Serum SP1 and hCG beta-subunit (hCG beta) levels in choriocarcinoma, invasive mole, and hydatidiform mole--clinical significance of SP1/hCG beta ratio

A polymerase-chain-reaction assay for the specific identification of transcripts encoded by individual carcinoembryonic antigen (CEA)-gene-family members

Carcinoembryonic antigen (CEA) is a tumor marker that belongs to a family of closely related molecules with variable expression patterns. We have developed sets of oligonucleotide primers for the specific amplification of transcripts from individual CEA-family members using the reverse transcriptase/polymerase chain reaction (RT/PCR). Specific primer sets were designed for CEA, non-specific cross-reacting antigen (NCA), biliary glycoprotein (BGP), carcinoembryonic antigen gene-family members 1, 6 and 7 (CGM1, CGM6 and CGM7), and one set for all pregnancy-specific glycoprotein (PSG) transcripts. Primers were first tested for their specificity against individual cDNA clones and product-hybridization with internal, transcript-specific oligonucleotides. Total RNA from 12 brain and 63 gynecological tumors were then tested for expression of CEA-related transcripts. None were found in tumors located in the brain, including various mesenchymal and neuro-epithelial tumors. CEA and NCA transcripts were, however, present in an adenocarcinoma located in the nasal sinuses. In ovarian mucinous adenocarcinomas, we always found co-expression of CEA and NCA transcripts, and occasionally BGP mRNA. CEA-related transcripts were also found in some serous, endometrioid and clear-cell ovarian carcinomas. CEA, NCA and BGP transcripts were present in endometrial carcinomas of the uterus and cervical carcinomas, whereas uterine leiomyomas were completely negative. No transcripts were found from CGM1, CGM6, CGM7 or from PSG genes in any of the tumors tested. The PCR data were compared with immunohistochemical investigations of ovarian tumors at the protein level using CEA (26/3/13)-, NCA-50/90 (9A6FR) and NCA-95 (80H3)-specific monoclonal antibodies.

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.

Structure, evolution and chromosomal localization of the human pregnancy-specific beta 1 glycoprotein gene family

Cloning and sequencing of the cDNA of a new member of the PS beta G gene family is reported. Comparison of the sequence with those of other PS beta G cDNAs reveals a remarkable conservation of their sequence (greater than 90%) and of their general structural organization: an NH2 domain is followed by 93- and 85-residue Ig-like domains termed A and B, respectively. Most PS beta G contain two domains A in tandem followed by a single domain B. In some PS beta G members described here, alternative splicing skips the AI domain in some transcripts, yielding two- and three-domain variants, respectively. Individual PS beta G members have specific short carboxyl domains displaying little sequence conservation. The PS beta G family is closely related to the CEA gene family. A detailed comparison of the sequence of both families is given and used to construct an evolutionary tree, using the method of Li, Wu, and Luo (1985, Mol. Biol. Evol. 2: 150-174). Computation of the number of substitutions of synonymous (Ks) and nonsynonymous (Ka) sites and of the Ks/Ka ratio suggests that the PS beta G gene family appeared concomitantly with the expansion of the placental mammals and belongs to the class of rapidly evolving genes. Very little selective pressure has been exerted on the body of the molecules, especially on domain A. The analysis also suggests that PS beta G genes encoding different carboxyl domains would have been positively selected and fixed during the evolution. The PS beta G gene family was assigned to chromosome 19, which also carries the CEA genes.

A pregnancy-specific beta 1-glycoprotein, a CEA gene family member, expressed in a human promyelocytic leukemia cell line, HL-60: structures of protein, mRNA and gene

Both genomic and cDNA clones encoding a precursor for a pregnancy-specific beta 1-glycoprotein (PS beta G) belonging to the CEA family, expressed in a human promyelocytic leukemia cell line, HL-60, have been isolated and the entire primary structure of the precursor is deduced. The 335-AA precursor has a 34-AA signal peptide followed by domains of N, IIA, IIB and C, which are encoded by separate exons. The genomic sequence contains extra exons IA and IB between exons N and IIA. Apparently, exon IA is excluded from the mRNA by alternative splicing while IB is a pseudo-exon having a stop codon formed by a deletion of dinucleotide in the middle of the sequence. This provides another mechanism to render exon IB abortive and is different from that we reported for another PS beta G (Biochem. Biophys. Res. Comm. (1988) 156, 68-77).

The human pregnancy-specific beta 1-glycoprotein (PS beta G) and the carcinoembryonic antigen (CEA)-related proteins are members of the same multigene family

Pregnancy-specific beta 1-glycoprotein (PS beta G), a major product of the placenta with unknown function, consists of a set of glycoproteins synthesized by the syncytiotrophoblast. We report here the molecular cloning of 3 cDNA encoding different members of the PS beta G family. Two clones (C, D) correspond to a single transcript undergoing differential splicing. The third one (E) originates from a different gene. All three clones have identical (C, D) or similar (E) coding sequences except for the last residues at their carboxyl end. They contain 93 residue motifs related to the ancestral Ig-like domain which makes them new members of this gene superfamily. A striking sequence similarity (50 to 60%) is observed between PS beta G and carcinoembryonic antigen (CEA)-related proteins. The evolutionary relationship between CEA and PS beta G points to a possible common function in the control of cell invasion and/or metastasis.

The serum pregnancy-specific beta 1-glycoprotein to beta-human chorionic gonadotrophin ratio as an index of prognosis in patients with choriocarcinoma

The ratio of serum pregnancy-specific beta 1-glycoprotein (SP1) to the beta-subunit of human chorionic gonadotrophin (beta-hCG) before and after chemotherapy was measured in 12 patients with metastatic choriocarcinoma. The ratios before chemotherapy ranged between 0.03 and 0.75, with a mean value of 0.34 (SD 0.21). The ratio increased to over 1.0 (1.05-53.3) after one or two courses of chemotherapy in seven of the 12 patients. These women achieved complete remission. In the other five patients who died of the disease due to drug resistance of the tumour, the ratio after chemotherapy was low (0.04-0.74) and tended to decline. These data suggest that the serum SP1/beta-hCG ratio can be used to predict the prognosis of patients with choriocarcinoma.

In vitro and in vivo studies of the production of placental proteins (HCG, SP1, PPs) in human choriocarcinoma cell lines

The production of human chorionic gonadotropin (hCG), pregnancy-specific beta-1 glycoprotein (SP1), and the various placental tissue proteins (PP4, PP5, PP10, PP11, PP12, MP1) was examined in human choriocarcinoma cell lines using radioimmunoassay (RIA) and an immunoperoxidase (PAP) staining method. In 6 gestational and 2 nongestational choriocarcinoma cell lines, hCG was produced in vitro. A significant heterogeneity of hCG production was noted among the cell lines. Production of hCG in the xenograft tumors was consistent with the hCG production of the same cell lines in vitro. SP1 was demonstrated both in the culture supernatants and the xenograft tumors of 3 cell lines, and the production was found to be inversely correlated with the hCG production of the cell lines. Positive staining for PP4 and MP1, and weakly positive staining for PP5, PP10, and PP12 was found in the xenograft tumors by immunoperoxidase (PAP) stain, but the staining for PP11 was negative. These placental proteins showed positive staining in portions of choriocarcinoma cells. These results indicate that placental proteins are not equally produced in heterogeneous choriocarcinoma cells.