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Biomedical subjects

D Liebowitz

Publications and source records attributed to D Liebowitz.

At least 19 recordsLinked to original sources
PubMed2000

Flavopiridol, a novel cyclin-dependent kinase inhibitor, in metastatic renal cancer: a University of Chicago Phase II Consortium study.

PURPOSE: Flavopiridol is the first cyclin-dependent kinase (cdk) inhibitor to enter clinical trials. Serum levels of flavopiridol obtained during phase I studies were sufficient to inhibit in vitro cancer cell growth. Because responses were observed in kidney cancer patients in the phase I trials, we performed a phase II trial of flavopiridol in this patient population. PATIENTS AND METHODS: Thirty-five minimally pretreated patients were accrued using a standard two-step mechanism. Flavopiridol (50 mg/m(2)/d) was administered by continuous infusion for 72 hours every 2 weeks, and response was evaluated every 8 weeks. Peripheral blood mononuclear cells (PBMCs) were collected at baseline, at completion of drug infusion, and on day 7 of the first therapy cycle, and cell cycle parameters after phytohemagglutinin and interleukin-2 stimulation were assessed. RESULTS: There were two objective responses (response rate = 6%, 95% confidence interval, 1% to 20%). The most common toxicities were asthenia, occurring in 83% of patients (grade 3 or 4 in 9%), and diarrhea, occurring in 77% of patients (grade 3 or 4 in 20%). Also, nine patients (26%) experienced grade 3 or 4 vascular thrombotic events, including one myocardial infarction, two transient neurologic ischemic attacks, four deep venous thrombosis, and two pulmonary emboli. Cell cycle studies did not reveal any effect of flavopiridol on stimulated PBMCs. CONCLUSION: Flavopiridol, at the dose and schedule administered in this trial, is ineffective in metastatic renal cancer. In addition to the diarrhea observed in phase I studies, we also observed a higher incidence of asthenia and serious vascular thrombotic events than expected.

Adult↗
PubMed1999

In vitro evaluation of flavopiridol, a novel cell cycle inhibitor, in bladder cancer.

PURPOSE: To determine the in vitro effects of flavopiridol on bladder cancer cell lines, immortalized urothelial cell lines, and normal urothelial cells well characterized for defects in p53, pRb, and p16. METHODS: Growth inhibition was assessed via an MTT assay and apoptosis via DAPI nuclear staining. Cell cycle analysis was performed via propidium iodide staining and fluorescent activated cell sorting (FACS). Multidrug-resistant cells were generated by continuous exposure to doxorubicin. RESULTS: Growth inhibition was not correlated with inactivation of p53, pRb, or p16. All cells experienced G2/M arrest within 24 h of flavopiridol exposure. Modest apoptosis was observed but required 72 h of continuous drug exposure to become evident. There was no obvious synergistic or antagonistic toxicity when flavopiridol was combined with radiotherapy or cisplatin dosed at the IC50 despite the observation that radiotherapy and flavopiridol led to more profound G2/M arrest than either agent alone. Doxorubicin-resistant cells, demonstrated to overexpress the MDR1 multi-drug-resistance protein were equally as sensitive to flavopiridol as the parental cells. CONCLUSIONS: Flavopiridol is a novel cell cycle inhibitor that may be a useful agent in bladder cancers with tumor suppressor gene alterations and/or multidrug resistance.

Antineoplastic Agents↗
PubMed1999

Adoptive T-cell therapy.

Adoptive immunotherapy, or the transfer of immunocompetent cells, has been shown to be a promising new strategy for treatment of a variety of malignancies, including leukemia and non-Hodgkin's lymphoma. The possibility that it may likewise benefit patients with multiple myeloma is now being explored by researchers in Europe and the United States. Two alternatives, one using donor leukocyte infusions (DLIs) and the other using autologous T cells, are described. In the Netherlands, researchers studied the use of DLIs in 17 patients with multiple myeloma who relapsed after bone marrow transplant (BMT). Of 16 evaluable patients, 10 (62%) responded, with six (37%) achieving a complete response (CR). After a median follow-up duration of 28 months, five patients relapsed and five remained in remission. Graft-versus-host disease (GVHD) developed in nine patients. In the United States, adoptive immunotherapy is currently being tested in eight patients with chemotherapy-resistant lymphoma. Autologous T cells were obtained prior to BMT and expanded using an anti-CD3/CD28 culture system. After BMT, the cells were reinfused into the patient. At approximately day 14, granulocyte levels began to recover in the six evaluable patients, and levels remained relatively stable over the posttreatment course. Two patients developed severe autoimmune toxicity, which responded to treatment in one and resolved spontaneously in the other.

Humans↗
PubMed1998

Epstein-Barr virus and a cellular signaling pathway in lymphomas from immunosuppressed patients.

BACKGROUND: Epstein-Barr virus (EBV) is associated with various malignant and benign lymphoproliferative disorders. It also efficiently transforms human B lymphocytes in vitro. The latent membrane protein 1 (LMP1) of EBV-infected cells plays a central part in this process by mimicking members of the family of tumor necrosis factor (TNF) receptors, thereby transmitting growth signals from the cell membrane to the nucleus through cytoplasmic TNF-receptor-associated factors (TRAFs). I sought evidence of LMP1-mediated signal transduction through TRAFs in tumor tissue from patients with post-transplantation lymphoproliferative disease and non-Hodgkin's lymphomas related to the acquired immunodeficiency syndrome (AIDS). METHODS: The association of LMP1 with TRAF-1 or TRAF-3 in tumor tissue was studied with double-immunofluorescence microscopy and immunoprecipitation assays. Evidence of LMP1-TRAF signaling was sought with an electrophoretic mobility shift assay for the nuclear factor-kappaB (NF-kappaB) transcription factor. RESULTS: Tumors from eight patients with post-transplantation lymphoproliferative disease, two patients with AIDS-associated non-Hodgkin's lymphoma, and three patients with endemic Burkitt's lymphoma were analyzed. Tumors from six of the patients with post-transplantation lymphoproliferative disease were positive for EBV and expressed LMP1; two samples were EBV-negative. Tumors from both patients with AIDS-associated non-Hodgkin's lymphoma were EBV-positive and expressed LMP1, whereas tumors from all three patients with Burkitt's tumors were positive for EBV but negative for LMP1. Double-immunofluorescence microscopy showed that LMP1 localized with and immunoprecipitated with TRAF-1 and TRAF-3 in all eight of the EBV-positive, LMP1-positive samples. An electrophoretic mobility shift assay revealed activated NF-kappaB in all eight EBV-positive, LMP1-positive samples as well, but not in either of the EBV-negative, LMP1-negative samples or in the three EBV-positive, LMP1-negative samples. CONCLUSIONS: LMP1-mediated signaling through the TRAF system has a role in the pathogenesis of the EBV-positive lymphomas that arise in immunosuppressed patients.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Nasopharyngeal carcinoma: the Epstein-Barr virus association.

The etiology of NPC is multifactorial and includes virological, genetic, and environmental factors as described. These factors can be synthesized into a model for the development of NPC through a multistep process. First, an individual may carry a genetic predisposed risk of developing NPC as suggested by the HLA linkage of the disease. The nasopharyngeal epithelium becomes infected early in life by EBV and viral gene expression eventually becomes limited to EBNA-1, LMP1, LMP2A/2B, and perhaps another viral protein not yet fully characterized. LMP1 has profound growth stimulating effects in vitro and may exert similar effects in the nasopharyngeal epithelium. As cells are stimulated to divide, the presence of EBNA-1 ensures that the viral genome will replicate and be distributed to progeny cells. Finally, to reach their full malignant potential, the dividing nasopharyngeal cells may acquire cellular genetic changes involving recessive TSGs on chromosome 3. The risk for developing secondary genetic alterations involving these genes may be increased by exposure to environmental carcinogens such as volatile nitrosamines in salted fish. Thus, NPC provides a model system for understanding the interactions of genetic, infectious, and environmental factors involved in oncogenic transformation. Recent developments in organoculture systems and transgenic animal technology should allow dissection at the molecular level of the specific mechanisms involved in this process.

Genes, Viral↗
PubMed1992

Phenotypes of Epstein-Barr virus LMP1 deletion mutants indicate transmembrane and amino-terminal cytoplasmic domains necessary for effects in B-lymphoma cells.

The Epstein-Barr virus (EBV) latent infection membrane protein 1 (LMP1) has previously been shown to cause EBV-negative B-lymphoma cells to grow in large clumps and to alter expression of surface activation and adhesion molecules (D. Wang, D. Liebowitz, F. Wang, C. Gregory, A. Rickinson, R. Larson, T. Springer, and E. Kieff, J. Virol. 62:1473-4184, 1988; F. Wang, C. Gregory, C. Sample, M. Rowe, D. Liebowitz, R. Murray, A. Rickinson, and E. Kieff, J. Virol. 64:2309-2318, 1990). In order to identify functional elements in the amino-terminal cytoplasmic domain and the first four transmembrane domains which were previously shown to be essential for LMP1 activity, three smaller deletion mutants were constructed and tested for their activity in B-lymphoma cells. The results of the present study indicate that the amino-terminal cytoplasmic domain, the first transmembrane domain, and the third and fourth transmembrane domains each contribute to LMP1's effects on B lymphocytes.

Amino Acid Sequence↗
PubMed1990

Epstein-Barr virus latent membrane protein (LMP1) and nuclear proteins 2 and 3C are effectors of phenotypic changes in B lymphocytes: EBNA-2 and LMP1 cooperatively induce CD23.

Latent Epstein-Barr virus (EBV) infection and growth transformation of B lymphocytes is characterized by EBV nuclear and membrane protein expression (EBV nuclear antigen [EBNA] and latent membrane protein [LMP], respectively). LMP1 is known to be an oncogene in rodent fibroblasts and to induce B-lymphocyte activation and cellular adhesion molecules in the EBV-negative Burkitt's lymphoma cell line Louckes. EBNA-2 is required for EBV-induced growth transformation; it lowers rodent fibroblast serum dependence and specifically induces the B-lymphocyte activation antigen CD23 in Louckes cells. These initial observations are now extended through an expanded study of EBNA- and LMP1-induced phenotypic effects in a different EBV-negative B-lymphoma cell line, BJAB. LMP1 effects were also evaluated in the EBV-negative B-lymphoma cell line BL41 and the EBV-positive Burkitt's lymphoma cell line, Daudi (Daudi is deleted for EBNA-2 and does not express LMP). Previously described EBNA-2- and LMP1-transfected Louckes cells were studied in parallel. EBNA-2, from EBV-1 strains but not EBV-2, induced CD23 and CD21 expression in transfected BJAB cells. In contrast, EBNA-3C induced CD21 but not CD23, while no changes were evident in vector control-, EBNA-1-, or EBNA-LP-transfected clones. EBNAs did not affect CD10, CD30, CD39, CD40, CD44, or cellular adhesion molecules. LMP1 expression in all cell lines induced growth in large clumps and expression of the cellular adhesion molecules ICAM-1, LFA-1, and LFA-3 in those cell lines which constitutively express low levels. LMP1 expression induced marked homotypic adhesion in the BJAB cell line, despite the fact that there was no significant increase in the high constitutive BJAB LFA-1 and ICAM-1 levels, suggesting that LMP1 also induces an associated functional change in these molecules. LMP1 induction of these cellular adhesion molecules was also associated with increased heterotypic adhesion to T lymphocytes. The Burkitt's lymphoma marker, CALLA (CD10), was uniformly down regulated by LMP1 in all cell lines. In contrast, LMP1 induced unique profiles of B-lymphocyte activation antigens in the various cell lines. LMP1 induced CD23 and CD39 in BJAB; CD23 in Louckes; CD39 and CD40 in BL41; and CD21, CD40, and CD44 in Daudi. In BJAB, CD23 surface and mRNA expression were markedly increased by EBNA-2 and LMP1 coexpression, compared with EBNA-2 or LMP1 alone. This cooperative effect was CD23 specific, since no such effect was observed on another marker, CD21.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens, CD↗
PubMed1989

Two related Epstein-Barr virus membrane proteins are encoded by separate genes.

The structures of the 2.3- and 2.0-kilobase Epstein-Barr virus (EBV) mRNAs, partially encoded within the EcoRI J fragment DNA of the viral genome, were determined by analysis of their cDNAs. Both mRNAs are transcribed across the fused terminal repeats of the EBV episome and consist of nine exons. The mRNAs are transcribed from different promoters and have a unique 5' exon from the U5 region of the genome but eight common exons from the U1 region. One principal open reading frame is present in each mRNA and is predicted to encode 54,000- and 40,000-dalton integral membrane proteins. This result was confirmed by in vitro translation of RNAs in the presence of canine pancreatic microsomes. The 2.3-kilobase mRNA is not expressed in Raji cells, owing to the deletion of the 5' regulatory and coding region of this gene, whereas neither mRNA is expressed in Namalwa cells, owing to inactivation as a result of integration of the EBV genome via the terminal repeats. Since these mRNAs are readily detected in largely latently infected cells and do not increase in abundance with EBV replication, these putative latent-infection membrane proteins are tentatively designated LMP-2A and LMP-2B, respectively.

Amino Acid Sequence↗
PubMed1989

Epstein-Barr virus latent membrane protein: induction of B-cell activation antigens and membrane patch formation does not require vimentin.

The latent membrane protein (LMP) of Epstein-Barr virus (EBV) forms patches associated with the vimentin intermediate filament system in EBV-transformed lymphoblastoid cell lines, EBV-infected Burkitt's lymphoma cells, and LMP-transfected, EBV-negative Burkitt's lymphoma cells. By gene transfer, LMP induces the expression of vimentin and B-cell activation antigens in EBV-negative Burkitt's lymphoma cells. We have now expressed LMP in an EBV-positive Burkitt's lymphoma cell line, Daudi, which does not express any LMP or vimentin. In these Daudi transfectants, LMP still formed plasma membrane patches in the absence of vimentin. LMP did not resist nonionic detergent extraction in Daudi cells as it does in vimentin-expressing cells. LMP still retained functional activity as judged by induction of B-cell activation antigens. These data indicate that LMP can form plasma membrane patches and induce B-lymphocyte activation independent of vimentin association.

Antigens, Differentiation↗
PubMed1989

Epstein-Barr virus latent infection membrane protein increases vimentin expression in human B-cell lines.

Latent Epstein-Barr virus (EBV) infection activates B-lymphocyte proliferation through mechanisms which are partially known. One approach to further delineate these mechanisms is to identify cellular genes whose expression is augmented in cells latently infected with EBV. Since EBV-negative Burkitt's lymphoma cells can be grown in continuous culture and EBV can establish growth-altering latent infection in these cells, some effects of EBV on B-lymphocyte gene expression can be studied by using this in vitro system. Pursuing this latter approach, we have used cDNA cloning and subtractive hybridization to identify a gene whose expression is increased after EBV infection. This gene encodes the cytoskeletal protein vimentin. Latent infection of established EBV-negative Burkitt's lymphoma cell lines with the transforming EBV strain, B95-8, resulted in dramatic increases in vimentin mRNA and protein levels, while infection with the nontransforming P3HR1 strain failed to do so. Vimentin induction was reproduced by the expression of the single EBV gene which encodes the latent infection membrane protein (LMP). An amino-terminal LMP deletion mutant did not induce vimentin. These results are of particular interest in light of the transforming potential of LMP, as demonstrated in rodent fibroblasts, and the interaction between vimentin and LMP observed in immunofluorescent colocalization and cell fractionation studies.

Antigens, Viral↗
PubMed1989

Philadelphia chromosome (Ph1)-positive acute lymphoblastic leukemia (ALL) is resistant to effective therapy for Ph1-negative ALL.

Amsacrine with high-dose cytarabine is effective therapy for Philadelphia chromosome (Ph1)-negative acute lymphoblastic leukemia (ALL). We examined the effectiveness of this regimen in 19 patients with Ph1-positive lymphoblastic leukemia. Four had an antecedent chronic phase of chronic myelogenous leukemia and 15 presented with ALL. There were no complete responders in either group. All 14 patients whose bone marrow could be assessed after completion of therapy showed persistent leukemia. We conclude that patients with Ph1-positive lymphoblastic leukemia have a disease that is resistant to treatment that is highly effective in patients with Ph1-negative ALL.

Adolescent↗
PubMed1988

Epstein-Barr virus latent infection membrane protein alters the human B-lymphocyte phenotype: deletion of the amino terminus abolishes activity.

A latent infection membrane protein (LMP) encoded by the Epstein-Barr virus (EBV) genome in latently infected, growth-transformed lymphocytes alters the phenotype of a human EBV-negative B-lymphoma cell line (Louckes) when introduced by gene transfer. These LMP-expressing cells exhibit increased homotypic adhesion due to increased expression of the adhesion molecules LFA-1 and ICAM-1. Increased homotypic adhesion could foster B-cell growth by facilitating autocrine growth factor effects. LFA-3 expression is also induced. The induction of LFA-3 and ICAM-1 results in increased heterotypic adhesion to T lymphocytes. This could result in more effective T-cell immune surveillance. Since LMP is expressed in EBV-transformed lymphocytes and has been demonstrated to transform rodent fibroblasts in vitro, a wide range of possible effects on B-lymphoma cell growth were assayed. In the Louckes B-lymphoma cell line, EBV LMP causes increased cell size, acid production, plasma membrane ruffling, and villous projections. Although cell proliferation rate was not greatly affected, the steady-state intracellular free calcium level, transforming growth factor beta responsiveness, and expression of the lymphocyte activation markers (CD23 and transferrin receptor) were increased. Thus, LMP appears to be a mediator of EBV effects on B-cell transformation. In transfected lymphoma cells, LMP localizes to patches at the cell periphery and associates with the cytoskeleton as it does in EBV-transformed B lymphocytes or in rodent fibroblasts. A partially deleted form of LMP (D1LMP) does not aggregate in patches or associate with the cytoskeleton and had little effect on B-cell growth. Thus, cytoskeletal association may be integral to LMP activity.

Antibodies, Monoclonal↗
PubMed1988

The truncated form of the Epstein-Barr virus latent-infection membrane protein expressed in virus replication does not transform rodent fibroblasts.

The gene encoding the Epstein-Barr virus membrane protein LMP, expressed in latent infection, is known to induce morphologic changes and some loss of contact inhibition in NIH 3T3 cells as well as profound loss of contact inhibition and of anchorage dependence in Rat-1 cells. Another form of LMP (D1LMP), deleted for the amino terminus and first four putative transmembrane domains of LMP, was recently shown to be expressed late in Epstein-Barr virus replication. We now demonstrate that D1LMP has no transformation-associated phenotypic effect in Rat-1 cells and does not significantly affect LMP-induced Rat-1 cell transformation. LMP activity and D1LMP inactivity in inducing anchorage-independent growth are not restricted to Rat-1 cells, but are also evident in BALB/c 3T3 cells. In both cell types, loss of contact inhibition and anchorage independence are acutely evident after LMP expression. Although newly transfected polyclonal Rat-1 or BALB/c cells have a lower agar cloning efficiency than established LMP-expressing clones, this is attributable, at least in part, to their lower average LMP expression, since among clones of transfected cells, higher cloning efficiencies correlated with higher levels of LMP. LMP is bound to the vimentin cytoskeletal network in rodent fibroblasts as it is in transformed lymphocytes, whereas D1LMP showed no detectable cytoskeletal binding, suggesting that cytoskeletal association may be integral to LMP-mediated cell transformation. LMP association with the cytoskeleton in latently infected, growth-transformed lymphocytes and LMP-transformed rodent fibroblasts, correlated with the lack of both rodent cell-transforming activity and cytoskeletal association of D1LMP supports working hypothesis that cytoskeletal association is important in LMP transforming activity.

Animals↗
PubMed1988

NSAID-induced mucosal injury.

Nonsalicylate, nonsteroidal anti-inflammatory drug (NSAID)-induced injury to the gastroduodenal mucosa may be responsible for significant ulceration and bleeding. The pathophysiology of gastroduodenal injury is reviewed and risk factors predisposing to NSAID injury are discussed. Finally, data are presented on the concurrent use of prostaglandin analogues and sucralfate in preventing mucosal injury.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

An Epstein-Barr virus transforming protein associates with vimentin in lymphocytes.

The Epstein-Barr virus (EBV) latent infection membrane protein (LMP) is likely to be an important mediator of EBV-induced cell proliferation, since it is one of the few proteins encoded by the virus in latent infection and since production of this protein in Rat-1 cells results in their conversion to a fully transformed phenotype. LMP was previously noted to localize to patches at the cell periphery. In this paper we examine the basis of LMP patching in EBV-infected, transformed lymphocytes. Our data indicate that LMP is associated with the cytoskeletal protein vimentin. Although LMP is fully soluble in isotonic Triton X-100 buffer, only 50% of it is extracted from cells in this solution. The rest remains bound to the cytoskeleton. LMP undergoes phosphorylation, and phosphorylated LMP is preferentially associated with the cytoskeleton. As judged by both immunofluorescence and immunoelectron microscopy, the vimentin network in EBV-transformed lymphocytes or EBV-infected Burkitt tumor lymphocytes is abnormal. Vimentin and LMP often colocalize in a single patch near the plasma membrane. In response to Colcemid treatment of EBV-infected cells, vimentin reorganizes into perinuclear rings, as it does in uninfected cells. LMP is associated with these perinuclear rings. Vimentin (or a vimentin-associated protein) may be a transducer of an LMP transmembrane effect in lymphoproliferation.

Burkitt Lymphoma↗
PubMed1986

Nonspecific chronic inflammatory bowel disease and AIDS.

A male patient with a 14-year history of UC (ulcerative colitis) had a helper-suppressor ratio (H/S) of 0.25 during a suspected exacerbation of chronic colitis. Prednisone and sulfasalazine were administered. Despite a transient clinical response he developed AIDS (acquired immune deficiency syndrome) and KS (Kaposi's sarcoma) within 3 months of initiating therapy.

Acquired Immunodeficiency Syndrome↗