Anemia and leukopenia following intravenous colloidal silver infusions-Clinical and hematological features, unique peripheral blood film appearance and effective therapy with supplemental oral copper and apheresis.

Alternative medical therapy with multiple intravenous colloidal silver infusions may cause severe illness, including profound copper deficiency-induced anemia and hepatic toxicity. No chelating agent for silver poisoning exists and effective therapy requires apheresis in combination with continuous administration of oral copper.

Acquired myelodysplasia or myelodysplastic syndrome: clearing the fog.

Myelodysplastic syndromes (MDS) are clonal myeloid disorders characterized by progressive peripheral blood cytopenias associated with ineffective myelopoiesis. They are typically considered neoplasms because of frequent genetic aberrations and patient-limited survival with progression to acute myeloid leukemia (AML) or death related to the consequences of bone marrow failure including infection, hemorrhage, and iron overload. A progression to AML has always been recognized among the myeloproliferative disorders (MPD) but occurs only rarely among those with essential thrombocythemia (ET). Yet, the World Health Organization (WHO) has chosen to apply the designation myeloproliferative neoplasms (MPN), for all MPD but has not similarly recommended that all MDS become the myelodysplastic neoplasms (MDN). This apparent dichotomy may reflect the extremely diverse nature of MDS. Moreover, the term MDS is occasionally inappropriately applied to hematologic disorders associated with acquired morphologic myelodysplastic features which may rather represent potentially reversible hematological responses to immune-mediated factors, nutritional deficiency states, and disordered myelopoietic responses to various pharmaceutical, herbal, or other potentially myelotoxic compounds. We emphasize the clinical settings, and the histopathologic features, of such AMD that should trigger a search for a reversible underlying condition that may be nonneoplastic and not MDS.

Evaluation of NHANES biomonitoring data for volatile organic chemicals in blood: application of chemical-specific screening criteria.

Available biomonitoring data for volatile organic chemicals (VOCs) in blood from the National Health and Nutrition Examination Survey (NHANES) (2003-2004) (CDC, 2009) were compared with recently derived screening biomonitoring equivalent (BE) values (Aylward et al., 2010). A BE is defined as the estimated concentration or range of concentrations of a chemical or its metabolites in a biological medium (blood, urine, or other medium) that is consistent with an existing health-based exposure guidance value. Blood concentrations of VOCs from the NHANES data set were compared with predicted screening BE values based upon a hazard quotient (HQ) for individual chemicals, and a hazard index (HI) approach for combined exposures. HI values for detected chemicals were generally at or below a value of 1, suggesting that the potential for deleterious effects is low. However, smoking was an important determinant of HI and HQ values. Detected levels of benzene in non-smokers were within the range of BE values corresponding to a 1 × 10(-6)-1 × 10(-4) range for upper-bound cancer risk; in smokers, levels of benzene were at the upper end of or exceeded this range. For VOCs that were not detected in the NHANES sampling, analytical detection limits were generally sufficiently sensitive to detect concentrations consistent with existing non-cancer and cancer risk-based exposure guidance values. Interpretations of measured blood concentrations of VOCs must be made with caution due to the substantial within-individual, within-day fluctuations in levels expected due to the rapid elimination of VOCs.

United States Voluntary Children's Chemical Evaluation Program (VCCEP) risk assessment for children exposed to benzene.

As part of the Voluntary Children's Chemical Evaluation Program (VCCEP) program, a risk assessment was performed to evaluate the risks to children from environmental benzene exposures. This paper summarizes this risk assessment. Risk was characterized using two distinct methods: USEPA's default type of risk assessment, which used the Reference Dose (RfD) and Cancer Slope Factor (CSF) to characterize non-cancer and cancer risks, as well as a Margin of Safety (MOS) approach that utilized a point of departure (POD). The exposures for most scenarios evaluated in this VCCEP risk assessment are lower than both the cancer and non-cancer PODs by several orders of magnitude, indicating a large MOS and corresponding low potential for toxicity at these exposures. The highest benzene exposures likely experienced by children, associated with the lowest MOS, are from cigarette smoke. In addition, the potential for age-related differences in the sensitivity towards benzene-induced toxicity was investigated. In general, this risk assessment does not indicate that children are likely to be at a elevated risk of AML or hematopoietic toxicity associated with environmental exposures to benzene.

Biomonitoring Equivalents for benzene.

Biomonitoring Equivalents (BEs) are defined as the concentration or range of concentrations of a chemical or its metabolite in a biological medium (blood, urine, or other medium) that is consistent with an existing health-based exposure guideline such as a reference dose (RfD) or tolerable daily intake (TDI). BE values can be used as a screening tool for the evaluation of population-based biomonitoring data in the context of existing risk assessments. This study reviews available health based risk assessments and exposure guidance values for benzene from the United States Environmental Protection Agency (US EPA), Texas Commission on Environmental Quality (TCEQ), California's Office of Environmental Health Hazard Assessment (OEHHA) and the Agency for Toxic Substances and Disease Registry (ATSDR) to derive BE values for benzene in blood and urine. No BE values were derived for any of the numerous benzene metabolites or hemoglobin and albumin adducts. Using existing physiologically based pharmacokinetic (PBPK) models, government risk assessment values were translated into corresponding benzene levels in blood assuming chronic steady-state exposures. BEs for benzene in urine were derived using measured correlations between benzene in urine with benzene in blood. The BE values for benzene in blood range from 0.04 to 1.29 µg/L, depending upon the underlying non-cancer risk assessment used in deriving the BE. Sources of uncertainty relating to both the basis for the BE values and their use in evaluation of biomonitoring data, including the transience of the biomarkers relative to exposure frequency, are discussed. The BE values derived here can be used as screening tools for evaluation of population biomonitoring data for benzene in the context of the existing risk assessment and can assist in prioritization of the potential need for additional risk assessment efforts for benzene relative to other chemicals.

Preservation of differentiation and clonogenic potential of human hematopoietic stem and progenitor cells during lyophilization and ambient storage.

Progenitor cell therapies show great promise, but their potential for clinical applications requires improved storage and transportation. Desiccated cells stored at ambient temperature would provide economic and practical advantages over approaches employing cell freezing and subzero temperature storage. The objectives of this study were to assess a method for loading the stabilizing sugar, trehalose, into hematopoietic stem and progenitor cells (HPC) and to evaluate the effects of subsequent freeze-drying and storage at ambient temperature on differentiation and clonogenic potential. HPC were isolated from human umbilical cord blood and loaded with trehalose using an endogenous cell surface receptor, termed P2Z. Solution containing trehalose-loaded HPC was placed into vials, which were transferred to a tray freeze-dryer and removed during each step of the freeze-drying process to assess differentiation and clonogenic potential. Control groups for these experiments were freshly isolated HPC. Control cells formed 1450+/-230 CFU-GM, 430+/-140 BFU-E, and 50+/-40 CFU-GEMM per 50 microL. Compared to the values for the control cells, there was no statistical difference observed for cells removed at the end of the freezing step or at the end of primary drying. There was a gradual decrease in the number of CFU-GM and BFU-E for cells removed at different temperatures during secondary drying; however, there were no significant differences in the number of CFU-GEMM. To determine storage stability of lyophilized HPC, cells were stored for 4 weeks at 25 degrees C in the dark. Cells reconstituted immediately after lyophilization produced 580+/-90 CFU-GM ( approximately 40%, relative to unprocessed controls p<0.0001), 170+/-70 BFU-E (approximately 40%, p<0.0001), and 41+/-22 CFU-GEMM (approximately 82%, p = 0.4171), and cells reconstituted after 28 days at room temperature produced 513+/-170 CFU-GM (approximately 35%, relative to unprocessed controls, p<0.0001), 112+/-68 BFU-E (approximately 26%, p<0.0001), and 36+/-17 CFU-GEMM ( approximately 82%, p = 0.2164) These studies are the first to document high level retention of CFU-GEMM following lyophilization and storage for 4 weeks at 25 degrees C. This type of flexible storage stability would potentially permit the ability to ship and store HPC without the need for refrigeration.

Temozolomide-induced myelodysplasia.

A patient who had received temozolomide (TMZ) as a single agent in treatment of malignant glioma developed therapy-induced myelodysplasia (T-MDS). TMZ is an orally active imidazotetrazine which methylates guanine residues in DNA, ultimately causing single and double-strand DNA breaks leading to apoptotic cell death. TMZ does not chemically cross-link DNA and is considered a nonclassical alkylating agent, similar in structure and activity to dacarbazine. Observations on this patient, and on similarly treated others, suggest that the cumulative dose threshold (CDT) for TMZ that predisposes to T-MDS and which may potentially lead to acute myeloid leukemia (T-AML) is around 18000 to 20000 mg/sq m. Although the incidence of T-MDS and the predisposing CDT of TMZ may differ from that of other potentially leukemogenic compounds currently and formerly used as chemotherapeutic agents, all alkylating agents, including TMZ, should be considered potentially leukemogenic when administered long term.

A review of the potential association between childhood leukemia and benzene.

Chronic exposure to high concentrations of benzene is an established cause of acute myeloid leukemia (AML) in occupationally exposed workers. Based on this association, it is not unreasonable to assume that children could also get AML if they were exposed to comparable levels of benzene. Fortunately, reports of such exposures and subsequent AML development in children are non-existent. However, the question of whether children can develop leukemia at far lower, environmental levels of benzene remains. The existing scientific evidence relevant to this question will be addressed in this review. While positive findings have been reported, the collective literature does not indicate that exposure to environmental levels of benzene is related to an increased risk of childhood leukemia. Our understanding of this important issue would be strengthened by additional studies that accurately characterize exposures as well as differentiate between the various forms of leukemias observed in children.

Is inhalation exposure to formaldehyde a biologically plausible cause of lymphohematopoietic malignancies?

The United States Environmental Protection Agency (EPA) recently proposed a hypothetical mode of action (MOA) to explain how inhaled formaldehyde (FA) might induce leukemia, lymphoma and a variety of other lymphohematopoietic (LHP) malignancies in occupationally exposed workers. The central hypothesis requires that B lymphocytes or hematopoietic progenitor cells (HPC) present at the "portal of entry (POE)" undergo sustained mutagenic change as a result of direct FA exposure. These modified cells would then migrate back to the bone marrow or primary lymphatic tissue and subsequently develop into specific LHP disease states. Chemical interaction at the POE is an absolute requirement for the hypothesized MOA as there is no convincing evidence that inhaled FA causes distant site (e.g., bone marrow) toxicity. The purpose of this review is to critically evaluate this proposed MOA within the context of the existing data concerning the toxicokinetic and biological properties of FA, the current understanding of the induction of chemically-induced leukemias and lymphomas, as well as within EPA's specific guidelines for evaluating the MOA of chemically-induced cancers. Specifically, we examine the scientific support for the hypothesis that FA exposure may induce carcinogenic transformation of localized lymphocytes or peripheral hematopoietic progenitor cells (HPC) in the absence of discernable systemic hematopoietic toxicity (i.e., peripheral transformation). While little or no empirical evidence exists upon which to fully evaluate the proposed hypothesis, available data does not support the proposed concept of "peripheral transformation" at the chemical entry site. Numerous animal bioassays evaluating chronic inhalation of FA clearly do not support this hypothesis since no properly conducted study as ever shown an increase in any LHP malignancy. Moreover, the notion that FA can cause any LHP malignancy is not supported with either epidemiologic data or current understanding of differing etiologies and risk factors for the various hematopoietic and lymphoproliferative malignancies. It is therefore concluded that existing science does not support the proposed MOA as a logical explanation for proposing that FA is a realistic etiological factor for any LHP malignancy.

Is age an independent risk factor for chemically induced acute myelogenous leukemia in children?

Secondary or therapy-related acute myelogenous leukemia (t-AML) is a rare but unfortunate consequence of treatment with certain classes of cytotoxic chemotherapeutic agents or chronic exposure to high concentrations of benzene. Drugs known to produce AML following chemotherapy of primary malignancy are usually alkylating agents or topoisomerase II inhibitors. Both children and adults develop AML following treatment with these classes of antineoplastic drugs. In this review, the effect of age at treatment on a child's susceptibility to developing therapy related AML was investigated. The clinical literature describing pediatric cancer patients treated with cytotoxic chemotherapeutic agents was used to characterize risk factors associated with chemical leukemogenesis in children. As demonstrated in the published literature, the risk of developing AML following chemotherapy is not reliably correlated with the age of the pediatric patient. There is no consistent evidence that indicates that younger children will be at increased risk; in fact, some studies suggest that younger children might actually display a decreased susceptibility. The age dependency of treatment-related malignancies (all types) in children appears to vary considerably with the type of secondary neoplasm in question. For example, secondary solid tumors such as breast, central nervous system (CNS), bone, and thyroid cancer are highly dependent on the age of the patient at time of diagnosis and treatment; in contrast, an age dependency for t-AML risk was not observed in these same patient populations. Predictably, the induction of t-AML in children follows a rational dose-response relationship, with increasing doses of chemotherapy resulting in greater risk. Recent U.S. Environmental Protection Agency (EPA) cancer risk assessment guidance recommends a default assumption that children are inherently up to 10-fold more sensitive than adults to carcinogen exposures. Available scientific and medical literature does not support the hypothesis that children necessarily possess an increased risk of developing AML following leukemogenic chemical exposure.

Formaldehyde as a potential human leukemogen: an assessment of biological plausibility.

The International Agency for Research on Cancer (IARC, 2004) recently reevaluated the epidemiological data on formaldehyde and concluded that there was "strong but not sufficient evidence for a causal association between leukaemia and occupational exposure to formaldehyde." This conclusion was tempered since a mechanism for leukemia induction could not be identified. Chemically induced leukemia is a well-studied phenomenon with benzene and a number of cancer chemotherapeutic drugs recognized as capable of causing this effect. Abundant in vitro and in vivo data in animals and humans demonstrate that exposure to sufficient doses of these recognized leukemogens can initiate a cascade of events leading to hematopoietic toxicity and the subsequent development of leukemia. This review addresses the biological plausibility that formaldehyde might be capable of causing any type of leukemia by providing a broad overview of the scientific data that must be considered in order to support or refute a conclusion that a particular substance might be leukemogenic. Data on benzene and selected chemotherapeutic cancer drugs are used as examples and are briefly summarized to demonstrate the similar biological events thought to result in leukemogenesis. These data are compared and contrasted with the available data on formaldehyde in order to judge whether they fulfill the criteria of biological plausibility that formaldehyde would be capable of inducing leukemia as suggested by the epidemiological data. Based on the epidemiological data, it is reasonable to expect that if formaldehyde was capable of inducing leukemia, in vivo and in vitro data would offer supporting evidence for biological plausibility. In particular, there is (1) no evidence to suggest that formaldehyde reaches any target organ beyond the site of administration including the bone marrow, (2) no indication that formaldehyde is toxic to the bone marrow/hematopoietic system in in vivo or in vitro studies, and (3) no credible evidence that formaldehyde induces leukemia in experimental animals. As discussed in this review, based on the key biological events that occur in the process of chemically induced leukemia, there is inadequate biological evidence currently available to corroborate existing weak epidemiological associations. This provides an insufficient database to conclude that there is a causal relationship for formaldehyde and leukemia risk.

Risk assessment for children exposed to decabromodiphenyl (oxide) ether (Deca) in the United States.

Decabromodiphenyl (oxide) ether (Deca) is a widely used brominated flame retardant in the United States predominantly in the hard-plastic housings of consumer electronics and in flame-retarded backing on textiles used in furniture. A child-specific exposure assessment of Deca was performed for the US Environmental Protection Agency's Voluntary Children's Chemical Evaluation Program (VCCEP). The VCCEP guidance for a tier 1 exposure assessment requires that a screening-level assessment be conducted using currently available data and conservative assumptions. For Deca, relevant exposure pathways considered were general environmental exposures (e.g., exposures to contaminated soil, dust, air, and food), breast milk exposures, inhalation of Deca-containing particulates in air, and mouthing Deca-containing consumer products. For each of these scenarios, a mid-range and upper estimate of age-appropriate intakes were calculated. The calculated intakes indicate that, despite the uncertainties, children appear to be exposed to Deca at levels at least 1 order of magnitude, with most being several orders of magnitude, below the National Academy of Sciences reference dose for Deca of 4 mg/kg/d. This analysis indicates that, using the available data, current levels of Deca in the United States are unlikely to represent an adverse health risk for children.

Do children have increased susceptibility for developing secondary acute myelogenous leukemia?

This study was undertaken to evaluate the effects of age on a child's susceptibility to developing leukemia following exposure to known leukemogenic agents. The clinical literature describing the risk of developing acute myelogenous leukemia (AML) following treatment with alkylating agents or topoisomerase reactive drugs (known leukemogens) was used as a basis for this investigation. Based on this preliminary assessment, the age of the child does not appear to be an independent variable for risk following treatment with either class of drug. Although the number of studies and cases was very small, the available scientific and medical literature does not support the hypothesis that children will necessarily have an altered susceptibility or increased risk of developing chemotherapy-induced AML.

Benzene and hematopoietic malignancies.

In certain countries outside of the United States, benzene remains a significant occupational hazard. This article provides a brief historical perspective of benzene use and general aspects of benzene toxicology, focusing primarily on benzene-induced hematotoxicity and leukemogenesis. Although the causal relationship between benzene and acute myelogenous leukemia is unequivocal, there has been considerable debate regarding the potential role of benzene exposure in the development of other hematopoietic malignancies, including chronic myelogenous leukemia, chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and multiple myeloma. The relationship between benzene and these other diseases also is discussed briefly.

Cryopreservation of stem cells using trehalose: evaluation of the method using a human hematopoietic cell line.

While stem cell cryopreservation methods have been optimized using dimethylsulfoxide (DMSO), the established techniques are not optimal when applied to unfertilized human embryonic cells. In addition, important questions remain regarding the toxicity and characteristics of DMSO for treatment of stem cells for clinical use. The objective of this study was to establish an optimal method for cryopreservation of stem cells using low concentrations (0.2 M) of trehalose, a nontoxic disaccharide of glucose, which possesses excellent protective characteristics, in place of current methods utilizing high concentrations (1-2 M) of DMSO. A human hematopoietic cell line was used in this investigation as a surrogate for human stem cells. Trehalose was loaded into cells using a genetically engineered mutant of the pore-forming protein alpha-hemolysin from Staphylococcus aureus. This method results in a nonselective pore equipped with a metal-actuated switch that is sensitive to extracellular zinc concentrations, thus permitting controlled loading of trehalose. Preliminary experiments characterized the effects of poration on TF-1 cells and established optimal conditions for trehalose loading and cell survival. TF-1 cells were frozen at 1 degrees C/min to -80 degrees C with and without intra- and extracellular trehalose. Following storage at -80 degrees C for 1 week, cells were thawed and evaluated for viability, differentiation capacity, and clonogenic activity in comparison to cells frozen with DMSO. Predictably, cells frozen without any protective agent did not survive freezing. Colony-forming units (CFU) generated from cells frozen with intra- and extracellular trehalose, however, were comparable in size, morphology, and number to those generated by cells frozen in DMSO. There was no observable alteration in phenotypic markers of differentiation in either trehalose- or DMSO-treated cells. These data demonstrate that low concentrations of trehalose can protect hematopoietic progenitors from freezing injury and support the concept that trehalose may be useful for freezing embryonic stem cells and other primitive stem cells for therapeutic and investigational use.

Inhibition of NF-kappaB by hydroquinone sensitizes human bone marrow progenitor cells to TNF-alpha-induced apoptosis.

Suppression of hematopoiesis is an important mechanism governing blood cell formation. Factors such as tumor necrosis factor alpha (TNF-alpha) inhibit proliferation and colony-forming activity of bone marrow cells and activate nuclear factor kappa B (NF-kappaB) in multiple cell types. Activated NF-kappaB is required for many cells to escape apoptosis, including hematopoietic progenitor cells (HPC). The benzene metabolite hydroquinone (HQ) alters cytokine response and induces cell death in HPC, and inhibits NF-kappaB activation in T and B cells. Therefore, we studied the potential role of HQ-induced NF-kappaB inhibition in a hematopoietic cell line (TF-1) and primary HPC in rendering these cells susceptible to TNF-alpha-induced apoptosis. We demonstrate in both cell types that TNF-alpha activates NF-kappaB, and HQ exposure inhibits activation of NF-kappaB by TNF-alpha in a dose dependent manner. We further investigated the ability of HQ to potentiate TNF-alpha-induced apoptosis in these cells, and found that HQ sensitized the cells to the pro-apoptotic effect of TNF-alpha. These results suggest that NF-kappaB plays a key role in HPC survival, and that HQ-induced inhibition of NF-kappaB leaves these cells susceptible to cytokine-induced apoptosis. These effects may play a role in the suppression of hematopoiesis seen in some benzene exposed individuals.