Faculty Bibliography

Continuous fibroblast growth factor signaling inhibits the differentiation of primary osteoblasts and osteoblastic cell lines. We studied the expression of several cell cycle regulatory molecules in response to fibroblast growth factor, and found that fibroblast growth factor strongly upregulates the expression of p21(WAF1/CIP1), a CDK inhibitor that has also been implicated in the regulation of apoptosis and cell differentiation. To test the hypothesis that p21 mediated the fibroblast growth factor effects on osteoblasts, we studied the differentiation of primary osteoblasts and osteoblastic cell lines derived from p21 null mice in the presence or absence of fibroblast growth factor. While the results obtained indicate that p21 is not the major mediator of the inhibition of osteoblast differentiation by fibroblast growth factor, we found that p21 per se acts as a brake on osteoblast proliferation and differentiation. p21 is strongly downregulated during differentiation and is highly expressed in osteoblastic cell lines expressing activated FGFR2, which do not differentiate. p21 null osteoblasts differentiate faster than wild-type cells, are more susceptible to the differentiation-promoting action of BMP-2, and undergo increased differentiation-related apoptosis. Furthermore, transient overexpression of p21 from an adenovirus vector delayed the onset of differentiation both in wild-type and in p21 null osteoblasts. These results highlight a new function for p21 in osteoblast differentiation

Fibroblast growth factor (FGF) 2 (or basic FGF) is expressed at increased levels in human prostate cancer. FGF2 can promote cell motility and proliferation, increase tumor angiogenesis, and inhibit apoptosis, all of which play an important role in tumor progression. To determine whether FGF2 plays a critical role in prostate cancer progression, we have used the transgenic adenocarcinoma of the mouse prostate (TRAMP) model system. A high percentage of TRAMP mice develop metastatic prostate cancer, and thus the TRAMP model is useful for evaluating cancer progression. TRAMP mice were crossed with FGF2 knockout (FGF2(-/-)) mice, and tumor progression in TRAMP mice that were either hemi- or homozygous for inactivation of the FGF2 allele was compared with progression in wild-type TRAMP mice. Inactivation of even one FGF2 allele resulted in increased survival, a decrease in metastasis, and inhibition of progression to the poorly differentiated phenotype in primary prostatic tumors. When compared with wild-type mice, poorly differentiated tumors arising in FGF(+/-) and FGF(-/-) mice expressed higher levels of vascular endothelial growth factor and, in some cases, increased levels of acidic FGF intracellular binding protein, a nuclear FGF1-binding protein. These findings suggest that both FGF2-mediated angiogenesis and intranuclear FGF2 activities may promote tumor progression and support the hypothesis that FGF2 plays a significant role in prostate cancer progression in vivo

Basic fibroblast growth factor (Fgf2) is required for the generation of founder cells within the dorsal pseudostratified ventricular epithelium, which will generate the cerebral cortex, but the ganglionic eminences are not affected. We report here that the Fgf2 null mutant mice show an approximately 40% decrease in cortical glutamatergic pyramidal neurons. In contrast, no change in pyramidal or granule cell number is detected in the hippocampus of Fgf2 -/- mice. In addition, the soma of the pyramidal cells in the frontal and parietal cortices are smaller in Fgf2 knock-out mice. The decrease in the number and size of glutamatergic neuronal population affects all cortical layers but is restricted to the frontal and parietal cortices without any change in the occipital cortex, indicating that Fgf2 is necessary to regulate cell number and size in the anterior cerebral cortex. In contrast to pyramidal neurons, cortical GABA interneurons are unaffected by the lack of Fgf2. The resulting imbalance between the excitatory and inhibitory neurotransmission in the cerebral cortex is reflected by an increased duration of sleep when the animals receive a GABA receptor agonist. Thus, Fgf2 signaling may contribute to the regional specification of the cerebral cortex and may play a role in increasing the size of anterior cortical regions during vertebrate evolution

The formation of blood capillaries from preexisting vessels (angiogenesis) and vascular remodeling secondary to atherosclerosis or vessel injury are characterized by endothelial cell migration and proliferation. Numerous growth factors control these cell functions. Basic fibroblast growth factor (FGF-2), a potent angiogenesis inducer, stimulates endothelial cell proliferation, migration, and proteinase production in vitro and in vivo. However, mice genetically deficient in FGF-2 have no apparent vascular defects. We have observed that endothelial cell migration in response to mechanical damage in vitro is accompanied by activation of the extracellular signal-regulated kinase (ERK) pathway, which can be blocked by neutralizing anti-FGF-2 antibodies. Endothelial cells from mice that are genetically deficient in FGF-2 neither migrate nor activate ERK in response to mechanical wounding. Addition of exogenous FGF-2 restores a normal cell response, which shows that impaired migration results from the genetic deficiency of this growth factor. Injury-induced ERK activation in endothelial cells occurs only at the edge of the wound. In addition, FGF-2-induced ERK activation mediates endothelial cell migration in response to wounding without a significant effect on proliferation. These data show that FGF-2 is a key regulator of endothelial cell migration during wound repair

Unregulated FGF signaling affects endochondral ossification and long bone growth, causing several genetic forms of human dwarfism. One major mechanism by which FGFs regulate endochondral bone growth is through their inhibitory effect on chondrocyte proliferation. Because mice with targeted mutations of the retinoblastoma (Rb)-related proteins p107 and p130 present severe endochondral bone defects with excessive chondrocyte proliferation, we have investigated the role of the Rb family of cell cycle regulators in the FGF response. Using a chondrocyte cell line, we found that FGF induced a rapid dephosphorylation of all three proteins of the Rb family (pRb, p107, and p130) and a blockade of the cells in the G1 phase of the cell cycle. This cell cycle block was reversed by inactivation of Rb proteins with viral oncoproteins such as polyoma large T (PyLT) antigen and Adenovirus E1A. Expression of a PyLT mutant that efficiently binds pRb, but not p107 and p130, allowed the cells to be growth inhibited by FGF, suggesting that pRb itself is not involved in the FGF response. To investigate more precisely the role of the individual Rb family proteins in FGF-mediated growth inhibition, we used chondrocyte micromass culture of limb bud cells isolated from mice lacking Rb proteins individually or in combination. Although wild-type as well as Rb-/- chondrocytes were similarly growth inhibited by FGF, chondrocytes null for p107 and p130 did not respond to FGF. Furthermore, FGF treatment of metatarsal bone rudiments obtained from p107-/-;p130-/- embryos failed to inhibit proliferation of growth plate chondrocytes, whereas rudiments from p107-null or p130-null embryos showed only a slight inhibition of growth. Our findings indicate that p107 and p130, but not pRb, are critical effectors of FGF-mediated growth inhibition in chondrocytes

Fibroblast growth factors (FGFs) comprise a large family of multifunctional, heparin-binding polypeptides that show diverse patterns of interaction with a family of receptors (FGFR1 to -4) that are subject to alternative splicing. FGFR binding specificity is an essential mechanism in the regulation of FGF signaling and is achieved through primary sequence differences among FGFs and FGFRs and through usage of two alternative exons, IIIc and IIIb, for the second half of immunoglobulin-like domain 3 (D3) in FGFRs. While FGF4 binds and activates the IIIc splice forms of FGFR1 to -3 at comparable levels, it shows little activity towards the IIIb splice forms of FGFR1 to -3 as well as towards FGFR4. To begin to explore the structural determinants for this differential affinity, we determined the crystal structure of FGF4 at a 1.8-A resolution. FGF4 adopts a beta-trefoil fold similar to other FGFs. To identify potential receptor and heparin binding sites in FGF4, a ternary FGF4-FGFR1-heparin model was constructed by superimposing the FGF4 structure onto FGF2 in the FGF2-FGFR1-heparin structure. Mutation of several key residues in FGF4, observed to interact with FGFR1 or with heparin in the model, produced ligands with reduced receptor binding and concomitant low mitogenic potential. Based on the modeling and mutational data, we propose that FGF4, like FGF2, but unlike FGF1, engages the betaC'-betaE loop in D3 and thus can differentiate between the IIIc and IIIb splice isoforms of FGFRs for binding. Moreover, we show that FGF4 needs to interact with both the 2-O- and 6-O-sulfates in heparin to exert its optimal biological activity

Interleukin (IL)-18, a newly discovered cytokine produced primarily by macrophages, has been shown to induce gamma interferon (IFN-gamma) production by natural killer cells, to induce the T helper type 1 response. To further elucidate the role of this cytokine in uncomplicated malaria caused by Plasmodium falciparum, serum levels of IL-18, and gamma interferon (IFN-gamma), determined by an immunoenzymatic assay, were analyzed in 40 adult patients, and in 15 healthy control subjects. A significant increase in serum levels of IL-18 was observed in patients with uncomplicated P. falciparum malaria on admission, whereas serum levels of IFN-gamma tended to increase although not significantly. Serum levels of IL-18 decreased three days later, but still remained significantly high, whereas IFN-gamma levels returned to normal levels compared to the controls. No significant correlation was found between parasitemia and serum levels of IL-18 and IFN-gamma. The increase of IL-18 levels during acute and recovery phases of uncomplicated P. falciparum malaria may reflect a proinflammatory role of IL-18 in these patients. An early and effective immune response regulated by proinflammatory Th1 cytokines, including tumor necrosis factor (TNF), interleukin (IL)-12, and possibly IFN-gamma may limit the progression from uncomplicated malaria to severe and life-threatening complications

A retrospective analysis of data from a cohort of patients coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) who were treated with highly active antiretroviral therapy (HAART) at 3 infectious diseases units in northern Italy was performed. While the patients were receiving HAART, CD4(+) cell counts significantly increased and HIV RNA serum levels decreased. However, no significant overall changes in alanine aminotransferase (ALT) levels and HCV RNA serum levels were observed. Fifteen (4.6%) of 323 patients died within 3 years of follow-up; death was related to cirrhosis in 5 patients (1.6%). No significant difference was observed between cirrhosis-related mortality and mortality related to other causes. Patients with ALT levels >4 times the normal values at initiation of HAART showed a significant decrease in ALT levels, whereas patients with normal ALT levels at initiation of HAART showed a significant increase over time, suggesting that HAART may have long-term beneficial or detrimental effects, depending on patient characteristics