Heterogeneity in the Induction and Expression of Carcinoembryonic Antigen-related Antigens in Human Colon Cancer Cell Lines

Sodium butyrate induces morphological and biochemical changes consistent with a more differentiated phenotype in some colon cancer cell lines. These changes include increased expression of carcinoembryonic antigen (CEA) and other oncodevelopmental markers. We utilized domain-specific probes and polyclonal antibodies against CEA-related antigens to study sodium butyrate-induced expression of the CEA gene family in a villous adenoma-derived cell line, which is nontumorigenic in nude mice (VACO 235), and two colonic carcinoma cell lines known to respond to sodium butyrate exposure by phenotypic differentiation (HT-29 and LS 174T). The induction begins as quickly as 24 h after exposure and occurs primarily at a transcriptional level, although some translational control is also evident. No evidence was found for gene amplification, rearrangement, or methylation to account for the mechanism of this transcriptional control. [35S]Cysteine pulse-labeled cell lysate immunoblots and polyadenylated RNA blot hybridization suggest that increases in mRNA transcript and CEA-related glycoprotein levels are primarily due to increased synthesis rather than decreased degradation. A considerable amount of heterogeneity is seen in the biosynthesis of the CEA-related glycoproteins, with each cell line showing a distinct pattern of CEA-related antigen expression from a limited number of mRNA transcripts.