Interstitial lung disease induced by gefitinib and toll-like receptor ligands is mediated by Fra-1.

The role of the AP-1 transcription factor Fra-1 (encoded by Fosl1) in inflammatory responses associated with lung disease is largely unknown. Here, we show that Fra-1 overexpression in mice reduced proinflammatory cytokine production in response to injection of lipopolysaccharide (LPS), a Toll-like receptor (TLR)-ligand. Unexpectedly, Fra-1 transgenic mice died rapidly following LPS treatment, showing severe interstitial lung disease and displaying massive accumulation of macrophages and overproduction of several chemokines, including macrophage chemoattractant protein-1 (MCP-1, encoded by Ccl2). To assess the clinical relevance of Fra-1 in lung pathology, mice were treated with the anticancer drug gefitinib (Iressa), which can lead to interstitial lung disease in patients. Gefitinib-treated mice showed increased Fosl1 and Ccl2 expression and developed interstitial lung disease in response to LPS, endogenous TLR ligands and chemotherapy. Moreover, deletion of Fra-1 or blocking MCP-1 receptor signaling in mice attenuated gefitinib-enhanced lethality in response to LPS. Importantly, human alveolar macrophages showed enhanced LPS-induced FOSL1 and CCL2 expression after gefitinib treatment. These results indicate that Fra-1 is an important mediator of interstitial lung disease following gefitinib treatment.

The role of the transcription factor AP-1 in colitis-associated and beta-catenin-dependent intestinal tumorigenesis in mice.

Chronic inflammation is an important cancer risk factor but the molecular pathways linking inflammation and cancer are incompletely understood. The transcription factor c-Jun/AP-1 (activator protein 1) is involved in inflammatory responses and tumorigenesis and has been proposed as an essential mediator of oncogenic beta-catenin signaling in the intestine. Here, we examined the functions of c-Jun in two distinct mouse models of conditional and intestine-specific activation of beta-catenin. c-Jun is strongly expressed in the small intestine of mutant mice. However, beta-catenin-dependent cell proliferation is surprisingly not affected in mice lacking c-jun in intestinal epithelium, suggesting that c-Jun is not an essential immediate target of beta-catenin signaling in the small intestine. To examine the functions of Jun and Fos proteins during inflammation and cancer in the colon, colitis-associated tumors were induced chemically in the respective knockout mice. Tumors were characterized by activated beta-catenin and strongly expressed c-Jun and JunB. However, tumorigenesis was not affected by inactivation of c-Jun in either intestinal epithelium or myeloid cells. Moreover, tumorigenesis was not altered in mice lacking junB, junD, c-fos, fra-1 or fra-2, suggesting that inhibition of c-Jun or other single AP-1 proteins is not a determining factor in colitis-associated cancer in mice.

Characterization of the human OATP-C (SLC21A6) gene promoter and regulation of liver-specific OATP genes by hepatocyte nuclear factor 1 alpha.

OATP-C (SLC21A6) is the predominant Na(+)-independent uptake system for bile salts and bilirubin of human liver and is expressed exclusively at the basolateral (sinusoidal) hepatocyte membrane. To investigate the basis of liver-specific expression of OATP-C, we studied promoter function in the two hepatocyte-derived cell lines HepG2 and Huh7 and in nonhepatic HeLa cells. OATP-C promoter constructs containing from 66 to 950 nucleotides of 5'-regulatory sequence were active in HepG2 and Huh7 but not HeLa cells, indicating that determinants of hepatocyte-specific expression reside within the minimal promoter. Deoxyribonuclease I footprint analysis revealed a single region that was protected by HepG2 and Huh7 but not HeLa cell nuclear extracts. The liver-enriched transcription factor hepatocyte nuclear factor 1 alpha (HNF1 alpha) was shown by mobility shift assays to bind within this footprint. Coexpression of HNF1 alpha stimulated OATP-C promoter activity 30-fold in HepG2 and 49-fold in HeLa cells. Mutation of the HNF1 site abolished promoter function, indicating that HNF1 alpha is critical for hepatocyte-specific OATP-C gene expression. The human OATP8 (SLC21A8) and mouse Oatp4 (Slc21a6) promoters were also responsive to HNF1 alpha coexpression in HepG2 cells. These data support a role for HNF1 alpha as a global regulator of liver-specific bile salt and organic anion transporter genes.