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

Lymphocyte micronuclei frequencies in skin, haematological, prostate, colorectal and esophageal cancer cases: A systematic review and meta-analysis

Micronucleus (MN) assay has been widely used as a biomarker of DNA damage, chromosomal instability, cancer risk and accelerated aging in many epidemiological studies. In this narrative review and meta-analysis we assessed the association between lymphocyte micronuclei (MNi) and cancers of the skin, blood, digestive tract, and prostate. The review identified nineteen studies with 717 disease subjects and 782 controls. Significant increases in MRi for MNi were observed in the following groups: subjects with blood cancer (MRi = 3.98; 95 % CI: 1.98-7.99; p = 0.000) and colorectal cancer (excluding IBD) (MRi = 2.69; 95 % CI: 1.82-3.98, p < 0.000). The results of this review suggest that lymphocyte MNi are a biomarker of DNA damage and chromosomal instability in people with haematological or colorectal cancers. However, the MRi for lymphocyte MNi in subjects with cancers of skin, prostate, esophagus was not significantly increased. More case-control and prospective studies are warranted to further verify the observed trends and to better understand the role of lymphocyte MNi as a biomarker of cancer risk in blood, skin, digestive tract and prostate.

Micronuclei and Their Association with Infertility, Pregnancy Complications, Developmental Defects, Anaemias, Inflammation, Diabetes, Chronic Kidney Disease, Obesity, Cardiovascular Disease, Neurodegenerative Diseases and Cancer

Micronuclei (MN) are a strong cytogenetic indicator of a catastrophic change in the genetic structure and stability of a cell because they originate from either chromosome breaks or whole chromosomes that have been lost from the main nucleus during cell division. The resulting genetic abnormalities can to lead to cellular malfunction, altered gene expression and impaired regenerative capacity. Furthermore, MN are increased as a consequence of genetic defects in DNA repair, deficiency in micronutrients required for DNA replication and repair and exposure to genotoxic chemicals and ultraviolet or ionising radiation. For all of these reasons, the measurement of MN has become one of the best-established methods to measure DNA damage in humans at the cytogenetic level. This chapter is a narrative review of the current evidence for the association of increased MN frequency with developmental and degenerative diseases. In addition, important knowledge gaps are identified, and recommendations for future studies required to consolidate the evidence are provided. The great majority of published studies show a significant association of increased MN in lymphocytes and/or buccal cells with infertility, pregnancy complications, developmental defects, anaemias, inflammation, diabetes, cardiovascular disease, kidney disease, neurodegenerative diseases and cancer. However, the strongest evidence is from prospective studies showing that MN frequency in lymphocytes predicts cancer risk and cardiovascular disease mortality.

Investigation of genotoxicity in acromegaly from peripheral blood lymphocyte cultures using a micronucleus assay

CONTEXT

Although patients with acromegaly may have an increased risk of developing several types of cancers, the degree of risk for malignancy in these patients is unresolved.

OBJECTIVE

The present study aimed to investigate the potential genotoxic effects of acromegaly on the cell cycle in peripheral blood lymphocyte cultures.

DESIGN

This was a single center, crossover, case-control study conducted on the acromegalic patients in Turkey.

SETTING

The study was conducted in the outpatient clinic of a university hospital.

PATIENTS

Seventy-one consecutively screened acromegalic patients and 56 controls participated in the study.

INTERVENTION

Patients were included, regardless of the disease activity status and their treatment duration before the study.

MAIN OUTCOME MEASURES

The primary end point was the frequency of micronucleus (MN) in the peripheral blood lymphocyte cultures, and the secondary end point was its clinical correlations.

RESULTS

The MN level was 3.82 ± 1.49 in the control group and 18.00 ± 6.13 in the acromegalic group (P < .01), whereas the nuclear division index (NDI) was 1.79 ± 0.12 in the control group and 1.68 ± 0.07 in the acromegalic group (P < .01). Neither MN nor NDI was correlated with age, GH, IGF-I, initial GH, initial IGF-I, duration of the remission period, and initial tumor size. Only the MN level was positively correlated with the duration of disease (r = 0.323, P = .014).

CONCLUSION

Our results indicated that acromegalic patients had genotoxic damage at a substantial level, and there was a positive correlation between the duration of disease and genotoxicity level.

Validation of micronuclei frequency in peripheral blood lymphocytes as early cancer risk biomarker in a nested case-control study

Aim of this work was to assess the predictive value of micronuclei (MN) frequency in peripheral blood lymphocytes (PBL) for the risk of cancer death in disease-free individuals. Blood samples from 1650 subjects selected from the general population of Pisa, Italy, were collected between June 1991 and November 1993. The follow-up until January 2005 recorded a total of 111 deaths (52 for cancer). MN frequency was assessed for 49 cancer cases and 101 matched controls. A significantly higher MN frequency was found in cancer cases (4.7+/-3.4 MN/1000 BN cells) versus controls (1.5+/-1.7; p<0.0001). Donors were stratified in two classes and multivariate logistic regression analysis confirmed that individuals with high MN frequency (>2.5 MN/1000 BN cells) had a significantly increased risk of cancer death (OR=10.7; 95% CI=4.6-24.9; p<0.0001) when compared to individuals with low MN frequency (<or=2.5 MN/1000 BN cells). Ageing was associated with a 6% increased risk per year (p=0.03). No influence of other potential confounders (gender, occupation, smoking and drinking habits) was observed. Finally, subjects with a higher MN frequency showed a higher MR for CVD (Logrank test, p=0.001). These findings provide strong evidence that MN frequency assessed in PBL of disease-free subjects is a good predictor of cancer death risk, evaluated by a nested case-control study performed 14 years after the original recruitment.

Evaluation of micronuclei frequency in the cultured peripheral blood lymphocytes of cancer patients before and after radiation treatment

The frequency of micronucleated binucleate lymphocyte (MNBNC) was determined in the peripheral blood lymphocytes of patients suffering from various types of cancer before the onset of radiation treatment, middle (mid-) of the treatment and after completion of the treatment (post-treatment). The frequency of micronuclei increased significantly in the pretreatment sample of cancer patients when compared with the normal untreated healthy volunteers. During the middle of the radiotherapy an approximate two or > two-fold increase was observed in the micronuclei frequency in most of the patients when compared with the concurrent pretreatment samples. Immediately after the completion of treatment, the frequency of micronuclei further increased, and this increase was significantly higher than that of pretreatment and mid-treatment samples. Out of 27 patients analyzed, only nine patients did not have any history of smoking, tobacco chewing or alcohol consumption, while the remaining 18 patients had a history of either smoking, tobacco chewing or alcohol consumption or combination of two or all habits at the time of blood collection.

Increased spontaneous formation of micronuclei in cultured fibroblasts of first-degree relatives of familial melanoma patients

The phenomenon of spontaneous increased micronuclei and enhanced UV-sensitivity, which is known for familial cutaneous malignant melanoma (CMM) patients, could be demonstrated again in fibroblasts of 17 familial CMM patients. In order to determine if close relatives of familial CMM patients show both a comparable spontaneous chromosomal instability and enhanced UV-sensitivity, cultured fibroblasts of 24 healthy, first-degree relatives of patients with familial malignant melanoma were investigated. The cytokinesis-block micronucleous technique was used to detect enhanced chromosomal instability. Fibroblasts of the investigated relatives showed a significantly increased spontaneous formation of micronuclei, in comparison to 19 healthy controls, but no enhanced UV-sensitivity was evident. We conclude that chromosomal instability might be a hereditary trait and a causative factor in developing familial malignant melanoma. This supports the concept of a genetic predisposition to familial CMM and may help to identify high-risk family members at a cytogenetic level in addition to the common clinicopathological traits.

Induction of micronuclei and granular chromatin condensation in human skin fibroblasts influenced by cisplatin (cis-DDP) in vitro

Chromosomal damage was evaluated by quantification of micronuclei (MN) in two cell lines of human skin fibroblasts treated with different concentrations of cisplatin (ranging from 2 to 80 mumol/l) over the following time intervals: 2, 24 and 48 h. The formation of micronuclei was dependent upon the concentration of cis-DDP as well as on the duration of exposure. The dose-response curve for micronuclei in treated cells revealed a bell shape with the maximum at 12.5 mumol/l cis-DDP. The results were compared with another toxicological phenomenon, granular condensation of nuclear chromatin. This change, which was closely related to apoptosis in the cells exposed to cis-DDP, occurred at 5 mumol/l. The degree of condensation of nuclear chromatin depended on the concentration of cis-DDP. In contrast to the observations for micronuclei, the dose-effect relationship was linear up to the highest tested concentration (80 mumol/l). This change was primarily due to the duration of cis-DDP treatment. Our results showed the comparison between micronucleus formation and granular condensation of nuclear chromatin, as two morphological manifestations of cisplatin-induced DNA damage.

Increased mutagen sensitivity in human cultured fibroblasts with constitutively high micronucleus levels

The induction of micronuclei (MN) by incubation with different mutagenic agents was tested in diploid fibroblast cultures obtained from 15 probands with constitutively high MN rates (15.75-77.25 MN/500 cells; average 36.27 +/- 17.60 MN) and 15 probands (controls) with low MN rates (4-13.75 MN/500 cells; average 8.97 +/- 2.73 MN). In order to find out whether fibroblast cultures of individuals with increased spontaneous MN levels exhibit an increased sensitivity to various agents with different genotoxic mechanisms, we studied the induction of MN in these cell cultures by ultraviolet (UV) irradiation, mitomycin C (MMC), N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and benzo-(a)pyrene-diol-expoxid (BPDE). In addition, we tested aphidicolin (APC), a polymerase alpha inhibitor, which is a potent inducer of common fragile sites. Probands with spontaneously high MN showed an significantly increased sensitivity to UV (p less than or equal to 0.005), MMC (p less than or equal to 0.005), and BPDE (p less than or equal to 0.005). No significant differences were found for MNNG and APC as compared to controls.

Constitutively increased micronuclei are predominantly caused by acentric fragments

The frequency of kinetochore (centromere)-positive micronuclei (MN) was determined in 32 fibroblast cell lines. We tested 16 probands with spontaneously high MN levels (greater than or equal to 20 MN/500 cells (4%] and 8 probands (controls) with low MN levels (less than or equal to 13 MN/500 cells (2.6%]. To study whether the elevation of MN levels is due to increased chromosomal breakage we used the antikinetochore antibody fluorescent staining method. Probands with spontaneously high MN had kinetochore-positive MN increased by a factor 2.1 compared to the controls whereas the kinetochore-negative MN were increased by a factor 6.14. This shows that spontaneous elevation of MN is mainly caused by increased chromosomal breakage and only in a minor proportion by chromosome segregation errors as a consequence of spindle defects.

Elevated frequencies of micronuclei in cultured fibroblasts after freezing and thawing

Spontaneous micronuclei (MN) were determined in 69 fibroblast lines in the first subculture after cryoconservation. 45 cultures (65%) showed micronuclei in the normal range (less than 10 MN/500 cells), but 24 (35%) exhibited an elevation up to 60 MN/500 cells. In order to determine whether freezing and thawing is responsible for the enhanced MN level we studied the persistence of elevated MN in 10 cell cultures after freezing and thawing, and found that the MN levels returned to normal after 3 subcultures. In addition, the micronucleus formation before and after freezing was investigated in 2 newly established cell cultures obtained from probands whose cells had a particularly high number of MN. Both cultures had regular MN levels before freezing but a more than doubled number of MN when frozen samples were recultivated. This effect of the freezing procedure was confirmed with 5 separate biopsies obtained from the same donor. Since a freezing-related increase in MN was constantly observed in cells from some individuals but not in others, it might be possible that it is a constitutive trait which causes cultured fibroblasts of some individuals to be hypersensitive to the freezing and thawing procedure. It is also noteworthy that fibroblasts from 8 out of 12 probands with a familial malignant melanoma exhibited this phenomenon.