Autologous cancer vaccine: a novel formulation

A novel cancer vaccine consisting of fixed autologous cancer tissue-fragments, microparticles encapsulating cytokines, and an adjuvant was developed. In a Phase I/IIa clinical trial, vaccination to patients after resection of hepatocellular carcinoma induced significantly longer time before the first recurrence than that in historical control patients operated in the same department (P < 0.05). This formulation will be promising against recurrence of many types of human cancers.

Homophilic adhesion of human CEACAM1 involves N-terminal domain interactions: structural analysis of the binding site

CEACAM1 on leukocytic, endothelial, and epithelial cells functions in homophilic adhesion, tumor suppression, regulating cell adhesion and proliferation, and in heterophilic adhesion as a receptor for E-selectin and Neisseria meningiditis, Neisseria gonorrhoeae, Haemophilus influenzae, and murine coronaviruses. The 8 transmembrane isoforms of human CEACAM1 possess an extracellular N-terminal IgV domain, followed by variable numbers of IgC2 domains. To establish which key amino acids contribute specifically to CEACAM1 homophilic adhesion, exposed amino acids in the N-terminal domain of a soluble form of CEACAM1 were subjected to mutagenesis. Analyses of mutant proteins with conformationally dependent antibodies indicated that most mutations did not substantially affect the structural integrity of CEACAM1. Nevertheless, decreased adhesion was observed for the single mutants V39A or D40A (single-letter amino acid codes) in the CC' loop and for the triple mutants located in the GFCC'C" face of the N-terminal domain. Interestingly, whereas single mutations in R64 or D82 that are predicted to form a salt bridge between the base of the D and F beta strands close to the critical V39 and D40 residues also abolish adhesion, an amino acid swap (R64D and D82R), which maintains the salt bridge was without significant effect. These studies indicate that the CC' loop plays a crucial role in the homophilic adhesion of CEACAM1. They further predict that specific hydrophobic amino acid residues on the nonglycosylated GFCC'C" face of CEACAM1 N-terminal domain are not only involved in heterophilic interactions with Opa proteins and H influenzae, but are also critical for protein-protein interactions between 2 CEACAM1 molecules on opposing cells.

Biochemical characterization of 25 distinct carcinoembryonic antigen (CEA) epitopes recognized by 57 monoclonal antibodies and categorized into seven groups in terms of domain structure of the CEA molecule

The chemical nature of 25 distinct carcinoembryonic antigen (CEA) epitopes, which were recognized by 57 different monoclonal antibodies and categorized into 7 groups (Groups A to G) in terms of domain structure of the CEA molecule, was analyzed and the findings obtained were compared with the results of our previous studies using recombinant CEA proteins. All 21 epitopes of Groups A to F defined by 48 MAbs were resistant to periodate oxidation and were to a greater or lesser extent retained after deglycosylation of CEA, indicating that they are all protein in nature. The 21 epitopes were detected in recombinant CEA proteins expressed in Chinese hamster ovary (CHO) cells. Seven of the 21 epitopes of protein nature were partially or completely sensitive to reduction and alkylation of CEA and not detected or only slightly revealed in the recombinant CEA proteins expressed in E. coli, indicating that those epitopes are dependent on the tertiary structure of the peptide chain, which is formed by disulfide bonds. All 4 epitopes of Group G defined by 9 MAbs were sensitive to mild periodate oxidation and deglycosylation, but resistant to reduction and alkylation and to digestion with pepsin or pronase, indicating that those 4 epitopes are carbohydrate in nature. Although none of the 4 epitopes of Group G were detected in the recombinant CEA proteins expressed in E. coli, two were detected in those expressed in CHO cells. The biochemical studies reported here thus provide information as to the nature of the epitopes on the CEA molecule and help form the basis for selecting the anti-CEA MAbs for use in biological study and potential clinical applications of CEA.

Characterization of murine carcinoembryonic antigen gene family members

The carcinoembryonic antigen (CEA) is a human tumor marker whose gene belongs to a family with more than 20 members. This gene family codes for a group of proteins with in vitro cell adhesion properties and for a group of abundantly expressed pregnancy-specific glycoproteins (PSG) with unknown functions. As a basis for in vivo functional studies, we have started to analyze the murine CEA gene family and have identified five new members (Cea-2 to Cea-6). cDNA clones were isolated for Cea-2, Cea-3, and Cea-6. The deduced amino acid sequences of Cea-2 and Cea-6 indicate three IgV-like (N), followed by one IgC-like (A) domain (N1-N2-N3-A). We have also partially characterized the Cea-2 gene and two additional ones, Cea-4 and Cea-5. Cea-2 and Cea-4 are separated by only 16 kb, suggesting a close linkage of murine CEA-related genes, as found for the human CEA gene family. Cea-5 was located to the proximal region of mouse Chromosome (Chr) 7, which is syntenic to part of human Chr 19, containing the human CEA gene family cluster. Cea-2, Cea-3, and a Cea-4-like gene are differentially transcribed in the placenta during pregnancy, but not in other organs tested. This expression pattern strongly suggests that they represent counterparts of the human PSG subgroup members, despite the presence of multiple IgV-like domains, a feature not found for human PSGs. The more distantly related Cea-5 seems to be ubiquitously expressed. The putative promoter region of Cea-2 lacks typical TATA- or CAAT-boxes, but contains other conserved motifs that could play a role in the initiation of transcription.

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.