Isolation of tumor-secreted products from human carcinoma cells maintained in a defined protein-free medium.

A protein-free synthetic cell-growth medium has been defined that permits long-term survival (greater than 120 days) of an established human colon tumor cell line, HT-29. Viability is dependent upon both the concentration of L-glutamine in the medium and the cell density at the time of initial transfer into it. Cell proliferation is minimal, thus obviating the necessity for subculturing. HT-29 adenocarcinoma cells maintained in large-scale culture with this medium continue to secrete the established colon tumor marker carcinoembryonic antigen as well as growth factors and lysozyme. These and, potentially, other important tumor-derived products can therefore be generated continuously in such cultures so that they can be isolated from a conditioned medium free of contaminating serum and protein supplements.