Topoisomerase II levels and drug sensitivity in adult acute myelogenous leukemia

The topoisomerase (topo) II-directed agents etoposide, daunorubicin (DNR), and amsacrine (m-AMSA) are widely used in the treatment of acute myelogenous leukemia (AML). In the present study, multiple aspects of topo II-mediated drug action were examined in marrows from adult AML patients. Colony-forming assays revealed that the dose of etoposide, DNR, or m-AMSA required to diminish leukemic colony formation by 90% (LD90) varied over a greater than 20-fold range between different pretreatment marrows. Measurement of nuclear DNR accumulation in the absence and presence of quinidine revealed evidence of P-glycoprotein (Pgp) function in 8 of 82 samples at diagnosis and 5 of 36 samples at first relapse, but the largest quinidine-induced increment in DNR accumulation (< 2-fold) was too small to explain the variations in drug sensitivity. Restriction enzyme-based assays and sequencing of partial topo II alpha and topo II beta cDNAs from the most highly resistant specimens failed to demonstrate topo II gene mutations that could account for resistance. Western blotting of marrow samples containing greater than 80% blasts revealed that the content of the two topo II isoenzymes varied over a greater than 20-fold range, but did not correlate with drug sensitivity in vitro or in vivo. In addition, levels of topo II alpha and topo II beta in 46 of 47 clinical samples were lower than in human AML cell lines. Immunoperoxidase staining showed that these low topo II levels were accompanied by marked cell-to- cell heterogeneity, with topo II alpha being abundant in some blasts and diminished or absent from others. There was a trend toward increasing percentages of topo II alpha-positive cells in pretreatment marrows that contained more S-phase cells. Consistent with this observation, treatment of patients with granulocyte-macrophage colony- stimulating factor for 3 days before chemotherapy resulted in increases in topo II alpha-positive cells concomitant with increases in the number of cells traversing the cell cycle. These observations have implications for the regulation of topo II in AML, for the use of topo II-directed chemotherapy, and for future attempts to relate drug sensitivity to topo II levels in clinical material.     

Pathogenesis of B cell lymphoma in a patient with AIDS

Lymphoma occurs at increased frequency in patients with the acquired immunodeficiency syndrome (AIDS). We studied, using serologic and molecular techniques, one such lymphoma for (a) evidence of infection with human T lymphotropic virus, type III (HTLV-III), and Epstein-Barr virus (EBV), (b) monoclonal rearrangement of immunoglobulin and T cell receptor genes, and (c) rearrangement of the c-myc oncogene. Immunoglobulin and T cell receptor gene studies demonstrated that the tumor was of monoclonal B cell origin. Similar to cases of Burkitt's lymphoma unrelated to AIDS, there were DNA sequences in the lymphoma that hybridized to EBV-specific probes and demonstrated evidence of c- myc rearrangement. HTLV-III sequences were not detected in the malignant B cells. The pathogenesis of some B cell neoplasms in patients with the syndrome may involve transformation by EBV and deregulation of oncogene expression without direct infection of the malignant B cells by HTLV-III.     

Dialysis Disequilibrium Syndrome: Brain death following hemodialysis for metabolic acidosis and acute renal failure – A case report

Background

Hepatitis C virus (HCV) infection is a significant problem among patients undergoing maintenance hemodialysis (HD). We conducted a prospective multi-center study to evaluate the effect of dialysis machine separation on the spread of HCV infection.

Methods

Twelve randomly selected dialysis centers in Tehran, Iran were randomly divided into two groups; those using dedicated machines (D) for HCV infected individuals and those using non-dedicated HD machines (ND). 593 HD cases including 51 HCV positive (RT-PCR) cases and 542 HCV negative patients were enrolled in this study. The prevalence of HCV infection in the D group was 10.1% (range: 4.6%– 13.2%) and it was 7.1% (range: 4.2%–16.8%) in the ND group. During the study conduction 5 new HCV positive cases and 169 new HCV negative cases were added. In the D group, PCR positive patients were dialyzed on dedicated machines. In the ND group all patients shared the same machines.

Results

In the first follow-up period, the incidence of HCV infection was 1.6% and 4.7% in the D and ND group respectively (p = 0.05). In the second follow-up period, the incidence of HCV infection was 1.3% in the D group and 5.7% in the ND group (p < 0.05).

Conclusions

In this study the incidence of HCV in HD patients decreased by the use of dedicated HD machines for HCV infected patients. Additional studies may help to clarify the role of machine dedication in conjunction with application of universal precautions in reducing HCV transmission.     

Homocysteine inhibits von Willebrand factor processing and secretion by preventing transport from the endoplasmic reticulum

Intracellular protein transport in endothelial cells is selectively inhibited by homocysteine, a thiol amino acid associated with both thrombosis and atherosclerosis. In a previous study, homocysteine decreased cell surface expression of the surface transmembrane glycoprotein thrombomodulin without decreasing secretion of another endothelial cell protein, plasminogen activator inhibitor-1. To define further the effects of homocysteine on protein transport, we examined the processing and secretion of the multimeric glycoprotein von Willebrand factor (vWF) in human umbilical vein endothelial cells. Incubation with 2 mmol/L homocysteine resulted in complete loss of vWF multimers and prevented asparagine-linked oligosaccharide maturation, propeptide cleavage, and secretion; these effects are consistent with impaired exit from the endoplasmic reticulum (ER). Dimerization was only partially inhibited, suggesting that homocysteine causes retention of provWF in the ER without preventing dimer formation. In pulse-chase incubations, intracellular provWF was degraded before exiting the ER in homocysteine-treated cells. Homocysteine also inhibited the processing and secretion of a carboxyl-terminal truncation mutant of human provWF expressed in rat insulinoma cells, indicating that retention in the endoplasmic reticulum can be mediated by regions of provWF apart from the carboxyl-terminal 20-Kd segment. These results suggest that retention of secretory proteins in the ER is regulated by redox mechanisms and imply that the intracellular transport of multiple endothelial cell proteins may be altered in patients with homocystinuria.     

Early functional effects of Clostridium difficile toxin A on human colonocytes

BACKGROUND & AIMS: Previous in vitro studies have shown that Clostridium difficile toxin A is able to directly affect the intestinal epithelial barrier function. The aim of this study was to examine the early effects of toxin A on mucin exocytosis and determine whether this toxin can induce the production of the chemokine interleukin 8 (IL-8) from human colonic epithelial cells. METHODS: Two model systems were used: the HT29-CI.16E colonic goblet cell line and primary cultures of human normal colonocytes. RESULTS: Toxin A exerted a rapid and dose- related inhibition of stimulated mucin exocytosis without altering baseline (constitutive) mucin exocytosis from HT29-CI.16E cells. Toxin A was also able to induce the secretion of IL-8 from both HT29-CI.16E cells and primary cultures of human normal colonocytes, as early as 2-3 hours of incubation. CONCLUSIONS: The results show that while toxin A is able to down-regulate stimulated mucin exocytosis, it is able to up- regulate the secretion of an important chemoattractant chemokine, IL-8. These modifications illustrate the ability of colonocytes to recruit inflammatory and immune cells that will eventually bring about major mucosal damage. (Gastroenterology 1997 Jun;112(6):1887-94)     

A retrospective analysis of therapy for acute graft-versus-host disease: initial treatment

We have reviewed results of therapy in 740 patients with grades II-IV acute graft-versus-host disease (GVHD) after allogeneic marrow transplantation. At the beginning of therapy, 597 patients (81%) had rash, 369 (50%) had liver dysfunction and 396 (54%) had gut dysfunction. Initial treatment was with glucocorticoids (n = 531), cyclosporine (n = 170), antithymocyte globulin (ATG) (n = 156) or monoclonal antibody (n = 3) either singly (n = 633) or in combination (n = 107). Parameters of GVHD severity in each organ were recorded weekly, and evaluation of response was made using values at the initiation of secondary treatment or, for patients without such treatment, using values on day 29 of primary treatment or the last recorded value before death, whichever occurred first. Minimal criteria for improvement or progression were defined for each organ, but no attempt was made to define liver or gut outcome if another complication such as venocclusive disease or infectious enteritis was present. Improvement rates were 43% for skin disease, 35% for evaluable liver disease and 50% for evaluable gut disease. Overall complete or partial responses were seen in 44% of patients. Multivariate analyses were carried out to identify patient, disease or treatment factors associated with likelihood of overall improvement and likelihood of response in at least one organ. A similar analysis was also carried out to identify covariates associated with time to treatment failure (defined as initiation of secondary therapy or death not due to relapse of malignancy). In all three models, GVHD prophylaxis using cyclosporine combined with methotrexate was associated with favorable GVHD treatment outcome compared to prophylaxis with either agent alone, and treatment with glucocorticoids or cyclosporine was more successful than treatment with ATG. Other factors associated with unfavorable outcome in the model of time to treatment failure and also entered in one of the response models were recipient HLA disparity with the donor, presence of a liver complication other than GVHD, and early onset of GVHD. Results of this analysis indicate that glucocorticoids represent the best initial therapy available for treatment of acute GVHD, although much room for improvement remains.     

Preclinical studies on the use of selective antibody-ricin conjugates in autologous bone marrow transplantation

Whole-ricin immunoconjugates were synthesized with the pan-T cell antibodies T101 and 3A1 and assayed in the presence of 0.1 mol/L lactose. Their toxicity for cell lines, peripheral blood T lymphocytes, and normal bone marrow progenitors was compared with that of whole ricin. In the presence of 0.1 mol/L lactose, normal cells and cell lines exhibited the following sensitivities to ricin: 8392 (human malignant B cell line) less than E rosette-positive lymphocytes less than bone marrow progenitors less than 8402 (human T ALL) less than CEM (human T ALL). Ricin sensitivities correlated with ricin binding as determined by immunofluorescence. In the presence of lactose, peripheral blood T cells were resistant to 0.1 nmol/L ricin, but a similar concentration of T101-ricin inhibited normal and malignant T colony formation by greater than 98%. 3A1-ricin was slightly less effective. At a conjugate concentration of 0.1 nmol/L, bone marrow progenitor colony formation was inhibited by 30% or less; T101-positive cells were at least tenfold more sensitive than normal progenitors. When mixtures of 10% CEM cells and marrow cells were incubated with T101-ricin, 95% of CEM colonies were killed, and 96% of marrow granulocyte/ macrophage progenitors survived. Some free ricin was released from immunotoxin-treated cells, producing minimal inhibition of protein synthesis or cell growth. We conclude that (a) normal blood cells and malignant cell lines exhibit varying degrees of ricin sensitivity in the presence of lactose; (b) T101-ricin is at least tenfold more toxic to T lymphocytes than to bone marrow progenitor cells and is effective in mixtures of normal and malignant cells; and (c) treatment of infiltrated marrow with anti-T cell immunotoxins should safely remove target T cells without excessively damaging normal progenitors or producing excessive free ricin. Anti-T cell, whole-ricin immunotoxins merit trials for autologous transplantation.     

Normal and leukemic SCID-repopulating cells (SRC) coexist in the bone marrow and peripheral blood from CML patients in chronic phase, whereas leukemic SRC are detected in blast crisis

Progress in understanding the abnormal regulation of hematopoiesis in chronic myelogenous leukemia (CML) would be facilitated if neoplastic cells, at all stages of the disease, could be studied in an animal model. In this report, we show that irradiated severe combined immunodeficient (SCID) mice can be transplanted with both normal (Philadelphia chromosome [Ph]-negative) and neoplastic (Ph+) cells from CML patients with either chronic or blast phase disease. Mice transplanted with peripheral blood (PB) or bone marrow (BM) cells from 9 of 12 chronic phase CML patients were well engrafted with human cells including multilineage colony-forming progenitors and CD34+ cells for at least 90 days posttransplantation. Repeated posttransplant injections of cytokines did not enhance the number of engrafted human cells. Interestingly, approximately 70% of the human progenitors found in the engrafted SCID BM were Ph-, suggesting that the growth of primitive normal cells is favored in this in vivo transplant model. A similar number of normal cells were found in mice transplanted with either PB or BM cells, suggesting that elevated numbers of primitive normal cells are present in CML PB. When cells from patients with CML in either myeloid or lymphoid blast crisis were transplanted into SCID mice, the BM of these mice was more rapidly repopulated and to a higher level than that observed with transplants of chronic phase cells. Moreover, all human colony-forming progenitors present in the BM of mice transplanted with blast crisis cells were Ph+, and the majority of cells showed the same morphological features of the blast crisis cells originally transplanted. These experiments provide a starting point for the creation of an animal model of CML and establish the feasibility of using this model for the future characterization of transplantable CML stem cells during disease progression.