Advantages and limitations of using fluorescence in situ hybridization for the detection of aneuploidy in interphase human cells

Validation of primed in situ labeling (PRINS) for interphase analysis: comparative studies with conventional fluorescence in situ hybridization and chromosome analyses

Primed in situ labeling (PRINS) is a rapidly developing new technology with wide ranging clinical applications. To assess the sensitivity, specificity, and accuracy of PRINS, we carried out a retrospective study on cultured bone marrow cells to detect aneuploidy for chromosomes 7, 8, and 12. The results were then compared to the results of previous fluorescence in situ hybridization (FISH) and chromosome analyses (CA). In patients who showed aneuploidy with CA, both FISH and PRINS confirmed the aneuploidy in interphase cells. FISH and PRINS also showed excellent correlation with conventional cytogenetic analysis for the detection of mosaic aneuploidies. However, both FISH and PRINS showed significantly higher sensitivity in the detection of abnormal clones compared to CA. In 9 of the 17 cases, there were no significant differences in the detection rates between the two methods. Based on our studies, we conclude that PRINS is as sensitive as FISH in most cases for aneuploidy detection; and that PRINS, like FISH, is more sensitive than conventional CA for aneuploidy detection.

Micronuclei assay and FISH analysis in human lymphocytes treated with six metal salts

The capability of some metal compounds for inducing micronuclei (MN) in human lymphocytes was studied. In this investigation, Al (III), Cd (II), Hg (II), Sb (V), Te (VI), and Tl (I) salts were considered. The FISH (fluorescence in situ hybridization) technique with a centromeric probe was coupled with the MN assay in binucleated cells in order to detect both centromere-positive MN (C+ MN) due to malsegregation phenomena and centromere-negative MN (C- MN) due to chromosome breakage. The blood of two young nonsmoking male donors was employed for all experiments. In both donors, all the tested metal compounds, with the exception of Tl(2)SO(4), showed a statistically significant increase of MN compared to controls, at least at one dose. FISH analysis revealed an increase in the fraction of C+ MN for Al, Cd, and Hg compounds, and of C- MN for the Sb salt; however, this was not a statistically significant increase. A different efficiency was observed for the different metal compounds, in particular, KSbO(3) and CH(3)HgCl, which were highly genotoxic, whereas the others showed minimal effects.

Aneuploidy of chromosome 8 as detected by interphase fluorescence in situ hybridization is a recurrent finding in primary and metastatic breast cancer

Previous work from our laboratory demonstrated aneuploidy for several chromosomes by interphase fluorescence in situ hybridization (FISH) in a high proportion of breast cancer specimens. In the literature, only limited data are available concerning chromosome 8 anomalies in breast cancer. To determine chromosome 8 ploidy status in primary and metastatic specimens from 81 breast cancer patients, FISH analysis with a DNA probe recognizing chromosome 8 centromeres was performed. In all primary tumor specimens (n = 30), significant proportions of cells were aneuploid exhibiting gain of chromosome 8 copy numbers; in 75% of effusion specimens previously classified as malignant by cytology and/or FISH for various chromosomes (n = 40), cell populations aneuploid for chromosome 8 were detected; effusions previously classified non-malignant (n = 11) were diploid in 10 cases, whereas one specimen contained rare hyperdiploid cells. Among these cells complex chromosomal aneuploidy could be demonstrated by two-color FISH, suggesting malignancy. Trisomic and tetrasomic clones were predominant in the majority of samples, but a marked intratumor cytogenetic heterogeneity was observed in most cases. Primary tumors and corresponding positive axillary lymph nodes revealed similar distributions of chromosome 8 copy numbers, analogous to previous findings with other chromosomes. This implies that, by using suitable FISH probes after examination of the respective primary tumor, an efficient search for (micro)metastasis might be feasible.

Association of the NAT1*10 genotype with increased chromosome aberrations and higher lung cancer risk in cigarette smokers

The NAT1 gene exhibits polymorphisms in the non-coding polyadenylation region with a number of alleles. Of these alleles, NAT1*10 is responsible for increased NAT1 enzyme levels and is reported to be associated with increased risk for colorectal and bladder cancers. In view of the possible role of the NAT1 gene product in the metabolism of a number of cigarette smoke carcinogens, we tested the possibility that genetic variation in the NAT1 gene might also be associated with increased risk for lung cancer. Allelic variances of the NAT1 gene were analyzed in 45 lung cancer patients and 47 controls who were matched with respect to age, race and gender using restriction fragment length polymorphism (RFLP) analysis and allele-specific (AS)-PCR. Our results indicate that individuals who inherited the NAT1*10 allele had a 3.7-fold increased relative risk for lung cancer (95% CL = 1.2-16.0, p < 0.02). There was a 6.8-fold increase in relative risk for lung cancer associated with the inheritance of the NAT1*10 allele in younger individuals (< 60 years of age) compared to 2.2-fold increase in older individuals (> 60 years old) (OR = 6.8; 95% CL = 1.1-40.7, p < 0.01 and OR = 2.2; 95% CL = 0.5-11.1, p = 0.2, respectively). We have also applied the sensitive fluorescence in situ hybridization (FISH) tandem probe assay to elucidate the frequency of chromosome breakage among a subgroup of the studied individuals harboring the NAT1*10 allele (17 lung cancer patients, 17 smoking controls and 7 non-smoking controls). Our results indicate a significant increase (p < 0.001) in the frequency of chromosome breaks in lung cancer patients (mean +/- SE per 100 cells = 1.45 +/- 0.11) and in smoking controls (1.30 +/- 0.13) compared to non-smoking controls (0.47 +/- 0.07). Regression analysis indicated a highly significant positive correlation between the duration of smoking in years and the frequency of chromosome breaks in lung cancer patients (r = 0.62, p = 0.008), but not in smoking controls (r = 0.02; p = 0.91). These findings suggest that NAT1 polymorphism may be an important genetic determinant of lung cancer risk. In addition, these data provide a mechanistic link between the inheritance of the NAT1*10 allele and smoking-induced lung cancer. Given that the NAT1 enzyme can mediate activation and detoxication pathways for numerous carcinogens and given that this polymorphism is prevalent in the general population (20-50% frequency), it may play a significant role in influencing the outcome of a variety of environmental cancers.

Predisposing genes and increased chromosome aberrations in lung cancer cigarette smokers

Genotoxic effects linking cigarette smoking with lung cancer have not been consistently demonstrated, therefore claims for the cause-effect relationships are vigorously contested. Using matched populations of 22 lung cancer patients who have been cigarette smokers (LCP), 22 non-cancerous cigarette smokers (SC) and 13 non-smokers (NSC), we have applied the fluorescence in situ hybridization (FISH) tanden probe assay to elucidate the frequency of chromosome breakage among the participants. Two probes were used, a classical satellite probe which hybridizes to the large heterochromatin region of chromosome 1, and an alpha-satellite probe which targets a small region adjacent to the heterochromatin probe. The highest frequency of structural aberrations was observed in LCP (1.4 +/- 0.1) followed by SC (1.25 +/- 0.1) and NSC (0.4 +/- 0.1). Aberration frequencies were not significantly different between LCP and SC (p > 0.05), however, a statistically significant difference was detected between the smoker populations combined (LCP and SC) and the NSC (p < 0.001). The breakage frequencies showed a positive correlation with duration of smoking for LCP (r = 0.5; p < 0.01), but not for SC (P > 0.05). In addition, the aberration frequencies were influences by the inheritance of polymorphic glutathione S-transferase (GST) genes. LCPs missing one or the other GST (GSTM1 or GSTT1) genes were found to have significantly higher chromosome breaks compared to LCPs with both genes present (p < 0.05). Our data indicate that genetic predisposition and chromosome aberrations may be mechanistically related to the initiation of lung carcinogenesis; therefore, they may be useful biomarkers for lung cancer among cigarette smokers.

Disruption of microtubule assembly and spindle formation as a mechanism for the induction of aneuploid cells by sodium arsenite and vanadium pentoxide

Arsenic and vanadium are important environmental and industrial pollutants. Due to their widespread occurrence and potential genotoxicity, we studied the aneuploidy-inducing effects of these elements in cultured human lymphocytes using a variety of techniques including fluorescence in situ hybridization (FISH) with DNA probes for chromosomes 1 and 7, immunostaining of the lymphocyte spindle apparatus, and an in vitro assay measuring the polymerization and depolymerization of tubulin. Dose-related increases in hyperdiploidy were seen in lymphocyte cultures treated with sodium arsenite (NaAsO2) or vanadium pentoxide (V2O5) over concentrations ranging from 0.001 to 0.1 microM. NaAsO2-treated cells from different donors exhibited similar hyperdiploid frequencies, whereas substantial inter-individual variability was seen in the V2O5-treated cells. Examination of the spindle apparatus using an anti-beta-tubulin antibody indicated that these compounds might disrupt spindle formation by interacting with microtubules. Additional in vitro assays using purified tubulin indicated that both compounds inhibited microtubule assembly and induced tubulin depolymerization. These results indicate that in vitro exposure to both NaAsO2 and V2O5 can induce aneuploidy in human lymphocytes, and that this effect may occur through a disruption of microtubule function.

Interactions between genetic predisposition and environmental toxicants for development of lung cancer

Significant interindividual variations in health outcome may be caused by the inheritance of variant polymorphic genes, such as CYP2D6 and CYP2E1 for activation, and GSTM1 and GSTT1 for detoxification of chemicals. However, mechanistic studies linking the inheritance of predisposing genes with genotoxic effects towards cancer have yet to be systematically conducted. We have studied 54 lung cancer patients and 50 matched normal controls, who have been cigarette smokers, to elucidate the role of polymorphic genes in cancer. Our data indicates that the inheritance of unfavorable CYP2D6, CYP2E1, and GSTT1 genes in strongly correlated with the smoking-related lung cancer. For heavy cigarette smokers (> 30 pack-years), the smoking habit is the strongest predictor of lung cancer risk irrespective of the inheritance of unfavorable metabolizing genes. For moderate to light smokers (< 30 pack-years), the genetic predisposition plays an important role for the risk (odds ratio = 3.46; 95% Cl = 0.46-40.2). Using a subgroup of the study population, we observed that cigarette smokers having the defective GST genes have significantly more chromosome aberrations as determined by the fluorescence-in-situ-hybridization (FISH) technique than smokers with the normal GST genes (P < 0.001). In conclusion, our study provides data to indicate that individuals who have inherited unfavorable metabolizing genes have increased body burden of toxicants to cause increased genetic damage and to have increased risk for cancer. Studies like ours can be used to understand the basis for interindividual variations in cancer outcome, to identify high risk individuals and to assess health risk.

Interphase fluorescence in situ hybridization improves the detection of malignant cells in effusions from breast cancer patients

In diagnostic evaluation of effusions, difficulties are encountered when atypical reactive mesothelial cells have to be differentiated from malignant cells. We tested the impact of fluorescence in situ hybridization (FISH) to identify metastatic cells in breast cancer effusions by detection of numerical chromosomal changes. Pleural and ascitic fluid samples (n=57) from 41 breast cancer patients were concomitantly evaluated by routine cytology and FISH, using centromere-specific probes representing chromosomes 7, 11, 12, 17 and 18. After setting stringent cut-off levels deduced from non-malignant control effusions (n=9), the rates of cells with true aneuploidy were determined in each effusion sample from breast cancer patients. The occurrence of aneuploid cells, as detected by FISH and indicative of malignancy, was correlated with the cytological findings. Routine cytology revealed malignancy in 60% of effusions. Using FISH, aneuploid cell populations could be observed in 94% of cytologically positive and in 48% of cytologically negative effusions, thus reverting diagnosis to malignancy. To confirm malignancy in cases with a low frequency of aneuploid cells, two-colour FISH was additionally performed and indeed showed heterogeneous chromosomal aneuploidy within single nuclei. We conclude that FISH is a valuable tool in the diagnosis of malignancy and may serve as an adjunct to routine cytological examination, as demonstrated here for breast cancer effusions.