Molecular characterization of recombinant human acidic fibroblast growth factor produced in E. coli: comparative studies with human basic fibroblast growth factor

Large-Scale Preparation of Highly Stable Recombinant Human Acidic Fibroblast Growth Factor in Escherichia coli BL21(DE3) plysS Strain

In this study, the optimum human aFGF gene encoding haFGF₁₃₅ was cloned in pET3c and transferred to Escherichia coli BL21(DE3) plysS. To enhance the yield of fermentation and the expression level of the target protein, the fermentation parameters, including temperature, pH, dissolved oxygen, glucose concentration, ammonium chloride concentration, induction time, and inducer (IPTG) concentration, were optimized. The optimized fermentation parameters were used in large-scale fermentation (30 L). Ion-exchange and heparin-affinity column chromatography techniques were used for separation and purification of rhaFGF₁₃₅ protein. HPLC, isoelectric focusing electrophoresis, and mass spectrometry were used to detect the purity, isoelectric point, and molecular weight and peptide map of rhaFGF₁₃₅ protein, respectively. Mitogenic activity of rhaFGF₁₃₅ protein was detected in NIH-3T3 cells and a full-thickness injury wound diabetic rat model. The production and expression level of rhaFGF₁₃₅ in the 30-L scale fermentation reached 80.4 ± 2.7 g/L culture and 37.8% ± 1.8%, respectively. The RP-HPLC and SDS-PAGE purity of the final rhaFGF₁₃₅ product almost reached 100%, and the final pure protein yield was 158.6 ± 6.8 mg/L culture. Finally, the cell and animal experiments showed that rhaFGF₁₃₅ retained a potent mitogenic activity. The large-scale process of rhaFGF₁₃₅ production reported herein is relatively stable and time-saving, and thus, it can be used as an efficient and economic strategy for the synthesis of rhaFGF₁₃₅ at the industrial level.

Functional Analysis of a Putative Type III Secretion System in Stress Adaption by Mesorhizobium alhagi CCNWXJ12-2T

Mesorhizobium alhagi CCNWXJ12-2^T, isolated from root nodules of the desert plant Alhagi sparsifolia, contains two type III secretion systems (T3SSs). T3SSs are specialized machinery with wide distribution in bacteria that inject effector proteins into target cells. Our previous study showed that the expression of M. alhagi T3SS1 is upregulated in high-salt conditions. Here, phylogenetic analysis of T3SS1 using the core protein RhcU suggested that T3SS1 belongs to the α-Rhc II subgroup of the Rhc T3SS family. To elaborate the function of M. alhagi CCNWXJ12-2^T T3SS1 in stress adaption, two T3SS1 mutants (ΔrhcQ and ΔMA29250) were constructed and analyzed. β-galactosidase transcriptional fusion assays showed that activity of the promoter of T3SS1 was induced by salts. Mutant ΔrhcQ was more sensitive to NaCl and LiCl than the wild-type, but ΔMA29250 was not. Both mutants were more sensitive to KCl than the wild-type. The intracellular Na⁺ concentration in ΔrhcQ in high-NaCl conditions (0.4 M) increased by 37% compared to that of the wild-type strain, while the Na⁺ concentration in ΔMA29250 increased by 13%. The K⁺ concentration in both mutants increased by 16% compared to the wild-type in high-KCl conditions (0.3 M). Strain ΔrhcQ showed decreased survival compared to the wild-type after treatment with H₂O₂, while the survival rate of ΔMA29250 was almost the same as that of the wild-type. Antioxidant enzyme activities in ΔrhcQ were lower than those in the wild-type strain, but this was not the case for ΔMA29250. Our data elucidate the beneficial effects of T3SS1 in the adaption of M. alhagi CCNWXJ12-2^T to stress.

Peptides derived from the histidine–proline rich glycoprotein bind copper ions and exhibit anti-angiogenic properties

A peptide belonging to the histidine–proline rich glycoprotein binds copper(ii), inhibiting metal angiogenic responses in endothelial cells.

SHuffle™ T7 strain is capable of producing high amount of recombinant human fibroblast growth factor-1 (rhFGF-1) with proper physicochemical and biological properties

BACKGROUND

Human fibroblast growth factor-1 (FGF-1) has powerful mitogenic activities in a variety of cell types and plays significant roles in many physiological processes e.g. angiogenesis and wound healing. There is increasing demand for large scale production of recombinant human FGF-1 (rhFGF-1), in order to investigate the potential medical use. In the present study, we explored SHuffle™ T7 strain for production of rhFGF-1.

METHODS

A synthetic gene encoding Met-140 amino acid form of human FGF-1 was utilized for expression of the protein in three different E. coli hosts (BL21 (DE3), Rosetta-gami™ 2(DE3), SHuffle™ T7). Total expressions and soluble/insoluble expression ratios of rhFGF-1 in different hosts were analyzed and compared. Soluble rhFGF-1 produced in SHuffle™ T7 cells was purified using one-step heparin-Sepharose affinity chromatography and characterized by a variety of methods for physicochemical and biological properties.

RESULTS

The highest level of rhFGF-1 expression and maximum soluble/insoluble ratio were achieved in SHuffle™ T7 strain. Using a single-step heparin-Sepharose chromatography, about 1500mg of purified rhFGF-1 was obtained from one liter of the culture, representing purification yield of ∼70%. The purified protein was reactive toward anti-FGF-1 ployclonal antibody in immunoblotting. Mass spectrometry confirmed the protein had expected amino acid sequence and molecular weight. In reverse-phase high-performance liquid chromatography (RP-HPLC), the protein displayed the same retention time with the human FGF-1 standard, and purity of 94%. Less than 0.3% of the purified protein was comprised of oligomers and/or aggregates as judged by high-performance size-exclusion chromatography (HP-SEC). Secondary and tertiary structures of the protein, investigated by circular dichroism and intrinsic fluorescence spectroscopy methods, respectively, represented native folding of the protein. The purified rhFGF-1 was bioactive and stimulated proliferation of NIH 3T3 cells with EC50 of 0.84ng/mL.

CONCLUSION

Although SHuffle™ T7 has been introduced for production of disulfide-bonded proteins in cytoplasm, we herein successfully recruited it for high yield production of soluble and bioactive rhFGF-1, a protein with 3 free cysteine and no disulfide bond. To our knowledge, this is the highest-level of rhFGF-1 expression in E. coli reported so far. Extensive physicochemical and biological analysis showed the protein had similar characteristic to authentic FGF-1.

Lysyl oxidase and enhancement of cell proliferation and angiogenesis in oral squamous cell carcinoma

BACKGROUND

Lysyl oxidase (LOX) is a copper-dependent enzyme that cross-links collagen and elastin in the extracellular matrix. LOX overexpressed in various tumors. The manner in which LOX affects tumor growth remains controversial.

METHODS

Chemical treatment and gene transfection were used to induce LOX overexpression or inhibition in cell lines SAS and SVEC4-10. LOX mRNA, protein, and activity were confirmed before tube formation assay and tumorigenesis. The microvessels in the tumor section were detected by immunostaining CD31-positive endothelial cells.

RESULTS

LOX overexpression and copper induction of LOX activity increased SVEC4-10 tube formation. LOX silencing and β-aminopropionitrile inhibition of LOX activity had opposite effects. LOX overexpression increased proliferation and proliferating cell nuclear antigen expression. High LOX expression clones increased tumor size in a tumorigenesis model. The microvascular numbers were higher in LOX overexpression tumors than in control tumors.

CONCLUSION

LOX can induce cell proliferation and angiogenesis in oral squamous cell carcinoma.

Production of biologically active IgG hinge-tag soluble epidermal growth factor receptors (ErbB)

The extracellular domains (ECD) of epidermal growth factor receptors, ErbB1, 2, 3 and 4, were designed as soluble dimeric forms. Each ECD was fused to a short hinge region derived from IgG, such that the stable dimer could be formed with disulfide bridges. This hinge-tagged design minimized the molecular weight to approximately 50% of the conventional Fc-fusion design without an Fc domain of IgG. The refolded dimers could be easily analyzed and characterized by SDS-PAGE. Hinge-tagged soluble ErbBs demonstrated significant affinity for betacellulin and heregulin. The IgG hinge-tag should be a simple method to design soluble dimers that would be useful for high throughput screening of ligands, antagonists or derivatives.

Cations modulate polysaccharide structure to determine FGF-FGFR signaling: a comparison of signaling and inhibitory polysaccharide interactions with FGF-1 in solution

For heparan sulfate (HS) to bind and regulate the activity of proteins, the polysaccharide must present an appropriate sequence and adopt a suitable conformation. The conformations of heparin derivatives, as models of HS, are altered via a change in the associated cations, and this can drastically modify their FGF signaling activities. Here, we report that changing the cations associated with an N-acetyl-enriched heparin polysaccharide, from sodium to copper(II), converted it from supporting signaling through the fibroblast growth factor receptor (FGF-1-FGFR1c) tyrosine kinase signaling system to being inhibitory in a cell-based BaF3 assay. Nuclear magnetic resonance and synchrotron radiation circular dichroism (SRCD) spectroscopy demonstrated that the polysaccharide conformation differed in the presence of sodium or copper(II) cations. Electron paramagnetic resonance confirmed the environment of the copper(II) ion on the N-acetyl-enriched polysaccharide was distinct from that previously observed with intact heparin, which supported signaling. Secondary structures in solution complexes of polysaccharides with FGF-1 (which either supported signaling through FGFR1c or were inhibitory) were determined by SRCD. This allowed direct comparison of the two FGF-1-polysaccharide complexes in solution, containing identical molecular components and differing only in their cation content. Subtle structural differences were revealed, including a reduction in the level of disordered structure in the inhibitory complex.

Do cytokines have any role in Wilson's disease?

The aim of this study was to determine the serum cytokine levels in patients with Wilson's disease (WD) and correlate with phenotype, therapeutic status and laboratory data. In this cross-sectional study, the serum levels of cytokines were estimated in 34 patients (M : F, 23 : 11; drug-naive, 11) with WD (mean age: 13.8 +/- 8.6 and 19.6 +/- 9.03 years) and compared with 30 controls. The following serum cytokines were analysed using enzyme-linked immunosorbent assay: (i) tumour necrosis factor (TNF)-alpha, (ii) interferon (IFN)-gamma, (iii) interleukin (IL)-2, (iv) IL-6 and (v) IL-4. Serum TNF-alpha (P < 0.001), IFN-gamma (P = 0.005) and IL-6 (P < 0.001) were detectable in WD compared with controls. However, serum level elevation of IL-4 (P = 0.49) and IL-2 (P = 0.11), although detectable compared with controls, was statistically insignificant. The disease severity and therapeutic status did not affect the cytokines. Presence of anaemia, leucopenia, thrombocytopenia, pancytopenia and hepatic dysfunction did not influence cytokine levels. There was a significant negative correlation between IL-6 and ceruloplasmin (P = 0.04) and anti-inflammatory cytokines (IL-4) and copper level (P = 0.01). Serum cytokines, both proinflammatory and anti-inflammatory subtypes, were elevated significantly in patients with WD. Further studies would establish their role in its pathogenesis.

The role of copper in drug-resistant murine and human tumors

Multidrug resistance (MDR) is still a major threat to successful clinical application of cancer chemotherapy. Copper plays an important role in biological systems, and copper is also involved in carcinogenesis. In the present investigation, we addressed the question whether metal copper might be involved in drug resistance of murine and human tumors. By means of atomic absorption spectroscopy, we determined serum copper concentrations. We found that the blood serum of tumor-bearing mice contained higher amounts of copper than healthy mice with tumors. Secondly, mice bearing doxorubicin-resistant Ehrlich ascites carcinoma- or cyclophosphamide-resistant Lewis lung carcinoma contained more copper in their serum than mice bearing the corresponding drug-sensitive parental tumors. Furthermore, the analysis of patients with breast cancer, colon carcinoma or lung cancer showed that the serum copper contents were higher in patients not responding to chemotherapy when compared to patients whose tumors responded to treatment. The copper levels in serum of healthy volunteers were lower than in cancer patients irrespective of their response to chemotherapy. Our results imply that the level of serum copper may be considered as a biomarker for treatment response.

Copper and angiogenesis: unravelling a relationship key to cancer progression

1. Angiogenesis, the formation of new capillaries from existing vasculature, is a critical process in normal physiology as well as several physiopathologies. A desire to curb the supportive role angiogenesis plays in the development and metastasis of cancers has driven exploration into anti-angiogenic strategies as cancer therapeutics. Key to this, angiogenesis additionally displays an exquisite sensitivity to bioavailable copper. Depletion of copper has been shown to inhibit angiogenesis in a wide variety of cancer cell and xenograft systems. Several clinical trials using copper chelation as either an adjuvant or primary therapy have been conducted. Yet, the biological basis for the sensitivity of angiogenesis remains unclear. Numerous molecules important to angiogenesis regulation have been shown to be either directly or indirectly influenced by copper, yet a clear probative answer to the connection remains elusive. 2. Measurements of copper in biological systems have historically relied on techniques that, although demonstrably powerful, provide little or no information as to the spatial distribution of metals in a cellular context. Therefore, several new approaches have been developed to image copper in a biological context. One such approach relies on synchrotron-derived X-rays from third-generation synchrotrons and the technique of high resolution X-ray fluorescence microprobe (XFM) analysis. 3. Recent applications of XFM approaches to the role of copper in regulating angiogenesis have provided unique insight into the connection between copper and cellular behaviour. Using XFM, copper has been shown to be highly spatially regulated, as it is translocated from perinuclear areas of the cell towards the tips of extending filopodia and across the cell membrane into the extracellular space during angiogenic processes. Such findings may explain the heightened sensitivity of this cellular process to this transition metal and set a new paradigm for the kinds of regulatory roles that the spatial dynamics of cellular transition metals may play.

Combined effects of treatment with trientine, a copper-chelating agent, and x-irradiation on tumor growth in transplantation model of a murine fibrosarcoma

Combined effects of treatment with trientine, a copper-chelating agent, and X-irradiation on development of fibrosarcoma using a murine transplantation model in vivo and on cellular survival in vitro were examined. Copper contents in the tumors and serum of trientine-treated mice were significantly lower than those of untreated mice. The tumor volumes of mouse fibrosarcoma QRsp-11 cells increased more slowly in the trientine-treated and the X-irradiated mice than in the control mice from 10 to 24 days postinoculation. The extent of inhibition of tumor growth by X-irradiation at 3 Gy was similar to that obtained by treatment with trientine. A combination of trientine and X-irradiation at 3 Gy showed inhibitory effects on tumor growth similar to those obtained by X-irradiation at 6 Gy. The results showed that trientine and X-irradiation interacted additively in inhibition of tumor growth. When QRsp-11 cells and mouse and bovine endothelial cells were treated with trientine after X-irradiation, the surviving fractions of the cells with combined treatments were essentially consistent with the products of the surviving fractions of trientine-treated cells and those of X-irradiated cells. When the cells were pretreated with trientine and X-irradiated, the surviving fractions of the pretreated cells were lower than those of cells without treatment.

Trientine, a copper-chelating agent, induced apoptosis in murine fibrosarcoma cells in vivo and in vitro

Anti-copper treatments have been investigated to determine whether they suppress angiogenesis and tumor development since Cu is widely accepted as being required for angiogenesis. We examined the effects of treatment with trientine, a copper-chelating agent, on tumor development in a murine xenograft model using fibrosarcoma-derived transplantable QRsp-11 cells and C57BL/6 mice and induction of apoptosis in tumor cells and endothelial cells in vivo and in vitro. The tumor volumes increased more slowly in trientine-treated mice than in untreated mice. Tumor volumes in the treated mice were significantly smaller than those in the untreated mice at 24 days postinoculation (d.p.i.) of tumor cells. A cluster of pyknotic tumor cells and morphological abnormalities in capillary endothelial cells were observed in the tumors of trientine-treated mice but not in the tumors of untreated mice. The proportions of apoptotic and necrotic cells in the tumors of treated mice were approximately 3.5-fold higher than those in the tumors of untreated mice at 14 d.p.i. When the cells were treated with trientine in vitro, mouse endothelial cells and bovine primary endothelial cells showed an approximately 10-fold higher sensitivity to trientine than QRsp-11 cells in terms of D37. However, the proportion of apoptotic cells in endothelial cells was significantly lower than that in QRsp-11 cells after treatment with trientine. These results show that apoptosis was induced in tumor cells by treatment with trientine in vivo and in vitro.

X-ray fluorescence microscopy reveals large-scale relocalization and extracellular translocation of cellular copper during angiogenesis

Although copper has been reported to influence numerous proteins known to be important for angiogenesis, the enhanced sensitivity of this developmental process to copper bioavailability has remained an enigma, because copper metalloproteins are prevalent and essential throughout all cells. Recent developments in x-ray optics at third-generation synchrotron sources have provided a resource for highly sensitive visualization and quantitation of metalloproteins in biological samples. Here, we report the application of x-ray fluorescence microscopy (XFM) toin vitro models of angiogenesis and neurogenesis, revealing a surprisingly dramatic spatial relocalization specific to capillary formation of 80-90% of endogenous cellular copper stores from intracellular compartments to the tips of nascent endothelial cell filopodia and across the cell membrane. Although copper chelation had no effect on process formation, an almost complete ablation of network formation was observed. XFM of highly vascularized ductal carcinomas showed copper clustering in putative neoangiogenic areas. This use of XFM for the study of a dynamic developmental process not only sheds light on the copper requirement for endothelial tube formation but highlights the value of synchrotron-based facilities in biological research.

Radiotherapy and antiangiogenic TM in lung cancer

Tetrathiomolybdate (TM) is a potent nontoxic orally delivered copper complexing agent under development for the last several years for the treatment of Wilson's disease. It has been shown to block angiogenesis in primary and metastatic tumors. Therefore, the combination of cytotoxic radiotherapy (RT) and antiangiogenic TM could target both the existing tumor and the tumor microvasculature in a comprehensive strategy. Using a Lewis lung high metastatic (LLHM) carcinoma mouse tumor model, we demonstrate that the combination of TM and RT is more effective than either used as monotherapy. We also show that their therapeutic effects are additive, with no additional toxicity. We show that TM has no significant cytotoxicity in vitro against LLHM tumor cells, further supporting the antiangiogenic mechanism for its action.

The copper-chelating agent, trientine, suppresses tumor development and angiogenesis in the murine hepatocellular carcinoma cells

Angiogenesis is now recognized as a crucial process in tumor development, including hepatocellular carcinoma (HCC). Since HCC is known as a hypervascular tumor, anti-angiogenesis is a promising approach to inhibit the HCC development. Trientine dihydrochloride (trientine) is used in clinical practice as an alternative copper (Cu)-chelating agent for patients with Wilson's disease of penicillamine intolerance. In our study, we examined the effect of Cu-chelating agents on tumor development and angiogenesis in the murine HCC xenograft model. Although both trientine and penicillamine in the drinking water suppressed the tumor development, trientine exerted a more potent inhibitory effect than penicillamine. In combination with a Cu-deficient diet, both trientine and penicillamine almost abolished the HCC development. Trientine treatment resulted in a marked suppression of neovascularization and increase of apoptosis in the tumor, whereas tumor cell proliferation itself was not altered. In vitro studies also exhibited that trientine is not cytotoxic for the tumor cells. On the other hand, it significantly suppressed the endothelial cell proliferation. These results suggested that Cu plays a pivotal role in tumor development and angiogenesis in the murine HCC cells, and Cu-chelators, especially trientine, could inhibit angiogenesis and enhance apoptosis in the tumor with consequent suppression of the tumor growth in vivo. Since trientine is already used in clinical practice without any serious side effects as compared to penicillamine, it may be an effective new strategy for future HCC therapy.

The Role of Copper Suppression as an Antiangiogenic Strategy in Head and Neck Squamous Cell Carcinoma

OBJECTIVE

To determine whether tetrathiomolybdate (TM), a powerful chelator of copper, is capable of lowering the body stores of copper and suppressing the growth of head and neck squamous cell carcinoma in an orthotopic murine model.

STUDY DESIGN

In vivo, murine model.

METHODS

Twelve 8-week-old male C3H/HeJ mice were assigned to either a TM treatment group (n = 7) or a control group (n = 5). Serum samples were obtained from a single mouse in each group to measure the level of ceruloplasmin as a surrogate marker of total body copper on days 0, 4, and 7. Mice in both groups received a floor-of-mouth injection of 1.5 x 105 SCC VII/SF cells. After 7 to 10 days of tumor growth the treatment group received fresh water daily, to which TM was added to achieve an oral intake of 50 mg per mouse. The control group received only fresh drinking water daily. Tumor volume measurements were obtained every other day. Microvessel density counts were assessed in the tumors by Factor VIII analysis.

RESULTS

Measurable tumor growth was achieved in 100% of the mice by the tenth day. Total body copper was reduced by 28% from baseline levels in mice in the treatment group. The difference in mean tumor volume in the control group was 4.7 times greater than the TM-treated group at the completion of treatment (3004 mm3 and 633mm3, respectively). This accounted for an overall suppression rate of 79% (P =.008; two-tailed Student t test). In addition, microvessel density was reduced by 50% in the TM-treated group.

CONCLUSION

In this initial study, the first of its kind in head and neck squamous cell carcinoma, we have demonstrated the ability of TM to significantly suppress both the growth of squamous cell carcinoma and tumor vascularity in this orthotopic murine model, suggesting its potential for efficacy in the treatment of this disease in humans.

High-level expression of human acidic fibroblast growth factor and basic fibroblast growth factor in silkworm (Bombyx mori L.) using recombinant baculovirus

A hybrid of Autographa californica nuclear polyhedrosis virus and Bombyx mori nuclear polyhedrosis virus, which is infectious to both Spodoptera frugiperda and Bombyx mori, was prepared in our previous study. Two recombinant hybrid baculoviruses, carrying cDNAs of human acidic and basic fibroblast growth factors, respectively, were successfully constructed in this study, for the large-scale production of human aFGF and bFGF using silkworm as host. These recombinant viruses were used to inoculate silkworm larvae. After the infection, the recombinant proteins were not found in the hemolymph. Such nonsecretion from cells has also been observed in the established insect cell lines, Sf21 and Tn-5. Tissue distribution analysis indicated that the expressed products were mainly located in fat body and the production of the recombinant aFGF and bFGF was maximal at around 80 h postinfection. Therefore, silkworm larvae infected with recombinant viruses were dissected and fat bodies were collected for the purification of recombinant aFGF and bFGF. The expression levels in both cases were estimated to be as high as approximately 600-700 microg per larva. Furthermore, the recombinant proteins were characterized and their biological activities were evaluated by in vitro bioassay using cell culture.

Regulation of FGF-1 mitogenic activity by heparan sulfate oligosaccharides is dependent on specific structural features: differential requirements for the modulation of FGF-1 and FGF-2

The interaction of heparan sulfate (HS) (and the closely related molecule heparin) with FGF-1 is a requirement for enabling the growth factor to activate its cell surface tyrosine kinase receptor. However, little is known about the regulatory role of naturally occurring cell surface HS in FGF-1 activation. We have addressed this issue by utilizing a library of HS oligosaccharides, which are defined in both length and sulfate content. Mitogenic activation assays using these oligosaccharides showed that HS contained both FGF-1 activatory and inhibitory sugar sequences. Further analysis of these oligosaccharides showed a clear correlation between FGF-1 promoting activity and their 6-O-sulfate content. The results, in particular with the dodecasaccharide sequences, suggested that specific positioning of 6-O-sulfate groups may be required for the promotion of FGF-1 mitogenic activity. This may also be true for 2-O-sulfate groups though the evidence was not as conclusive. Differential activation of FGF-1 and FGF-2 was also observed and found to be mediated by both oligosaccharide length and sulfation pattern, with different specific O-sulfate positioning being implicated for the promotion of different growth factors. These results suggest that variation and tight control of the fine structure of HS may allow cells to not only control their positive/negative responses to individual FGFs but also to change specificity towards promotion of different members of the FGF family.

Inhibition of cell growth by a fused protein of human ribonuclease 1 and human basic fibroblast growth factor

Pancreatic-type RNases are considered to have cytotoxic potential due to their ability to degrade RNA molecules when they enter the cytosol. However, most of these RNases show little cytotoxicity because cells have no active uptake mechanism for these RNases and because the ubiquitous cytoplasmic RNase inhibitor is considered to play a protective role against the endocytotic leak of RNases from the outside of cells. To study the cytotoxic potential of RNase toward malignant cells targeting growth factor receptors, the C-terminus of human RNase 1 was fused to the N-terminus of human basic fibroblast growth factor (bFGF). This RNase-FGF fused protein effectively inhibited the growth of mouse melanoma cell line B16/BL6 with high levels of cell surface FGF receptor. This effect appeared to result from prolongation of the overall cell cycle rather than the killing of cells or specific arrest in a particular phase of the cell cycle. Thus, human RNase 1 fused to a ligand of cell surface molecules, such as the FGF receptor, is shown to be an effective candidate for a selective cell targeting agent with low toxic effects on normal cell types.

Fibroblast growth factor-1 induction of delayed-early mRNA expression in NIH 3T3 cells is prolonged by heparin addition

Fibroblast growth factor (FGF)-1, also known as acidic FGF, is a multifunctional heparin-binding protein that is mitogenic for a wide variety of cell types cultured in vitro and a potent angiogenic agent in vivo. These cellular responses are mediated via high-affinity binding to a family of four membrane-spanning tyrosine kinase receptors. FGF-1-stimulated mitogenesis is potentiated by heparin, a sulfated glycosaminoglycan. In this study, we examined the effect of exogenous heparin on FGF-1-inducible gene expression in murine NIH 3T3 cells using both wild-type FGF-1 and FGF-1/glu132, an FGF-1 mutant with a reduced apparent affinity for heparin. The induction levels and temporal expression kinetics of two immediate-early response mRNAs (early growth response gene-1, thrombospondin-1) as well as two delayed-early response mRNAs (proliferin, ornithine decarboxylase) were monitored by Northern blot hybridization analysis. We found that although FGF-1 alone can promote the initial induction of these four mRNAs, heparin coaddition is necessary for prolonged delayed-early mRNA expression. This heparin effect occurs when cells are stimulated with wild-type FGF-1 but not with FGF-1/glu132. Furthermore, FGF-1 and heparin must be added together at the initial time of mitogen stimulation and they must remain present in the cell culture medium for a minimum period of 8 h to promote sustained delayed-early mRNA expression. These findings are consistent with the proposal that heparin promotes a long-term FGF-1:FGFR interaction which is required for sustained delayed-early gene expression and a full mitogenic response.

Construction of a sensitive enzyme immunoassay for human fibroblast growth factor 9

Hybridomas secreting monoclonal antibodies (MAbs) against human fibroblast growth factor 9 (FGF-9) were established using recombinant human (rh) FGF-9 N33 as the immunogen. Among these, MAb 150-59 demonstrated a potent neutralizing activity against FGF-9. It arrested the FGF-9-induced growth of BALB/c 3T3 A31 cells at an equimolar dose of the factor. It also abrogated the in vivo thrombopoietic activity of FGF-9. Mitogenic activity of several other FGF family members such as FGF-1, FGF-2, and FGF-4 was not neutralized by this MAb. A sensitive sandwich enzyme immunoassay for FGF-9 was developed employing MAbs 150-59 and 13-3. The detection limit of this system was 3 pg/well. In this assay system, FGF-1 and FGF-2 were not cross-reactive up to 1 microgram/well. Using this system, the distribution of FGF-9 in rat organs was examined. FGF-9 could be detected only in the extract of rat cerebellum. Also, we detected a high amount of FGF-9 in the culture supernatant of certain cell lines originated from human tumor. These findings suggest that this enzyme immunoassay system may be used to clarify biological meaning of FGF-9.

Expression patterns of acidic and basic fibroblast growth factor in loach fish embryos

Heparin-binding fractions were taken from the heparin sepharose columns on which extracts of loach fish (Misgurnus anguillicaudatus) embryos from blastula, gastrula, 4-8 and 12-16 somites stages were applied. These heparin-binding fractions, except the fraction derived from 12-16 somite embryos, showed potent mitogenic activity on fibroblast-like cells derived from caudal fin blastema of goldfish. Western blot analysis of these heparin-binding fractions was carried out using monoclonal antibodies against human acidic and basic fibroblast growth factors (FGF-1 and-2). An immunoreactive FGF-1 band at 16 kD was detected in the heparin-binding fraction derived from embryos in each stage of blastula, gastrula and 4-8 somites. An immunoreactive FGF-2 band at 17 kDa was detected exclusively in the heparin-binding fraction derived from 4-8 somite embryos. In the heparin-binding fraction derived from 12-16 somite embryos neither immunoreactive FGF-1 nor-2 member band was detectable.

Overexpression of the gene for N-acylamino acid racemase from Amycolatopsis sp. TS-1-60 in Escherichia coli and continuous produciton of optically active methionine by a bioreactor

A DNA sequence encoding N-acylamino acid racemase (AAR) was inserted downstream from the T7 promoter in pET3c. The recombinant plasmid was introduced into Escherichia coli MM 294 lysogenized with a bacteriophage lambda having a T7 RNA polymerase gene. The amount of AAR produced by the E. coli transformant was 1100-fold more than that produced by Amycolatopsis sp. TS-1-60, the DNA donor strain. The AAR was purified to homogeneity from the crude extract of the E. coli transformant by two steps: heat treatment and Butyl-Toyopearl column chromatography. Bioreactors for the production of optically active amino acids were constructed with DEAE-Toyopearl-immobilized AAR and D- or L-aminoacylase. D- or L-methionine was continuously produced with a high yield from N-acetyl-DL-methionine by the bioreactor.

Molecular cloning and expression of human ribonuclease 4 cDNA

A cDNA coding for human ribonuclease 4 was isolated from a pancreas cDNA library and sequenced. This cDNA (996 bp) includes an entire open reading frame encoding mature protein (119 aa) following signal peptide (28 aa). Expression of mature protein in Escherichia coli showed an apparent molecular mass of about 16 kDa, which was slightly lower than the mature form of human RNase 1, in SDS-PAGE.

Stimulation of thrombopoiesis in mice by fibroblast growth factor 9

Fibroblast growth factor 9 (FGF-9), a novel member of the FGF family, was found to have thrombopoietic activity in vitro and in vivo. In an in vitro megakaryocyte colony-stimulating factor assay, anti-mouse interleukin-6 (IL-6) monoclonal antibody neutralized FGF-9 activity. This suggests that the activity may be exerted via IL-6 induction. BALB/c mice that received subcutaneous FGF-9 injections of 4 to 100 micrograms/day for 2 weeks showed a dose-dependent transient increase in peripheral platelet counts 10 to 12 days after the first treatment. Histologic studies showed a marked increase in megakaryocytes in bone marrow and extramedullary hematopoiesis in the spleen and the liver. Examination of changes in the DNA content of bone marrow megakaryocytes revealed that the ploidy distribution underwent a marked shift 3 days after FGF-9 injection, with a large increase in the 2N megakaryocyte population. The major modal ploidy shifted from the normal 16N to 2N. The number of megakaryocyte progenitor cells in FGF-9-treated mice increased up to 1.5-fold in the bone marrow and 10-fold in the spleen on day 6. These results indicate that FGF-9 acts on the in vivo proliferation of megakaryocytes.

Human parathyroid hormone: efficient synthesis in Escherichia coli using a synthetic gene, purification and characterization

Human parathyroid hormone is a peptide hormone consisting of 84 amino acid residues. Production of small proteins by direct expression in Escherichia coli is often unsuccessful owing to susceptibility of the mRNA and/or the product to endogenous enzymes. In this study, direct expression of the hormone at an excellent level (over 100 mg/L) has been achieved by using a suitably designed synthetic gene under the control of the T7 promoter. The protein produced in bacteria was extracted and easily purified in a good yield of 27 mg/L. The purified product was physico-chemically identified as intact human parathyroid hormone from the results of amino acid analysis, N-terminal sequencing, and peptide mapping using fast atom bombardment mass spectrometry. In biological assays the purified product stimulated adenylate cyclase in vitro, promoted bone growth and increased the serum osteocalcin in rats to the same extent as the authentic hormone.

A novel procedure for the preparation of biologically active recombinant peptides using a cyanylation reaction

A cysteine specific cleavage reaction was used for the preparation of biologically active peptides from recombinant fusion proteins. The fusion protein through cysteine was prepared by a recombinant DNA technology and then treated with cyanylating reagents such as 2-nitro-5-thiocyanatobenzoic acid (NTCB) and 1-cyano-4-(dimethylamino) pyridinium tetrafluoroborate (DMAP-CN) to release the desired product. As an example, we have selected a glucagon-like peptide 1 (7-37) (termed insulinotropin). We constructed an expression vector for a fusion protein in which insulinotropin and human basic fibroblast growth factor (hbFGF) mutein (abbreviated as CS 23) are connected by cysteine and then expressed it in Escherichia coli cells. The fusion protein, after refolding, was purified by heparin affinity chromatography, since CS23 has a strong affinity for heparin. The affinity-purified fusion protein was treated with NTCB or DMAP-CN to give crude insulinotropin, which was then purified by reversed phase (rp) high-performance liquid chromatography (HPLC). From various criteria such as amino acid analysis, amino acid sequence and the biological activity, the purified material obtained was found to be methionylated insulinotropin (Met-insulinotropin) with full activity. The specificity and simplicity of the present method make it versatile and convenient for the preparation of biologically active peptides.

Monoclonal antibodies against hst-1 gene product

Four monoclonal antibodies (MAbs) against the hst-1 gene product (hst-1 protein) were obtained by a somatic cell hybridization technique. The recognition sites of these MAbs designated HS-131, HS-210, HS-233 and HS-276 on the hst-1 protein were evaluated by competitive binding assay with synthetic polypeptides. HS-131 MAb and HS-276 MAb recognize the epitope located within the 59-73 and the 197-206 amino acid sequences, respectively. The epitopes recognized by HS-210 and HS-233 MAbs could not be determined, but these MAbs showed neutralizing activity against hst-1 protein. Using HS-131 and HS-233 MAbs, a sensitive sandwich enzyme immunoassay (sandwich EIA) has been developed. The assay sensitivity was 1.2-2.5 pg/well of hst-1 protein. Acidic and basic fibroblast growth factors were not cross-reactive up to a concentration of 1 microgram/ml.

In vivo stimulation of endosteal bone formation by basic fibroblast growth factor in rats

Intravenous administration of human basic fibroblast growth factor (bFGF) for 2 weeks stimulated osteoblast proliferation and new bone formation in various skeletal bones in young and aged rats at dosage levels of 0.1 mg/kg/day and greater. Morphometry of the soft X-ray radiograms of cross sections of the tibia indicated about a 20% increase in the calcified bone area of the diaphysis at 0.1 mg/kg/day. The Ca and hydroxyproline contents showed statistically significant increases at this dosage. The new bone formation was found only on the endosteal side, and no periosteal bone formation was found. Similar systemic osteogenic potential was seen after intravenous administration of other growth factors of the FGF family, human acidic FGF and human heparin-binding secretory transforming protein-1. The above results suggest a potential therapeutic role for these growth factors in bone-loss diseases such as osteoporosis.

Endothelial cell chemotactic factor derived from human glioma cell lines

✓ The authors report a study of the human umbilical vein endothelial cell chemotactic factor derived from human malignant glioma cell lines. The endothelial cell chemotactic activity of serum-free conditioned medium from cultures of U-373MG, U-251MG, or U-105MG cell lines was measured using a 48-well microchemotaxis chamber. The best response was from U-373MG, which was selected for further study. Chemotactic activity was contained in materials unadsorbed and adsorbed to the heparin-affinity column. Because the higher activity was seen in the unadsorbed material, it was used for characterization and partial isolation. The chemotactic activity was decreased under the condition of tumor protein synthesis inhibition. Heating, exposure to acid, and trypsin digestion also decreased the activity. The factor was found to be a protein with a relative molecular weight of greater than 200 kD; it has no mitogenic activity for endothelial cells in vitro and, partially purified, it was not identical to any other known endothelial cell chemotactic or mitogenic factor. Fibronectin was not detected, and anti-fibronectin antibody failed to inhibit the activity of the factor. These results suggest that malignant glioma cells produce a yet unknown endothelial cell chemotactic factor.

Effects of acidic fibroblast growth factor on hippocampal long-term potentiation in fasted rats

Effects of human recombinant acidic fibroblast growth factor (haFGF) on long-term potentiation (LTP) and the increase of the spike amplitude induced by weak tetanic stimulation were investigated and compared with those of CS23 (modified human basic FGF) in the dentate gyrus of fasted and nonfasted rats. haFGF didn't influence the LTP induced by the tetanus of 100 pulses at 100 Hz in both 24 hr fasted and non-fasted rats. On the other hand, the tetanus of 20 pulses at 60 Hz significantly enhanced the amplitude of population spike and facilitated the generation of LTP by the i.c.v. injection of 10 microliters of 20-40 micrograms/ml haFGF in 24 hr fasted rats but not in non-fasted rats. However, 40 micrograms/ml CS23 induced LTP when the tetanus of 20 pulses at 60 Hz was applied in both fasted and non-fasted states. These results suggest that haFGF might be one of the regulating factors of feeding and memory.

Expression of human T-cell leukemia virus type I protease in Escherichia coli

Human T-cell leukemia virus type I (HTLV-I) genome is believed to encode its own protease, although the protease has not yet been detected. To identify the HTLV-I protease, an in-frame gag (3' portion)-prt region was expressed in Escherichia coli. The 14-kDa product was detected using antisera against a synthetic peptide mimicking the fragment of HTLV-I protease, although the molecular weight of the primary translational product was 27,000. A cell extract had a proteolytic activity to cleave a synthetic peptide substrate containing the cleavage site of gag p19/p24 at the correct site in vitro. Replacement of the putative active site Asp-64 with Gly abolished both in vivo processing activity and in vitro proteolytic activity. These results suggest that the 14-kDa product is the mature enzymatically active HTLV-I protease generated through posttranslational autoprocessing in E. coli.

Differential expression in Escherichia coli of the alpha and beta forms of heparin-binding acidic fibroblast growth factor-1: potential role of RNA secondary structure

Synthetic DNA fragments encoding the entire open-reading frame of human heparin-binding growth factor-1 (HBGF-1 beta) and its NH2-terminal truncated form (HBGF-1 alpha) were constructed. When both constructs were expressed in Escherichia coli under control of the trp-lac promoter, biologically active HBGF-1 alpha, but not HBGF-1 beta was produced in high yield. However, high level expression of HBGF-1 beta was obtained using the T7 polymerase expression vector. Computer analysis of HBGF-1 beta predicts the potential for the formation of exaggerated RNA secondary structure near the translation initiation codon and this could be implicated in contributing to the poor translation of HBGF-1 beta under the trp-lac promoter.

Characterization of high-molecular-mass forms of basic fibroblast growth factor produced by hepatocellular carcinoma cells: possible involvement of basic fibroblast growth factor in hepatocarcinogenesis

Growth factor(s) with a strong mitogenic effect on BALB/c3T3 cells was purified from an extract of C-Li21 cells, a human hepatocellular carcinoma line, by a combination of heparin-affinity chromatography and reversed-phase high-performance liquid chromatography (HPLC). Two major peaks of mitogenic activity were obtained by reversed-phase HPLC. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the two peaks revealed that one was composed of three proteins with relative molecular masses of 27, 24 and 23 kilodaltons (kD), whereas the other was a single 19-kD protein. Immunoblot analysis showed that all four of these molecules were immunoreactive species of human basic fibroblast growth factor (bFGF). N-Terminal sequence analysis of these molecules revealed that most of them were N-terminally blocked. However, small proportions of the 23- and 19-kD molecules were not blocked, and their respective N-terminal sequences were found to correspond to Gly-40-Gly-27 and Pro29-Phe40 of human bFGF deduced from the cDNA sequence of a human hepatoma cell line, SK-HEP-1. Expression of bFGF in hepatocellular carcinomas was then investigated by RNA blot analysis. All of the examined hepatocellular carcinoma cells expressed bFGF, and the degree of expression was higher in surgically resected hepatocellular carcinomas than in the corresponding adjacent non-cancerous liver tissue. Transcripts of bFGF were not detected in normal liver. These results suggest that C-Li21 cells produce four molecular forms of bFGF, and that bFGF may be involved in hepatocarcinogenesis. Moreover, it appears that bFGF is a potent mitogen toward primary-cultured hepatocytes, and that high-molecular-mass forms of bFGF produced by C-Li21 cells have stronger mitogenic effects on hepatocytes and are more stable under acidic conditions than the low-molecular-mass form, composed of 146 amino acids.

Establishment of monoclonal antibodies against human acidic fibroblast growth factor

Four kinds of hybridomas secreting monoclonal antibodies (MAbs) against human acidic fibroblast growth factor (haFGF) were established using recombinant haFGF as an immunogen. The recognition sites of four MAbs designated AF1-52, 81, 114 and 1C10 for the haFGF molecule were examined by binding studies with synthetic polypeptides and with amino-terminal truncated forms of haFGF. These experiments suggested that AF1-52, 114, and 1C10 MAbs recognize epitopes within the 1-5, 44-132 and 6-43 amino acid sequences, respectively. However, the epitope recognized by the AF1-81 MAb could not be determined. The sandwich EIA method constructed with these MAbs was sensitive to 1.5 pg/well of haFGF and had no cross-reactivity with human basic FGF, bovine aFGF or the hst-1 gene product.

A sensitive enzyme immunoassay for human basic fibroblast growth factor

A sensitive sandwich enzyme immunoassay for human basic fibroblast growth factor (HbFGF) was developed employing three monoclonal antibodies (MAb3H3, MAb98 and MAb52). The Fab' fragment of MAb3H3 which inhibits HbFGF biological activity was conjugated to horseradish peroxidase. A mixture of MAb52 and MAb98 was used in the solid phase. Neither human acidic fibroblast growth factor, hst-1/KS3 product nor acid denatured HbFGF was cross-reactive in this assay system. The detection limit of this assay system was 1 pg/well. Using this assay, some tumor cell lines were revealed to produce a higher level of bFGF than a normal one. Serum samples from normal volunteers were also assayed, and immuno-reactive HbFGF could be detected in 16 out of 57 samples at range 30 approximately 206 pg/ml.