Activation protein 1 (AP-1) has been reported to be an activator ofIl12b transcription in LPS-stimulated macrophages32, whereas in tumor-derived prostaglandin E2 (PGE2)-treated macrophages, it appears to play the opposite role: inhibitingIl12b transcription and promoting tumor progressionin vivo33. This evidence concerns the gene FOS and neoplasm.