Tumorigenicity, mucin production and AM-3 epitope expression in clones selected from the HT-29 colon carcinoma cell line.

Two mucin-producing cell clones (16.2 and 12.2) and a mucin-deficient clone (15.2) were selected from the established human adenocarcinoma cell line HT-29 by limiting dilution and Alcian blue staining. The amounts of the mucin antigen detectable on the cell surface with the monoclonal antibody (MAb) AM-3 decreased in the order HT-29 greater than 16.2 greater than 12.2 greater than 15.2 = 0. The binding avidity of AM-3 antibody to cells as well as to mucin extracts from each cell line decreased in the same order, indicating that the epitope density on the cell-bound mucins was highest in HT-29 and lowest in 12.2 cells. The parental line and the mucin-producing cell clones 16.2 and 12.2 showed no contact inhibition and grew as aggregates, while the 15.2 cells were well spread and formed a regular monolayer. The mucin-producing cell lines injected into nude mice yielded solid tumors with different growth rates (HT-29 greater than 16.2 greater than 12.2), while the 15.2 cell clone was not tumorigenic at all. The relative amounts of total mucin-bound hexoses and of the mucin epitope AM-3 decreased in the xenografts in the order HT-29 greater than 16.2 greater than 12.2. The present system is suitable for investigating the role of mucins in growth of colon carcinoma cells and indicates that increased tumorigenicity in nude mice coincides with the increase in total mucin expression and the expression of the AM-3 mucin epitope in tumor tissue.