Fibroproliferative processes are a group of disorders in which there is excessive proliferation of spindle (mesenchymal fibroblast-like) cells. They range from hypertrophic scars to neoplasms such as aggressive fibromatosis. Cells from these disorders share cytologic similarity with fibroblasts present during the proliferative phase of wound healing, suggesting that they represent a prolonged wounding response. A critical role for ␤-catenin in mesenchymal cells in fibroproliferative processes is suggested by its high rate of somatic mutation in aggressive fibromatosis. Using a Tcf-reporter mouse we found that ␤-catenin protein level and Tcf-transcriptional activity are elevated in fibroblasts during the proliferative phase of healing. We generated a transgenic mouse in which stabilized ␤-catenin is expressed in mesenchymal cells under control of a tetracycline-regulated promoter. Fibroblasts from the transgenic mice exhibited increased proliferation, motility, and invasiveness when expressing stabilized ␤-catenin and induced tumors after induction of the transgene when grafted into nude mice. Mice developed aggressive fibromatoses and hyperplastic gastrointestinal polyps after 3 months of transgene induction and healed with hyperplastic cutaneous wounds compared with control mice, which demonstrates an important function for ␤-catenin in mesenchymal cells and shows a central role for ␤-catenin in wound healing and fibroproliferative disorders.

Suppressor of fused (Su(fu)) is a negative regulator of the Hedgehog signaling pathway that controls the nuclear-cytoplasmic distribution of Gli/Ci transcription factors through direct protein-protein interactions. We show here that Su(fu) is present in a complex with the oncogenic transcriptional activator ␤-catenin and functions as a negative regulator of T-cell factor (Tcf)-dependent transcription. Overexpression of Su(fu) in SW480 (APC mut ) colon cancer cells in which ␤-catenin protein is stabilized leads to a reduction in nuclear ␤-catenin levels and in Tcf-dependent transcription. This effect of Su(fu) overexpression can be blocked by treatment of these cells with leptomycin B, a specific inhibitor of CRM1-mediated nuclear export. Overexpression of Su(fu) suppresses growth of SW480 (APC mut ) tumor cells in nude mice. These observations indicate that Su(fu) negatively regulates ␤-catenin signaling and that CRM-1-mediated nuclear export plays a role in this regulation. Our results also suggest that Su(fu) acts as a tumor suppressor.The oncogenic transcriptional activator ␤-catenin is a major mediator in Wnt signaling (1-4). A large multiprotein complex that includes APC 1 and axin normally facilitates the phosphorylation of ␤-catenin by GSK3␤. Phosphorylated ␤-catenin binds to the F-box protein ␤TrCP and is then modified by ubiquitination and subjected to proteasome-mediated protein degradation. When cells are exposed to the Wnt signal, ␤-catenin phosphorylation and its subsequent ubiquitination are blocked. ␤-Catenin is thus diverted from the proteasome; instead, ␤-catenin accumulates and translocates to the nucleus, where it interacts with members of the Tcf/Lef family of transcription factors and activates transcription of Wnt-responsive genes. In tumors, ␤-catenin degradation is blocked by mutations of APC, axin, or ␤-catenin itself. As a result, stabilized ␤-catenin enters the nucleus and ␤-catenin⅐Tcf complexes activate oncogenic target genes.Nuclear translocation of ␤-catenin is of key importance in its ability to regulate transcription, yet little is known about the factors important in controlling the nuclear versus cytoplasmic distribution of ␤-catenin. ␤-Catenin lacks a nuclear import signal, and it docks to the nuclear membrane by a mechanism that is Ran-independent and does not require importins (5). Nuclear import of ␤-catenin is also independent of its association with the Tcf transcription factors because mutant forms of ␤-catenin that do not bind Tcf proteins can enter the nucleus (6). Microinjection studies show that ␤-catenin rapidly exits the nucleus, suggesting a role for nuclear export in the regulation of the intracellular distribution of ␤-catenin (7).Several studies demonstrate that APC is a nucleo-cytoplasmic protein with export from the nucleus inhibited by LMB, a specific inhibitor of CRM1-mediated nuclear export (8 -10). CRM1, also called exportin-1, is an export karypopherin that binds to a leucine-rich nuclear export signal on its target protein and mediates nuclear-cytoplasm...

In viral myocarditis, inflammation and destruction of cardiac myocytes leads to fibrosis, causing progressive impairment in cardiac function. Here we show the etiologic importance of serine elastase activity in the pathophysiology of acute viral myocarditis and the therapeutic efficacy of an elastase inhibitor. In DBA/2 mice inoculated with the encephalomyocarditis virus, a more than 150% increase in myocardial serine elastase activity is observed. This is suppressed by a selective serine elastase inhibitor, ZD0892, which is biologically effective after oral administration. Mice treated with this compound had little evidence of microvascular constriction and obstruction associated with myocarditis-induced ischemia reperfusion injury, much less inflammation and necrosis, only mild fibrosis and myocardial collagen deposition, and normal ventricular function, compared with the infected nontreated group.

Serine elastases degrade elastin, stimulate vascular smooth muscle cell migration and proliferation, and are associated with myocardial damage. To evaluate the impact of elastase inhibition on cardiovascular development and disease, transgenic mice were created in which the mouse preproendothelin-1 promoter was used to target elafin overexpression to the cardiovascular system. To distinguish the transgene from endogenous elafin, constructs were made incorporating a FLAG sequence; the COOH-terminus FLAG-tagged elafin construct produced a stable, functionally active gene product and was used to create transgenic mice. Consistent with endothelin expression, abundant elafin mRNA was observed in transgenic F1 embryos (embryonic day 13.5) and in adult transgenic mice heart, trachea, aorta, kidney, lung, and skin, but not in liver, spleen, and intestine. Functional activity of the transgene was confirmed by heightened myocardial elastase inhibitory activity. No tissue abnormalities were detected by light microscopy or elastin content. However, injection of 10 plaque-forming units (PFU) of encephalomyocarditis virus resulted in death within 11 days in 10 out of 12 nontransgenic mice compared with one out of nine transgenic littermates. This reduced mortality was associated with better cardiac function and less myocardial inflammatory damage. Thus, elafin expression may confer a protective advantage in myocarditis and other inflammatory diseases.