Human Breast Cancer Cells Characteristics of Vasoactive Intestinal Peptide Receptors in Pharmacology, Molecular Identification and Functional

High-performance liquid chromatography-purified I2*l-vasoactive in testinal peptide (VIP) bound to T-47D human breast cancer cells in a specific, saturable, and reversible manner. Scatchard plots were compat ible with the presence of one class of VIP receptors with high affinity (*„= 4.5 x HT10 M VIP, and Bm* = 293 fmol/mg protein). The neuropeptide and its natural analogues inhibited the binding of ''"I-VIP and stimulated cyclic AMP (cAMP) generation in T-47D cells 96-fold (EC»= 7 x IO"10M VIP), in the following order of potency: VIP > helodermin > human peptide with A-icniiiiiul histidine and <'-torminal methionine > human pancreatic growth hormone-releasing factor > human secretin. In contrast, I29I-VIP binding was not displaced by pancreatic glucagon, human oxyntomodulin, truncated glucagon-Iike peptide-1, glucagon-like peptide-2, the somatostatin analogue SMS 201-995, gastric inhibitory peptide, and a series of steroid hormones or peptides unrelated to VIP. VIP also increased cAMP generation in seven other human breast cancer cell lines: 114-66B. HSL 53, HSL 78, MCF 7, MDA-MB231, T-47D2, and ZR75-1. Adenylate cyclase activity rose from 72.2 ±14 to 1069 ±66 pmol cAMP/min mg protein after the addition of Kl" M VIP to I -471) plasma membranes. In agreement with our pharmacological results and the Scatchard analysis of the binding data, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized receptor in the I -471) membranes permitted identification of one autoradiographic band with a molecular weight of 69,000. The sensitivity of the M, 69,000 binding site to GTP and low doses of VIP implies that in I -471) cells, this component constitutes the membrane domain involved in the functional regulation of adenylate cyclase by VIP receptors. Our results indicate a role for the VIP receptor-cAMP system in human breast cancer cells.