Myeloperoxidase: an enzyme involved in intrinsic vincristine resistance in human myeloblastic leukemia

One of the differences between acute myeloblastic leukemia (AML) and acute lymphoblastic leukemia (ALL) is their sensitivity to vincristine. Although vincristine plays an important role in chemotherapeutic regimens for ALL, it does not possess clinically significant activity in AML. Horseradish peroxidase, a heme-centered peroxidase, oxidatively degrades Vinca derivatives and thereby abrogates their cytotoxic activity. This finding suggested that myeloperoxidase (MPO), a heme- centered peroxidase characteristically found in AML and not in ALL, might also degrade vincristine. We first examined the effects of MPO on vincristine in a cell-free system and demonstrated that this enzyme is capable of catalyzing vincristine's oxidative breakdown. We also observed that vincristine is more rapidly degraded in tissue culture by MPO-positive HL-60 cells than by a MPO-negative HL-60 subclone. The degree of MPO activity in these cell lines correlated in a positive manner with their degree of resistance to vincristine's cytotoxic activity. Moreover, the differential resistance to vincristine observed between these cell lines could be increased by increasing the concentration of H2O2 available to the enzyme. These data support the hypothesis that MPO-mediated oxidation of vincristine accounts in part for this drug's lack of activity in AML.     

Tumor necrosis factor-alpha induces activation of coagulation and fibrinolysis in baboons through an exclusive effect on the p55 receptor

Tumor necrosis factor-alpha (TNF-alpha) can bind to two distinct transmembrane receptors, the p55 and p75 TNF receptors. We compared the capability of two mutant TNF proteins with exclusive affinity for the p55 or p75 TNF receptor with that of wild type TNF, to activate the hemostatic mechanism in baboons. Both activation of the coagulation system, monitored by the plasma levels of thrombin-antithrombin III complexes, and activation of the fibrinolytic system (plasma levels of tissue-type plasminogen activator, and plasminogen activator inhibitor type I), were of similar magnitude after intravenous injection of wild type TNF or the TNF mutant with affinity only for the p55 receptor. Likewise, wild type TNF and the TNF p55 specific mutant were equally potent in inducing neutrophil degranulation (plasma levels of elastase- alpha 1-antitrypsin complexes). Wild type TNF tended to be a more potent inducer of secretory phospholipase A2 release than the p55 specific TNF mutant. Administration of the TNF mutant binding only to the p75 receptor did not induce any of these responses. We conclude that TNF-Induced stimulation of coagulation, fibrinolysis, neutrophil degranulation, and release of secretory phospholipase A2 are predominantly mediated by the p55 TNF receptor.     

Expression of the hematopoietic growth factor receptor FLT3 (STK- 1/Flk2) in human leukemias

Normal expression of the hematopoietic growth factor receptor FLT3 (STK- 1@Flk2) is limited to CD34+ stem/progenitor cells. We have evaluated the expression of FLT3 by RNase protection assay and Western blotting in 161 primary bone marrow (BM) samples from patients with leukemia. FLT3 RNA was found to be expressed at a higher level than in normal BM controls in 33 of 33 B-lineage acute leukemias, 11 of 12 acute myeloid leukemias (AMLs), and 3 of 11 T-cell acute leukemias (T-ALLs). Expression of FLT3 RNA was also observed in some cases of blast crisis CML. The FLT3 signal resulted from expression on the leukemic blasts, and was not caused by increased FLT3 expression on normal CD34+ stem/progenitor cells in the leukemic samples. To determine if FLT3 protein was also overexpressed, proteins were extracted from leukemic BM samples and screened by Western blotting with anti-FLT3 antisera. FLT3 protein was not detected in normal BM controls, but was found in 14 of 14 B-lineage ALLs, 36 of 41 AMLs, and 1 of 4 T-ALLs. Stimulation of patient samples with FLT3 ligand resulted in autophosphorylation of the FLT3 receptor, suggesting the receptor is functional in these cells. These data show that FLT3 RNA and protein are aberrantly expressed by AML and ALL cells in that CD34 expression and FLT3 expression are no longer synchronous, and suggest the possibility that overexpression of FLT3 could play a role in the survival and/or proliferation of malignant clones in acute myeloid and lymphoid leukemias.     

Associations of iron overload in Africa with hepatocellular carcinoma and tuberculosis: Strachan's 1929 thesis revisited

We analyzed data from the first study of iron overload in Africans, conducted between 1925 and 1928, to determine whether this common condition is associated with death from hepatocellular carcinoma and/or tuberculosis. In the original study, necropsies were performed on 714 adult blacks from southern Africa. Hepatic and splenic iron levels were measured semiquantitatively in 604 subjects and one of five iron grades was assigned. We examined death from hepatocellular carcinoma or from tuberculosis and the variables of age, sex, the presence of cirrhosis or other diagnoses that might be influenced by iron status, and tissue iron grades. Nineteen percent of men and 16% of women had the highest grade of hepatic iron. After adjustment for the presence of cirrhosis, hepatic iron grade was the variable most significantly associated with death from hepatocellular carcinoma (P = .021). The odds of death from hepatocellular carcinoma in subjects with the highest grade of hepatic iron was 23.5 (95% confidence interval, 2.1 to 225) times the odds in subjects with the three lowest grades. Splenic iron was the variable most significantly associated with death from tuberculosis (P <.0001). The odds of death from tuberculosis with the highest grade of splenic iron was 16.9 (4.8 to 59.9) times the odds with the two lowest grades. These findings suggest that iron overload in black Africans may be a risk factor for death from hepatocellular carcinoma and for death from tuberculosis.     

Western blot identification of platelet proteins that bind normal serum immunoglobulins. Characteristics of a 95-Kd reactive protein

We have found that Western blots (WBs) of whole platelets exposed to normal autologous or homologous sera commonly have bands at 90 to 95 (95) Kd, and less often at 100 to 110, 80 to 85, 60 to 75, and 50 to 60 Kd when developed with antiglobulins. The percentages of normal sera producing a 95-Kd band with anti-immunoglobulin G (IgG), -IgA, and -IgM are 85, 50, and 30, respectively. Antiglobulin reagents alone also produce background bands on WBs that we have shown correspond to levels of platelet-associated Igs (PAIgs) or their derivatives. Titers of 95 Kd-reactive IgG in normal sera range from 10 to 1,280 (85% less than or equal to 50), and the reaction appears to be partially F(ab')2- mediated. The 95-Kd protein is internal and differs in many respects from surface glycoproteins IIIa, IV, and V of similar apparent molecular weight. In thrombocytopenic patients there was no correlation between severity of thrombocytopenia or PAIgG of platelet eluates and corresponding serum titers of 95 Kd-reactive IgG. Some WB reactions previously reported as evidence of autoimmunity may represent normal variations in reactions of Igs with internal platelet proteins. These reactions may be immunospecific or analogous to nonspecific, partially F(ab')2-dependent binding of Igs by certain bacterial proteins.     

Polymorphism of adhesion molecule CD31 is not a significant risk factor for graft-versus-host disease

Mismatch between bone marrow transplant (BMT) patient and donor for an amino acid polymorphism within the adhesion molecule CD31 has recently been reported to increase risk for the development of graft-versus-host disease (GVHD). We further examined this association in a larger series of 301 BMT patients (227 with grade III/IV GVHD and 74 with grade 0 GVHD) and their HLA-identical sibling donors. CD31 genotypes were determined by polymerase chain reaction and restriction endonuclease digestion. The role of mismatch at the CD31 locus in the development of GVHD was assessed by analyzing the extent of CD31 identity and CD31 compatibility among the grade 0 GVHD and grade III/IV GVHD sibling pairs. No significant association between CD31 mismatch and the development of severe GVHD was detected in our overall patient population. Sixty-three percent of grade III/IV GVHD sibling pairs and 69% of grade 0 GVHD sibling pairs had CD31 genotypes that were identical (P = .36, odds ratio = 1.30). In addition, neither the grade 0 GVHD group (P = .10) nor the grade III/IV GVHD group (P = .27) differed significantly from the expected probability of identity between sibling pairs. Mismatch at the CD31 polymorphism between recipients and donors showed no consistent association with the development of GVHD. Current evidence does not support the value of CD31 mismatch in the selection of BMT donors.     

Increasing the use of second-line therapy is a cost-effective approach to prevent the spread of drug-resistant HIV: a mathematical modelling study

Introduction

Earlier antiretroviral therapy (ART) initiation reduces HIV-1 incidence. This benefit may be offset by increased transmitted drug resistance (TDR), which could limit future HIV treatment options. We analyze the epidemiological impact and cost-effectiveness of strategies to reduce TDR.

Methods

We develop a deterministic mathematical model representing Kampala, Uganda, to predict the prevalence of TDR over a 10-year period. We then compare the impact on TDR and cost-effectiveness of: (1) introduction of pre-therapy genotyping; (2) doubling use of second-line treatment to 80% (50–90%) of patients with confirmed virological failure on first-line ART; and (3) increasing viral load monitoring from yearly to twice yearly. An intervention can be considered cost-effective if it costs less than three times the gross domestic product per capita per quality adjusted life year (QALY) gained, or less than $3420 in Uganda.

Results

The prevalence of TDR is predicted to rise from 6.7% (interquartile range [IQR] 6.2–7.2%) in 2014, to 6.8% (IQR 6.1–7.6%), 10.0% (IQR 8.9–11.5%) and 11.1% (IQR 9.7–13.0%) in 2024 if treatment is initiated at a CD4 <350, <500, or immediately, respectively. The absolute number of TDR cases is predicted to decrease 4.4–8.1% when treating earlier compared to treating at CD4 <350 due to the preventative effects of earlier treatment. Most cases of TDR can be averted by increasing second-line treatment (additional 7.1–10.2% reduction), followed by increased viral load monitoring (<2.7%) and pre-therapy genotyping (<1.0%). Only increasing second-line treatment is cost-effective, ranging from $1612 to $2234 (IQR $450-dominated) per QALY gained.

Conclusions

While earlier treatment initiation will result in a predicted increase in the proportion of patients infected with drug-resistant HIV, the absolute numbers of patients infected with drug-resistant HIV is predicted to decrease. Increasing use of second-line treatment to all patients with confirmed failure on first-line therapy is a cost-effective approach to reduce TDR. Improving access to second-line ART is therefore a major priority.     

Acid hydrolases as markers of maturation in B-cell chronic lymphocytic leukemia

Malignant lymphocytes from 30 B-cell chronic lymphocytic leukemia (B- CLL) patients were studied for the cytochemical localization of two acid hydrolases, alpha-naphthyl acetate esterase (ANAE) and acid phosphatase (AT). The large majority of the cells stained for both ANAE and AP in 7 cases, for AP only in 18 cases, and were negative for both the enzymes in 5 cases. Ultrastructural analysis revealed that the cells that displayed more mature morphological features, such as well developed smooth and rough membrane compartments, were those positive for acid hydrolases. That ANAE and AP are expressed by B cells at late stage of maturation was confirmed by the finding that some lymphocytes and all of the plasmacytoid lymphocytes and plasma cells from Walderstrom's macroglobulinemia, from mixed cryoglobulinemia, and from multiple myeloma patients stained strongly for both ANAE and AP. Using the expression of acid hydrolases and certain ultrastructural features as markers of cell differentiation, it was possible to demonstrate a process of maturation within the single B-CLL clones with accumulation of the cells at stages that differed in the various cases.     

Social-cognitive functioning and social skills in patients with early treated phenylketonuria: a PKU-COBESO study

Objective

Early treatment of phenylketonuria (ET-PKU) prevents mental retardation, but many patients still show cognitive and mood problems. In this study, it was investigated whether ET-PKU-patients have specific phenylalanine (Phe-)related problems with respect to social-cognitive functioning and social skills.

Methods

Ninety five PKU-patients (mean age 21.6?±?10.2 years) and 95 healthy controls (mean age 19.6?±?8.7 years) were compared on performance of computerized and paper-and-pencil tasks measuring social-cognitive abilities and on parent- and self-reported social skills, using multivariate analyses of variance, and controlling for general cognitive ability (IQ-estimate). Further comparisons were made between patients using tetrahydrobiopterin (BH4, N?=?30) and patients not using BH4. Associations with Phe-levels on the day of testing, during childhood, during adolescence and throughout life were examined.

Results

PKU-patients showed poorer social-cognitive functioning and reportedly had poorer social skills than controls (regardless of general cognitive abilities). Quality of social-cognitive functioning was negatively related to recent Phe-levels and Phe-levels between 8 and 12 years for adolescents with PKU. Quality of social skills was negatively related to lifetime phenylalanine levels in adult patients, and specifically to Phe-levels between 0 and 7, and between 8 and 12 years. There were no differences with respect to social outcome measures between the BH₄ and non-BH₄ groups.

Conclusion

PKU-patients have Phe-related difficulties with social-cognitive functioning and social skills. Problems seem to be more evident among adolescents and adults with PKU. High Phe-levels during childhood and early adolescence seem to be of greater influence than current and recent Phe-levels for these patients.

     

Paternal origin of the rearranged major breakpoint cluster region in chronic myeloid leukemia

The Philadelphia chromosome, t(9;22), is present in virtually all cases of chronic myeloid leukemia (CML). It has previously been shown by cytogenetic studies that the rearranged chromosome 22 in patients with CML is exclusively maternal in origin. To address this issue at a molecular level, the major breakpoint cluster region (M-bcr) on chromosome 22 was examined using Southern blot assays and M-bcr Pvu II and Mae II restriction site polymorphisms in three CML patients. In all three cases, the rearranged allele was paternal in origin. These results indicate that the paternally derived M-bcr allele may also be involved in the M-bcr rearrangement.