The subunit structure of non-specific cross-reacting antigen (NCA)

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.

Effective purification of nonspecific cross-reacting antigens with phosphatidylinositol-specific phospholipase C

Two molecular species of nonspecific cross-reacting antigens, NCA-90 and NCA-50 with mol. wts. of 90,000 and 50,000, respectively, were effectively extracted with phosphatidylinositol-specific phospholipase C (PI-PLC) from human lung tissues, followed by extraction with perchloric acid, immunoaffinity chromatography with anti-NCA adsorbent, and gel filtration on a TSK G3000SW column. The yields of NCA were about 2 times more than those obtained by the usual method without PI-PLC. Addition of 0.05 unit of PI-PLC to 1 g of lung tissue and incubation at 37 degrees C for 1 h with continuous shaking seem to be practically sufficient for NCA extraction. The immunochemical properties of the NCAs thus obtained were found to be identical to those of NCAs obtained by the ordinary method.

Behavior in immunoblotting of dimeric and monomeric forms of nonspecific cross-reacting antigen (NCA-50) from normal lung

The dimeric and monomeric forms of NCA-50 from normal lung showed differences in binding to nitrocellulose in an immunoblotting procedure. The NCA dimer showed weaker binding, it passed through nitrocellulose and was more easily washed out from the blot. The NCA monomer was bound strongly and was detected with higher sensitivity following immunoblotting.

Carcinoembryonic antigen: function in metastasis by human colorectal carcinoma

Carcinoembryonic antigen (CEA) is a glycoprotein that has been useful as a tumor marker to predict recurrence in gastrointestinal malignancies, but whose biological function has not been elucidated. With the recent evidence that CEA is a member of the immunoglobulin supergene family, CEA may be involved in intercellular recognition and binding. This review examines the role that CEA plays in the development of metastases by colorectal carcinoma.

Expression of nonspecific cross-reacting antigen species in myeloid leukemic patients and healthy subjects

The reactivity of two monoclonal antibodies recognizing NCA-95 and NCA-55 (MAb 47 and MAb 192, respectively) with a polyclonal anti-NCA serum in myeloid leukemic cells isolated by density gradient centrifugation was compared using an immunofluorescence test (IF). It was observed that the blood myeloid cells in 78.8% of the patients with different types of myelocytic leukemias and all granulocytes of 15 normal donors showed similar expression of the NCA species studied. The leukocytes of the remaining patients did not synthesize the NCA-95 species regardless of the maturation stage of the cells studied. In two patients, synthesis of this NCA form was limited to the fractions containing myelocytes and metamyelocytes. We have found that all anti-NCA antibodies studied recognized different antigenic epitopes in a myeloid cell series. A relationship between the patient's survival and the proportion of NCA-containing cells was also observed.

The molecular heterogeneity of nonspecific cross-reacting antigen synthesized by tumor cells and granulocytes

The molecular heterogeneity of nonspecific cross-reacting antigen (NCA) was examined. Metabolically-labeled glycoproteins were precipitated from cell lysates of human tumor cell lines and of normal peripheral granulocytes with antibodies specific for NCA, and analyzed by SDS-PAGE. NCA components synthesized by three tumor cell lines, QGP-1 (pancreas), HLC-1 (lung) and CAOV-2 (ovary) showed slightly different migration patterns on SDS-PAGE, but the molecular weights of their unglycosylated peptides synthesized in the presence of tunicamycin were all found to be 35K. On the other hand, two molecular species of NCA were identified in normal granulocytes: an 80K mature form derived from a 69K precursor peptide and a 58K mature form from a 41K precursor peptide. Upon SDS-PAGE, the migration pattern of the unglycosylated NCA peptides from tumor cells was affected by the presence of 2-mercaptoethanol, while that of the peptides of granulocytes was not. All the NCAs identified in this study possessed antigenic determinants common to carcinoembryonic antigen as well as those unique to NCA. These results suggest that the molecular heterogeneity of NCA observed thus far resulted from diverse glycosylation of the three fundamental molecular forms of unglycosylated peptides: one with a molecular weight of 35K produced by tumor cells and two with molecular weights of 69K and 41K produced by granulocytes.

Monoclonal antibody against carcinoembryonic antigen (CEA) identifies two new forms of crossreacting antigens of molecular weight 90,000 and 160,000 in normal granulocytes

Two new forms of non-specific crossreacting antigens (NCAs) were identified in the Nonidet P40 (NP-40) extracts of normal granulocytes by precipitation with the monoclonal antibody (MAb) 192 directed against carcinoembryonic antigen (CEA) and already known to crossreact with the perchloric acid soluble NCA-55. The NP-40 soluble NCAs recognized by MAb 192 have apparent mol. wts of 90,000 and 160,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Both NCAs appear to consist of a single monomeric polypeptide chain, since they have the same electrophoretic mobility in SDS-PAGE under reduced and non-reduced conditions. When granulocytes were extracted with perchloric acid instead of NP-40, only the 55,000 mol. wt antigen, corresponding to the previously described NCA-55, was precipitated by MAb 192. Furthermore, it was shown that NCA-55 is not a degradation product of NCA-90 or NCA-160 due to the perchloric acid treatment because exposure to perchloric acid of NCA preparations purified from NP-40 extracts did not change their apparent mol. wts in SDS-PAGE. It was also shown that NCA-160 is not a granulocytic form of CEA because it was not precipitated by the MAb 35 reacting exclusively with CEA. Immunocytochemical studies of granulocytes and macrophages showed that MAb 192 stained both types of cells whereas MAb 47 stained only the granulocytes and MAb 35 none of these cells. In granulocytes both MAbs reacted with antigens associated with granules and also present at the periphery of the nucleus as well as in the Golgi apparatus. The NCA-90 identified by MAb 192 was found by sequential immunodepletion to be antigenically distinct from the NCA-95 precipitated by MAb 47. The epitope recognized by MAb 192 on CEA and NCA molecules appears to be on the peptidic moiety because the antigens deglycosylated by the enzyme Endo F were still precipitated by this MAb. Taken together, the results indicate that MAb 192 identifies two novel forms of NCA (NCA-90 and NCA-160) in NP-40 extracts of granulocytes, which are distinct from CEA and the previously described NCA-55 and NCA-95 identified by MAbs 192 and 47, respectively, in perchloric acid extracts of granulocytes.

Non-specific cross-reacting antigen (NCA) in individual maturation stages of myelocytic cell series

The distribution and localization of NCA and carcinoembryonic antigen CEA in cells of different types of myelogenous leukaemias (acute myelogenous leukaemia - AML; chronic granulocytic leukaemia - CGL; CGL in myeloblastic crisis - CGL-BC) was studied using the immunofluorescence test. Discontinuous density-gradient centrifugation was used to separate myeloid cells into fractions containing granulocytes in individual stages of maturation. Serum NCA and CEA levels were estimated in parallel. It was established that: (a) AML blasts without maturation (MO type) and monoblasts did not synthesize NCA; (b) individual blasts of AML with features of maturation (M1, M2 types) and some myeloblasts of CGL-BC exhibited a limited ability to express cytoplasmic NCA; (c) the number of NCA-containing cells increased in the more mature granulocyte fractions isolated on Ficoll-Hypaque density-gradients; (d) myelocytic NCA is immunologically related to NCA isolated from lung tissue and (e) CEA is undetectable in the myelocytic cell series.

Tumor-Associated Antigens in Female Genital Tract Cancers

The immunologic reactivity of glycoprotein antigens extractable from individual, histologically different ovarian and uterine cancers was studied taking into account their relationship with carcinoembryonic antigen (CEA), nonspecific cross-reacting antigen (NCA), α-fetoprotein (AFP), and α-1-antichymotrypsin. All studies were performed using specific immune sera against perchloric acid (PCA) extracts of ovarian mucinous cystadenocarcinoma (anti-PCA-CaOm) and cervical squamous cell carcinoma (anti-PCA-CaCx), and antisera against the reference antigens mentioned above. A considerable antigenic heterogeneity and the existence of several immunologically related antigenic systems were found: 1) CEA-like antigens; 2) NCA-type antigens; 3) an antigen different from CEA and NCA present in ovarian mucinous adenocarcinomas and often cross-reacting, but not identical with respective antigens of uterine body and cervical carcinomas; 4) an antigen reacting with anti-α-1-antichymotrypsin serum; and 5) an antigen reacting with anti-AFP serum.

Immunochemical identification of an alpha 1-acid glycoprotein-antigenic determinant on carcinoembryonic antigen (CEA) and non-specific cross-reacting antigen (NCA)

An immunochemical characterization of carcinoembryonic antigen (CEA) and NCA (non-specific cross-reacting antigen) was performed. Positive reactions of CEA and NCA (Mr 60 000) with some antibodies to alpha 1-acid glycoprotein (AG) were observed. Thus, both antigens may contain immune determinants in common with alpha 1-acid glycoprotein. CEA showed positive reactivity with anti-NCA. NCA showed positive reactivity with either polyclonal or monoclonal antibodies to CEA, but negative reactivity with auto-antibodies to CEA. 125I-Tetracosapeptide (synthetic peptide-24 corresponding to the amino terminal sequence of CEA) failed to react with any antisera against CEA, NCA and AG. 125I-AG also showed no immuno-reaction with any antibody against CEA, NCA and tetracosapeptide. These results suggest that some monoclonal antibodies to CEA are directed against a common antigenic determinant of both CEA and NCA in addition to AG and tetracosapeptide, and that the auto-antibody to CEA is directed against a unique immune determinant which is not common to NCA. Thus, CEA appears to contain a unique determinant not found in NCA. Similarities in the composition of both amino acids and carbohydrates of CEA and NCA suggest that CEA is 'big-big' AG and NCA is 'big' AG.