Sister chromatid exchanges in smokers of high-tar cigarettes, low-tar cigarettes, cheroots and pipe tobacco

An Unusual Case of Multiple Malignancy in an Adult

An adult female is described who, during a clinical course of 25 years, presented malignant tumors of the rectum, breast, uterus and colon. Cytostatics were never administered. Lymphocyte subsets, a variety of lymphocyte and mononuclear cell stimulation assays with mitogens and antigens, DNA repair tests and activity of natural killer cells were normal. Serum leukocytic interleukin-1 activity was slightly elevated. Sister chromatid exchange frequency in peripheral lymphocytes was below the normal range. An explanation for the development of 4 primary malignant neoplasms was not found.

Sister chromatid exchange, (SCE), High-Frequency Cells (HFCs) and SCE distribution patterns in peripheral blood lymphocytes of Spanish adult smokers compared to non-smokers

According to the International Agency for Research on Cancer, smoking tobacco is a major cause of cancer in humans. It causes about half of all male cancer deaths and an ever increasing number of cancer deaths in females. The aim of this study was to establish whether cigarette smoking increases sister chromatid exchanges (SCEs) in peripheral blood lymphocytes in two Spanish population groups; light and heavy smokers. The mean number of High-Frequency Cells (HFCs) was determined and, the SCE distribution pattern among the chromosomes was analysed represented by a ratio described below. A local sample of 101 adult smokers (n=48) and non-smokers (n=53), aged from 18 to 49 years, was studied using SCE levels in peripheral lymphocytes. Heavy smoking (≥ 10 cigarettes per day) increased significantly the SCE frequency and the HFC parameters. Neither age nor sex significantly influenced the frequencies in the groups studied.

Screening for agents inhibiting the mutagenicity of extracts and constituents of tobacco products

The aim of this study was to screen for potential agents affecting the mutagenicity of tobacco products. The influence of a number of compounds which have been suggested to be antimutagenic some of which are present in tobacco products, was investigated on the mutagenicity of a cigarette smoke condensate (CSC) and, in some cases, an extract of oral Swedish moist snuff (SNUS), using a screening procedure of the Ames Salmonella/microsome assay (STY). For some of the compounds the V79/hprt mutagenicity assay with benzo[a]pyrene metabolites as mutagens was used to obtain complementary and confirmatory information on mammalian cells. The antimutagens used included two selenium compounds, sodium selenite and ebselen; the flavonoids and polyphenols, ellagic acid, (+)-catechin hydrate, scopoletin, chlorogenic acid and rutin trihydrate; the porphyrin derivatives, bovine hemin, biliverdine dihydrochloride, chlorophyllin and a plant extract containing chlorophyll; the terpenoids, beta-carotene, retinol and a mixture of the two epimers (4R) and (4S) of (1S,2E,6R,7E,11E)-cembra-2,7,11-triene-4,6-diols (CBD); and cyclohexanol and ubiquinone. Screening of antimutagenic activities using the STY involves problems with toxicity. In several cases in this study mutagenicity was decreased below the control level without signs of toxicity in the background growth of bacteria. Since the survival of mutants and slight bacteriostatic effects on the background growth cannot be determined accurately in the STY, a reduction in mutagenicity may simply be due to toxicity. Only in cases where a dose-response curve declines to a level at or above the background and then levels off, can toxicity be excluded. An antimutagenic effect determined using this test system is therefore often not sufficient for classifying a compound as antimutagenic until these findings are confirmed in other test systems and, preferably, the mechanism behind this effect is clarified. The results obtained with the selenium compounds were considered to be inconclusive since the reduction in the mutation rate declined below the background level and might only reflect the toxic effects of these compounds. For ellagic acid an almost complete inhibition of the mutagenicity of CSC and SNUS in STY was indicated. This indication of antimutagenicity was confirmed in V79 cells using two metabolites of the CSC constituent benzo[a]pyrene, i.e., trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene and (+)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE). Chlorogenic acid and (+)--catechin reduced the mutagenicity of CSC and chlorogenic acid also strongly inhibited SNUS mutagenicity. Scopoletin and rutin trihydrate inhibited the mutagenicity of CSC, but showed confounding effects with SNUS.(ABSTRACT TRUNCATED AT 400 WORDS)

Passive smoking and sister-chromatid exchanges in lymphocytes

The object of this study was to determine whether exposure to environmental tobacco smoke is associated with DNA damage reflected by the frequency of sister-chromatid exchange (SCE) in lymphocytes. Within a cross-sectional design, 106 male non-smoking adults, employees of two administrative companies, were divided on the basis of self-reported exposure into high and low passive smoking groups. The high exposed subjects (passive smokers, n = 50) lived with smokers, worked with smokers and were exposed to tobacco smoke for an average of 70 h/week. The low exposed non-smokers (n = 56) were exposed for an average of 5 h/week. Plasma cotinine levels for the passive smokers ranged between 0.4 and 9.0 ng/ml (median 1.4 ng/ml), and for the low exposed group between 0.0 and 1.9 ng/ml (median 0.4 ng/ml) (p less than 0.0001; Mann-Whitney test). No difference was observed between the two groups in the frequency of SCEs in lymphocytes: 4.66 +/- 0.05 for passive smokers and 4.68 +/- 0.04 for low exposed non-smokers (mean +/- SEM) (p = 0.80; t-test). Reclassification of subjects on the basis of plasma cotinine levels did not change the results substantially. These results are in accordance with observations that the increase in cancer risk due to passive smoking is small in comparison with the increase due to active smoking. The SCE test may be too insensitive to be useful for the evaluation of possible cytogenetic effects related to passive smoking.

Constitutive heterochromatin polymorphism and chromosome damage in viral hepatitis

The frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) were scored in relation to constitutive heterochromatin in 100 patients with viral hepatitis B, 100 patients with viral hepatitis A and 100 age- and sex-matched normal controls. 23.4%, 15% and 4% of the cells showed chromosomal aberrations in patients with hepatitis B, hepatitis A and normal controls respectively. Non-random involvement of chromosomal aberrations were also noted in chromosome 1 of patients with hepatitis B and A as compared to normal controls. The frequencies of SCEs (mean +/- S.D.) were found to be 10.40 +/- 2.83 in hepatitis B and 8.70 +/- 2.34 in hepatitis A. These values were significantly higher than the SCE frequency (mean +/- S.D.) of 5.88 +/- 2.25 observed in normal controls (P less than 0.001). The intra-chromosomal distribution of SCEs revealed a relatively increased incidence of SCEs in chromosome 1 of patients with hepatitis B and A as compared to normal controls. Analysis of constitutive heterochromatin polymorphism showed chromosome 1 qh+ to be the most frequent variant in patients with hepatitis B and A as compared to normal controls. The increased involvement of C-band variant 1 qh+ in patients with hepatitis B and A as compared to normal controls may indicate that extra heterochromatin offers additional sites for viral integration.

Sister chromatid exchanges in the lymphocytes of patients with oral leukoplakia

The incidence of sister chromatid exchange (SCE) was investigated in lymphocyte chromosomes of 59 patients with oral leukoplakia and 65 age- and sex-matched nonsmoking controls. The frequency of SCE was found to be 8.61 +/- 1.89 in patients with oral leukoplakia, which was significantly higher than the mean SCE value of 5.58 +/- 1.26 observed in normal controls. The frequency of SCE in patients with oral leukoplakia addicted to the single habit of betel with tobacco chewing, bidi/cigarette smoking, and combined habits of chewing and smoking of tobacco were found to be 7.95 +/- 1.63, 8.17 +/- 1.66, and 9.23 +/- 2.14, respectively. These values were also significantly higher as compared to the SCE values observed in normal controls.

Variation in the human lymphocyte sister-chromatid exchange frequency: results of a long-term longitudinal study

The variation in lymphocyte sister-chromatid exchange (SCE) frequency as a function of time was investigated in nonsmokers and smokers. The smokers were divided into 3 groups depending on their smoking status. The group termed 'smokers' participated in a program to stop smoking but did not reduce or eliminate their use of tobacco; 'smoke enders' successfully completed the smokending program and remained free of tobacco for the duration of the study, while the 'variable' group stopped smoking for a limited time but then resumed smoking. 8 or more blood samples per person were obtained over a period of at least 12 months. The SCE frequencies for each of these groups were compared with each other and with those of two previous longitudinal study groups from our laboratory. The proportion of high-frequency cells (HFCs) was also determined for each sample. The results confirm our previous finding that SCE frequencies and the proportion of HFCs observed in separate samples from the same individual are more likely to be different as the time between samples increases. We also show that smokers have significantly more SCEs and HFCs than do nonsmokers, that SCE frequencies in smokers do not decline for at least 12 months when smoking is stopped, and that among smokers, significant seasonal variation in the SCE frequency occurs. These results provide useful information concerning the effects of smoking upon SCE frequencies, and will be helpful in designing and interpreting the results of long-term human population cytogenetic studies.

Factors that influence formation of sister chromatid exchanges in human blood lymphocytes

Sister chromatid exchange (SCE) reflects an interchange of DNA sequences between helices in a replicating chromosome. This was initially accomplished by Taylor and colleagues (1957) using tritiated thymidine incorporation followed by autoradiography. The development of an elegant technique for differential staining of sister chromatids by incorporating a thymidine analog, 5-bromodeoxyuridine (BrdU) has greatly simplified the detection of SCEs in metaphase chromosomes. In recent years, the analysis of SCE has been considered to be a highly sensitive and additional (i.e., with chromosome aberrations) end point for measuring mutagenic/carcinogenic potential of various environmental agents and is increasingly being used to detect and differentiate among chromosome fragility human diseases that predispose to neoplasia. Attention has been focused to see if the induction of SCEs in lymphocyte cultures can be used as a reliable "biological dosimeter" for genetic risk assessment and to monitor the exposed populations. Several physical or preparatory as well as biological factors that modify the response and formation of SCEs make the monitoring difficult. The purpose of this article is to review and analyze these factors to facilitate an effective development of a standard protocol for SCE testing and for appropriate evaluation of test results. This may also provide clues to understand the yet unknown molecular mechanism(s) and biological significance of SCE formation.

The effect of tobacco smoking on the frequency of sister chromatid exchanges in human lymphocyte chromosomes

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of 24 bidi smokers, 18 cigarette smokers, and 20 normal nonsmoking controls. Bidi and cigarette smokers had a mean SCE per cell of 10.12 +/- 2.41 and 8.15 +/- 1.62, respectively, which were significantly higher than the mean value of 5.48 +/- 1.29 found in controls. Higher frequencies of SCE were also observed in individuals who smoked more than ten bidis or cigarettes per day, compared with people who smoked less than ten bidis or cigarettes per day, respectively. Individuals who smoked bidis or cigarettes for more than 10 years also showed an increased frequency of SCE as compared with those who smoked bidis or cigarettes for less than 10 years.

Normal sister chromatid exchange in lymphocytes from patients with multiple epidermal cancer?

Exposure to toxins in the environment and due to personal habits, e.g., tobacco smoking, may increase the rate of spontaneous sister chromatid exchange (SCE). The SCE in lymphocytes from a group of 31 patients with multiple epidermal cancer, who in the past had been exposed to various skin carcinogens, as a whole exceeded that of a control group--matched by sex, age, and smoking habits--but the difference was not statistically significant (p = 0.08). The individual SCE in these patients was also statistically independent of the nature of the carcinogenic exposure. We were unable to detect correlations between the SCE and UVC-radiation induced DNA synthesis, UVC-radiation tolerance, or rate of X-ray damage repair. This suggests that the molecular mechanisms involved in SCE induction and in repair of radiation damage are basically independent.

Very low sister-chromatid exchange rate in Seventh-Day Adventists

42 Seventh-Day Adventists (SDAs) and 42 controls matched for sex, age and occupation had their sister-chromatid exchange (SCE) examined in peripheral blood lymphocytes. This was done to examine if the SCE frequency was lower in this group of people, who are known to have a decreased cancer risk compared to the general population. The average SCE/cell in 30 cells from each person was 5.54 +/- 0.07 (mean +/- standard error of the mean) for the SDAs and 8.00 +/- 0.15 for the controls, the difference being statistically significant (p less than 0.00001). No difference in SCE frequency was found between SDAs eating only an ovo-lacto-vegetarian diet and those eating some fish or meat. The mitotic index (MI) was significantly higher and the replication index (RI) was significantly lower in SDAs than in controls. No correlation was found between gamma (a statistical transformation of SCEs/cell) and MI or RI within the groups of SDAs or controls. In the pooled data there was a negative correlation of gamma and MI and a positive correlation of gamma and RI. Of the interpersonal variation in gamma 8% and 14% could be explained by MI and RI. The finding of a lower SCE frequency in a group of SDAs who have a low risk of cancer might indirectly indicate a relation between SCE and cancer and encourages further studies of SCE and diet.

Analysis of sister-chromatid exchanges (SCEs) in familial and sporadic multiple sclerosis

The levels of sister-chromatid exchanges (SCEs) were calculated in 17 multiple sclerosis (MS) patients (14 familial and 3 sporadic cases) and 16 healthy controls matched for sex and age. The SCEs were significantly increased for MS patients (p = 0.0002), while there was no statistically significant difference between men and women and between younger and older subjects in both groups. Such factors as familial occurrence and severity of MS, smoking habits, and distribution of lymphocyte subpopulations were discussed. Although there was a significant difference between the MS patients taking medication and the patients taking none (p = 0.038), the latter were still significantly different from the controls (p = 0.035), supporting the fact that the disease itself increases SCEs. Our study, done with 2 doses of BrdU, also shows that the increased SCEs in MS patients are not due to a hypersensitivity to this substance known to be an inducer of SCEs. Thus we suggest that the increased SCEs found are probably disease-related.

Sister chromatid exchange in patients treated with methotrexate for psoriasis

Sister chromatid exchange (SCE), which is considered a sensitive method in evaluation of mutagenicity and may be an indicator of carcinogenicity, was determined in lymphocytes from 8 patients with severe psoriasis who underwent treatment with oral methotrexate (MTX). During the treatment period (median 118 days, range 50-298 days) a significant increase in SCE compared to the pretreatment value was found in 1 patient only. It is concluded that no long-term damage as measured by SCE occurs in lymphocytes from psoriasis patients treated with MTX.

Distribution of SCEs in lymphocytes in persons with normal, slightly increased, and heavily increased SCEs

The distribution of SCEs in lymphocytes was examined for 165 healthy persons (58 non-smokers and 107 smokers with cigarette consumption ranging from 1 to greater than 20 per day), and for 1 patient treated with melphalan, a cytostatic drug. The data from the healthy persons did not follow a Poisson distribution. A mixed Poisson that allowed different lambda values for the 30 cells scored from each person and postulated a gamma distribution for the lambda s within the 30 cells fitted all the data examined including those from the melphalan-treated patient. In the latter case the 7 samples taken at various times after the treatment could all be represented satisfactorily with a common parameter, c, in the gamma distribution for the lambda s, even though the mean SCEs/cell varied from 9.8 to 36.8. Because the c parameter determines the spread of lambda values within the 30 cells, this suggested that the effect of the cytostatic drug was to increase all the lambda s by a constant amount. The sum of the SCEs taken over all 30 cells in a sample is a convenient summary statistic, and the transformation y = square root s + square root s + 1 behaves as a normal variate with a constant variance within a group.

The SCE test as a tool for cytogenetic monitoring of human exposure to occupational and environmental mutagens

The sister chromatid exchange (SCE) test system using human peripheral lymphocytes is proposed as a valuable tool for the cytogenetic monitoring of exposure to potential chemical mutagens in the occupational environment. We examined the SCE frequencies in organic solvent-exposed workers and reviewed the effects of occupational and environmental chemicals on SCE frequencies. The results obtained in these exposed populations are rather contradictory, which may be related to confounding factors, such as personal life style (smoking, drinking, and drugs) of the examinees, tissue culture conditions and the number of subjects examined. We discussed some practical problems for exposure estimation and sample size determination and are led to the following conclusions. 1) The possible combined effects of potential mutagens and cigarette smoking should be taken into consideration when using the SCE test system. 2) Cell cycle kinetic analysis by differential chromatid staining would provide valuable information as a biological indicator for the monitoring of the workers exposed to xenobiotics. 3) By appropriately setting the number of examinees, monitoring would become more efficient in detecting an increased SCE frequency in the exposed populations. Further studies are also required to enhance the sensitivity of the SCE test system for monitoring purposes.