Sister chromatid exchanges in patients with precancerous and cancerous lesions of cervix uteri

Sister chromatid exchanges in smokers and smokers with alcohol habit

Aim:

Sister chromatid exchange (SCE) test is a sensitive, biomarker of genotoxic substances. The present study was conducted to observe the frequency of SCEs in peripheral blood lymphocytes of 30 males with and without the habit of cigarette smoking and alcohol consumption.

Materials and Methods:

Subjects for this study were males aged between 25-50 years and were selected from the students, employees and the patients attending the outpatient department of Ragas dental college and Hospital, Chennai.

Results:

Controls, smokers, and smokers with alcohol habit were divided into two age groups as ≤30 years and ≥30 years. In controls the mean frequency of SCEs/cell in ≤30 years and ≥30 year's age group was 5.80 and 6.05, respectively. In Smokers SCEs/cell in ≤30 years and ≥30 year's age group was 7.7 and 8.8, respectively. In Smokers with alcohol habit SCEs/cell in ≤30 years and ≥30 years age group was 10.1 and 12.8, respectively.

Conclusions:

In this study, the duration of the smoking habit has shown a positive correlation with the mean SCE frequency. Whereas, frequency of the habit did not show any influence on the SCE levels. In smokers with alcohol habit, both the duration and frequency of their smoking habit has shown a significant effect on the SCE levels suggesting a synergistic effect of alcohol and smoking leading to excessive DNA damage.

Lymphocyte telomere dynamics and telomerase activity in inflammatory bowel disease: effect of drugs and smoking

BACKGROUND

The chromosome instability observed in peripheral blood lymphocytes in ulcerative colitis could be a biomarker of cancer susceptibility.

AIM

To determine whether accelerated telomere shortening could explain chromosome instability and assess the effect of drugs and smoking on telomere dynamics in these cells.

METHODS

Peripheral blood lymphocytes were isolated from ulcerative colitis, Crohn's disease and non-inflammatory bowel disease control patients. Telomere lengths were measured by quantitative real-time polymerase chain reaction. After activation and cell separation, telomerase activity and human telomerase reverse transcriptase messenger ribonucleic acid were measured by telomerase repeat amplification protocol enzyme-linked immunosorbent serological assay and quantitative real-time polymerase chain reaction, respectively.

RESULTS

Age-related telomere loss in peripheral blood lymphocytes was similar in ulcerative colitis, Crohn's disease and control patients. Telomerase activity decreased with age in all groups and correlated positively with telomere length (r = 0.489, P = 0.006). Among Crohn's disease patients, azathioprine was associated with decreased telomerase activity (0.66 vs. 1.54, P = 0.026, P < 0.05) and smoking was associated with decreased human telomerase reverse transcriptase mRNA expression (10.5 vs. 33.3, P = 0.036, P < 0.05).

CONCLUSIONS

Telomere shortening is not accelerated and therefore cannot be the cause of the chromosome instability observed in ulcerative colitis peripheral blood lymphocytes. Azathioprine and cigarette smoking modify telomerase expression in these cells.

Sister chromatid exchanges in peripheral lymphocytes from women with carcinoma of the uterine cervix

Sister chromatid exchanges (SCE) are reciprocal exchanges between sister chromatids. It has been reported that in patients with cervical cancer, the frequency of SCE in peripheral lymphocytes is significantly higher than that in normal individuals; however, other studies have shown no significant difference. The aim of this unmatched case-control study was to compare the mean number of SCE per metaphase in lymphocytes from women with and without carcinoma of the cervix uteri. The SCE specimens were prepared by the fluorescence plus giemsa technique in peripheral lymphocytes from 28 women with carcinoma of cervix uteri and 28 controls. The mean number of SCE per metaphase in women with carcinoma of cervix uteri (7.80 +/- 1.05) was higher than the control group (6.98 +/- 1.13) (P < 0.05; t-test). This study had a statistical power of 0.80 and an alpha value of 0.05. This finding suggests that an increased number of SCE in peripheral lymphocytes is associated with cervical cancer. We consider that the lack of reported association of SCE and cervical cancer might be attributed to the none determination of the statistical power and sample size.

High frequencies of telomeric associations, chromosome aberrations, and sister chromatid exchanges in ulcerative colitis

OBJECTIVE

Chromosome instability provides a predisposing background to malignancy, contributing to the crucial genetic changes in multistep carcinogenesis. The aim of this work was to analyze chromosome instability in patients with ulcerative colitis (UC) to achieve a better understanding of the increased risk for colorectal cancer.

METHODS

Peripheral blood lymphocyte cultures from 20 untreated UC patients and 24 controls were used to study chromosome instability by assessing telomeric associations (TAS), chromosome aberrations (CA), and sister chromatid exchanges (SCE).

RESULTS

Mean frequencies of TAS and CA were significantly increased in UC patients compared to controls (p < 0.001). Chromosomes 10, 11, 21, 16, and 19 were the most frequently involved in TAS. A total of 104 CA clustered in 66 breakpoints could be exactly localized. Seven nonrandom bands significantly affected in UC patients were found (p < 0.004), showing a significant correlation with the location of cancer breakpoints (p < 0.003), particularly with colorectal carcinoma rearrangements. SCE analysis showed higher levels in patients compared to controls (p < 0.006), but no differences were observed in cell cycle kinetics.

CONCLUSIONS

Our results demonstrate the presence of an unstable genome in UC patients that could be related to the cancer development observed in this disease.

Chromosome aberrations and sister chromatid exchange studies in patients with prostate cancer: possible evidence of chromosome instability

Cytogenetic studies have been carried out using the G-banding technique in peripheral blood lymphocytes of 24 patients with prostate cancer. Of these, eight belong to stage B, six to stage C/e, three to C/sv, two to Do, and the remaining five to DI stage of carcinoma. Simultaneously, sister chromatid exchanges (SCEs) were also analyzed in the peripheral blood lymphocytes of these patients, along with those of 40 age-matched control subjects. The frequency of aberrant metaphases is significantly higher in patients with prostate cancer (7.32%) than in age-matched controls (2.92%). A large number of chromosome aberrations in lymphocytes of these patients, which are generally constitutional in nature, have also been detected. In stage-B patients, the frequency of cytogenetically abnormal cells is comparatively low with regard to the number of cells scanned, and these abnormalities are generally confined only to single chromosome (except in one metaphase in patient 1, who was diagnosed with bladder carcinoma in addition to cancer of the prostate). Sister chromatid exchanges (SCEs) were also analyzed in the patients and age-matched control subjects. The mean SCE frequencies were 9.24 +/- 0.62 (n = 1356) per metaphase and 0.203 per chromosome in patients, whereas in control subjects the frequencies were 5.94 +/- 0.25 (n = 4000) per metaphase and 0.129 per chromosome. The SCE frequency in cancer patients was statistically significant (p < 0.001). Our results indicate that the patients with prostate cancer show a degree of chromosomal instability that might be related to a predisposition to neoplasia.

Spontaneous genomic fragility and cell cycle progression in lymphocytes of patients with cervical carcinoma

Thirty patients with invasive carcinoma of the cervix, along with 15 age-matched healthy females as controls, were studied to examine the frequency of spontaneous SCEs, chromosomal aberrations (CAs), and cell cycle progression in lymphocytes. The frequency of SCEs and TCAs was statistically significant in the patients over the control group. The correlation of SCEs and TCAs with the stage of cancer, age, and number of pregnancies was also made. The cell cycle of lymphocytes showed its prolongation in the patients, as is evident from the higher proportion of cells at M1 (metaphase of first cell division after 72 hours).

Choromosome instabililty and sister chromatid exchange (SCE) studies in patients with carcinoma of cervix uteri

Cytogenetic studies have been carried out using the G-banding technique in peripheral blood lymphocytes of 14 patients with carcinoma of the cervix uteri. Simultaneously, sister chromatid exchange (SCE) was also analyzed in the peripheral blood lymphocytes of these patients, along with those of 20 age-matched control subjects. The frequency of aberrant metaphases is significantly higher in patients with carcinoma of the cervix uteri (7.85%) than in the age-matched controls (3.35%). A large number of chromosome aberrations in lymphocytes of these patients have also been detected. Sister chromatid exchange (SCE) was also analyzed in lymphocytes of 14 patients with carcinoma of the cervix uteri and 20 age-matched control subjects. The mean SCE frequencies were 9.44 +/- 0.34 (n = 637) and 6.09 +/- 0.24 (n = 900) per metaphase in patients and controls, respectively. The increase of SCE frequency in cancer patients was statistically significant (p < 0.001), but not seen in controls. Our results suggest that patients with carcinoma of the cervix uteri show a degree of chromosomal instability that might be related to a predisposition to neoplasia.

Nuclear lesions during rat hepatocarcinogenesis. I. Measuring the sister-chromatid exchanges during initiation, promotion and progression of rat hepatocarcinogenesis induced with diethylnitrosamine

Cytogenetic endpoints such as sister-chromatid exchanges (SCEs), chromosomal aberrations and micronuclei (MNs) have been widely used as indicators of genetic damage. However, no systematic attempts have been made to correlate the levels of these cytogenetic endpoints with the different steps of carcinogenesis. In the present report, the induction, accumulation and persistence of SCEs and high frequency cells (HFCs) were measured in liver cells during the initiation, promotion and progression steps of rat hepatocarcinogenesis induced by diethylnitrosamine (DEN). The results indicate that lesions leading to SCEs accumulate during initiation only. When DEN administration is longer than the duration of this first step, SCE values stabilize. After stopping the carcinogenic treatment, the SCE levels decrease to control values whether or not promotion and progression occur.

Genetic instability assessed by sister chromatid exchange analysis in the Dunning R-3327 rat prostatic adenocarcinoma model and its relationship to metastatic potential

The original Dunning R-3327 tumor, described in 1961, has given rise to distinct sublines of different metastatic potentials. The different phenotypes cannot be explained by differences in chromosomal number, DNA content, or nuclear pleomorphism. Sister chromatid exchange is an interchange between two strands of DNA indicative of DNA damage. The frequency of sister chromatid exchanges is a well-accepted measure of genetic instability. To determine whether an assay of genetic instability could distinguish sublines capable of generating cells of the metastatic phenotype, cells from three sublines of low (< 10%) metastatic potential and three sublines of high (> 90%) metastatic potential were cultured in 10 microM 5-bromodeoxyuridine to label DNA. Chromosome preparations were made and sister chromatids were differentiated with Hoechst 33258 dye and Giemsa stain. Sixty metaphase spreads from each subline were scored for SCE and chromosome number. The low metastatic sublines G, AT-1, and AT-2 had 0.32 +/- standard deviation 0.10, 0.38 +/- 0.12, and 0.14 +/- 0.05 sister chromatid exchanges per chromosome, respectively. The high metastatic sublines AT-3, MAT-Lu, and MAT-LyLu had 0.55 +/- 0.17, 0.32 +/- 0.1, and 0.33 +/- 0.2 sister chromatid exchanges per chromosome, respectively. Subline differences in metastatic potentials cannot be explained by incidences of sister chromatid exchanges.

Sister chromatid exchange (SCE) studies in breast cancer patients: a follow-up study

Sister chromatid exchanges (SCEs) were studied in 20 patients with breast cancer (stage II) before surgery, one month after surgery, and after three years as a follow-up study. Data from 50 age-matched, normal healthy females, preferably from the affected families, served as controls. In each patient, 50 well-spread metaphases were scored for SCEs. The mean values of SCEs per metaphase were 5.80, 4.69, and 5.98 in breast cancer patients before surgery, one month after surgery, and after a gap of three years as a follow-up, respectively. The one-way analysis of variance was applied and it was found that there was a highly significant difference in the frequency of sister chromatid exchanges in these patients before surgery, one month after surgical removal of cancerous tissue, and after three years as a follow-up study. The elevated level of SCEs three years after surgical removal of cancerous tissue predict the chances of development of another type of cancer.

Sister chromatid exchange analysis in acute leukemia patients

This study was made to show the effects of acute leukemia (AL) and cytostatic drug therapy on chromosomes by sister chromatid exchange (SCE) analysis. Metaphase preparations from peripheral blood lymphocytes (PBL) of 15 patients [13 with acute nonlymphocytic leukemia (ANLL) and one with acute lymphocytic leukemia (ALL), and one with Hodgkin's disease (HD)] were harvested before and after treatment. Mean SCE frequency in the cells was 12.07 +/- 0.15 before therapy and was 14.04 +/- 0.32 after therapy as compared with 7.87 +/- 0.60 in controls. SCE values of patients with AL were significantly higher than those of controls, and this was more conspicuous in the cells that had undergone anticancer treatment.

Study of numerical aberrations of chromosome 1 by fluorescent in situ hybridization and DNA content by densitometric analysis on (pre)-malignant cervical lesions

In an attempt to determine whether the fluorescent in situ hybridization (FISH) can be used as a rapid approach for the identification of aneuploidy in premalignant cervical smears, a centromeric probe for chromosome 1 was used. The results from the FISH experiments were compared with measurements of the overall DNA content obtained by means of an image analysis system. With progression to neoplasia, a decrease of the frequency of cells with two spots was observed, due to an increasing polysomy of chromosome 1. As far as the DNA content was concerned, an increasing DNA index and 5C-exceeding ratio (fraction of cells with a DNA content higher than 5C) was observed. Classification of the FISH results by a linear discriminant analysis revealed that 67.6% of the cases were classified in agreement with the CIN classification. These data suggest that chromosome 1 may be considered as a marker chromosome for pre-malignant cervical lesions and that the DNA content measurements are complementary to the FISH results.

Detection of premalignant stages in cervical smears with a biotinylated probe for chromosome 1

Fluorescence in situ hybridization with (peri-)centromeric probes is an easy method to detect numerical aberrations in nonmitotic and mitotic cells. In this study, cervical smears of premalignant and malignant stages (26 controls, 15 CIN I, 12 CIN II, and 15 CIN III cervical smears) were analyzed for the presence of numerical aberrations of chromosome 1 with a centromeric DNA probe (1q12). With more severe stages a decrease of disomy was observed, merely due to a gain of extra copies of chromosome 1; in some cases, however, monosomy was detected. The frequencies of disomy for chromosome 1 ranged from 65.3% to 95.0% in the controls, from 71.3% to 94.3% in CIN I, from 59.2% to 91.5% in CIN II, and from 23% to 96.2% in CIN III. Polysomy ranged from 0% to 5.7% in the controls, from 0% to 14.4% in CIN I, from 0.9% to 30.8% in CIN II, and from 0.8% to 69.6% in CIN III. Monosomy ranged from 2.6% to 34.1% in the controls, from 0% to 17.5% in CIN I, from 3.6% to 27.5% in CIN II, and from 0.9% to 31.4% in CIN III. The results show that screening for aneuploidy of chromosome 1 allows a good discrimination between control samples and dysplasia. These data suggest that chromosome 1 may be a marker chromosome. They are in accordance with previous cytodensitometric analyses, where already in the preneoplastic stages an increased DNA content (polyploidization with subsequent aneuploidization) is observed.

Cytogenetic damage by melphalan and hyperthermia in patients with an initial epileptic attack

Sister-chromatid exchanges (SCEs) and cell kinetics in cultured lymphocytes of patients with an initial epileptic attack, and prior to any anticonvulsant treatment, were studied. Spontaneous melphalan (MEL) and MEL-hyperthermia (MEL-HYP) induced SCE frequencies have been studied in 18 adults with an initial epileptic seizure. Fifteen age and sex matched healthy subjects were used as the control group. The incidence of spontaneous SCEs in lymphocytes from epileptics was not significantly greater than in those from the control subjects. However, when exposed to MEL in vitro, cells from both groups showed an increase in SCE frequency. When exposed to MEL and HYP (41 degrees C for 3 h) in vitro, cells from both groups showed a further increase in SCE frequency with yields from epileptics higher (P less than 0.05) than from controls. HYP in combination with MEL enhanced synergistically SCEs and cell division delays in both groups with synergistic effects in cells from epileptics (P less than 0.01 and P less than 0.01 respectively) higher than from controls (P less than 0.05 and P less than 0.05 respectively.

Sister chromatid exchanges in patients with carcinoma in situ of cervix uteri

Sister chromatid exchange (SCE) was analyzed in lymphocytes of 21 patients with carcinoma in situ of cervix uteri and 19 control subjects. The mean SCE frequencies were 8.92 +/- 0.31 (n = 417) and 6.94 +/- 0.23, (n = 375) per metaphase in patients and controls, respectively. The increase of SCE levels in cancer patients was highly significant in respect to controls (p less than 0.001). Together with data of other authors in patients with precancerous and cancerous lesions of the cervix, our results suggest that there is no correlation between SCE rate and severity of cancerous lesions.

Cytogenetic surveillance of tobacco-areca nut (mava) chewers, including patients with oral cancers and premalignant conditions

Three cytogenetic endpoints were studied in non-chewing healthy controls and 3 groups of tobacco-areca nut chewers, viz. normal chewers, chewers with oral submucous fibrosis and chewers with oral cancer. Frequencies of sister-chromatid exchanges and chromosome aberrations in peripheral blood lymphocytes and of micronucleated cells in exfoliated buccal mucosa were evaluated. All the parameters showed statistically significant elevations in all 3 groups of chewers compared to the controls. The data indicate possible application of the parameters as sensitive endpoints for monitoring tobacco-areca nut chewers, the group of individuals at higher risk of developing oral cancer, the commonest cancer among Indian males.

Increased spontaneous and mitomycin C-induced sister chromatid exchanges in patients with cancer of the cervix uteri, with special reference to stage of cancer

The frequencies of spontaneous and mitomycin C (MMC)-induced sister chromatid exchange (SCE) were examined in 35 patients with cancer of the cervix uteri (stage 0, eight cases; stage I, nine cases; stage II, nine cases, and stage III, nine cases) before they had undergone cancer treatment, as well as in seven patients with uterine myoma and 18 healthy women as controls. The frequency of SCE was analyzed in reference to the stage of cancer in the cancer group and in reference to chromosome group in the cancer and normal groups. The frequencies of spontaneous and MMC-induced SCE in the cancer group were 10.0 +/- 1.8 and 20.7 +/- 2.6, respectively, and both were significantly higher than in the myoma (8.1 +/- 0.8 and 17.6 +/- 1.8) and normal (7.6 +/- 0.8 and 17.6 +/- 2.3) groups. Furthermore, the frequency of SCE in the cancer group increased with cancer stage. All chromosome groups contributed equally to the increase in SCE in the cancer group. These results indicate that an increase in the frequency of SCE in patients with cervical cancer is related to the presence of cancer, but is not related to a predisposition to cancer.

Increased numbers of spontaneous micronuclei in blood lymphocytes and cultures fibroblasts of individuals with familial cutaneous malignant melanoma

In vitro detection of micronuclei was used to determine spontaneous chromosomal instability in cultured fibroblasts of 28 healthy normal controls, 28 individuals with nonfamilial cutaneous malignant melanoma (CMM) and 14 people with familial occurrence of CMM. Lymphocytes from 40 healthy controls, 40 CMM patients and 6 individuals with familial CMM were also compared for spontaneous expression of micronuclei in vitro. In the familial cases micronucleus frequency was found to be higher, both in cultured fibroblasts (P less than 0.005) and in lymphocytes (P less than 0.001) as compared to normal controls. There was no significant difference between nonfamilial cases and normal controls. We conclude that chromosomal instability may contribute to a genetic risk for development of cutaneous malignant melanoma.

Effect of hyperthermia on the frequency of sister-chromatid exchanges in patients with cancer of cervix uteri

The frequencies of sister-chromatid exchanges (SCE) were studied in patients with cancer of the cervix uteri and normal controls at 37 degrees C and 40 degrees C. At 37 degrees C the mean frequency of SCE was found to be 8.26 +/- 1.91 in untreated patients with cervical cancer and 7.91 +/- 1.68 in cancer patients treated with radiotherapy; these values were significantly higher than the control value of 5.34 +/- 1.28 exchanges. Increase of the growth temperature to 40 degrees C elevated the SCE frequency to 11.95 +/- 2.12 in patients without radiotherapy treatment, 13.37 +/- 2.17 in patients with radiotherapy treatment and 7.82 +/- 1.84 in normal controls. These data indicate that there is a differential induction of SCEs by hyperthermia in the lymphocytes of control women and patients with cancer of the cervix uteri.

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.

Common fragile sites: their prevalence in subjects with constitutional and acquired chromosomal instability

Chromosomal fragile sites that are inducible by methotrexate and aphidicolin are frequent in the human population. To assess the frequency and distribution of these common fragile sites, we performed a cytogenetic survey on lymphocytes from subjects known to be particularly prone to breakage because of constitutional chromosomal instability, the possession of a rare fragile site, or Fanconi anemia. Furthermore, a group of cancer patients was included in this study in view of possible acquired chromosomal instability. Lymphocyte chromosomes from several healthy donors were analyzed under identical conditions. We found that methotrexate- and aphidicolin-induced fragile sites are widespread in the general population, showing a similar breakpoint distribution. Ten fragile sites (3p14, 16q23, 2q32, 6q25, 4p16, 4q31, 14q24, 1p31, 20p12, 7q21) were observed in at least 40% of the individuals among the different groups. Our data point out a significantly increased breakage induced by aphidicolin in lymphocytes from cancer patients and, to a lesser extent, from rare fragile sites carriers. These results suggest that common fragile sites are enhanced in some constitutional and acquired conditions.