Bone marrow morphology in patients with neutropenia due to chronic exposure to organic solvents (benzene): early lesions

Nonlinear low dose hematotoxicity of benzene; a pooled analyses of two studies among Chinese exposed workers

BACKGROUND

Impairment of the hematopoietic system is one of the primary adverse health effects from exposure to benzene. We previously have shown that exposure to benzene at low levels (<1 ppm) affects the blood forming system and that these effects were proportionally stronger at lower versus higher levels of benzene exposure. This observation is potentially explained by saturation of enzymatic systems.

METHODS

Here we extend these analyses by detailed modeling of the exposure response association of benzene and its major metabolites (i.e. catechol, muconic acid, phenol, and hydroquinone) on peripheral white blood cell (WBC) counts and its major cell-subtypes (i.e. granulocytes, lymphocytes, and monocytes) using two previously published cross-sectional studies among occupationally exposed Chinese workers.

RESULTS

Supra-linear exposure response associations were observed between air benzene concentrations (range ∼ 0.1 - 100 ppm) and WBC counts and its cell-subtypes, with a larger than proportional decrease in cell counts at lower than at higher levels of benzene exposure. The hematotoxicity associations were largely similar in shape when the analyses were repeated with benzene urinary metabolites suggesting that enzymatic saturation is not a full explanation of the observed non-linearity with WBC endpoints.

DISCUSSION

We hypothesize that the flattening of the exposure response curve especially at higher benzene exposure levels may reflect a response by the bone marrow to maintain hematopoietic homeostasis. Toxicity to the bone marrow and an induced hyper-proliferative response could both contribute to risk of subsequently developing a hematopoietic malignancy. Additional work is needed to explore this hypothesis.

Shanghai Health Study (2001-2009): What was learned about benzene health effects?

The Shanghai Health Study (SHS) was a large epidemiology study conducted as a joint effort between the University of Colorado and Fudan University in Shanghai, China. The study was funded by members of the American Petroleum Institute between 2001 and 2009 and was designed to evaluate the human health effects associated with benzene exposure. Two arms of the SHS included: an occupational-based molecular epidemiology study and several hospital-based case control studies. Consistent with historical literature, following sufficient exposure to relatively high airborne concentrations and years of exposure, the SHS concluded that exposure to benzene resulted in an increased risk of various blood and bone marrow abnormalities such as benzene poisoning, aplastic anemia (AA), myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML). Non-Hodgkin lymphoma (NHL) was not significantly increased for the exposures examined in this study. Perhaps the most important contribution of the SHS was furthering our understanding of the mechanism of benzene-induced bone marrow toxicity and the importance of identifying the proper subset of MDS relevant to benzene. Investigators found that benzene-exposed workers exhibited bone marrow morphology consistent with an immune-mediated inflammatory response. Contrary to historic reports, no consistent pattern of cytogenetic abnormalities was identified in these workers. Taken together, findings from SHS provided evidence that the mechanism for benzene-induced bone marrow damage was not initiated by chromosome abnormalities. Instead, chronic inflammation, followed by an immune-mediated response, is likely to play a more significant role in benzene-induced disease initiation and progression than previously thought.

Metabolic Polymorphisms and Clinical Findings Related to Benzene Poisoning Detected in Exposed Brazilian Gas-Station Workers

Benzene is a ubiquitous environmental pollutant and an important industrial chemical present in both gasoline and motor vehicle emissions. Occupational human exposure to benzene occurs in the petrochemical and petroleum refining industries as well as in gas-station workers, where it can lead to benzene poisoning (BP), but the mechanisms of BP are not completely understood. In Brazil, a significant number of gas-station service workers are employed. The aim of the present study was to evaluate alterations related to BP and metabolic polymorphisms in gas-station service workers exposed to benzene in the city of Rio de Janeiro, Brazil. Occupational exposure was based on clinical findings related to BP, and metabolic polymorphisms in 114 Brazilian gas-station attendants. These workers were divided into No Clinical Findings (NCF) and Clinical Findings (CF) groups. Neutrophil and Mean Corpuscular Volume (MCV) showed a significant difference between the two study groups, and neutrophil has the greatest impact on the alterations suggestive of BP. The clinical findings revealed higher frequencies of symptoms in the CF group, although not all members presented statistical significance. The frequencies of alleles related to risk were higher in the CF group for GSTM1, GSTT1, CYP2E1 7632T > A, but lower for NQO1 and CYP2E1 1053C > T genotypes. Moreover, an association was found between GSTM1 null and alterations related to BP, but we did not observe any effects of other polymorphisms. Variations in benzene metabolizing genes may modify benzene toxicity and should be taken into consideration during risk assessment evaluations.

Bone marrow necrosis: ten-year retrospective review of bone marrow biopsy specimens

OBJECTIVES

Bone marrow can undergo necrosis for many different causes; malignant causes are reported to be more frequent.

METHODS

We undertook a 10-year retrospective review of all bone marrow biopsy specimens with bone marrow necrosis at our institution.

RESULTS

Identified cases represented approximately 0.3% of our bone marrow cases. Most identified bone marrow cases with necrosis were involved by metastatic tumor or hematolymphoid malignancy (90% of total) in relatively equal proportions. In those cases of bone marrow necrosis with hematolymphoid malignancy, lymphoid disease predominated and the necrosis was often seen in the setting of chemotherapy. In metastatic tumor cases, necrosis seemed to enrich in prostate adenocarcinoma and Ewing sarcoma/primitive neuroectodermal tumor; neuroblastoma showed much less necrosis. Ten percent of patients with bone marrow necrosis had no underlying malignancy, and the associated causes varied.

CONCLUSIONS

The causes of bone marrow necrosis are diverse but should always prompt careful assessment for malignancy and infectious etiology.

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.

Glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) genetic polymorphisms and atopic asthma in children from Southeastern Brazil

Xenobiotics can trigger degranulation of eosinophils and mast cells. In this process, the cells release several substances leading to bronchial hyperactivity, the main feature of atopic asthma (AA). GSTM1 and GSTT1 genes encode enzymes involved in the inactivation of these compounds. Both genes are polymorphic in humans and have a null variant genotype in which both the gene and corresponding enzyme are absent. An increased risk for disease in individuals with the null GST genotypes is therefore, but this issue is controversial. The aim of this study was to investigate the influence of the GSTM1 and GSTT1 genotypes on the occurrence of AA, as well as on its clinical manifestations. Genomic DNA from 86 patients and 258 controls was analyzed by polymerase chain reaction. The frequency of the GSTM1 null genotype in patients was higher than that found in controls (60.5% versus 40.3%, p = 0.002). In individuals with the GSTM1 null genotype the risk of manifested AA was 2.3-fold higher (95%CI: 1.4-3.7) than for others. In contrast, similar frequencies of GSTT1 null and combined GSTM1 plus GSTT1 null genotypes were seen in both groups. No differences in genotype frequencies were perceived in patients stratified by age, gender, ethnic origin, and severity of the disease. These results suggest that the inherited absence of the GSTM1 metabolic pathway may alter the risk of AA in southeastern Brazilian children, although this must be confirmed by further studies with a larger cohort of patients and age-matched controls from the distinct regions of the country.

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.

Integrating WHO 2001-2008 criteria for the diagnosis of Myelodysplastic Syndrome (MDS): a case-case analysis of benzene exposure

We characterized the prevalence of hematopoietic and lymphoid disease for 2923 consecutive patients presenting at 29 hospitals from August 2003 to June 2007. Diagnoses were made in our laboratory using WHO criteria based on morphologic, immunophenotypic, cytogenetic, FISH and molecular data. A total of 611 subjects (322 males/289 females) were prospectively diagnosed with MDS using WHO (2001) criteria. Update and re-evaluation of cases using MDS (2008) criteria resulted in 649 MDS cases. Using WHO (2008) criteria, refractory cytopenia with multilineage dysplasia (RCMD) accounted for 68% of total cases, refractory anemia with excess blasts (RAEB), 16.3%; refractory anemia (RA), 6.5%; refractory cytopenia with unilineage dysplasia (RCUD), 4%; and MDS-unclassifiable (MDS-U), 4.5%. Subjects were administered questionnaires and information on previous disease, work histories and exposures to potential etiologic agents such as benzene (BZ) was obtained. A total of 80/649 (13.2%) were determined to have some BZ exposure. The frequency of clonal cytogenetic abnormalities in all MDS was 30%, the most common being +8>del(20)q>del(7q)>del(5q), while the analogous frequency in BZ-exposed cases was only 24%. To further investigate the characteristics of MDS associated with BZ, we identified a subset of cases with high BZ exposure. These BZ signal cases were each matched by age and gender to two cases with no known BZ exposure. When contrasting BZ signal cases vs matched cases with no BZ exposure, we found a high odds ratio (OR) for the WHO subtype MDS-U (OR=11.1), followed by RAEB and RCUD (OR=1), RA (OR=0.7) and RCMD (OR=0.6). Multilineage dysplasia with abnormal eosinophils (MDS-Eo) was strongly associated with BZ exposure, whereas the relative risk of clonal cytogenetic abnormalities was reduced for high BZ-exposed cases (OR=0.5). These findings are strongly indicative that MDS subtypes are influenced by BZ exposure, and taken together with previous studies, the features of MDS-Eo suggest that altered immune regulation plays a major role in the pathogenesis of MDS following chronic exposure to BZ.

No contribution of GSTM1 and GSTT1 null genotypes to the risk of neutropenia due to benzene exposure in Southeastern Brazil

Exposure to benzene has been associated with haematological diseases such as neutropenia (NEB) and acute myeloid leukaemia (AML). We tested whether the null genotypes of the GSTM1 and GSTT1 genes, involved in benzene inactivation, altered the risk for NEB in southeastern Brazil. Genomic DNA from 55 NEB patients and 330 controls was analysed by multiplex-polymerase chain reaction. The frequency of the GSTM1, GSTT1 and combined null genotypes was similar in patients and controls (GSTM1, 27.3% vs. 38.8%, p = 0.16; GSTT1, 25.5% vs. 19.7%, p = 0.24; GSTM1/GSTT1, 12.7% vs. 6.7%, p = 0.26; respectively). The distribution of genotype classes in NEB patients was similar to normal controls, suggesting that GSTM1 and GSTT1 null genotypes make no specific contribution to the risk of NEB. As the GSTM1 and GSTT1 null genotypes were previously associated with increased risk for AML in Brazil and elsewhere, we hypothesise that different thresholds of chemical exposure relative to distinct GSTM1 and GSTT1 genotypes may determine whether AML or NEB manifests in benzene exposed individuals from southeastern Brazil. Although indicative, our results still require support by prospective and large scale epidemiological studies, with rigorous assessment of daily chemical exposures and control of the possible contribution of other polymorphic genes involved in benzene metabolism.

Polymorphisms of glutathione S-transferase Mu 1, glutathione S-transferase theta 1 and glutathione S-transferase Pi 1 genes in Hodgkin's lymphoma susceptibility and progression

We tested in this study whether the polymorphisms of the glutathione S-transferase Mu1 (GSTM1), glutathione S-transferase Theta 1 (GSTT1) and glutathione S-transferase Pi 1 (GSTP1), involved in metabolism of chemical agents, cell proliferation and cell survival, alter the risk for Hodgkin lymphoma (HL). Genomic DNA from 110 consecutive patients with HL and 226 controls was analysed by polymerase chain reaction and restriction digestion for the polymorphism analyses. Similar frequencies of the GSTM1 and GSTT1 genotypes were seen in patients and controls. In contrast, the frequency of the GSTP1 wild genotype (59.1%versus 36.3%, P = 0.004) was higher in patients than in controls. Individuals with the wild genotype had a 2.68 (95%CI: 1.38-5.21)-fold increased risk for the disease than others. An excess of the GSTP1 wild genotype was also observed in patients with tumors of stages III + IV when compared with those with tumors of stages I + II (39.1%versus 20.0%, P = 0.03). These results suggest that the wild allele of the GSTP1 gene is linked to an increased risk and high aggressiveness of the HL in our cases but they should be confirmed by further studies with larger cohorts of patients and controls.

ATSDR evaluation of health effects of benzene and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Benzene. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of benzene. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.

Benzene exposure and refractory sideroblastic erythropoiesis: is there an association?

The myelodysplastic syndromes (MDS) consist of a group of diverse hematological disorders that carry an increased risk of transforming into acute myeloid leukemia. They may appear de novo and without obvious cause (primary or de novo MDS) or be induced by certain mutagenic environmental or therapeutic toxins (secondary MDS). Excessive exposures to benzene are generally considered to be a potential environmental risk factor for both MDS and acute myeloid leukemia. However, such risk is unproven for each disease component within the MDS classification. A critical review of the refractory sideroblastic disorders strongly suggests that benzene exposure is not a potential cause of this distinct and still-evolving subset of MDS. The widely disparate nature of MDS suggests that epidemiologic studies can only provide meaningful data on associations and potential causation of its component syndromes by a disease-specific analysis, as is currently advocated for other hematological malignancies.

Benzene-induced acute myeloid leukemia: a clinician's perspective

Benzene-induced acute myeloid leukemia (AML) is considered a secondary form of AML, based both in theory and on limited cohort observations. Its latency, cytogenetic aberrations, and clinical features are thought similar to, or identical with, AML resulting from the use of modern day cytotoxic agents for chemotherapy and immunotherapy. Although distinction between secondary AML and the far more common de novo AML is difficult to establish with certainty in any given case, latency from toxic therapeutic and environmental exposure and certain clinical and pathological features generally separate these two entities. AML is the only human neoplasm proven to be potentially caused by benzene, which actually is an obsolete form of chemotherapy. Despite many years of environmental regulation, alleged toxic exposure to this ubiquitous chemical has become an expanding area of litigation. A review of benzene-induced AML suggests that, in developed countries, this entity should no longer merit serious consideration among workers in the modern petrochemical industry and related fields.

GSTM1 and codon 72 P53 polymorphism in multiple myeloma

The GSTM1 and GSTT1 genes reduce the effects of exposure to cytotoxic agents. Both genes have a null variant allele in which the entire gene is absent. On the other hand, a common polymorphism of the tumour suppressor P53 gene results in either arginine (A) or proline (P) at amino-acid position 72. The A and P alleles code proteins with distinct functions in apoptosis and DNA repair and have been associated with variable risks for several cancers. However, their roles in multiple myeloma (MM) are still unknown. We tested in study whether the GSTM1, GSTT1 and P53 genotypes altered the risk for MM in Brazilian patients. Genomic DNA from 106 patients and 230 controls were analysed by polymerase chain reaction-based methods for identification of the genotypes. Similar frequencies of the GSTM1, GSTT1 and P53 genotypes were seen in patients and controls. Individuals with the distinct genotypes had similar risks for disease. In contrast, an excess of the GSTM1 null (45.1 vs 17.2%, P = 0.009), the P53 PP+AP (70.4 vs 44.8%, P = 0.041) and the GSTM1 null plus P53 PP+AP (29.6 vs 10.3%, P = 0.004) genotypes were seen in MM patients at stage III compared with those at stages I + II. Our data suggest that the GSTM1, GSTT1 and P53 genotypes do not influence the risk for MM. However, the inherited presence of the variant codon 72 P53 allele, described here for the first time, and the absence of the GSTM1 detoxification pathway, seem to act in disease progression in our country.

Immunotoxic effects of chemicals: A matrix for occupational and environmental epidemiological studies

BACKGROUND

Many biological and chemical agents have the capacity to alter the way the immune system functions in human and animals. This study evaluates the immunotoxicity of 20 substances used widely in work environments.

METHODS

A systematic literature search on the immunotoxicity of 20 chemicals was performed. The first step was to review literature on immunotoxicity testing and testing schemes adopted for establishing immunotoxicity in humans. The second step consisted of providing a documentation on immunotoxicity of substances that are widely used in work environment, by building tables for each chemical of interest (benzene, trichloroethylene, PAHs, crystalline silica, diesel exhausts, welding fumes, asbestos, styrene, formaldehyde, toluene, vinyl chloride monomer, tetrachloroethylene, chlorophenols, 1,3-butadiene, mineral oils, P-dichlorobenzene, dichloromethane, xylene, 1,1,1-trichloroethane, ethylene oxide). The third step was the classification of substances; an index (strong, intermediate, weak, nil) was assigned on the basis of the evidence of toxicity and type of immunotoxic effects (immunosuppression, autoimmunity, hypersensitivity) on the basis of the immune responses. Finally substances were assigned a score of immunotoxic power.

RESULTS

Tables have been produced that include information for the 20 substances of interest, based on 227 animal studies and 94 human studies. Each substance was assigned an index of immunotoxic evidence, a score of immunotoxic power and type of immunotoxic effect.

CONCLUSIONS

This matrix can represent a tool to identify chemicals with similar properties concerning the toxicity for the immune system, and to interpret epidemiological studies on immune-related diseases.

Causes of incidental neutropenia in adulthood

The incidental discovery of neutropenia during routine blood counting represents a common problem for clinicians. However, there are no reported data of systematic evaluations of adults with incidental neutropenia. As such, this was the aim of the present study. Ninety-seven adults with incidental neutropenia were submitted to a clinical and laboratory approach including medical evaluation, complete blood count (CBC), serial CBC, direct and indirect antiglobulin test, bone marrow smear and biopsy, assessment of folate, vitamin B12 and iron status, serum liver enzymes, serum proteins, serological exams for hepatitis B and C virus, cytomegalovirus, mononucleosis, human immunodeficiency virus and toxoplasmosis, detection of lupus erythematosus cells, antinuclear and anti-DNA antibodies and rheumatoid factor, dosage of free thyroxin and thyrotropin, chest roentgenogram and abdominal echography. Chronic idiopathic neutropenia of adults was identified in 34.0% of the individuals, neutropenia due to exposure to chemical agents was seen in 16.5%, infectious diseases in 9.3%, autoimmune diseases in 9.3%, haematological diseases in 9.3%, thyroid disorders in 8.2%, ethnic neutropenia in 7.2%, drug-related neutropenia in 2.1%, cyclic neutropenia in 2.1% and iron deficiency in 2.1%. Recovery or improvement of the neutrophil count was seen upon treatment or recuperation from infectious, autoimmune, haematological and thyroid diseases and iron supplementation. We conclude that the evaluation of individuals with incidental neutropenia using a structured approach may make the identification of clinically silent diseases possible, and provide an opportunity for early treatment, avoiding complications of the diseases and consequences of neutropenia.

Validation and Development of a Predictive Paradigm for Hemotoxicology Using a Multifunctional Bioluminescence Colony-Forming Proliferation Assay

The lympho-hematopoietic colony-forming assay has been redesigned into a rapid, nonsubjective and standardized proliferation assay that can measure the effects of compounds on multiple stem and progenitor cell populations from different species simultaneously using a sensitive, high-throughput bioluminescence readout. Eleven reference compounds from the Registry of Cytotoxicity (RC) and eight other compounds, including anticancer drugs, were studied over an 8- to 9-log dose range for their effects on seven cell populations from both human and mouse bone marrow simultaneously. The cell populations studied included a primitive (HPP-SP) and mature (CFC-GEMM) stem cell, three hematopoietic (BFU-E, GM-CFC, Mk-CFC) and two lymphopoietic (T-CFC, B-CFC) populations. The results reveal a five-point prediction paradigm for lympho-hematotoxicity. Depending on how and which populations are affected, the resulting effects in the periphery can be predicted. Validation against the RC Prediction Model produces a high degree of correlation between the in vitro IC(50) values and known in vivo LD(50) values, thereby allowing preclinical dosing to be predicted. If primary human hematopoietic target tissue is used, inhibitory concentration (IC(50)/IC(75)/IC(90)) values of anticancer and other drugs can be converted into predicted clinical doses which, when compared to published chemotherapeutic dosing regimen, are very similar. When performed during early drug screening, the prediction value of the assay should help reduce time and cost, but above all, provide increase efficacy and safety for the patient.

The use of non-tumor data in cancer risk assessment: reflections on butadiene, vinyl chloride, and benzene

The estimation and characterization of a cancer risk is grounded in the observation of tumors in humans and/or experimental animals. Increasingly, however, other kinds of data (non-tumor data) are finding application in cancer risk assessment. Metabolism and kinetics, adduct formation, genetic damage, mode of action, and biomarkers of exposure, susceptibility, and effects are examples. While these and other parameters have been studied for many important chemicals over the past 30-40 years, their use in risk assessments is more recent, and new insights and opportunities are continuing to unfold. To provide some perspective on this field, the ILSI Risk Science Institute asked a select working group to characterize the pertinent non-tumor data available for 1,3-butadiene, benzene, and vinyl chloride and to comment on the utility of these data in characterizing cancer risks. This paper presents the findings of that working group and concludes with 15 simple principles for the use of non-tumor data in cancer risk assessment.

The Brazilian Pediatric Myelodysplastic Cooperative Group strategies: are they relevant to improve educational approach and correct diagnosis?

Brazil is a wide country with huge contrasts. Its peculiarities can highlight environmental factors that could influence the frequencies of different cancers. The standard treatment and results achieved from several different areas of the country may not be found in others. The establishment of a national cooperative group has the potential to improve outcomes. The The Brazilian Cooperative Group on Pediatric Patients with Myelodysplastic Syndrome (BCG-MDS-PED) was first organized in January 1997 as a working group of hematologists, pediatric oncologists, pediatric-hematologists, molecular biologists and other professionals in order to study pediatric (age <18 years) MDS. Six distinct subcommittees constituted with members from several universities: cytology, histopathology, clinical, cytogenetics, molecular biology and epidemiology. The goals of the BCG-MDS-PED were: (i) to offer support for diagnosis and orientation for treatment; (ii) educational support for the colleagues all over the country and (iii) research on pathogenesis and new approaches for pediatric MDS patients. There are socio-economical differences among the five regions of the country. The BCG-MDS-PED believes that it is absolutely necessary to study the clinical, cellular, molecular and epidemiological aspects of MDS, taking in account these peculiar differences among populations and regions. Since 1997, 114 pediatric cases were referred to the BCG-MDS-PED from 21 centres. Seven Brazilian states have sent cases to the group, 31 patients were referred from universities, 73 patients from pediatric oncology units (foundations ) and 10 patients came from private clinics. Some of these patients have been followed up and/or treated by the physician who referred them to the BCG-MDS-PED for confirmation of the initial diagnosis. The majority of these physicians have required orientation on diagnostic and treatment issues, as well as to complete cytogenetic and molecular studies. From these 114 patients, 64 patients were confirmed as MDS. We believe that, the more numerous the MDS-studied cases, the more experienced will be the referee group on clinical and laboratory features on childhood MDS in Brazil.

Increased risk for acute myeloid leukaemia in individuals with glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) gene defects

OBJECTIVES

Glutathione S-transferases (GST) modulate the effects of exposure to various cytotoxic and genotoxic agents, including those associated with increased risks of the myelodysplastic syndrome (MDS), acute myeloid leukaemia (AML) and aplastic anemia (AA). Both the GST mu 1 (GSTM1) and GST theta 1 (GSTT1) genes have a null variant allele in which the entire gene is absent. In this study, we tested whether null genotypes for the GSTM1 and GSTT1 genes altered the risks for MDS, AML and AA.

METHODS

Genomic DNA from 49 MDS, 38 AML and 37 AA patients and 276 controls was analysed using the polymerase chain reaction (PCR).

RESULTS

The frequencies of GSTM1 (73.6%) and GSTT1 (34.2%) null genotypes were significantly higher in AML patients than in the controls (36.9 and 18.1%, respectively). A higher frequency of the combined null genotype for both genes was also observed in patients with AML (26.3% compared with 5.0% in the controls). In contrast, no differences in the frequencies of the null genotypes were found among MDS patients, AA patients and the controls.

CONCLUSION

Our observation of a 4.7-fold (95% CI: 2.1-11.0) and 2.3-fold (95% CI: 1.0-5.2) increased risk associated with the GSTM1 and GSTT1 null genotypes, respectively, and a 6.6-fold (95% CI: 2.4-7.9) increased risk associated with the combined null genotype presents preliminary evidence that the inherited absence of this carcinogen detoxification pathway may be an important determinant of AML.

Prevalence of homozygosity for the deleted alleles of glutathione S-transferase mu (GSTM1) and theta (GSTT1) among distinct ethnic groups from Brazil: relevance to environmental carcinogenesis?

Environmental related diseases due to occupational carcinogens and toxic substances are a serious problem particularly in developing countries. The glutathione S-transferase system is fundamental for the detoxification of numerous carcinogens and mutagens. The individual inherited susceptibility to chemical carcinogenesis due to glutathione S-transferase mu (GSTM1) and theta (GSTT1) varies significantly among distinct ethnic groups. In this study we determined the prevalence of the null genotype of the GSTM1 and GSTT1 genes among individuals from three distinct Brazilian racial groups using a multiplex-PCR methodology. The results showed that the highest prevalence of the null genotype for the GSTM1 occurred among Caucasians (55%, allele frequency = 0.74), followed by 33% among Brazilian Black subjects (allele frequency = 0.57), and 20% among Amazonian Indians (allele frequency = 0.45). For GSTT1 a homogenous distribution of the null genotype was found among Caucasian and African descendants (18.5 and 19% homozygotes, respectively, allele frequency = 0.43), with a lower prevalence among Amazonian Indians (11% of homozygotes, allele frequency = 0.34). Whether the deficiency of the GST system contributes to a predisposition to environmental related carcinogenesis in specific populations in Brazil remains to be determined.