Chromosomal aberrations and SCEs as biomarkers of cancer risk.

Previous studies have suggested that the frequency of chromosomal aberrations (CAs), but not of sister chromatid exchanges (SCEs), predicts cancer risk. We have further examined this relationship in European cohorts comprising altogether almost 22,000 subjects, in the framework of a European collaborative project (CancerRiskBiomarkers). The present paper gives an overview of some of the results of the project, especially as regards CAs and SCEs. The results confirm that a high level of CAs is associated with an increased risk of cancer and indicate that this association does not depend on the time between CA analysis and cancer detection, i.e., is obviously not explained by undetected cancer. The present evidence indicates that both chromatid-type and chromosome-type CAs predict cancer, even though some data suggest that chromosome-type CAs may have a more pronounced predictive value than chromatid-type CAs. CA frequency appears to predict cancers at various sites, although there seems to be a particular association with gastrointestinal cancers. SCE frequency does not appear to have cancer predictive value, at least partly due to uncontrollable technical variation. A number of genetic polymorphisms of xenobiotic metabolism, DNA repair, and folate metabolism affect the level of CAs and might collectively contribute to the cancer predictivity of CAs. Other factors that may influence the association between CAs and cancer include, e.g., exposure to genotoxic carcinogens and internal generation of genotoxic species. Although the association between CA level and cancer is seen at the group level, an association probably also exists for the individual, although it is not known if an individual approach could be feasible. However, group level evidence should be enough to support the use of CA analysis as a tool in screening programs and prevention policies in occupational and environmental health.

[Validity of chromosome analysis and bleomycin sensitivity assay in the prevention of head and neck cancer in Hungary]. / A kromoszómaanalízis és a bleomycin-teszt hazai alkalmazhatóságának vizsgálata a fej-nyaki laphámrák prevenciójában.

Because of unfavourable cancer mortality statistics of Hungary, the search of different biomarkers is one of the most important demands of the national primary cancer prevention programme. The aim of this study was to clarify the usefulness of bleomycin sensitivity assay elaborated in the USA, and to find whether it serves under our environmental conditions as a biomarker of individual sensitivity and risk for head and neck cancer, beside chromosomal aberration analysis. The test reflecting mutagen sensitivity is based on the mean values of chromatid breaks induced by bleomycin in vitro in a single lymphocyte (break/cell = b/c). Since cancer formation is influenced by environmental mutagens, in contrast to others, their 111 head and neck cancer patients were matched not only with 230 healthy controls (106 nonsmokers and 124 smokers), but also with 44 strong alcoholic and smoking patients with liver diseases whose lifestyle did not differ from that of the cancer patients. According to the results of conventional chromosome analysis, the aberrant cell frequency was the highest in the cancer patients (3.34%), while in the alcoholics (2.73%) and healthy smokers (2.88%) the values were similar. Thus, the genetic instability occurring in the form of elevated rate of spontaneous chromosomal aberrations was mostly expressed in head and neck cancer patients. Mutagen sensitivity measured by the b/c values of bleomycin assay was significantly higher in both the cancer (1.16 b/c) and the alcoholic patients (1.34 b/c) compared with the controls (1.0 b/c). The bleomycin sensitivity assay, therefore, seems to be the biomarker not only of cancer, but also the disease of the same etiology such as alcohol-related liver disease. However the method is not suitable for the assessment of individual cancer risk because of the high variability of b/c values in each group, and their considerable overlapping with the controls. It can also be supported with extremely high mutagen sensitivity of Hungarian controls (63 and 67%), which is three-fold of US values (23%). The bleomycin sensitivity assay is not a selective biomarker if comparing to the controls, probably due to the action of more complex exposures under Hungarian environmental conditions. When estimating cancer risk, the results of conventional chromosome analysis offer more information than bleomycin sensitivity assay.

[Exposure or cancer predisposition? Cytogenetic examination of head and neck squamous cancer patients] / Expozíció vagy rákhajlam? Fej-nyaki laphámrákos betegek citogenetikai szûrése.

Search of different biomarkers is one of the most important demands of the national cancer prevention programme. We examined the usefulness of bleomycin sensitivity assay, whether it serves as a biomarker of individual sensitivity and risk for head and neck cancer under our environmental conditions. The test is based on the measurement of the means of chromatid breaks induced by bleomycin in vitro in a single lymphocyte (break/cell=b/c). 156 head and neck cancer patients were matched not only with 295 healthy controls (146 non-smokers and 149 smokers), but also with 51 strong alcoholic and smoking patients with liver disease whose lifestyle did not differ from that of the cancer patients. The aberrant cell frequency of cancer patients (2.85%), alcoholics (2.82%) and healthy smokers (2.81%) was similar and higher (p<0.03) than the values of non-smoker controls (2.25%). Thus, the results of conventional chromosome analysis indicate the effect of exposure to mutagens, derived mainly from smoking. Mutagen sensitivity measured by the bleomycin assay was significantly higher in both the cancer- (1.13 b/c) and the alcoholic patients (1.29 b/c) compared with smoker (1.04 b/c) and non-smoker controls (0.98 b/c). The bleomycin sensitivity assay, therefore, seems to be the biomarker not only for the cancer, but also for a disease of the same aetiology such as alcohol-related liver disease. However, the method is not suitable for the assessment of individual cancer risk due to overlapping of b/c values with those of controls. The proportion of mutagen sensitive persons in the group of Hungarian controls is 42-49%, which is two-fold of those in the US and Western Europe. When we estimate the cancer risk, the results of bleomycin sensitivity assay are equivocal under our experimental conditions, and they must be applied cautiously even in combination with the results of chromosome analysis.

[Cytogenetic study of thyroid patients treated with external irradiation or radioiodine]. / Külsó sugárforrással, vagy radiojóddal kezelt pajzsmirigybetegek citogenetikai vizsgálata.

Where clinically permitted, either external irradiation or radioiodine therapy is usually recommended for the treatment of differentiated thyroid cancer patients. This paper describes an attempt to clarify the radiation burden and the distribution of radiation doses on the lymphocytes in consequence of these two therapeutic modalities, and the circumstances of the applicability of biological dosimetry. Thyrotoxic patients with intact thyroid glands underwent 131I therapy were also analysed for this purpose. An analysis was made of the extent to which exposure to local neck irradiation (50 Gy) or radioiodine therapy (1734-2600 MBq) causes chromosomal aberrations in the lymphocytes of thyroid disease patients after total or subtotal thyroidectomy, or thyrotoxic patients with intact thyroid glands (185-595 MBq). The irradiated volume of lymphatic tissues played the most important role in the formation of chromosomal aberrations. External irradiation caused 10-times more aberrant cells than 131I therapy did in cancer patients. In thyrotoxic patients the lower therapy doses of radioiodine caused a significantly higher frequency of aberrations than that observed in thyroid cancer patients. Selective radiosensitivity of lymphocytes was supported by the analysis of the Poisson distribution of aberrations, which suggested a homogeneous dose distribution only in 131I-treated and thyroidectomized cancer patients. In conclusion, we suggest that the results of studies of the genetic alterations in the lymphocytes exposed to radioiodine, under well-defined circumstances should not be ignored before the mode of radiation treatment is chosen. On the other hand, in the modelling of accidental environmental radioiodine exposure, only thyrotoxic patients with an intact thyroid gland and heterogeneous dose-distribution are a suitable group.

Cytogenetic study of radiation burden in thyroid disease patients treated with external irradiation or radioiodine.

Where clinically permitted, either external irradiation or radioiodine therapy is usually recommended for the treatment of differentiated thyroid cancer patients. The choice depends on the treatment philosophy of the responsible physician. This paper describes an attempt to clarify the radiation burden on the lymphocytes in consequence of these two therapeutic modalities. An analysis was made of the extent to which exposure to local neck irradiation (25 x 2 Gy) or radioiodine therapy (1734-2600 MBq) causes chromosomal aberrations in the lymphocytes of thyroid disease patients after total or subtotal thyroidectomy. External irradiation caused many more chromosomal aberrations than 131I therapy did, but analysis of the distribution of the aberrations suggested a homogeneous dose distribution only in 131I-treated and thyroidectomized cancer patients. In thyrotoxic patients with intact thyroid glands, the lower therapy doses (185-595 MBq) caused a significantly higher frequency of aberrations than that observed in thyroid cancer patients, and the dose distribution in the lymphocytes was inhomogeneous. Thus, in the modelling of accidental environmental radioiodine exposure, thyroid patients with small if any residual thyroids are not a suitable group.

A study of children, fathered by men treated for testicular cancer, conceived before, during, and after chemotherapy.

One hundred fifty children of 113 fathers with testicular tumour treated from 1979 on the National Institute of Oncology, Budapest, were studied. Three groups were formed on the basis of the time of conception; 69 children were born before the illness of the fathers, 40 during the 12 pretreatment months, and 41 during or after combined chemotherapy. One hundred fifty control children underwent tonsillectomy/appendectomy, but were otherwise healthy. They were matched according to age, sex, and place of inhabitance with index children. Family anamnesis, perinatal, and gestational data were listed; thereafter, physical, laboratory, immunological, and, if required, radiological examinations were made. No difference was detectable in the somatic and psychiatric status of the three groups, and development was well balanced, corresponding to age. Protocols of the combined chemotherapy applied, and the incidence of anomalies, abnormalities, malignancies, and other diseases was recorded. Incidence was similar in all three groups. Incidence of congenital malformations was not increased in children conceived before and after therapy; however, a complex congenital abnormality, an atrial septal defect with horseshoe kidney, occurred in one young girl, conceived after the end of her father's treatment. The interval between conception and the end of therapy was established in the case of children conceived either during or after therapy. This was shorter in the case of healthy children; the number of healthy children conceived during cytostatic treatment was also remarkable. Further detailed analysis of data and individual evaluation of case reports are recommended.

[Spontaneous and cytostatic therapy induced chromosome aberrations in testicular cancer patients]. / Heretumoros betegek spontán és citosztatikus kezelést követö kromoszóma aberrációi.

Chromosomal aberrations were studied in peripheral blood lymphocytes from only surgery treated testicular cancer patients and treated with chemo- and/or radiotherapy. A distinct increase in spontaneous aberration frequency over the level of 27 healthy controls in 27 patients treated with surgery alone was found. Our data suggest the existence of a certain degree of chromosome instability, which may be a factor to the development of testicular tumour. The frequency of aberrant cells was much higher in 102 treated patients than in the controls. The decrease in aberrant cells was only time-dependently gradual in VPB and X-ray treated patients, while the second line combined treatment modalities caused the highest frequency of aberrant cells in the first two years after the end of courses. The possible relationship between the persistence of chromosomal aberrations and the development of malignancies are discussed in this paper.

Persistence of chromosomal aberrations in blood lymphocytes of testicular cancer patients. II. The effect of chemotherapy and/or radiotherapy.

Chromosome aberrations were studied in peripheral blood lymphocytes from untreated testicular cancer patients and others treated with chemo- and/or radiotherapy. A distinct increase in spontaneous aberrations over the level of healthy controls was found in patients treated with surgery alone. Our data suggest the existence of a certain degree of chromosome instability which may be a factor in the development of malignancy for testicular tumours, too. The frequency of aberrant cells was much higher in treated groups than in controls, and the total of aberrations was therapy related. The frequency of aberrant cells was the highest in the first 2 years after the end of treatments similarly to the results of 3 serially examined individuals. The decrease in aberrant cells was time-dependently gradual only in X-ray-treated patients. Real conclusions about the nature of therapy-related persistence of aberrant cells can be drawn from the study of a sufficient number of testicular cancer patients studied more than 1 year after the end of treatments.

Children fathered by men treated for testicular cancer conceived before, during and after chemotherapy--examination for evidence of congenital malformations, malignancies and immunological defects.

Hundred children of 64 fathers with testicular tumour treated from 1979 on at the National Institute of Oncology, Budapest were studied. Three groups were formed on the basis of the time of conception. 59 children were born before the illness of the fathers, 19 during the 9 pretreatment months and 22 during or after combined chemotherapy. Family anamnesis, perinatal and gestational data were listed, thereafter physical, laboratory, immunological, psychiatric, and, if required, radiological examinations were made. No difference was detectable in the somatic and psychiatric status of the three groups, development was well balanced, corresponding to age. Protocols of the combined chemotherapy applied and incidence of anomalies, malformations, malignancies and other diseases were recorded. Their incidence was similar in all three groups though frequently this was higher than that of the normal population. Often cumulated incidence of severe congenital malformations was found in the group conceived after concluded therapy where twice as many girls were born as boys. The interval between conception and the end of therapy was established in the case of children conceived during and after therapy. This was shortest in the case of healthy children, the number of healthy children conceived during cytostatic treatment was also remarkable. Further compilation of data and individual evaluation of case reports is recommended.

Persistence of chromosomal aberrations in blood lymphocytes of testicular cancer patients. I. The effect of vinblastine, cisplatin and bleomycin adjuvant therapy.

Chromosomal aberrations and sister chromatid exchanges were examined in 45 patients with nonseminomatous testicular cancer at different times after the termination of vinblastine, cisplatin and bleomycin (VPB) therapy and in 22 age-matched healthy men and untreated testicular cancer patients. After 36 months, the frequency of unstable aberrations markedly decreased in peripheral blood lymphocytes of VPB-treated patients, however the persistence of aberrant cells even 75 months after the termination of treatment underlines the necessity of longer follow-up of VPB-treated patients in order to evaluate the relationship between their carcinogen sensitivity and the risk of second malignancies.

Vinblastine, cisplatin and bleomycin (VPB) adjuvant therapy does not induce dose-dependent damage in human chromosomes.

Chromosome aberrations and sister chromatid exchanges were examined in testicular tumor patients treated by 4 cycles of vinblastine, cisplatin and bleomycin adjuvant therapy. The predominant aberrations in cells varied among the patients, and due to interindividual variability no time- or dose-dependent changes were observed in cytogenetic data. There was found an overdispersion of aberrations which might be explained by the effect of bleomycin. Sister chromatid exchange (SCE) frequency was slightly increased and showed also an individual variability in the response to vinblastine, cisplatin and bleomycin (VPB) therapy. No correlation with chromosome aberration rate was found. Further data are required for the real estimation of long-term effects of VPB therapy.

Cytogenetical studies on a large control population and on persons occupationally exposed to radiation and/or to chemicals.

Nowadays all people are exposed to mutagens environmentally, occupationally, therapeutically or due to life style. In order to validate any conclusions concerning a possible effect of some kind of these mutagens to the relevant exposed groups, chromosomal analysis was carried out on a standard population (211 persons) distributed randomly from biological and social points of view and on 163 persons, occupationally exposed to different kinds of mutagens. Analysis proved that the mean frequency of chromosomal aberrations (CA) of control was 0.81% and it was similar before and following the Chernobyl events. Data concerning the CA frequency in people exposed occupationally to low doses of ionizing radiations below the internationally accepted permissible level, showed a 2-6-fold increase of aberrant cells. Occupational exposure to chemical mutagens such as vinyl-chloride and organic solvents like benzene and toluene revealed 2-4 times higher frequency of CAs than the control; however, exposures to organophosphorus insecticides reached a 5-6-fold increase in CAs as well. The sister chromatid exchange (SCE) frequency data were in each exposed group higher than the control values. Neither chromosomal aberration frequencies, nor sister chromatid exchanges differed significantly between smokers and non smokers in control and exposed persons.

Sister chromatid exchange frequency in human lymphocytes exposed to ionizing radiation in vivo and in vitro.

This paper reports statistically significant elevations in peripheral blood lymphocyte sister chromatid exchange frequencies in persons occupationally exposed to low levels of ionizing radiation when compared with unexposed persons. Low doses of X or gamma rays administered in vitro also produce significant elevations in sister chromatid exchange frequencies, though the magnitude of the increases is dependent upon culture medium and other factors.