Chromosomal instability in breast cancer patients

The Importance of Monitoring Non-clonal Chromosome Aberrations (NCCAs) in Cancer Research

Cytogenetic analysis has traditionally focused on the clonal chromosome aberrations, or CCAs, and considered the large number of diverse non-clonal chromosome aberrations, or NCCAs, as insignificant noise. Our decade-long karyotype evolutionary studies have unexpectedly demonstrated otherwise. Not only the baseline of NCCAs is associated with fuzzy inheritance, but the frequencies of NCCAs can also be used to reliably measure genome or chromosome instability (CIN). According to the Genome Architecture Theory, CIN is the common driver of cancer evolution that can unify diverse molecular mechanisms, and genome chaos, including chromothripsis, chromoanagenesis, and polypoidal giant nuclear and micronuclear clusters, and various sizes of chromosome fragmentations, including extrachromosomal DNA, represent some extreme forms of NCCAs that play a key role in the macroevolutionary transition. In this chapter, the rationale, definition, brief history, and current status of NCCA research in cancer are discussed in the context of two-phased cancer evolution and karyotype-coded system information. Finally, after briefly describing various types of NCCAs, we call for more research on NCCAs in future cytogenetics.

Understanding aneuploidy in cancer through the lens of system inheritance, fuzzy inheritance and emergence of new genome systems

BACKGROUND

In the past 15 years, impressive progress has been made to understand the molecular mechanism behind aneuploidy, largely due to the effort of using various -omics approaches to study model systems (e.g. yeast and mouse models) and patient samples, as well as the new realization that chromosome alteration-mediated genome instability plays the key role in cancer. As the molecular characterization of the causes and effects of aneuploidy progresses, the search for the general mechanism of how aneuploidy contributes to cancer becomes increasingly challenging: since aneuploidy can be linked to diverse molecular pathways (in regards to both cause and effect), the chances of it being cancerous is highly context-dependent, making it more difficult to study than individual molecular mechanisms. When so many genomic and environmental factors can be linked to aneuploidy, and most of them not commonly shared among patients, the practical value of characterizing additional genetic/epigenetic factors contributing to aneuploidy decreases.

RESULTS

Based on the fact that cancer typically represents a complex adaptive system, where there is no linear relationship between lower-level agents (such as each individual gene mutation) and emergent properties (such as cancer phenotypes), we call for a new strategy based on the evolutionary mechanism of aneuploidy in cancer, rather than continuous analysis of various individual molecular mechanisms. To illustrate our viewpoint, we have briefly reviewed both the progress and challenges in this field, suggesting the incorporation of an evolutionary-based mechanism to unify diverse molecular mechanisms. To further clarify this rationale, we will discuss some key concepts of the genome theory of cancer evolution, including system inheritance, fuzzy inheritance, and cancer as a newly emergent cellular system.

CONCLUSION

Illustrating how aneuploidy impacts system inheritance, fuzzy inheritance and the emergence of new systems is of great importance. Such synthesis encourages efforts to apply the principles/approaches of complex adaptive systems to ultimately understand aneuploidy in cancer.

Why it is crucial to analyze non clonal chromosome aberrations or NCCAs?

Current cytogenetics has largely focused its efforts on the identification of recurrent karyotypic alterations, also known as clonal chromosomal aberrations (CCAs). The rationale of doing so seems simple: recurrent genetic changes are relevant for diseases or specific physiological conditions, while non clonal chromosome aberrations (NCCAs) are insignificant genetic background or noise. However, in reality, the vast majority of chromosomal alterations are NCCAs, and it is challenging to identify commonly shared CCAs in most solid tumors. Furthermore, the karyotype, rather than genes, represents the system inheritance, or blueprint, and each NCCA represents an altered genome system. These realizations underscore the importance of the re-evaluation of NCCAs in cytogenetic analyses. In this concept article, we briefly review the definition of NCCAs, some historical misconceptions about them, and why NCCAs are not insignificant "noise," but rather a highly significant feature of the cellular population for providing genome heterogeneity and complexity, representing one important form of fuzzy inheritance. The frequencies of NCCAs also represent an index to measure both internally- and environmentally-induced genome instability. Additionally, the NCCA/CCA cycle is associated with macro- and micro-cellular evolution. Lastly, elevated NCCAs are observed in many disease/illness conditions. Considering all of these factors, we call for the immediate action of studying and reporting NCCAs. Specifically, effort is needed to characterize and compare different types of NCCAs, to define their baseline in various tissues, to develop methods to access mitotic cells, to re-examine/interpret the NCCAs data, and to develop an NCCA database.

Follow-Up Genotoxic Study: Chromosome Damage Two and Six Years after Exposure to the Prestige Oil Spill

BACKGROUND

The north-west coast of Spain was heavily contaminated by the Prestige oil spill, in 2002. Individuals who participated in the clean-up tasks showed increased chromosome damage two years after exposure. Long-term clinical implications of chromosome damage are still unknown.

OBJECTIVE

To realize a follow-up genotoxic study to detect whether the chromosome damage persisted six years after exposure to the oil.

DESIGN

Follow-up study.

SETTING

Fishermen cooperatives in coastal villages.

PARTICIPANTS

Local fishermen who were highly exposed (n = 52) and non-exposed (n = 23) to oil seven years after the spill.

MEASUREMENTS

Chromosome damage in circulating lymphocytes.

RESULTS

Chromosome damage in exposed individuals persists six years after oil exposure, with a similar incidence than those previously detected four years before. A surprising increase in chromosome damage in non-exposed individual was found six years after Prestige spill vs. those detected two years after the exposure.

LIMITATIONS

The sample size and the possibility of some kind of selection bias should be considered. Genotoxic results cannot be extrapolated to the approximately 300,000 individuals who participated occasionally in clean-up tasks.

CONCLUSION

The persistence of chromosome damage detected in exposed individuals six years after oil exposure seems to indicate that the cells of the bone marrow are affected. A surprising increase in chromosome damage in non-exposed individuals detected in the follow-up study suggests an indirect exposition of these individuals to some oil compounds or to other toxic agents during the last four years. More long-term studies are needed to confirm the presence of chromosome damage in exposed and non-exposed fishermen due to the association between increased chromosomal damage and increased risk of cancer. Understanding and detecting chromosome damage is important for detecting cancer in its early stages. The present work is the first follow-up cytogenetic study carried out in lymphocytes to determine genotoxic damage evolution between two and six years after oil exposure in same individuals.

Fluorescence in-situ hybridization technique as a diagnostic and prognostic tool in oral squamous cell carcinoma

Background and Objectives:

Early diagnosis and appropriate management are of prime importance for oral squamous cell carcinoma (OSCC) in the present scenario. Molecular changes in OSCC are well documented with the occurrence of a wide range of genetic damage. Identification of the genetic damage in OSCC using various diagnostic aids is mandatory, and one of the important advances in this field is cytogenetics using fluorescence in-situ hybridization (FISH). The aim of the present study is to analyze the genetic alteration in OSCC using FISH as a diagnostic aid.

Materials and Methods:

Peripheral blood was analyzed in 20 clinically and histopathologically proven OSCC cases and 10 healthy controls for chromosomal alteration under standardized conditions.

Results:

Of the 20 OSCC cases, 7 (35%) cases showed chromosomal alterations. No cases from the control group showed any chromosomal changes. Of the positive cases in OSCC, 30% cases showed increased copy number of cyclin D1 gene and 1 (5%) case showed positivity indicating extra copy of chromosome 11p11.11-q11 region.

Interpretation and Conclusion:

Increased genetic damage in OSCC which is a prominent feature can be identified by the use of FISH as seen from the present study. The findings suggest that FISH can be used as a diagnostic aid in the detection of genetic changes occurring in OSCC. The present study also suggests the importance of peripheral blood as a medium for assessing cytogenetic damage in OSCC.

Spontaneous and radiation-induced chromosomal instability and persistence of chromosome aberrations after radiotherapy in lymphocytes from prostate cancer patients

The aim of the study was to compare the spontaneous and ex vivo radiation-induced chromosomal damage in lymphocytes of untreated prostate cancer patients and age-matched healthy donors, and to evaluate the chromosomal damage, induced by radiotherapy, and its persistence. Blood samples from 102 prostate cancer patients were obtained before radiotherapy to investigate the excess acentric fragments and dicentric chromosomes. In addition, in a subgroup of ten patients, simple exchanges in chromosomes 2 and 4 were evaluated by fluorescent in situ hybridization (FISH), before the onset of therapy, in the middle and at the end of therapy, and 1 year later. Data were compared to blood samples from ten age-matched healthy donors. We found that spontaneous yields of acentric chromosome fragments and simple exchanges were significantly increased in lymphocytes of patients before onset of therapy, indicating chromosomal instability in these patients. Ex vivo radiation-induced aberrations were not significantly increased, indicating proficient repair of radiation-induced DNA double-strand breaks in lymphocytes of these patients. As expected, the yields of dicentric and acentric chromosomes, and the partial yields of simple exchanges, were increased after the onset of therapy. Surprisingly, yields after 1 year were comparable to those directly after radiotherapy, indicating persistence of chromosomal instability over this time. Our results indicate that prostate cancer patients are characterized by increased spontaneous chromosomal instability. This instability seems to result from defects other than a deficient repair of radiation-induced DNA double-strand breaks. Radiotherapy-induced chromosomal damage persists 1 year after treatment.

S. U, Yamini, A. P. S. B, Vasudha S. Chromosomal instability in the lymphocytes of breast cancer patients

Genomic instability in the tumor tissue has been correlated with tumor progression. In the present study, chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBLs) of breast tumor patients were studied to assess whether chromosomal instability (CIN) in PBLs correlates with aggressiveness of breast tumor (i.e., disease stage) and has any prognostic utility. Cultured blood lymphocyte metaphases were scored for aberrations in 31 breast cancer patients and 20 healthy age and sex-matched controls. A variety of CAs, including aneuploidy, polyploidy, terminal deletions, acentric fragments, double minutes, chromatid separations, ring chromosome, marker chromosome, chromatid gaps, and breaks were seen in PBLs of the patients. The CAs in patients were higher than in controls. A comparison of the frequency of metaphases with aberrations by grouping the patients according to the stage of advancement of disease did not reveal any consistent pattern of variation in lymphocytic CIN. Neither was any specific chromosomal abnormality found to be associated with the stage of cancer. This might be indicative of the fact that cancer patients have constitutional CIN, which predisposes them to the disease, and this inherent difference in the level of genomic instability might play a role in disease progression and response to treatment.

Chromosomal aberrations in lymphocytes of healthy subjects and risk of cancer

There is evidence that increased frequency of chromosomal aberration (CA) in peripheral blood lymphocytes is a predictor of cancer, but further data are needed to better characterize CA as marker of cancer risk. From the archives of 15 laboratories we gathered cytogenetic records of 11,834 subjects who were free of cancer at the moment of blood drawing and who underwent cytogenetic examination for preventive purposes in the Czech Republic during 1975-2000. We linked these records to the national cancer registry, revealing a total of 485 cancer cases. Subjects were classified according to the percentiles of CA distribution within each laboratory as low (0-33rd percentile), medium (34-66th percentile), and high (66-100th percentile). Subjects were further classified by occupational exposure and by subclass of CA. We found a significant association between the overall cancer incidence and the presence of chromosome-type aberrations [relative risk (RR) for high vs. low CA level = 1.24; 95% confidence interval (CI), 1.03-1.50] but not chromatid-type aberrations. Stomach cancer showed a strong association with frequency of total CA (RR = 7.79; 95% CI, 1.01-60.0). The predictivity of CA observed in subjects exposed to various classes of carcinogens did not significantly differ from the group of nonexposed subjects. This study contributes to validation of CA as a predictive marker of cancer risk, in particular, of stomach cancer; the association between CA frequency and cancer risk might be limited to chromosome-type aberrations.

Increased Rates of Chromosome Breakage in BRCA1 Carriers Are Normalized by Oral Selenium Supplementation

Women who are born with constitutional heterozygous mutations of the BRCA1 gene face greatly increased risks of breast and ovarian cancer. The product of the BRCA1 gene is involved in the repair of double-stranded DNA breaks and it is believed that increased susceptibility to DNA breakage contributes to the cancer phenotype. It is hoped therefore that preventive strategies designed to reduce chromosome damage will also reduce the rate of cancer in these women. To test for increased mutagenicity of cells from BRCA1 carriers, the frequency of chromosome breaks was measured in cultured blood lymphocytes following in vitro exposure to bleomycin in female BRCA1 carriers and was compared with noncarrier relatives. The frequency of chromosome breaks was also measured in BRCA1 carriers following oral selenium supplementation. Carriers of BRCA1 mutations showed significantly greater mean frequencies of induced chromosome breaks per cell than did healthy noncarrier relatives (0.58 versus 0.39; P < 10(-4)). The frequency of chromosome breaks was greatly reduced following 1 to 3 months of oral selenium supplementation (mean, 0.63 breaks per cell versus 0.40; P < 10(-10)). The mean level of chromosome breaks in carriers following supplementation was similar to that of the noncarrier controls (0.40 versus 0.39). Oral selenium is a good candidate for chemoprevention in women who carry a mutation in the BRCA1 gene.

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.

Telomeric association in women with breast and uterine cervix cancer

This study compares the frequency of telomeric associations in the peripheral blood of women suffering breast and cervix uterine cancer with a healthy control group. Two kinds of cultures were developed for each individual: with and without aphidicolin. In the normal cultures, the number of telomeric associations observed was 95.5 times higher in individuals affected by breast cancer and 41.3 times higher in those affected by cervix uterine cancer when compared to the control group (p < 0.001). In the cultures with aphidicolin, higher numbers of altered metaphases were observed in both groups as compared to the control groups (p < 0.001). Statistically significant differences (p < 0.001) could also be observed when comparing telomeric associations between the two types of cancer in both cultures. When we compared individuals affected by breast cancer in both types of cultures statistical differences were found (p < 0.05), and similar results were found in individuals affected by uterine cervix cancer (p < 0.001). The findings suggest that telomeric associations may be reflecting chromosome instability observed in cancer and that this instability behaves differently for various types of cancer.

Comparative study of chromosome aberrations induced with aphidicolin in women affected by breast cancer and cervix uterine cancer

Blood samples were obtained from 80 women: Twenty of these samples were from women affected by ductal infiltrating breast carcinoma, twenty from women affected by cervix uterine cancer, and forty individuals were screened for a control group. The search for chromosome instability that is known to affect individuals with cancer was performed through chromosome analysis in nontumor cells, intending to establish frequency and different types of numerical and structural aberrations. The results, in regard to spontaneous and aphidicolin induced chromosome aberrations, showed a significantly greater frequency (p < 0.001) of chromosome fragility, as well as other numerical and structural aberrations in breast cancer patients when compared to the control group. Similar results were obtained from cervix uterine cancer patients with the exception of certain numerical aberrations in which no significant differences were found. This suggests the existence of a certain degree of chromosomal instability affecting individuals with both types of cancer. The increase in fragility may play an important role in the biologic behavior and progression of cancer.

Cytogenetic studies on a patient with prepubertal breast cancer: a case report

Cytogenetic studies were carried in a 10 year old girl with prepubertal breast cancer for assessing inherited genetic susceptibility to chromosome breakage. The girl presented with a tumour in the left breast. Histologically it was diagnosed as secretory carcinoma (SC). Chromosome anomalies observed in phytohemagglutinin (PHA-P) stimulated lymphocytes were del(2)(q33), del(3)(p24), del(7)(q22) and dup(12)(p11p12). The regions involved have been reported in breast tumors. These loci, detected in peripheral blood lymphocytes (PBL), could be the sites susceptible to breakage, its subsequent effect being manifested in the target (breast) tissue.

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.