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Biomedical subjects

R F Ambinder

Publications and source records attributed to R F Ambinder.

At least 91 records · Page 5Linked to original sources
PubMed1991

Biology of the lymphomas: cytogenetics, molecular biology, and virology.

Correlations between cytogenetics, histology, and clinical course continue to emerge in studies of non-Hodgkin's lymphomas. The previously recognized association between the t(14;18) chromosomal translocation and follicular lymphoma has been confirmed; abnormalities of chromosome 3 have correlated specifically with diffuse large cell lymphoma and abnormalities of chromosome 1 have been frequently present in T-cell lymphomas. Rearrangements involving 11q13 (bcl-1) occur most commonly in diffuse lymphocytic lymphoma of intermediate differentiation. Several new recurrent chromosomal abnormalities have also been described. The molecular fine structure of the t(8-14) chromosomal translocation in Burkitt's lymphoma appears to differ between endemic (Epstein-Barr virus-associated) and sporadic cases. In endemic Burkitt's lymphomas, the chromosomal breakpoint is usually far upstream of c-myc oncogene, leaving the regulatory region of the gene intact. In sporadic tumors, a large part of the regulatory region is separated from the gene and transcription is initiated at sites within the first intron. These data raise the possibility that Epstein-Barr virus may contribute to the deregulation of the c-myc gene and that this interaction may be required for tumorigenesis in the presence of some, but not all, types of c-myc damage arising from chromosomal translocations. Partner proteins that oligomerize with c-Myc have been identified in humans and mice (Max and Myn). The partners share with c-Myc the DNA-binding and coiled-coil motifs that are recognized in many other proteins and that function as transcriptional regulators. The Bcl-2 protein has been shown to be a mitochondrial inner membrane protein that blocks programmed cell death (apoptosis). Viral expression has been demonstrated in Epstein-Barr virus-associated Hodgkin's disease, and the spectrum of Epstein-Barr virus-associated lymphoproliferative disease has been expanded to include some T-cell malignancies. A new human herpesvirus has been associated with some cases of Hodgkin's disease.

Animals↗
PubMed1991

Functional domains of Epstein-Barr virus nuclear antigen EBNA-1.

The Epstein-Barr virus (EBV)-encoded latency product EBNA-1 is functionally pleiotropic, being required for replication of the episomal form of the EBV genome and having a role in the regulation of latency transcription. EBNA-1 is a direct DNA-binding protein, and both replication and transactivation are dependent on the interaction of EBNA-1 with its cognate DNA recognition sequences. To better understand EBNA-1 function, we have further characterized the DNA-binding domain of EBNA-1 and have examined the contributions of other domains of the protein to EBNA-1 transactivation activity. A Bal31 deletional analysis of the carboxy-terminal region of EBNA-1 identified a core DNA-binding domain located between amino acids 493 and 584. Column chromatographic, sedimentation, and cross-linking studies indicated that EBNA-1 exists in solution as a dimer. Mobility retardation assays using in vitro-translated variants of EBNA-1 showed that the active DNA-binding form of EBNA-1 is also a dimer. In short-term cotransfections, a pFRTK-CAT target containing EBNA-1-binding sites from the EBV origin of plasmid replication, ori-P, was transactivated by a carboxy-terminal EBNA-1 construction (amino acids 450 to 641) that also carried a c-myc nuclear localization signal. These reconstruction experiments demonstrated that a transactivation domain exists within the carboxy-terminal region of EBNA-1, that transactivation is more efficient when a nuclear localization signal is present, and that the natural karyophilic signal lies outside of the carboxy-terminal 191 amino acids. To identify the EBNA-1 nuclear localization signal, small oligonucleotides representing EBNA-1 sequences that encode clusters of basic peptides were transferred into two different vectors expressing cytoplasmic proteins (pyruvate kinase and herpes simplex virus delta IE175 protein) and the cellular locations of the fusion constructions were determined by immunofluorescence staining of transfected cells. In this way we identified a functional nuclear localization signal, Leu-Lys-Arg-Pro-Arg-Ser-Pro-Ser-Ser, encompassing amino acids 379 to 386 of the EBNA-1 protein.

Amino Acid Sequence↗
PubMed1991

Abundant expression of EBER1 small nuclear RNA in nasopharyngeal carcinoma. A morphologically distinctive target for detection of Epstein-Barr virus in formalin-fixed paraffin-embedded carcinoma specimens.

The highly restricted expression of the Epstein-Barr virus (EBV) genome in malignancy has limited the use of EBV detection methods applicable to formalin-fixed paraffin-embedded carcinoma specimens. In EBV-transformed lymphocytes very short nonprotein coding EBV transcripts (EBERs) are expressed in much higher abundance (10(7) copies per cell) than other EBV latency transcripts. Using a 3H riboprobe, the authors demonstrated EBER1 expression in NASOPHARYNGEAL CARCINOMAS (NPCs) as well as in parotid salivary gland. Recognition of EBER1 expression was facilitated by the intensity of hybridization and its characteristic morphology (nuclear with nucleolar sparing). EBER1 expression was not demonstrated in other epithelial malignancies arising from mucosal surfaces (oropharynx, uterine cervix) from which EBV shedding has been detected. Repeat study of the NPC specimens with digoxigenin-labeled probe yielded hybridization signal with subcellular morphologic detail and without background in a 12-hour procedure. Thus the EBER1 transcript is an appropriate target for in situ hybridization detection of EBV in formalin-fixed paraffin-embedded carcinoma specimens.

Carcinoma↗
PubMed1990

Detection of EBV gene expression in Reed-Sternberg cells of Hodgkin's disease.

EBV DNA has been detected by Southern blot hybridization in 20-25% of Hodgkin's disease tumor specimens and localized to the Reed-Sternberg cells by in situ hybridization. In the present investigation we used a 3H-labelled EBER I anti-sense RNA for in situ hybridization of archival formalin-fixed paraffin-embedded Hodgkin's disease specimens previously shown by Southern Blot hybridization to be EBV-positive. In 6 of 8 specimens neoplastic cells showed an intense signal in virtually all of the tumor cells. The background lymphocytes, eosinophils, plasma cells and histiocytes did not demonstrate significant hybridization. In each case hybridization tended to spare the nucleoli. Hybridization was detected in specimens with histologies of mixed cellularity and nodular sclerosis. The intensity of signal relative to background is better than that in previous studies utilizing 35S-labelled large internal repeat probes for EBV in Reed-Sternberg cells. The exposure time is one week in contrast to the 4-5 weeks reported by others for detection of EBV in Hodgkin's disease. Both increased relative intensity and shorter exposure requirements may be attributed to the very high number of EBER transcripts in the target cells. The demonstration that EBER I is expressed is consistent with a role for EBV in growth regulation of Reed-Sternberg cells and suggests that the virus is not merely a silent passenger in Hodgkin's disease.

Blotting, Southern↗
PubMed1990

Oligonucleotides for polymerase chain reaction amplification and hybridization detection of Epstein-Barr virus DNA in clinical specimens.

We designed synthetic oligonucleotide primers and hybridization probe for use in polymerase chain reaction (PCR) amplification and hybridization detection of Epstein-Barr virus (EBV) nucleic acid sequences. Primer sequences were chosen from the coding region for the Epstein-Barr virus nuclear antigen-1 (EBNA-1). PCR amplification and hybridization with these oligonucleotides was carried out on standard laboratory cell lines including African Burkitt's lymphoma and infectious mononucleosis derived cell lines, as well as cell lines recently established from clinical EBV isolates from bone marrow transplant recipients. All EBV cell lines tested were positive. No false-positives were detected with uninfected cell lines, human placental DNA or with other viruses. The sensitivity of the detection procedure was such that four copies of the EBV genome could consistently be detected in a background of 1 microgram of placental DNA. EBV was detected in DNA extracts from the peripheral blood mononuclear cells of two patients with infectious mononucleosis and one patient with viral-associated hemophagocytic syndrome. Three of 18 EBV seropositive patients without known ongoing EBV-associated illness undergoing ambulatory surgery also had EBV detected in DNA extracts from their peripheral blood mononuclear cells. EBV was detected in DNA extracts from lymphoma tissue from two patients with post-transplant lymphomas and two AIDS patients with primary CNS lymphomas. EBV was not detected in 12 B-cell lymphoma specimens from patients without history of immunocompromise. DNA extracts from formalin-fixed paraffin-embedded Hodgkin's tissues previously shown to be EBV positive by Southern blot were also demonstrated to be EBV positive by PCR. Thus, with the oligonucleotides described, PCR is applicable to the detection of EBV in a spectrum of clinical isolates. The broad specificity of these oligonucleotides for all strains of EBV tested is probably a function of the highly conserved sequence of the EBNA-1 DNA binding domain.

Antigens, Viral↗
PubMed1990

Definition of the sequence requirements for binding of the EBNA-1 protein to its palindromic target sites in Epstein-Barr virus DNA.

Interaction between the trans-acting DNA-binding protein EBNA-1 and cis-acting sequences in the ori-P region of Epstein-Barr virus DNA is required for maintenance of the viral plasmid state in latently infected B cells and is involved in the regulation of transcription during latency. In the Epstein-Barr virus genome, a total of 26 EBNA-1-binding sites occur within three clustered loci referred to as the family of repeats and dyad symmetry locus of ori-P and the separate BamHI-Q locus. Incubation of a bacterially expressed carboxy-terminal domain of EBNA-1 (28,000-molecular-weight EBNA-1 [28K EBNA-1]) with synthetic monomer and dimer consensus binding sites gave characteristic DNA-protein complexes in a mobility retardation assay. A similar approach with the naturally occurring Q locus confirmed that it contains two distinct but low-affinity binding sites. We then examined the precise sequence requirements for EBNA-1 binding, using a set of 30-base-pair oligonucleotides designed to contain symmetric point mutations within both halves of the palindromic target site. Analysis of all possible single substitutions between positions 1 and 10 in the consensus half-palindrome sequence revealed that positions 9 and 10 did not contribute to EBNA-1 binding and that considerable flexibility could be tolerated at positions 1 and 2. Positions 3 through 8 of the recognition site had the most stringent requirements, with transversions at these positions either reducing or eliminating binding. The relative spacing of the halves of the palindrome was also critical, since the addition or removal of 2 base pairs at the center of the sequence abolished binding. Similar results were obtained when a partially purified preparation of intact Raji EBNA-1 was substituted for the 28K EBNA-1, and the results were further supported by methylation interference studies which indicated contact points between EBNA-1 and the guanine residues at positions -8, -7, and +3 of the binding site. The three naturally occurring EBNA-1-binding loci have previously been shown to differ in their relative affinities for EBNA-1. The present study indicates that the sequence variations occurring within the family of repeats would not affect binding affinity, whereas certain base substitutions within the Q and dyad symmetry sites would be predicted to contribute to the observed lower affinities of these sites. An apparent Kd of 1.5 x 10(-11) M for binding of 28K EBNA-1 to a consensus recognition site was calculated from Scatchard analysis.

Antigens, Viral↗
PubMed1990

High-dose cytotoxic therapy and bone marrow transplantation for relapsed Hodgkin's disease.

Patients with Hodgkin's disease who have failed two or more chemotherapy regimens or who have relapsed after an initial chemotherapy-induced remission of less than 12 months are seldom cured with conventional salvage therapies. We studied the effect of high-dose cytoreductive therapy followed by bone marrow transplantation in 50 such patients with relapsed Hodgkin's disease. Twenty-one patients with histocompatibility locus antigen (HLA)-matched donors had allogeneic marrow transplants, one patient received marrow from an identical twin, and 28 patients without a matched donor received autologous grafts purged with 4-hydroperoxycyclophosphamide. Busulfan plus cyclophosphamide was the preparative regimen for the 25 patients who had received extensive prior irradiation, and the other 25 patients received cyclophosphamide plus total body irradiation. The overall actuarial probability of event-free survival at 3 years was 30%, with a median follow-up of 26 months. The event-free survival following transplantation was influenced by the number of chemotherapy failures and the patient's response to conventional salvage therapy prior to transplant. The 16 patients who were transplanted at first relapse, while still responsive to standard therapy, had a 64% actuarial probability of event-free survival at 3 years. Age, presence of extranodal disease, preparative regimen, and type of graft (autologous v allogeneic) were not significant prognostic factors. The majority of transplant-related deaths were from interstitial pneumonitis; inadequate pulmonary function, multiple prior chemotherapy regimens, and prior chest irradiation all appeared to increase the transplant-related mortality. These results suggest a role for marrow transplantation in a subset of patients with relapsed Hodgkin's disease who are unlikely to be otherwise cured but are still responsive to conventional-dose cytoreductive therapy.

Actuarial Analysis↗
PubMed1990

Allogeneic bone marrow transplantation for patients with high-risk acute lymphoblastic leukemia.

Seventy-four consecutive patients with high-risk acute lymphoblastic leukemia (ALL) were given cyclophosphamide (CY; 50 mg/kg on each of 4 days) plus total body irradiation (TBI; 300 rad on each of 4 days) followed by a human leukocyte antigen (HLA)-identical allogeneic bone marrow transplant (BMT). Eighteen patients in first complete remission (CR1), 36 in CR2, 16 in CR3, and four in CR4 were transplanted. Patients in CR1 were transplanted 1 to 8 months (median, 3 months) after attaining CR. All 18 patients in CR1 had one or more poor risk factors: age more than 18 (N = 17), initial leukocyte count greater than or equal to 20,000 (N = 11), Ph 1 chromosome (N = 2), delay in attaining CR more than 6 weeks (N = 8), or extramedullary disease (N = 1). Of those transplanted in CR2, 72% had relapsed on therapy. The 5-year event-free survival (EFS) rates for patients transplanted in CR1, CR2, and CR3 are 42%, 43%, and 25%, respectively, at median follow-up times of 57, 54, and 72 months, respectively. Children aged less than 18 years transplanted in CR2 have a 5-year EFS rate of 54%. All CR4 patients died early after transplant. The actuarial probability of relapse is 20%, 26%, and 48% for those transplanted in CR1, CR2, and CR3, respectively. Although there was substantial transplant-associated mortality, it decreased over the decade of the study (P = .01). This study indicates that BMT offers an attractive alternative to postremission chemotherapy in patients in CR1 with poor prognostic factors and in patients in second remission.

Adolescent↗
PubMed1990

Human lymphotropic viruses associated with lymphoid malignancy: Epstein-Barr and HTLV-1.

Epstein-Barr virus and HTLV-1 are both lymphotropic viruses, capable of immortalizing lymphocytes in vitro (Fig. 1). Both viruses have been sequenced and subjected to intense molecular biologic scrutiny, and in both cases genes believed to be important in lymphocyte immortalization have been identified. These viral genes are not homologues of cellular oncogenes, nor is there any evidence to suggest insertional mutagenesis. Rather, these genes alter the expression of a variety of cellular genes and, in so doing, alter the growth characteristics of the host cell. Infection with either virus is most likely to be asymptomatic, associated with a benign self-limited lymphoproliferation, or both, but in a small fraction of instances these benign lymphoproliferations give rise to a lymphoma or leukemia. In the case of the Epstein-Barr virus, a variety of cofactors have been identified that are important to the evolution of malignancy. These cofactors include immunosuppression in transplant recipients, cogenital immunodeficiency in the X-linked lymphoproliferative syndrome, human immunodeficiency virus infection in AIDS patients, and malaria in patients with endemic Burkitt's lymphoma. In the case of HTLV-1, cofactors have not been identified. Nonetheless, the importance of cofactors is suggested by the small fraction of the population infected by the virus who actually develop lymphoproliferative disease, and the long latency period between infection and the development of frank lymphoproliferative disease. In organ transplant recipients with lymphomas associated with Epstein-Barr virus infection, the EBV immortalizing/transforming genes are expressed in the malignant tissue. But in Burkitt's lymphoma and in adult T-cell leukemia/lymphoma, the EBV and HTLV-1 immortalizing/transforming genes are not detectably expressed. In Burkitt's lymphoma, it is suggested that the dysregulated myc gene renders the growth effects of Epstein-Barr virus latency genes superfluous. No comparable proto-oncogene translocation or activation has yet been identified in HTLV-1 lymphoma/leukemia.

Burkitt Lymphoma↗
PubMed1989

Allogeneic bone marrow transplantation after high-dose busulfan and cyclophosphamide in patients with acute nonlymphocytic leukemia.

Ninety-nine patients with acute nonlymphocytic leukemia (ANLL) received HLA-identical bone marrow transplants (BMTs) from sibling donors after preparation with high doses of busulfan and cyclophosphamide. Forty-nine patients were transplanted in first complete remission (CR), and 50 patients were transplanted in second and third CR and early relapse. Fifty-three received one of three regimens containing primarily low-dose cyclophosphamide (group I) for graft-v-host disease (GVHD) prophylaxis; since March 1983, 46 patients received intravenous (IV) cyclosporine (group II). After December 1983, only cytomegalovirus (CMV)-seronegative blood products were used in appropriate patients, and since April 1984 patients seropositive for herpes-simplex virus (HSV) and CMV received high-dose acyclovir prophylaxis. For patients transplanted in first CR, there was a significantly lower incidence of acute GVHD (P = .005) and deaths related to GVHD and interstitial pneumonitis (P = .001) in patients in group II. This was reflected in an improved Kaplan-Meier probability of disease-free survival (DFS) in the 22 patients transplanted in group II as compared with the 27 patients in group I (64% +/- 10% v 30% +/- 9%, P = .017). The probability of remaining in remission was slightly lower in group II (82% +/- 9% v 94% +/- 6%, P = .479). For patients transplanted in second and third CR and early relapse, the incidence of acute GVHD (P = .026) and deaths related to GVHD and interstitial pneumonitis was significantly lower in group II (P = .029); the probability of remaining in remission was also less (47% +/- 15% v 91% +/- 15%, P = .022). However, the probability of DFS was not significantly different between the two groups (26% +/- 10% v 35% +/- 18%, P = .957). We conclude that transplantation for patients in first CR who received IV cyclosporine therapy is effective treatment; patients with more refractory disease treated with the same cyclosporine regimen (group II) had a lower incidence of GVHD than those treated in group I, but survival did not improve because of an increase in the number of relapses and other nonleukemic complications.

Acute Disease↗
PubMed1987

Pathologic features of cytomegalovirus retinopathy after treatment with the antiviral agent ganciclovir.

Ganciclovir is a new antiviral compound (also called BW B759U, DHPG, BIOLF-62, and 2'NDG) that has been used for the treatment of cytomegalovirus (CMV) retinopathy in immunocompromised patients (bone marrow recipients or acquired immune deficiency syndrome [AIDS] victims). The authors studied the eyes of three AIDS patients with CMV retinopathy who died while receiving ganciclovir chemotherapy. Gross, microscopic, and ultrastructural studies of these cases showed varying degrees of retinal scarring and active CMV lesions at the margins of the scars. CMV antigens were localized in cells at all layers of retina at the border of the lesions and in isolated cells in a perivascular location within histologically normal appearing retina. These areas probably represent sites of recrudescence when the drug is discontinued. In situ hybridization using a cloned complementary DNA (cDNA) probe of human CMV corroborated the immunocytologic localization of the virus. Ultrastructural studies showed megalic syncytial cells containing mostly capsids exclusively in the cell nucleus. The cytoplasmic electron-dense membrane-bound bodies that have characterized untreated cases of CMV retinopathy were absent in the treated cases. An attempt to isolate CMV in tissue culture from the vitreous and retina of one of the cases yielded a negative result. Our results indicate that ganciclovir does not effectively eliminate CMV from the retina nor does it suppress expression of all viral genes. Ganciclovir appears to function by limiting viral DNA synthesis and subsequent packaging of viral DNA into infectious units, thereby acting as a virostatic chemotherapeutic agent.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Allogeneic, syngeneic and autologous marrow transplantation in the acute leukemias and lymphomas--Baltimore experiences.

Allogeneic bone marrow transplants (BMT) in acute lymphoblastic leukemia following cyclophosphamide (Cy) and total body irradiation (TBI) has resulted in disease-free survival (DFS) for CR1, CR2, and CR3 of 10/18 (56%), 16/30 (53%) and 4/17 (24%), respectively. Median follow-up of survivors was 25-43 months. One relapse was seen in CR1, 1 in CR2, and 6 in CR3. Allogeneic BMT in acute nonlymphoblastic leukemia (ANLL) following busulfan (Bu) resulted in DFS for CR1, CR2 + CR3 + early relapse of 21/47 (45%) and 13/41 (32%), respectively. Median DFS of survivors of all groups together was 36 months. DFS of all patients 20 years or less was 15/27 (56%) and 19/61 (31%) for ages 21-46. Three relapses of 47 (6%) were seen in CR1 and 6/41 (15%) in subsequent remission and early relapse. BMT of autologous BMT with 4-hydroperoxy-cyclophosphamide (4-HC) purged marrow in ANLL in CR1 (5), CR2 (32) and CR3 (9) following Bu + Cy resulted in DFS of 19/46 (41%) for 1-67 months (median 15 months). Twenty patients with prior risk non-Hodgkin's lymphoma received 4-HC-purged marrow following Cy + TBI. DFS was 10/20 (50%) for 1.4-9.5 years (median 2.9 years).

Acute Disease↗
PubMed1986

Autologous bone marrow transplantation in patients with acute nonlymphocytic leukemia, using ex vivo marrow treatment with 4-hydroperoxycyclophosphamide.

We studied 25 patients with acute nonlymphocytic leukemia in second remission (20 patients) or third remission (5 patients) in whom autologous bone marrow transplantation was performed with use of marrow incubated ex vivo with the alkylating agent 4-hydroperoxycyclophosphamide. Patients received intensive cytoreductive therapy with busulfan and cyclophosphamide or cyclophosphamide and total body irradiation, followed by an infusion of marrow that had been collected in remission, treated with 4-hydroperoxycyclophosphamide, and cryopreserved. Four patients died from bacterial or fungal sepsis within the first month after transplantation, and one patient with persistent marrow hypoplasia died from gram-negative sepsis 155 days after infusion with autologous marrow. In the remaining patients, peripheral-blood levels of neutrophils in excess of 0.5 X 10(9) per liter and platelet counts over 50 X 10(9) per liter were attained at median intervals of 29 and 57 days after transplantation, respectively. Nine patients had leukemic relapses at 73 to 316 days (median, 182 days) after infusion of autologous marrow, for an actuarial relapse rate of 46 percent. Eleven patients (eight in second remission and three in third) remained in remission at a median of more than 400 days (range, greater than 230 to greater than 1653 days) after transplantation. The observed disease-free survival after transplantation with autologous marrow treated with 4-hydroperoxycyclophosphamide compares favorably with the results of syngeneic or allogeneic transplantation in similar groups of patients.

Acute Disease↗
PubMed1986

Localized herpes simplex lymphadenitis.

Despite the marked immunocompromised status of most affected patients, visceral herpes simplex virus (HSV) infections in adults remain localized to the esophagus, with only rare examples of dissemination. Lymph node involvement with herpes simplex has been noted in three reported cases, but only in the context of a widespread fatal infection. This report describes two patients who presented with localized herpetic lymphadenitis documented by light microscopy, immunohistochemistry, and DNA hybridization technics.

Aged↗
PubMed1986

The vector homology problem in diagnostic nucleic acid hybridization of clinical specimens.

Nucleic acid hybridization techniques using cloned probes are finding application in assays of clinical specimens in research and diagnostic laboratories. The probes that we and others have used are recombinant plasmids composed of viral inserts and bacterial plasmid vectors such as pBR322. We suspected that there was material homologous to pBR322 present in many clinical samples. because hybridization occurred in samples which lacked evidence of virus by other techniques. If the presence of this vector-homologous material was unrecognized, hybridization in the test sample might erroneously be interpreted as indicating the presence of viral sequences. In this paper we demonstrate specific hybridization of labeled pBR322 DNA with DNA from various clinical samples. Evidence is presented that nonspecific probe trapping could not account for this phenomenon. In mixing experiments, it is shown that contamination of clinical samples with bacteria would explain such a result. Approaches tested to circumvent this problem included the use of isolated insert probes, alternate cloning vectors, and cold competitor pBR322 DNA in prehybridization and hybridization mixes. None proved entirely satisfactory. We therefore emphasize that it is essential that all hybridization detection systems use a control probe of the vector alone in order to demonstrate the absence of material with vector homology in the specimen tested.

Cytomegalovirus↗