Elevated sister chromatid exchange frequencies in the lymphocytes of esophageal cancer patients

Genomic instability in chronic obstructive pulmonary disease and lung cancer: A systematic review and meta-analysis of studies using the micronucleus assay

Respiratory tissues are highly susceptible to diseases due to the constant exposure to physical and chemical airborne pollutants. Chronic obstructive pulmonary disease (COPD) and lung cancer are among the most common causes of serious illness and death worldwide. The inflammatory environment associated with these respiratory diseases has long been accepted as the major player in the development of airway abnormalities. The presence and relevance of DNA damage and genomic instability makes the micronucleus assay a suitable candidate to quantitatively estimate these early pathogenetic events. A systematic review and meta-analysis were planned to determine underlying common mechanisms that can explain the relationships between COPD and lung cancer. A total of 17 studies from Jan 1999 to Dec 2019 comparing micronucleus frequency in patients affected by respiratory diseases vs healthy controls were analysed. Our results confirmed the presence of significant association between MN frequency and the diseases investigated, and suggested a circle of events linking inflammation induced oxidative stress to the risk of disease through genomic instability and hypoxia. Therefore, using non-invasive, robust and cost effective genomic instability assays such as the micronucleus assay, would allow us to capture unique phenotypic and biological changes that would allow the identification of subjects at high risk of developing lung diseases and improve early detection strategies.

Can consumption of raw vegetables decrease the count of sister chromatid exchange? Results from a cross-sectional study in Krakow, Poland

Background

Sister chromatid exchange (SCE) is a widely used sensitive cytogenetic biomarker of exposure to genotoxic and cancerogenic agents. Results of human monitoring studies and cytogenetic damage have revealed that biological effects of genotoxic exposures are influenced by confounding factors related to life-style. Vegetable and fruit consumption may play a role, but available results are not consistent. The purpose of the study was to investigate the effect of consumption of raw and cooked vegetables and fruits on SCE frequency.

Methods

A total of 62 participants included colorectal cancer (CRC) patients, hospital-based controls and healthy laboratory workers. SCE frequency was assessed in blood lymphocytes. Frequency of vegetable and fruit consumption was gathered by structured semi-quantitative food frequency questionnaire.

Results

SCE frequency was lowest among hospital-based controls (4.4 ± 1.1), a bit higher in CRC patients (4.5 ± 1.0) and highest among laboratory workers (7.4 ± 1.2) (p < 0.05). Multivariable linear regression showed a significant inverse effect (b = −0.20) of raw vegetable consumption, but not so for intake of cooked vegetables and fruits.

Conclusions

The results of the study have shown the beneficial effect of consumption of raw vegetables on disrupted replication of DNA measured by SCE frequency, implying protection against genotoxic agents. Further effort is required to verify the role of cooked vegetables and fruits.

Cytokinesis-blocked micronucleus assay and cancer risk assessment

Cancer risk assessment is a multidisciplinary process that goes beyond the scope of classical epidemiology to include the biological evaluation of individual differences to carcinogenic exposures. The inclusion of genetic biomarkers such as mutagen sensitivity or cytokinesis-blocked micronucleus (CBMN) assay end points into risk assessment models allows for a more comprehensive determination of cancer risk that includes known demographic (age and gender), lifestyle exposures (smoking and alcohol) and occupational or environmental exposures. The CBMN assay generates multiple correlated end points that, after applying data reduction methods, could be combined into a summary measure that incorporates information from each individual variable into a single (or possible multiple, uncorrelated) measure of risk. In this article, we highlight the use of the CBMN assay in radiosensitivity assessment. In addition, we demonstrate the potential use of the combined summary measures in cancer risk assessment as a result of chronic exposure to tobacco carcinogens. The simplicity, rapidity and sensitivity of the CBMN assay not only make it a valuable tool for screening but also the multiple end points simultaneously generated lead to a better understanding of the underlying mechanisms involved in the carcinogenic process that could in turn substantially improve risk predictions.

Spontaneous and gamma-ray-induced sister chromatid exchanges in patients with carcinoma of cervix uteri

The aim was to investigate whether there are differences in the spontaneous and gamma-ray-induced genomic instability in peripheral blood lymphocytes between untreated cervical cancer patients and healthy women using the sister chromatid exchange (SCE) assay as an indicator of chromosomal instability. Lymphocyte cultures from whole venous blood of 10 patients with cervical neoplasia and 10 healthy female volunteers were cultivated in vitro and irradiated using a 60Co-gamma source. Slides were prepared using the standard air-drying procedure and stained by the fluorescence-plus Giemsa (FPG) technique. The number of SCE and the number of chromosomes were assessed in second-division metaphases. A radiation dose-dependent increase of SCE/cell and SCE/chromosome values were found in healthy women as well as in patients, while statistical analysis has shown significantly higher SCE frequencies in healthy women as compared with patients. Cellular kinetics expressed as replication indices (RI) calculated from the frequency of cells in first cell division (M1), second cell division (M2) and third cell division (M3) were also significantly different, while observed RI were higher for patients than for control individuals. The results suggest that patients with carcinoma of the cervix uteri have chromosomal stability changes reflected in statistically different levels of spontaneous and induced SCE in comparison with healthy individuals. Despite the unknown mechanisms of SCE formation, it is felt that the changed SCE frequency, especially after mutagen treatment, may be used as a marker of increased cancer risk.

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.

Sister chromatid exchange frequencies in carcinoma of the human oral cavity: effect of treatment

Spontaneous and mitomycin-C-induced sister chromatid exchange frequencies were studied in the lymphocytes of 25 oral cancer patients. For these patients, the mean spontaneous SCE value was 8.31 (+/- SD), which was significantly higher than the value of 6.60 (+/- SD) obtained for the controls (p < 0.001). But there was no significant difference between the Mitomycin C induced mean SCE values of oral cancer patients and controls. Seven of these 25 oral cancer patients were selected for second sampling after surgical removal of the tumor. Six of these seven patients showed a decrease in mean SCE/cell value following surgery, which was almost equal to the SCE values obtained for the controls. This indicates that the increased spontaneous SCE rates in oral cancer patients might be due to the metabolic stress imposed by the tumor on the host body or by some clastogenic product of the malignant cells. Surgical removal of the tumour might have resulted in normalization of the lymphocytic SCE rates in postoperatively studied patients.

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.

Effects of CCNU therapy on human chromosomes

Peripheral blood lymphocytes of 9 patients under CCNU therapy were examined for frequency of sister-chromatid exchanges (SCEs) and chromosomal aberrations (CAs). 7 out of 9 patients were treated with only CCNU, whereas the remaining 2 were treated with other chemotherapeutic agents in combination with CCNU. Compared to normal individuals, a significantly increased frequency of SCE was observed in the patients before starting anticancer therapy (P less than 0.001). Increased incidences of structural changes in chromosomes were observed in cells from all the treated patients. The most frequent aberrations were of chromatid type. After administration of a single dose of CCNU, an increase in SCE frequencies was observed which remained elevated even after 6 weeks. It was concluded that increases in SCEs and CAs in lymphocytes were caused by CCNU treatment. Further studies are needed to elucidate whether any CAs observed in the present study could participate in the induction of second neoplasm.