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Biomedical subjects

Gideon Rechavi

Publications and source records attributed to Gideon Rechavi.

At least 73 records · Page 4Linked to original sources
PubMed2004

A pivotal role of cyclic AMP-responsive element binding protein in tumor progression.

Tumor microenvironment controls the selection of malignant cells capable of surviving in stressful and hypoxic conditions. The transcription factor, cyclic AMP-responsive element binding (CREB) protein, activated by multiple extracellular signals, modulates cellular response by regulating the expression of a multitude of genes. Previously, we have demonstrated that two cystein residues, at the DNA binding domain of CREB, mediate activation of CREB-dependent gene expression at normoxia and hypoxia. The construction of a dominant-positive CREB mutant, insensitive to hypoxia cue (substitution of two cystein residues at position 300 and 310 with serine in the DNA binding domain) and of a dominant negative CREB mutant (addition of a mutation in serine(133)), enabled a direct assessment, in vitro and in vivo, of the role of CREB in tumor progression. In this work, we demonstrate both in vitro and in vivo that CREB controls hepatocellular carcinoma growth, supports angiogenesis, and renders resistance to apoptosis. Along with the identification, by DNA microarray, of the CREB-regulated genes in normoxia and hypoxia, this work demonstrates for the first time that in parallel to other hypoxia responsive mechanisms, CREB plays an important role in hepatocellular carcinoma tumor progression.

Amino Acid Sequence↗
PubMed2004

Favorable early response of secondary chronic myeloid leukemia to imatinib.

Second malignant neoplasms are gradually becoming a recognized long-term complication of successful cancer treatment, and they usually respond poorly to conventional therapy and have an unfavorable outcome. Chronic myeloid leukemia (CML) is a clonal panmyelopathy, rarely seen in children with a specific cytogenetic aberration-the Philadelphia chromosome. The translocation generates an aberrant tyrosine kinase, which drives the malignant process in CML and which is also the molecular target for successful treatment of CML with imatinib. It is also exceedingly rare as a secondary malignant neoplasm in both adults and children. We report two cases of secondary CML. The first occurred after successful treatment for nasopharyngeal carcinoma in a child, and the second after treatment for lymphoma in an adolescent. Both patients had an excellent response to treatment with imatinib and attained complete cytogenetic remissions. We conclude that secondary CML may respond favorably to treatment with imatinib.

Adolescent↗
PubMed2004

Successful umbilical cord blood transplantation for Fanconi anemia using preimplantation genetic diagnosis for HLA-matched donor.

Fanconi anemia is a rare autosomal recessive disease characterized by bone marrow failure, developmental anomalies, and a high incidence of myelodysplasia and acute myeloid leukemia. Stem cell transplantation is the only curative treatment. In the absence of matched- sibling donor, an alternative mismatched family or matched unrelated donor can be used, but the results are inferior to the matched-sibling transplant and carry a high risk of morbidity and mortality. Preimplantation genetic diagnosis (PGD) has been increasingly used in recent years for mutation analysis for many genetic disorders and results in the birth of healthy children, saving the need for the termination of pregnancy of an affected embryo. The use of PGD for combined analysis of mutation and HLA-matching was reported for the first time in 2001. This enables the birth of an unaffected child who can serve as a donor for an affected sibling in need for stem cell transplantation. We report successful cord blood transplantation for a Fanconi anemia patient from his HLA-matched sibling, born after PGD that included mutation analysis for Fanconi anemia and HLA typing. PGD can provide an unaffected donor for a sibling affected by genetic disease in the absence of a compatible related donor.

Blood Donors↗
PubMed2004

Risk of venous thromboembolism in pediatric patients with brain tumors.

BACKGROUND: Venous thromboembolism (VTE) is a common event in adults with malignant brain tumors approaching 24% throughout the course of the disease. The high morbidity and mortality of this complication yielded several protocols for prevention of the disease in adults undergoing neurosurgery for brain tumors and possible primary prevention afterwards. We investigated the incidence and complications of VTE in pediatric neuro-oncology patients. PROCEDURE: We analyzed, retrospectively, the files of all consecutive patients under the age of 18 years who were hospitalized for the treatment of brain tumors between the years 1990 and 2003 in two leading, closely related, Israeli neuro-oncology centers. RESULTS: A total of 462 children were analyzed. Three hundred eighty-four patients underwent surgery and 78 were treated medically. Only three (0.64%) of the patients developed clinical episodes of VTE that were treated conservatively. Two of these patients developed intracranial bleeding while on secondary prevention for the disease. CONCLUSIONS: Although this study has considerable limitations in terms of retrospective design, heterogeneous group of patients and diagnoses, the changing awareness for thrombosis over the last 14 years and the inclusion of symptomatic VTE events only, our surprising data suggest that, as opposed to adults, the risk of clinically significant VTE in children with brain tumors may be exceedingly low. These findings set the stage for future forthcoming evaluations in view of the prospective studies that were done in adults and the possible significant implications for the prevention and possible etiologies of the disease.

Brain Neoplasms↗
PubMed2004

Determination of chromosome 13 status in bone marrow cells of patients with multiple myeloma using combined morphologic and fluorescence in situ hybridization analysis.

Deletion of chromosome 13q is believed to be an adverse prognostic marker in patients with multiple myeloma (MM). Interphase fluorescence in situ hybridization (I-FISH) is the method of choice for detection of chromosome 13q deletion (del13q). However, I-FISH has high false-positive rates attributed to a low percentage of plasma cells (PC), which are responsible for MM, in bone marrow (BM) samples from MM patients. In an attempt to overcome this problem, combined morphologic and I-FISH analyses were performed by a unique system that allows rapid automatic scanning of a large number of cells with simultaneous determination of the lineage of specific cells carrying del13q. The percentage of PC with del13q in BM samples from 40 MM patients was calculated. In addition, we established a useful prognostic ratio defined as the number of PC with del13q divided by the number of non-PC with del13q (PDP/PDNP), which may help to precisely define the putative role of del13q in prediction response of MM patients to new therapeutic compounds. We suggest this technique as a novel sensitive and specific method for detection of del13q in a minor PC population of MM patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Karyotypic evolution pathways in medulloblastoma/primitive neuroectodermal tumor determined with a combination of spectral karyotyping, G-banding, and fluorescence in situ hybridization.

Medulloblastomas (MBs) or primitive neuroectodermal tumors (PNETs) represent 15%-30% of pediatric brain tumors and are the most common brain tumors in children; they are rare in adults. Classification of these tumors is based on tissue morphology and is often controversial and problematic. Karyotypic analysis of these tumors using conventional cytogenetic methods is often a difficult process that may be hindered by a limited number of metaphase cells and poor chromosome morphology, often leading to only partial characterization of the chromosomal abnormalities. We investigated three primary human tumors and four cell lines (CHO-707, DAOY, D-341, and PFSK) utilizing a combination of conventional G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH) techniques. A high level of intratumoral heterogeneity was seen, with multiple numerical and structural chromosomal aberrations. The chromosomes most frequently involved in structural aberrations were chromosomes 1 (14 rearrangements), 7 (9 rearrangements), and 21 (9 rearrangements). The chromosomes most frequently involved in numerical aberrations were chromosomes 1, 12, and 13 (four cases) and chromosomes 14, 17, 19, 21, 22, and X (three cases). Numerous aberrant chromosomes were characterized only with the SKY analysis, and based on these findings multiple clones were identified, facilitating analysis of karyotypic evolution. The most frequent evolution mechanism was via polyploidization, followed by acquisition of additional numerical or structural aberrations (or both); however, the results showed that the karyotypic evolution process in these tumors is typically divergent and complex.

Adult↗
PubMed2004

Psychiatric morbidity and quality of life in children with malignancies and their parents.

Recent improvements in prognosis necessitate considering the emotional responses of children with malignant diseases and of their parents. This prospective study assessed 20 children and adolescents and their 36 parents within 2 weeks of diagnosis and after 1 and 6 months. Fifty-three percent exhibited moderate to severe posttraumatic symptoms right after diagnosis that decreased significantly after 1 month. Children with high-risk disease reported the most severe symptoms. Unexpectedly, children with low-risk disease exhibited more severe symptoms than those with moderate risk. Depressive symptoms decreased significantly during the period, but anxiety symptoms did not. Moreover, quality of life did not change. Twenty percent of parents exhibited posttraumatic symptoms on initial evaluation. Mothers' symptoms did not change, but fathers' symptoms decreased with those of their children. Several procedures and experiences were identified as causes of traumatic stress responses.

Adolescent↗
PubMed2004

Assessment of the response to imatinib in chronic myeloid leukemia patients--comparison between the FISH, multiplex and RT-PCR methods.

OBJECTIVE: The objective of this study was to evaluate the kinetics of molecular response in chronic myeloid leukemia (CML) patients treated with imatinib and to compare between the fluorescent in situ hybridization (FISH), multiplex and real-time quantitative RT-PCR (RQ-PCR) methods with this respect. METHODS: Molecular follow-up was carried out on 24 CML patients treated with imatinib. FISH analysis was performed according to the standard protocol. For RT-PCR the multiplex and RQ-PCR methods were used. RESULTS: Sixty-three percent and 52% of the patients achieved complete remission according to FISH and multiplex RT-PCR analyses, respectively. Seventy-five percent of the patients achieved remission within the first year of treatment. In 83% of the cases the FISH and RT-PCR results were concordant. RQ-PCR analysis was carried out on 32 of the 41 samples negative by multiplex RT-PCR but only nine were negative. All samples with a BCR-ABL/ABL ratio below 2% were also negative by FISH. There was an excellent correlation between the RQ-PCR and the FISH tests. CONCLUSIONS: Molecular remission according to FISH and multiplex RT-PCR can be achieved by imatinib within 1 yr of therapy. There is a good correlation between the FISH, multiplex and RQ-PCR results in terms of the kinetics of disappearance of the BCR-ABL transcript and the predictability of each method for the other. Although RQ-PCR is the most sensitive method for molecular follow-up, FISH and multiplex RT-PCR can be used as complementary tools, at least during the early period of treatment.

Adult↗
PubMed2004

Gene expression profiling of in vivo UVB-irradiated human epidermis.

BACKGROUND: Several recent studies have employed microarray profiling to study UVB-regulated gene expression in human skin. These studies are all based on UV-irradiated cultured cells that differ substantially from the intact tissues they are supposed to imitate. The purpose of the present study was to analyze the differential expression of UVB-regulated genes in intact human epidermis following in vivo UV irradiation. METHODS: The forearms of human volunteers were exposed to 4 MED of UVB in vivo, followed by removal of epidermal samples from exposed and non-exposed areas after 24 h. RNA samples were analyzed using oligonucleotide microarray (Affymetrix) technology analyzing 12 500 genes simultaneously. Verification of selected genes was performed by semi-quantitative reverse transcriptase polymerase chain reaction. RESULTS: Gene expression patterns clearly distinguished UV-exposed epidermis from unexposed skin. Classification of these genes into functional categories revealed that several biological processes are globally affected by UVB. Significant changes were seen in more than 800 genes. CONCLUSION: Human intact epidermis responds to a single low dose of in vivo UVB irradiation by differential regulation of numerous genes. Our results illustrate the power of global gene expression analysis of human epidermis to identify molecular pathways involved in UV-induced photodamage.

Adolescent↗
PubMed2004

The multiparametric scanning system for evaluation of minimal residual disease in hematological malignancies.

Combined simultaneous analysis of morphology, immunophenotyping and fluorescence in situ hybridization on the same cell offers advantages that may help to disclose the relevance of minimal residual disease (MRD) detection. Morphological analysis of small populations of cells related either to malignancy or recipient-associated markers may improve the accuracy of chimerism and MRD testing and delineate their clinical significance.

Cell Size↗
PubMed2003

Unique SDF-1-induced activation of human precursor-B ALL cells as a result of altered CXCR4 expression and signaling.

The mechanisms governing migration and extramedullary dissemination of leukemic cells remain obscure. In this study the migration and in vivo homing to the bone marrow of nonobese diabetic severe combined immunodeficient (NOD/SCID) mice injected with human precursor-B acute lymphoblastic leukemia (ALL) cells in comparison to normal CD34+ progenitors (both cord blood and mobilized peripheral blood) was investigated. Although migration and homing of both cell populations was dependent on stromal cell-derived factor 1 (SDF-1)/CXCR4 interactions, major differences in receptor expression as well as the migratory capacity toward various concentrations of SDF-1 were found. Furthermore, unlike normal CD34+ progenitors, in vivo homing of the leukemic cells was superior when recipient NOD/SCID mice were not irradiated prior to transplantation. In addition, we report differences in the adhesion molecules activated following SDF-1 stimulation, documenting a major role for very late antigen 4 (VLA-4), but not VLA-5 and lymphocyte function-associated antigen-1 (LFA-1), in homing of precursor-B ALL cells. Interestingly, Toxin-B and pertussis toxin inhibited the homing of the leukemic cells but not that of normal CD34+ progenitors or normal CD10+/CD19+ precursor-B cells, revealing differences in CXCR4 signaling pathways that are based on changes that acquired by the leukemic cells. Altogether, our data provide new insights into different SDF-1-induced signaling, activation, and consequent motility between normal CD34+ and precursor-B ALL progenitors, which may lead to improved clinical protocols.

Animals↗
PubMed2003

Genome-wide comparison of human keratinocyte and squamous cell carcinoma responses to UVB irradiation: implications for skin and epithelial cancer.

To gain insight into the transformation of epidermal cells into squamous carcinoma cells (SCC), we compared the response to ultraviolet B radiation (UVB) of normal human epidermal keratinocytes (NHEK) versus their transformed counterpart, SCC, using biological and molecular profiling. DNA microarray analyses (Affymetrix), approximately 12000 genes) indicated that the major group of upregulated genes in keratinocytes fall into three categories: (i). antiapoptotic and cell survival factors, including chemokines of the CXC/CC subfamilies (e.g. IL-8, GRO-1, -2, -3, SCYA20), growth factors (e.g. HB-EGF, CTGF, INSL-4), and proinflammatory mediators (e.g. COX-2, S100A9), (ii). DNA repair-related genes (e.g. GADD45, ERCC, BTG-1, Histones), and (iii). ECM proteases (MMP-1, -10). The major downregulated genes are DeltaNp63 and PUMILIO, two potential markers for the maintenance of keratinocyte stem cells. NHEK were found to be more resistant than SCC to UVB-induced apoptosis and this resistance was mainly because of the protection from cell death by secreted survival factors, since it can be transferred from NHEK to SCC cultures by the conditioned medium. Whereas the response of keratinocytes to UVB involved regulation of key checkpoint genes (p53, MDM2, p21(Cip1), DeltaNp63), as well as antiapoptotic and DNA repair-related genes - no or little regulation of these genes was observed in SCC. The effect of UVB on NHEK and SCC resulted in upregulation of 251 and 127 genes, respectively, and downregulation of 322 genes in NHEK and 117 genes in SCC. To further analyse these changes, we used a novel unsupervised coupled two-way clustering method that allowed the identification of groups of genes that clearly partitioned keratinocytes from SCC, including a group of genes whose constitutive expression levels were similar before UVB. This allowed the identification of discriminating genes not otherwise revealed by simple static comparison in the absence of UVB irradiation. The implication of the changes in gene profile in keratinocytes for epithelial cancer is discussed.

Apoptosis↗
PubMed2003

Inhibition of p53-induced apoptosis without affecting expression of p53-regulated genes.

Using DNA microarray and clustering of expressed genes we have analyzed the mechanism of inhibition of wild-type p53-induced apoptosis by the cytokine interleukin 6 (IL-6) and the calcium mobilizer thapsigargin (TG). Clustering analysis of 1,786 genes, the expression level of which changed after activation of wild-type p53 in the absence or presence of IL-6 or TG, showed that these compounds did not cause a general inhibition of the ability of p53 to up-regulate or down-regulate gene expression. Expression of various p53 targets implicated as mediators of p53-induced apoptosis was also not affected by IL-6 or TG. These compounds thus can bypass the effect of wild-type p53 on gene expression and inhibit apoptosis. IL-6 and TG activated different p53-independent pathways of gene expression that include up-regulation of antiapoptotic genes. IL-6 and TG also activated different differentiation-associated genes. The ability of compounds such as cytokines and calcium mobilizers to inhibit p53-mediated apoptosis without generally inhibiting gene expression regulated by p53 can facilitate tumor development and tumor resistance to radiation and chemotherapy in cells that retain wild-type p53.

Apoptosis↗
PubMed2003

Mutations in exon 2 of GATA1 are early events in megakaryocytic malignancies associated with trisomy 21.

Patients with Down syndrome (DS) frequently develop 2 kinds of clonal megakaryocytosis: a common, congenital, spontaneously resolving, transient myeloproliferative disorder (TMD) and, less commonly, childhood acute megakaryoblastic leukemia (AMKL). Recently, acquired mutations in exon 2 of GATA1, an X-linked gene encoding a transcription factor that promotes megakaryocytic differentiation, were described in 6 DS patients with AMKL. The mutations prevent the synthesis of the full-length GATA1, but allow the synthesis of a shorter GATA1 protein (GATA1s) that lacks the transactivation domain. To test whether mutated GATA1 is involved in the initiation of clonal megakaryoblastic proliferation or in the progression to AMKL, we screened 35 DS patients with either AMKL or TMD and 7 non-DS children with AMKL for mutations in exon 2 of GATA1. Mutations were identified in 16 of 18 DS patients with AMKL, in 16 of 17 DS patients with TMD, and in 2 identical twins with AMKL and acquired trisomy 21. Analysis revealed various types of mutations in GATA1, including deletion/insertions, splice mutations, and nonsense and missense point mutations, all of which prevent the generation of full-length GATA1, but preserve the translation of GATA1s. We also show that the likely mechanism of generation of GATA1 isoforms is alternative splicing of exon 2 rather than, or in addition to, alternative translation initiation, as was proposed before. These findings suggest that acquired intrauterine inactivating mutations in GATA1 and generation of GATA1s cooperate frequently with trisomy 21 in initiating megakaryoblastic proliferation, but are insufficient for progression to AMKL.

Alternative Splicing↗
PubMed2003

MYH9 spectrum of autosomal-dominant giant platelet syndromes: unexpected association with fibulin-1 variant-D inactivation.

The autosomal-dominant giant platelet syndromes (Fechtner, Epstein, and Sebastian platelet syndromes and May-Hegglin anomaly) represent a group of disorders characterized by variable degrees of macrothrombocytopenia with further combinations of neutrophil inclusion bodies and Alport-like syndrome manifestations, namely, deafness, renal disease, and eye abnormalities. The disease-causing gene of these giant platelet syndromes was previously mapped by us to chromosome 22. Following their successful mapping, these syndromes were shown to represent a broad phenotypic spectrum of disorders caused by different mutations in the nonmuscle myosin heavy chain 9 gene (MYH9). In this study, we examined the potential role of another gene, fibulin-1, encoding an extracellular matrix protein as a disease modifier. Eight unrelated families with autosomal-dominant giant platelet syndromes were studied for DNA sequence mutations and expression of the four fibulin-1 splice variants (A-D). A mutation in the splice acceptor site of fibulin-1 exon 19 was found in affected individuals of the Israeli Fechtner family, whereas no MYH9 mutations were identified. Unexpectedly, fibulin-1 variant D expression was absent in affected individuals from all eight families and coupled with expression of a putative antisense RNA. Transfection of the putative antisense RNA into H1299 cells abolished variant D expression. Based on the observation that only affected individuals lack variant D expression and demonstrate antisense RNA overexpression, we suggest that these autosomal-dominant giant platelet syndromes are associated, and may be modified, by aberrant antisense gene regulation of the fibulin-1 gene.

Base Sequence↗
PubMed2003

Clonal expansion and not cell interconversion is the basis for the neuroblast and nonneuronal types of the SK-N-SH neuroblastoma cell line.

The ability of neuroblastoma (NB) cells to interconvert bidirectionally, in vitro, from a neuroblast (N) to a nonneuronal (S) form is a well-studied biologic phenomenon of great clinical importance. Differences in the morphologic/ biochemical characteristics and gene expression patterns of the two cell populations have been investigated extensively in an effort to unravel the transdifferentiation process. Subcloning of the SK-N-SH NB cell line has led to two morphologically distinct cell types: SH-SY5Y (N-type) and SH-EP (S-type). Karyotypic analysis combined with G-banding and SKY showed a difference between these two cell types in the copy number of the 2p15 approximately pter segment, including the MYC-N gene. FISH analysis showed an extra copy of MYC-N present in all three lines: in SK-N-SH and SH-SY5Y the majority of cells had three copies of MYC-N, whereas in SH-EP the majority had two copies and only a small cell population with three copies was present. We suggest that the simultaneous coexistence of both cell types and the subsequent clonal expansion of one over the other is a possible explanation for the phenomenon observed and not the accepted interconversion model. According to the clonal expansion model, both N and S cells are simultaneously present in both cell lines. Under certain conditions, the less-aggressive S cells can dominate over the highly aggressive N cells, which eventually lead to the formation of the SH-EP and vice-versa.

Cell Differentiation↗