Additive Effects of Leflunomide and Tacrolimus in Prevention of Islet Xenograft Rejection

Leflunomide is a low molecular weight immunosuppressive drug which inhibits the enzymes dehydroorotate dehydrogenase and protein tyrosine kinase, both of which are important components in the immune response. As the mechanisms of action of leflunomide and tacrolimus are different, we postulated an additive or synergistic effect of the two drugs and investigated the effects of leflunomide alone, or in combination with a suboptimal dose of tacrolimus, on xenogeneic islet transplantation in a rat-to-mouse model. A total of 1200-1500 rat islets were transplanted under the left kidney capsule of streptozotocin-induced diabetic BALB/c mice. The median survival time (MST) of the untreated group was 6 days. Leflunomide at 5, 10 and 20 mg/kg/d administrated for 10 days significantly prolonged MST to 10, 16 and 20 days. A dose of tacrolimus (2 mg/kg/d) was associated with a graft survival of 9 (range 6-12) days; most grafts rejected during ongoing therapy. When tacrolimus (2 mg/kg/d) was combined with leflunomide (10 mg/kg/d), the survival time of the islet xenografts was increased further to 22 days, significantly longer than with leflunomide or tacrolimus alone. In summary, our findings demonstrate that leflunomide prolonged xenogeneic islet graft survival, and that its immunosuppressive effect was improved when combined with tacrolimus.

Intravital fluorescence facilitates measurement of multiple physiologic functions and gene expression in tumors of live animals

The purpose of this report is to present an overview of the use of fluorescence imaging in vivo, with particular emphasis on oncology. It is important to note, however, that many of the methods described herein have been applied to the study of non-malignant tissues as well. Modern medicine and biology research has benefited greatly from an ever-expanding assortment of fluorescent markers and labels. These markers and labels have allowed investigators to observe the behavior and properties of cell and molecular entities of interest in the context of complicated biological systems such as a mammalian cell or a whole mouse. Methods developed to image fluorescence in whole mice have been valuable in studying patterns of tumor growth and metastases. Alternatively, more detailed information and a wide variety of endpoints can be obtained using "intravital" preparations. This review focuses on use of fluorescence imaging for intravital preparations. For detail on fluorescence imaging of whole animals, refer to reviews on this subject [1,2]. For oncologic applications, studies have focused primarily on window chamber preparations that allow for real-time visualization of tumor growth, vascularity, vascular responses to stimulation, vascular permeability, vascular orientation, flow instability, and the like. These endpoints have been used to show that there are functional differences between tumor and normal tissues with respect to these functions under baseline conditions and after therapeutic manipulation. Examples of some of these differences are provided in this review as a means to illustrate how they can be used.

Enzyme-linked immunosorbent assay for glycyrrhizin using anti-glycyrrhizin monoclonal antibody and an eastern blotting technique for glucuronides of glycyrrhetic acid

Hybridomas secreting a monoclonal antibody against glycyrrhizin were produced by fusing splenocytes from a mouse immunized against a glycyrrhizin-bovine serum albumin conjugate with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma cell line, P3-X63-Ag8-653. A very weak cross-reaction with glycyrrhetinic acid monoglucuronide and glycyrrhetic acid occurred. An enzyme-linked immunosorbent assay (ELISA) that had an effective measuring range of 20 -200 ng/mL of glycyrrhizin was established using this monoclonal antibody. In addition, a method named eastern blotting for the detection of glycyrrhizin was investigated. In this method, we developed a new way to separate the glycyrrhizin molecule into two functional parts using a simple and well-known chemical reaction. The sugar parts were oxidized by sodium periodate to give dialdehydes, which reacted with amino groups on the protein and covalently bound to the adsorbent membrane. The monoclonal antibody bound to the aglycone part of the glycyrrhizin molecule for immunostaining. This method was validated by immunocytolocalization of glycyrrhizin in fresh Glycyrrhiza root.

Mechanisms associated with tumor vascular shut-down induced by combretastatin A-4 phosphate: intravital microscopy and measurement of vascular permeability

The tumor vascular effects of the tubulin destabilizing agent disodium combretastatinA-4 3-O-phosphate (CA-4-P) were investigated in the rat P22 tumor growing in a dorsal skin flap window chamber implanted into BD9 rats. CA-4-P is in clinical trial as a tumor vascular targeting agent. In animal tumors, it can cause the shut-down of blood flow, leading to extensive tumor cell necrosis. However, the mechanisms leading to vascular shut-down are still unknown. Tumor vascular effects were visualized and monitored on-line before and after the administration of two doses of CA-4-P (30 and 100 mg/kg) using intravital microscopy. The combined effect of CA-4-P and systemic nitric oxide synthase (NOS) inhibition using N(omega)-nitro-L-arginine (L-NNA) was also assessed, because this combination has been shown previously to have a potentiating effect. The early effect of CA-4-P on tumor vascular permeability to albumin was determined to assess whether this could be involved in the mechanism of action of the drug. Tumor blood flow reduction was extremely rapid after CA-4-P treatment, with red cell velocity decreasing throughout the observation period and dropping to <5% of the starting value by 1 h. NOS inhibition alone caused a 50% decrease in red cell velocity, and the combined treatment of CA-4-P and NOS inhibition was approximately additive. The mechanism of blood flow reduction was very different for NOS inhibition and CA-4-P. That of NOS inhibition could be explained by a decrease in vessel diameter, which was most profound on the arteriolar side of the tumor circulation. In contrast, the effects of CA-4-P resembled an acute inflammatory reaction resulting in a visible loss of a large proportion of the smallest blood vessels. There was some return of visible vasculature at 1 h after treatment, but the blood in these vessels was static or nearly so, and many of the vessels were distended. The hematocrit within larger draining tumor venules tended to increase at early times after CA-4-P, suggesting fluid loss from the blood. The stacking of red cells to form rouleaux was also a common feature, coincident with slowing of blood flow; and these two factors would lead to an increase in viscous resistance to blood flow. Tumor vascular permeability to albumin was increased to approximately 160% of control values at 1 and 10 min after treatment. This could lead to an early decrease in tumor blood flow via an imbalance between intravascular and tissue pressures and/or an increase in blood viscosity as a result of increased hematocrit. These results suggest a mechanism of action of CA-4-P in vivo. Combination of CA-4-P with a NOS inhibitor has an additive effect, which it may be possible to exploit therapeutically.

The novel tubulin-binding drug BTO-956 inhibits R3230AC mammary carcinoma growth and angiogenesis in Fischer 344 rats

BTO-956 [methyl-3,5-diiodo-4-(4'-methoxyphenoxy)benzoate], a novel tubulin-binding drug and thyroid hormone analogue, was originally found to inhibit human carcinoma cell proliferation in vitro and to have potent growth delay activity in human breast and ovarian carcinoma xenografts in nude mice. Here we report that BTO-956 given to Fischer 344 rats also inhibits corneal angiogenesis and the growth and neovascularization of the R3230Ac rat mammary carcinoma tumor implanted in skin-fold window chambers. Hydron pellets containing recombinant human basic fibroblast growth factor (50 ng) and Sucralfate (20 microg) were implanted into surgically created corneal micropockets (day 0). BTO-956 was administrated by oral gavage (500 mg/kg, twice a day for 6 days) on days 1-6 (controls received vehicle alone). On day 7, rats received retrograde infusions of India ink via the thoracic aorta to visualize the corneal vasculature. Digitized images of slide-mounted corneas from control and treated animals were taken with a microscope. For the tumor growth and angiogenesis study, small pieces of R3230Ac tumor from a donor rat were implanted into surgically prepared window chambers (day 0). BTO-956 was given during days 5-11, and images of the tumors and their vasculature were recorded on day 12. No body weight loss was observed in either study. BTO-956 significantly inhibited corneal angiogenesis (by 50-80%), as assessed by measurements of limbal circumference displaying neovascularization, vessel length, vascularized area, and vascular area density. In the window chamber assay, tumors from treated animals were >50% smaller than tumors in control animals. In addition, vascular length densities in peripheral tumor zones were 30% less in treated compared with control animals. Together, these findings demonstrate that BTO-956 can inhibit angiogenesis induced by a growth factor in the rat cornea and in the peripheral area of implanted tumors, where tumor angiogenesis is most active.

Role of incipient angiogenesis in cancer metastasis

Metastasis is the primary cause of mortality in cancer patients. Angiogenesis is intimately involved in metastasis at the site of entry of tumor cells into the vasculature and at the site of eventual metastasis growth. In this commentary, we review current paradigms regarding angiogenesis in metastatic sites. Recent discoveries challenge some of the existing paradigms. Significant prior data suggest that successful formation of metastases requires: 1) angiogenesis in the primary tumor site; 2) downregulation of cohesive molecules and tumor cell increased motility, resulting in invasion into neovessels; 3) tumor cell embolism; 4) arrest and attachment in capillary beds of distant organs; 5) extravasation and proliferation in the organ parenchyma; and 6) re-establishment of angiogenesis when the tumor reaches > 1-2 mm in size [1]. While most recent data largely confirm the aforementioned sequence of events, a few reports have revealed new knowledge about the earliest phases of angiogenesis of metastases. Of particular importance has been the ability to create tumor cell lines that are stably transfected with reporter genes, such as green fluorescence protein. With these tools it is now literally possible to monitor tumor formation from a single cell [2-7].

Tamoxifen inhibits angiogenesis in estrogen receptor-negative animal models

Inhibition of tumor angiogenesis is a therapeutic strategy that can inhibit tumor growth and metastases. The aim of this study was to determine whether the estrogen receptor (ER) ligand drug tamoxifen has antiangiogenic effects. We used three different models of angiogenesis, including measurement of microvessel densities in murine tumors, ex vivo aortic ring assays, and corneal pocket assays. ER-negative fibrosarcoma tumors in tamoxifen-treated ovariectomized rats had significantly less vessel formation compared with untreated animals (median microvessel density, 53.6 versus 94.3 counts/per x 200 field; P = 0.002). Rat aortic rings treated with tamoxifen at several different concentrations demonstrated significantly less vascular sprouting than control rings (P = 0.0001). Corneal pocket assays performed in tamoxifen-treated rats compared with control and estrogen-treated rats demonstrated decreased vascular length (0.88 mm versus 1.26 mm versus 1.47 mm; P = 0.022) and vessel area (21% versus 34% versus 47%; P = 0.018). These three animal models all showed significant inhibition of angiogenesis by tamoxifen and suggest a possible contributory mechanism of ER-independent manipulation by tamoxifen in the treatment and prevention of breast cancer. These studies raise the question as to whether or not newer ER ligand drugs might possess even more potent antiangiogenic effects, which in turn could lead to the broadening of the clinical usefulness of these compounds in a number of diseases. More importantly, these studies suggest that the antiangiogenic effects of tamoxifen are due, in part, to ER-independent mechanisms.

Structure-based discovery of an organic compound that binds Bcl-2 protein and induces apoptosis of tumor cells

Bcl-2 and related proteins are key regulators of apoptosis or programmed cell death implicated in human disease including cancer. We recently showed that cell-permeable Bcl-2 binding peptides could induce apoptosis of human myeloid leukemia in vitro and suppress its growth in severe combined immunodeficient mice. Here we report the discovery of HA14-1, a small molecule (molecular weight = 409) and nonpeptidic ligand of a Bcl-2 surface pocket, by using a computer screening strategy based on the predicted structure of Bcl-2 protein. In vitro binding studies demonstrated the interaction of HA14-1 with this Bcl-2 surface pocket that is essential for Bcl-2 biological function. HA14-1 effectively induced apoptosis of human acute myeloid leukemia (HL-60) cells overexpressing Bcl-2 protein that was associated with the decrease in mitochondrial membrane potential and activation of caspase-9 followed by caspase-3. Cytokine response modifier A, a potent inhibitor of Fas-mediated apoptosis, did not block apoptosis induced by HA14-1. Whereas HA14-1 strongly induced the death of NIH 3T3 (Apaf-1(+/+)) cells, it had little apoptotic effect on Apaf-1-deficient (Apaf-1(-/-)) mouse embryonic fibroblast cells. These data are consistent with a mechanism by which HA14-1 induces the activation of Apaf-1 and caspases, possibly by binding to Bcl-2 protein and inhibiting its function. The discovery of this cell-permeable molecule provides a chemical probe to study Bcl-2-regulated apoptotic pathways in vivo and could lead to the development of new therapeutic agents.

Cell permeable Bcl-2 binding peptides: a chemical approach to apoptosis induction in tumor cells

Bcl-2 is a potent suppressor of apoptosis, and its overexpression contributes to tumorigenesis in many types of human cancers. To test the possibility of modulating Bcl-2 function as an anticancer strategy, a cell permeable Bcl-2 binding peptide, cell permeable moiety (cpm)-1285, was designed by chemically attaching a fatty acid to a peptide derived from the proapoptotic protein Bad. cpm-1285 entered HL-60 tumor cells, bound Bcl-2 protein, and induced apoptosis in vitro. In contrast, cpm-1285 had little effect on normal human peripheral blood lymphocytes. Furthermore, cpm-1285 had in vivo activity in slowing human myeloid leukemia growth in severe combined immunodeficient mice. These results demonstrate a novel approach for therapeutic intervention of tumor growth in vivo with small molecule inhibitors of Bcl-2.

Histochemical investigation of β-glucuronidase in culture cells and regenerated plants of Scutellaria baicalensis Georgi

 Strong activity of β-glucuronidase first appeared in the epidermal and glandular hair cells of leaf primordia regenerated from callus of Scutellaria baicalensis Georgi. Leaf primordia matured rapidly in culture to form shoots within 1 month in which both the mesophyll cells and the glandular hairs were deeply stained. Leaves predominantly accumulated β-glucuronidase in both glandular hair cells and mesophyll cells. β-Glucronidase activity in leaves was higher in the summer and decreased in the winter. The stem section collected in the summer had a different β-glucuronidase distribution pattern from that of the root in that in the former strong activity appeared in the periderm cells and collenchyma cells which was decreasingly dispersed into the phloem layer cells. In the winter, β-glucronidase activity decreased compared to that in summer. It can be argued that the distribution of β-glucuronidase in this plant is closely linked with the defense against pathogens: it is a starting key enzyme which may act together with the flavonoids, which play an important role as a proton donor for the detoxification metabolism of H₂O₂.

Initial stages of tumor cell-induced angiogenesis: evaluation via skin window chambers in rodent models

BACKGROUND

There is a paucity of information about events that follow immediately after tumor cells are triggered to initiate the process of angiogenesis (the formation of new blood vessels). Such information is relevant to the issue of when micrometastases vascularize and has implications for the accessibility of micrometastases to various treatments. In this study, we attempted to monitor events at the initiation of angiogenesis at the earliest possible stage of tumor growth in vivo.

METHODS

Two different rodent mammary tumor cell lines, R3230Ac from the Fischer 344 rat and 4T1 from the BALB/c mouse, were stably transfected with a gene that encodes an enhanced version of green fluorescence protein (GFP). GFP-labeled R3230Ac or 4T1 cells (about 20-50 cells) were implanted into dorsal skinfold window chambers of Fischer 344 rats or BALB/c mice, respectively. Tumor angiogenesis was then monitored serially and noninvasively for up to 4 weeks.

RESULTS

Clear evidence of modification of the host vasculature was observed when tumor mass reached approximately 60-80 cells, and functional new blood vessels were seen when tumor mass reached roughly 100-300 cells. Individual tumor cells exhibited a chemotaxis-like growth pattern toward the pre-existing host vasculature. When ex-flk1 (a soluble, truncated vascular endothelial cell growth factor receptor protein known to be antiangiogenic) was injected with the tumor cells, the initial angiogenic and tumor growth activities were inhibited considerably, indicating that angiogenesis inhibitors may halt tumor growth even before the onset of angiogenesis.

CONCLUSION

Angiogenesis induced by tumor cells after implantation in the host begins at a very early stage, i.e., when the tumor mass contains roughly 100-300 cells. Identification of chemotactic signals that initiate tumor cell migration toward the existing vasculature may provide valuable targets for preventing tumor progression and/or metastases.

[Expression of Bacillus thuringiensis (Bt) crystal toxin gene in the chloroplast of tobacco]

The 3.5 kb wild-type Bt Cry I A(c) gene and its 3' truncated forms (2.1 kb, 1.8 kb) were placed under the control of plastid expression signals consisting of the strong light-induced psbA promoter and its 3' untranslated region with the aadA cassette (Prrn, aadA and psbA3') as a selectable marker. The resulting vectors pBT3, pBT8 and pBT22 also contain flanking tobacco plastid DNA homology regions to direct insertion of the Bt transgene into the tobacco plastid genome between psbA and trnK by homologous recombination. Transformed plastid genomes were selectively amplified by growing the cells on spectinomycin medium. Several independently transformed lines were obtained at last. The results of Southern and Western blot demonstrated that these three kinds of Bt genes had been introduced into tobacco plants, and their filial generations are resistant to spectinomycin. Insecticidal activity assay with transgenic tobacco leaves indicate that some plants have strong toxicity to cotton bollworm. This is the first report in China that Bt gene has been introduced and successfully expressed in the chloroplast of higher plants.

Synthetic peptide sequence from the C-terminus of the insulin-like growth factor-I receptor that induces apoptosis and inhibition of tumor growth

Although the type 1 insulin-like growth factor receptor (IGF-IR) is a potent inhibitor of apoptosis, its C-terminus sequence sends contradictory signals, including a clearly proapoptotic signal. We have synthesized a peptide, peptide 2, having the sequence of the IGF-IR from residue 1282 to residue 1298 (C-terminus of the beta subunit). To favor its uptake into cells, we linked it to a stearic acid moiety at its NH-terminus. Peptide 2 is taken up by the cells, where it inhibits DNA synthesis and causes apoptosis, while a scrambled peptide (with stearic acid) and peptide 2 without stearic acid are completely ineffective. Peptide 2 is more effective when cells are in anchorage-independent conditions than when they grow in monolayer cultures. Accordingly, we find that peptide 2 can inhibit the growth of a human prostatic cell line in nude mice. The proapoptotic effect of peptide 2 is inhibited by the expression of Bcl-2 or by a dominant negative mutant of caspase 9. These and other data indicate that peptide 2 does not seem to be competing directly with the IGF-IR for common substrates, but that its proapoptotic effect is related to its ability to activate the caspase cascade.

Characterization of an antibody that can detect an activated IGF-I receptor in human cancers

The type 1 insulin-like growth factor receptor (IGF-IR) plays an important role in malignant transformation and in apoptosis. Its role in human cancer has now been firmly established. IGF-IR signaling occurs only when the receptor is activated by its ligands, which induce autophosphorylation of the receptor at several tyrosine residues. Although the IGF-IR (phosphorylated or not) can be detected in human cancers with conventional antibodies, it would be desirable to obtain antibodies that can detect the IGF-IR only when activated by its ligands. We describe and characterize in this paper such an antibody and show that it can be used in sections of human cancers to detect an autophosphorylated IGF-IR. This antibody will be useful in detecting autocrine or paracrine influences on normal and tumor cells and could eventually be also useful in diagnostic and prognostic studies of human primary and metastatic cancer.

Western blotting method for the immunostaining detection of glucuronides of glycyrrhetic acid using anti-glycyrrhizin monoclonal antibody

A method for detecting glucuronides of glycyrrhetic acid using Western blotting was investigated. Glucuronides of glycyrrhetic acid separated by silica gel TLC were transferred to a polyvinylidene difluoride membrane. The membrane was treated with sodium periodate solution followed by bovine serum albumin, resulting in a glucuronides of glycyrrhetic acid-BSA conjugate. Individual spots were stained by monoclonal antibody against glycyrrhizin. Immunostaining of glucuronides of glycyrrhetic acid was more sensitive compared to other staining methods. The newly established immunostaining method can be expanded to the distribution of glucuronides of glycyrrhetic acid in the plant body.

Identification of the CD8 DE loop as a surface functional epitope. Implications for major histocompatibility complex class I binding and CD8 inhibitor design

We used an approach of protein surface epitope mapping by synthetic peptides to analyze the surface structure-function relationship of the CD8 protein. Small synthetic peptide mimics of the CD8 DE loop were shown to effectively block CD8 binding to major histocompatibility complex (MHC) class I molecules and possess significant inhibitory activity on in vitro CD8(+) T cell function. These results suggested that the DE loop region of the CD8 protein is an important functional epitope mediating CD8-MHC class I interaction and the activation of CD8(+) T cells, a finding that is consistent with the recently reported crystal structure of the CD8-MHC class I complex. The structural basis for the biological activity of the DE loop peptide was further analyzed in a series of analogs containing alanine substitutions. This study provides support for the concept of bioactive peptide design based on protein surface epitopes and suggests that such an approach may be applicable to other protein-protein complexes, particularly those of immunoglobulin superfamily molecules.

Inhibition of tumor growth by targeting tumor endothelium using a soluble vascular endothelial growth factor receptor

Vascular endothelial growth factor (VEGF) is a leading candidate for an endogenous mediator of tumor angiogenesis. Recently, two endothelial cell surface receptors, flk-1 and flt-1, have been shown to mediate the angiogenic activities of VEGF. In this study, we have evaluated whether a soluble VEGF receptor could suppress tumor angiogenesis and thereby inhibit tumor growth. A soluble VEGF receptor was constructed by fusing the entire extracellular domain of murine flk-1 to a six-histidine tag at the COOH terminus (ExFlk.6His). In vitro, recombinant ExFlk.6His protein bound VEGF with high affinity (Kd, 16 nM) and blocked receptor activation in a dose-dependent manner and inhibited VEGF-induced endothelial cell proliferation and migration. ExFlk.6His bound to endothelial cells only in the presence of VEGF, and cell surface cross-linking yielded a high molecular weight complex consistent with the VEGF-mediated formation of a heterodimer between ExFlk.6His and the endogenous VEGF receptor. In vivo, ExFlk.6His potently inhibited corneal neovascularization induced by conditioned media from a rat mammary carcinoma cell line (R3230AC). Moreover, when ExFlk.6His protein was administered into a cutaneous tumor window chamber concomitantly with R3230AC carcinoma transplants, tumor growth was inhibited by 75% (P < 0.005) and vascular density was reduced by 50% (P < 0.002) compared with control-treated tumors. These results demonstrate the potential of ExFlk.6His to inhibit VEGF action by a potent "dominant-negative" mechanism and suggest that targeting VEGF action using a soluble receptor may be an effective antiangiogenic therapy for cancer and other "angiogenic" diseases.

[Prevention and treatment of postoperative complications following skin soft tissue expansion]

Since 1987, One hundred and fifty-four patients suffered from alopecia, neck and facial scar, and nasal defect had been treated with skin soft tissue expansion. The incidence of complication was decreased markedly, compared to previons report which was 11.7%. Two cases of this group were given up this procedure. The lessous learned from these case were as following. Strictly evaluated the case according to the indication, examined the expander carefully, improved the techniques to inbed the expander and infilled the sailine, those of which could obtain satisfactory result.

Inhibition of tumor angiogenesis using a soluble receptor establishes a role for Tie2 in pathologic vascular growth

Tie2 is a novel receptor tyrosine kinase that is expressed almost exclusively by vascular endothelium. Disruption of Tie2 function in transgenic mice resulted in embryonic lethality secondary to characteristic vascular defects; similar defects occurred after disruption of the Tie2 ligand. These findings indicate that the Tie2/Tie2 ligand pathway plays important roles during development of the embryonic vasculature. To determine whether the Tie2 pathway was involved in pathologic angiogenesis in adult tissues, a soluble form of the extracellular domain of murine Tie2 (ExTek.6His) was developed and used as a Tie2 inhibitor. After a single application of the ExTek.6His protein into a rat cutaneous window chamber, growth of a mammary tumor inside the chamber was reduced by > 75% (P < 0.005), and tumor vascular length density was reduced by 40% when compared with control-treated tumors (P < 0.01). In the rat cornea, ExTek.6His blocked angiogenesis stimulated by tumor cell conditioned media. ExTek.6His protein did not affect the viability of cultured tumor cells, indicating that the antitumor effect of ExTek.6His was due to the inhibition of tumor angiogenesis. These data demonstrate a role for the Tie2 pathway in pathologic angiogenesis, suggesting that targeting this pathway may yield effective antiangiogenic agents for treatment of cancer and other angiogenic diseases.

A natural motif approach to protein design: a synthetic leucine zipper peptide mimics the biological function of the platelet factor 4 protein

The design of smaller functional mimics of large proteins has long been an important challenge. In this study we use the natural leucine zipper as a structural template to design a 31-residue peptide analog that mimics the function of the larger platelet factor 4 (PF4) protein. The heparin binding activity of PF4 has been introduced into an unrelated leucine zipper sequence only by virtue of incorporating four lysines of PF4. Circular dichroism and binding experiments have shown that the designed leucine zipper peptide adopts a stable helical conformation and shows significant PF4-like heparin binding activity. These results strongly suggest that the lysine residues play an important role in the binding of PF4 to heparin. The de novo generation of the PF4 function in a designed leucine zipper peptide demonstrates that the leucine zipper motif is a useful scaffold for the design of functional peptides and proteins.

Simultaneous measurement of liposome extravasation and content release in tumors

OBJECTIVE

The success of liposome-based drug delivery systems for tumor targeting relies on maximum extravasation of liposomes into tumor interstitium, as well as optimal release of contents from the liposomes once within the tumor Liposome extravasation and content release are two separate processes that can be individually or jointly manipulated so a method is needed to monitor these two processes independently and simultaneously. In this report, we describe a method to measure liposome extravasation and content release in tumor tissues growing in a rat skinfold window chamber preparation.

METHODS

Mixtures of liposomes containing either doxorubicin or calcein, both of which are fluorescent, and liposomes surface-labeled with rhodamine were injected intravenously. Fluorescent, light intensities in a tumor region in two fluorescent channels were measured using an image-processing system. Light intensities of plasma from blood samples were also measured using this system. These measurements were used to calculate the amounts of liposomes and released contents in both plasma and tumor interstitium. The calculations were based on the fact that the liposome surface labels and contents emit fluorescent light at different wavelengths and when encapsulated, the contents fluorescence is self-quenched. The model included equations to account for fluorescent light "cross-contamination" by the two fluorochromes as well as equations relating the measured fluorescent light intensities to the amounts of liposomes and released contents. This method was applied to three situations in which liposome extravasation and content release were manipulated in different, predictable ways.

RESULTS AND CONCLUSION

Our results indicate that this method can perform simultaneous independent and quantitative measurements of liposome extravasation and content release. This method can potentially be used to study drug delivery of other carrier systems in vivo.

Stroma-free human hemoglobin A decreases R3230Ac rat mammary adenocarcinoma blood flow and oxygen partial pressure

We examined the effect of a nitric oxide (NO) quencher, stroma-free human hemoglobin A (HbA0; 0.01, 0.05, 0.1, 0.2 g/kg), on the blood flow measured using the Doppler flow technique, tumor oxygen pressure (pO2) and the diameter of the arterioles using R3230Ac mammary adenocarcinoma as the tumor model. In female Fischer 344 rats with 1-cm-diameter tumors implanted in the lateral aspect of the left quadriceps, intravenous infusion of 0.1 and 0.2 g/kg HbA0 decreased both central tumor and peripheral tumor blood flow by 20-30% (P < 0.05). Tumor pO2 decreased 28% with 0.2 g/kg HbA0, from 15 mm Hg (baseline) to 11 mm Hg at 10 min (P = 0.02). Although 0.2 g/kg HbA0 increased blood flow 55% in the left quadriceps muscle proximal to the implanted tumor (P < 0.05), HbA0 had little effect on blood flow in right quadriceps muscle with no tumor implanted, and increased right quadriceps pO2, from 21 mm Hg (baseline) to 23 mm Hg at 10 min (P = 0.03). HbA0 increased mean arterial pressure 5-10% in a manner that was dependent on dose while heart rate concurrently decreased 9-19%. The diameter of the arterioles supplying the tumor was rapidly reduced 10% by 0.2 g/kg HbA0 (P = 0.037) and remained stable through 60 min of observation (P = 0.005). HbA0 selectively reduces tumor blood flow and tumor pO2 through vasoconstriction of the arterioles supplying the tumor. Vascular NO quenching provides an alternative to NO synthase inhibition as a means to achieve the goal of selective tumor hypoxia.

[Measurement of skin area of expansion and defect on scalp]

The skin expander has been widely used to produce extra skin by the plastic surgeon, but there is no a scientific method for measuring the skin area of external expansion. The plastic surgeon usually do not know exactly whether the skin area of expansion more or less than the skin area of defect. A morphologic measure method was developed to figure out accurately the area of expansion and the area of defect separately. Clinical application has proved that the method can help the plastic surgeon know the wanted skin area of expansion in practice before operation.

Arteriolar oxygenation in tumour and subcutaneous arterioles: effects of inspired air oxygen content

Carbogen is thought to be more effective than normobaric oxygen in reducing tumour hypoxia because it may reduce hyperoxic vasoconstriction. In this study, tumour and normal arteriolar diameters were measured simultaneously with perivascular pO2 during air breathing followed by either carbogen or 100% oxygen to determine whether the action of carbogen is the result of alterations in feeding vessel diameter. Fischer-344 rats bearing dorsal flap window chambers, with or without implanted R3230AC tumours, were the experimental subjects. Arteriolar diameters were measured using optical techniques and perivascular pO2 was measured using recessed-tip electrodes (3-6 microns tip diameter). Baseline arteriolar pO2 averaged 30-50% of blood gas pO2 (mean = 97 mmHg). Both hyperoxic gases increased blood gas pO2 by 4-to 5-fold, but relative improvements in arteriolar pO2 were < or = 2.5 for all arterioles studied. This means that these normobaric high O2 gases are not very efficient in increasing O2 delivery to tumours. In addition, improvements in tumour arteriolar pO2 were transient for both hyperoxic gases. Oxygen and carbogen caused no change and mild vasodilatory responses in tumour arterioles, respectively. Normal arterioles on the other hand, tended toward vasoconstriction by carbogen breathing. Peri-arteriolar pO2 in tumours increased within the first 5 min of breathing either hyperoxic gas, followed by a decline back toward values seen with air-breathing. These results suggest that temporal changes in tumour oxygenation after exposure to carbogen or O2 may not be due to changes in perfusion. Other factors, such as changes in O2 consumption rate may be involved.

Nitric oxide synthase inhibition irreversibly decreases perfusion in the R3230Ac rat mammary adenocarcinoma

We examined the microvascular effects of competitive nitric oxide synthase (NOS) inhibition with NG-monomethyl-L-arginine (MeArg), followed by L-arginine, on R3230Ac mammary adenocarcinoma perfusion. In window preparations containing tumours, superfusion of 50 microM MeArg reduced diameters of central tumour venules by 13%, of peripheral tumour venules by 17% and of normal venules near tumours by 16% from baseline. MeArg reduced red blood cell (RBC) velocity in central tumour venules by 25%, and increased intermittent flow and stasis frequency by 20% in central tumour venules. Subsequent superfusion of 200 microM L-arginine did not restore diameters or RBC velocity of any tumour preparation venules, and decreased length density in both central tumour venules and peripheral tumour venules. In contrast, MeArg reduced control preparation venule diameter by 30% and RBC velocity by 66%, but did not decrease length density or increase intermittent flow or stasis frequency. Unlike tumour preparation venules, L-arginine restored control venule diameters and velocities. NOS inhibition reduces both tumour and control venule perfusion, but the effect is blunted in the vicinity of tumours, possibly because of increased NOS levels. Perfusion can be subsequently restored in control, but not tumour, venules with L-arginine. Tumour NOS inhibition, followed by normal tissue rescue with L-arginine, may provide a novel means to achieve the goal of selective tumour hypoxia.

Rational reconstruction of the active site of a class mu glutathione S-transferase

Isoenzymes 3-3 and 4-4 of the mu class glutathione S-transferases share 77% sequence identity but have distinctly different catalytic properties. Analysis of the crystal structure of isoenzyme 3-3 in complex with the diastereomeric products of the addition of GSH to phenanthrene 9,10-oxide (Ji, X., Johnson, W. W., Sesay, M. A., Dickert, L., Prasad, S. M., Ammon, H. L., Armstrong, R. N., and Gilliland, G. L. (1994) Biochemistry 33, 1043-1052) reveals that 3 residues that are in van der Waals contact with the xenobiotic portion of the product are different in the type 4 subunit. The three mutations, V9I, I111A, and S209A, have been introduced into isoenzyme 3-3 individually and in combination in an attempt to minimally reconstruct the active site of the enzyme to mimic the type 4 subunit in structure and function. The results suggest that the V9I mutation is an important determinant in the stereoselectivity of the enzyme toward enones and epoxides. The I111A mutation increases the catalytic efficiency of the enzyme toward para-substituted 4-phenyl-3-buten-2-ones (XPBO) as measured by kcat/KmXPBO but does not affect kcat. The S209A mutation has no effect on catalysis. The double and triple mutants V9I/I111A and V9I/I111A/S209A exhibit both a high stereoselectivity and high kcat/KmXPBO comparable to that of isoenzyme 4-4. Analysis of substituent effects on the kinetics and stereoselectivity of the enzyme toward the enone substrates suggests that the mechanistic bases for the catalytic behavior of the isoenzyme 4-4 and the reconstructed mutants are not identical. The results provide functional evidence for the catalytic importance of specific residues previously identified by x-ray crystallography.

Comparison of the effects of hydralazine on tumor and normal tissue blood perfusion by MRI

PURPOSE

The differential effects on blood perfusion of the vasodilator hydralazine (HYD) between tumor and normal muscle have been measured using the dynamic enhanced-magnetic resonance imaging (DE-MRI) technique.

METHODS AND MATERIALS

DE-MRI is a noninvasive method of determining blood perfusion in tumors and normal tissues using the MR contrast agent Gd-DTPA. Hydralazine is currently being used in an attempt to increase tumor response to bioreductive agents and to hyperthermia.

RESULTS

We show that a dose of 1.2 mg/kg HYD causes an increase in tumor perfusion while doses > or = 2.5 mg/kg cause a decrease in tumor perfusion. The latter was accompanied by a dose-dependent increase in normal muscle perfusion consistent with the "steal effect."

CONCLUSION

This study demonstrates the sensitivity of the DE-MRI technique and its capability of providing estimates of blood perfusion in normal and tumor tissue as well as in smaller regions of a solid tumor. Such features would make it clinically useful in the study of tumor response to radiation therapy and chemotherapy in patients.