cells, and found that the epitopes for the Group F MAbs are present on domain B3 close to the anchoring device of the CEA molecule. The epitopes for the Group F MAbs were retained on the CEA molecules in the plasma of patients with malignant tumors and on the CEA molecules spontaneously released into the culture media from established tumor cell lines. However, a large part of the CEA molecules in the plasma of normal individuals were found to lack the epitopes for the Group F MAbs. These results provide a basis for the improved cancer diagnosis by using our CEA assay system utilizing a Group F MAb, and indicate the potential clinical utility of the Group F MAbs.

Carcinoembryonic antigen levels in peritoneal washings can predict peritoneal recurrence after curative resection of gastric cancer

Carcinoembryonic antigen (CEA) levels were determined in the peritoneal washings from 120 patients with gastric cancer and 9 patients with benign diseases. Elevated values (greater than 100 ng/g of protein) were observed in 20 of 25 patients with gastric cancer with visible dissemination and 16 of 25 patients with serosal invasion but no dissemination. The same elevation was found in only 9 of 70 patients with no serosal invasion and none of the patients with benign disease. The 2-year survival rates after curative operation for the patients with and without elevation of CEA levels were 21% (19 patients) and 100% (66 patients), respectively (P less than 0.001). A negative correlation was found between CEA levels and survival times after noncurative operation. These results indicate that the CEA level in peritoneal washings could be a sensitive detector of invisible peritoneal dissemination and a new predictor for the postoperative prognosis of gastric cancer.

Binding of Escherichia coli and Salmonella strains to members of the carcinoembryonic antigen family: differential binding inhibition by aromatic alpha-glycosides of mannose

Various Escherichia coli and Salmonella strains bound to glycoproteins of the family of carcinoembryonic antigens (CEA). As judged from plateau regions of the binding curves, CEA, nonspecific cross-reacting antigen of Mr 55,000 (NCA-55), and biliary glycoprotein of Mr 85,000 (BGP-85) showed similar binding activities. The binding to ovalbumin was significantly lower and the binding to fetuin was insignificant under identical experimental conditions. The binding of E. coli and S. typhi to the different glycoproteins was similar as judged from the binding curves. In comparison with alpha-methyl-D-mannopyranoside, aromatic alpha-glycosides of mannose were more potent binding inhibitors of E. coli but not of salmonellae to CEA and NCA-55. These results are similar to those previously obtained with intestinal epithelial cells and yeast cells (N. Firon, S. Ashkenazi, D. Mirelman, I. Ofek, and N. Sharon, Infect. Immun. 55:472-476, 1987). The binding of E. coli to CEA was inhibited by purified type 1 fimbriae. On the basis of the distribution of CEA-like glycoproteins in tissues and body fluids, the results indicate that glycoproteins of the CEA family may be involved in the recognition of bacteria and the regulation of bacterial colonization.

Carcinoembryonic antigen gene family: molecular biology and clinical perspectives

The carcinoembryonic antigen (CEA) gene family belongs to the immunoglobulin super-gene family and can be divided into two main subgroups based on sequence comparisons. In humans it is clustered on the long arm of chromosome 19 and consists of approximately 20 genes. The CEA subgroup genes code for CEA and its classical crossreacting antigens, which are mainly membrane-bound, whereas the other subgroup genes encode the pregnancy-specific glycoproteins (PSG), which are secreted. Splice variants of individual genes and differential post-translational modifications of the resulting proteins, e.g., by glycosylation, indicate a high complexity in the number of putative CEA-related molecules. So far, only a limited number of CEA-related antigens in humans have been unequivocally assigned to a specific gene. Rodent CEA-related genes reveal a high sequence divergence and, in part, a completely different domain organization than the human CEA gene family, making it difficult to determine individual gene counterparts. However, rodent CEA-related genes can be assigned to human subgroups based on similarity of expression patterns, which is characteristic for the subgroups. Various functions have been determined for members of the CEA subgroup in vitro, including cell adhesion, bacterial binding, an accessory role for collagen binding or ecto-ATPases activity. Based on all that is known so far on its biology, the clinical outlook for the CEA family has been reassessed.

Cloning of the complete gene for carcinoembryonic antigen: analysis of its promoter indicates a region conveying cell type-specific expression

Carcinoembryonic antigen (CEA) is a widely used tumor marker, especially in the surveillance of colonic cancer patients. Although CEA is also present in some normal tissues, it is apparently expressed at higher levels in tumorous tissues than in corresponding normal tissues. As a first step toward analyzing the regulation of expression of CEA at the transcriptional level, we have isolated and characterized a cosmid clone (cosCEA1), which contains the entire coding region of the CEA gene. A close correlation exists between the exon and deduced immunoglobulin-like domain borders. We have determined a cluster of transcriptional starts for CEA and the closely related nonspecific cross-reacting antigen (NCA) gene and have sequenced their putative promoters. Regions of sequence homology are found as far as approximately 500 nucleotides upstream from the translational starts of these genes, but farther upstream they diverge completely. In both cases we were unable to find classic TATA or CAAT boxes at their expected positions. To characterize the CEA and NCA promoters, we carried out transient transfection assays with promoter-indicator gene constructs in the CEA-producing adenocarcinoma cell line SW403, as well as in nonproducing HeLa cells. A CEA gene promoter construct, containing approximately 400 nucleotides upstream from the translational start, showed nine times higher activity in the SW403 than in the HeLa cell line. This indicates that cis-acting sequences which convey cell type-specific expression of the CEA gene are contained within this region.

Cloning of the complete gene for carcinoembryonic antigen: analysis of its promoter indicates a region conveying cell type-specific expression

Carcinoembryonic antigen (CEA) is a widely used tumor marker, especially in the surveillance of colonic cancer patients. Although CEA is also present in some normal tissues, it is apparently expressed at higher levels in tumorous tissues than in corresponding normal tissues. As a first step toward analyzing the regulation of expression of CEA at the transcriptional level, we have isolated and characterized a cosmid clone (cosCEA1), which contains the entire coding region of the CEA gene. A close correlation exists between the exon and deduced immunoglobulin-like domain borders. We have determined a cluster of transcriptional starts for CEA and the closely related nonspecific cross-reacting antigen (NCA) gene and have sequenced their putative promoters. Regions of sequence homology are found as far as approximately 500 nucleotides upstream from the translational starts of these genes, but farther upstream they diverge completely. In both cases we were unable to find classic TATA or CAAT boxes at their expected positions. To characterize the CEA and NCA promoters, we carried out transient transfection assays with promoter-indicator gene constructs in the CEA-producing adenocarcinoma cell line SW403, as well as in nonproducing HeLa cells. A CEA gene promoter construct, containing approximately 400 nucleotides upstream from the translational start, showed nine times higher activity in the SW403 than in the HeLa cell line. This indicates that cis-acting sequences which convey cell type-specific expression of the CEA gene are contained within this region.

Impaired carcinoembryonic antigen release during the process of suramin-induced differentiation of the human colonic adenocarcinoma cell clone HT29-D4

The establishment of a differentiated state of the human colic adenocarcinoma cell clone HT29-D4 can be obtained by two ways: 1) the removal of glucose and its replacement by galactose in the culture medium (Fantini et al.: Biology of the Cell 65:163-169, 1989); 2) the addition of suramin, a polyanionic compound, in the glucose-containing medium (Fantini et al.: Journal of Biological Chemistry 264:10282-10286, 1989). We investigated the release of CEA in the culture medium of glucose-deprived HT29-D4 cells (HT29-D4-Gal) and studied its alteration in suramin-treated HT29-D4 cells (HT29-D4-S). The amount of CEA released in the medium in function of time in culture of undifferentiated HT29-D4-Glu cells was very low (5 to 8 ng/10(6) cells/24 hours) and almost constant throughout the experiment whereas it increased sharply during differentiation of HT29-D4-Gal cells (380 ng/10(6) cells/24 hours after 9 days in culture). Surprisingly the amount of CEA released by differentiated HT29-D4-S cells remained very low and comparable with the one of HT29-D4-Glu cells. Moreover suramin, when added to CEA-producing HT29-D4-Gal cells, strongly inhibited its release. Radioiodination of cell surface proteins followed by immunoprecipitation using an anti-CEA monoclonal antibody showed the presence of a 180 kDa polypeptide, i.e., CEA, predominantly labeled in HT29-D4-Gal and -S cells. The total CEA cellular content was higher in HT29-D4-Glu and HT29-D4-S cells than in HT29-D4-Gal cells. When HT29-D4-Gal or -S cells were treated with the bacterial phosphatidylinositol phospholipase C (Pl-PLC) a similar level of CEA was released suggesting a similar type of CEA anchorage. The present data demonstrate that a decrease in CEA release (i.e., in HT29-D4-Glu and -S cells) corresponds to an increase in its overall cellular expression. These results are in favour of a regulatory mechanism, impaired by suramin, which determines the balance between the soluble and the membrane bound forms of CEA.

Characterization of carcinoembryonic antigen-related antigens in normal adult feces

About 50-70 mg in total of carcinoembryonic antigen (CEA) (or CEA-related antigens) was detected in normal adult feces evacuated during one day (200-250 g). Ten percent or less of the antigen was found to be in soluble form in fresh feces (naturally solubilized antigen), while 90% or more was still in membrane-bound form which was releasable with phosphatidylinositol-specific phospholipase C (PI-PLC-solubilized antigen). The naturally solubilized and PI-PLC-solubilized antigens are antigenically different from each other and similar to normal fecal antigen (NFA)-2 and CEA, respectively, suggesting that "CEA-distinctive" antigenicity detected so far in CEA from cancerous tissues is not due to the difference between antigens in normal and malignant tissues but is probably due to the presence of the glycosylinositolphosphate moiety at the carboxyl-terminus of the antigen molecule. Thus, "CEA-distinctive" antigenicity is by no means cancer-specific, but this antigenicity seems to be critical for the clinical significance of CEA as a tumor marker, because an assay system (Kit II) which is able to distinguish CEA from NFA-2 revealed much improved features in cancer diagnosis as reported recently.

Escherichia coli of human origin binds to carcinoembryonic antigen (CEA) and non-specific crossreacting antigen (NCA)

Immobilized carcinoembryonic antigen (CEA) and non-specific crossreacting antigen (NCA) bound 3 strains of E. coli of human origin. The binding was dose dependent, saturable, and of high avidity. Binding of the bacteria to CEA and NCA was completely abolished in the presence of 10 mM alpha-methyl D-mannopyranoside. Bacteria did not bind to concanavalin A. In addition, binding to deglycosylated CEA was either absent or significantly reduced. These findings indicate that the E. coli strains bind to D-mannosyl residues in CEA and NCA. Considering the tissue distribution of CEA (brush border of colonic epithelium) and NCA (granulocytes), these glycoproteins may be involved in the recognition of bacteria.

Immunohistochemical demonstration of nonspecific cross-reacting antigen in normal and neoplastic human tissues using a monoclonal antibody. Comparison with carcinoembryonic antigen localization

Nonspecific cross-reacting antigen (NCA) immunoreactivity was localized in normal and neoplastic human tissues using a monoclonal antibody to 55, 90 and 95 kDa molecules of NCA. This was compared to the localization of immunoreactive carcinoembryonic antigen (CEA) as demonstrated by polyclonal and monoclonal antibodies. In frozen sections, CEA was localized in normal surface epithelium of the stomach and colon where NCA was only weakly detected. Type 1 and type 2-like pneumocytes were positive for NCA, while CEA was localized only in type 2-like pneumocytes. CEA and NCA were both demonstrated in ductal cells of frozen pancreatobiliary and mammary tissues. The antigenicity of CEA and NCA in normal tissues was significantly lost after paraffin embedding as compared to frozen sections. NCA was consistently demonstrated in eccrine sweat glands embedded in paraffin. In various tumor tissues, CEA and NCA were colocalized and expression increased sufficiently to be detected in paraffin sections. Adenocarcinomas of the stomach and colon and cystadenocarcinoma of the pancreas, as well as neuroendocrine carcinomas of the lung and thyroid, showed a CEA predominance over NCA. In ductal adenocarcinomas of the pancreas and breast and in cholangiocarcinoma, NCA reactivity was greater than CEA. Keratinizing foci of most squamous cell carcinomas of mucosal origin and some adenocarcinomas equally expressed both. Hepatocellular carcinoma, lobular mammary carcinoma and papillary thyroid carcinoma were positive only with unabsorbed polyclonal antibody which widely recognizes CEA-related substances. Renal cell carcinoma, prostatic adenocarcinoma, transitional cell carcinoma, anaplastic carcinomas, choriocarcinoma and basal cell carcinomas showed little or no immunoreactivity. Hence the relative ratio of CEA/NCA expression in tumors was dependent on the tissue of origin and histologic type. The cytoplasmic granular staining of NCA in cancer cells was a noteworthy difference from the plasma membrane-associated localization of CEA.

Induction of polarized apical expression and vectorial release of carcinoembryonic antigen (CEA) during the process of differentiation of HT29-D4 cells

HT29-D4 clonal cells can be induced to differentiate by a simple alteration of the culture medium, that is, by the replacement of glucose by galactose [Fantini, J., et al. (1986) J. Cell Sci., 83:235-249] as reported for the nonclonal HT29 cells [Pinto, M., (1982) Biol. Cell, 44:193-196]. An essential property of the HT29-D4 cell line is the fact that no cell loss occurs after the medium change, so that the differentiated cells can be considered as the true counterpart of the undifferentiated one. This model is particularly suitable to study morphological and biochemical events associated with the progressive establishment of the differentiation state. We report here that carcinoembryonic antigen (CEA), a 180 kDa glycoprotein originally described as a colon tumor associated antigen, is faintly expressed at the surface of undifferentiated HT29-D4 cells. These cells release a small amount of CEA (2.5 ng/10(6) cells/24 hr) in the culture medium. Fourty-eight hours after glucose substitution by galactose, both CEA cell surface expression and release are strongly enhanced as demonstrated by immunofluorescence and immunoprecipitation studies. Ten days after the medium change, the amount of CEA released reaches a maximum value of 130 ng/10(6) cells/24 hr, which remains stable for differentiated HT29-D4 cells cultured in glucose-free, galactose-containing medium (Gal-medium) for several months. HT29-D4 cells grown in Gal-medium in porous-bottom culture dishes generate leakproof epithelial monolayers. We have successfully performed an independent radioiodination of the apical and basolateral domains of these cells, followed by immunoprecipitation. We demonstrate that CEA is expressed exclusively at the apical surface of differentiated HT29-D4 cells, since the 180 kDa polypeptide was immunoprecipitated only when the radioiodination was performed at the apical side of the monolayer. Leakproof HT29-D4 monolayers cultured in permeable chambers were also used to demonstrate that CEA was exclusively released in the medium bathing the apical side of the cells. In conclusion, this study of cell surface CEA expression and CEA release during the process of differentiation of HT29-D4 cells demonstrated that 1) CEA cell surface expression and CEA release are correlated with cell differentiation; 2) CEA is expressed in the apical brush border membrane of differentiated HT29-D4 cells; and 3) CEA release is exclusively oriented toward the apical side of the polarized monolayer.

cDNA cloning demonstrates the expression of pregnancy-specific glycoprotein genes, a subgroup of the carcinoembryonic antigen gene family, in fetal liver

The pregnancy-specific glycoprotein (PSG) genes constitute a subgroup of the carcinoembryonic antigen (CEA) gene family. Here we report the cloning of four cDNAs coding for different members of the PSG family from a human fetal liver cDNA library. They are derived from three closely related genes (PSG1, PSG4 and PSG6). Two of the cDNA clones represent splice variants of PSG1 (PSG1a, PSG1d) differing in their C-terminal domain and 3'-untranslated regions. All encoded proteins show the same domain arrangement (N-RA1-RA2-RB2-C). Transcripts of the genes PSG1 and PSG4 could be detected in placenta by hybridization with gene-specific oligonucleotides. Expression of cDNA in a mouse and monkey cell line shows that the glycosylated PSG1a protein has a Mr of 65-66 kD and is released from the transfected cells. Sequence comparisons in the C-terminal domain and the 3'-untranslated regions of CEA/PSG-like genes suggests a complex splicing pattern to exist for various gene family members and a common evolutionary origin of these regions.