Cytochrome P4501B1 mediates induction of bone marrow cytotoxicity and preleukemia cells in mice treated with 7,12-dimethylbenz[a]anthracene.

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs) through many environmental pollutants, especially cigarette smoke. These chemicals cause a variety of tumors and immunotoxic effects, as a consequence of bioactivation by P-450 cytochromes to dihydrodiol epoxides. The recently identified cytochrome P4501B1 (CYP1B1) bioactivates PAHs but is also a physiological regulator, as evidenced by linkage of CYP1B1 deficiency to congenital human glaucoma. This investigation demonstrates that CYP1B1 null mice are almost completely protected from the acute bone marrow cytotoxic and preleukemic effects of the prototypic PAH 7,12-dimethylbenz[a]anthracene (DMBA). CYP1B1 null mice did not produce the appreciable amounts of bone marrow DMBA dihydrodiol epoxide DNA adducts present in wild-type mice, despite comparable hepatic inductions of the prominent PAH-metabolizing P-450 cytochrome, CYP1A1. Wild-type mice constitutively expressed low levels of bone marrow CYP1B1. These findings suggest that CYP1B1 is responsible for the formation of DMBA dihydrodiol epoxides in the bone marrow. Furthermore, this study substantiates the importance of DMBA dihydrodiol epoxide generation at the site of cancer initiation and suggests that tissue-specific constitutive CYP1B1 expression may contribute to cancer susceptibility in the human population.

Specific N-ras mutation in bone marrow within 48 H of 7,12-dimethylbenz[a]anthracene treatment in Huggins-Sugiyama rat leukemogenesis.

7,12-Dimethylbenz[a]anthracene (DMBA)-induced leukemias in Long-Evans rats consistently have an A --> T transversion at the second base of codon 61 in the N-ras gene. This mutation is also detected in the preleukemic stage. To determine when this specific N-ras mutation occurs in the early stages of leukemogenesis, we designed the mutant allele-specific amplification method, which was sensitive enough to detect one mutant cell among 10(6) normal cells. In the study reported here, N-ras mutation was found in bone-marrow cells 2 d after a single DMBA injection and thereafter throughout the preleukemic stage. These results show that DMBA induces a specific N-ras mutation soon after one DMBA injection and that this mutation is probably the first event in DMBA leukemogenesis.

Hair dye use and other risk factors for leukemia and pre-leukemia: a case-control study. Italian Leukemia Study Group.

A case-control study was carried out to examine the relation of three subtypes of leukemia cells and refractory anemia with excess of blasts to selected behavioral and environmental factors. Cases aged 15 years or older were recruited in three hospitals located in Rome, Bologna, and Pavia, respectively. Outpatients who were either normal or had nonneoplastic hematologic disorders and were seen in the same hospitals as the cases were enrolled as controls. Two hundred fifty-two patients with acute myeloid leukemia, 100 with acute lymphocytic leukemia, 111 with refractory anemia with excess of blasts, 156 with chronic myeloid leukemia, and 1,161 controls were included in the study. Refractory anemia with excess of blasts and chronic myeloid leukemia were included because they are regarded as forms of pre-leukemia. Odds ratio estimates were generally imprecise, but associations were suggested between specific case subtypes and exposure to dark hair dye, selected occupations (shoemaker, painter, electrician, child care), residence in houses built with tuff, and smoking. Although the exploratory nature of the study and its limited statistical power preclude firm conclusions, its results are consistent with those of previous studies, and are in general biologically plausible.

[Multicentric reticulohistiocytosis and myelodysplastic syndrome]. / Multizentrische Retikulohistiozytose und myelodysplastisches Syndrom.

Multicentric reticulohistiocytosis (MRH) is a rare disorder of skin and joints, and its aetiology is unknown. We describe a male patient who had first developed osteoblastic lesions of the skeleton in 1976 at the age of 59 years. Three years later, he presented with multiple papular and nodular skin lesions, predominantly on the limbs and upper trunk, and 4 years later he developed painful arthropathy. In 1988 skin examination showed multiple brownish-red papulo-nodules, some of which, at mechanically stressed areas, were ulcerated. The patient complained of pronounced arthrotic disorders with reduced joint mobility. Examination of biopsy specimens from active skin lesions demonstrated extensive numbers of macrophages with partial confluence to giant cells with typical ground-glass cytoplasm. Electron microscopy revealed phagocytosis of collagen-like-structures. Examination of bone marrow biopsy specimens revealed diffuse infiltration by histiocytic cells. The diagnosis made was therefore MRH. The patient was treated for several years with different therapeutic regimens, including azathioprin, dapsone, prednisolon, chlorambucil and cyclophosphamide, and complete remission of skin lesions and of bone marrow infiltration was observed. However, a myelodysplastic syndrome with refractory anaemia and ring sideroblasts developed, which is generally understood to be a preleukaemic condition. Myelodysplastic syndromes commonly develop between 3 and 10 years after the start of a therapy with antineoplastic agents.

Preleukemic proliferative changes in murine bone marrow after single and multiple 7,12-dimethylbenz(a)anthracene (DMBA)-applications.

The effect of a leukemia-inducing treatment on early changes in kinetic parameters of murine bone marrow cells were investigated. Mice were treated i.p. one, four and eight times at biweekly intervals with 1 mg DMBA. Up to nine weeks after the last injection, CFU-S number, proliferation ability of bone marrow cells (PF), cell doubling time (td) and the compartment ratio (CR) were measured. Following multiple DMBA injections, CFU-S number and PF were decreased whereas CR and td increased, thus indicating persisting stem cell injury and proliferative compensation in the hemopoietic amplification compartment. A single DMBA injection had no effect. It is concluded that a first DMBA injection induces cytotoxic (and genotoxic) damage in the bone marrow leading simultaneously to a strong proliferation stimulus and a hindered proliferation ability of HSC, some of which will be predisposed for further mutagenic treatment. The following DMBA injections meet strongly proliferating HSCs, thus enhancing the probability for the loss of proliferation control/terminal differentiation.

[The significance of beta 2-microglobulin for the diagnosis of preleukemic states in workers of the chemical industry]. / Znachenie beta 2-mikroglobulina dlia diagnostiki predleikoznykh sostoianii u rabochikh khimicheskoi promyshlennosti.

A study is presented of 89 workers contacting with benzene and its derivatives and 98 workers without contacts with chemical substances. Radioimmunological assay of peripheral blood B2-microglobulin was carried out. Persons with a length of work over 10 years contacting with anilin and its derivatives showed a marked increase of B2-microglobulin in the blood serum as well a marked reduction of leucocyte number. It is considered that leucopenia with granulocytopenia and marked increase of B2-microglobulin is regarded as a preleucosis state.

Cytogenetic abnormalities and leukemic transformation in hydroxyurea-treated patients with Philadelphia chromosome negative chronic myeloproliferative disease.

Eighty-one consecutive hydroxyurea-treated patients with Philadelphia (Ph) chromosome negative chronic myeloproliferative disease were followed prospectively from 1981 to 1989; 35 of them had polycythemia vera, 32 had essential thrombocythemia, 12 had myelofibrosis, and 2 had myeloproliferative syndromes. The 81 patients were treated with hydroxyurea for a total of 3,804 months during the observation time. Only three patients had been treated with alkylating agents or 32P before start of hydroxyurea treatment. Four patients transformed into acute myeloid leukemia or myelodysplastic syndromes; three of these patients had essential thrombocythemia, and one had a myeloproliferative syndrome. Two patients died of solid cancers. Five out of 53 evaluable patients (9%) had pretreatment clonal cytogenetic abnormalities involving chromosomes 1, 9, 20, and 21. At follow-up, during or after hydroxyurea treatment, 15% had cytogenetic abnormalities, an unexpectedly low frequency compared to the previously reported frequency in patients with polycythemia vera treated with alkylating agents. None of our patients who developed cytogenetic clonal changes during hydroxyurea therapy had polycythemia vera. However, follow-up is too short to draw any conclusions about the mutagenic potential of hydroxyurea compared to alkylating agents.

High risk of therapy-related leukemia and preleukemia after therapy with prednimustine, methotrexate, 5-fluorouracil, mitoxantrone, and tamoxifen for advanced breast cancer.

Therapy-related acute non-lymphocytic leukemia or preleukemia was observed in five of 71 patients with advanced breast cancer treated with combination chemotherapy comprising prednimustine, methotrexate, 5-fluorouracil, mitoxantrone, and tamoxifen. In this closely followed cohort of patients the cumulative risk of leukemic complications was 25.4% +/- 10.3% (+/- SE) 37 months after start of chemotherapy. The relative risk of overt leukemia was 339 (95% CI: 41-1223), as two cases were observed versus 0.0059 cases expected. The very high risk of leukemia and preleukemia observed may partly reflect the advanced age of the patients (mean, 61 years) and partly the diagnostic procedures used, which included cytogenetic screening of all patients developing refractory cytopenia. A particularly high leukemogenic effect of prednimustine or a synergism between prednimustine and other drugs used in this study cannot be excluded. In the light of the above results, the authors caution against the use of intensive combination chemotherapy with alkylating agents as in the current study in potentially curable patients with breast cancer.

Leukemia following chemotherapy for breast cancer.

Leukemia following chemotherapy for breast cancer was studied among patients diagnosed during 1973-1985 within the population-based tumor registries in the Surveillance, Epidemiology, and End Results Program. Among 13,734 women given initial chemotherapy, 24 developed acute nonlymphocytic leukemia (ANLL) compared to 2.1 expected based on general population rates (observed/expected = 11.5; 95% confidence interval = 7.4-17.1). Overall, 58 excess ANLL occurred per 100,000 women-years at risk for patients treated with chemotherapy. The cumulative incidence was 0.7% at 10 years. Risk remained high over all periods of observation up to 9 years after treatment. Among 7974 women treated only with surgery during 1973 and 1974, a period before the widespread use of adjuvant chemotherapy for breast cancer, ANLL was not significantly increased (observed = 7, expected = 5.1). A case-control study was then conducted in Connecticut to evaluate in more detail the risk associated with adjuvant chemotherapy in the general population. Among 20 cases (17 incident leukemias and 3 deaths due to preleukemia) and 60 matched controls, alkylating agents were linked to an 11.9-fold risk of ANLL and preleukemia (95% confidence interval = 2.6-55). Chemotherapy regimens including melphalan were related to a higher risk of leukemic conditions than those including cyclophosphamide. These data suggest that women in the general population treated with adjuvant chemotherapy for breast cancer are at an increased risk of leukemia, that the risk remains high among long-term survivors, and that risk differs by type of alkylating agent administered.

Development of leukemia after doxorubicin and cisplatin treatment for ovarian cancer.

Alkylating agents have been the major group of chemotherapeutic agents associated with an increased incidence of secondary leukemias. In ovarian cancer alkylating agents have resulted in a lesser, although still increased, risk of secondary malignancies. This paper reports two cases of ovarian cancer treated with cisplatin and doxorubicin (Adriamycin, Adria Laboratories, Columbus, OH), and the subsequent development of an acute nonlymphocytic leukemia and a preleukemia syndrome. This regimen does not contain alkylating agents, and has not been associated with leukemia in patients with ovarian cancer. In these two cases, abnormalities of chromosomes 5, 7, 11, and 17 are reported which have been shown to occur in therapy-related leukemia.

Myelodysplasia, chemical exposure, and other environmental factors.

This paper describes a case-control study of the occupational and environmental exposures of patients with myelodysplasia. The methodology, first described in Canada for solid tumors, estimates lifetime exposures to a number of potential toxic hazards or carcinogens. This pilot study confirms that the methodology, with the use of questionnaires and interviews, can estimate exposures to specific chemicals and shows some significant associations with myelodysplasia, including exposure to petrol or diesel compounds.

Clinicopathological study of hematological disorders after Thorotrast administration in Japan.

Ten leukemia and four aplastic anemia cases were clinicopathologically studied in autopsies from patients who had been administered the contrast medium, Thorotrast, three to five decades previously. The short period from the appearance of hematological symptoms to death, the relatively low percentage of leukemic cells in the peripheral blood, the high frequency of erythroleukemia, i.e., 50% of leukemia patients, and a case of atypical megakaryocyte proliferation were revealed in leukemia patients. Leukemic cell infiltration in the spleen tended to become slight or minimal with the progress of fibrosis. As a result, the degree of spleen swelling was mild or lacking in leukemia patients who had been administered Thorotrast. On the other hand, cases such as hyperplastic or normoplastic bone marrow, an increase in immature granulocytic series or no decrease in the number of megakaryocytes were observed in aplastic anemia of Thorotrast-administered patients. It was thought that fibrosis in the bone marrow as well as in the spleen was induced by Thorotrast deposition. Thus, in hematological disorders of Thorotrast-administered patients, both leukemia and aplastic anemia cases were considered to be mainly of the atypical type, and it was speculated that the damage due to Thorotrast may affect the hemopoietic stem cell level and hemopoietic microenvironment.

Murine thymic multicellular complexes during latency period after methylnitrosourea (MNU) injection.

The number of TNC complexes and of stroma cell-thymocyte rosettes was examined during the preleukemic period in mice given MNU to induce leukemia. In parallel, numbers of the complexes were studied following administration of hydrocortisone one day before administering MNU, i.e. after the procedure which clearly inhibited manifestation of induced leukemias. Administration of MNU with or without hydrocortisone is followed by disappearance of TNC complexes and stroma cell-thymocyte rosettes followed by their regeneration between 2 and 6 weeks after MNU. Relative rates of regeneration were different in MNU treated versus MNU + hydrocortisone treated animals.

Selective activation of endogenous ecotropic retrovirus in hematopoietic tissues of B6C3F1 mice during the preleukemic phase of 1,3-butadiene exposure.

1,3-Butadiene (BD), a comonomer used in the production of synthetic rubber, is a rodent carcinogen. We have observed a marked increase in the incidence of thymic lymphoma in male B6C3F1 relative to NIH Swiss mice chronically exposed to BD in the absence of demonstrable differences in bone marrow (target organ) toxicity. Increased expression of murine leukemia virus (MuLV) antigens was also observed on lymphomas from BD-exposed B6C3F1 mice. Because NIH Swiss mice do not usually express endogenous retroviruses and their ecotropic proviral sequences are not intact, these findings provide presumptive evidence of a role for endogenous retrovirus sequences in BD-induced lymphoma in the B6C3F1 mouse. The present study was conducted to examine the expression and behavior of endogenous retroviruses in these strains during the preleukemic phase of BD exposure. Chronic exposure to BD (1250 ppm) 6 hr/day, 5 days/wk for 3 to 21 weeks increased markedly the quantity of ecotropic retrovirus recoverable from bone marrow, thymus, and spleen of B6C3F1 mice. However, expression of other endogenous retroviruses (xenotropic, MCF-ERV) was not enhanced. No viruses of any type were found in similarly treated NIH Swiss mice. The mechanism of this increase in ecotropic retrovirus in B6C3F1 mice is believed to be de novo activation in greater numbers of cells because changes in the Fv-1 tropism of the replicating viruses or changes in Fv-1 host restriction were not found. Endogenous retroviruses are thus implicated in BD-induced leukemogenesis in B6C3F1 mice. Further studies will examine the role of retrovirus in BD-induced leukemogenesis and the mechanisms of activation of ecotropic proviral sequences in murine cells.

Translocations and deletions with breakpoint on 21q are nonrandomly associated with treatment-related acute nonlymphocytic leukemia and preleukemia.

Six of 70 (8.6%) consecutive cases with therapy-related acute nonlymphocytic leukemia (ANLL) or preleukemia had a translocation or deletion with a breakpoint on 21q. Such aberrations were seen in only one of 200 (0.5%) consecutive cases of de novo ANLL examined at our laboratory. The figures reflect a 17.1-fold increased incidence of 21q aberrations in therapy-related ANLL or preleukemia, compared with ANLL de novo. The difference is highly significant (p = 0.003). The increased incidence of 21q aberrations in therapy-related myelodysplastic syndromes was confirmed by literature studies. Band 21q22 was most often involved. Cases with t(8;21), which is strongly associated with the M2 variant of ANLL, or cases with i(21q), which is supposedly due to a centromeric misdivision, were not included in the count. It is concluded that the 21q aberrations are associated with treatment-related ANLL or preleukemia with at least the same degree of specificity as aberrations of #5 and #7.