Seven tissue-specific isozymes--lactate dehydrogenases A and B (LDHA and LDHB), esterases B2 and A4 (ESB2 and ESA4), creatine kinase B (CKB), and red blood cell and tissue forms of adenosine deaminases (ADA)--were examined in the human adenocarcinoma cell line LS174T and its subclones grown under a wide variety of conditions. Strong expressions of ESB2, ESA4 and CKB were stable in all material studied, as was a greater expression of LDHA than of LDHB. ADA isozyme expression varied with culture conditions. Identical expression of the five stable isozymes was observed in six surgical specimens of normal bowel mucosa, while cell lines derived from normal mucosa varied in the expression of these isozymes. An additional 23 colorectal cell lines, derived from primary or metastatic adenocarcinomas in different stages of invasiveness and differentiation from 18 individuals, were verified as to their origin by genetic signature analysis and similarly studied for isozyme expression. These lines had different, yet stable, gene expression patterns similar to differences observed among six adenocarcinoma surgical specimens. These differences could not be related to the number of passages that the cell lines were in culture nor to the stages of the tumors at the time that the cell lines were initiated or surgical samples tested. Gene expression patterns in adenocarcinomas differed, these differences might have been due to the origin of colorectal adenocarcinomas from different cell types within a heterogeneous mucosa, and the colorectal cell lines studied represented appropriate models for colon cancer.