Experimental study on malignant transformation of human bronchial epithelial cells induced by glycidyl methacrylate and analysis on its methylation.

OBJECTIVE: To establish the model of human bronchial epithelial cells (16HBE) malignant transformation induced by glycidyl methacrylate (GMA) and define the different methylation genes at different stages. METHODS: DNA was extracted at different 16HBE malignant phases and changes of genes DNA methylation at different stages were detected using Methylation chip of 'NimbleGen HG18 CpG Promoter Microarray Methylation'. Methylation-specific PCR (MSP) was used to observe the methylation status of some genes, and then compared with the control groups. RESULTS: The result showed that GMA induced 16HBE morphorlogical transformation at the dose of 8 µg/mL, and cell exposed to GMA had 1374 genes in protophase, 825 genes in metaphase, 1149 genes in anaphase, respectively; 30 genes are all methylation in the 3 stages; 318 genes in protophase but not in metaphase and anaphase; 272 genes in metaphase but not in protophase and anaphase; 683 genes in anaphase but not in metaphase and protophase; 73 genes in protophase and metaphase but not in anaphase; 67 genes in protophase and anaphase but not in metaphase; 59 genes in metaphase and anaphase but not in protophase. CONCLUSION: The pattern of DNA methylation could change in the process of 16HBE induced by GMA.

Elevated levels of mitochonrial respiratory complexes activities and ATP production in 17-ß-estradiol-induced prolactin-secretory tumor cells in male rats are inhibited by melatonin in vivo and in vitro.

BACKGROUND: Our earlier studies indicate that melatonin inhibits the proliferation of prolactinoma and induces apoptosis of pituitary prolactin-secreting tumor in rats. Melatonin has also been shown to induce apoptosis and to reduce the production of ATP in breast tumor cells. This study analyzed the levels of the four mitochondrial respiratory complexes and the production of ATP and also the effects of melatonin treatment of prolactinoma. METHODS: In the in vivo study, mitochondria were harvested from control pituitaries or prolactinoma collected from the pituitaries of melatonin- and 17-ß-estradiol (E2)-treated male rats. In the in vitro study, prolactinoma cells mitochondria were harvested. Activities of the four mitochondrial respiratory complexes were assayed using fluorometer. ATP production of prolactinoma cells was estimated using bioluminescent methods. RESULTS: Elevated levels of four mitochondrial respiratory complexes activities and ATP production were recorded in prolactinoma cells. Moreover, in both in vivo and in vitro studies, melatonin inhibited the activities of mitochondrial respiratory complexes and the production of ATP in prolactinoma cells. CONCLUSIONS: There is a link between mitochondrial function increase and tumorigenesis. Melatonin induces apoptosis of pituitary prolactin-secreting tumor of rats via the induction of mitochondrial dysfunction and inhibition of energy metabolism.

[Method for determining brodifacoum in workplace air by high-performance liquid chromatography].

OBJECTIVE: To establish a method for determining brodifacoum in workplace air by high-performance liquid chromatography (HPLC). METHODS: Brodifacoum in workplace air was collected with a polytetrafluoroethylene filter and desorbed by mixed solution of methanol and dichloromethane (20:80, V:V), and was then separated using an ODS column and determined by an ultraviolet detector; retention time was used for identification, and peak area was used for quantification. RESULTS: The concentration of brodifacoum showed a linear relationship with peak area within 0.2∼10.0 µg/ml; the elution efficiency was 91.6%∼95.1%; the detection limit was 0.08 µg/ml (injection volume: 20 µl eluate); the minimum detectable concentration was 0.000 67 mg/m(3) (calculated by 240 L air sample). CONCLUSION: This HPLC method is convenient and simple for air collection and sample preparation and meets the methodological requirements. Therefore, this method can be used for the determination of brodifacoum in workplace air.

Establishment of occupational exposure limit for warfarin in China.

This study aims to establish the occupational exposure limit (OEL) in the air for workplace of warfarin based on the available toxicological studies and field investigations by using questionnaire and air monitoring. The clinical therapeutic dose was used as lowest observed effect level (LOEL), and no observed effect level (NOEL) was achieved by using a safety factor. The highest concentration of warfarin monitored in the worksite of centrifuge washing, drying and packing were 0.029 mg/m3, 0.051 mg/m3 respectively, which did not exceed the OEL 0.1 mg/m3 recommended by NIOSH and ACGIH. Considering its feasibility for enforcement and protection for workers, we recommend OEL 0.1 mg/m3 of warfarin in China.

[Methylation status of P16 gene during malignant transformation of human bronchial epithelial cells induced by glycidyl methacrylate].

OBJECTIVE: To analyze the methylation status of P16 gene at the different stages of malignant transformation of human bronchial epithelial cells (16HBE) induced by glycidyl methacrylate (GMA) and to explore the DNA methylation mechanisms. METHODS: The cells exposed to GMA were harvested at the end of exposure (early stage), the 10th generation (protophase) and the 30th generation (anaphase), respectively. The methylation status of P16 promotor was detected by Methylation-specific PCR (MSP). The transformed 16HBE cells were compared with the normal 16HBE cells and the cells exposed to DMSO for methylation status. RESULTS: At the early stage and protophase stage, the non-methylation status in P16 gene promotor of the normal 16HBE cells and the cells exposed to DMSO appeared, the methylation status in P16 gene promotor of the 16HBE cells exposed to GMA was detected to some extension. At the anaphase stage, the methylation status in P16 gene promotor of the 16HBE cells exposed to GMA or DMSO was detected to some extension. CONCLUSION: Methylation status of P16 gene promoter was specific at the early stage and protophase stage of malignant transforming in 16HBE cells induced by GMA, which can serve as an early sensitive biological indicator for malignant transforming in 16HBE cells induced by GMA.

[Determination of brodifacoum in rat plasma by HPLC].

OBJECTIVE: A determination method of brodifacoum in rat plasma with bromadiolone as an internal standard was developed. METHODS: A volume of 10 microl internal standard (bromadiolone) was added into rat plasma, and then extracted by 0.5 ml of acetonitrile by shaking for 2 min. The residue was dissolved with 200 microl of mobile phase after centrifugation for 10 min, and evaporation to dryness by Nitrogen blowing. A C18 column and PDA detector were used for separating and detecting. The wavelength was 254 nm, the flow rate was 1.0 ml/min, and the injection volume was 20 microl. RESULTS: The liner range was 1.0-20 microg/ml, and the correlation coefficient was 0.9992. The detection limit was 0.3 microg/ml in plasma (S/N=3). The intra-assay and inter-assay coefficients of variation were 1.89%-2.45% and 2.51%-3.61% respectively. The recoveries in plasma at levels of low, middle and high concentrations were (80.8 +/- 3.1)%, (81.8 +/- 2.7)% and (87.9 +/- 3.6)% (n=6), respectively. The accuracies were 84.1%-91.5% and 86.7%-93.2%, respectively. CONCLUSION: This method is simple, fast and accurate for the determination of brodifacoum in rat plasma.

[Study on malignant transformation of human bronchial epithelial cells induced by glycidyl methacrylate].

OBJECTIVE: To study the malignant transformation of human bronchial epithelial cells induced by glycidyl methacrylate (GMA). METHODS: 16HBE cells were treated multiple times with GMA at concentrations of 1, 2, 4 and 8 microg/ml. Cellular biological characteristics of malignant transformation were identified by the tests of conA, colony forming frequency on soft agar, scanning electron microscope and tumorigenesis in nude mice. Test of immunocytochemical detection was also applied to confirm the derivation of cell and tumor. Groups of solvent control (DMSO) and positive control (MCA) were also performed at the same time. RESULTS: Transformed foci could be observed after the cells were treated by GMA at concentrations from 1 to 8 microg/ml. The number of transformation foci increased with the concentration of GMA. Transforming rate in 8 microg/ml group (8.48 x 10(-6)) was significantly higher (P < 0.01) than that of solvent control group (4.5 x 10(-7)). The transformed cells lost contact inhibition and exhibited a crossover growth in culture dish. They also could grow in semi-solid agar and showed dose-reaction relations with the concentration of GMA. The colony forming frequency in 2, 4 and 8 microg/ml group was 1.20 per thousand, 2.35 per thousand and 5.70 per thousand respectively, which were higher than that of solvent control group (P < 0.01). The transformed cells could be agglutinated by low concentration of conA. Microvilli on the surface of transformed cells increased and became strong and long under scanning electron microscope. The transformed cells could form subcutaneous tumor in nude mice which was diagnosed as squamous cell carcinoma in morphology. Expression of cytokeratin (CK) was detected in both 16HBE cells and tumor formed in nude mice. CONCLUSION: GMA could induce the malignant transformation of 16HBE cells. This research system might provide a potential tool and lay a foundation for the study of the molecular mechanism of carcinogenesis induced by GMA.

[Analysis for the association between genetic polymorphisms of XRCC1, XPD, XRCC3, CCND1 and the latency of the occupational chronic benzene poisoning].

OBJECTIVE: To explore the association between genetic polymorphisms of XRCC1, XPD, XRCC3 and CCND1 and latency of occupational chronic benzene poisoning. METHODS: 80 patients diagnosed with occupational chronic benzene poisoning were investigated. PCR-RFLP was applied to detect the single nucleotide polymorphisms of C26304T, G27466A, G28152A, G36189A of XRCC1, C22541A, C23591T, A35931C of XPD, C18067T of XRCC3 and G870A of CCND1. Their relationship with the latency of chronic benzene poisoning was analyzed by Kaplan-Meier method. RESULTS: The association of XRCC1 G27466A subgroup with the latency of chronic benzene poisoning was observed, as well as that of CCDN1G870A subgroup. The benzene-exposed workers with XRCC1 27466G/G homozygous wild genotype developed chronic benzene poisoning 6.9 years later than those had homozygous (27466A/A) or heterozygous (27466G/A) mutant alleles. On the other hand, the latency developing chronic benzene poisoning was longer in workers with homozygous (CCND1 870A/A) or heterozygous (CCND1 870G/A) mutant alleles than in those carrying 870G/G homozygous wild genotype (14.9 vs. 8.7 years). CONCLUSION: The polymorphisms of XRCC1 and CCND1 potentially modify the latency of the chronic benzene poisoning among workers exposed to benzene.

[Association between genetic polymorphisms of DNA repair genes XRCC1, XRCC3 and susceptibility to chronic benzene poisoning].

OBJECTIVE: To explore the association between genetic polymorphisms of DNA repair genes XRCC1, XRCC3 and susceptibility to chronic benzene poisoning. METHODS: A case-control study was conducted. Eighty patients with chronic benzene poisoning and 62 workers occupationally exposed to benzene who were engaged in the same working time and job title as patients were investigated. Polymerase chain reaction-restriction fragments length polymorphism (PCR-RFLP) was used to detect the single nucleotide polymorphisms on C26304T, G27466A, G28152A, G36189A of XRCC1 and C18067T of XRCC3. The relationship between them and latency of chronic benzene poisoning was analyzed by Kaplan-Meier method. RESULTS: A correlation for XRCC3 18067C/T compared with C/C genotype was found (OR=0.233, 95% CI 0.085 approximately 0.639, P=0.0046). Patients who were XRCC1 27466G/G homozygous wild genotype developed chronic benzene poisoning average 6 years later than those had homozygous (27466A/A) or heterozygous (27466G/A) mutant alleles. CONCLUSION: Subjects with XRCC3 18067T variant allele are tolerance sub-group to benzene poisoning. Patients carrying XRCC1 27466 G/G genotype develop chronic benzene poisoning later.

Antiproliferative effects of melatonin on the growth of rat pituitary prolactin-secreting tumor cells in vitro.

Earlier studies showed that melatonin reduced the growth of 17-beta-estradiol (E(2))-induced rat pituitary prolactin-secreting tumor (prolactinoma) in vivo. The mechanisms of melatonin's inhibitory action on the prolactin-secreting tumor were further explored by investigating the in vitro effects of melatonin on the growth of pituitary prolactin-secreting tumor cells. Primary cultured prolactinoma cells from E(2)-induced rat pituitary prolactin-secreting tumor were treated with 10(-5), 10(-4) or 10(-3) m melatonin for 5 days. Apoptosis was evaluated using flow cytometry and the TdT-mediated dUTP nick-end labeling (TUNEL) method. In addition, cell viability was analyzed by (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It was found that incubation of prolactinoma cells with 10(-5), 10(-4) or 10(-3) m melatonin for 5 days inhibited cell growth and increased cell apoptosis. Furthermore, melatonin increased caspase-3 activity, Bax mRNA expression, and cytochrome c protein expression. Conversely, Bcl-2 mRNA expression and mitochondrial membrane potential were inhibited by melatonin treatment. Our results further suggest that melatonin inhibits tumor growth by inducing apoptosis of rat pituitary prolactin-secreting tumor directly via the damage of mitochondria.

[Association between polymorphisms of XPD gene and susceptibility to chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphisms of XPD gene and susceptibility to chronic benzene poisoning. METHODS: A case control study was conducted. Eighty patients diagnosed with chronic benzene poisoning and 62 workers occupationally exposed to benzene who were engaged in the same working time and job title as patients were investigated. PCR-RFLP was used for detecting the single nucleotide polymorphisms (SNPs) on codon156, codon312 and codon751 of XPD gene. RESULTS: There was a 2.903 times (95% CI: 1.054 - 7.959, P = 0.039 2) increased risk of chronic benzene poisoning in the subjects carrying XPD 751Gln variant allele compared with those carrying XPD 751Lys/Lys genotype, after adjusted for sex, length of service, smoking and drinking status. CONCLUSION: The subjects with XPD 751Gln variant allele are more susceptive to benzene.

[Effects of different modes of artificial ventilation on lung injury in dog model of acute respiratory distress syndrome].

OBJECTIVE: To investigate the effects of different modes of artificial ventilation on lung injury in a dog model of acute respiratory distress syndrome (ARDS), and to evaluate the protective effect of various parameters in mechanical ventilation on lung injury. METHODS: Thirty-six healthy dogs were randomly divided into normal control group (N group), ARDS group (M group) and ventilation group (A-D groups) based on a series of random number. The ARDS dog model was replicated by intratracheal instillation of hydrochloric acid, and mechanical ventilation was carried out according to the following ventilatory protocols. A group: low V(T) (6 ml/kg) with respiratory rate 30/minutes, low inspiratory flow 6 ml.kg(-1).s(-1). B group: large V(T) (20 ml/kg) with respiratory rate 30/minutes, high inspiratory flow 20 ml.kg(-1).s(-1). C group: large V(T) (20 ml/kg) with respiratory rate 15/minutes, high inspiratory flow 17 ml.kg(-1).s(-1). D group: large V(T) (20 ml/kg) with respiratory rate 15/minutes, low inspiratory flow 10 ml.kg(-1).s(-1). Lung mechanical parameters were recorded at 0, 1, 2 and 4 hours after the change in ventilatory protocol. After 4 hours of mechanical ventilation, animals were sacrificed, and the lung was harvested. Lung wet/dry weight ratio (W/D) was measured. Histopathological changes were observed under light microscope, diffuse alveolar damage (DAD) scores was estimated, and polymorphonuclear leucocytes (PMN) count was done. Nuclear factor-KappaB (NF-KappaB) p65 activity was assessed by flow cytometry. RESULTS: W/D in B group (9.95+/-0.99) was higher than that of A (6.78+/-0.56) and D (7.11+/-0.47) groups (both P<0.01),but there was no significant difference between B and C groups (9.22+/-1.19, P>0.05). DAD scores in B group (12.80+/-1.47) was obvious higher than that of A (7.67+/-1.20) and D (8.83+/-1.17) groups (both P<0.01), but there was no difference compared with C group (11.50+/-1.87, P>0.05). NF-KappaB p65 activity in B group [(33.56+/-2.85)%] was significantly higher than that of A [(10.35+/-0.60)%] and D [(10.79+/-1.02)%] groups, but there was no difference between B and C [(30.87+/-1.16)%] groups. CONCLUSION: Large tidal volumes with high inspiratory flow and high respiratory rate may cause severe ventilator induced lung injury (VILI). Reduction of inspiratory flow and respiratory rate with large tidal volume ventilation may provide pulmonary protection.

Inhibitory effects of melatonin on the growth of pituitary prolactin-secreting tumor in rats.

The in vivo effects of melatonin on proliferation and apoptosis of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) were investigated in rats kept in 12 L/12 D (lights on: 06:00-18:00 hr). As melatonin was shown to induce apoptosis of breast and liver tumor cells, we examined whether melatonin would induce apoptosis of rat pituitary prolactinoma cells. 0.125, 0.25, 0.50 or 1.0 mg melatonin/day/rat was administrated subcutaneously at 17:30-18:00 hr. The weight of prolactinomas was measured. Apoptosis was evaluated using the TdT-mediated dUTP nick-end labeling method. It was found that treatment with 0.25 and 0.50 mg melatonin for 97 days inhibited prolactinoma cell proliferation and increased prolactinoma cell apoptosis. Furthermore, melatonin induced mRNA expression of Bax and cytochrome c protein expression. Conversely, mRNA expression of Bcl-2, and mitochondrial membrane potential were inhibited by melatonin treatment. These results suggest that melatonin inhibits the proliferation and induces apoptosis of rat pituitary prolactin-secreting tumor via perturbation of mitochondria physiology.

[Melatonin suppressing the proliferation of E2-induced pituitary prolactin-secreting tumor in rat involves the effects of estrogen receptor].

AIM: To investigate effects of melatonin on estrogen receptor at the primary stage of melatonin (MLT) inhibiting the proliferation of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) and its mechanisms in the rat. METHODS: MLT inhibiting the proliferation of 17-beta-E2-induced prolactinoma was created by administrating different concentration of melatonin subcutaneously at 18:00 in every group of SD rat in vivo. We also examined the expression of MLT receptor in prolactinoma cells and the effects of MLT on the expression of estrogen receptor (ER) by in situ hybridization and the effects of MLT on the binding of ER to estrogen response element (ERE) by electrophoretic mobility shift assay (EMSA)in primary culture cells iv vitro. RESULTS: The results showed that the weights of prolactinomas in MLT groups, in which 0.25 mg or 0.50 mg/day/rat melatonin was administrated subcutaneously at 18:00, were decreased significantly (P < 0.01 and P < 0.05). The expression of MLT1a and MLT1b were shown in pituitary prolactinoma cells. Compared with the prolactinoma, the expression of ER and the bind of ER to ERE in prolactinoma treated with 0.25 mg/day/rat or 0.50 mg/day/rat MLT was decreased (P < 0.01 and P < 0.01). CONCLUSION: These data indicate that some dosage of MLT inhibit the development of E2-induced prolactinoma in SD rat. One of the mechanisms is involved in suppressing the expression of estrogen receptor and partly inhibiting the bind of ER to ERE.

[Genetic polymorphisms of NQO1, GSTT1, GSTM1 and susceptibility to chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphism of quinone oxidoreductase 1 (NQO1), glutathione S-transferase theta 1 (GSTT1), glutathiones S-transferase mu 1 (GSTM1) and susceptibility to chronic benzene poisoning (BP). METHODS: The genotypes of NQO1, GSTT1, GSTM1 for 100 patients with benzene poisoning and 90 workers exposed to benzene who were engaged in the same working time and job title as patients with benzene poisoning were detected by PCR-RFLP and multi-PCR. RESULTS: There was a 2.82-fold (95% CI: 1.42 approximately 5.58, P < 0.05) increased risk of BP in the subjects with NQO1 C609T mutation genotype (T/T) compared with those carrying heterozygous (C/T) and wild type (C/C), and there was a 2.94-fold (95% CI: 1.25 approximately 6.90, P < 0.05) increased risk of BP in the subjects with NQO1 C609T T/T genotype compared with those carrying C/C genotype. The subjects with GSTT1 null genotype had a 1.91-fold (95% CI: 1.05 approximately 3.45, P < 0.05) increased risk of BP compared with those with GSTT1 non-null genotype. The interaction of two genes showed that there was a increased risk of BP in subjects with any two genotypes of NQO1 C609T T/T genotype and GSTT1 null genotype and GSTM1 null genotype, compared to the individual with any two genotypes of NQO1 C609T C/C genotype and GSTT1 non-null genotype and GSTM1 non-null genotype. The interaction of three genes showed that there was a 20.41-fold (95% CI: 3.79 approximately 111.11, P < 0.01) increased risk of BP in subjects with NQO1 C609T T/T genotype and GSTT1 null genotype and GSTM1 null genotype compared with those carrying NQO1 C609T C/T genotype and C/C genotype and GSTT1 non-null genotype and GSTM1 non-null genotype. CONCLUSIONS: The interaction of multi-genes may be an important role to BP. The genetic polymorphisms of 3 genes (NQO1, GSTT1 and GSTM1) led to declining of detoxifying ability in benzene metabolism, so the individual with NQO1 C609T T/T genotype, GSTT1 null genotype and GSTM1 null genotype is most susceptive to benzene. The results were consistent with that of the theoretic presumption. It could be suggested as a biomarker to assess the risk of benzene poisoning for individuals.

Genes differentially expressed in human lung fibroblast cells transformed by glycidyl methacrylate.

OBJECTIVE: To define the differences in gene expression patterns between glycidyl methacrylate (GMA)-transformed human lung fibroblast cells (2BS cells) and controls. METHODS: The mRNA differential display polymerase chain reaction (DD-PCR) technique was used. cDNAs were synthesized by reverse transcription and amplified by PCR using 30 primer combinations. After being screened by dot blot analysis, differentially expressed cDNAs were cloned, sequenced and confirmed by Northern blot analysis. RESULTS: Eighteen differentially expressed cDNAs were cloned and sequenced, of which 17 were highly homologous to known genes (homology = 89%-100%) and one was an unknown gene. Northern blot analysis confirmed that eight genes encoding human zinc finger protein 217 (ZNF217), mixed-lineage kinase 3 (MLK-3), ribosomal protein (RP) L15, RPL41, RPS 16, TBX3, stanniocalcin 2 (STC2) and mouse ubiquitin conjugating enzyme (UBC), respectively, were up-regulated, and three genes including human transforming growth factor beta inducible gene (Betaig-h3), alpha-1,2-mannosidase 1A2 (MAN 1A2) gene and an unknown gene were down-regulated in the GMA-transformed cells. CONCLUSION: Analysis of the potential function of these genes suggest that they may be possibly linked to a variety of cellular processes such as transcription, signal transduction, protein synthesis and growth, and that their differential expression could contribute to the GMA-induced neoplastic transformation.

Genotoxic and nongenotoxic effects of glycidyl methacrylate on human lung fibroblast cells.

OBJECTIVE: To evaluate the genotoxic and nongenotoxic effects of short-term exposure to glycidyl mathacrylate (GMA) on human lung fibroblast cells (2BS cells) in vitro. METHODS: DNA strand breakage was determined by single cell gel electrophoresis, and DNA ladder formation assay and flow cytometric analysis were carried out to detect apoptic responses of cells to GMA exposure. The HPRT gene mutation assay was used to evaluate the mutagenicity, and the effect of GMA on gap junctional intercellular communication (GJIC) in the exposed cells was examined with the scrape loading/dye transfer technique. The ability of GMA to transform 2BS cells was also tested by an in vitro cell transformation assay. RESULTS: Exposure to GMA resulted in a dose-dependent increase in DNA strand breaks but not apoptic responses. GMA was also shown to significantly induce HPRT gene mutations and morphological transformation in 2BS cells in vitro. In contrast, GMA produced a concentration-dependent inhibition of GJIC. CONCLUSIONS: GMA elicits both genotoxic and nongenotoxic effects on 2BS cells in vitro. The induction of DNA damage and gene mutations and inhibition of GJIC by GMA may casually contribute to GMA-induced cell transformation.

[Effect of the polymorphism of myeloperoxidase gene on the risk of benzene poisoning].

OBJECTIVE: To study the relationship between the polymorphism myeloperoxidase (MPO) gene and the genetic susceptibility to benzene toxicity in workers exposed to benzene and in patients with benzene poisoning. METHODS: Using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) techniques, the genotypes' polymorphism of MPO gene in 35 patients with chronic benzene poisoning, 46 workers exposed to benzene from the same workplace (as exposed control) and 26 controls were analyzed. RESULT: There were three (G/G, G/A and A/A) genotypes in the region of 463 bp upstream of MPO gene. The distribution frequency in G/G wild-type genotype in patients was 27.4% more than that in the exposed workers. The risk of benzene-hematotoxicity in those with G/G genotype was 2.8-fold higher than G/A + A/A genotype (OR = 2.835, 95% CI: 1.065 - 7.549, P < 0.05). The polymorphism of myeloperoxidase was not associated with gender specific. CONCLUSION: In the same benzene-exposed environment, the subjects with MPO-463 G/G genotype may be more susceptible to benzene toxicity.