PITUITARY ADENYLATE-CYCLASE ACTIVATING PEPTIDE RECEPTORS REGULATE THEGROWTH OF NON-SMALL-CELL LUNG-CANCER CELLS

We have identified pituitary adenylate cyclase activating peptide (PAC AP) receptors on small cell lung cancer cell line NCI-N417 in a previo us study. In this study, the role of PACAP in the growth and signal tr ansduction of non-small cell lung cancer cells was investigated. North ern blot analysis with a full-length human PACAP receptor cDNA probe r evealed a major 7.5-kb hybridizing transcript when total RNA extracted from NCI-H838 cells was used. PACAP bound with high affinity (K-d = 1 nM) to a single class of sites (B-max = 14,000/cell) when NCI-H838 ce lls were used. Specific I-125-labeled PACAP binding was inhibited with high affinity by PACAP-27 and PACAP-38, with moderate affinity by PAC AP(6-38), and with low affinity by vasoactive intestinal polypeptide, PACAP(28-38), and PACAP(16-38). PACAP-27 elevated cAMP in a dose-depen dent manner, and the increase in cAMP caused by PACAP was reversed by PACAP(6-38). PACAP-27, but not vasoactive intestinal polypeptide, elev ated cytosolic Ca2+ in individual NCI-H838 cells, PACAP-27 stimulated arachidonic acid release, and the increase caused by PACAP was reverse d by PACAP(6-38). PACAP-27 stimulated colony formation in NCI-H838 cel ls, whereas the PACAP antagonist PACAP(6-38) reduced colony formation in the absence or presence of exogenous PACAP-27. In nude mice bearing NCI-H838 xenografts, PACAP(6-38) slowed tumor growth significantly. T hese data suggest that biologically active type 1 PACAP receptors are present on human non-small cell lung cancer cells, which exhibit dual signal transduction pathways and regulate cell proliferation.