Characterization of β-Adrenergic Receptor Linked to Adenylate Cyclase in a Human Cancer Cell Line (COLO 16)

1. A human cancer cell line (COLO 16) derived originally from an epidermal squamous cell carcinoma was found to possess adenylate cyclase responsiveness to β-adrenergic agonists. 2. The adenylate cyclase response was characterized with respect to activation constants (KA) for various β-adrenergic agonists and inhibition constants (Ki) for antagonists. 3. Intact cells responded with dose-dependent increases in production of cyclic adenosine 3′:5′-monophosphate. 4. Properties of the β-adrenergic receptor were evaluated by using the specific binding of [3H]propranolol to cell membranes. Specific binding was saturable, with KD 5.79 nmol/l and binding sites 0.68 pmol/mg of protein. 5. Competition for binding to cell membranes was shown by β-adrenergic agonists and antagonists and was stereospecific. There was close agreement between the affinity of these various agents on adenylate cyclase and receptor binding. 6. It is likely that the β-adrenergic receptor-linked adenylate cyclase in COLO 16 cells represents persistence in a cancer cell line of a receptor present normally in epidermal cells.