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Biomedical subjects

D Small

Publications and source records attributed to D Small.

At least 19 recordsLinked to original sources
PubMed2006

Combinations of the FLT3 inhibitor CEP-701 and chemotherapy synergistically kill infant and childhood MLL-rearranged ALL cells in a sequence-dependent manner.

Mixed lineage leukemia (MLL) rearrangements occur in 80% of infants and 5% of older children with acute lymphoblastic leukemia (ALL). These cases have a poor prognosis with current therapy. The FLT3 kinase is overexpressed and constitutively activated in MLL-rearranged ALL cells. The FLT3 inhibitor CEP-701 selectively kills these cells, but is unlikely to be curative if used as monotherapy. To identify potentially synergistic combination strategies, we studied CEP-701 and six standard chemotherapeutic agents in three sequences of exposure (S1: chemotherapy followed by CEP-701, S2: simultaneous exposure to both; and S3: CEP-701 followed by chemotherapy) using MLL-rearranged ALL cell lines and patient bone marrow samples. MTT cytotoxicity and annexin V binding apoptosis assays were used to assess antileukemic effects. Combination indices (CI) were calculated for each combination (CI<0.9 - synergistic; CI 0.9-1.1 - additive; CI>1.1 - antagonistic). A striking pattern of sequence-dependent synergy was observed: S1 was markedly synergistic (mean CI=0.59+/-0.10), S2 was additive (mean CI=0.99+/-0.09) and S3 was antagonistic (mean CI=1.23+/-0.10). The sequence dependence is attributable to the effect of CEP-701 on cell cycle kinetics, and is mediated specifically by FLT3 inhibition, as these effects are not seen in control cells without activated FLT3.

Antineoplastic Agents↗
PubMed2004

FLT3 inhibitors: a paradigm for the development of targeted therapeutics for paediatric cancer.

The area of molecularly-targeted cancer therapeutics is generating tremendous interest and excitement. While clinical investigation of these agents has been largely limited to adults, clinical trials for paediatric cancer patients with many of these agents are now underway. This paper reviews the current status of molecularly-targeted therapies for paediatric malignancies, with special attention given to one class of agents, inhibitors of the FLT3 receptor tyrosine kinase. FLT3 is expressed and activated in many human leukemias, including a significant percentage of pediatric AML and infant and childhood ALL, especially in the setting of MLL gene rearrangement. Activating mutations of FLT3 portend a poor prognosis in pediatric AML. Activated FLT3 can be effectively and selectively targeted by small molecule inhibitors, and these agents have shown promise in early phase clinical trials in adults with AML. Limited preclinical data with FLT3 inhibitors in MLL-rearranged ALL have also been reported. Challenges and future directions for the use of FLT3 inhibitors and other targeted agents in paediatric cancer are discussed.

Adjuvants, Immunologic↗
PubMed2004

Hormonal manipulation of benign metastasizing leiomyomas: report of two cases and review of the literature.

Benign metastasizing leiomyomas (BMLs) occur predominantly in women during reproductive years. The condition is characterized by uterine leiomyomas associated with the development, typically years later, of slow-growing metastatic lesions. The most commonly affected organs are the lungs, but BMLs have been reported in lymph nodes, deep soft tissues, mesentery, bones, the central nervous system, and the heart. In many cases, these lesions have an indolent course and are discovered rather incidentally. However, occasionally they can present with debilitating symptoms or even life-threatening complications. The presence of estrogen and progesterone receptors in these tumors supports their origin from uterine smooth muscle and, more importantly, makes them amenable to hormonal manipulation. Radical interventions, such as extensive tumor debulking and oophorectomy for hormonal control, although effective in many cases, are not always possible or desirable and carry significant morbidity. Here we present two cases of BMLs to illustrate the role of newer therapeutic agents, the estrogen receptor modulators and the aromatase inhibitors, in the hormonal manipulation of these tumors.

Adult↗
PubMed2003

FLT3: ITDoes matter in leukemia.

FMS-like tyrosine kinase-3 (FLT3), a receptor tyrosine kinase, is important for the development of the hematopoietic and immune systems. Activating mutations of FLT3 are now recognized as the most common molecular abnormality in acute myeloid leukemia, and FLT3 mutations may play a role in other hematologic malignancies as well. The poor prognosis of patients harboring these mutations renders FLT3 an obvious target of therapy. This review summarizes the data on the molecular biology and clinical impact of FLT3 mutations, as well as the therapeutic potential of several small-molecule FLT3 inhibitors currently in development.

Acute Disease↗
PubMed2002

Bis(1H-2-indolyl)-1-methanones as inhibitors of the hematopoietic tyrosine kinase Flt3.

Aberrant expression and activating mutations of the class III receptor tyrosine kinase Flt3 (Flk-2, STK-1) have been linked to poor prognosis in acute myeloid leukemia (AML). Inhibitors of Flt3 tyrosine kinase activity are, therefore, of interest as potential therapeutic compounds. We previously described bis(1H-2-indolyl)-1-methanones as a novel class of selective inhibitors for platelet-derived growth factor receptors (PDGFR). Several bis(1H-2-indolyl)-1-methanone derivatives, represented by the compounds D-64406 and D-65476, are also potent inhibitors of Flt3. They inhibit proliferation of TEL-Flt3-transfected BA/F3 cells with IC(50) values of 0.2-0.3 microM in the absence of IL-3 but >10 microM in the presence of IL-3. Ligand-stimulated autophosphorylation of Flt3 in EOL-1 cells and corresponding downstream activation of Akt/PKB are effectively inhibited by bis(1H-2-indolyl)-1-methanones whereas autophosphorylation of c-Kit/SCF receptor or c-Fms/CSF-1 receptor is less sensitive or insensitive, respectively. Flt3 kinase purified by different methods is potently inhibited in vitro, demonstrating a direct mechanism of inhibition. 32D cells, expressing a constitutively active Flt3 variant with internal tandem duplication are greatly sensitized to radiation-induced apoptosis in the presence of D-64406 or D-65476 in the absence but not in the presence of IL-3. Thus, bis(1H-2-indolyl)-1-methanones are potential candidates for the treatment of Flt3-driven leukemias.

Animals↗
PubMed2002

Human AML cells in NOD/SCID mice: engraftment potential and gene expression.

Most cases of human acute myeloid leukemia (AML) engraft in irradiated non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. Intravenous transfer of as few as 10(5) human AML cells resulted in engraftment. Cases with poor prognosis clinical features, including FLT3 mutations, tended to engraft efficiently. Nevertheless, AML cells obtained from patients at relapse did not engraft more efficiently than cells obtained from the same patients at initial diagnosis. One passage of human AML cells in NOD/SCID mice did not appear to select for increased virulence, as measured by serial transplantation efficiency. Finally, cDNA microarray analyses indicated that approximately 95% of genes were expressed at similar levels in human AML cells immunopurified after growth in mice, as compared to cells assessed directly from patients. Thus, the growth of human AML cells in NOD/SCID mice could yield large numbers of human AML cells for direct experimental use and could also function as a renewable, potentially unlimited source of leukemia cells, via serial transplantation.

Acute Disease↗
PubMed2002

Inhibition of the transforming activity of FLT3 internal tandem duplication mutants from AML patients by a tyrosine kinase inhibitor.

FLT3 is a receptor tyrosine kinase that may play a role in a significant proportion of leukemias. In addition to being aberrantly expressed in acute leukemias, activating mutations of the FLT3 gene have been found in patients with AML, myelodysplastic syndrome (MDS) and more rarely, ALL. Internal tandem duplications (ITDs) of the FLT3 gene have been detected in 17-34% of patients with AML and portend a poor prognosis for these patients. FLT3 receptors containing ITD mutations (FLT3/ITDs) are constitutively activated in the absence of FLT3 ligand (FL) stimulation leading to the activation of downstream signaling proteins, including ERK and STAT 5. FLT3 activity, therefore, is a logical target for therapeutic intervention. AG1296 is a tyrosine kinase inhibitor of the tyrphostin class that shows inhibitory activity for wild-type FLT3, in addition to the PDGF and c-KIT receptors. We examined the inhibitory effects of AG1296 on FLT3/ITDs isolated from AML patients in the IL-3-dependent cell line, Ba/F3, as well as in primary leukemia samples from AML patients. Immunoprecipitation and immunoblotting analyses demonstrated that FLT3/ITDs were constitutively phosphorylated in the absence of FL. The auto-phosphorylation of FLT3/ITDs was inhibited by AG1296 with an IC(50) of approximately 1 microM. FLT3/ITDs were associated with constitutive phosphorylation of ERK, STAT 5A, STAT 5B, CBL, VAV and SHP2 in Ba/F3 cells. The phosphorylation of these downstream signaling molecules was suppressed in a dose-responsive fashion by AG1296. AG1296 inhibited IL-3 independent growth and induced apoptosis in Ba/F3 cells transformed by FLT3/ITDs. AG1296 also inhibited FLT3 auto-phosphorylation, and induced a cytotoxic effect, in primary AML cells. These findings suggest that inhibiting the activity of FLT3 may have a therapeutic value in some leukemias expressing FLT3/ITDs.

Amino Acid Sequence↗
PubMed2001

A FLT3 tyrosine kinase inhibitor is selectively cytotoxic to acute myeloid leukemia blasts harboring FLT3 internal tandem duplication mutations.

Internal tandem duplication (ITD) mutations of the receptor tyrosine kinase FLT3 have been found in 20% to 30% of patients with acute myeloid leukemia (AML). These mutations constitutively activate the receptor and appear to be associated with a poor prognosis. Recent evidence that this constitutive activation is leukemogenic renders this receptor a potential target for specific therapy. In this study, dose-response cytotoxic assays were performed with AG1295, a tyrosine kinase inhibitor active against FLT3, on primary blasts from patients with AML. For each patient sample, the degree of cytotoxicity induced by AG1295 was compared to the response to cytosine arabinoside (Ara C) and correlated with the presence or absence of a FLT3/ITD mutation. AG1295 was specifically cytotoxic to AML blasts harboring FLT3/ITD mutations. The results suggest that these mutations contribute to the leukemic process and that the FLT3 receptor represents a therapeutic target in AML. (Blood. 2001;98:885-887)

Acute Disease↗
PubMed2001

Soluble Jagged 1 represses the function of its transmembrane form to induce the formation of the Src-dependent chord-like phenotype.

We have previously demonstrated that the expression of the soluble extracellular domain of the transmembrane ligand for Notch receptors, Jagged 1 (sJ1), in NIH 3T3 cells results in the formation of a matrix-dependent chord-like phenotype, the loss of contact inhibition of growth, and an inhibition of pro-alpha 1(I) collagen expression. In an effort to define the mechanism by which sJ1 induces this phenotype, we report that sJ1 transfectants display biochemical and cytoskeletal alterations consistent with the activation of Src. Indeed, cotransfection of sJ1 transfectants with a dominant-negative mutant of Src resulted in the loss of matrix-dependent chord formation and correlated with the restoration of type I collagen expression and contact inhibition of growth. We also report that the sJ1-mediated induction of Src activity and related phenotypes, including chord formation, may result from the inhibition of endogenous Jagged 1-mediated Notch signaling since it was not possible to detect an sJ1-dependent induction of CSL-dependent transcription in these cells. Interestingly, NIH 3T3 cells transfected with dominant-negative (but not constitutively active) mutants of either Notch 1 or Notch 2 displayed a similar Src-related phenotype as the sJ1 transfectants. These data suggest that the ability of sJ1 to mediate chord formation is Src-dependent and requires the repression of endogenous Jagged 1-mediated Notch signaling, which is tolerant to the destabilization of the actin cytoskeleton, a mediator of cell migration.

3T3 Cells↗
PubMed2001

Home monitoring service improves mean arterial pressure in patients with essential hypertension. A randomized, controlled trial.

BACKGROUND: Technological advances in the distribution of information have opened new avenues for patient care. Few trials, however, have used telemedicine to improve blood pressure in patients with essential hypertension. OBJECTIVE: To determine the efficacy of a telecommunication service in reducing blood pressure. DESIGN: Randomized, controlled trial. SETTING: University-affiliated primary care outpatient clinics. PATIENTS: 121 adults with essential hypertension who were under evaluation for a change in antihypertensive therapy. INTERVENTION: A home service consisting of automatic transmission of blood pressure data over telephone lines, computerized conversion of the information into report forms, and weekly electronic transmission of the report forms to physicians and patients. MEASUREMENTS: 24-hour ambulatory blood pressure monitoring at baseline and exit. The primary end point was change in mean arterial pressure from baseline to exit. RESULTS: Mean arterial pressure decreased by 2.8 mm Hg in patients receiving the home service and increased by 1.3 mm Hg in patients receiving usual care (P = 0.013 for the difference). Mean diastolic blood pressure decreased by 2.0 mm Hg for home service but increased by 2.1 mm Hg for usual care (P = 0.012 for the difference). Mean systolic blood pressure decreased by 4.9 mm Hg for home service and 0.1 mm Hg for patients receiving usual care (P = 0.047 for the difference). Among African-American patients, mean arterial pressure decreased by 9.6 mm Hg in those receiving home service and increased by 5.25 mm Hg in those receiving usual care (P = 0.047). Part of the decrease in blood pressure for home service was due to more frequent changes in the type or dose of antihypertensive medications. CONCLUSION: This telecommunication service was efficacious in reducing the mean arterial pressure of patients with established essential hypertension.

Aged↗
PubMed2001

Members of the Jagged/Notch gene families are expressed in injured arteries and regulate cell phenotype via alterations in cell matrix and cell-cell interaction.

The Jagged/Notch signaling pathways control cell fate determination and differentiation, and their dysfunction is associated with human pathologies involving cardiovascular abnormalities. To determine the presence of these genes during vascular response to injury, we analyzed expression of Jagged1, Jagged2, and Notch1 through 4 after balloon catheter denudation of the rat carotid artery. Although low levels of Jagged1, Jagged2, and constitutive expression of Notch1 were seen in uninjured endothelium, expression of all was significantly increased in injured vascular cells. High Jagged1 expression was restricted to the regenerating endothelial wound edge, whereas Notch transcripts were abundant in endothelial and smooth muscle cells. To understand the basis for Jagged/Notch control of cellular phenotype, we studied an in vitro model of NIH3T3 cells transfected with a secreted form of the extracellular domain of Jagged1. We report that the soluble Jagged1 protein caused decreased cell-matrix adhesion and cell migration defects. Cadherin-mediated intercellular junctions as well as focal adhesions were modified in soluble Jagged1 transfectants, demonstrating that cell-cell contacts and adhesion plaques may be targets of Jagged/Notch activity. We suggest that Jagged regulation of cell-cell and cell-matrix interactions may contribute to the control of cell migration in situations of tissue remodeling in vivo.

3T3 Cells↗
PubMed2001

Vitreous concentration of topically applied brimonidine tartrate 0.2%.

OBJECTIVE: To determine the vitreous concentration of brimonidine after topical administration of Alphagan. DESIGN: Prospective observational case series. PARTICIPANTS: Eighteen patients scheduled for elective pars plana vitrectomy. METHODS: Brimonidine tartrate, 0.2%, was topically administered twice or three times daily for 4 to 14 days preoperatively in 13 patients. Four patients served as controls, without application of brimonidine. A dry, undiluted vitrectomy specimen obtained intraoperatively was collected, frozen, and sent to an independent bioanalytical facility for quantitative determination of vitreous concentration of brimonidine using gas chromatography/mass spectrometry. MAIN OUTCOME MEASURES: The concentration of brimonidine in human vitreous. RESULTS: All patients treated with brimonidine measured above the lower limit of quantitation with a mean vitreous concentration of 185 +/- 500 nM. All patients not treated with brimonidine measured at or below the lower limit of quantitation of 0.05 nM. There was a trend toward higher concentration in patients who were either aphakic or pseudophakic compared with those that were phakic. CONCLUSIONS: Topically applied brimonidine results in vitreous levels at or above 2 nM, the concentration shown to activate alpha(2)-receptors.

Administration, Topical↗
PubMed2001

Seasonal variation in plasma lipids, lipoproteins, apolipoprotein A-I and vitellogenin in the freshwater turtle, Chrysemys picta.

An analysis of plasma lipids and lipoprotein fractions was performed over the course of the annual ovarian cycle of the female turtle, Chrysemys picta. Determinations of total plasma triglycerides, cholesterol, vitellogenin and apolipoprotein A-I (apoA-I) were made. The lipid and protein composition of the lipoprotein fractions [very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) and very high density lipoprotein (VHDL)] were also observed over the same period. Plasma triglyceride and vitellogenin levels were significantly increased in the spring preovulatory period and fall recrudescent phase. Total plasma cholesterol levels were significantly elevated only at the onset of the fall recrudescent phase and apoA-I levels were highest during the postoviposition/ovarian arrest phase. The triglyceride content of VLDL was highest in preovulatory animals and there were apparent seasonal changes in the expression of apoA-I and apoE of HDL/VHDL. We conclude that the coordinate regulation of lipids and protein contributes to seasonal ovarian growth and clearance of lipids from plasma, both of which are most likely under hormonal control.

Animals↗
PubMed2001

Inhibition of FLT3-mediated transformation by use of a tyrosine kinase inhibitor.

FLT3 is a member of the type III receptor tyrosine kinase (RTK) family. These receptors all contain an intrinsic tyrosine kinase domain that is critical to signaling. Aberrant expression of the FLT3 gene has been documented in both adult and childhood leukemias including AML, ALL and CML. In addition, 17-27% of pediatric and adult patients with AML have small internal tandem duplication mutations in FLT3. Patients expressing the mutant form of the receptor have been shown to have a decreased chance for cure. Our previous study, using a constitutively activated FLT3, demonstrated transformation of Ba/F3 cells and leukemic development in an animal model. Thus, there is accumulating evidence for a role for FLT3 in human leukemias. This has prompted us to search for inhibitors of FLT3 as a possible therapeutic approach in these patients. AG1296 is a compound of the tyrphostin class that is known to selectively inhibit the tyrosine kinase activity of the PDGF and KIT receptors. Since FLT3 is a close relative of KIT, we wanted to test the possible inhibitory activity of AG1296 on FLT3. In transfected Ba/F3 cells, AG1296 selectively and potently inhibited autophosphorylation of FL-stimulated wild-type and constitutively activated FLT3. Treatment by AG1296 abolished IL-3-independent proliferation of Ba/F3 cells expressing the constitutively activated FLT3 and thus, reversed the transformation mediated by activated FLT3. Inhibition of FLT3 activity by AG1296 in cells transformed by activated FLT3 resulted in apoptotic cell death, with no deleterious effect on their parental counterparts. Addition of IL-3 rescued the growth of cells expressing activated FLT3 in the presence of AG1296. This demonstrates that the inhibition is specific to the FLT3 pathway in that it leaves the kinases of the IL-3 pathway and other kinases further downstream involved in proliferation intact. Several proteins phosphorylated by the activated FLT3 signaling pathway, including STAT 5A, STAT 5B and CBL, were no longer phosphorylated when these cells were treated with AG1296. The activity against FLT3 suggests a potential therapeutic application for AG1296 or similar drugs in the treatment of leukemias involving deregulated FLT3 tyrosine kinase activity and as a tool for studying the biology of FLT3.

Animals↗
PubMed2001

Characteristics of sustained blood-brain barrier opening and tissue injury in a model for focal trauma in the rat.

Minor stab wounding of rodent brain by needle or razor blade is a standard model for immunohistochemical investigations of secondary neuronal degeneration and scarring. Opening of the blood-brain barrier (BBB) to plasma molecules and inflammatory cells is integral to the secondary injury process. To facilitate quantitative study of these BBB phenomena, we tested the utility of a stereotaxic wire knife as a minimally invasive way for modeling of focal trauma and bleeding in brain parenchyma and substantial, reproducible BBB damage. Adult rats were anesthetized, and through a skull burr hole, the 0.3-mm dia guide cannula housing a laterally extendable tungsten wire (0.13 mm dia) was inserted into the right striatum. A layering of horizontal disk-like cuts (3 mm dia) was made, producing a cylindrical lesion of approximately 18 mm3 volume, approximately 2.7% of the cerebral hemisphere. Transfer constants (Ki) for blood to brain permeation of [3H]sucrose measured from 30 min to 2 weeks postlesion showed sustained BBB leakiness; for example, mean Ki +/- SEM (nL.g(-1) x s(-1)) for a standard, matrix-dissected forebrain sample enclosing the lesion were 7.2 +/- 1.2 (day 1 postlesion), 8.1 +/-1.4 (day 3), 5.4 +/- 0.8 (day 14) compared with values for contralateral nonlesioned forebrain ranging from 1.3 +/- 0.05 to 1.6 +/- 0.3 (n = 3-4 samples per time point). Analysis of the simultaneous transport of [14C]sucrose (MW = 342 Da) and [3H]inulin (MW approximately 5,000) showed significantly larger upward increments in Ki for sucrose than inulin, indicating a pore-like opening mechanism. Significant edema was measured 3 days postlesion. A reactive glial response was indicated by an increase in S100beta by 6 h and a glial scar forming around the lesion by 7 days. Secondary brain injury was indicated by a 10% loss of hemisphere mass, measured at 2 months. The wire knife enabled tailoring of interstitial trauma with a minimum of extraneous injury and supported reproducible measurements of sustained BBB injury using relatively few animals.

Animals↗
PubMed2001

Use of the Brief Psychiatric Rating Scale to facilitate differential diagnosis at acute inpatient admission.

BACKGROUND: The advent of managed care has necessitated strategies for quickly and accurately diagnosing psychiatric disorders. The aim of the present study was to ascertain whether the Brief Psychiatric Rating Scale-Anchored (BPRS-A) would be a useful adjunct to more traditional diagnostic strategies at acute inpatient admission. METHOD: Using a sample of 207 inpatients admitted during an 8-month index period, we examined the utility of the BPRS-A in predicting whether patients were more likely to be diagnosed with schizophrenia, bipolar disorder, or major depression (DSM-IV). RESULTS: Discriminant function analyses were used to correctly predict 68%, 60%, and 74% of patients diagnosed with schizophrenia, bipolar disorder, and major depression, respectively. The main predictors of diagnostic category, in descending order. were BPRS-A depressed mood item, BPRS-A positive symptoms scale, BPRS-A excitement item, BPRS-A guilt feelings item, BPRS-A mannerisms and posturing item, and number of previous episodes. CONCLUSION: As efforts are directed toward continuous quality improvement within mental health settings, an emphasis must be placed on improving the efficiency and accuracy of diagnostic procedures. The BPRS-A shows promise as a time-efficient assessment instrument that may be useful in facilitating differential diagnosis at inpatient admission and may increase the likelihood that efficacious prerelease interventions and appropriate aftercare services are implemented.

Acute Disease↗
PubMed2000

A non-transmembrane form of Jagged-1 regulates the formation of matrix-dependent chord-like structures.

Jagged-Notch interactions regulate a transmembrane ligand-receptor signaling pathway involved in the regulation of cell fate determination as well as myoblast and endothelial cell differentiation. To further examine the role of the transmembrane ligand, Jagged-1, in the regulation of cell differentiation, we stably transfected NIH 3T3 cells with a truncated form of Jagged(J)-1, which results in the secretion of a soluble(s) form of the protein. Comparison of gene expression by serial analysis demonstrated that among the 227 transcripts differentially regulated in the sJ-1 transfectants, the expression of the pro-alpha-2(I) collagen transcript and pro-alpha-1(I) collagen translation product was predominantly repressed in sJ-1 transfectants. When plated on extracellular matrices, sJ-1 transfectants formed prominent chord-like structures on type I collagen but not on fibrin, fibronectin, or vitronectin. While the sJ-1 transfectants exhibited growth kinetics similar to control cells and were unable to grow in soft agar, the cells were less sensitive to contact inhibition of growth in vitro and sJ-1 allografts formed tissue masses in nude mice after a prolonged latency period and exhibited an abundance of host-derived microvascular endothelial cells. These data suggest that J-1 may be able to modulate, in a matrix-dependent manner, the organization of cell to cell interactions including its ability to promote the development of chord-like structures.

3T3 Cells↗