Detection of mRNAs of Carcinoembryonic Antigen and Nonspecific Cross‐reacting Antigen Genes in Colorectal Adenomas and Carcinomas by in situ Hybridization

Expression of mRNAs of carcinoembryonic antigen (CEA) and nonspecific cross‐reacting antigen (NCA) genes in colorectal carcinomas and adenomas was investigated by in situ hybridization (ISH) with specific biotinylated probes. Hybridization was clearly detected throughout the cytoplasm of 7 out of 15 adenomas and 13 out of 15 carcinomas with the CEA cDNA probe, and in 6 out of 15 adenomas and 10 out of 15 carcinomas with the NCA cDNA probe. The intensity of signal appeared to be stronger in carcinomas than that in adenomas, and the CEA and NCA mRNAs were expressed together in most of the positive tissue specimens. On the other hand, noninvaded tissues adjacent to the carcinoma did not show any signal except for 4 cases faintly stained with the NCA probe. This finding was partly confirmed by Northern blot analysis which indicated that the specific bands for the CEA and NCA mRNAs were more intense in RNAs from carcinoma tissues than in those from adjacent noninvaded tissues. These data suggest that the ISH technique with biotinylated probes could be of use for analyzing expression and localization of CEA and related genes on tissue sections.