RESUMEN

Fibrous extracellular matrix (ECM) proteins provide mechanical structure and adhesive scaffolding to resident cells within stromal tissues. Aligned ECM fibers play an important role in directing morphogenetic processes, supporting mechanical loads, and facilitating cell migration. Various methods have been developed to align matrix fibers in purified biopolymer hydrogels, such as type I collagen, including flow-induced alignment, uniaxial tensile deformation, and magnetic particles. However, purified biopolymers have limited orthogonal tunability of biophysical cues including stiffness, fiber density, and fiber alignment. Here, we generate synthetic, cell-adhesive fiber segments of the same length-scale as stromal fibrous proteins through electrospinning. Superparamagnetic iron oxide nanoparticles (SPIONs) embedded in synthetic fiber segments enable magnetic field induced alignment of fibers within an amorphous bulk hydrogel. We find that SPION density and magnetic field strength jointly influence fiber alignment and identify conditions to control the degree of alignment. Tuning fiber length allowed the alignment of dense fibrous hydrogel composites without fiber entanglement or regional variation in the degree of alignment. Functionalization of fiber segments with cell adhesive peptides induced tendon fibroblasts to adopt a uniaxial morphology akin to within native tendon. Furthermore, we demonstrate the utility of this hydrogel composite to direct multicellular migration from MCF10A spheroids and find that fiber alignment prompts invading multicellular strands to separate into disconnected single cells and multicellular clusters. These magnetic fiber segments can be readily incorporated into other natural and synthetic hydrogels and aligned with inexpensive and easily accessible rare earth magnets, without the need for specialized equipment. 3D hydrogel composites where stiffness/crosslinking, fiber density, and fiber alignment can be orthogonally tuned may provide insights into morphogenetic and pathogenic processes that involve matrix fiber alignment and can enable systematic investigation of the individual contribution of each biophysical cue to cell behavior.

RESUMEN

Unit operations during production influence the sensory properties of nonfat dry milk (NFDM) and milk protein concentrate (MPC). Off-flavors in dried dairy ingredients decrease consumer acceptance of ingredient applications. Previous work has shown that spray-drying parameters affect physical and sensory properties of whole milk powder and whey protein concentrate. The objective of this study was to determine the effect of inlet temperature and feed solids concentration on the flavor of NFDM and MPC 70% (MPC70). Condensed skim milk (50% solids) and condensed liquid MPC70 (32% solids) were produced using pilot-scale dairy processing equipment. The condensed products were then spray dried at either 160, 210, or 260°C inlet temperature and 30, 40, or 50% total solids for NFDM and 12, 22, or 32% for MPC70 in a randomized order. The entire experiment was replicated 3 times. Flavor of the NFDM and MPC70 was evaluated by sensory and instrumental volatile compound analyses. Surface free fat, particle size, and furosine were also analyzed. Both main effects (30, 40, and 50% solids and 160, 210, and 260°C inlet temperature) and interactions between solids concentration and inlet temperature were investigated. Interactions were not significant. In general, results were consistent for NFDM and MPC70. Increasing inlet temperature and feed solids concentration increased sweet aromatic flavor and decreased cardboard flavor and associated lipid oxidation products. Increases in furosine with increased inlet temperature and solids concentration indicated increased Maillard reactions during drying. Particle size increased and surface free fat decreased with increasing inlet temperature and solids concentration. These results demonstrate that increasing inlet temperatures and solids concentration during spray drying decrease off-flavor intensities in NFDM and MPC70 even though the heat treatment is greater compared with low temperature and low solids.

Asunto(s)

Proteínas de la Leche , Leche/química , Animales , Aromatizantes , Manipulación de Alimentos , Gusto

RESUMEN

PURPOSE: We examined whether the novel 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolate, compound 2, might be an effective treatment for malignant pleural mesothelioma (MPM), reflecting its selective membrane transport by the proton-coupled folate transport (PCFT) over the reduced folate carrier (RFC). METHODS: HeLa sublines expressing exclusively PCFT (R1-11-PCFT4) or RFC (R1-11-RFC6) and H2452 MPM cells were assayed for transport with [(3)H]compound 2. [(3)H]Polyglutamate metabolites of compound 2 were measured in R1-11-PCFT4 and H2452 cells. In vitro cell proliferation assays and colony formation assays were performed. Inhibition of glycinamide ribonucleotide formyltransferase (GARFTase) was assayed by nucleoside protection assays and in situ GARFTase assays with [(14)C]glycine. In vivo efficacy was established with early- and advanced-stage H2452 xenografts in severe-combined immunodeficient (SCID) mice administered intravenous compound 2. RESULTS: [(3)H]Compound 2 was selectively transported by PCFT and was metabolized to polyglutamates. Compound 2 selectively inhibited proliferation of R1-11-PCFT4 cells over R1-11-RFC6 cells. H2452 human MPM cells were sensitive to the antiproliferative effects of compound 2. By colony-forming assays with H2452 cells, compound 2 was cytotoxic. Compound 2 inhibited GARFTase in de novo purine biosynthesis. In vivo efficacy was confirmed toward early- and advanced-stage H2452 xenografts in SCID mice administered compound 2. CONCLUSIONS: Our results demonstrate potent antitumor efficacy of compound 2 toward H2452 MPM cells in vitro and in vivo, reflecting its efficient membrane transport by PCFT, synthesis of polyglutamates, and inhibition of GARFTase. Selectivity for non-RFC cellular uptake processes by tumor-targeted antifolates such as compound 2 presents an exciting new opportunity for treating solid tumors.

Asunto(s)

Antagonistas del Ácido Fólico/uso terapéutico , Mesotelioma/tratamiento farmacológico , Transportador de Folato Acoplado a Protón/fisiología , Pirimidinas/uso terapéutico , Pirroles/uso terapéutico , Animales , Proliferación Celular/efectos de los fármacos , Femenino , Antagonistas del Ácido Fólico/farmacocinética , Antagonistas del Ácido Fólico/farmacología , Células HeLa , Humanos , Ratones , Ratones SCID , Fosforribosilglicinamida-Formiltransferasa/antagonistas & inhibidores , Ácido Poliglutámico/metabolismo , Pirimidinas/farmacocinética , Pirroles/farmacocinética , Ensayos Antitumor por Modelo de Xenoinjerto

RESUMEN

Uptake of 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates with four or three bridge carbons [compound 1 (C1) and compound 2 (C2), respectively] into solid tumors by the proton-coupled folate transporter (PCFT) represents a novel therapeutic strategy that harnesses the acidic tumor microenvironment. Although these compounds are not substrates for the reduced folate carrier (RFC), the major facilitative folate transporter, RFC expression may alter drug efficacies by affecting cellular tetrahydrofolate (THF) cofactor pools that can compete for polyglutamylation and/or binding to intracellular enzyme targets. Human tumor cells including wild-type (WT) and R5 (RFC-null) HeLa cells express high levels of PCFT protein. C1 and C2 inhibited proliferation of R5 cells 3 to 4 times more potently than WT cells or R5 cells transfected with RFC. Transport of C1 and C2 was virtually identical between WT and R5 cells, establishing that differences in drug sensitivities between sublines were independent of PCFT transport. Steady-state intracellular [³H]THF cofactors derived from [³H]5-formyl-THF were depleted in R5 cells compared with those in WT cells, an effect exacerbated by C1 and C2. Whereas C1 and C2 polyglutamates accumulated to similar levels in WT and R5 cells, there were differences in polyglutamyl distributions in favor of the longest chain length forms. In severe combined immunodeficient mice, the antitumor efficacies of C1 and C2 were greater toward subcutaneous R5 tumors than toward WT tumors, confirming the collateral drug sensitivities observed in vitro. Thus, solid tumor-targeted antifolates with PCFT-selective cellular uptake should have enhanced activities toward tumors lacking RFC function, reflecting contraction of THF cofactor pools.

Asunto(s)

Antineoplásicos/farmacología , Antagonistas del Ácido Fólico/farmacología , Transportador de Folato Acoplado a Protón/metabolismo , Pirimidinas/farmacología , Pirroles/farmacología , Proteína Portadora de Folato Reducido/metabolismo , Tiofenos/farmacología , Animales , Antineoplásicos/metabolismo , Transporte Biológico , Línea Celular Tumoral , Membrana Celular/metabolismo , Proliferación Celular/efectos de los fármacos , Ensayos de Selección de Medicamentos Antitumorales , Espacio Extracelular/metabolismo , Femenino , Antagonistas del Ácido Fólico/metabolismo , Humanos , Ratones , Ratones SCID , Trasplante de Neoplasias , Ácidos Pteroilpoliglutámicos/metabolismo , Pirimidinas/metabolismo , Pirroles/metabolismo , Relación Estructura-Actividad , Tetrahidrofolatos/metabolismo , Tiofenos/metabolismo , Microambiente Tumoral

RESUMEN

The proton-coupled folate transporter (PCFT) is a proton-folate symporter with an acidic pH optimum. By real-time reverse transcription-polymerase chain reaction, PCFT was expressed in the majority of 53 human tumor cell lines, with the highest levels in Caco-2 (colorectal adenocarcinoma), SKOV3 (ovarian), and HepG2 (hepatoma) cells. A novel 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolate (compound 1) was used to establish whether PCFT can deliver cytotoxic drug under pH conditions that mimic the tumor microenvironment. Both 1 and pemetrexed (Pmx) inhibited proliferation of R1-11-PCFT4 HeLa cells engineered to express PCFT without the reduced folate carrier (RFC) and of HepG2 cells expressing both PCFT and RFC. Unlike Pmx, 1 did not inhibit proliferation of R1-11-RFC6 HeLa cells, which express RFC without PCFT. Treatment of R1-11-PCFT4 cells at pH 6.8 with 1 or Pmx inhibited colony formation with dose and time dependence. Transport of [(3)H]compound 1 into R1-11-PCFT4 and HepG2 cells was optimal at pH 5.5 but appreciable at pH 6.8. At pH 6.8, [(3)H]compound 1 was metabolized to (3)H-labeled polyglutamates. Glycinamide ribonucleotide formyltransferase (GARFTase) in R1-11-PCFT4 cells was inhibited by 1 at pH 6.8, as measured by an in situ GARFTase assay, and was accompanied by substantially reduced ATP levels. Compound 1 caused S-phase accumulation and a modest level of apoptosis. An in vivo efficacy trial with severe combined immunodeficient mice implanted with subcutaneous HepG2 tumors showed that compound 1 was active. Our findings suggest exciting new therapeutic possibilities to selectively deliver novel antifolate drugs via transport by PCFT over RFC by exploiting the acidic tumor microenvironment.

Asunto(s)

Sistemas de Liberación de Medicamentos/métodos , Antagonistas del Ácido Fólico/metabolismo , Neoplasias/metabolismo , Transportador de Folato Acoplado a Protón/metabolismo , Pirimidinas/metabolismo , Animales , Relación Dosis-Respuesta a Droga , Femenino , Antagonistas del Ácido Fólico/administración & dosificación , Células HeLa , Células Hep G2 , Humanos , Ratones , Ratones Endogámicos ICR , Ratones SCID , Neoplasias/tratamiento farmacológico , Pirimidinas/administración & dosificación , Ensayos Antitumor por Modelo de Xenoinjerto/métodos

RESUMEN

2-Amino-4-oxo-6-substituted pyrrolo[2,3-d]pyrimidine antifolates with a thienoyl side chain (compounds 1-3, respectively) were synthesized for comparison with compound 4, the previous lead compound of this series. Conversion of hydroxyl acetylen-thiophene carboxylic esters to thiophenyl-α-bromomethylketones and condensation with 2,4-diamino-6-hydroxypyrimidine afforded the 6-substituted pyrrolo[2,3-d]pyrimidine compounds of type 18 and 19. Coupling with l-glutamate diethyl ester, followed by saponification, afforded 1-3. Compound 3 selectively inhibited the proliferation of cells expressing folate receptors (FRs) α or ß, or the proton-coupled folate transporter (PCFT), including KB and IGROV1 human tumor cells, much more potently than 4. Compound 3 was more inhibitory than 4 toward ß-glycinamide ribonucleotide formyltransferase (GARFTase). Both 3 and 4 depleted cellular ATP pools. In SCID mice with IGROV1 tumors, 3 was more efficacious than 4. Collectively, our results show potent antitumor activity for 3 in vitro and in vivo, associated with its selective membrane transport by FRs and PCFT over RFC and inhibition of GARFTase, clearly establishing the 3-atom bridge as superior to the 1-, 2-, and 4-atom bridge lengths for the activity of this series.

Asunto(s)

Antineoplásicos/síntesis química , Receptor 1 de Folato/metabolismo , Receptor 2 de Folato/metabolismo , Antagonistas del Ácido Fólico/síntesis química , Glutamatos/síntesis química , Fosforribosilglicinamida-Formiltransferasa/antagonistas & inhibidores , Transportador de Folato Acoplado a Protón/metabolismo , Pirimidinas/síntesis química , Pirimidinonas/síntesis química , Proteína Portadora de Folato Reducido/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Línea Celular Tumoral , Ensayos de Selección de Medicamentos Antitumorales , Femenino , Antagonistas del Ácido Fólico/química , Antagonistas del Ácido Fólico/farmacología , Glutamatos/química , Glutamatos/farmacología , Humanos , Ratones , Ratones SCID , Trasplante de Neoplasias , Oocitos/efectos de los fármacos , Oocitos/fisiología , Técnicas de Placa-Clamp , Pirimidinas/química , Pirimidinas/farmacología , Pirimidinonas/química , Pirimidinonas/farmacología , Estereoisomerismo , Relación Estructura-Actividad , Trasplante Heterólogo , Xenopus

RESUMEN

PURPOSE: To determine the possibility of synergistic antileukemic activity and the underlying molecular mechanisms associated with cytarabine combined with valproic acid (VPA; a histone deacetylase inhibitor and a Food and Drug Administration-licensed drug for treating both children and adults with epilepsy) in pediatric acute myeloid leukemia (AML). EXPERIMENTAL DESIGN: The type and extent of antileukemic interactions between cytarabine and VPA in clinically relevant pediatric AML cell lines and diagnostic blasts from children with AML were determined by MTT assays and standard isobologram analyses. The effects of cytarabine and VPA on apoptosis and cell cycle distributions were determined by flow cytometry analysis and caspase enzymatic assays. The effects of the two agents on DNA damage and Bcl-2 family proteins were determined by Western blotting. RESULTS: We showed synergistic antileukemic activities between cytarabine and VPA in four pediatric AML cell lines and nine diagnostic AML blast samples. t(8;21) AML blasts were significantly more sensitive to VPA and showed far greater sensitivities to combined cytarabine and VPA than non-t(8;21) AML cases. Cytarabine and VPA cooperatively induced DNA double-strand breaks, reflected in induction of γH2AX and apoptosis, accompanied by activation of caspase-9 and caspase-3. Further, VPA induced Bim expression and short hairpin RNA knockdown of Bim resulted in significantly decreased apoptosis induced by cytarabine and by cytarabine plus VPA. CONCLUSIONS: Our results establish global synergistic antileukemic activity of combined VPA and cytarabine in pediatric AML and provide compelling evidence to support the use of VPA in the treatment of children with this deadly disease.

Asunto(s)

Citarabina/farmacología , Leucemia Mieloide Aguda/tratamiento farmacológico , Ácido Valproico/farmacología , Apoptosis/efectos de los fármacos , Caspasa 3/metabolismo , Caspasa 9/metabolismo , Citarabina/química , Daño del ADN , Sinergismo Farmacológico , Humanos , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/patología , Masculino , Relación Estructura-Actividad , Células Tumorales Cultivadas , Ácido Valproico/química

RESUMEN

The proton-coupled folate transporter (PCFT) is a folate-proton symporter with an acidic pH optimum, approximating the microenvironments of solid tumors. We tested 6-substituted pyrrolo[2,3-d]pyrimidine antifolates with one to six carbons in the bridge region for inhibition of proliferation in isogenic Chinese hamster ovary (CHO) and HeLa cells expressing PCFT or reduced folate carrier (RFC). Only analogs with three and four bridge carbons (N-{4-[3-2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]-pyrimidin-6-yl)propyl]benzoyl}-L-glutamic acid (compound 2) and N-{4-[4-2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]-pyrimidin-6-yl)butyl]benzoyl}*-L-glutamic acid (compound 3), respectively) were inhibitory, with 2 ≫ 3. Activity toward RFC-expressing cells was negligible. Compound 2 and pemetrexed (Pmx) competed with [(3)H]methotrexate for PCFT transport in PCFT-expressing CHO (R2/hPCFT4) cells from pH 5.5 to 7.2; inhibition increased with decreasing pH. In Xenopus laevis oocytes microinjected with PCFT cRNA, uptake of 2, like that of Pmx, was electrogenic. Cytotoxicity of 2 toward R2/hPCFT4 cells was abolished in the presence of adenosine or 5-amino-4-imidazolecarboxamide, suggesting that glycinamide ribonucleotide formyltransferase (GARFTase) in de novo purine biosynthesis was the primary target. Compound 2 decreased GTP and ATP pools by ∼50 and 75%, respectively. By an in situ GARFTase assay, 2 was ∼20-fold more inhibitory toward intracellular GARFTase than toward cell growth or colony formation. Compound 2 irreversibly inhibited clonogenicity, although this required at least 4 h of exposure. Our results document the potent antiproliferative activity of compound 2, attributable to its efficient cellular uptake by PCFT, resulting in inhibition of GARFTase and de novo purine biosynthesis. Furthermore, they establish the feasibility of selective chemotherapy drug delivery via PCFT over RFC, a process that takes advantage of a unique biological feature of solid tumors.

Asunto(s)

Antineoplásicos/administración & dosificación , Sistemas de Liberación de Medicamentos/métodos , Antagonistas del Ácido Fólico/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Neoplasias/tratamiento farmacológico , Purinas/biosíntesis , Pirimidinas/administración & dosificación , Pirroles/administración & dosificación , Animales , Antineoplásicos/química , Antineoplásicos/metabolismo , Células CHO , Cricetinae , Cricetulus , Femenino , Inhibidores de Crecimiento/administración & dosificación , Inhibidores de Crecimiento/química , Inhibidores de Crecimiento/metabolismo , Células HeLa , Humanos , Neoplasias/metabolismo , Transportador de Folato Acoplado a Protón , Purinas/antagonistas & inhibidores , Pirimidinas/química , Pirimidinas/metabolismo , Pirroles/química , Pirroles/metabolismo , Xenopus laevis

RESUMEN

Melatonin has a variety of functions in human physiology and is involved in a number of pathological events including neoplastic processes. The tissue protective actions of melatonin are attributed to its antioxidant activity though, under certain conditions, melatonin might also exert oxidant effects, particularly in cancer cells. This study evaluated the effects of 10(-5) and 10(-3) m concentrations of melatonin on human leukemia cells. Moderate cytotoxic effects of melatonin at 10(-3) m concentrations were observed in CMK, Jurkat and MOLT-4 cells which was associated with significant reactive oxygen species (ROS) generation. Melatonin treatment was not associated with significant cytotoxicity in HL-60 cells, although the generation of ROS was significantly increased. K562 and Daudi cells did not appear to be effected by melatonin treatment. Cellular membrane lipid peroxidation was not influenced by melatonin with the exception of CMK cells. Cell cycle kinetics were not affected in melatonin-treated samples, again with the exception of CMK cells which showed increased apoptosis. Melatonin, therefore, induces the production of ROS that may be associated with cytotoxicity depending on the concentration of melatonin in some leukemia cells and does not appear to stimulate leukemia cell growth. These pro-oxidant actions of melatonin may assist in limiting leukemic cell growth.

Asunto(s)

Melatonina/toxicidad , Oxidantes/toxicidad , Especies Reactivas de Oxígeno/metabolismo , Apoptosis/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Células HL-60 , Humanos , Células Jurkat , Leucemia/metabolismo , Leucemia/patología

RESUMEN

Children with Down syndrome (DS) with acute megakaryocytic leukemia (AMkL) have very high survival rates compared with non-DS AMkL patients. Somatic mutations identified in the X-linked transcription factor gene, GATA1, in essentially all DS AMkL cases result in the synthesis of a shorter (40 kDa) protein (GATA1s) with altered transactivation activity and may lead to altered expression of GATA1 target genes. Using the Affymetrix U133A microarray chip, we identified 551 differentially expressed genes between DS and non-DS AMkL samples. Transcripts for the bone marrow stromal-cell antigen 2 (BST2) gene, encoding a transmembrane glycoprotein potentially involved in interactions between leukemia cells and bone marrow stromal cells, were 7.3-fold higher (validated by real-time polymerase chain reaction) in the non-DS compared with the DS group. Additional studies confirmed GATA1 protein binding and transactivation of the BST2 promoter; however, stimulation of BST2 promoter activity by GATA1s was substantially reduced compared with the full-length GATA1. CMK sublines, transfected with the BST2 cDNA and incubated with HS-5 bone marrow stromal cells, exhibited up to 1.7-fold reduced cytosine arabinoside (ara-C)-induced apoptosis, compared with mock-transfected cells. Our results demonstrate that genes that account for differences in survival between DS and non-DS AMkL cases may be identified by microarray analysis and that differential gene expression may reflect relative transactivation capacities of the GATA1s and full-length GATA1 proteins.

Asunto(s)

Síndrome de Down/genética , Factor de Transcripción GATA1/genética , Leucemia Megacarioblástica Aguda/tratamiento farmacológico , Leucemia Megacarioblástica Aguda/genética , Niño , Análisis por Conglomerados , Citarabina/toxicidad , Cartilla de ADN , Síndrome de Down/complicaciones , Regulación Neoplásica de la Expresión Génica , Humanos , Leucemia Megacarioblástica Aguda/complicaciones , Luciferasas/genética , Hibridación de Ácido Nucleico , Análisis de Secuencia por Matrices de Oligonucleótidos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transfección , Células Tumorales Cultivadas

RESUMEN

Down syndrome children with acute megakaryocytic leukemia (AMkL) have higher cure rates than non-Down syndrome acute myeloid leukemia (AML) patients treated with cytosine arabinoside (ara-C). Megakaryoblasts from Down syndrome AML patients are more sensitive in vitro to ara-C than cells from non-Down syndrome AML patients. Somatic mutations in the GATA1 transcription factor have been detected exclusively and almost uniformly in Down syndrome AMkL patients, suggesting a potential linkage to the chemotherapy sensitivity of Down syndrome megakaryoblasts. Stable transfection of wild-type GATA1 cDNA into the Down syndrome AMkL cell line CMK resulted in decreased (8- to 17-fold) ara-C sensitivity and a threefold-lower generation of the active ara-C metabolite ara-CTP compared with that for mock-transfected CMK cells. High intracellular levels of uridine arabinoside (ara-U) (an inactive ara-C catabolite generated by cytidine deaminase) and cytidine deaminase transcripts were detected in GATA1-transfected CMK sublines, whereas no ara-U was detected in mock-transfected cells. Cytidine deaminase transcripts were a median 5.1-fold (P = .002) lower in Down syndrome megakaryoblasts (n = 16) than in blast cells from non-Down syndrome patients (n = 56). These results suggest that GATA1 transcriptionally upregulates cytidine deaminase and that the presence or absence of GATA1 mutations in AML blasts likely confers differences in ara-C sensitivities due to effects on cytidine deaminase gene expression, which, in turn, contributes to the high cure rate of Down syndrome AMkL patients.

Asunto(s)

Citidina Desaminasa/metabolismo , Proteínas de Unión al ADN/metabolismo , Síndrome de Down/complicaciones , Síndrome de Down/metabolismo , Leucemia Megacarioblástica Aguda/metabolismo , Factores de Transcripción/metabolismo , Antimetabolitos Antineoplásicos/metabolismo , Trifosfato de Arabinofuranosil Citosina/metabolismo , Arabinofuranosil Uracilo/metabolismo , Western Blotting , Niño , Citarabina/metabolismo , Citidina Desaminasa/genética , Proteínas de Unión al ADN/genética , Síndrome de Down/genética , Factores de Unión al ADN Específico de las Células Eritroides , Factor de Transcripción GATA1 , Humanos , Leucemia Megacarioblástica Aguda/complicaciones , Leucemia Megacarioblástica Aguda/enzimología , Leucemia Megacarioblástica Aguda/genética , Reacción en Cadena de la Polimerasa , Factores de Tiempo , Factores de Transcripción/genética , Transcripción Genética , Activación Transcripcional , Regulación hacia Arriba

RESUMEN

Myeloblasts from Down syndrome (DS) children with acute myeloid leukemia (AML) are significantly more sensitive in vitro to 1-beta-D-arabinofuranosylcytosine (ara-C) and generate higher 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP) than non-DS AML myeloblasts. Semiquantitative reverse transcription-PCR analyses demonstrated that transcripts for cytidine deaminase (CDA) were 2.7-fold lower in DS than for non-DS myeloblasts. In contrast, transcripts of cystathionine-beta-synthase and deoxycytidine kinase were a median 12.5- and 2.6-fold higher in DS compared with non-DS myeloblasts. The ratio of deoxycytidine kinase/CDA transcripts significantly correlated with ara-C sensitivities and ara-CTP generation. In clinically relevant AML cell line models, high cystathionine-beta-synthase transcripts in DS CMK cells were accompanied by 10-fold greater ara-C sensitivity and 2.4-fold higher levels of ara-CTP compared with non-DS CMS cells. Overexpression of CDA in non-DS THP-1 cells was associated with a 100-fold decreased ara-C sensitivity and 40-fold decreased ara-CTP generation. THP-1 cells secreted CDA into the incubation media and converted extracellular ara-C completely to 1-beta-D-arabinofuranosyluracil within 30 min. Rapid amplification of 5'-cDNA ends (5'-RACE) and reverse transcription-PCR assays identified short- (sf) and long-form (lf) CDA transcripts in THP-1 cells with different 5' untranslated regions and translational start sites; however, only the latter resulted in the active CDA. Although 5' flanking sequences for both CDA transcripts exhibited promoter activity in reporter gene assays, activity for the CDAlf was low. The presence of several GATA1 binding sites in the CDAsf promoter and the uniform detection of GATA1 mutations in DS megakaryocytic leukemia suggested the potential role of GATA1 in regulating CDA transcription and the CDAsf promoter acting as an enhancer. Transfection of GATA1 into Drosophila Mel-2 cells stimulated the CDAlf promoter in a dose-dependent fashion. Additional identification of the mechanisms of differential expression of genes encoding enzymes involved in ara-C metabolism between DS and non-DS myeloblasts may lead to improvements in AML therapy.

Asunto(s)

Citarabina/toxicidad , Citosina Desaminasa/genética , Proteínas de Unión al ADN/genética , Síndrome de Down/patología , Leucemia/patología , Factores de Transcripción/genética , Secuencia de Bases , Muerte Celular/efectos de los fármacos , Línea Celular Tumoral , Células Cultivadas , Citosina Desaminasa/metabolismo , Cartilla de ADN , Proteínas de Unión al ADN/metabolismo , Síndrome de Down/genética , Factores de Unión al ADN Específico de las Células Eritroides , Exones/genética , Factor de Transcripción GATA1 , Humanos , Intrones/genética , Leucemia/genética , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Transcripción/metabolismo , Transcripción Genética

RESUMEN

We describe a rare complication of an acute aortic dissection. Proximally the dissection propagated into the right atrium, resulting in an aorta-right atrium fistula. The clinical course, operative findings, and operative treatment are discussed.

Asunto(s)

Rotura de la Aorta/complicaciones , Atrios Cardíacos , Fístula Vascular/etiología , Enfermedad Aguda , Femenino , Humanos , Persona de Mediana Edad

RESUMEN

Vincristine (VCR) is an effective drug against acute lymphoblastic leukemia (ALL), many solid tumors, but not acute myeloid leukemia. It has been hypothesized that resistance of myeloblasts to VCR is related to myeloperoxidase (MPO) and production of hypochlorous acid (HOCl). We investigated the relationship between VCR degradation and MPO expression and serum HOCl concentrations in pediatric patients with ALL, lymphoma and solid tumors. We studied the sera from 43 children, of which 23 were newly diagnosed and as yet untreated cancer patients, 10 on chemotherapy and 10 healthy control subjects. Patients' sera were incubated with VCR alone or in the presence of taurine (T) or acetaminophen (APAP) and post-incubation VCR and HOCL concentrations were measured. Significant correlations between serum MPO expression, HOCl concentrations and VCR degradation were seen. In the chemotherapy group, MPO-positive patients produced high levels of HOCl and reciprocally low post-incubation VCR levels. HOCl and VCR concentrations in this group were significantly different than other groups studied. Both APAP and T inhibited VCR degradation in the sera of the chemotherapy group but not to the same degree. The effects seen here were consistent for both ALL and the lymphoma/solid tumor cases. Our results indicate that HOCl can increase VCR degradation in vitro in the serum and this effect is significantly more pronounced in pediatric patients undergoing chemotherapy.

Asunto(s)

Antineoplásicos Fitogénicos/metabolismo , Ácido Hipocloroso/sangre , Leucemia Linfoide/sangre , Peroxidasa/sangre , Vincristina/metabolismo , Acetaminofén/farmacología , Enfermedad Aguda , Analgésicos no Narcóticos , Estudios de Casos y Controles , Niño , Resistencia a Antineoplásicos , Humanos , Neoplasias/sangre , Neoplasias/enzimología , Neoplasias/patología , Taurina/farmacología