The glycine box: a determinant of specificity for fibroblast growth factor

Acidic fibroblast growth factor (FGF-1), keratinocyte growth factor (FGF-7), and FGF-10 are homologues with distinct specificity. In the presence of heparin, FGF-1 binds and activates in vitro all FGFR subtypes, while FGF-7 exhibits absolute specificity for the IIIb splice variant of FGFR2. FGF-10 exhibits a similar specificity but also binds the FGFR1IIIb isoform. Neither FGF-7 nor FGF-10 will bind to IIIc isoforms of FGFR. Molecular models of FGF, heparin, and the FGFR ectodomain suggested that sequences between beta-strands 10 and 12 of FGF may be important for the interaction of FGF with the heparin-FGFR ectodomain duplex. Site-directed mutants of FGF-7 and FGF-10 were prepared to test whether this domain might underlie failure of FGF-7 and FGF-10 to bind to the FGFRIIIc isoforms. Constructions with substitution of FGF-1 sequences spanning the entire C-terminus encoded in exon 3 or only C-terminal sequences spanning beta-strands 10 through 12 conferred ability on FGF-7 to bind to and activate FGFRIIIc without a significant loss in binding to or activation of FGFR2IIIb. A series of twelve different substitutions of shorter segments of FGF-1 sequences into the C-terminal portion of FGF-7 or FGF-10 revealed that substitution of GSCKRG for GIPVRG or the tri-peptide sequence KKN for NQK just N-terminal to it conferred dual activities on both the FGF-7 and FGF-10 backbones. The results suggest that the combined sequence domain, which we call the FGF glycine box (G-box), is a major determinant for the specificity of the binding of FGF to heparan sulfate-FGFR duplexes.

Traumatic carotid cavernous sinus fistula: serial angiographic studies from the day of trauma

BACKGROUND AND PURPOSE

The purpose of this study was to ascertain the early angiographic features characteristic of traumatic carotid cavernous sinus fistulas (CCFs).

METHODS

Eight patients with severe craniofacial injuries underwent emergency diagnostic and therapeutic angiography for intractable oronasal bleeding, starting on an average of 6.7 hours after trauma. Carotid angiograms and the clinical manifestation of traumatic CCFs were then reviewed retrospectively to determine characteristic angiographic features.

RESULTS

In four of the eight patients, no arteriovenous fistulas were found in the cavernous sinuses and symptomatic CCF did not occur during the follow-up period. In the remaining four patients, dural CCFs (Barrow type B) were observed, unilaterally in three patients and bilaterally in one. One of these four patients subsequently became symptomatic and required transarterial coil embolization.

CONCLUSION

Traumatic dural CCFs are frequently observed in the early stage of severe craniofacial trauma, if investigated. Although their spontaneous disappearance is known, some of these do become symptomatic and need treatment.

[A case of Salmonella subdural empyema developed in chronic subdural hematoma]

A case of Salmonella subdural empyema developed in chronic subdural hematoma (Infected Subdural Hematoma; ISH) was reported. A 64-year-old man had been in a nearby hospital due to myelodysplastic syndrome with cerebral infarction for two months. His condition there had been almost uneventful. But spike fever occurred and the patient became drowsy two days before his transfer to our medical center. His consciousness level deteriorated progressively and CT scan showed a right chronic subdural hematoma. He had had no history of head trauma in the previous two months. On admission to our center, his consciousness level was semicoma with anisocoria. An emergency operation was performed via a single burr hole initially. From the burr hole, old bloody fluid accompanied by yellowish pus was obtained. Thus so-called ISH was diagnosed and the craniotomy was carried out. Gram stain of the specimen revealed gram negative rods. Although an epileptic state developed after the operation, it was controlled by barbiturate coma therapy for 3 days, followed by phenytoin administration. Fever subsided gradually with antibiotics sensitive to the bacteria and his anisocoria disappeared on the 4th postoperative day. In this case, Salmonella enteritidis was detected from bacterial culture both of the specimen and of the arterial blood. Salmonella enteritidis might have been implanted on the capsule of the chronic subdural hematoma by bacteremia derived from immunological dysfunction due to myelodysplastic syndrome. In conclusion, the possibility of ISH should be considered in chronic subdural hematoma patients with immunological dysfunction.

Inhibition of growth of malignant rat prostate tumor cells by restoration of fibroblast growth factor receptor 2

A loss of expression of fibroblast growth factor (FGF) receptor 2 IIIb (FGFR2IIIb), which responds to stroma-derived FGF, accompanies progression of premalignant androgen-responsive rat prostate tumor epithelial cells to the malignant phenotype. Concurrently, the level of FGFR2 gene expression is reduced and lost altogether in over 30% of cells, whereas all malignant cells abnormally express FGFR1, which is normally confined to stromal cells (S. Feng et al., Cancer Res., 57:5369-5378, 1997). To determine the relative roles of the FGFR2 and FGFR1 kinases in growth of malignant cells, we transfected malignant prostate epithelial cells with the wild-type FGFR2IIIb kinase and an artificial chimeric construct (FGFR2IIIb/R1) composed of the FGFR2IIIb ectodomain and the FGFR1 kinase domain. Population growth kinetics, in both the absence and presence of FGF-7, which binds only the FGFR2IIIb ectodomain, were then examined in the transfected cell populations. In contrast to the untransfected malignant tumor cells and those expressing the FGFR2IIIb/R1 chimera, FGF-7 caused a dose-dependent net inhibition of the population growth rates of cells expressing the full-length FGFR2IIIb kinase. The results suggest that although the FGFR2 kinase can mediate positive mitogenic effects, it mediates a net restriction on the growth of prostate tumor epithelial cells relative to FGFR1. Highly malignant prostate tumor cells, which have lost the FGFR2 tyrosine kinase, retain the cellular response mechanisms to it. Restoration of the FGFR2 kinase to malignant tumors that are refractory to treatment may present a new avenue for gene therapy.

Differential expression of transforming growth factor-beta and its receptors in hepatocytes and nonparenchymal cells of rat liver after CCl4 administration

BACKGROUND/AIMS

Transforming growth factor-beta (TGF-beta) is a family of multifunctional proteins that regulate hepatocyte proliferation, and biosynthesis of the extracellular matrix. In this study we examined whether modulation of TGF-beta receptor expression contributes to the liver diseases.

METHODS

The mRNA expression of TGF-beta1, TGF-beta type I receptor (TGFbetaRI), TGF-beta type II receptor (TGFbetaRII) and TGF-beta type III receptor (TGFbetaRIII) in rat livers injured by CCl4 administration was studied by Northern blotting. The mRNA expression patterns were confirmed by in situ hybridization.

RESULT

The peak of TGF-beta1 mRNA expression was observed 48 h after acute intoxication with CCl4 in nonparenchymal cells. However, the levels of TGFbetaRI and TGFbetaRII mRNA expression decreased from 24 h to 48 h and from 12 h to 48 h, respectively, and returned to the normal level by 72 h. TGFbetaRII mRNA expression was depressed more and for longer than that of TGFbetaRI mRNA. Analysis in separated hepatocytes and nonparenchymal cells from the injured livers indicated that the mRNA changes occurred in hepatocytes. Nonparenchymal cells expressed TGFbetaRI and TGFbetaRII mRNAs at constant levels during liver regeneration. TGFbetaRIII mRNA, which also decreased after 12 h, was not apparent in hepatocytes but only in nonparenchymal cells.

CONCLUSIONS

These observations suggest that: (i) whenever TGF-beta1 is increased in CCl4-treated livers, it may induce liver fibrogenesis via nonparenchymal cells; (ii) the mitoinhibitory effect of TGF-beta1 on hepatocytes is transiently relieved by down-regulation of TGF-beta receptors for 72 h post-damage; and (iii) the resistance to TGF-beta growth inhibition between 24 to 48 h may be predominantly due to down-regulation of the expression of TGFbetaRII.

Ligand-dependent and -independent interactions with the transforming growth factor type II and I receptor subunits reside in the aminoterminal portion of the ectodomain of the type III subunit

The type III receptor for transforming growth factor beta (TGFbeta), which exhibits no kinase activity, binds TGFbeta1 and TGFbeta2 and is involved in assembly and activity of the multi-subunit TGFbeta signal transduction complex. Recently we showed that TGFbeta receptor type III (TbetaRIII) can participate in a complex composed of the dimeric TGFbeta ligand and a type III, II, and I receptor subunit. The interaction of the TbetaRIII subunit with TbetaRII is TGFbeta-dependent, whereas interaction with TbetaRI is TGFbeta-independent. Here we use coexpression of the three types of TGFbeta receptors in baculoviral-infected insect cells to determine which parts of the unglycosylated TbetaRIII receptor participate in the binding of TGFbeta, the TGFbeta-dependent interaction with TbetaRII and the TGFbeta-independent interaction with TbetaRI. The results suggest that the first 500 amino acid residues in the aminoterminal portion of TbetaRIII exhibit all three properties.

Endovascular treatment of intractable oronasal bleeding associated with severe craniofacial injury

BACKGROUND

Severe craniofacial injury may cause intractable oronasal bleeding, which is refractory to conventional treatments. This study will evaluate the efficacy of endovascular treatment for such oronasal bleeding.

METHODS

Nine males between the ages of 19 and 62 years who had intractable oronasal bleeding resulting from severe craniofacial injuries received treatments of transarterial embolization using Gelfoam pledgets, polyvinyl alcohol particles, or platinum coils. We then reviewed their clinical and neuroradiologic characteristics retrospectively.

RESULTS

In all but one case, angiography demonstrated bleeding points as extravasation. These bleeding points were multiple in seven cases. Except for bleeding from ethmoidal arteries, selective embolization was successful. In all cases, intractable oronasal bleeding was controlled. Patient survival was not directly related to oronasal bleeding, but rather was strongly correlated with associated brain injuries.

CONCLUSION

Endovascular treatment is an acceptable treatment for intractable oronasal bleeding associated with severe craniofacial injuries when conventional treatments have failed.

The heparan sulfate-fibroblast growth factor family: diversity of structure and function

The fibroblast growth factor (FGF) receptor complex is a ubiquitous regulator of development and adult tissue homeostasis that bridges the peri-cellular matrix and the intracellular environment. Diverse members of the FGF polypeptide family, the FGF receptor tyrosine kinase (FGFRTK) family and the FGF receptor heparan sulfate proteoglycan (FGFRHS) family combine to result in active and specific FGFR signal transduction complexes. Regulated alternate splicing and combination of variant subdomains give rise to diversity of FGFRTK monomers. Divalent cations cooperate with the FGFRHS to conformationally restrict FGFRTK trans-phosphorylation, which causes depression of kinase activity and facilitates appropriate activation of the FGFR complex by FGF. Diffusional and conformational molecular models of the oligomeric FGFR complex are presented to explain how different point mutations in the FGFRTK commonly cause craniofacial and skeletal abnormalities of graded severity by graded increases in FGF-independent activity of total FGFR complexes. The role of the FGF family in liver growth and function and in prostate tumor progression is discussed.

Fibroblast growth factor receptor 2 limits and receptor 1 accelerates tumorigenicity of prostate epithelial cells

Progressive loss of the differentiated phenotype and communication with stroma accompanies the transition of nonmalignant rat prostate epithelial cells to anaplastic, malignant tumors. Here we show that cell surface expression of the fibroblast growth factor receptor 2 (FGFR2) tyrosine kinase is reduced in malignant tumor cell populations (type II) and undetectable at the mRNA level in 30% of cells. This is in addition to the irreversible loss by splice switching of the FGFR2 ectodomain that abrogates response to FGF-7 and homologues from the stroma. One hundred % of type II malignant cells express FGFR1, which is normally expressed in the stroma. Expression of the FGFR1 kinase in premalignant type I tumor epithelial cells by transfection accelerated progression to the malignant phenotype. In contrast to the FGFR2 kinase fused to the ectodomain of FGFR1, the FGFR1 kinase failed initially to support a mitogenic response to FGF-2 in type I tumor cells. However, the FGFR1-transfected cells acquired a mitogenic response after extensive proliferation of the cell population. Resident FGFR2 and ectopic FGFR1 appeared to be partitioned in the type I cells, because neither full-length nor truncated isoforms of FGFR1 affected the mitogenic response of the other. Restoration of the FGFR2IIIb kinase to malignant cells expressing FGFR1 depressed tumor growth rates, restored responsiveness to stromal cells, and restored epithelial cell differentiation. These observations reveal that homologous FGFR1 and FGFR2 kinases play very different roles in cell growth and differentiation and in development and support of the malignant phenotype.

Heparan sulfate is required for interaction and activation of the epithelial cell fibroblast growth factor receptor-2IIIb with stromal-derived fibroblast growth factor-7

Fibroblast growth factor-7 (FGF-7) and a specific splice variant of the FGF tyrosine kinase receptor family (FGFR2IIIb) constitute a paracrine signaling system from stroma to epithelium. Different effects of the manipulation of cellular heparan sulfates and heparin on activities of FGF-7 relative to FGF-1 in epithelial cells suggest that pericellular heparan sulfates may regulate the activity of FGF-7 by a different mechanism than other FGFs. In this report, we employ the heparan sulfate-binding protein, protamine sulfate, to reversibly block cellular heparan sulfates. Protamine sulfate, which does not bind significantly to FGF-7 or FGFR2IIIb, inhibited FGF-7 activities, but not those of epidermal growth factor. The inhibition was overcome by increasing the concentrations of FGF-7 or heparin. Heparin was essential for binding of FGF-7 to recombinant FGFR2IIIb expressed in insect cells or FGFR2IIIb purified away from cell products. These results suggest that, similar to other FGF polypeptides, heparan sulfate within the pericellular matrix is required for activity of FGF-7. Differences in response to heparin and alterations in the BULK heparan sulfate content of cells likely reflect FGF-specific differences in the cellular repertoire of multivalent heparan sulfate chains required for assembly and activation of the FGF signal transduction complex.

[Management of subarachnoid hemorrhages without detectable aneurysm]

In this study, 21 patients with subarachnoid hemorrhage (SAH) but negative angiography were evaluated. Angiography was performed twice on each patient, that is, on admission and at 2 weeks following admission. All patients had severe headache of sudden onset, a characteristic manifestation of SAH. Clinical grades on admission (Hunt and Kosnik classification) were generally good: 17 patients were in grade I or II and 4 patients were in grade III. SAH was confirmed by the presence of subarachnoid clot on CT in all cases. Based on the distribution of SAH, CT findings were classified into two patterns, i.e., perimesencephalic and non-perimesencephalic patterns. Four patients showed the perimesencephalic pattern and the remaining 17 the non-perimesencephalic. The period of follow-up ranged from 20 days to 11 years 6 months, with a mean of 6 years 10 months. Except for three recent cases, the mean follow-up period in 8 years 9 months. Exploratory craniotomies probing for aneurysms have been performed in four patients, but no aneurysms have been found in any of these cases. Clinical deterioration associated with vasospasm was observed in one patient. A communicating hydrocephalus requiring a shunting procedure was observed in three patients showing the non-perimesencephalic type CT pattern. Rebleeding occurred in one patient who subsequently died of what may be a dissecting aneurysm of the vertebral artery. One patient who was able to return to full activity experienced symptoms attributable to SAH such as frequent headaches and increased fatigability. Complete recovery was observed in the remaining 19 patients. Two of them, however, later died due to myocardial infarction and aging, respectively. Given these generally positive outcomes, it should be possible to inform such patients of the benignity of their condition. Angiography may not demonstrate a ruptured aneurysm on initial examination in all cases of aneurysmal SAH. Serial angiography, however, can provide a definite diagnosis of the dissecting aneurysm. Therefore, repeat angiography, particularly, when possible, digital subtraction angiography, is necessary to rule out aneurysmal SAH. While small aneurysms or microaneurysms are often found through exploratory craniotomy, we do not agree with the opinion that surgery may be appropriate for certain patients with SAH but with negative angiography. The natural history concerning rebleeding in such cases, as well as morbidity and mortality associated with hemorrhage, remains to be defined. Furthermore, there are reservations regarding whether coagulation of these abnormalities with bipolar cautery constitutes definitive treatment.

Direct extracranial-intracranial bypass for children with moyamoya disease

To improve cerebral hypoperfusion in the ischemic type of Moyamoya disease, we have applied superficial temporal artery-middle cerebral artery (STA-MCA) double anastomoses in combination with encephalo-myo-synangiosis (EMS) for 19 hemispheres of 10 children (age from 5 to 11 years at surgery). Two branches of the STA were anastomosed to the two cortical arteries which were selected in the watershed area of the cerebral hemisphere estimated as a hypoperfusion area on the preoperative angiograms. Before surgery transient ischemic attacks (TIAs) developed from every month to every 6 months in association with hyperventilation or sobbing. No perioperative completed stroke or wound complications was observed, although single TIA developed in four patients within 1 month after surgery. Postoperative angiogram demonstrated that, not only the preoperative watershed area, but also the most of the middle cerebral artery territory was oppacified via the 2 branches of the STA in all 19 hemispheres. In a mean follow-up period of 4 years, no ischemic episode was induced by hyperventilation, and there was no mental or neurological deterioration. STA-MCA double anastomoses, to the cerebral watershed area, in combination with EMS are safe and effective even for younger children with Moyamoya disease.

A homeo-interaction sequence in the ectodomain of the fibroblast growth factor receptor

Interaction of fibroblast growth factor receptors (FGFR) sufficient for a trans-phosphorylation event in which one intracellular domain is substrate for the other is essential for signal transduction. By analysis of the direct interaction of recombinant constructions co-expressed in baculoviral-infected insect cells, we identified a 17-amino acid sequence that is required for the stable interaction between ectodomains of FGFR. The sequence 160ERSPHRPILQAGLPANK176 (Glu160-Lys176) connects immunoglobulin modules II and III. In insect cells, the interaction between Glu160-Lys176 domains occurs independently of intact heparin or FGF binding domains. The sequence is not required for the binding of heparin or FGF-1, but is essential for mitogenic activity of the FGFR kinase in mammalian cells. The results support a model in which the homeo-interaction between Glu160-Lys176 in the ectodomain contributes to the interaction between intracellular domains in mammalian cell membranes (Kan, M., Wang, F., Kan, M., To, B., Gabriel, J. L., and McKeehan, W. L. (1996) J. Biol. Chem. 271, 26143-26148). We propose that the Glu160-Lys176 domain plays a pivotal role in restriction of the interaction between kinases by pericellular matrix heparan sulfate proteoglycan and divalent cations. Restrictions are overcome by FGF or constitutively by diverse gain of function mutations which cause skeletal and craniofacial abnormalities.

Skin dose reduction by a clinically viable magnetic deflector

A variable magnetic deflector which attaches onto the treatment head of a linear accelerator has reduced skin dose by as much as 65% for 6MV x-rays. The magnetic deflector is constructed from Neodymium Iron Boron (NdFeB) rare earth magnets. It weighs approximately 15 kg and is designed to easily fit onto the accessory mount of a clinical linear accelerator. All field sizes are attainable up to 35 cm x 35 cm at 100 cm SSD. The gap between the magnetic poles can be adjusted, providing the highest field strength for each field size. Magnetic field strengths up to 0.55 Tesla are attainable. For a 6MV x-ray beam with a 10 mm perspex block tray, surface dose is reduced from 29% to 14% and from 59% to 37% for a 20 cm x 20 cm and 35 cm x 35 cm field size, respectively. Results at varying SSD's have shown at least 10 cm of space must be allowed between the magnets and patient for adequate reduction of skin dose through removal of electron contaminants.

Heparin-dependent fibroblast growth factor activities: effects of defined heparin oligosaccharides

Heparin and related molecules have been identified as important participants in fibroblast growth factor (FGF) signaling although the mechanisms of action remain unclear. We have used heparin oligosaccharides to examine steps in the signaling process which could be affected by the polysaccharide. Immobilized FGF-1 and FGF-2 bound all sizes of oligosaccharides tested, ranging from tetrasaccharide to decasaccharide, at physiological salt concentration. Each group of oligosaccharide was eluted from the FGF affinity columns in several peaks, and larger oligosaccharides showed higher apparent affinity for the immobilized growth factors compared to the shorter ones. Heparin hexasaccharides were the smallest fragments providing complete protection of FGF-1 and FGF-2 against trypsin digestion. Tetrasaccharides, however, were able to provide partial protection. The requirement of heparin for ligand-receptor interaction was evaluated in receptor binding assays using Sf9 insect cells engineered to overexpress different recombinant FGF receptor (FGFR) species including FGFR1 beta, FGFR1 alpha or FGFR4 at the cell surface. In these assays hexasaccharides were the smallest fragments capable of stimulating FGF-receptor interaction. Over the range of concentrations examined, neither hexasaccharides nor octasaccharides were able to stimulate receptor binding to the level attained by intact heparin. In fact, these oligosaccharides interfered with the ability of intact heparin in promoting FGF-receptor binding. The presence of both stimulatory and inhibitory activities in hexasaccharide and octasaccharide populations could be attributed to structural heterogeneity within the oligosaccharide preparations. However, similar observations were obtained with "highly-sulfated" structurally homogeneous preparations of hexasaccharide and octasaccharide, although these molecules generally had greater stimulatory and less inhibitory activity than their structurally heterogeneous counterparts. Hexasaccharides were found to be the smallest fragments able to potentiate the FGF-1-induced 3T3 cell proliferation while their effect on FGF-2 signaling was less clear. These observations suggest that heparin can modulate FGF-signaling at several stages with different end results.

Growth and differentiation of periodontal ligament-derived cells in serum-free defined culture

We have developed a serum-free medium for the growth and differentiation of periodontal ligament-derived cells (PLC). In addition, the expression of both fibroblast growth factor (FGF) and FGF receptor (FGFR) in the PLC was investigated by immunohistochemical examination, heparin affinity chromatography (HAC), and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Optimal growth of the cells was achieved in Iscove's modified Dulbecco's medium supplemented with insulin, transferrin, 2-mercaptoethanol, 2-ethanolamine, sodium selenite, and oleic acid in type-I collagen-coated dishes. Both FGF-1 and FGF-2 stimulated cell growth and inhibited differentiation as measured by inhibition of alkaline phosphatase activity of the cells. An immunohistochemical analysis of FGF-1 and FGF-2 revealed that immunoreactive FGF-1 and FGF-2 were detected predominantly in the cytoplasm of growing cells. In addition, perinuclear FGF-1 staining and nuclear FGF-2 staining were observed in the same growing cells. In contrast, a faint diffuse staining of FGF-1 and FGF-2 was detected in cytoplasm of the confluent differentiated cells. The 2.15 M NaCl eluate from HAC of the cell extracts exhibited growth-promoting activities for the PLC, and it also stimulated the growth of human umbilical vein-derived endothelial cells and inhibited binding of [125I]-FGF to its receptors, indicating the cells produced FGFs or FGF-like growth factors. RT-PCR analysis revealed that the cells expressed FGFR-1 mRNA but not mRNAs for FGFR-2, FGFR-3 and FGFR-4 mRNA. These results suggest that the FGF-FGFR-1 system plays an important role in the growth and differentiation of periodontal ligament-derived cells.

Immunohistochemical localization of fibroblast growth factor-1 (FGF-1), FGF-2 and fibroblast growth factor receptor-1 (FGFR-1) in pleomorphic adenoma of the salivary glands

Fibroblast growth factor-1 (FGF-1) and FGF-2 are heparin-binding polypeptides that are potent mitogens for neoplastic cells. In this study, fibroblast growth factor-1 (FGF-1), FGF-2, and fibroblast growth factor receptor-1 (FGFR-1) were immunohistochemically analyzed in 10 patients with pleomorphic adenoma of the salivary gland by using specific monoclonal antibodies. The tumor tissues were histopathologically classified as: tubular, solid, myxoid or chondroid. Both FGF-1 and FGF-2 were immunohistochemically identified in the tumor cells of all histological types. In addition, immunoreactive FGF-2 was also found in the basement membrane of tubular type tumor cells. Conversely, FGFR-1-positive tumor cells were essentially confined to the tubular and solid areas of tumors. Tumor cells in the myxoid and chondroid areas were FGFR-1 immunonegative. These results suggest that the co-expression of FGF and its receptor appears to be related to the proliferative activity of tumor cells in the tubular and solid areas, whereas loss of FGF receptor expression may be associated with the differentiation of tumor cells into myxoid and chondroid tissue types.

Serological evaluation of soluble CD44 in renal cancer

In this study, we examined the feasibility of using elevated serum CD44 concentration as an indicator in renal cancer. We performed enzyme-linked immunosorbent assays using 63 sera obtained from 47 patients with renal cancer and 16 healthy controls and evaluated the clinico-pathological parameters. The concentration of soluble CD44 standard (sCD44std), indicating the concentration of all circulating CD44 isoforms, was significantly higher in renal cancer patients than in normal individuals (745+/-170 ng/ml vs. 563+/-159 ng/ml, P=0.001). The concentration of soluble CD44 splice isoforms sharing exon v6 (sCD44v6) was also higher in the same patients (287+/-121 vs. 220+/-59, P=0.056). However, there were no correlations between the concentrations of sCD44std or sCD44v6 and clinico-pathological parameters such as grade, stage, histological type, tumor size and growth type. The ratio of sCD44std/sCD44v6 was higher in the rapid growth-type cancers than in the slow growth-type cancers (3.95+/-2.12 vs. 2.63+/-0.82, P = 0.014). These findings suggested that the serum concentration of unknown soluble CD44 isoforms not sharing exon v6, which are present in sCD44std, increases in patients with rapid growth-type cancers. These findings indicated that sCD44std and sCD44v6 are not useful indicators of tumor burden and metastasis in patients with renal cancer, but that an unknown sCD44 isoform(s) plays a role in the biological behavior of the rapid growth-type cancers.

Induction of FGF-7 after kidney damage: a possible paracrine mechanism for tubule repair

A member of the fibroblast growth factor (FGF) family, keratinocyte growth factor (FGF-7 has unique specificity for epithelial cells. We investigated the role of FGF-7 in repair of proximal tubular damage caused by S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFEC). In situ hybridization localized FGF-7 to interstitial cells in the medulla and outer stripe of the outer medulla. Interstitial FGF-7 expression increased throughout the kidney 1 day after TFEC treatment. FGFR2 IIIb mRNA was high in the papilla and medulla and also increased after TFEC administration. By in situ hybridization, FGFR2 IIIb was localized to the tubular epithelium, particularly in collecting ducts. Proliferation of collecting duct epithelial cells increased in adult kidney after damage to the proximal tubule. FGFR2 IIIb, but not FGF-7, mRNA was also expressed by rat proximal tubule epithelial (RPTE) cells in vitro, and FGF-7 increased DNA synthesis in RPTE. Thus FGFR2 IIIb and FGF-7 expression is segregated between epithelial and interstitial cells forming a paracrine growth factor loop. These results raise the possibility that a novel paracrine growth loop is activated by chemical damage and regulates epithelial cell growth during tubular repair.

Molecular modeling and deletion mutagenesis implicate the nuclear translocation sequence in structural integrity of fibroblast growth factor-1

The sequence NYKKPKL in the NH2 terminus of fibroblast growth factor (FGF)-1 has been proposed to affect the long term activities of FGF-1 through its function as a nuclear translocation signal or its role in stabilization of the structure required to sustain binding and activation of the transmembrane receptor kinase. A dynamic molecular model of FGF-1 docked into a duplex of the FGF receptor ectodomain and a hexadecameric heparin chain suggests that the NYKKPKL sequence does not directly interact with heparin or the receptor, but rather the lysine-leucine residues within the sequence indirectly stabilize a major receptor-binding domain. Concurrent with a marked increase in dependence on exogenous heparin for optimal activity, sequential deletion of residues in the NYKKPKL sequence in FGF-1 resulted in a progressive loss of thermal stability, resistance to protease, mitogenic activity, and affinity for the transmembrane receptor. The largest change resulted from deletion of the entire sequence through the lysine-leucine residues. In the presence of sufficiently high concentrations of heparin, the deletion mutants exhibited mitogenic activity equal to wild-type FGF-1. The results confirm that a primary role of the NYKKPKL sequence domain is to maintain the structural integrity of FGF-1 required for optimal binding to and activation of the heparan sulfate-transmembrane receptor complex.

Divalent cations and heparin/heparan sulfate cooperate to control assembly and activity of the fibroblast growth factor receptor complex

Polypeptides of the fibroblast growth factor (FGF) family are ubiquitous bioregulators within tissues whose activity is controlled by heparan sulfates within the pericellular matrix. FGF and the ectodomain of their transmembrane tyrosine kinase receptors (FGFR) exhibit heparin-binding domains that when juxtaposed in a FGF middle dotFGFR complex can accommodate a single, potentially bivalent, decameric polysaccharide chain in a ternary complex. Here we show that the interaction of heparin with FGF ligands is not affected by divalent cations. In contrast, the high affinity interaction (apparent Kd = 10 nM) of heparin with FGFR requires Ca2+ or Mg2+ at physiological concentrations. Divalent cations maintain FGFR in a heparan sulfate-dependent state in respect to FGF binding and an FGF- and heparan sulfate-dependent state in respect to autophosphorylation. A model is proposed where divalent cations and heparan sulfate cooperate to maintain FGFR in a conformation that restricts trans-phosphorylation between intracellular kinase domains. The restriction is overcome by FGF or constitutively as a common consequence of diverse mutations in FGFR associated with skeletal and craniofacial abnormalities.