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Biomedical subjects

E M Gordon

Publications and source records attributed to E M Gordon.

At least 55 records · Page 3Linked to original sources
PubMed1996

Hydroxamic acid-based bisubstrate analog inhibitors of Ras farnesyl protein transferase.

The rational design, synthesis, and activity of novel, hydroxamic acid-based, collective bisubstrate analog inhibitors of farnesyl protein transferase (FPT) is described. This class of compounds differ structurally from the conventional FPT inhibitors by being non-sulfhydryl and by being bisubstrate based rather than peptide or FPP derived inhibitors. Whereas replacement of the sulfhydryl group of tetrapeptide CVLS (I50 = 1 microM) by an N-methylhydroxamic acid had a deleterious effect (10, I50 > 360 microM), moderate inhibition was realized with 16 (I50 = 42.5 microM), a bisubstrate analog involving anchorage of farnesyl and tripeptide groups by a hydroxamic acid-embedded linker. Starting from 16, a 1 order of magnitude improvement in in vitro potency was obtained by optimization of the linker (20, I50 = 4.35 microM). An additional 13-fold enhancement was achieved by substituting the tripeptide moiety VLS in 20 by VVM (23, I50 = 0.33 microM). The dependence of these inhibitors on their peptide and farnesyl subunits is suggestive of their bisubstrate nature. Compound 23 (I50 = 0.33 microM) is 2 orders of magnitude better in activity compared to the initial lead 16 [I50 = 42.5 microM) and is effective in blocking prenylation of protein in whole cells including p21ras.

3T3 Cells↗
PubMed1996

Retrovirus-mediated suicide gene transduction in the vitreous cavity of the eye: feasibility in prevention of proliferative vitreoretinopathy.

In proliferative vitreoretinopathy (PVR), retinal pigment epithelial cells, fibroblasts, or other proliferating cells form contractile membranes in the vitreous cavity of the eye, resulting in traction retinal detachment. Retroviral vector-mediated transfer is a suitable method to transduce the herpes simplex virus thymidine kinase (HSV-tk) gene into proliferating cells in PVR, allowing for the selective killing of these cells. To determine the potential of gene transduction in the environment of the vitreous cavity, we evaluated the effect of vitreous humor on retroviral vector-mediated gene transduction of rabbit dermal fibroblasts in vitro and studied in vivo transduction in rabbit experimental PVR with retroviral vector G1BgSvNa. In addition, we studied the bystander effect in vitro and in vivo in a rabbit model of PVR, with low percentages of HSV-tk-positive cells. Finally, we evaluated the efficacy of intravitreal administration of HSV-tk retroviral vector G1TkSvNa followed by ganciclovir (GCV) in the prevention of experimental PVR. Vitreous humor reduced gene transfer efficiency in vitro in a dose-dependent manner. LacZ expression was found in cells of preretinal or intravitreal membranes of animals of both in vivo and in vitro transduction groups; however, in vivo transduction resulted in a decreased number of transduced cells, with a relative transduction efficiency of approximately 2%. Transduction of HSV-tk was associated with a powerful bystander effect both in vitro and in vivo with significant effects even when HSV-tk-positive cells represented only 1% of the population. In vivo transduction with G1TkSvNa followed by GCV significantly inhibited the development of PVR (p < 0.05). These results suggest that retroviral vector-mediated transfer of HSV-tk into the proliferating cells in PVR may be feasible and may provide a novel therapeutic strategy for this disease.

Animals↗
PubMed1996

Versatile approach to encoding combinatorial organic syntheses using chemically robust secondary amine tags.

Encoded combinatorial organic synthesis has recently emerged as a powerful tool for the discovery of biologically active compounds from complex chemical libraries. This report describes a new encoding methodology that uses chemically robust secondary amines as tags. These amines are incorporated into an N-[(dialkylcarbamoyl)methyl]glycine-coding oligomer through simple chemistry that is compatible with a wide range of polymer-supported transformations useful in combinatorial synthesis. In the decoding process acidic hydrolysis of the tagging polymer regenerates the secondary amines, which after dansylation are resolved and detected at sub-picomole levels by reversed-phase HPLC. The versatility of this strategy is demonstrated here by encoded syntheses of members of several representative heterocyclic compound classes, including beta-lactams, 4-thiazolidinones, and pyrrolidines.

Anti-Bacterial Agents↗
PubMed1996

Factor XII-induced mitogenesis is mediated via a distinct signal transduction pathway that activates a mitogen-activated protein kinase.

Clotting factor XII (Hageman factor) contains epidermal growth factor (EGF)-homologous domains and is reported to be a potent mitogen for human hepatoma (HepG2) cells. In this study, we tested whether factor XII exhibits growth factor activity on several other EGF-sensitive target cells, including fetal hepatocytes, endothelial cells, alveolar type II cells, and aortic smooth muscle cells. We found that factor XII significantly enhanced [3H]thymidine incorporation in aortic smooth muscle cells (SMCs) and all other cells tested. Tyrphostin, a growth factor receptor/tyrosine kinase antagonist, inhibited both EGF- and factor XII-induced responses. However, differences in the levels of magnitude of DNA synthesis, the observed synergism between EGF and factor XII, and the differential sensitivity to tyrphostin suggest that the EGF receptor and the factor XII receptor may be nonidentical. The factor XII-induced mitogenic response was achieved at concentrations that were 1/10th the physiologic range for the circulating factor and was reduced by popcorn inhibitor, a specific factor XII protease inhibitor. Treatment of aortic SMCs with factor XII, as well as activated factor XII, resulted in a rapid and transient activation of a mitogen-activated/extracellular signal-regulated protein kinase with peak activity/tyrosine phosphorylation observed at 5 to 10 min of exposure. Taken together, these data (i) confirm that clotting factor XII functions as a mitogenic growth factor and (ii) demonstrate that factor XII activates a signal transduction pathway, which includes a mitogen-activated protein kinase.

Animals↗
PubMed1996

Combinatorial modification of natural products: preparation of unencoded and encoded libraries of Rauwolfia alkaloids.

We report the preparation of combinatorial libraries which consist of derivatives of the stereoisomeric alkaloids yohimbine and rauwolscine-members of the Rauwolfia genus. The chemistry was performed on solid support using the divide-and-pool method, and involved the derivatization of the E-ring carboxylates and hydroxyls of these alkaloids with 36 amino acids and 22 carboxylic acids, respectively, to afford 792 bifunctionalized derivatives. The rauwolscine library was prepared using an encoding strategy in which the identity of each incorporated amino acid was recorded by cosynthesizing chemically inert tags prior to the pooling step. The general strategy for library synthesis exploits existing functionality present on the natural products, and should be applicable to other families of secondary metabolites.

Chromatography, High Pressure Liquid↗
PubMed1996

Gene therapy of metastatic pancreas cancer with intraperitoneal injections of concentrated retroviral herpes simplex thymidine kinase vector supernatant and ganciclovir.

OBJECTIVE: The objective of this study was to determine the efficacy of intraperitoneal (IP) injections of a new concentrated herpes simplex thymidine kinase (HS-tk) retroviral vector and ganciclovir (GCV) for peritoneal metastases from pancreas cancer. SUMMARY BACKGROUND DATA: Metastatic pancreas cancer is fatal. Gene therapy may provide a novel approach for this disease. Gene therapy with adeno- or retroviral-mediated transfer of the HS-tk gene into tumor cells renders the cells susceptible to GCV. Intratumoral or intracavity injections of retroviral vectors have been ineffective in previous studies. METHODS: Pancreatic cancer B x PC3 cells (3 x 10(7)) were injected into the tail of pancreas in nude mice. Mice received IP injections of a concentrated HS-tk vector (5 x 10(7)) cfu/mliters) or a control vector (G1Na) without the tk gene for 10 days and GCV (100 mg/kg) for 14 days. To determine whether the vector would survive in the milieu of the peritoneal cavity, the authors examined the effects of ascitic fluid on the vector. Pancreas cancer cells were transduced in vitro with HS-tk vector in presence of media or ascitic fluid and treated with GCV. RESULTS: Highly significant reductions in the mass of metastatic peritoneal tumor deposits were found in HS-tk-treated group (124 +/- 27 mg; n = 11) compared with G1Na vector controls (910 +/- 168 mg; n = 8; p < 0.0001). Results of polymerase chain reaction analysis demonstrated integration of the vector in the tumors, and on immunohistochemistry, expression of the TK protein was seen in the number of surviving colonies (representing nontransduced cells) were similar in both groups, suggesting that the vector effectively transduced tumor cells bathed in the ascitic fluid. CONCLUSIONS: Results demonstrate that IP administration of concentrated retroviral HS-tk vectors is effective treatment for pancreas cancer metastatic to the peritoneal cavity; furthermore, the vector is active in the presence of ascitic fluid. Intraperitoneal retroviral HS-tk may provide a novel approach to treatment of metastatic pancreas cancer.

Animals↗
PubMed1995

Retroviral vector-mediated gene transfer of antisense cyclin G1 (CYCG1) inhibits proliferation of human osteogenic sarcoma cells.

Genetic changes found in human osteogenic sarcoma cells, including loss of the p53 and Rb tumor suppressor elements and overexpression of the cyclin G1 (CYCG1) proto-oncogene, suggest the potential of gene transfer as a treatment for metastatic disease. In this study, we examined the effects of antisense cyclin G1, in comparison with antisense cyclin D1 (CYCD1) and enforced expression of the universal cyclin-dependent kinase inhibitor p21WAF1/CIP1 on the proliferation of human MG-63 osteosarcoma cells. Retroviral vectors bearing antisense CYCG1 as well as antisense CYCD1 and WAF1/CIP1 (in sense orientation) driven by the Moloney murine leukemia virus long terminal repeat promoter inhibited the growth and/or survival of transduced MG-63 cells in 2-7 day cultures. This represents the first demonstration that cyclin G1 is essential for the survival and/or growth of human osteosarcoma cells. Cytostatic and cytopathic effects were accompanied by a significant increase in the incidence of apoptosis, as determined by immunocytochemical analysis of DNA fragmentation. Furthermore, transduction of MG-63 cells with a retroviral vector bearing the suicide gene, herpes simplex thymidine kinase (HStk), induced cell death on treatment with ganciclovir, exhibiting pronounced bystander effects. Taken together, the data affirm the feasibility of modulating inducible cell cycle control enzymes as a potential gene therapy approach in the clinical management of osteogenic sarcoma.

Apoptosis↗
PubMed1995

Farnesyl diphosphate-based inhibitors of Ras farnesyl protein transferase.

The rational design, synthesis, and biological activity of farnesyl diphosphate (FPP)-based inhibitors of the enzyme Ras farnesyl protein transferase (FPT) is described. Compound 3, wherein a beta-carboxylic phosphonic acid type pyrophosphate (PP) surrogate is connected to the hydrophobic farnesyl group by an amide linker, was found to be a potent (I50(FPT) = 75 nM) and selective inhibitor of FPT, as evidenced by its inferior activity against squalene synthetase (I50(SS) = 516 microM) and mevalonate kinase (I50(MK) = > 200 microM). A systematic structure-activity relationship study involving modifications of the farnesyl group, the amide linker, and the PP surrogate of 3 was undertaken. Both the carboxylic and phosphonic acid groups of the beta-carboxylic phosphonic acid PP surrogate are essential for activity, since deletion of either group results in 50-2600-fold loss in activity (6-9, I50 = 4.6-220 microM). The farnesyl group also displays very stringent requirements and does not tolerate one carbon homologation (12, I50 = 17.7 microM), substitution by a dodecyl fragment (14, I50 = 9 microM), or introduction of an extra methyl group at the allylic position (18, I50 = 55 microM). Modifications around the amide linker group of 3 were more forgiving, as evidenced by the activity of N-methyl analog (21, I50 = 0.53 microM), the one carbon atom shorter farnesoic acid-derived retroamide analog (32, I50 = 250 nM), and the exact retroamide analog (49, I50 = 50 nM). FPP analogs such as 3, 32, and 49 are novel, potent, selective, small-sized, nonpeptidic inhibitors of FPT that may find utility as antitumor agents.

Alkyl and Aryl Transferases↗
PubMed1995

Phosphinyl acid-based bisubstrate analog inhibitors of Ras farnesyl protein transferase.

The rational design, synthesis, and biological activity of phosphonyl- and phosphinyl-linked bisubstrate analog inhibitors of the enzyme Ras farnesyl protein transferase (FPT) are described. The design strategy for these bisubstrate inhibitors involved connection of the critical binding components of the two substrates of FPT (ras protein and farnesyl pyrophosphate, FPP) through a phosphonyl- or phosphinyl-bearing linker. Compound 14, the first example in this series, was found to be a potent FPT inhibitor (I50 = 60 nM). A further 15-fold enhancement in activity was observed upon replacement of the VLS tripeptide sequence in 14 with VVM (15, I50 = 6 nM). The phosphinic acid analog 16 (I50 = 6 nM) was equiactive to phosphonic acid 15. Compounds 14-16 afforded 1000-fold selectivity for FPT against the closely related enzyme geranylgeranyl protein transferase type I, GGT-I [14, I50(GGT-I) = 59 microM; 15 I50(GGT-I) = 10 microM; 16 I50(GGT-I) = 21 microM]. Methyl and POM ester prodrugs 17-19 were prepared and evaluated in whole cell assays and appear to block ras-induced cell transformation, as well as colony formation in soft agar. A distinctive feature of this novel class of potent and selective bisubstrate FPT inhibitors is that they are non-sulfhydryl in nature.

3T3 Cells↗
PubMed1995

Heterozygous protein C deficiency presenting as severe protein C deficiency and peripartum thrombosis: successful treatment with protein C concentrate.

BACKGROUND: Complications of pregnancy, including thrombosis and increased fetal loss, have been described in women with heterozygous protein C deficiency. CASE: We report an unusual case of umbilical cord thrombosis, acute renal failure, and cutaneous venous thrombosis associated with severe protein C deficiency in the heterozygous infant of a normal mother. Repeated infusions of protein C concentrate made successful heparinization of the infant possible, with the subsequent resolution of cutaneous thrombosis and improvement of renal status. CONCLUSION: Heterozygous protein C deficiency in the fetus may result in perinatal thrombosis, which can be treated with viral-inactivated protein C concentrate. Heterozygous protein C deficiency should be considered in cases of fetal compromise or death associated with umbilical vein thrombosis.

Adult↗
PubMed1995

Inhibition of experimental proliferative vitreoretinopathy by retroviral vector-mediated transfer of suicide gene. Can proliferative vitreoretinopathy be a target of gene therapy?

PURPOSE: To determine the potential of somatic gene transfer as a treatment for proliferative vitreoretinopathy (PVR), experimental PVR was induced in rabbits by intraocular injection of fibroblasts bearing the herpes simplex virus thymidine kinase (HStk) gene. These transduced cells should be susceptible to cytotoxicity by exposure to ganciclovir (GCV). MATERIALS AND METHODS: Rabbit fibroblasts were transduced with retroviral vectors bearing an HStk gene. Proliferative vitreoretinopathy was induced by injection of 5 x 10(4) normal or HStk gene-transduced fibroblasts (HStk fibroblasts) into rabbit eyes. Ganciclovir (100 micrograms per eye) or saline was injected into the vitreous on days 0 and 4. Experimental animals were divided into three groups: group A received HStk fibroblasts with GCV; group B, normal fibroblasts with GCV; group C, HStk fibroblasts with saline. Proliferative vitreoretinopathy also was induced in several other groups of eyes, some receiving GCV and different proportions of HStk fibroblasts to normal fibroblasts, others receiving only normal fibroblasts and GCV. The eyes were examined by indirect ophthalmoscopy on days 4, 7, 14, and 28, and PVR was classified into six stages (0-5). RESULTS: Proliferative vitreoretinopathy was induced and progressed over time in each group. On day 28, PVR was most severe in animals in group B (average stage, 4.6) and group C (average stage, 4.4). Proliferative vitreoretinopathy was inhibited in group A (average stage, 1.0). The groups that received mixed injection of HStk fibroblasts and normal fibroblasts had intermediate PVR. Results of histologic study showed no apparent toxic or pathologic reaction in the retinochoroidal tissue of group A animals. CONCLUSIONS: Severity of experimental PVR clearly was reduced by transfer of the HStk gene and administration of GCV. This inhibitory effect also was produced by a combination of 10% HStk fibroblasts and 90% normal fibroblasts, indicating a significant bystander effect. These data suggest the potential of somatic gene therapy for the treatment of PVR.

Animals↗
PubMed1995

Expression of biologically active human factor IX in human hematopoietic cells after retroviral vector-mediated gene transduction.

Gene therapy is a potential treatment for hemophilia, wherein cells transduced with a normal factor IX gene could provide a continuous in vivo source of circulating factor IX. In this study, we examined the potential use of hematopoietic cells as a target for factor IX gene therapy. Human myeloid leukemia cells (HL-60) were transduced by retroviral vectors carrying a normal human factor IX cDNA under control of either the Moloney murine leukemia virus long terminal repeat (MoMuLV LTR) (LIXSN), the SV40 promoter (LNSVIX), or a cytomegalovirus (CMV) promoter (LNCIX). Factor IX production was measured in the transduced cells both in the uninduced state and after induction of granulocytic differentiation [with dimethylsulfoxide (DMSO)] or monocytoid differentiation [with phorbol myristic acetate (PMA)]. Transcription of factor IX from the MoMuLV LTR was seen in all cells, with a two-fold increase upon differentiation. Induction with PMA led to an 8- to 15-fold increase in factor IX transcripts from an internal CMV promoter. No factor IX transcripts from the internal SV40 promoter were detected. Immunoreactive factor IX protein was identified by Western blot from induced HL-60 cells transduced by either LIXSN or LNCIX. Factor IX production by HL-60 cells transduced by LNCIX ranged from 38-93 ng/10(6) cells/24 hr following induction of monocytic differentiation. The factor IX antigen titer was directly related to factor IX coagulant titer (r = 0.98; p < 0.001). These data indicate that human myelomonocytic cells are capable of performing the necessary post-translational modifications to produce functional factor IX.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Northern↗
PubMed1995

Superficial bladder cancer: for how long should a tumour-free patient have check cystoscopies?

OBJECTIVE: To determine the probability of a patient with superficial bladder cancer developing a recurrent tumour after having remained tumour free for 2 or more years. PATIENTS AND METHODS: One-hundred and seventy-nine patients with Ta or T1 tumours at diagnosis, a minimum follow-up of 3 years and a minimum of 2 years remaining tumour free were identified. Thirteen patients had more than one episode that was eligible for inclusion and there were therefore 192 tumour-free episodes for analysis. Survival curves of the probability of being recurrence-free against time were constructed for the whole group, for subgroups of Ta and T1 tumours and for subgroups with characteristics at diagnosis suggesting a good, intermediate and poor prognosis. RESULTS: The probability of a patient developing a recurrence after 2, 5 and 10 years of being tumour free was 43, 22 and 2% respectively. No patient had a recurrence after remaining tumour free for 12 years. No patient who had been tumour free for at least 2 years progressed to muscle invasion or metastases. There was no significant difference in the probability of recurrence between Ta and T1 tumours after 2 years of remaining tumour free. CONCLUSION: The optimum length of cystoscopic follow-up for patients with superficial bladder cancer is unknown, but patients continue to develop recurrences even after many years of being tumour free. If a patient is to discontinue cystoscopic follow-up, then alternative methods of assessment should be applied.

Adult↗
PubMed1995

Should all patients with ureteric colic be admitted?

A two-part study was undertaken to determine if all patients with uncomplicated ureteric colic require admission. The analgesic requirements and outcome in 31 patients admitted with ureteric colic were assessed; 20/31 (64%) required no further analgesia after admission and 8/31 (26%) required only oral/rectal analgesia. In the second part of the study a protocol was introduced allowing patients with no complicating factors to be discharged directly from the A&E department. Of 58 patients seen in the A&E department, 29 were discharged for outpatient follow-up. Of these patients, 19 required no additional acute hospital treatment, five returned for further parenteral analgesia but outside the time they would have stayed in hospital under our previous protocol (ie beyond 48 h) and three returned within 48 h of their first attendance with pain which had not responded to oral analgesics. No patient discharged from A&E subsequently required intervention for obstruction or infection. We conclude that it is not necessary to admit patients with uncomplicated ureteric colic if the initial colic has been relieved and there is adequate social support.

Adult↗
PubMed1994

A multicenter study of recombinant factor VIII (recombinate): safety, efficacy, and inhibitor risk in previously untreated patients with hemophilia A. The Recombinate Study Group.

In July 1990, the Recombinate Study Group initiated a prospective, open-labeled investigation of recombinant factor VIII (r-FVIII) to assess its safety and efficacy and to characterize the natural history of inhibitor development in previously untreated patients (PUPs) with hemophilia A. All study subjects have severe FVIII deficiency (baseline FVIII level < or = 2% of normal) and no history of blood product exposure before study entry. Following the first r-FVIII infusion, plasma was screened for inhibitors once every 3 months, and plasma recovery of r-FVIII at 30 minutes and 24 hours postinfusion was assayed at least once every 6 months. As of May 1993, 73 of 79 patients originally enrolled in the trial continue to participate. The median number of r-FVIII exposure-days for the 71 subjects who have received at least one r-FVIII infusion is 11. A total of 1,785 infusions have been administered to treat 810 bleeding events. Ninety-two percent of bleeding events responded as anticipated to one or two infusions. Two, nonrecurring, acute adverse reactions occurred coincident with r-FVIII infusion, one of which was unrelated and the other, possibly related to the infusion. Seventeen (23.9%) subjects have developed inhibitors: five with peak titers more than 10 Bethesda units (BU) and 12 with peak titers < or = 10 BU (range, 0.5 to 10). Survival analysis showed that the probability of remaining inhibitor-free in this group of patients with severe hemophilia A is 88.4% after 8, 73.6% after 10, and 61.6% after 25 r-FVIII exposure-days. Inhibitors disappeared in five (29.4%) subjects on retesting 2 to 16 months after the last positive inhibitor assay. r-FVIII is safe and effective in the treatment of hemophilia A-related bleeding. To date, the inhibitor risk associated with its use is comparable to that in patients treated with plasma-derived concentrates. The majority of inhibitors identified are low in titer and do not preclude continued on-demand therapy with r-FVIII.

Antibodies↗
PubMed1994

Continuous infusion of monoclonal antibody-purified factor VIII: rational approach to serious hemorrhage in patients with allo-/autoantibodies to factor VIII.

Hemorrhage in a patient with factor VIII inhibitor is associated with increased morbidity and mortality. Treatment with factor IX complex concentrates or recombinant factor VIIa (rVIIa) may not control bleeding and may induce thrombosis. In this study, continuous infusion of a monoclonal antibody-purified factor VIII [correction of factor VII] concentrate (Monoclate-P) was used successfully in two hemophilic patients with factor VIII alloantibodies and one nonhemophilic patient with a factor VIII autoantibody. In two patients, hemorrhage was life-threatening, and, in one, bleeding did not stop with repeated infusions of activated factor IX complex concentrates. The patients' ages ranged from 4 to 15 years, and the inhibitor levels from 6 to 300 Bethesda units/ml. Clinical hemostasis was excellent, and in vivo recovery of infused factor VIII was achieved. When an excess of monoclonal factor VIII was added to the inhibitor plasma in vitro, a stable level of residual factor VIII activity was noted after an initial rapid loss. This second-order reaction occurs in plasmas of patients with type I factor VIII inhibitors. In one patient, we showed that the saturation dose of the factor VIII inhibitor predicted in vivo recovery of factor VIII:C. These data emphasize the importance of characterizing the kinetic reactions of the factor VIII inhibitor. Furthermore, we confirm previous reports that continuous infusion of monoclonal factor VIII is a safe and effective treatment of patients with factor VIII inhibitors in whom hemorrhage is either life-threatening or refractory to standard treatment.

Adolescent↗