Brent A. Schacter

Cytotoxic therapy-induced D-xylose malabsorption and invasive infection during remission-induction therapy for acute myeloid leukemia in adults.

PURPOSE To study the sequential changes in the intestinal absorption of an oral pentose probe, D-xylose, in patients receiving therapy for untreated acute myeloid leukemia (AML), and to correlate these changes to infectious morbidity. PATIENTS AND METHODS Serial D-xylose absorption studies were conducted in 110 consecutive adult patients admitted to a university-affiliated tertiary care hospital for remission-induction therapy for untreated newly diagnosed AML. Serial serum D-xylose levels were obtained 1 hour after a 5-g oral dose of D-xylose at baseline and weekly for 4 weeks until marrow recovery. These results were correlated with invasive infection using multivariate techniques. RESULTS The mean (+/- SEM) serum D-xylose levels were 0.88 +/- 0.03, 0.69 +/- 0.03, 0.58 +/- 0.02, 0.53 +/- 0.02, and 0.73 +/- 0.02 mmol/L at baseline and weeks 1 to 4, respectively (P < .0001, analysis of variance [AN-OVA]). Time to malabsorption varied with induction regimen (P = .007, log-rank test). Bloodstream infections during week 2 correlated with malabsorption (P = .007). Neutropenic enterocolitis correlated independently with induction regimen (P = .009), malabsorption at week 2 (P = .02), and the development of candidemia (P = .005). Hepatosplenic fungal infection correlated with induction regimen (P = .03), malabsorption at week 2 (P = .02), and fever at diagnosis (P = .003). Malabsorption was unrelated to the duration of severe neutropenia and the administration of parenteral nutrition. CONCLUSION Serial D-xylose absorption studies in subjects with AML produced a characteristic profile of cytotoxic therapy-related damage to the functional integrity of the intestinal epithelium that was regimen dependent, myelosuppression independent, and predictive for invasive infectious complications. Further study to validate these observations appears warranted.

Therapy of untreated acute myeloid leukemia in the elderly: remission-induction using a non-cytarabine-containing regimen of mitoxantrone plus etoposide.

PURPOSE The University of Manitoba Adult Acute Leukemia Study Group sought to examine the safety, efficacy, and impact on quality of life of a non-cytarabine-containing remission-induction regimen followed by intermediate-dose cytarabine (IDARA-C) postremission therapy for the management of untreated acute myeloid leukemia (AML) in patients age 60 to 80 years. PATIENTS AND METHODS Eligible patients received mitoxantrone 10 mg/m2 and etoposide 100 mg/m2 on days 1 to 5. Complete remitters received a single course of cytarabine 0.5 mg/m2 every 12 hours on days 1 to 6. Cytogenetic and immunophenotyping studies were performed at diagnosis and were examined for prognostic importance. The Functional Living Index-Cancer (FLI-C) was used in the longitudinal assessment of quality of life. RESULTS A total of 37 (55%) of 67 eligible patients achieved remission, 34 (92%) of whom did so with a single course. The induction mortality rate was 12%. The median disease-free and overall survival times were 8.4 and 9.2 months, respectively. CD34 stem-cell phenotype, poor performance status, and high cytogenetic complexity score were independent covariates of failure to achieve remission. Very complex karotype combined with CD34 stem-cell phenotype to predict induction death in 67% of cases (P = .0003). Cytotoxic therapy-related gut epithelial damage was maximal during weeks 2 and 3 of therapy. Complete remitters and partial responders exhibited significantly improved global FLI-C scores following completion of therapy. CONCLUSION Mitoxantrone plus etoposide was an effective and well-tolerated first-line induction regimen for AML in the elderly that should be studied further in comparison to the standard cytarabine/anthracycline-based therapy.

Active Therapy and Models of Care for Adolescents and Young Adults With Cancer

The reduction in the cancer mortality rate in adolescents and young adults (AYA) with cancer has lagged behind the reduction noted in children and older adults. Studies investigating reasons for this are limited but causes appear to be multifactorial. Host factors such as developmental stage, compliance, and tolerance to therapy; provider factors such as lack of awareness of cancer in AYA and referral patterns; differences in disease biology and treatment strategies; low accrual onto clinical trials; and lack of psychosocial support and education programs for AYA all likely play a role. Recommendations for change from a recent international workshop include education of physicians and patients concerning AYA cancer, improved cooperation between pediatric and adult centers, age‐appropriate psychosocial support services, programs to help AYA with issues relevant to them, dedicated AYA hospital space, improved accrual to clinical trials, the use of technology to educate patients and enhance communication between patients and the health care team, and ensuring that resident and fellowship training programs provide adequate education in AYA oncology. The longer term goal is to develop AYA oncology into a distinct subspecialist discipline within oncology. The ideal model of care would incorporate medical care, psychosocial support services, and a physical environment that are age‐appropriate. When this is not feasible, the development of “virtual units” connecting patients to the health care team or a combination of physical and virtual models are alternative options. The assessment of outcome measures is necessary to determine whether the interventions implemented result in improved survival and better quality of life, and are cost‐effective. Cancer 2011;117(10 suppl):2316–22.

Methene bridge carbon atom elimination in oxidative heme degradation catalyzed by heme oxygenase and NADPH-cytochrome P-450 reductase

Physiological heme degradation is mediated by the heme oxygenase system consisting of heme oxygenase and NADPH-cytochrome P-450 reductase. Biliverdin IX alpha is formed by elimination of one methene bridge carbon atom as CO. Purified NADPH-cytochrome P-450 reductase alone will also degrade heme but biliverdin is a minor product (15%). The enzymatic mechanisms of heme degradation in the presence and absence of heme oxygenase were compared by analyzing the recovery of 14CO from the degradation of [14C]heme. 14CO recovery from purified NADPH-cytochrome P-450 reductase-catalyzed degradation of [14C]methemalbumin was 15% of the predicted value for one molecule of CO liberated per mole of heme degraded. 14CO2 and [14C]formic acid were formed in amounts (18 and 98%, respectively), suggesting oxidative cleavage of more than one methene bridge per heme degraded, similar to heme degradation by hydrogen peroxide. The reaction was strongly inhibited by catalase, but superoxide dismutase had no effect. [14C]Heme degradation by the reconstituted heme oxygenase system yielded 33% 14CO. Near-stoichiometric recovery of 14CO was achieved after addition of catalase to eliminate side reactions. Near-quantitative recovery of 14CO was also achieved using spleen microsomal preparations. Heme degradation by purified NADPH-cytochrome P-450 reductase appeared to be mediated by hydrogen peroxide. The major products were not bile pigments, and only small amounts of CO were formed. The presence of heme oxygenase, and possibly an intact membrane structure, were essential for efficient heme degradation to bile pigments, possibly by protecting the heme from indiscriminate attack by active oxygen species.

Cyclic oscillations in rat hepatic heme oxygenase and δ-aminolevulinic acid synthetase following intravenous heme administration

Abstract Heme administration in vivo results in the suppression of synthesis of rat hepatic δ-aminolevulinic acid (ALA) synthetase and induction of rat hepatic heme oxygenase. Intravenous heme administration in vivo results in the appearance of cyclic progressively damped oscillations of both hepatic ALA synthetase activity and hepatic heme oxygenase activity. Heme oxygenase induction precedes in time the induction of ALA synthetase. ALA synthetase oscillations are observed in hepatic cell cytosol and mitochondrial fractions as well as in the total homogenate. Cycloheximide pretreatment abolishes both the ALA synthetase and heme oxygenase oscillations, while actinomycin D pretreatment has only a minimal effect on the induction of heme oxygenase. These results suggest that hepatic heme metabolism is closely regulated by rapid changes in the capacity to synthesize and catabolize heme, and the cyclic oscillations following intravenous heme may be a manifestation of the feedback regulation processes involved. This regulatory capacity is dependent on protein synthesis, and the primary site of regulation may be at the translational level on the endoplasmic reticulum.

Induction of δ-aminolevulinic acid synthetase in the kidney of chicks treated with porphyrinogenic drugs

Abstract 1. 1. The administration of allylisopropylacetamide induced an increase in δ-aminolevulinic acid synthetase activity in both kidney and liver of one-day-old chicks. 2. 2. The induction of δ-aminolevulinic acid synthetase in chick kidney was measurable by colorimetric assay and was comparable in activity to the increase observed in the liver. 3. 3. One of the most potent inducers of δ-aminolevulinic acid synthetase in chick liver, 3,5-dicarbethoxy-1,4-dihydrocollidine, did not increase the activity of chick kidney although the activity in liver was higher than that obtained with allylisopropylacetamide. Ferrochelatase activity was decreased in both liver and kidney by dicarbethoxy-1,4-dihyrocollidine.

Structural studies on bovine spleen heme oxygenase: Immunological and structural diversity among mammalian heme oxygenase enzymes☆

Heme oxygenase is an Mr 32,000 microsomal enzyme which catalyzes the rate-limiting step in the oxidative catabolism of heme to yield equimolar quantities of biliverdin IX alpha, carbon monoxide, and iron. In the present investigation, evidence is presented suggesting that immunochemical and structural differences exist between bovine spleen heme oxygenase and heme oxygenase enzymes from other mammalian species. Using an antibody directed against bovine spleen heme oxygenase, enzyme-linked immunosorbent assays, Western blotting experiments, and cell-free translation immunoprecipitation studies showed that bovine spleen heme oxygenase is only weakly immunochemically related to heme oxygenase from rat spleen. This observation was supported by the fact that a rat spleen heme oxygenase cDNA probe did not hybridize significantly to bovine spleen heme oxygenase mRNA in Northern analyses nor to restriction fragments containing the bovine heme oxygenase gene in Southern analyses. Tryptic peptides were prepared from bovine spleen heme oxygenase and the amino acid sequences of nine peptides comprising 94 amino acid residues were determined, providing the first information on the primary structure of bovine spleen heme oxygenase. Comparison of the sequences of these tryptic peptides with regions of the deduced amino acid sequences of rat spleen and human macrophage heme oxygenase revealed sequence similarities ranging from 55 to 100%. Several peptides displaying the highest degree of sequence similarity were found to occur in regions of the heme oxygenase molecule postulated to contain the heme binding site, indicating that despite the immunochemical and apparent structural differences between bovine spleen heme oxygenase and the rat and human enzymes, functionally important amino acid residues have been conserved in the evolution of mammalian heme oxygenase genes.

Heme oxygenase provides α-selectivity to physiological heme degradation

Abstract The isomeric composition of biliverdin formed by the degradation of heme by purified NADPH-cytochrome c reductase has been determined by high performance liquid chromatography. Methemalbumin heme yields a mixture of the four biliverdin IX isomers while myoglobin yields only the IX-α isomer of biliverdin. In both cases biliverdin is a minor product of the reaction. Addition of purified heme oxygenase to the methemalbumin NADPH-cytochrome c reductase system confers α-selectivity on the reaction and allows stoichiometric conversion of heme to biliverdin. Thus the role of heme oxygenase in enzymatic heme degradation appears to be to provide a suitable environment for quantitative conversion of heme to biliverdin in addition to conferring α-selectivity on the reaction.

Remission induction therapy of untreated acute myeloid leukemia using a non-cytarabine-containing regimen of idarubicin, etoposide, and carboplatin.

The safety and efficacy of idarubicin, etoposide, and carboplatin as remission induction therapy for patients younger than 60 years with untreated acute myeloid leukemia was studied as an alternative to standard regimens based on cytarabine plus anthracycline.

Prevalence of Alcohol Related Admissions to General Medical Units

The prevalence of alcohol related admissions to hospitals in Manitoba was examined in an investigation limited to the general medicine units of four representative hospitals within the province. All admissions during one-month periods were closely examined. In order to determine if an admission was related to alcohol, the investigators obtained permission from each patient to ask the attending physician to rate the degree to which they felt the admission was alcohol related, and intensively reviewed all charts. The percentage of alcohol related admissions was found to range from 6.38 percent to 14.93 percent on medical units. The disorders which alcohol related patients presented on admission tended to differ from those in the not-related category. At all hospitals, disorders of the gastrointestinal system were in the majority for the alcohol related group, while the not-related group presented more difficulty in the area of cardiovascular disorders. The cost which is associated with these alcohol related admissions is large, the highest being