ABSTRACT
Germline mutations of the APC (adenomatous polyposis coli) gene lead to multiple intestinal tumors in familial adenomatous polyposis patients and in Min (multiple intestinal neoplasia) mice. Consequently, these mice provide an excellent model for familial colon cancer. We have identified an Mr approx. 66 kDa glycoprotein which is preferentially expressed at the cell surface of cell lines established from chemically induced rat colon carcinomas. Cloning of the corresponding Tage4 cDNA has revealed that this protein contains the conserved amino acids characteristic of members of the immunoglobulin gene superfamily. Here, we analyze expression of the mouse Tage4 gene in Min mouse intestinal adenomas. RT-PCR analysis allowed us to detect expression of this gene in all the mouse adenomas tested. In contrast, lower levels of Tage4 mRNA were found in the intestinal tract and barely detectable levels in other tissues of normal mice. Furthermore, Tage4 mRNA was detected in a series of mouse intestinal adenomas by in situ hybridization. A strong signal was seen in the samples analyzed.
Subject(s)
Adenoma/metabolism , Immunoglobulins/biosynthesis , Intestinal Neoplasms/metabolism , Neoplasm Proteins/biosynthesis , Adenoma/chemistry , Adenoma/pathology , Animals , Base Sequence , Female , Gene Expression Regulation, Neoplastic , In Situ Hybridization/methods , Intestinal Mucosa/metabolism , Intestinal Neoplasms/chemistry , Intestinal Neoplasms/pathology , Intestines/anatomy & histology , Intestines/chemistry , Male , Mice , Polymerase Chain Reaction/methods , RNA, Neoplasm/chemistry , RNA-Directed DNA Polymerase/metabolism , Tumor Cells, CulturedSubject(s)
Antigens, Neoplasm/genetics , Cell Adhesion Molecules , Chromosome Mapping , Genes, Immunoglobulin , Multigene Family , Neoplasm Proteins/genetics , Amino Acid Sequence , Animals , Chromosomes, Human, Pair 19 , Colonic Neoplasms/genetics , Consensus Sequence , DNA/isolation & purification , Humans , Molecular Sequence Data , Rats , Sequence Homology, Amino AcidABSTRACT
Defined by monoclonal antibody E4, the pE4 antigen is a 66,000-Da glycoprotein which is expressed at the cell surface of rat colon and mammary carcinomas, but only in trace amounts in normal adult rat tissues. To determine the structure of this tumor-associated antigen and to identify its functional domains, we have cloned a cDNA coding for this protein. It encodes a 416-amino acid protein with an expected molecular weight for the core protein of approximately 42,000. The predicted amino acid sequence reveals that pE4 contains the conserved amino acids and domain structures characteristic of members of the immunoglobulin gene superfamily. Comparison of this sequence with data banks revealed a significant homology with the human and mouse receptors for polio-virus. However, pE4 is not the rat receptor for poliovirus, as different patterns were obtained by hybridization of rat genomic DNA with both probes. A major approximately 2.2-kilobase transcript of the pE4 gene was detected in all the rat tumor cell lines tested. In contrast, barely detectable levels of pE4 mRNA were found in normal adult rat tissues.
Subject(s)
Antigens, Neoplasm/biosynthesis , Colonic Neoplasms/genetics , Colonic Neoplasms/immunology , Genes, Immunoglobulin , Immunoglobulins/genetics , Membrane Proteins , Multigene Family , Amino Acid Sequence , Animals , Antibodies, Monoclonal , Antigens, Neoplasm/genetics , Base Sequence , Blotting, Northern , Blotting, Southern , Cell Line , Conserved Sequence , DNA, Neoplasm/analysis , DNA, Neoplasm/metabolism , Gene Expression , Humans , Molecular Sequence Data , Protein Conformation , RNA, Messenger/analysis , RNA, Messenger/biosynthesis , RNA, Neoplasm/analysis , Rats , Receptors, Virus/genetics , Reference Values , Sequence Homology, Amino Acid , Transcription, Genetic , Tumor Cells, CulturedABSTRACT
In order to define biological markers of aggressiveness, 2 rat colon-carcinoma cell lines differing by their tumorigenicity were used to clone genes over-expressed in colon carcinoma as compared with normal epithelial cells. A progressive rat colon-carcinoma clone (PROb) cDNA library was hybridized with 32P-cDNA synthesized from mRNA prepared from these PROb cells, or from regressive cells (REGb) derived from the same tumor. Several clones were isolated after the initial screening. The specificity of each clone was confirmed by RNA blotting. One of these (B9) was found to hybridize to an mRNA 30-fold more abundant in PROb cells than in normal adult rat colon, and was therefore selected for further study. No gene amplification was detected by Southern blot analysis, indicating that the difference in mRNA content was most likely due to an increased transcription of this gene. Sequencing of the cDNA revealed approximately 98% homology with the rat S13 ribosomal protein. The expression level of this gene was determined in a series of rat cell lines with different growth rates. A good correlation was found between these 2 parameters. Our data suggest that the S13 ribosomal-protein gene can be used to evaluate the growth rate of tumor cells, which might be correlated with their aggressiveness. In an initial trial experiment, S13 ribosomal-protein mRNA was detected in a series of human colorectal tumors by in situ hybridization. A strong signal was seen in the 4 tumors analyzed.
