Selective inhibition of PGE2 production in cells transfected with c-fms encoded CSF-1 receptor genes by the tyrosine kinase inhibitor, ST638

In this study, we investigated the effect of ST638, a novel tyrosine kinase inhibitor, on TPA and ionomycin-stimulated PGE2 production after transfection of c-Fms encoded CSF-1 receptor (CSF-1R) DNA (with or without transforming activity) into the myeloid progenitor cell line, 32D. ST638 inhibited prostaglandin E2 (PGE2) production induced after transfection of normal c-Fms into 32D cell line, but failed to inhibit PGE2 production induced in 32D cells transformed with c-Fms containing a point mutation at tyrosine 969 in the intracellular domain (substitution with phenylalanine) and at leucine 301 in the extracellular domain (substitution with serine). The selective effect on PGE2 production in normal c-fms-bearing cells by ST638 may indicate the presence of different induction pathways, one sensitive to ST638 and the Other not. Alternatively, the phosphorylation site at tyr969 in c-Fms may be a site of ST638 action, and upon its removal from the transforming c-Fms, ST638 loses its inhibitory effect.