Cis-acting elements required for expression of the nonspecific cross-reacting antigen gene in colorectal carcinoma.
OBJECTIVE
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.
Jones
D V
DV
Department of Gastrointestinal Medical Oncology and Digestive Diseases, Division of Medicine, University of Texas, Houston, USA.
Wu
E
E
Manire
M
M
Frazier
M L
ML
D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics*; D001483:Base Sequence; D016466:CHO Cells; D015815:Cell Adhesion Molecules; D015179:Colorectal Neoplasms / Q000235:genetics*; D006224:Cricetinae; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D007438:Introns; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D008562:Membrane Glycoproteins