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Biomedical subjects

I T Magrath

Publications and source records attributed to I T Magrath.

At least 37 records · Page 2Linked to original sources
PubMed1996

Switching viral latency to viral lysis: a novel therapeutic approach for Epstein-Barr virus-associated neoplasia.

We describe an EBV-driven lytic system (LySED) that can be used to specifically target therapy to EBV- containing tumors. This system takes advantage of the transactivating properties of EBNA-1, a latency protein expressed in all EBV-containing cells, to drive the expression of Zta, a gene sufficient for inducing the EBV lytic cycle. Thus, EBV provides both the target and the executor for mediating tumor-specific cell death, markedly increasing the specificity of the system. Transfection of EBV-positive cell lines with the LySED construct resulted in a switch to lytic cycle and subsequent cell death, even in the presence of an inhibitor of EBV thymidine kinase (acyclovir) without an increase in virion production. In contrast, growth of EBV-negative B-cell lines was not affected.

Antigens, Viral↗
PubMed1996

Absence of germline p53 mutations in familial lymphoma.

p53, a tumor suppressor gene, is frequently mutated in sporadic human cancer, and inherited mutations in p53 predispose to the early onset of cancer. p53 mutations occur frequently in sporadic lymphoma, and, in mice deficient for p53, lymphoma is the most common type of malignancy. Families with an increased incidence of lymphoma have been described, suggesting an inherited predisposition to lymphoma in these circumstances. To determine whether the predisposition to lymphoma in these families results from germline mutations in p53, we analysed exons 4-11 of the p53 gene in 35 individuals from 19 lymphoma-prone kindreds. We found no germline p53 mutations in any of the individuals tested. However, p53 expression assessed by immunohistochemistry, which suggests mutation, was observed in 35% of the tumor samples from the familial Hodgkin's disease cases and in 13% of the familial non-Hodgkin's lymphoma cases. These results suggest that p53 mutations do not play a critical role in heritable susceptibility to lymphoma. p53 may act by different, non-mutation related mechanisms in this setting, or be involved in late events in the pathogenesis of these tumors.

Adolescent↗
PubMed1996

Management of histologically aggressive lymphomas with a high risk of CNS disease.

The NHLs are a group of neoplasms that share a common target tissue, and are characterized by a high degree of biological and clinical heterogeneity. Adult lymphomas with a high propensity for CNS involvement comprise SNCC, lymphoma (ATLL), LL, and PCL of immunocompromised patients. Despite recently reported encouraging results, there is no standard therapy available for ATLL or PCL. In contrast, recent data from several groups suggest that the therapeutic outcome of SNCC lymphoma in adults is similar to the excellent results in children, when the same regimens are used, and the toxicity, at least for adults less than 60 years, is also similar. Although more intensive chemotherapy combined with CNS prophylaxis has extended the long-term survival of patients with LL, the treatment results in adults fall short of those for children.

Adult↗
PubMed1996

Severe atypical neuropathy associated with administration of hematopoietic colony-stimulating factors and vincristine.

PURPOSE: We have observed a severe atypical neuropathy (SAN) in patients with small non-cleaved-cell (SNCL) and large-cell lymphoma (LCL) treated with intensive chemotherapy and hematopoietic colony-stimulating factors (CSFs). The present analysis was undertaken in an attempt to identify factors associated with the development of this syndrome. PATIENTS AND METHODS: Fifty-four adult and pediatric patients consecutively treated according to the same chemotherapy protocol were included in the analysis. Low-risk patients received three cycles of cyclophosphamide, vincristine, doxorubicin, and high-dose methotrexate (CODOX-M) while in high-risk patients this drug combination was alternated with high-dose cytarabine (ara-C), etoposide, and ifosfamide (IVAC) for a total of four cycles. Twenty-eight patients received a CSF (granulocyte [G]- or granulocyte-macrophage [GM]-CSF), and 26 patients received no CSF. A statistical analysis, which included a logistic regression model, was undertaken to examine the importance of potential contributing factors to the development of SAN. RESULTS: SAN, which consisted of excruciating foot pain, usually associated with marked motor weakness, was observed in 12 patients. There was a highly significant association between the occurrence of this syndrome and the administration of CSFs, and an independent association with the cumulative dose of vincristine given in the first cycle of chemotherapy. Furthermore, the analysis suggested a synergistic effect between administration of the CSFs and vincristine in the genesis of this neuropathy. CONCLUSION: Our results indicate that CSFs can precipitate SAN when given in conjunction with vincristine. The development of SAN was associated most strongly with the cumulative dose of vincristine -- the size of individual doses and the number of doses given in cycle 1 were important to the extent that they influenced the cumulative dose.

Adolescent↗
PubMed1996

Treatment of patients with high grade non-Hodgkin's lymphomas and central nervous system involvement: is radiation an essential component of therapy?

We have retrospectively examined the outcome of 41 patients with high grade non-Hodgkin's lymphomas (NHL) and central nervous system (CNS) involvement who were treated with and without radiation at a single institution. Group I consisted of 25 patients with CNS involvement at presentation and Group II, of 16 with CNS involvement at first relapse. All 41 had systemic disease at diagnosis and received systemic and intrathecal chemotherapy. Response to therapy did not differ whether patients received concomitant radiation or no CNS radiation. Thirteen of 16 non-irradiated (81%) and 8 of 9 irradiated Group I patients (89%) achieved complete responses. Three of 4 non-irradiated (75%) and 7 of 12 irradiated (58%) Group II patients achieved complete responses. CNS relapse patterns were similar whether or not patients were irradiated, and regardless of radiation dose. Most patients (18) failed systemically; there were few (6) isolated CNS relapses. Survival was not improved by the addition of radiation. Of the 15 patients who achieved long term survival, 13 remained disease-free throughout their clinical course: 7 of these 13 patients (all Group I) did not receive CNS radiation and 6 (4 Group I, 2 Group II) did. In this series, in which 44% of patients who presented with CNS disease and 13% of those who relapsed with CNS became long term disease-free survivors, there was no discernable benefit from radiation, but increased toxicity was observed.

Adolescent↗
PubMed1996

Low incidence of CNS relapse with cranial radiotherapy and intrathecal methotrexate in acute lymphoblastic leukemia.

OBJECTIVES: To assess the incidence of isolated central nervous system (CNS) relapses in patients of acute lymphoblastic leukemia (ALL) treated with a protocol containing cranial irradiation and intrathecal methotrexate as CNS directed therapy. DESIGN: Prospective non randomized study. SETTING: Department of Medical Oncology, Tata Memorial Hospital. SUBJECTS: 623 children of ALL on MCP 841. METHODS: CNS relapse was diagnosed, if upon examination of the CSF, more than 50 cells/microliter were observed, or a count of 5 cells which were unequivocally lymphoblasts. RESULTS: The incidence of isolated CNS relapse was 1.75% with the use of this treatment. Age, sex, white blood cell count, platelet count, lactic dehydrogenase and immunophenotyping were not significantly related to isolated CNS relapse. CONCLUSION: A low incidence of isolated CNS relapse demonstrates the adequacy of the presymptomatic CNS therapy.

Adolescent↗
PubMed1995

Age, thymopoiesis, and CD4+ T-lymphocyte regeneration after intensive chemotherapy.

BACKGROUND: Inadequate reconstitution of CD4+ T lymphocytes is an important clinical problem complicating chemotherapy, human immunodeficiency virus infection, and bone marrow transplantation, but relatively little is known about how CD4+ T lymphocytes regenerate. There are two main possibilities: bone marrow-derived progenitors could reconstitute the lymphocyte population using a thymus-dependent pathway, or thymus-independent pathways could predominate. Previous studies have suggested that the CD45RA glycoprotein on CD4+ T lymphocytes is a marker for progeny generated by a thymus-dependent pathway. METHODS: We studied 15 patients 1 to 24 years of age who had undergone intensive chemotherapy for cancer. The absolute numbers of CD4+ T lymphocytes in peripheral blood and the expression of CD45 isoforms (CD45RA and CD45RO) on these lymphocytes were studied serially during lymphocyte regeneration after the completion of therapy. Radiographic imaging of the thymus was performed concomitantly. RESULTS: There was an inverse relation between the patients' ages and the CD4+ T-lymphocyte counts six months after therapy was completed (r = -0.92). The CD4+ recovery correlated quantitatively with the appearance of CD45RA+CD4+ T lymphocytes in the blood (r = 0.64). There was a higher proportion of CD45RA+CD4+ T lymphocytes in patients with thymic enlargement after chemotherapy than in patients without such enlargement (two-sided P = 0.015). CONCLUSIONS: Thymus-dependent regeneration of CD4+ T lymphocytes occurs primarily in children, whereas even young adults have deficiencies in this pathway. Our results suggest that rapid T-cell regeneration requires residual thymic function in patients receiving high-dose chemotherapy.

Adolescent↗
PubMed1994

Lymphocyte depletion during treatment with intensive chemotherapy for cancer.

Recently we have observed an increased incidence of opportunistic infections in patients treated with intensive chemotherapy for cancer. Because T-cell depletion is associated with similar clinical events in human immunodeficiency virus infection and after bone marrow transplantation, we have analyzed peripheral blood lymphocyte populations in a series of patients during treatment with intensive chemotherapy for cancer. Although neutrophil, monocyte, and platelet numbers consistently recovered to greater than 50% of pretreatment values after each sequential cycle of therapy, lymphocyte numbers did not recover within the same time period. B cells decreased rapidly from a mean value of 149 +/- 46/mm3 before chemotherapy to 4 +/- 1/mm3 during chemotherapy (P = .01). CD4+ T cells decreased from a mean of 588 +/- 76/mm3 before chemotherapy to 105 +/- 28/mm3 during chemotherapy (P = .0002) and CD8+ T cells decreased from a mean of 382 +/- 41/mm3 before chemotherapy to 150 +/- 46/mm3 during chemotherapy (P = .0009). Natural killer cell numbers did not show significant declines (171 +/- 30/mm3 before, 114 +/- 24/mm3 during, P = .19). Based on the history of opportunistic complications in patients with other disorders who display similar degrees of CD4+ T-cell lymphopenia and preliminary observations in this population, immune incompetence could surface as a dose-limiting toxicity for highly dose-intensive chemotherapy regimens.

Adolescent↗
PubMed1994

Binding and suppression of the Myc transcriptional activation domain by p107.

An amino-terminal transactivation domain is required for Myc to function as a transcription factor controlling cell proliferation, differentiation, and apoptosis. A complementary DNA expression library was screened with a Myc fusion protein to identify proteins interacting with this domain, and a clone encoding the Rb-related p107 protein was isolated. The p107 protein was shown to associate with Myc in vivo and to suppress the activity of the Myc transactivation domain. However, mutant forms of Myc from Burkitt lymphoma cells, which contain sequence alterations in the transactivation domain, were resistant to p107-mediated suppression. Thus, disruption of a regulatory interaction between Myc and p107 may be important in tumorigenesis.

3T3 Cells↗
PubMed1994

Regression of experimental Burkitt's lymphoma induced by Epstein-Barr virus-immortalized human B cells.

Epstein-Barr virus (EBV)-immortalized human B cells survive only transiently when injected subcutaneously into athymic mice, whereas Burkitt's lymphoma cells give rise to progressively growing subcutaneous tumors. In this study, we tested whether these Burkitt's tumors could be induced to regress via a bystander effect induced by EBV-immortalized B cells. Simultaneous inoculation of EBV-immortalized B cells and Burkitt's lymphoma cells in the same subcutaneous site resulted in tumors that regressed with necrosis and scarring. Similarly, simultaneous inoculation of EBV-immortalized B cells and Burkitt's lymphoma cells in separate subcutaneous sites resulted in regression of a proportion of the Burkitt's tumors. Furthermore, most of the established human Burkitt's tumors regressed with necrosis and scarring after intratumor inoculations with EBV-immortalized B cells. The EBV-immortalized B cells continued to exert this antitumor effect even when killed with irradiation. The experimental approach to Burkitt's lymphoma treatment described here exploits the ability of athymic mice to reject EBV-immortalized B cells to target an effective antitumor response to malignant cells normally incapable of eliciting it.

Animals↗
PubMed1994

Prospects for the therapeutic use of antisense oligonucleotides in malignant lymphomas.

Combinations of cytotoxic drugs, based almost entirely upon the results of empirical clinical trials, are the foundation of the modern management of the non-Hodgkin's lymphomas. While highly effective in the high-grade (particularly pediatric) lymphomas, and able to cure a significant fraction of intermediate-grade lymphomas, it has yet to be proven that patients with low-grade lymphomas can be cured by chemotherapy. Yet even if 100% of patients were potentially curable by chemotherapy, the significant medical cost with respect to both immediate and late toxicity is reason enough to search for radically different approaches to therapy. Of particular appeal is the possibility that therapy might be developed that is targeted to the very genetic lesions that are responsible for the pathogenesis of lymphomas. Such therapy should, by definition, be largely specific for the lymphoma cells, and hence devoid of the major side effects presently encountered. Recent advances in the understanding of the molecular basis of lymphomagenesis have provided sufficient information to begin to develop approaches of this kind. Here, I discuss the prospects for sequence-specific therapy, focusing specifically on antisense oligonucleotides. These short stretches of DNA bind specifically to RNA molecules and prevent their translation. If the targeted RNA molecules are specific to the tumor cells, or derived from pathogenetically relevant viral genomes, such therapy has at least the theoretical possibility of inhibiting tumor cell growth, or even killing tumor cells, without causing significant damage to normal cells.

Humans↗
PubMed1993

Variable IgH chain enhancer activity in Burkitt's lymphomas suggests an additional, direct mechanism of c-myc deregulation.

The deregulation of the c-myc gene in small non-cleaved cell lymphomas (SNCL) with 8;14 translocations is thought to be due to the juxtaposition of this gene with the IgH chain locus, but exactly how the Ig locus contributes to the deregulation is unclear. One widely considered hypothesis is that Ig gene enhancers, when moved near c-myc, might stimulate inappropriate transcription of this gene. To evaluate this hypothesis, we have tested the ability of the two known H chain enhancers, the JH-C mu intronic enhancer and the 3' alpha enhancer, to support transcription from c-myc promoters, by using transient transfection assays in a panel of 32 SNCL cell lines with 8;14 translocations. The activity of the JH-C mu intronic enhancer varied widely among the cell lines tested and correlated with the presence of nuclear factors binding to the E4/octamer regions of the enhancer. The 3' alpha enhancer was much less active than the intronic enhancer in all of our cell lines and seems unlikely to account for the c-myc deregulation (although the enhancer we tested was from the rat, because the human homologue is unidentified at present). A marked difference was also seen in the ability of individual cell lines to support transcription from the unenhanced c-myc constructs. Cell lines supporting the lowest enhancer activity tended to support the highest level of transcription from unenhanced c-myc promoters. The differences in transcription from c-myc promoters were confirmed by stably transfecting constructs containing c-myc promoters in SNCL cell lines. Our data strongly suggest that the importance of Ig enhancers for c-myc deregulation varies markedly in different cell lines and that, for many, trans-acting regulators of the c-myc promoters are as important or more important, than Ig enhancers in the deregulation of the c-myc gene.

Base Sequence↗
PubMed1993

Theophylline induced differentiation provides direct evidence for the deregulation of c-myc in Burkitt's lymphoma and suggests participation of immunoglobulin enhancer sequences.

Most of the evidence that supports the hypothesis that the c-myc gene is abnormally regulated in Burkitt's lymphoma (BL) is indirect. The putative abnormal expression of c-myc is likely, at least in part, to be a consequence of the usurpation of its regulatory sequences by immunoglobulin enhancer elements, which are invariably juxtaposed to c-myc by the translocations associated with this tumor (C. M. Croce, J. Erikson, A. Ar-Rushdi, D. Aden, and K. Nishikura, Proc. Natl. Acad. Sci. USA, 81: 3170-3174, 1984). We have developed a differentiation induction model system to examine this issue more directly. In a variety of non-BL cell lines, differentiation induction results in the down-regulation of c-myc (G. P. Studzinski, A. K. Bhandal, and Z. S. Brelvi, Proc. Soc. Exp. Biol. Med., 179: 288-295, 1985; Y. Matsui, R. Takahasi, K. Minara, T. Nakagawa, T. Koizumi, Y. Nakao, T. Sugiyama, and T. Fugita, Cancer Res., 49: 1366-1371, 1985; T. Mitchell, E. Sariban, and D. Kufe, Mol. Pharmacol., 30: 398-402, 1986; Z. S. Brelvi, and G. P. Studzinski, J. Cell. Physiol., 128: 171-179, 1986). Since BL is of B-cell origin, differentiation is associated with persistent or increased expression of immunoglobulin genes. Therefore, if c-myc and c-mu are coregulated in BL via immunoglobulin enhancer sequences, persistent or increased expression of the c-myc gene, rather than down-regulation, should occur in differentiated BL cells. Differentiation was induced in four BL cell lines with theophylline (7 x 10(-3) M), and mRNA was examined by Northern blot analysis. In all four BL lines studied (JD38, AG876, KK124, and Daudi), there was persistent or increased expression of both c-mu and c-myc genes (detected with a third exon c-myc probe), in contrast to the decreased expression of the c-myc gene observed in the three Epstein-Barr virus transformed lines studied (A3317, TC84, and CB34). In the BL cell line, JD38, the c-myc gene is truncated (the second and third exons are translocated to chromosome 14 while the first exon remains on chromosome 8). In this line, we demonstrated that theophylline induced differentiation results in down-regulation of the first exon while the level of expression of the translocated second and third exons remains unchanged or increases.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Burkitt's lymphoma between African and American types in Turkish children: clinical, viral (EBV), and molecular studies.

Seventy-two Turkish children with Burkitt's lymphoma (BL) observed during a period of 22 years (1968-1990) have been analysed retrospectively. The diagnosis was established histologically according to WHO criteria. BL represented 50% of NHL in this series. The patients were staged according to Ziegler's system. The median age of patients was 5.5 years with a sex (M/F) ratio of 2.1/1. The most common primary site of tumor involvement was the abdomen (69.4%), which was followed by facial tumors, in particular the jaw and orbit (49.9%). There were 21 cases with jaw (29.1%) and 15 cases with orbital involvement (20.8%) at initial presentation. The majority of the patients (84.4%) were in advanced stages (C and D) at initial diagnosis. Facial tumors observed in Turkish children with BL were more similar to African Burkitt's lymphoma than American or European cases. High titers of antibodies against VCA and EA of EBV were also seen in our recent cases of BL. Two main treatment regimens, namely, single agent chemotherapy with cyclophosphamide (CYX) (1968-1974) and three drug (COM) combination chemotherapy, were used consecutively (1974-1988). COM has been shown to produce better results than single agent therapy. The clinical presentation, mean age, and high antibodies (IgG) to EBV and preliminary molecular studies revealed that BL appears to be in between African and non-African types in Turkish children. This will be further elucidated by direct examination of tumor cells for EBV and investigation of the molecular characteristics of Turkish tumors. Such studies are presently under way.

Adolescent↗
PubMed1993

The role of gallium-67 tumour scintigraphy in patients with small, non-cleaved cell lymphoma.

Two hundred and thirty-four scintigraphic studies were performed in 34 patients (27 men, 7 women, age 17.3 +/- 7.7 years) with small, non-cleaved cell lymphoma who had follow-up for 3-96 months (mean 21.6 +/- 21.7 months). Whole-body scintigraphy was performed 48-72 h following i.v. injection of 370 MBq gallium-67 citrate. "Gold standards" for truth determinations were surgery, autopsy, histology, axial x-ray computed tomography, magnetic resonance imaging, ultrasonography and clinical follow-up. Overall, 181 of 234 studies were true negative. Eighty proven sites of disease had true positive 67Ga uptake (in 21 patients/37 studies). Nineteen sites (in 12 patients/15 studies) were false positive. In addition, 31 benign lesions were detected and interpreted correctly in terms of non-malignancy. Ten lymphoma sites (in 6 patients/10 studies) were missed by scintigraphy. Overall, sensitivity of gallium scintigraphy was 89% when calculated by sites and 79% when calculated by studies. Corresponding specificities were 91% and 92%, respectively. Positive predictive values were 81% (sites) and 71% (studies), and negative predictive values 95% (sites and studies). Thus, gallium scintigraphy proved to be a sensitive and specific method for staging and follow-up in patients with small, non-cleaved cell lymphoma.

Adolescent↗