Pericentromeric Probes Research Articles

Cytogenetic analysis of gliomas by in situ hybridization of stereotactic biopsy material.

Chromosome analysis of brain tumours can provide important pathobiological data; however, cytogenetic tools are so far not routinely applied for diagnosis. In the present study 25 paraffin embedded stereotactic biopsies from 19 glioma patients were studied using in situ hybridization of chromosome #10 and #15 using biotinylated pericentromeric probes. Numerical changes of chromosome #10 are frequent alterations in glioblastoma. Quantification of chromosome #15 served as a control in order to exclude artificial monosomies or nonspecific changes. The number of chromosomes in at least 200 cells were counted for each specimen. 18 of 25 biopsies could be evaluated quantitatively. The small volume of probes was not a limiting factor for analysis. Quantification of "nonspecific" chromosome #15 revealed single spots in 22-41% of all cells in the 18 biopsies. Chromosome #10 showed single spots in a range between 34 and 44% of counted nuclei in 13/18 biopsies. In 5 out of 18 biopsies 51-60% monosomies were found: in this subgroup were 4 high grade gliomas. These cases were interpreted as monosomy of chromosome #10. The results demonstrate feasibility and quantitative evaluability of cytogenetic analysis in stereotactic biopsy material using in situ hybridization.

Chromosomal Anomalies in Stage D1 Prostate Adenocarcinoma Primary Tumors and Lymph Node Metastases Detected by Fluorescence in Situ Hybridization

We determined if characteristic chromosomal anomalies exist within the primary tumors and lymph node metastases in patients with stage D1 prostate cancer, and compared the patterns of chromosomal alterations between primary tumors and nodal metastases. Fluorescence in situ hybridization analysis using peri-centromeric probes for chromosomes 6, 7, 8, 17, X and Y was performed on 5 mu. sections from paraffin embedded tissue blocks obtained from 23 consecutive patients who underwent radical prostatectomy and bilateral pelvic lymphadenectomy in 1990 for stage D1 prostate cancer. The dominant focus of primary tumor was compared to matched nodal metastases in 12 cases. Five of 12 primary tumor foci (41.7%) had similar chromosomal gains and the same fluorescence in situ hybridization ploidy result as the corresponding nodal metastases. Chromosomes 7 and X (73.2% of cases) were most frequently gained in the primary tumors, and chromosomes X and Y (81.2% of cases) were most frequently gained in the metastases. No primary tumor or metastasis demonstrated chromosomal loss. Three of 19 primary tumors (15.7%) were diploid, while 16 of 19 (84.3%) were nondiploid. Chromosomal aneusomy was inversely correlated with increasing Gleason summary score. These data indicate that the dominant primary tumor foci may not give rise to nodal metastases, gains of chromosomes 7, X and Y may be associated with metastatic behavior, and patients with stage D1 disease have a greater rate of aneuploidy than those with lower stage cancer.

Assessment of intra-tumoral karyotypic heterogeneity by interphase cytogenetics in paraffin wax sections

Aim-To analyse the effect of sectioning on the assessment of karyotypic heterogeneity by interphase cytogenetics in paraffin wax embedded normal squamous epithelium and to apply the principles derived to invasive cervical carcinoma.Methods-Normal male (n = 5) and female (n = 5) squamous epithelia were hybridised with peri-centromeric repeat probes specific for chromosomes X (DXZ1) and 17 (D17Z1) individually and in combination to assess the effect of sectioning on mono-, di-, tri-, and tetrasomic populations. Section thickness, interobserver variation and variation between different areas of the epithelium were evaluated. Invasive squamous carcinomas of the cervix (n = 5) were then hybridised with the DXZ1 probe and intratumoral heterogeneity was assessed by comparison of signal distributions obtained from different areas.Results-The optimum section thickness for the assessment of normal epithelium was 6 mum. Variation in the expected signal number in the range 1-4 did not introduce artefactual heterogeneity at this section thickness. The sensitivity of this approach for the detection of minor subpopulations was calculated to be 13-16%, 17-18% and 10-11% for mono-, tri- and tetrasomic populations, respectively. Karyotypic heterogeneity was detected in two of the five tumours and, in one case where the populations where clustered morphologically, a minor population representing 18% was identified.Conclusions-Interphase cytogenetic analysis of sections from paraffin wax embedded material can be used for the detection of minor subpopulations in tumours. This approach will be of particular value in the assessment of the relation between human papillomavirus infection and tumour karyotype and in the analysis of intraepithelial neoplasia.

Numerical chromosome alterations in colorectal carcinomas detected by fluorescence in situ hybridization. Relationship to 17p and 18q allelic losses.

This study concerns DNA ploidy, numerical changes of chromosomes 7, 8, 10, 17 and 18, and allelic losses at chromosomes 17p13.3 (flanking the p53 gene) and 18q21 (location of the DCC gene) in 31 freshly resected colorectal tumours. Cytological smears were used to determine DNA ploidy by image analysis, and chromosome numbers by fluorescence in situ hybridization (FISH) using chromosome-specific pericentromeric alpha-satellite DNA probes. Allelic losses were assessed by Southern blotting and by the polymerase chain reaction loss of heterozygosity method. Approximately 50% of the tumours were aneuploid. There was heterogeneity with respect to chromosome numbers, but gains and losses of chromosomes, or both, were detected in all carcinomas examined, including 10 that were nonaneuploid by image analysis. Trisomy 7 was found in 74% of the tumours, and monosomy of chromosome 18 in 32%. Allelic loss at chromosome 17p13.3 was evident in 13 of 26 informative cases, and only one case exhibited monosomy 17. In comparison monosomy 18 was found in 10 cases; 7 of them corresponded to approximately half of the cases with allelic loss within the DCC gene, and the other three were noninformative. These findings indicate that the loss of one chromosome 18 is an important mechanism producing allelic deletion of the DCC gene in colorectal carcinomas. Our data also suggest that monosomy 18 is a useful indicator for studying colorectal cancer progression on a cell by cell basis.

Study on aneuploidy and p53 mutations in astrocytonias

To determine whether a correlation exists between aneuploidy and p53 status in astrocytic tumors we analyzed 48 astrocytomas with different grades of malignancy for the presence of p53 mutations and aneuploidy of chromosomes 10 and 17 (chi o, Chi 7), known to be particularly involved with this type of tumor. We used polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis on exons 5–8 of the p53 gene, and fluorescence in situ hybridization (FISH) analysis on interphase nuclei using chromosome specific pericentromeric probes, respectively. Our results showed that Ch1 OlChl7 aneuploidy is a common early event in astrocytomas (90% of low grade tumors are aneuploid). p53 mutations and Chi 7 aneuploidy are early events, but their incidence is not dependent on tumor grade. Loss of Chi 0 is the only alteration that significantly correlates with tumor progression. No significant correlation between the presence of Chi 0/Ch17 aneuploidy and p53 mutations was found. However, the coexistence of p53 mutations and aneuploidy, was observed in a subset of cases. The presence of p53 mutations appeared to be a significant predictor of a poor prognosis. In conclu sion genomic instability may or may not be associated with p53 mutations in astrocytomas, thus suggesting that other cellular determinants can also be responsible for the aneuploidy observed.

Interphase cytogenetics in mammographically detected breast lesions

Chromosomal aneuploidy in 25 mammographically detected breast lesions (MDBL) were determined on cytological smears using directly labeled pericentromeric probes for chromosomes 7 to 12, 17, 18, and X. The lesions included seven nonproliferative (NP) lesions, seven atypical hyperplasias (AHs), and 11 carcinomas (CAs). No other significant histological findings were identified in the remaining specimens except in two mammographically detected NP lesions, where foci of AH were present in adjacent sections; therefore, these two specimens were included in the AH lesion group (moderately increased risk lesions). Corresponding tissue sections were evaluated, and the results were correlated with fluorescent in situ hybridization (FISH) results. Monosomy was defined as the loss of one signal in ⩾ 15% of cells, and trisomy or tetrasomy was defined by the presence of three or more signals in ⩾ 3% of cells. Chromosomal aberrations were detected in 2 of 5 NP, 9 of 9 AH, and 11 of 11 CA groups. The mean number of cells with three or more signals, for all chromosomes, was 1.04 ± 0.9 in the NP group, 8.5 ± 9.4 in the AH group, and 20.2 ± 5.4 in the CAs. A significant statistical difference was noted between the different groups ( P = .0001). Chromo somal gain was the most common aberration and involved all chromosomes. The X chromosome was the only individual chromosome with significant differences in NP, AH, and CA groups. Chromosomal loss was observed in five specimens (20%) and involved chromosomes 8, 10, 17, and 18. The authors conclude (1) significant chromosomal aberrations can be detected in AH lesions and in NP epithelium from patients with moderately increased risk lesions; (2) numerical chromosomal aberrations tend to increase with progression of disease; (3) the frequent chromosomal gains/losses involving AH suggest that some AH may display submicroscopic features of malignancy; and (4) combined chromosomal aberrations allow for significant categorization of breast lesions, especially in cytology specimens.

Evaluation of chromosome aneuploidy in tissue sections of preinvasive breast carcinomas using interphase cytogenetics.

Little is known about cellular level genetic alterations in preinvasive breast lesions, particularly lobular carcinoma in situ. We employed fluorescence in situ hybridization (FISH) using pericentromeric (alpha satellite) probes to assess numerical alterations of chromosomes 1, 7, 8, 16, 17, and X in deparaffinized archival tissue sections of 9 lobular carcinomas in situ (LCIS), 10 ductal carcinomas in situ (DCIS), and a spectrum of proliferative lesions (including 3 ductal hyperplasias, 1 adenosis, 1 radial scar, and 2 atypical hyperplasias). Three of the LCIS lesions and five of the DCIS lesions were from patients who had a concurrent invasive neoplasm as a component of the tumor. None of the proliferative lesions exhibited detectable chromosome gains, and only 1 showed evidence of signal loss consistent with monosomy (chromosome 7 in the adenosis lesion). Six LCIS patients (67%) displayed evidence of monosomy, with involvement of chromosome 17 in 6 of 6 patients, chromosome 8 in 2 of 6 patients, and chromosome 7 in 2 of 6 patients. Two LCIS patients, each of whom had a concurrent invasive neoplasm, exhibited signal gains consistent with trisomy for chromosomes 1 and 8 (1 patient each). Chromosome aneuploidies were observed in 7 of 10 (70%) DCIS patients, including 2 of 5 patients (40%) without concurrent invasive neoplasm and 5 of 5 patients (100%) with concurrent invasive neoplasm. The pattern of numerical chromosome alteration in DCIS included two patients with losses only, 2 patients with gains only, and 3 patients with both gains and losses (i.e., involving different chromosomes). Chromosome 17 aneuploidy was observed in all DCIS and all LCIS patients who exhibited abnormalities; however, DCIS patients showed more frequent aneuploidies for chromosomes X and 16 (0 LCIS patients vs. 4 DCIS patients with each). Distinctive pathologic subsets of preinvasive breast neoplasia have divergent patterns of genetic instability. Foci of residual in situ neoplasia that accompany invasive disease may have a greater degree of genetic instability than neoplasms that lack progression to invasive phenotype.

Homologous centromere association of chromosomes 9 and 17 in prostate cancer

Chromosomal loss in cancer cells has been observed by nonisotopic in situ hybridization using pericentromeric probes. Accurate determination of this loss depends upon efficient hybridization and visualization of all probe signals in a two-dimensional field. Close association of homologous centromeres, reported in various normal and tumor tissues, can complicate evaluation and interpretation, resulting in the overestimation of actual chromosome loss. Using pericentromeric FISH probes for chromosomes 9 (classical and β-satellite) and 17 (α-satellite), as well as 17q-specific phage probes, we tested the frequency of homologous centromere association in normal and malignant prostate tissues and lymphoblastoid cells. We found that the pericentromeric region of both chromosomes 9 and 17 associated in prostate tissues, but only chromosome 9 demonstrated association in the lymphoblastoid cells. The association observed for chromosome 9 in both cell types appeared to be limited to the classical satellite III-type of heterochromatic, pericentromeric DNA. Using a single-copy probe along with the chromosome 17-specific pericentromeric probe, we determined that the association did not extend to the chromosome arms, but was limited to the pericentromeric region of chromosome 17. To accurately determine chromosome loss, we advocate the use of single-copy probes in addition to, or in place of, pericentromeric probes.

Frequent deletions of material from chromosome arm 1p in oligodendroglial tumors revealed by double-target fluorescence in situ hybridization and microsatellite analysis.

We undertook a cytogenetic analysis of 29 human brain tumors using double-target fluorescence in situ hybridization (FISH) and focusing on chromosome arm 1p. One or more tumor suppressor genes in this arm have been suggested to be important in a variety of neuroectodermal tumors. The series included 9 oligodendrogliomas, 4 mixed gliomas, 10 astrocytomas, 4 glioblastomas, and 2 central neurocytomas. We hybridized pericentromeric (1q12) and subtelomeric (1p36) DNA probes to cell nuclei prepared from paraffin-embedded tissues and observed a strikingly high incidence of deletion of at least part of 1p in oligodendrogliomas (100%) and mixed gliomas (75%). The results of the FISH analyses were confirmed by demonstration of loss of heterozygosity for a microsatellite polymorphism in 10 of the 29 tumors. As well as supporting the feasibility of FISH for detecting allelic deletions in chromosomes from paraffin-embedded tumor samples, the alteration of 1p reported here will contribute to an understanding of the molecular genetic events in oligodendroglial tumor development.

Nonrandom chromosomal gains in pilocytic astrocytomas of childhood

Low-grade astrocytomas are the most common central nervous system (CNS) tumor occurring in the pediatric age group. Although many of these tumors are karyotypically normal, various studies have reported gains of chromosomes in a significant proportion of cases. We had the opportunity to karyotype two pilocytic astrocytomas occurring in 5- and 15-year-old children. These tumors were characterized by stemlines of 49,XY,+4,+7,+8 and 48,XX,+7,+8. Using these patients as index cases and based on additional karyotypic data that have been published, we performed fluorescence in situ hybridization on 25 additional cases of low-grade astrocytomas in children using pericentromeric probes for chromosomes 4, 6, 7, 8, 9, 10, 11, 12, 15, and 17. Six of 18 (excluding the two index cases), or one third, of the pilocytic astrocytomas were characterized by chromosomal gains, most commonly chromosomes 7 and 8, suggesting that trisomy 7 and 8 are relatively common events in the tumorigenesis of pilocytic astrocytomas. In contrast, chromosomal trisomies were not detected in seven well-differentiated fibrillary astrocytomas with any of the probes chosen.

Correlation of numerical chromosome 11 and 17 imbalance with metastasis of primary breast cancer to lymph nodes.

Abnormalities of chromosomes 11 and 17 have been widely reported in invasive carcinoma of the breast. Interphase cytogenetics using pericentromeric repeat probes allows the evaluation of numerical chromosomal aberrations in tumour cell populations. We have developed a method for interphase cytogenetics on fine needle aspirates taken from breast tumours and have applied it to the analysis of chromosomes 11 and 17 in 49 cases of invasive adenocarcinoma. Frequency distributions of signal number were generated for each case and no correlation was found between modal signal number and tumour size at presentation, nodal status or tumour differentiation. In 14 cases, two copies of each of chromosomes 11 and 17 were present, and in 14, the number of chromosomes 11 and 17 were equal but abnormal. In 14 cases, the chromosome 11 number was greater than chromosome 17 and in 7 cases, the chromosome 17 number was greater than chromosome 11. Chromosome inequality correlated with the presence of lymph node metastases or disseminated disease at presentation and the absence of in situ carcinoma. There was no relationship with the presence of vascular invasion. These data suggest that numerical chromosome 11 and 17 imbalance may indicate the ability of breast cancers to metastasize rather than invade vessels. The pattern of numerical chromosome abnormality described may define a subgroup of tumours with a greater tendency for metastasis.

Interphase cytogenetics: Analysis of numerical chromosome aberrations in isolated cells

Probes which recognize pericentromeric repetitive sequences can be used to determine numerical chromosome aberrations in interphase nuclei. Under appropriate stringency conditions, these probes decorate only the chromosome from which they were derived. It has been assumed that abnormalities of signal number in interphase nuclei reflect aneuploidy rather than proliferation, but this has not been clearly demonstrated. In this paper, three alphoid probes (D3Z1, D11Z1, and DXZ1) were localized to the appropriate chromosomes and the factors governing the production of reproducible signal distributions from three aneuploid cervical carcinoma-derived epithelial cell lines were investigated. Abnormalities of signal number represent numerical chromosome aberrations rather than changes associated with proliferation. Using four simple rules of interpretation, reproducible results can be obtained with minimal technical variation and selection bias. These results demonstrate that pericentromeric repetitive probes can be used reproducibly to determine numerical chromosome aberrations independent of cell proliferation in interphase nuclei, a necessary prerequisite for the application of this approach to the analysis of human tumours.

Improved detection of DNA aneuploidy in primary breast cancer using quantitative DNA image analysis in combination with fluorescent in situ hybridization technique.

To obtain more information about the relationship between numerical aberrations of chromosome 1 and the overall DNA content of breast cancer cells, fluorescent in situ hybridization with a pericentromeric probe for this chromosome and image analysis based densitometry were carried out on imprints of benign (15 cases, mainly fibroadenomas) and malignant breast disease (31 invasive ductal carcinomas out of 45 cases). The most pronounced aneuploidy was observed in invasive ductal and lobular carcinoma cases both by in situ hybridization and DNA content (76.7 and 75.0% were aneuploid). The frequency of cells with two spots for chromosome 1 was 48.3 and 51.5%, respectively, as compared to 80.3% in control lymphocytes. There was a weak overall correlation (r2 = 0.83) between DNA content and copy number of chromosome 1 in the malignant samples, although some of the DNA diploid/near diploid carcinomas showed a marked aneusomy for this chromosome. Also, some aberrations were present in the benign breast disease samples. Classification of cases by a linear discriminant analysis was most accurate when both techniques were combined (77% of cases correctly classified, according to anatomo-pathological diagnosis). The variables which received the highest weight in the linear discriminant function are the percentage DNA-diploid cells and the fraction of cells with two spots for chromosome 1. The sensitivity and sources of error of both techniques is considered.

Chromosome aberrations in choroid plexus papillomas

Karyotypic data on choroid plexus papillomas are scarce and, to date, have revealed no consistent aberrations. We karyotyped a choroid plexus papilloma which was characterized by a stemline of 52,XX, + 7, + 11, + 12, + 12, + 15, + 18. Additional copies of chromosomes 16, 17, and 20 were also observed in a significant proportion of the metaphase cells analyzed. Based upon this index case, we retrospectively analyzed eight additional choroid plexus papillomas by fluorescence in situ hybridization by using pericentromeric probes to chromosomes 7, 11, 12, 15, 16, 17, 18, and 20. Extra hybridization signals were observed in five of the eight cases examined. All five cases had extra signals with the chromosome 7 probe, four cases had extra signals with the chromosome 12 probe, and three cases had extra signals with the chromosome 15, 17, and 18 probes. The overall DNA content of these same cases (as determined by image analysis) suggests that gains of additional chromosomes other than those examined may be present.

Aneusomy of chromosomes 7 and 17 detected by FISH in prostate cancer and the effects of selection in vitro.

Twenty prostate tumor specimens, obtained from radical prostatectomies, and two lymph node metastases were examined by classical and molecular cytogenetic methods. A sample from each tumor was analyzed histologically and used for touch preparations. Adjacent samples were used for preparation of single-cell suspensions before cell culture (DirFISH) and for establishing cell cultures, which were subsequently harvested for classical G-banding analysis. Fluorescence in situ hybridization (FISH) was performed on touch preparations, DirFISH, and cells obtained from tissue culture. Biotinylated pericentromeric probes for chromosomes 7 and 17, in addition to a digoxigenin-labeled X-chromosome probe, were used in a dual-color FISH assay. The results indicated that, in uncultured tumor cells, chromosome 17 was lost in 55% of specimens, chromosome 7 was gained in 16% of specimens, and 9% of specimens showed large tetraploid populations. After cell culture, 23% of specimens showed loss of chromosome 17, no specimens showed gain of chromosome 7, and no tetraploid populations were present. This study suggests that loss of chromosome 17 may play an important role in the development of prostate cancer, and that genetic changes observed after selection in vitro may not represent those in the original tumor.

Interphase Cytogenetics of Lung Tumors Using In Situ Hybridization: Numerical Aberrations

ObjectivesSince conventional cytogenetic analysis for bronchogenic carcinogenesis is limited by the difficulty to get enough number of high quality metaphase spreads, the development of new method to overcome above problems is strongly needed. Therefore, the introduction of non-radioactive in situ hybridization (ISH) with pericentromeric chromosome probes gave us the way to investigate the genetic events during carcinogenic process. We applied this method on lung cancer tissue to validate the possibility of this method for general usage and to analyze numerical chromosome aberration status and their clinical correlations.MethodsA set of satellite DNA probes specific for chromosome 3, 7, 9, 11, and 17 was hybridized directly to paraffin-embedded tissue section of 30 non-small cell lung cancers. Mean chromosome index of each chromosome and frequency of polysomy for each chromosome were calculated.ResultsMean chromosome indices for chromosome 3, 7, 9, 11, and 17 were 1.10, 1.13, 1.17, 1.12, and 1.17. respectively. Polysomy for a set of chromosomes was detected in all 30 cases except 4 cases which showed hypoploidy only for chromosome 3 or 7 in 2 cases and diploidy only for chromosome 3 or 11 in 2 cases. Among the set of chromosomes, mean chromosome index and polysomy frequency for chromosome 9 & 17 were significantly higher than that for others. Mean chromosome index or polysomy pattern for each chromosome was not much different among cell types or clinical stages.ConclusionsOur results show that chromosome ISH can be used to screen for numerical chromosome aberrations on paraffin tissue sections and further studies for ISH analysis with different probes on same tumor area or double-target ISH in large scale are needed to confirm above results and to elucidate the specific meanings.

Trisomy 12 in chronic lymphocytic leukemia and hairy cell leukemia: a cytogenetic and interphase cytogenetic study.

Fluorescent in situ hybridization (FISH) with a chromosome 12-specific pericentromeric probe was performed in 42 patients with B-cell chronic lymphocytic leukemia (CLL) and in 10 patients with hairy cell leukemia (HCL). In all cases, a normal karyotype in more than 10 metaphase cells was obtained by conventional chromosome study. FISH documented that 6/42 patients with CLL in fact had trisomy 12 in 15-49% interphase cells. Sequential FISH studies were performed in 2 cases, showing an increase of percentage of trisomic cells over a 2-month to 4-year period. Two out of 10 patients with HCL, one of whom had morphologic features consistent with a diagnosis of HCL variant, showed 5.5 and 10% interphase nuclei with three fluorescent signals, a finding suggestive of the presence of trisomy 12. Combined immunophenotyping and FISH staining in these patients with HCL documented that trisomic cells were CD11c-positive, CD13-negative, and CD2-negative. We conclude that FISH is a sensitive technique allowing for the detection of trisomy 12 in a fraction of cytogenetically normal patients affected with CLL and HCL.

Chromosomal aneuploidy in proliferative breast disease

Although some forms of proliferative breast disease have been associated with increased risk of breast cancer, substantial confirmatory evidence that the lesions are biologically premalignant has not been presented. Our intent was to identify cytogenetic aberrations in proliferative breast disease using fluorescence in situ hybridization probes selected for their relationship to aberrations previously reported in breast cancer. Application of fluorescence in situ hybridization techniques to paraffin tissue sections using pericentromeric probes for chromosomes 1, 16, 17, 18, and X revealed chromosome aneuploidy in proliferative and malignant lesions of the breast. Sectioning artifact that may result in nuclear truncation was controlled by establishing expected baseline frequencies for gain and loss in normal tissues from the same breast. Localization of chromosomal aberrations to proliferative breast disease lesions with concomitant retention of a normal chromosome complement in corresponding normal breast tissues indicates biologic significance of the results. The similarities of losses involving chromosomes 16, 17, and 18 in hyperplastic lesions and in malignant breast lesions suggest that some hyperplasias may be part of a sequence of progression to malignancy in breast cancer. Gains of chromosome 1 in both in situ and invasive carcinoma are consistent with reports of polysomy 1q as a common cytogenetic change in breast cancer. Its localization to advanced lesions suggests that this trisomy is probably not the initial cytogenetic change in breast cancer tumorigenesis.

Analysis of prostatic tumor cultures using fluorescence in-situ hybridization (FISH)

Analysis of ten primary prostatic tumor cultures using fluorescence in-situ hybridization (FISH) with pericentromeric probes for chromosomes 7, 8, 10, 16, 17, and 18 revealed aneusomies in nine of these specimens. Classical cytogenetics by G-banding indicated that only four of those same ten specimens had any (but not consistent) clonal abnormalities. This preliminary study suggests that aneusomy is a common event in early-stage prostatic tumors, and also supports the notion that multiple chromosomes are involved. In combination with routine cytogenetic analysis, FISH is thus likely to be a powerful tool in the evaluation of prostatic cancer.

Frequent occurrence of translocations of the short arm of chromosome 15 to other D-group chromosomes

The presence of DA/DAPI (distamycin A/4,6-diamino-2-phenyl-indole) heteromorphism on the short arm of human acrocentric chromosomes was investigated in 127 individuals. In 7 cases, a DA/DAPI signal was observed on an acrocentric chromosome other than 15. Subsequently, in situ hybridization (ISH) with a pericentromeric probe specific for chromosome 15 was carried out. In all 7 cases, three ISH signals were present in every metaphase, i.e., on both chromosomes 15 and on the third DA/DAPI-fluorescence-positive acrocentric chromosome (a chromosome 13 or 14), indicating that a chromosome 15 short arm was also present on these chromosomes. Therefore, we conclude that translocations of short arm sequences from chromosome 15 onto other D-group chromosomes occur frequently. Moreover, it appears that DA/DAPI staining remains specific for the short arm of chromosome 15, despite a number of recent papers suggesting otherwise.