The Epidermal Growth Factor-Like Growth Factor Amphiregulin Is Strongly Induced by the Adenosine 3′,5′-Monophosphate Pathway in Various Cell Types
We examined the cAMP-mediated regulation of the EGF-like growth factor amphiregulin (AR) in T cells and observed a strong cAMP-induced up-regulation of AR mRNA in a time-and concentration-dependent manner independent of T cell activation. This regulation may in part be mediated through activation of a cAMP-responsive element (CRE) in the AR promoter, since the CRE conferred cAMP-responsiveness to a luciferase reporter in Jurkat TAg cells. Similar effects of AR mRNA induction were seen in T
... were seen in T cells treated with cAMP-elevating agents such as PGE 2 and forskolin as well as with the phosphodiesterase inhibitors rolipram and IBMX. Furthermore, the induction of AR mRNA by cAMP was strongly suppressed by a PKA type I-selective inhibitor, whereas treatment with an Epac-specific agonist did not increase AR levels. In addition, an increase in AR gene transcripts by cAMP was also seen in MCF-7 mammary carcinoma cells and H295R adrenal cells. Moreover, the potent cAMP-mediated induction of AR mRNA resulted in increased secretion (5-fold) of AR from T cells. Furthermore, supernatants from cAMP-stimulated T cells containing secreted AR induced phosphorylated MAPK in OVCAR-3 carcinoma cells. In conclusion, our data suggest that AR is under strong regulation by the cAMP pathway in various cell types, and that PGE 2 -and cAMP-induced AR secretion from T cells may be highly relevant in a microenvironment consisting of tumor cells and infiltrated immune cells, since AR by activating the MAPK pathway through a paracrine route may contribute to proliferation of tumor cells and thus further add to neoplastic processes.