ABSTRACT
BACKGROUND & AIMS: The nonspecific cross-reacting antigen (NCA) is a cell adhesion molecule, and the messenger RNA for NCA is overexpressed in 92% of colorectal carcinomas. The aim of this study was to determine the cis-acting elements that may be responsible for the expression of NCA. METHODS: Deletion mutants of the 5' flanking sequence and first intron were ligated into chloramphenicol acetyltransferase expression vectors, transfected into Chinese hamster ovary (CHO), DiFi, and HT-29 human colorectal carcinoma cells, and BxPC-3 and MDAPanc-28 human pancreatic carcinoma cells. The amount of acetylated chloramphenicol was determined to show the presence and activity of cis-acting sequences. RESULTS: The 5' flanking sequence functions as a promoter in all of cell lines and contains negative regulatory and enhancer sequences. The minimal promoter is active in Chinese hamster ovary and HT-29, though not in MDAPanc-28 cells. The first intron contains a silencer capable of suppressing a heterologous promoter. CONCLUSIONS: The results show cis-acting sequences within and 5' to the NCA gene, which appear to play a role in the expression of this gene in malignant tissues. Some of these sequences function in a cell type-specific manner. Further studies of these elements may provide insight into the mechanisms of the abnormal growth patterns of malignant cells.
Subject(s)
Antigens, Neoplasm/genetics , Cell Adhesion Molecules , Colorectal Neoplasms/genetics , Gene Expression Regulation, Neoplastic , Membrane Glycoproteins/genetics , Animals , Base Sequence , CHO Cells , Cricetinae , HT29 Cells , Humans , Introns , Molecular Sequence Data , Promoter Regions, Genetic , Tumor Cells, CulturedABSTRACT
Single genes with large effects may contribute to insulin resistance or influence susceptibility to non-insulin-dependent diabetes mellitus (NIDDM). In the Pima Indians, results from sib-pair analysis have suggested that a gene on chromosome 4q influences both fasting insulin levels and maximal insulin action. We conducted sib-pair and logarithm of odds (LOD)-score linkage analysis to seek evidence for linkage between genes influencing insulin levels and chromosome 4q loci. Analyses were conducted on nondiabetic individuals from 28 different families participating in the San Antonio Family Diabetes Study. All subjects received a 2-h oral glucose tolerance test. Fasting insulin levels were measured in 382 nondiabetic individuals, and 2-h insulin levels were measured in 366 individuals. Initial sib-pair linkage analysis revealed a possible association between 2-h post-glucose challenge insulin levels and the intestinal fatty acid-binding protein (FABP2) locus located in the region of chromosome 4q28-31 (P = 0.006). Subsequent sib-pair linkage analysis of 11 additional chromosome 4q markers supported this hypothesis. We next conducted segregation analyses to estimate allele frequencies and other model parameters for the putative locus influencing 2-h insulin levels. Results of LOD-score linkage analysis indicated possible linkage between the major gene described by the segregation model and FABP2. Using combined segregation and linkage analysis, we obtained a LOD-score of 2.80 at recombination frequency of 0.0 between FABP2 and the putative locus influencing 2-h insulin levels. The maximum likelihood estimate of the allele associated with low insulin levels was 0.21.(ABSTRACT TRUNCATED AT 250 WORDS)
