The murine SerpinB2 proximal promoter region between nucleotides -539 and +92 mediated both PMA- and LPS-inducible gene transcription, with induction by PMA being less intense and more transient than that by LPS. Inspection of the murine SerpinB2 proximal promoter sequence shows that a CRE and two AP-1-like elements, demonstrated to mediate PMA-stimulated transcription of the human SERPINB2 gene [37], also are present in the murine SerpinB2 proximal promoter between nucleotides −189 and −87. These sites may therefore also play a role in mediating PMA-inducible transcription of the murine SerpinB2 gene. In contrast to the pattern of incremental increases in PMA-induced transcriptional activity conferred by regions of the murine SerpinB2 promoter containing these sites, most of the LPS-inducible response is dependent upon cis-acting regulatory sequences in the region between nucleotides −189 and −539. LPS responsiveness absolutely required the C/EBP binding site located in the region between nucleotides −189 and −539, with the downstream CRE and AP-1-like elements also being critical. Of note, there are previous reports of combinatorial interactions between C/EBP-β and CRE binding proteins (CREB) and AP-1 [63], and C/EBP-β has been reported to physically interact with AP-1, and NF-κB to promote gene expression of inflammatory mediators [63]; [66]. Additionally, CREB has been shown to control transcription of the C/EBP-β gene [67].