Differences in expression of SPan-1 and CA15-3 antigens in blood and tissues.

Pancreatic and mammary cancer cells are reported to have different oligosaccharides on the same apomucin, the MUCI gene product. A better understanding of the tissue specificity of these sugar structures may help in identifying the source of mucins when they are found in the sera. Serum levels of 3 pancreatic-cancer-associated carbohydrate epitopes identified by monoclonal antibodies (MAbs) SPan-1, 19-9 and DU-PAN-2, were compared to those of CA15-3 in a variety of malignant conditions. CA15-3 identifies both carbohydrate and peptide determinants associated with the MUC1 apomucin in breast tissues. SPan-1 antigen was elevated in a high percentage of patients with pancreatic, gastric and colorectal cancer but in only a few of the patients with malignancies of non-GI origin such as breast, ovary and lung. The 19-9 and DU-PAN-2 antigens had a similar pattern of much greater sensitivity for pancreatic cancer than for these non-gastrointestinal cancers. The levels of these 3 markers showed significant correlations in pancreatic cancer. In contrast, CA15-3 was elevated in a large number of patients with breast, lung, ovarian and pancreatic cancers. There was no correlation of CA15-3 with the 3 other markers in pancreatic cancer. SPan-1 and DF3/115D8 antigens in blood have different mobilities in SDS-PAGE and buoyant densities. Moreover, SPan-1 and DF3 antigenic determinants are localized in different regions of the same normal and malignant pancreas and breast tissues. Thus the SPan-1 determinant can be dissociated from the breast peptide and/or carbohydrate determinants.

Expression of carcinoembryonic antigen and related genes in lung and gastrointestinal cancers.

Carcinoembryonic antigen (CEA), a tumor marker for lung cancers of small cell (SCLC) and non-small cell (NSCLC) types, belongs in a multigene family which includes non-specific cross-reacting antigen (NCA) and biliary glycoprotein 1 (BGP). We used specific cDNA probes and a CEA immunoassay to determine the pattern of expression in normal and malignant lung and gastrointestinal (GI) tissues. Normal lung contained high amounts of NCA and a low concentration of CEA. All 3 genes were expressed discordantly in lung tumors and cell lines. In contrast, all three genes were expressed in most G1 tumor cell lines. In both lung and colorectal cell lines expression of NCA RNA was relatively high, while BGP RNA was relatively low, and the median concentrations of CEA were greater than in corresponding non-malignant tissues. While CEA protein concentrations in lung cell lines were similar to those present in G1 cell lines, the ratio of NCA:CEA RNA was significantly higher in lung cancer lines than in colorectal lines. Thus, NCA constitutes most of the "CEA-like" immunoreactivity previously described in lung cancers. There was excellent concordance between expression of CEA RNA and CEA protein, as well as between concentrations of CEA protein in cell line pellets and supernatant fluids. Of interest, significantly higher rates of CEA expression were present in lung cancers expressing neuroendocrine (NE) markers. The association between CEA expression and NE cell properties is intriguing and may prove to be of clinical interest.

Identification and characterization of new antigenic fragments related to carcinoembryonic antigen in adult feces.

Antigens in human adult feces related to carcinoembryonic antigen (CEA) were analyzed with respect to their molecular masses, CEA domain compositions, and N-terminal amino acid sequences. By avoiding perchloric acid treatment, new fecal antigens related to CEA were identified. The fecal antigens revealed by Western blot were M(r) 78,000, 70,000, 60,000, 50,000, 44,000, 36,000, 33,000, and 25,000 and a species M(r) less than or equal to 14,000. Unlike native CEA, all of the fecal antigens were very poorly soluble in perchloric acid and did not bind to concanavalin A, suggesting that they had undergone significant deglycosylation in the digestive tract. The major fecal antigens were purified by immunoaffinity chromatography and their N-terminal amino acid sequences determined. FA78, FA60, FA33, and the M(r) less than or equal to 14,000 antigen had the N-terminal amino acid sequence of the CEA N-domain, and FA44 and FA25, the sequence of the CEA A2 domain. The CEA domain compositions of the fecal antigens were investigated by probing them with anti-CEA monoclonal antibodies of known domain specificities. The N-terminal amino acid sequences, immunoreactivities with anti-CEA monoclonal antibodies, and apparent molecular masses of the fecal antigens allowed the following domain assignments (based on CEA as N-A1B1-A2B2-A3B3): FA78, N-A1B1-A2B2-A3B3; FA60, N-A1B1-A2B2; FA44, A2B2-A3B3; FA33, N-A1B1; and FA25, A2B2. The M(r) less than or equal to 14,000 antigen was shown to be the N-domain of CEA or nonspecific cross-reacting antigen. FA36 was assigned the N-AB domain structure of nonspecific cross-reacting antigen. The results suggested that FA78, FA60, FA44, FA33, and FA25 were degradation products (including deglycosylation and proteolysis) of CEA and that FA36 was a degradation product of nonspecific cross-reacting antigen.

Preparation of synthetic polypeptide domains of carcinoembryonic antigen and their use in epitope mapping.

Genes encoding the four principal polypeptide domains (N, A1-B1, A2-B2, and A3-B3) of carcinoembryonic antigen (CEA) were synthesized and expressed in Escherichia coli as fusion products with bacterial CMP-KDO synthetase (CKS). The four synthetic fusion proteins were purified in high yield and used as targets in Western blots for 11 anti-CEA MAbs and to compete with immobilized CEA for binding to four of these MAbs. Each of the MAbs showed strong binding to one or more of the fusion proteins. In Western blots, MAbs H19C91 and 4230 bound only to CKS-N. MAbs H8C2 and H11C35 bound only CKS-A1-B1, and MAbs T84.66, H46C136, and H21C83 appeared to be specific for CKS-A3-B3. None of the MAbs tested bound only to CKS-A2-B2. However, two MAbs bound both CKS-A1-B1 and CKS-A3-B3 and one MAb (3519) bound to all three of the repeated domains. Since these three domains exhibit over 90% amino acid sequence homology, the latter results were not surprising. The competition studies largely confirmed the results of Western blots but did show some MAb-fusion protein interactions not observed in Western blots. These competition studies also allowed estimation of the relative affinities of the MAbs for the synthetic domains and for native CEA. These studies demonstrated that epitopes in CEA recognized by the MAbs in this study are peptide in nature and that the fusion proteins are of utility in the localization of the epitopes on the polypeptide chain of CEA.

Characteristics of cell lines established from human gastric carcinoma.

We report the establishment and characterization of four continuous cell lines derived from human primary and metastatic gastric carcinomas, and we compare their properties with a panel of colorectal carcinoma cell lines previously established and reported by us. Our success rate in culturing gastric carcinomas was relatively low, especially from primary tumors, compared to colorectal carcinoma. These observations may reflect the relatively modest number of gastric carcinoma cell lines established (mainly from Japan), compared to the abundance of colorectal carcinoma lines established worldwide. All four gastric lines expressed the surface glycoproteins carcinoembryonic antigen and TAG-72 and three lines expressed CA 19-9. Two of the lines expressed aromatic amino acid decarboxylase but lacked other markers for neuroendocrine differentiation. All four lines were positive for vasoactive intestinal peptide receptors but lacked gastrin receptors. In addition, two lines expressed receptors for muscarinic/cholinergic receptors but not beta-adrenergic receptors. Cytogenetic evidence for gene amplification was present in the cell lines. All four lines contained varying numbers of double-minute chromosomes. One line, SNU-16, was amplified for the c-myc proto-oncogene and contained four homogeneously staining regions. While c-myc and c-erb-B-2 RNA were expressed by all lines, there was no evidence of amplification or overexpression of several other proto-oncogenes and growth factors. The multiple properties we have described in our gastric carcinoma cell lines are remarkably similar to those found in the panel of colorectal carcinoma cell lines. These properties include morphology, growth characteristics, expression of surface glycoproteins, partial expression of neuroendocrine cell markers, frequent chromosomal evidence of gene amplification, and occasional amplification of the c-myc proto-oncogene. Our four well characterized cell lines should provide useful additions to the modest number currently available for in vitro studies of gastric carcinoma.

Mucin glycoproteins as tumor markers.

Extensive biochemical studies have shown that mucin tumor antigens have a range of molecular sizes from 200 to greater than 1000 kDa. The molecular size of mucin antigens can be dramatically affected by the source and method of purification. Mucin antigens vary from 24 to 80% in carbohydrate content and their density is usually greater than 1.40 g/ml. Galactose and N-acetyl glucosamine are the predominant sugar residues in many mucins, whereas mannose is usually present in low levels or absent. The amino acids serine, threonine, alanine, glycine, and proline are abundant in mucins. An O-glycosidic linkage between the carbohydrate and protein of mucins is the most common linkage encountered. The gene encoding the core peptide for at least one mucin tumor marker, HMFG, has been identified, sequenced, and expressed. These findings may lead to a better understanding of the multiepitope nature of mucin tumor markers. The advent of hybridoma technology has yielded several monoclonal antibodies that have been used to identify the presence of tumor-associated mucins in the sera of cancer patients. Elevated levels of mucin antigens have been found in the serum of most patients with advanced adenocarcinomas. Many studies have shown that tumor-associated markers are useful in monitoring patients following cancer treatment. Clinically useful immunoassays have been developed for monitoring patients with ovarian, breast, and pancreatic adenocarcinomas. Although individual mucin tumor markers show limited utility in detecting early adenocarcinoma, recent studies using multiple mucin markers have suggested that early detection, at sensitivities greater than 50%, can be achieved.

Evaluation of factors affecting the performance of enzymatic SPan-1 immunoassays for pancreatic cancer.

An avidin-biotin complex (ABC) sandwich enzymatic immunoassay was developed utilizing SPan-1, a murine monoclonal antibody of the IgM isotype. Biotin was attached to the epsilon-amino group of lysines of SPan-1 using biotin-N-hydroxysuccinimide esters with or without a spacer (aminohexane). Addition of biotin to carbohydrates was with biotin hydrazide after periodate oxidation of the immunoglobulin. The resultant assays were compared to a sandwich radioimmunoassay and to another form of the SPan-1 enzymatic immunoassay in which oxidized horseradish peroxidase had been directly conjugated to SPan-1. Comparable antigen detection limits were obtained regardless of whether biotin was added to the peptide or carbohydrates or whether a spacer was used or not. The ABC assay had approximately the same SPan-1 antigen detection limit as the radioimmunoassay. 90.6% of the human pancreatic cancer sera tested positive in the ABC assay as compared to a previously reported 93% positive rate with a radioimmunoassay.

Characteristics of cell lines established from human colorectal carcinoma.

We have characterized 14 human colorectal carcinoma cell lines established from primary and metastatic sites by us during the years 1982 to 1985. Five lines were established in fully defined ACL-4 medium and 9 in serum supplemented R10 medium. However, after establishment, cultures could be grown interchangeably in either medium. The lines grew as floating cell aggregates in ACL-4 medium, while most demonstrated substrate adherence in R10 medium. The lines had relatively long doubling times and low cloning efficiencies. Twelve were tumorigenic in athymic nude mice when injected s.c., and two grew i.p. as well. Based on culture, xenograft, and ultrastructural morphologies, the 14 lines could be subtyped as follows: 4 were well differentiated; 5 were moderately differentiated; 4 were poorly differentiated; and 1 was a mucinous carcinoma. Membrane associated antigens characteristic for gastrointestinal cells (carcinoembryonic antigen, CA 19-9, and TAG-72 antigens) were expressed by 50-71% of the lines. Lines expressing carcinoembryonic antigen and CA 19-9 actively secreted these antigens into the supernatant fluids while TAG-72 antigen was not secreted. Surprisingly, 5 of 7 of the original tumor samples tested and 13 of 14 cultured lines expressed L-dopa decarboxylase activity, which is a characteristic enzyme marker of neuroendocrine cells and tumors. In addition, one poorly differentiated cell line contained dense core granules, characteristic of endocrine secretion. Preliminary cytogenetic analyses indicated that 9 of 11 lines examined contained double minute chromosomes. In addition, 3 of the 9 lines with double minutes also had homogeneously staining regions. These findings indicate a high incidence of amplification of one or more as yet unidentified genes.

Factors influencing pyrroline 5-carboxylate synthesis from glutamate by rat intestinal mucosa mitochondria.

Factors influencing pyrroline 5-carboxylate (P5C) synthesis from glutamate by a subcellular fraction enriched in mitochondria of rat small intestinal mucosa have been studied. P5C synthesis decreased rapidly if this subcellular fraction was preincubated at 20 degrees C in the absence of substrates; this effect suggests that the enzyme(s) catalyzing P5C synthesis from glutamate (P5C synthase) is unstable in the absence of substrates. In the presence of substrates P5C synthesis increased linearly for the first 30 min of incubation, suggesting that the substrates promote enzyme stability. Pyridoxal 5'-phosphate is an effective inhibitor of P5C synthase whereas pyridoxamine 5'-phosphate and pyridoxal are not inhibitory. Potassium phosphate, KCl, and KBr each inhibited P5C synthase but potassium-Hepes (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) did not. Potassium phosphate was the most potent inhibitor followed by KBr, and then KCl. These results suggest P5C synthase is sensitive to anion inhibition. Both L-ornithine and D-ornithine inhibited P5C synthase; L-proline did not inhibit. Several analogs of ornithine and proline were also tested and none was found to inhibit P5C synthase; the inhibition by ornithine is, therefore, rather specific and it may prove to contribute to the regulation of metabolism of these amino acids.

Pyrroline-5-carboxylate synthesis from glutamate by rat intestinal mucosa. Subcellular localization and temperature stability.

The demonstration of the ornithine biosynthesis from glutamate in cell-free homogenates of rat intestinal mucosa by Ross, G., Dunn, D., and Jones, M.E. (1978) Biochem. Biophys. Res. Commun. 85, 140-147 suggested that this tissue might have the capacity to convert glutamate to pyrroline-5-carboxylate (P5C). We have shown in the preceding paper (Wakabayashi, Y., and Jones, M.E. (1983) J. Biol. Chem. 258, 3865-3872) that this is the case. The intracellular distribution of the P5C-synthesizing activity was investigated utilizing a newly developed procedure for subcellular fractionation of the rat intestinal mucosa. We found that the activity resided in the mitochondrial fraction as characterized by marker enzymes and an electron micrograph. The mitochondrial membrane fraction, freed of the soluble matrix and intermembrane space enzymes, retained all of the P5C-synthesizing activity. Addition of the soluble fraction to the membrane fraction did not affect the activity. P5C synthase, the name we have chosen for the protein(s) that catalyzes P5C synthesis from glutamate when ATP and NADPH are present, is susceptible to thermal inactivation in the presence of detergent. By lowering the incubation temperature to or below 20 degrees C, one can obtain a linear production of P5C with respect to time and protein concentration. Lower incubation temperatures are recommended for routine assay of this enzyme(s). Addition of 30% glycerol to the incubation mixture resulted in a linear formation of P5C with time at 30 degrees C; this and other data suggest that polyhydroxylic compounds may protect this protein against denaturation. Preliminary experiments suggest that P5C synthase can be extracted from a mitochondrial membrane in the presence of detergent, a high salt concentration, and glycerol. The possibility that the enzyme(s) is located in the inner mitochondrial membrane is discussed.

Resolution of rat mitochondrial matrix proteins by two-dimensional polyacrylamide gel electrophoresis.

The mitochondrial matrix subfractions from rat liver, kidney cortex, brain, heart, and skeletal muscle were isolated and their protein components were resolved by two-dimensional polyacrylamide gel electrophoresis, revealing between 120 and 150 components for each matrix subfraction. Excellent resolution was obtained utilizing a pH 5 to 8 gradient in the first dimension and in 8 to 13% exponential acrylamide gradient in the second dimension, increasing the number of mitochondrial matrix proteins observed 3-fold over one-dimensional systems. Protein components tentatively identified by co-migration with pure enzymes and by known tissue distributions are carbamoyl-phosphate synthetase (EC 2.7.2.5), ornithine transcarbamylase (EC 2.1.3.3), glutamate dehydrogenase (EC 1.4.1.3), pyruvate carboxylase (EC 6.4.1.1), citrate synthase (EC 4.1.3.7), fumarase (EC 4.2.1.2), aconitase (EC 4.2.1.3), alpha-ketoglutarate dehydrogenase (EC 1.2.4.2), dihydrolipoyl transsuccinylase (EC 2.3.1.12), lipoamide dehydrogenase (EC 1.6.4.3), glutamate-aspartate aminotransferase (EC 2.6.1.1), and the two subunits of pyruvate dehydrogenase (EC 1.2.4.1). Protein components unambiguously identified by peptide mapping are citrate synthase, aconitase, and pyruvate carboxylase. The inner membrane subfraction from rat liver mitochondria was also resolved two dimensionally; the alpha and beta subunits of ATPase (F1) (EC 3.6.1.3) were identified by peptide mapping.