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Biomedical subjects

G Leone

Publications and source records attributed to G Leone.

At least 55 records · Page 3Linked to original sources
PubMed2002

Preponderance of methylenetetrahydrofolate reductase C677T homozygosity among leukemia patients intolerant to methotrexate.

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, a common mutation of the gene encoding the enzyme that catalyzes reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a carbon donor in the metabolism of folate, determines a striking reduction in the enzyme activity in carriers of mutation at homozygous status. PATIENTS AND METHODS: We retrospectively analyzed the incidence of MTHFR C677T and the influence of genotype on methotrexate (MTX) toxicity in patients with acute leukemia undergoing maintenance chemotherapy. Seventy-eight patients were analyzed and 61 were evaluable for toxicity. MTX toxicity was assessed on bone marrow, liver and mucosae. RESULTS: The incidence of the C677T mutation was as expected in the general Italian population with 23.08% of patients being TT, 38.46% of patients CT and 38.46% of patients CC. The TT genotype was significantly associated with an increase of toxicity during MTX administration. No specific pattern of toxicity was detected, although in TT patients myelosuppression and liver toxicity were more pronounced. CONCLUSIONS: TT genotype may indicate a need to reduce the dose of MTX during prolonged administration. Considering the high prevalence of homozygous individuals in the Italian population, pretreatment screening may be worthwhile.

Adolescent↗
PubMed2002

Characterization and complete nucleotide sequence of Strawberry mottle virus: a tentative member of a new family of bipartite plant picorna-like viruses.

An isolate of Strawberry mottle virus (SMoV) was transferred from Fragaria vesca to Nicotiana occidentalis and Chenopodium quinoa by mechanical inoculation. Electron micrographs of infected tissues showed the presence of isometric particles of approximately 28 nm in diameter. SMoV-associated tubular structures were also conspicuous, particularly in the plasmodesmata of C. quinoa. DsRNA extraction of SMoV-infected N. occidentalis yielded two bands of 6.3 and 7.8 kbp which were cloned and sequenced. Gaps in the sequence, including the 5' and 3' ends, were filled using RT-PCR and RACE. The genome of SMoV was found to consist of RNA1 and RNA2 of 7036 and 5619 nt, respectively, excluding a poly(A) tail. Each RNA encodes one polyprotein and has a 3' non-coding region of approximately 1150 nt. The polyprotein of RNA1 contains regions with identities to helicase, viral genome-linked protein, protease and polymerase (RdRp), and shares its closest similarity with RNA1 of the tentative nepovirus Satsuma dwarf virus (SDV). The polyprotein of RNA2 displayed some similarity to the large coat protein domain of SDV and related viruses. Phylogenetic analysis of the RdRp region showed that SMoV falls into a separate group containing SDV, Apple latent spherical virus, Naval orange infectious mottling virus and Rice tungro spherical virus. Given the size of RNA2 and the presence of a long 3' non-coding region, SMoV is more typical of a nepovirus, although atypically for a nepovirus it is aphid transmissible. We propose that SMoV is a tentative member of an SDV-like lineage of picorna-like viruses.

3' Untranslated Regions↗
PubMed2002

The role of hematopoietic stem cells in the treatment of ovarian cancer.

In recent years hematopoietic stem cells (HSC) have been the object of new research efforts and scientific advances. Therapeutic strategies have been set up using HSC for the treatment of solid tumors such as ovarian cancer. In this context different approaches have been proposed and clinically investigated. The "autologous" approach refers to the use of HSC as hematologic support to high-dose chemotherapy regimens, and to the use of HSC as an abundant source of dendritic cells for cancer vaccination protocols. Our institution has developed a long-term experience in high-dose chemotherapy with autologous HSC transplantation as first-line treatment of advanced ovarian cancer, and in the use of cytokines both for the HSC collection and for the post-transplantation hematopoietic recovery. Moreover, the "allogeneic" approach with HSC consists of the allogeneic transplantation with both myeloablative/standard or nonmyeloablative/reduced conditioning regimens, which has been proposed as a new adoptive immunotherapeutic treatment for different nonhematologic malignancies. Perspectives in the use of HSC in oncology comprise the possibility of an HSC ex vivo expansion, the use of umbilical cord blood HSC, and the development of future HSC-based gene-therapy programs.

Animals↗
PubMed2002

Clinically significant autoimmune hemolytic anemia with a negative direct antiglobulin test by routine tube test and positive by column agglutination method.

In two to five percent of cases of autoimmune hemolytic anemia (AIHA),the patient's RBCs are negative in the direct antiglobulin test (DAT). We describe a patient with AIHA with a negative DAT when tested by the traditional tube test but with a strongly positive one when tested by column agglutination. When the DAT was repeated by tube test using 4 degrees Celsius saline washes, it became positive. This phenomenon has been observed when low-affinity antibodies are involved in AIHA. The patient's history and serologic findings are detailed in this report.

Journal Article↗
PubMed2001

The E2F1-3 transcription factors are essential for cellular proliferation.

The retinoblastoma tumour suppressor (Rb) pathway is believed to have a critical role in the control of cellular proliferation by regulating E2F activities. E2F1, E2F2 and E2F3 belong to a subclass of E2F factors thought to act as transcriptional activators important for progression through the G1/S transition. Here we show, by taking a conditional gene targeting approach, that the combined loss of these three E2F factors severely affects E2F target expression and completely abolishes the ability of mouse embryonic fibroblasts to enter S phase, progress through mitosis and proliferate. Loss of E2F function results in an elevation of p21Cip1 protein, leading to a decrease in cyclin-dependent kinase activity and Rb phosphorylation. These findings suggest a function for this subclass of E2F transcriptional activators in a positive feedback loop, through down-modulation of p21Cip1, that leads to the inactivation of Rb-dependent repression and S phase entry. By targeting the entire subclass of E2F transcriptional activators we provide direct genetic evidence for their essential role in cell cycle progression, proliferation and development.

Animals↗
PubMed2001

BAALC, the human member of a novel mammalian neuroectoderm gene lineage, is implicated in hematopoiesis and acute leukemia.

The molecular basis of human leukemia is heterogeneous. Cytogenetic findings are increasingly associated with molecular abnormalities, some of which are being understood at the functional level. Specific therapies can be developed based on such knowledge. To search for new genes in the acute leukemias, we performed a representational difference analysis. We describe a human gene in chromosome 8q22.3, BAALC (brain and acute leukemia, cytoplasmic), that is highly conserved among mammals but evidently absent from lower organisms. We characterized BAALC on the genomic level and investigated its expression pattern in human and mouse, as well as its complex splicing behavior. In vitro studies of the protein showing its subcellular localization suggest a function in the cytoskeleton network. Two isoforms are specifically expressed in neuroectoderm-derived tissues, but not in tumors or cancer cell lines of nonneural tissue origin. We show that blasts from a subset of patients with acute leukemia greatly overexpress eight different BAALC transcripts, resulting in five protein isoforms. Among patients with acute myeloid leukemia, those overexpressing BAALC show distinctly poor prognosis, pointing to a key role of the BAALC products in leukemia. Our data suggest that BAALC is a gene implicated in both neuroectodermal and hematopoietic cell functions.

3T3 Cells↗
PubMed2001

Effects of harmine on dopamine output and metabolism in rat striatum: role of monoamine oxidase-A inhibition.

In vivo microdialysis was used to investigate the effects of acute injections of harmine on extracellular concentrations of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxindoleacetic acid (5-HIAA) in the striatum of awake rats. Administration of harmine in doses of 0.5, 2.5, and 10 mg/kg (i.p.) elicited a dose-dependent increase of the dopamine efflux to 152, 173, and 243% and a decrease in DOPAC to 52, 36, and 10%, and HVA to 67, 45, and 20% throughout, respectively; 5-HIAA concentrations were decreased to 81, 74, and 72% only. In contrast to D-amphetamine, which also increases dopamine release and decreases its metabolites, the stimulatory action of harmine on dopamine release in the striatum was totally abolished in the presence of tetrodotoxin (1 microM). Similar to monoamine oxidase (MAO)-A inhibitors, harmine potentiated the stimulatory effect of D-amphetamine (10 microM), infused by reverse microdialysis in the striatum, on dopamine release. Pre-treatment with the benzodiazepine receptor antagonist flumazenil (5 mg/kg, i.p.) did not modulate the effect of harmine on striatal dopamine release and metabolism. Administration of the reversible MAO-A inhibitor, moclobemide (20 mg/kg, i.p.), induced an increase in dopamine to 256% and a decrease in DOPAC, HVA, and 5-HIAA to 30, 24, and 62%, respectively, reproducing a pattern similar to that of harmine. Taken together, these results indicate that harmine affects the brain dopamine system probably by acting as a MAO-A inhibitor and not as an inverse agonist for the benzodiazepine receptors.

Animals↗
PubMed2001

HIV-protease inhibitors contribute to P-glycoprotein efflux function defect in peripheral blood lymphocytes from HIV-positive patients receiving HAART.

P-glycoprotein (P-gp) has been found expressed in normal human cells, such as bone marrow and peripheral blood cells. The aim of this study was to investigate whether HIV-protease inhibitors (HIV-PIs) interact with P-gp efflux function in normal human peripheral blood lymphocytes (PBLs) and CD34+ progenitor cells. Moreover, we analyzed the in vivo effect of HIV-PIs on P-gp function in PBLs from HIV-infected patients receiving highly active antiretroviral therapy (HAART). We found that HIV-PIs (i.e., ritonavir, saquinavir, nelfinavir and indinavir) interfere with P-gp function in normal PBLs as demonstrated by the reduced efflux of rhodamine 123 (Rh123). This effect was dose-dependent and suggested the following hierarchy: ritonavir > saquinavir > nelfinavir > indinavir. We further analyzed the effect of HIV-PIs on the P-gp function in specific PBLs subsets. Our results show an HIV-PI-induced inhibition of P-gp function in CD4+ and CD8+ T cell subsets, mostly caused by the effect on the naive compartment of both CD4+ and CD8+ T cells. The same inhibitory effect was found in CD34+ hematopoietic progenitor cells. With respect to the in vivo evaluation of P-gp function in PBLs from HIV-infected patients, we found reduced levels of Rh123 efflux that reached the lowest value in AIDS patients receiving HAART. We concluded that HIV-PIs interfere with P-gp function in major cellular targets for HIV infection, such as CD4+ T cells and CD34+ progenitor cells. This ability may contribute to P-gp efflux function defect found in HIV-infected patients and suggests that drug interaction studies are crucial to an overall understanding of the effects of this important group of drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Expression of p15(ink4b) gene during megakaryocytic differentiation of normal and myelodysplastic hematopoietic progenitors.

In myelodysplastic syndrome (MDS), the expression of the cyclin-dependent kinase inhibitor p15(ink4B) (p15) is frequently decreased because of the aberrant methylation of the gene promoter; p15 is normally up-regulated during megakaryocytic differentiation. It was hypothesized that p15 methylation and deregulation of gene expression contribute to defective megakaryocytopoiesis in patients with MDS. Here it is shown that the increasing autocrine production of TGF-beta1 stimulates megakaryocytic differentiation in normal CD34(+) cells and that p15 mediates, at least in part, this effect. This TGF-beta1-dependent pathway is altered in MDS CD34(+) progenitors because of p15 methylation. The demethylating agent 2-deoxyAZAcytidin can restore the normal demethylated state of the p15 gene and increase its expression. Nevertheless, MDS CD34(+) cells only poorly differentiate to the megakaryocytic lineage. These findings suggest that p15 methylation occurs in a neoplastic clone with a profound defect of cell proliferation, survival, and differentiation that cannot be overcome by using a demethylating drug.

Anemia, Refractory, with Excess of Blasts↗
PubMed2001

Hsp90 phosphorylation is linked to its chaperoning function. Assembly of the reovirus cell attachment protein.

Studies on Hsp90 have mainly focused on its involvement in the activation of several families of protein kinases and of steroid hormone receptors. Little is known regarding the role of Hsp90 in the folding of nascent proteins. We previously reported that Hsp90 plays an active role in the posttranslational assembly of the C-terminal globular head of the reovirus attachment protein final sigma1. We show here that Hsp90 becomes phosphorylated in this process. However, only the unphosphorylated form of Hsp90 is complexed with final sigma1, suggesting that Hsp90 phosphorylation is coupled to the release of the chaperone from the target protein. Geldanamycin, which blocks final sigma1 maturation by preventing the release of Hsp90 from final sigma1, also inhibits Hsp90 phosphorylation. Taken together, these results demonstrate that Hsp90 phosphorylation is linked to its chaperoning function.

Animals↗
PubMed2001

Expression of the c-met proto-oncogene and its ligand, hepatocyte growth factor, in Hodgkin disease.

The receptor for hepatocyte growth factor (HGF) is a transmembrane tyrosine kinase that is encoded by the proto-oncogene c-met. Recently, c-MET was detected in Reed-Sternberg (RS) cells from Epstein-Barr virus-positive (EBV(+)) Hodgkin disease (HD). The c-MET, EBER-1, and LMP-1 expression in 45 lymph node biopsies and 12 bone marrow biopsies obtained from patients with HD was analyzed. In addition, HGF levels in serum samples from 80 healthy individuals and 135 HD patients in different phases of disease. In all 45 lymph node and 12 bone marrow samples examined, RS cells expressed c-MET but not HGF(+). These results were independent of the EBV infection. Interestingly, several HGF(+) dendritic-reticulum cells were found scattered around c-MET(+) RS cells. The mean +/- SEM serum HGF levels in HD patients at diagnosis and at the time of relapse were 1403 +/- 91 (95% confidence interval [CI], 1221-1585) and 1497 +/- 242 pg/mL (95% CI, 977-2017), respectively. HGF values were significantly higher than those of healthy individuals (665 +/- 28 pg/mL; 95% CI, 600-721; and P <.001 for both groups of patients) and of HD patients in remission (616 +/- 49 pg/mL; 95% CI, 517-714; and P <.001 for both groups of patients). A significant correlation was found between serum HGF levels and B symptoms at diagnosis (P =.014). In conclusion, this study indicates that HGF and c-MET constitute an additional signaling pathway between RS cells and the reactive cellular background, thereby affecting adhesion, proliferation, and survival of RS cells. Furthermore, the serum concentration of HGF in HD patients may be a useful tool in monitoring the status of disease.

Adolescent↗
PubMed2001

Transient ectopic expression of PTEN in thyroid cancer cell lines induces cell cycle arrest and cell type-dependent cell death.

The tumour suppressor gene PTEN/MMAC1/TEP1 has been implicated in a variety of human cancers and several inherited hamartoma tumour syndromes, including Cowden syndrome, which has a high risk of breast and thyroid cancer. We have previously reported that overexpression of PTEN in MCF-7 breast cancer cells induces cell cycle arrest and apoptosis. In this study, we analysed PTEN status at both the structural and expression levels and explored PTEN's growth-suppressive effects on thyroid. We found that 1 of 10 thyroid cancer lines [follicular thyroid carcinoma FTC-133] had hemizygous deletion and a splice variant IVS4--19G-->A in the remaining allele. Four lines, including FTC-133, express PTEN mRNA at low levels. In general, PTEN protein levels correlated with mRNA levels, except for NPA87, which has low levels of transcript and relatively high levels of PTEN protein. Transient expression of PTEN in seven thyroid cancer cell lines resulted in G(1) arrest in two well differentiated papillary thyroid cancer lines (PTCs) and both G(1) arrest and cell death in the remaining five lines, including three FTCs, one poorly differentiated PTC and one undifferentiated thyroid cancer. The level of phosphorylated Akt was inversely correlated with the endogenous level of PTEN protein and overexpression of PTEN-blocked Akt phosphorylation in all cells analysed. Our results suggest that downregulation of PTEN expression at the mRNA level plays a role in PTEN inactivation in thyroid cancer and PTEN exerts its tumour-suppressive effect on thyroid cancer through the inhibition of cell cycle progression alone or both cell cycle progression and cell death.

Adenocarcinoma, Follicular↗
PubMed2001

Molecular and clinical follow-up after stem cell transplantation for multiple myeloma.

Molecular follow-up has been carried out using immunoglobulin heavy-chain (IgH) gene finger-printing, a polymerase chain reaction (PCR)-based technique with a sensitivity of 0.1-0.01% (10(-3)-10(-4)), in 22 patients affected by multiple myeloma and submitted to stem cell transplantation (SCT). Twelve patients were submitted to either single or double autologous unselected peripheral blood progenitor cell transplantation, eight patients were submitted to autologous CD34+ immunoselected transplantation and two patients were submitted to allogeneic bone marrow (one patient) or peripheral blood CD34+ stem cell (one patient) transplantation. At diagnosis, all patients showed clonal CDIII rearrangement. The molecular analysis performed on leukapheresis products and CD34+ purified fractions proved to be contaminated by myeloma cells. During follow-up after autografting, all but one patient retained clonal rearrangement despite clinical complete remission (CR) in ten of them. These ten patients either relapsed (Rel) or showed progressive disease (PD) after transplantation; four of them died. Only one patient did not retain clonal rearrangement after autologous transplantation; she is currently alive in CR after a follow-up of 100 months. One patient submitted to allogeneic transplantation is currently alive with no evidence of the disease, but still retains clonal rearrangement after a follow-up of 47 months. Another patient died 4 months after transplantation after succumbing to fatal pneumonia showing myeloma progression.

Adult↗
PubMed2001

T-cell apoptosis induced by granulocyte colony-stimulating factor is associated with retinoblastoma protein phosphorylation and reduced expression of cyclin-dependent kinase inhibitors.

Peripheral blood progenitor cells (PBPC) mobilized by granulocyte colony-stimulating factor (G-CSF) promptly engraft allogeneic recipients after myeloablative chemotherapy for hematologic malignancies. Surprisingly, no exacerbation of acute graft-vs-host disease has been observed despite a 10-fold higher T-cell content in PBPC compared with bone marrow allografts. Because G-CSF can suppress T-cell proliferation in response to mitogens and enhance their activation-induced apoptosis, we examined the molecular mechanisms underlying G-CSF-induced immune dysfunction. Normal allogeneic lymphocytes were challenged with phytohemagglutinin in the presence of serum collected after G-CSF administration (postG) to healthy PBPC donors, and the expression of key components of the cell cycle and apoptotic machineries was investigated by flow cytometry and Western blotting. Lymphocyte stimulation was associated with collapse of mitochondrial transmembrane potential, hypergeneration of reactive oxygen intermediates, and activation of caspase-3 and DNA fragmentation. Lymphocytes were arrested in a G(1)-like phase of the cell cycle, as measured by G(1)-phase cyclin expression and bromodeoxyuridine (BrdUrd) incorporation. Cell tracking experiments confirmed the occurrence of a lower number of population doublings in postG compared with preG cultures. Unexpectedly, the phosphorylation state of the protein encoded by the retinoblastoma susceptibility gene (pRB) was unaltered in postG cultures, and the inhibition of cell cycle progression occurred without the recruitment of the cyclin-dependent kinase inhibitors p15(INK4B), p16(INK4A), and p27(Kip1). We eventually evaluated the ability of antioxidant/cytoprotectant agents to prevent the G-CSF-induced mitochondrial dysfunction and inhibition of cell cycle progression. Of interest, both N-acetylcysteine and amifostine reduced apoptotic cell death by 45% on average, inhibited the activation/processing of caspase-3, and increased BrdUrd incorporation in postG cultures. Based on these experimental findings, a model is proposed in which T-cell activation in the presence of serum immunoregulatory factor(s) induced by G-CSF is associated with a molecular phenotype mimicking the G(1)-S transition and consisting of pRB phosphorylation, lack of CDKI recruitment, and reduced cyclin-E expression. The putative relationship between lymphocyte mitogenic unresponsiveness and apoptosis induction would occur at the level of key molecules shared by the cell cycle and apoptotic machineries. Whether the G-CSF-mediated modulation of lymphocyte functions in vitro is beneficial in transplantation medicine remains to be determined.

Acetylcysteine↗