Cell-specific expression of tissue factor (TF) in vivo is consistent with its primary role in hemostasis. In addition, TF expression is induced in cultured cells by a variety of agents, including serum and growth factors, which define the TF gene as a "primary response" gene. In this study we examined the signaling pathways and cis-acting regulatory elements required for induction of TF gene expression in HeLa cells in response to serum and the tumor promoter, phorbol 12-myristate 13-acetate (PMA). TF activity and mRNA were induced greater than sixfold in quiescent HeLa cells by serum and PMA. TF mRNA induction by both agonists required intracellular Ca2+ mobilization, whereas inhibition of protein kinase C abolished induction of the TF gene by PMA but had no effect on induction by serum. Functional studies demonstrated that a region of the human TF promoter between -96 and +121 bp contained regulatory elements required for serum and PMA induction. These data indicate that different signaling pathways regulate TF gene expression in response to serum and PMA, although the same cis-acting DNA elements may mediate induction.