Macrophage colony-stimulating factor (M-CSF) is a multifunctional cytokine attributed with key biological functions beyond the first discovered role in promoting proliferation of myeloid cell lineage. The human pancreatic cancer cell line MIA PaCa-2, from which the M-CSF gene was originally cloned, was used to study regulation of M-CSF expression. Expression of M-CSF was inducible by interleukin-1α (IL-1α), lipopolysaccharide (LPS) and PMA as demonstrated by a biological activity assay, Northern-blot analysis and reverse transcriptase (RT) PCR. Treatment of the cells with forskolin or dibutyryl-cAMP attenuated the expression of M-CSF induced by IL-1α or LPS, but not by PMA. Electromobility shift assays showed that IL-1α predominantly activated nuclear factor κB (NF-κB), while PMA preferentially activated activator protein-1 (AP-1). The activation of NF-κB, but not AP-1, could be attenuated by cAMP elevation. Relative RT-PCR demonstrated that the expression of a 1.6-kb M-CSF mRNA transcript was more effectively induced by IL-1α than a 4.0-kb transcript. By and large the induced expression of both mRNA transcripts could be attenuated by cAMP. M-CSF promoter-driven luciferase reporter-gene assays revealed that cAMP elevation attenuated the IL-1-induced transcription activation of the M-CSF promoter, but it had no effect on PMA-induced transcription. Our findings suggest that cAMP regulates M-CSF gene expression at the transcriptional level and that its inhibitory effect involves NF-κB signalling pathway.