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Transforming growth factor β2 (TGFβ2) is highly expressed in a variety of different cancer cell lines. Using Z12 cells, a mutant of 293 cells with overexpression of TGFβ2, we found that the cyclic adenosine monophosphate (cAMP)-responsive element (CRE) sequence in the promoter of the TGFβ2gene is crucial for its increased expression. Further, constitutive phosphorylation of CRE-binding protein (CREB) is increased in these cells. Treating Z12 cells with either the PI3 kinase inhibitor LY294002 or the p38 MAPK inhibitor SB203580 significantly inhibited both the phosphorylation of CREB and expression of TGFβ2. In addition, treating Z12 or cancer cell lines with either of these 2 inhibitors significantly decreased their secretion of TGFβ2. These data suggest that activated PI3 kinase and p38 MAPK play important roles in high expression of TGFβ2 in cancer cells by stimulating the phosphorylation of CREB, which activates the CRE in the promoter of the TGFβ2gene. We have identified an important link between PI3 kinase, p38 MAPK, and TGFβ2, providing an additional rationale for using inhibitors of these kinases as therapeutic drugs in cancer. [ABSTRACT FROM AUTHOR]

Activation of chemokine genes in response to interferon (IFN)-γ or NF-κB is an important aspect of inflammation. Using the chemokine gene ip-10in mouse embryonic fibroblast cells as an example, we show that the response to IFN-γ is long lasting but secondary: initial STAT1 activation drives IRF1 synthesis, and IRF1 then binds to IFN-stimulated regulatory elements (ISREs) in the ip-10promoter. The promoters of most IKK-β-dependent IFN-stimulated genes (ISGs) also contain ISREs. In response to IFN-γ, inhibitor of NF-κB (IκB) kinase β (IKK-β) is required to activate both newly synthesized IRF1 and the p65 subunit of NF-κB, which contributes to ip-10expression by binding to κB sites in the ip-10promoter, with little or no activation of classical NF-κB. In contrast to IFN-γ, IL-1β induces ip-10expression rapidly but transiently, by activating classical NF-κB and increasing the synthesis of IRF1. Together, IL-1β and IFN-γ induce ip-10synergistically. IFN-γ does not affect the transient activation of classical NF-κB by IL-1β and synergistic induction of ip-10expression by IFN-γ and IL-1β occurs even after the activation of classical NF-κB has returned to basal levels. Therefore, IKK-β has a novel role in IFN-γ-dependent activation of chemokine gene expression through its activation of IRF1 and p65. [ABSTRACT FROM AUTHOR]

Activation of NF-κB requires the inhibitor of κB (IκB) kinase (IKK) complex, which is made up of two functional kinases, IKKαand IKKβ, and the scaffolding protein IKKγ. We recently identified several interferon-γ(IFN-γ)-stimulated genes (ISGs) that are not induced in mouse embryonic fibroblast cells (MEFs) doubly null for the expression of IKKαand IKKβ. We show here that the IFN-γ-induced transcription of IKK-dependent ISGs requires IKKβbut not IKKα. We also identify several additional IKKβ-dependent ISGs that are induced by IFN-γboth in MEFs and in RAW 264.7 macrophages. Many have a combination of κB and IFN-stimulated response elements (ISRE) in their promoters. Although the IFN-γ-induced expression of the IKKβ-dependent gene ip-10is sensitive to the superrepressor (SR) of IκBαand requires the p65 subunit of NF-κB, IFN-γdoes not activate NF-κB. In summary, a distinct subset of IFN-γ-dependent genes requires some components of the normal pathway of NF-κB activation without activation of NF-κB signaling by IFN-γ. [ABSTRACT FROM AUTHOR]