Chromosomal aberrations in peripheral lymphocytes of train engine drivers.

Studies of Swedish railway employees have indicated that railroad engine drivers have an increased cancer morbidity and incidence of chronic lymphatic leukemia. The drivers are exposed to relatively high magnetic fields (MF), ranging from a few to over a hundred microT. Although the possible genotoxic potential of MF is unclear, some earlier studies have indicated that occupational exposure to MF may increase chromosome aberrations in blood lymphocytes. Since an increased level of chromosomal aberrations has been suggested to predict elevated cancer risk, we performed a cytogenetic analysis on cultured (48 h) peripheral lymphocytes of Swedish train engine drivers. A pilot study of 18 engine drivers indicated a significant difference in the frequency of cells with chromosomal aberrations (gaps included or excluded) in comparison with seven concurrent referents (train dispatchers) and a control group of 16 office workers. The engine drivers had about four times higher frequency of cells with chromosome-type aberrations (excluding gaps) than the office workers (P < 0.01) and the dispatchers (P < 0.05). Seventy-eight percent of the engine drivers showed at least one cell per 100 with chromosome-type aberrations compared with 29% among the dispatchers and 31% among the office workers. In a follow-up study, another 30 engine drivers showed an increase (P < 0.05) in the frequency of cells with chromosome-type aberrations (gaps excluded) as compared with 30 referent policemen. Sixty percent of the engine drivers had one or more cells (per 100 cells) with chromosome-type aberrations compared with 30% among the policemen. In conclusion, the results of the two studies support the hypothesis that exposure to MF at mean intensities of 2-15 microT can induce chromosomal damage.

Cancer predictive value of cytogenetic markers used in occupational health surveillance programs: a report from an ongoing study by the European Study Group on Cytogenetic Biomarkers and Health.

The cytogenetic endpoints in peripheral blood lymphocytes: chromosomal aberrations (CA), sister chromatid exchange (SCE) and micronuclei (MN) are established biomarkers of exposure for mutagens or carcinogens in the work environment. However, it is not clear whether these biomarkers also may serve as biomarkers for genotoxic effects which will result in an enhanced cancer risk. In order to assess this problem, Nordic and Italian cohorts were established, and preliminary results from these two studies indicated a predictive value of CA frequency for cancer risk, whereas no such associations were observed for SCE or MN. A collaborative study between the Nordic and Italian research groups, will enable a more thorough evaluation of the cancer predictivity of the cytogenetic endpoints. We here report on the establishment of a joint data base comprising 5271 subjects, examined 1965-1988 for at least one cytogenetic biomarker. Totally, 3540 subjects had been examined for CA, 2702 for SCE and 1496 for MN. These cohorts have been followed-up with respect to subsequent cancer mortality or cancer incidence, and the expected values have been calculated from rates derived from the general populations in each country. Stratified cohort analyses will be performed with respect to the levels of the cytogenetic biomarkers. The importance of potential effect modifiers such as gender, age at test, and time since test, will be evaluated using Poisson regression models. The remaining two potential effect modifiers, occupational exposures and smoking, will be assessed in a case-referent study within the study base.

Cancer predictive value of cytogenetic markers used in occupational health surveillance programs.

It has not previously been clear whether cytogenetic biomarkers in healthy subjects will predict cancer. Earlier analyses of a Nordic and an Italian cohort indicated predictivity for chromosomal aberrations (CAS) but not for sister chromatid exchanges (SCES). A pooled analysis of the updated cohorts, forming a joint study base of 5271 subjects, will now be performed, allowing a more solid evaluation. The importance of potential effect modifiers, such as gender, age at testing, and time since testing, will be evaluated using Poisson regression models. Two other potential effect modifiers, occupational exposures and smoking, will be assessed in a case-referent study within the study base.

Prognostic impact of bone marrow karyotype in childhood acute lymphoblastic leukaemia: Swedish experiences 1986-91.

The prognostic value of cytogenetic classification in acute lymphoblastic leukaemia (ALL) was evaluated in Swedish children below 16 years of age (n = 372) diagnosed between 1986 and 1991. A bone marrow karyotype was obtained in 281 cases, of which 149 (53%) showed clonal abnormalities. Event-free survival (p-EFS) was 0.64-0.69 in patients with diploid and pseudodiploid karyotype. Patients with massive hyperdiploidy (> 50 chromosomes) had the best outcome (p-EFS = 0.76) and those with hypodiploidy (< 46 chromosomes) had the worst (p-EFS = 0.33). White blood cell count and age were the strongest predictors of outcome. The karyotype reached borderline significance. The diagnostic karyotype was also a predictor of outcome after relapse, with hyperdiploid patients doing better than the others. The presence of a structural chromosomal abnormality did not constitute a negative prognostic factor when intensive chemotherapy was given.

Chromosomal changes in rheumatoid arthritis patients treated with CPH82.

Chromosomal changes were assessed in 19 patients with rheumatoid arthritis (RA) treated with CPH82, a benzylidated podophyllotoxin glycoside, for up to one year. The frequency of chromosomal aberrations (CA) and sister chromatid exchanges (SCE) in peripheral lymphocytes increased significantly after 12 weeks of treatment and remained elevated after 48 weeks treatment in peripheral lymphocytes. The number of CA and SCE were significantly increased in CPH82 treated patients compared with the RA patients treated with other disease modifying anti-rheumatic drug (sulphasalazine, gold, D-penicillamine, azathioprine, methotrexate, cyclophosphamide). Only two patients treated with cyclophosphamide and azathioprine had changes of comparable levels. The results of this study suggest a mutagenic potential of CPH82 similar to that described for other immunosuppressive drugs and the newer podophyllotoxin derivatives, etoposide and teniposide.

Myelodysplastic syndromes--a population-based study on transformation and survival.

A retrospective analysis was done on 113 patients (median age 73 years) with myelodysplastic syndromes (MDS), consecutively diagnosed at our center during a 10-year period. Patients with refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) had significantly longer survival than patients with refractory anemia with excess blasts (RAEB), chronic myelomonocytic leukemia (CMML) or refractory anemia with excess blasts in transformation (RAEB-T). Thirty-seven patients (33%) subsequently developed acute myelogenous leukemia (AML). The percentages of AML transformation for the subgroups were: RA: 26%, RARS: 14%, RAEB: 38%, CMML: 25% and RAEB-T: 69%. A total of 9 patients received high-dose chemotherapy, 7 of them already at the time of MDS diagnosis. Six of the RAEB-T patients entered complete and two partial remission. The median age in the group of RAEB-T patients was significantly lower (62 years) than in the other MDS subgroups. It seems that high-dose chemotherapy, at least in RAEB-T, may induce complete remission and improve survival time.

Cancer risk in humans predicted by increased levels of chromosomal aberrations in lymphocytes: Nordic study group on the health risk of chromosome damage.

Cytogenetic assays in peripheral blood lymphocytes (PBL) have been used extensively to survey the exposure of humans to genotoxic agents. The conceptual basis for this has been the hypothesis that the extent of genetic damage in PBL reflects critical events for carcinogenic processes in target tissues. Until now, no follow-up studies have been performed to assess the predictive value of these methods for subsequent cancer risk. In an ongoing Nordic cohort study of cancer incidence, 3182 subjects were examined between 1970 and 1988 for chromosomal aberrations (CA), sister chromatid exchange or micronuclei in PBL. In order to standardize for the interlaboratory variation, the results were trichotomized for each laboratory into three strata: low (1-33 percentile), medium (34-66 percentile), or high (67-100 percentile). In this second follow-up, a total of 85 cancers were diagnosed during the observation period (1970-1991). There was no significant trend in the standardized incidence ratio with the frequencies of sister chromatid exchange or micronuclei, but the data for these parameters are still too limited to allow firm conclusions. There was a statistically significant linear trend (P = 0.0009) in CA strata with regard to subsequent cancer risk. The point estimates of the standardized incidence ratio in the three CA strata were 0.9, 0.7, and 2.1, respectively. Thus, an increased level of chromosome breakage appears to be a relevant biomarker of future cancer risk.

Simultaneous immunoglobulin/T-cell receptor gene rearrangements and multiclonality in childhood acute lymphoblastic leukemia.

Twenty-five children less than 16 years of age with acute lymphoblastic leukemia (ALL) were investigated with immunologic, cytogenetic and molecular genetic techniques at diagnosis. All pre-B-cell ALL showed clonal rearrangements in the immunoglobulin heavy chain gene (JH and/or C mu). A very high proportion of the pre-B-cell leukemias (17 of 23 cases) also showed clonal rearrangements in T-cell receptor genes (T gamma and/or T beta). The two T-cell leukemias exhibited clonal T-cell receptor gene rearrangements and in one JH and kappa light chain rearrangements also. The T-cell receptor gene rearrangements found in pre-B-cell leukemias appeared to occur randomly with respect to the T beta and T gamma genes. A significant proportion of the leukemias (at least 24%) seemed to harbor more than one malignant (sub)clone at diagnosis. Cytogenetic studies revealed a clonal abnormality in 10 cases. Only 2 showed hyperdiploidy (> 50 chromosomes). The only correlation between cytogenetic findings and rearrangement patterns was extra bands corresponding to a possible trisomy of chromosome 14. Our data indicate, in line with previous studies, that childhood ALL has complex rearrangement patterns not useful for lineage sub-classification. For this purpose immunophenotyping appears to be superior. However, molecular analysis can reveal the presence of more than one clone not detected by immunophenotyping or karyotyping, and distribution of clones in different compartments. In this study no correlation with clinical outcome was observed.

Chromosomal aberrations in human amniotic cells after intermittent exposure to fifty hertz magnetic fields.

Our recent studies have shown a significant increase in the frequency of chromosomal aberrations in human amniotic cells after exposure to a sinusoidal 50 Hz, 30 microT (rms) magnetic field. To evaluate further interactions between chromosomes and electromagnetic fields, we have analyzed the effects of intermittent exposure. Amniotic cells were exposed for 72 h to a 50 Hz, 30 microT (rms) magnetic field in a 15 s on and 15 s off fashion. Eight experiments with cells from different fetuses were performed. The results show a 4% mean frequency of aberrations among exposed cells compared to 2% in sham-exposed cells. The difference is statistically significant, with P < 0.05 both excluding and including gaps. In another series of eight experiments, the cells were exposed in the same way but with the field on for 2 s and off for 20 s. Also in these experiments a similar increase in the frequency of chromosomal aberrations was seen, but only when the analysis included gaps. Continuous exposure for 72 h to 300 microT, 50 Hz, did not increase the frequency of chromosomal aberrations. The background electromagnetic fields at different locations within the two incubators used was carefully checked and was nowhere found to exceed 120 nT. Likewise, the background level of chromosomal aberrations in cells cultured at different locations in the incubators showed no significant interculture differences.

Ig-gene and T-cell receptor gene rearrangements in a secondary, mono-histiocytic malignancy.

In 1984, a 21-year-old male was diagnosed with an acute lymphoblastic leukemia of pre-B cell type. Treatment with chemotherapy, including alkylating agents and prophylactic radiotherapy to the central nervous system, induced a complete remission. In June 1990, a biopsy from a supraclavicular node revealed a malignancy of mono-histiocytic type with erythrophagocytosis. Soon thereafter bone marrow involvement was found. No remission was achieved and the patient died in December 1990. DNA from bone marrow and lymph node obtained 1990 showed clonal rearrangements of both the immunoglobulin heavy-chain gene and the T-cell receptor gamma chain gene. This unusual case illustrates a typical secondary malignancy proven to be separate from the primary neoplasm judged by morphological appearance, immunophenotype and cytogenetic constitution. Coexistent clonal rearrangements of immunoglobulin and T-cell receptor genes have been reported in acute non-lymphoblastic leukemias and notably in cases expressing TdT, interpreted as a predominant lymphoid commitment of the tumor cells. In the present case, however, the malignant cells had a differentiated phenotype and showed erythrophagocytosis, indicating a more mature mono-histiocytic cell type. However, also CD3 expression was found by immunohistochemistry of frozen sections which might indicate a biphenotypic malignancy.

Idiopathic hemochromatosis and chromosomal damage.

Spontaneous and radiation-induced chromosome damage in cultured lymphocytes was examined in a pilot study of 11 patients with idiopathic hemochromatosis and matched controls. Increased frequencies of chromosome breaks were found in the patients, both spontaneously and after exposure to ionizing radiation, but the differences between patients and controls were not statistically significant (p greater than 0.05) when individual data were analyzed. When pooled (group) data for patients and controls were compared, significant increases in spontaneous and radiation-induced chromosome breaks were found among the patients. The results suggest that iron overload may lead to chromosome damage in idiopathic hemochromatosis.

Multiple DNA rearrangements in the BCL2 region in a patient with follicular lymphoma.

A 39-year-old male with follicular non-Hodgkin's lymphoma was repeatedly studied with respect to DNA rearrangements with the two probes pFL-1 and pFL-2, representing two segments of chromosome 18. The oncogene BCL2, detected by pFL-1, was as expected translocated to the J region of the immunoglobulin locus. The standard BCL2 translocation was found in three samples, one obtained at diagnosis, one ten months later, and one after 5 years. Another translocation was found with the probe pFL-2 hybridizing with a region located about 20 kb 3' from BCL2. This latter rearrangement was found only in the first biopsy, which was obtained at the time of diagnosis, but not in the two later samples, when the morphology of the lymphoma was unchanged. No cytotoxic therapy had been given in the interval from diagnosis to disappearance of the latter rearrangement. Thus, one of the observed translocations (pFL-2) was detected only in the first biopsy, while the other (pFL-1) was a clonal marker in all three biopsies. The finding suggests that clonal evolution does not necessarily mean clinical progression.

Is the genotoxic effect of arsenic mediated by oxygen free radicals?

Previous investigations have shown that trivalent arsenic is inducing chromosomal aberrations and sister chromatid exchanges (SCEs). In a search for the genotoxic mechanism we have studied the effects of the oxygen-radical-scavenging enzymes superoxide dismutase (SOD) and catalase (CAT) on arsenic-induced SCEs in cultured human lymphocytes. The results indicate that SOD and possibly also CAT have a protective effect against arsenic-induced DNA damage. Arsenic, which is emitted in environmental pollutions e.g. from smelters and coal-fired power plants, appears to be underestimated as environmental mutagen and potential synergist to ionizing radiation.

Cytogenetic and flow cytometric DNA analysis in renal cell carcinoma.

Cytogenetic and flow cytometric DNA analyses were performed on 37 tumor samples from 16 patients with renal cell carcinoma. 36 cultures were chromosomally abnormal and 1 was normal. The most frequent abnormality was trisomy or tetrasomy of chromosome 7 (13 of 16 tumors), suggesting that this abnormality might be a primary change in renal cell carcinoma. Abnormalities of chromosome 3 were seen in 9 of 16 tumors (56%). Eight of 11 tumors (73%) with cytogenetic results from multiple tumor samples showed intratumor cytogenetic heterogeneity. Twelve of the 16 patients had aneuploid tumors, and 4 had homogeneously diploid tumors. DNA index correlated with chromosome number. No association was found between cytogenetic results and clinical stage.

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.

Fragility of the centromeric region of chromosome 1 associated with combined immunodeficiency in siblings. A recessively inherited entity?

Instability of the centromeric region of chromosome 1, and multibranched configurations formed by the short and long arms were seen in a brother and sister with facial dysmorphism, mental retardation and recurrent infections. No chromosomal abnormalities were seen in the parents, who were first cousins. The fragility of chromosome 1 was identified in amniotic fluid cells of the sister. A combined immunodeficiency characterized by a lack of immunoglobulin production, low numbers of T cells and a lack of cells with NK cell markers was diagnosed. This is the first report of familial occurrence of this unique chromosomal aberration. The cause may be an autosomal recessive gene defect.

An inter-Nordic prospective study on cytogenetic endpoints and cancer risk. Nordic Study Group on the Health Risk of Chromosome Damage.

To investigate whether high rates of chromosomal aberrations (CAs), sister chromatid exchange (SCE), or micronuclei(MN) in peripheral lymphocytes indicate an increased risk for subsequent cancer, a prospective cohort study of 2,969 subjects cytogenetically examined between 1970 and 1988 in four Swedish, two Finnish, and two Norwegian laboratories was initiated. To standardize for the interlaboratory variation, the results of the three cytogenetic endpoints were trichotomized for each laboratory into "low" (1st to 33rd percentile), "medium" (34th to 66th percentile), and "high" (67th to 100th percentile]. Thirty-four cancers had been diagnosed in the cohort during the observation period (1970 to 1985). The point-estimates of the standardized morbidity ratio (SMR) in the three CA strata were 90, 92, and 180, respectively. This trend for a positive association was not statistically significant (p = 0.06). There was no significant trend between SMR and the trichotomized rates of SCE. In the subcohort examined for MN only two cases of cancer had been diagnosed until now. If subjects with "high" frequencies of CA or SCE have a two-fold (or greater) risk of developing cancer as compared with individuals who have "medium" or "low" frequencies, we estimate that there is a likelihood of 80% and 70%, respectively, that this will be detectable as significant (p less than or equal to 0.05) differences after a further follow-up period of 5 years. Weaker associations between cancer risk and the cytogenetic endpoints would not be possible to evaluate until even later follow-ups.

The effect of CPH 82 on the growth of human lymphocytes in vitro. Definition of cytobiological action.

A drug composed of two semisynthetic podophylline derivatives, CPH 82, has recently been launched for the treatment of severe rheumatoid arthritis. The present in vitro study of PHA-stimulated human T-lymphocytes showed that CPH 82 arrested cell division in a metaphase-like configuration. The cell cycle effects of CPH 82 were indistinguishable from the cell cycle effects of the classical microtubule depolymerizers, Colcemid (a colchicine derivative) and podophyllotoxin. A CPH 82 concentration of 1 microgram/ml, which is close to therapeutic serum concentrations, had an almost maximal effect on cell division. It is suggested that at least part of the anti-inflammatory effect of CPH 82 is due to a colchicine-like activity on, for example, proliferating lymphocytes.

Philadelphia chromosome negative acute lymphoblastic leukemia preceding Philadelphia positive chronic myelogenous leukemia.

A patient with Philadelphia chromosome (Ph) negative acute lymphoblastic leukemia (ALL, FAB type L1) developed Ph-positive chronic myelogenous leukemia (CML) after more than 2 years in complete remission. Subsequently, Ph-positive lymphoblastic transformation occurred, which was again successfully treated. Thereafter, the CML state was interrupted twice more by blast crisis. The additional chromosomal abnormalities were atypical for Ph-positive CML. The course is interpreted as a possible example of the multistep development of CML. Blastic transformation occurring prior to the Ph chromosome has been reported in only two cases previously.

t(6;9) in bone marrow cells in two patients with sarcoidosis and acute myeloid leukemia.

A t(6;9) was seen in bone marrow aspirates from two patients with sarcoidosis who developed acute myeloid leukemia. This is a new observation not previously reported.