The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) modulate several biochemical pathways in human leukemic myeloid cells.

The neuropeptides Vasoactive-intestinal peptide (VIP) and Pituitary adenylate-cyclase activating protein (PACAP) increased cAMP levels in three out of five human myeloid leukemic cell lines tested while an increased in calcium intracytoplasmic levels was seen only in one cell line (HEL). This increase was phospholipase C, Pertussis toxin dependent and associated with an increase in c-fos and c-jun protein expression together with the formation of functional AP-1 transcriptional factor complex. Cell exposure to VIP or PACAP resulted in a decrease in HEL cell proliferation associated with a down-regulation of the erythroid marker, Glycophorin A.