FISH: sensitivity and specificity on sorted and unsorted cells

Combined assessment of 3q26 amplification and promoter methylation in patients with high grade cervical lesions show age specific differences

A considerable proportion of high grade cervical intraepithelial lesions (CIN2/3) are known to resolve on their own especially among young women. However, since reliable prognostic markers are still lacking, the diagnosis "CIN3" is still an indication for surgery which may result in overtreatment. It is conceivable that a combination of different, ideally independent molecular markers may provide more reliable results. In the present cross-sectional study two established triage markers, 3q26 amplification and a methylation signature, were evaluated in an age-dependent manner. The patient cohort comprised 60 patients with histologically confirmed CIN2/3 in two equally sized age groups (<30 years, ≥30 years). Cervical scrapes were analyzed by interphase fluorescence in situ hybridization for 3q26 amplification and methylation specific PCR (GynTect®) for six different genome regions. Both assays showed a significantly different pattern of test outcome independent of age (P = .001). Moreover, the combination of both assays differed significantly for double positive and double negative cases when comparing the two age groups: In patients <30 years there were clearly less cases with positive methylation signature and amplification of 3q26 as in women ≥30 years (23% vs 63%, Bonferroni adjusted P = .016). Of particular interest is the finding that double negative results were exclusive for the young age group (0% vs 27%, Bonferroni adjusted P = .020). Since regression of CIN2/3 characteristically occurs among young women it is tempting to speculate that a double negative test result could be prognostic for regression of CIN2/3. This will have to be investigated further in a prospective longitudinal intervention study.

Detection approaches for multidrug resistance genes of leukemia

Leukemia is a clonal malignant hematopoietic stem cell disease. It is the sixth most lethal cancer and accounts for 4% of all cancers. The main form of treatment for leukemia is chemotherapy. While some cancer types with a higher incidence than leukemia, such as lung and gastric cancer, have shown a sharp decline in mortality rates in recent years, leukemia has not followed this trend. Drug resistance is often regarded as the main clinical obstacle to effective chemotherapy in patients diagnosed with leukemia. Many resistance mechanisms have now been identified, and multidrug resistance (MDR) is considered the most important and prevalent mechanism involved in the failure of chemotherapy in leukemia. In order to reverse MDR and improve leukemia prognosis, effective detection methods are needed to identify drug resistance genes at initial diagnosis. This article provides a comprehensive overview of published approaches for the detection of MDR in leukemia. Identification of relevant MDR genes and methods for early detection of these genes will be needed in order to treat leukemia more effectively.

Detection of Chromosomal Aberrations in Prostate Cancer by Fluorescence In Situ Hybridization (FISH)

PURPOSE

Fluorescence in situ hybridization (FISH) is a powerful tool for quantitative analysis of chromosomes and genes and can be applied in a variety of specimens, including cell cultures, isolated nuclei from fresh and fixed tissues, and histological tissue sections. For detection of numerical chromosome aberrations, we examined prostatic cancer samples at our department. In addition, we also observed primary and secondary aberrations taking part in the initiation and progression of tumours.

MATERIALS AND METHODS

FISH using chromosome-specific alpha-satellite DNA probes for chromosomes 7, 8, 9, 10, 17, X and Y was performed on 19 prostatic cancer and 19 benign prostatic hyperplasia (BPH) samples obtained from transurethral resection (TUR) and archival paraffin-embedded blocks.

RESULTS

Numerical aberrations were observed in 41% of the tumours studied. A range of aberrant copy numbers of chromosome 9 (68%), 7 (63%), 8 (58%), 17 (37%), Y (32%) and 10 (26%) was observed. We did not observe significant aberrations in BPH samples. In prostate cancer patients, chromosomes 7 (47%), 8 (58%) and 9 (63%) were monosomic by FISH. Monosomy 8 and 9 were significant differences (p>0.05) between prostate cancer and BPH patients.

CONCLUSIONS

FISH analysis could be observed an one of strongest methods of analysis in detecting numerical aberrations of individual chromosomes with application to paraffin-block samples, metaphase and, interphase nuclei. To our knowledge, this analysis is firstly studied in Turkish patients. Therefore, results of this analysis may be important for Turkish patients.

Maternal or fetal origin of rhesus monkey (Macaca mulatta) amniotic fluid leukocytes can be identified by polymerase chain reaction using the zinc finger Y gene

Leukocytes can be found in substantial numbers within the intrauterine tissues and amniotic fluid of women, and play a central role in the pathophysiology of infection-related preterm labor by their production of proinflammatory mediators. It remains unclear whether these leukocytes represent a fetal immune response, a maternal response, or a combination of the two. The objective of this study was to develop a test in the rhesus monkey (Macaca mulatta) suitable for determining the percentage of male fetal cells present in a population of leukocytes recovered from blood or amniotic fluid. We found inadequate specificity for rhesus monkey cells using commercial human Y-chromosome paint kits (fluorescence in situ hybridization (FISH)). Human-specific primers for the repetitive Y chromosome DYZ-1 locus employed in the polymerase chain reaction (PCR) produced an unacceptable percentage of false positives. However, we successfully developed a PCR-based test using rhesus-specific primers for the zinc finger Y (ZFY) locus. Densitometry of PCR products from known ratios of male and female adult peripheral leukocytes generated a linear standard curve which provided quantitative results and required only 400 cells per sample. The rhesus beta globin (RBG) gene served as an internal control. The PCR test correctly discriminated the sex of peripheral leukocytes in 20 adult males, 20 adult females, two male fetuses, and one female fetus. Serial samples of amniotic fluid from four chronically catheterized rhesus monkeys bearing male fetuses were used to confirm the utility of this assay for quantifying fetal cells in amniotic fluid. In conclusion, we have developed a PCR test which is suitable for distinguishing male from female cells in adult and fetal blood and in amniotic fluid, which lends itself to a variety of diagnostic and biologic applications in the rhesus monkey and potentially in other nonhuman primates.

[Detection of fetal cells in maternal blood: myth or reality?]

Fetal cells exist in maternal blood and can be utilized for prenatal diagnosis. These cells are present from the sixth week of gestation, with frequency increasing as gestation advances, to many years after the birth. Enrichment of trophoblast cells, erythroblasts and lymphocytes was performed with various density gradient techniques and either magnetic activated or fluorescent activated sorting techniques. The abnormalities were detected by fluorescent in-situ hybridation (FISH) with chromosome-specific DNA probes for the detection of trisomy 21, trisomy 18, Klinefelter syndrome 47 XXY, or by polymerase chain reaction (PCR) for the detection of fetal sex, certain Mendelian disorders (as beta-globin mutations), HLA polymorphisms and fetal Rhesus D blood type. However others studies were necessary to determine the sensitivity and specificity of this technique as a noninvasive alternative to conventional methods of prenatal cytogenetic diagnosis.

Optimization of the fluorescence in situ hybridization (FISH) technique for high detection efficiency of very small proportions of target interphase nuclei

Using commercially available fluorochrome-labeled probes specific for chromosomes X, Y, 13, 18, and 21, we optimized the technical protocols for fluorescence in situ hybridization (FISH) so that the highest sensitivity and specificity were achieved. Also, we compared the optical properties of different types of fluorescent labels in an effort to develop the most efficient FISH protocol, including the determination of which types of labels are the easiest to count accurately. The lymphocytes were purified from blood of normal male and female newborns, normal male and female adults, and a trisomy 21 male adult. Male and female lymphocytes were mixed in five different combinations. For each combination, the male lymphocytes either from newborns or from adults were diluted with female lymphocytes in seven different proportions. For each of these 35 different cell mixtures, 100,000 nuclei were analyzed and scored in a blind fashion. Among the different fluorochrome-labeled probes, the highest sensitivity and specificity were achieved when SpectrumAqua CEP-Y/SpectrumOrange CEP X probe mixture, SpectrumAqua CEP-18, SpectrumOrange LSI-13, and SpectrumOrange LSI-21 were hybridized. The hybridization sensitivity and specificity were higher than 99% for the identification of chromosomes X, Y, 13, and 18, and higher than 98% for the detection of trisomy 21. The proportion of false-positive signals was under 0.005% for XY detection and lower than 0.14% for autosome detection. With these high hybridization sensitivities and specificities, the optimized FISH protocol developed in our laboratory has the potential to detect very rare events, e.g., when the proportion of cells being sought is lower than 0.01%. In other words, our protocol allows the specific detection of one male cell sunken among 10,000 female cells.

Enrichment of fetal nucleated cells from maternal blood: model test system using cord blood

The presence of small numbers of fetal nucleated red cells in the maternal circulation has been a stimulus for the development of technologies for non-invasive prenatal genetic analysis. Our laboratory has been assessing the feasibility of density gradient centrifugation followed by magnetic activated cell sorting (MACS) of cells expressing CD32 and CD45, to deplete maternal nucleated blood cells. We have examined the efficiency of each of the steps of this procedure using cord blood from term pregnancies as a source of nucleated red blood cells. Cord blood was shown to contain highly variable numbers of nucleated red cells. Three different density gradients were examined. There was no major difference in the performances of the double and triple gradients. Density gradient centrifugation resulted in enrichments of nucleated red blood cells of about 1000-fold relative to the total cell count. However, it was apparent that the selection of the cell layers which were most enriched for these cells would result in significant losses of nucleated red cells in other layers. MACS sorting of cells using CD45 resulted in white cell depletions ranging from 7 to 34-fold. These data provide a foundation for comparison with other methods and for optimization of the MACS technique.