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M Daibata

Publications and source records attributed to M Daibata.

At least 37 records · Page 2Linked to original sources
PubMed1998

Integration of human herpesvirus 6 in a Burkitt's lymphoma cell line.

Human herpesvirus 6 (HHV-6) genome has been found in several human lymphoid malignancies, but configuration of the HHV-6 genome has not been well delineated. We established the HHV-6-positive, Epstein-Barr virus-negative Burkitt's lymphoma cell line Katata. In this study we investigated the status of the HHV-6 genome in Katata cells. Neither linear nor circular HHV-6 DNA was detected by Gardella gel analysis. The fluorescence in situ hybridization technique enabled us to directly visualize the integrated HHV-6 DNA at the single-cell level. Only one integrated site of viral DNA was detected in metaphase chromosomes and it was preferentially located at the long arm of chromosome 22 (22q13). Treatment of the cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or with calcium ionophore A23187 led to induction of the HHV-6 immediate-early gene as well as the late gene. Sodium n-butyrate also gave rise to expression of the HHV-6 genes. The TPA inducibility was synergistically enhanced when combined with A23187 or n-butyrate. Our study provides, for the first time, an in vitro model system of latent HHV-6 infection whose genome is integrated into host DNA of lymphoma cells.

Blotting, Southern↗
PubMed1997

Human herpesvirus 6 (HHV-6)-positive Burkitt's lymphoma: establishment of a novel cell line infected with HHV-6.

Human herpesvirus 6 (HHV-6) DNA has been detected in several human lymphoproliferative disorders. We report a case of HHV-6-infected Burkitt's lymphoma, from which a cell line, designated Katata, has been established. Katata cells had an immature B-cell phenotype with an L3 morphology and carried a t(8;14)(q24;q32) chromosomal abnormality. The HHV-6 DNA sequences were detected in both the patient's tumor cells and Katata cell line by polymerase chain reaction using three sets of primers that target different regions of HHV-6 DNA. The presence of HHV-6 DNA in Katata cells was also shown by Southern blot hybridization with the BamHI fragment of HHV-6. It is likely that the virus is in a latent state, since (1) virion-associated protein was not expressed in Katata cells, (2) transcriptional level of the immediate-early gene was very low, and (3) no viral particles were observed by electron microscopy. Katata cells were highly tumorigenic in nude mice and the tumor cells also contained HHV-6 DNA. We have successfully obtained several clonal lines by allowing the cells to form colonies in soft agarose and by the limiting dilution method. HHV-6 DNA was detectable in all 13 clones analyzed, suggesting that virtually all Katata cells are infected with HHV-6. This is the first report of a case of HHV-6+ Burkitt's lymphoma in the absence of Epstein-Barr virus. Furthermore, there has been no report of lymphoma cell lines that are persistently and nonproductively infected with HHV-6. The Katata Burkitt's lymphoma cell line, therefore, would provide a useful tool for studies of the mechanisms of HHV-6 latency and reactivation.

Animals↗
PubMed1997

Angioimmunoblastic lymphadenopathy with disseminated human herpesvirus 6 infection in a patient with acute myeloblastic leukemia.

A 47-year-old man with acute myeloblastic leukemia (AML) developed angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) 4 months after induction chemotherapy for AML. During a leukopenic period, the patient suffered from pericarditis with massive pericardial effusion in which human herpesvirus 6 (HHV-6) DNA was detected. Although complete remission of AML was achieved, fever persisted and atypical skin rash followed by generalized lymphadenopathy along with polyclonal hypergammaglobulinemia appeared. A diagnosis of AILD was made on a biopsy specimen of the inguinal lymph node. The patient died of fulminant hepatitis and the autopsy showed lymphomatous infiltrates involving the liver, bone marrow, lungs, spleen, kidneys and heart. HHV-6 DNA sequences were identified in the biopsy specimen of the lymph node and in the involved organ tissues. HHV-6 in this patient was variant B. It is known that HHV-6 can be reactivated in immunocompromised patients and causes severe complications. This unusual clinical course suggests that the immunosuppression associated with AML and the additional iatrogenic immunosuppression following cytopenia-inducing chemotherapy predisposed the patient to reactivated HHV-6 infection. The sequential detection of this virus before and after manifestation of AILD may support the evidence that HHV-6 infection could directly or indirectly trigger AILD. This is the first time that such a sequence of events has been reported to our knowledge. The possibility of HHV-6 infection should be considered when unexplained fever and generalized lymphadenopathy are seen in patients with leukemia, and administration of antiviral agents should be considered for the diagnostic evaluation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

High serum levels of CA125 and interleukin-6 in a patient with Ki-1 lymphoma.

We report a 53-year-old-man with an aggressive Ki-1 lymphoma who had high serum CA125, a marker protein of the epithelial ovarian cancer, and interleukin-6 (IL-6) concentrations. Both CA125 and IL-6 levels decreased after chemotherapy and elevated with disease progression. The patient's lymphoma cells obtained before chemotherapy grew continuously in vitro, were IL-6 dependent and were found to secrete CA125 in culture medium. These results indicate that CA125 can be secreted by Ki-1 lymphoma cells and IL-6 may promote the growth of Ki-1 lymphoma cells.

Aged↗
PubMed1996

Differential tumorigenicity between Epstein-Barr virus genome-positive and genome-negative cell lines with t(11;14)(q13;q32) derived from mantle cell lymphoma.

Epstein-Barr virus (EBV) genome has been detected in several human lymphoproliferative diseases, but the oncogenic function of EBV is not fully understood. We previously established EBV-positive (SP-50B) and EBV-negative (SP-53) cell lines with the t(11;14)(q13;q32) chromosome abnormality from a single patient with mantle cell lymphoma. Monoclonal EBV DNA in a circular episomal form was demonstrated in the SP-50B cells by Southern blot hybridization with the EBV-terminal fragment probe. SP-50B cells were positive for not only EBV-encoded nuclear antigen-1 (EBNA1) but also latent membrane protein-1 and EBNA2. None of the EBV-encoded proteins was expressed in SP-53 cells. The isogenic EBV-infected and EBV-free cell lines of neoplastic clones made it possible to examine a tumorigenic role of EBV. Only EBV-positive SP-50B cells possessed malignant phenotypes, such as growth ability in low serum, colony formation in soft agarose, and tumorigenicity in nude mice. On the other hand, a lymphoblastoid B-cell line established by infecting the patient's normal B lymphocytes in vitro with exogenous EBV had no tumorigenicity. These results suggested that EBV infection, if it occurred in neoplastic lymphoma cells, could play a role in acquisition of malignant phenotypes.

Animals↗
PubMed1994

Regulation of the BZLF1 promoter of Epstein-Barr virus by second messengers in anti-immunoglobulin-treated B cells.

Initiation of the Epstein-Barr virus (EBV) lytic cycle is dependent on the transcription of the BZLF1 gene. The BZLF1 gene promoter (Zp) was activated by crosslinking of cell surface immunoglobulin (Ig) with anti-Ig antibody in B cells, even in the absence of other viral genes. We identified several anti-Ig response elements within Zp, which were originally defined as 12-O-tetradecanoylphorbol-13-acetate (TPA) response elements (ZI repeats and ZII, an AP-1-like domain). Since anti-Ig crosslinking leads to activation of protein kinase C (PKC) and an increase in intracellular calcium level, Zp was tested for the response to these cellular factors. Treatment with calcium ionophore A23187 increased Zp activity. When the calcium ionophore was used in conjunction with TPA, a PKC activator, the Zp induction was synergistically enhanced. 1-(5-Isoquinolinyl sulfonyl)-2-methylpiperazine, an inhibitor of PKC, inhibited the anti-Ig inducibility of Zp. Calmodulin antagonists, compound R24571 and trifluoperazine, blocked the Zp activation with anti-Ig. These findings suggest that Zp responds directly to changes in the activity of both PKC and calcium/calmodulin-dependent protein kinase. Requirement of tyrosine kinase activation for the anti-Ig-mediated Zp activation was also demonstrated through the use of the tyrosine kinase inhibitor herbimycin. These cellular gene regulatory molecules induced with anti-Ig may cooperatively play an important part in achieving efficient EBV activation as seen with anti-Ig treatment in B cells.

Antibodies↗
PubMed1994

More efficient peptide binding to MHC class II molecules during cathepsin B digestion of Ii than after Ii release.

The binding of a T cell-presented peptide to MHC class II alpha,beta chains occurs as a concurrent process with the release of the associated invariant chain (Ii) by cathepsin B. Ii was digested by cathepsin B from solubilized, MHC class II alpha,beta,Ii complexes in the presence of N-hydroxysuccinimidyl-4-azidobenzoate-conjugated, 125I-labeled, influenza virus matrix (18-29) peptide. The peptide was crosslinked where it became bound. This HLA-DR1-restricted peptide bound about three times more efficiently to class II alpha,beta chains of DR1-positive B cells when present during cathepsin B digestion of Ii than when added afterward, also at pH 5.0. Binding was competed by similarly DR-restricted peptides. Cathepsin D cleaved Ii but did not enhance peptide binding. However, a trace level of cathepsin D, added to the assay for peptide binding in the presence of cathepsin B, further enhanced peptide binding about three times. These experiments support an hypothesis for the staged release of Ii fragments by cathepsin D and cathepsin B, catalyzing at one point the insertion of a peptide into the antigen binding site formed by class II alpha and beta chains.

Amino Acid Sequence↗
PubMed1994

Cathepsin B cleavage and release of invariant chain from MHC class II molecules follow a staged pattern.

A staged pattern of cathepsin B cleavage of MHC class II alpha, beta-bound invariant (Ii) chain and release of fragments was defined. Charge-loss mutations in the Ii chain were created in three clusters of cathepsin B putative cleavage sites R78K80K83K86, K137K143, and R151K154. Products of HLA-DR1 alpha, beta and wild type (WT) or mutant Ii genes, co-transfected into COS1 cells, were cleaved by cathepsin B and immunoprecipitated by antibodies either to MHC class II chains or to different Ii epitopes. In WT Ii, cathepsin B digestion generated two forms of p21 Ii fragments: a p21 recognized by anti-C-terminus antibodies and a p21 recognized by an antibody to a determinant near the N-terminus. C-terminal p21 was released from MHC class II alpha, beta chains upon its formation while N-terminal p21 remained associated with MHC class II alpha, beta chains. Mutations at K137K143 inhibited the generation of N-terminal p21 by cathepsin B. Mutation at R78K80K83K86 led to an accumulation of MHC class II-bound N-terminal p21 without the appearance of MHC class II-bound p14, p10, and p6 fragments after cathepsin B digestion. These results indicate that cathepsin B cleaves wild type Ii first about K137K143 to produce a MHC class II-associated N-terminal p21, which is then cleaved about R78K80K83K86 to generate p14, p10 and finally p6 which still associates with MHC class II alpha, beta chains. This pattern of staged cleavage and release of Ii might be related to a concerted mechanism regulating the binding of antigenic peptides to MHC class II molecules.

Amino Acid Sequence↗
PubMed1993

Epstein-Barr virus (EBV) replication and expressions of EA-D (BMRF1 gene product), virus-specific deoxyribonuclease, and DNA polymerase in EBV-activated Akata cells.

The replication of Epstein-Barr virus (EBV) and the expression of EBV early proteins were studied in the Burkitt's lymphoma cell line Akata stimulated with anti-human immunoglobulin G antibody (anti-IgG). Akata cells contained approximately 20 copies of EBV genome per cell as covalently closed, circular DNA. EBV DNA replication was observed at 6 hr and reached a maximal level at 24 hr after treatment with anti-IgG. Virion DNA was found in the culture medium at 12 hr. The kinetics of expression of BMRF1 gene product (early antigen diffuse component; EA-D) paralleled that of EBV deoxyribonuclease (DNase) and of DNA polymerase. Immunoblotting analysis showed that three polypeptides with molecular masses of 54, 52, and 49 kilodaltons (kDa) were recognized as EA-D components. The EBV DNase polypeptide was detected by immunoblotting at 53 kDa. The anti-EBV DNA polymerase antibody recognized 120- and 54-kDa polypeptides in the Akata cells. Immunoprecipitation followed by immunoblotting showed that EA-D and EBV DNase polypeptides were coimmunoprecipitated with anti-EBV DNase antibody and with anti-EA-D monoclonal antibody. These findings indicate that EA-D forms a complex with EBV DNase polypeptide. The molecules of EA-D, EBV DNase, and DNA polymerase appear to be closely associated together on the EBV replication.

Antibodies, Viral↗
PubMed1992

Phosphorylation of the Epstein-Barr virus BZLF1 immediate-early gene product ZEBRA.

Expression of the Epstein-Barr virus (EBV) BZLF1 gene product ZEBRA is a first step in the cascade of the virus-productive cycle. ZEBRA protein was detected by immunoblotting as a single band at 38 kDa in Akata cells after crosslinkage of membrane immunoglobulin G (IgG) with anti-IgG antibody. Immunoprecipitation of [32P]phosphate-labeled, anti-IgG-stimulated Akata cells with anti-ZEBRA antibody showed that ZEBRA was phosphorylated. Phosphoamino acid analysis demonstrated phosphorylation of serine, but not threonine or tyrosine, and tryptic-peptide mapping showed multiple phosphorylated peptides of ZEBRA. Treatment with 8-bromo cAMP and blockage of phosphodiesterase by theophylline in anti-IgG-stimulated cells increased the phosphorylation of three ZEBRA peptides. Incubation with 12-O-tetradecanoylphorbol-13-acetate (TPA) reduced the phosphorylation of these three ZEBRA peptides, while treatment with staurosporine, a protein kinase C (PKC) inhibitor, enhanced their phosphorylations. These data suggest that activation of PKC with TPA induces the ZEBRA dephosphorylation and that activation of cAMP-dependent protein kinase A enhances the ZEBRA phosphorylation at the specific sites.

Cell Line↗
PubMed1991

Intracellular localization of tyrosine kinase substrates beneath crosslinked surface immunoglobulins in B cells.

Crosslinking of surface immunoglobulins (sIg) in B cells led to the accumulation of submembranal phosphotyrosine, which was followed morphologically with the PY20 antiphosphotyrosine monoclonal antibody. Phosphotyrosine was not detected before sIg crosslinking. After sIg crosslinking, phosphotyrosine-containing proteins were redistributed from scattered small clusters near the plasma membrane to a juxtanuclear region, where immunofluorescent staining decreased with time. Double immunofluorescent staining of individual cells showed accumulation of phosphotyrosine beneath crosslinked sIg molecules at the cell surface. The sIg molecules were subsequently internalized more rapidly than the phosphotyrosine-containing molecules were redistributed. Genistein, a protein tyrosine kinase (PTK) inhibitor, blocked intracellular tyrosine phosphorylations but not cell surface patching of crosslinked sIg. When polyacrylamide beads coated with anti-Ig antibodies were added to the cells, intracellular tyrosine phosphorylation occurred beneath the regions of contact with the beads. This study provides an independent line of evidence confirming recent biochemical experiments that show that crosslinking of the antigen receptor induces PTK activity in B cells, and that components of the newly described sIg complex are among the PTK substrates. The surprising finding that the bulk of the induced phosphotyrosine remains associated with crosslinked sIg for many minutes suggests a role for complex local protein interactions in phosphotyrosine-mediated signal transduction through the antigen receptor of B cells.

Antibodies, Monoclonal↗
PubMed1991

Effect of genistein, a tyrosine kinase inhibitor, on latent EBV activation induced by cross-linkage of membrane IgG in Akata B cells.

The activation of phosphoprotein tyrosine kinases was studied in the regulation of EBV activation in Akata cells after cross-linking membrane IgG with anti-IgG. Protein tyrosine phosphorylation was induced in Akata cells after stimulation with anti-IgG, as determined by immunoblotting with the PY20 anti-phosphotyrosine mAb. The frequency of phosphotyrosine-activated cells was also measured by immunofluorescence with the PY20 antibody. Genistein, an inhibitor of tyrosine kinases, at non-cytotoxic doses blocked EBV activation, as measured in the induction of EBV Ag, EBV immediate early BZLF1 mRNA, and its protein product ZEBRA. Such inhibitions were reversed upon removing genistein from the cultures. Genistein inhibition of early Ag induction depended upon the time of addition of genistein after stimulation with anti-IgG. These findings indicate that activation of tyrosine kinase is required for EBV activation after cross-linking membrane IgG in Akata cells.

Antibodies, Anti-Idiotypic↗
PubMed1991

Establishment of a new Epstein-Barr virus nuclear antigen-positive B-cell line, BALL-2, with t(8;14) (q24;q32) chromosome abnormality from B-cell acute lymphoblastic leukemia, L2.

A new Epstein-Barr virus nuclear antigen (EBNA)-positive B-cell line, designated BALL-2, was spontaneously established from the peripheral blood of a 14-year-old boy with an EBNA-negative B-cell acute lymphoblastic leukemia (B-ALL), L2 in the French-American-British classification. The BALL-2 cell line grew in suspension with or without forming clumps of cells. The cultured cells exhibited lymphoid morphology with indented or lobulated nuclei, prominent nucleoli, and relatively abundant cytoplasm. Immunologic and cytogenetic studies showed that the BALL-2 cell line expressed the B-cell phenotype, CpIg+, SmIg+, CD19+, CD20+, CD38-, Ia+, and had chromosome translocation, t(8;14) (q24;q32). The same phenotypic and chromosome markers were present in original leukemia cells. These results indicated that the cell line was derived from the patient's leukemia cells. Unexpectedly, however, BALL-2 cells were positive for EBNA and EB virus DNA. Gene analysis of the BALL-2 cell line showed biallelic rearrangements in the JH locus. One of the JH rearrangement comigrated with a rearranged c-myc gene, indicating the translocation had occurred between JH and c-myc loci. The t(8;14) abnormality is a known chromosome marker of Burkitt lymphoma and L3 type ALL. Our studies revealed that this translocation and myc gene rearrangement can also be found in L2 type B-ALL.

Adolescent↗