Chromosomal aneusomies detected by fluorescent in situ hybridization analysis in clinically localized prostate carcinoma

Mitotic Antipairing of Homologous Chromosomes

Chromosome organization is highly dynamic and plays an essential role during cell function. It was recently found that pairs of the homologous chromosomes are continuously separated at mitosis and display a haploid (1n) chromosome set, or "antipairing," organization in human cells. Here, we provide an introduction to the current knowledge of homologous antipairing in humans and its implications in human disease.

Somatic pairing of chromosome 19 in renal oncocytoma is associated with deregulated EGLN2-mediated [corrected] oxygen-sensing response

Chromosomal abnormalities, such as structural and numerical abnormalities, are a common occurrence in cancer. The close association of homologous chromosomes during interphase, a phenomenon termed somatic chromosome pairing, has been observed in cancerous cells, but the functional consequences of somatic pairing have not been established. Gene expression profiling studies revealed that somatic pairing of chromosome 19 is a recurrent chromosomal abnormality in renal oncocytoma, a neoplasia of the adult kidney. Somatic pairing was associated with significant disruption of gene expression within the paired regions and resulted in the deregulation of the prolyl-hydroxylase ELGN2, a key protein that regulates the oxygen-dependent degradation of hypoxia-inducible factor (HIF). Overexpression of ELGN2 in renal oncocytoma increased ubiquitin-mediated destruction of HIF and concomitantly suppressed the expression of several HIF-target genes, including the pro-death BNIP3L gene. The transcriptional changes that are associated with somatic pairing of chromosome 19 mimic the transcriptional changes that occur following DNA amplification. Therefore, in addition to numerical and structural chromosomal abnormalities, alterations in chromosomal spatial dynamics should be considered as genomic events that are associated with tumorigenesis. The identification of EGLN2 as a significantly deregulated gene that maps within the paired chromosome region directly implicates defects in the oxygen-sensing network to the biology of renal oncocytoma.

Together, renal oncocytoma and chromophobe renal cell carcinoma (RCC) account for approximately 10% of masses that are resected from the kidney. However, the molecular defects that are associated with the development of these neoplasias are not clear. Here, we take advantage of recent advances in genetics and computational analysis to screen for chromosomal abnormalities that are present in both renal oncocytoma and chromophobe RCC. We show that while chromophobe RCC cells contain an extra copy of chromosome 19, the renal oncoctyoma cells contain a rarely reported chromosomal abnormality. Both of these chromosomal abnormalities result in transcriptional disruptions of EGLN2, a gene that is located on chromosome 19 and is critical for the cellular response to changes in oxygen levels. Defects in oxygen sensing are found in other types of kidney tumors, and the identification of EGLN2 directly implicates defects in the oxygen-sensing network in these neoplasias as well. These findings are important because the chromosomal defect present in renal oncocytomas may also be present in other tumor cells. In addition, deregulation of EGLN2 reveals a unique way in which perturbations in oxygen-sensing are associated with disease.

Relative copy number gain of MYC in diagnostic needle biopsies is an independent prognostic factor for prostate cancer patients

OBJECTIVES

We have recently shown using comparative genomic hybridization (CGH) that 8q gain is an independent predictor of poor survival for prostate cancer patients. Because CGH may be difficult to implement in the clinical practice, we tested the feasibility of using a three-color fluorescent assay to assess 8q status in diagnostic, paraffin-embedded biopsy samples from prostate cancer patients.

METHODS

Fluorescence in situ hybridization with a dual-color probe flanking the MYC gene at 8q24 and a control probe for chromosome 18 was performed in a retrospective series of paraffin-embedded biopsies from 60 prostate cancer patients. The prognostic significance of 8q status was assessed by calculating disease-specific survival curves for these patients.

RESULTS

Whereas 44 (73%) samples displayed copy number gains of the MYC gene, a MYC/CEP18 ratio > or = 1.5 was detected in 36 (60%) samples. Kaplan-Meier curves with log-rank test showed that patients whose tumors displayed MYC/CEP18 ratio > or = 1.5 had a significantly worse disease-specific survival (p=0.003). The dual-color labelling of the MYC probe further allowed us to detect structural rearrangements of this gene in six (10%) carcinomas.

CONCLUSIONS

We show that a standard fluorescent protocol can successfully be applied to diagnostic needle biopsies to identify relative 8q gain in prostate carcinomas and that patients with a MYC/CEP18 ratio > or = 1.5 present a significantly higher risk of dying from the disease. The prognostic significance of this genetic variable was seen even for patients with Gleason score 7 or clinical stage II/III carcinomas, whose clinical behavior is currently difficult to predict.

Molecular biology in prostate cancer

Genes involved in cancer generation are usually tumor suppressors and oncogenes. Progressive genetic alterations in these genes are involved in the mechanisms of tumorigenesis. In prostate cancer, additionally several chromosomal loci that should harbor mutated genes have been proposed. Some genes have been found altered in prostate cancer, such as PTEN, TP53, AR, RNASEL (HPC1), ELAC2 (HPC2), CDKN2A and MSR1 and those can be natural targets for new strategies of treatment. Besides, gene therapy has been suggested to be suitable for prostate cancer treatment. This approach includes ex vivo corrective therapy, suicide, and antisense therapy.

Fluorescence in situ hybridization analysis of matched primary tumour and lymph-node metastasis of D1 (pT2-3pN1M0) prostate cancer

OBJECTIVE

To describe the chromosomal numerical changes present in primary prostate tumours and their matched lymph-node metastases, to identify a clonal cell migration process which could account for the metastatic behaviour.

MATERIALS AND METHODS

Twenty-eight cases of unsuspected stage D1 (pT2-3pN1M0) prostate cancer were detected among patients who had a radical prostatectomy for clinically localized prostate cancer. Fluorescence in situ hybridization (FISH), using centromeric probes to enumerate chromosomes 7, 8, 10 and 12, was used to assess numerical chromosomal changes. FISH analysis was used on isolated nuclei obtained from matched primary tumours and their lymph node metastases.

RESULTS

Of the 28 suitable cases it was possible to complete the study in 18 pairs of matched tissues; the remainder were excluded because of insufficient tissue or poor preservation of at least one of the tissues. There was cytogenetic change (aneuploidy) in 16 of the 18 primary tumours, the most common being monosomy 8, detected in 14, followed by trisomy 7, in 13 aneuploid tumours. All lymph node metastases were aneuploid by FISH. As in the primary tumours, monosomy 8 and trisomy 7 were the most common cytogenetic alterations, in 13 and 15 of the lymph node tissues. FISH analysis showed a high correlation (83%) in the cytogenetic pattern of changes between the primary tumours and their lymph node metastases. Moreover, a similar number of cells had the most common aneusomies when comparing prostate and the lymph node tissues.

CONCLUSIONS

These results show a similar pattern of cytogenetic alteration in the primary tumour and its lymph node metastasis, characterized by the frequent presence of trisomy 7 and monosomy 8, suggesting that clonal cell selection is not involved in the metastatic process.

Gain of androgen receptor gene copies in primary prostate cancer due to X chromosome polysomy

BACKGROUND

Prostate cancer is an androgen dependent tumor. In advanced prostate cancers androgen deprivation has proved to be an effective therapy, but 25% show no response. In this study prostatectomy specimens from patients without preoperative therapy were analyzed to determine the possible mechanism of primary antiandrogen resistance.

METHODS

The number of androgen receptor (AR) gene copies and X-centromeres were investigated from 80 prostate cancer specimens by FISH analysis.

RESULTS

In 9 out of 80 prostate cancers additional X-chromosomes with the corresponding AR gene could be detected. Polysomy of the X-chromosome correlates with pathological classification and tumor volume.

CONCLUSIONS

Additional AR genes due to polysomy of the X-chromosome are present in a subgroup of primary prostate cancers prior to antiandrogen therapy. Because the growth of prostate cancers is androgen dependent, these specimens may have an advantage in low concentrations of androgens. This may be a factor for initial antiandrogen resistance.

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.

Genetic markers useful for distinguishing between organ-confined and locally advanced prostate cancer

Prostate cancer is one of the most commonly diagnosed cancers and the second leading cause of cancer deaths among men in the United States. In this study, we performed comparative genomic hybridization (CGH) on 45 primary prostate adenocarcinomas to determine genetic markers that could be useful for distinguishing between organ-confined and locally advanced prostate cancer. Of these tumors, 24 were pT2 stage, 21 were pT3b; 20 had low Gleason scores (GS), 25 had high GS. The most common chromosomal alterations in all 45 tumors included losses on 8p (57.8%), 10q21-->qter (40.0%), 16q (35.6%), 11q21-->qter (28.9%), 16p (22.2%), 6q22-->24 (22.2%), 10p (20.0%), 5q31-->qter (17.8%), 6p (17.8%), 15q22-->qter (15.6%), and 17p (15.6%) as well as gains on 7cen-->p14 (20.0%), 7cen-->q22 (20.0%), and Xcen-->q21 (17.8%). Contingency table analysis showed that losses of 8p, 10q25-->qter, 6p21, 6q24-->qter, and 15q22-->qter were significantly increased in frequency (P < 0.05) with increasing stage and/or GS. A model was created following multivariate logistic regression analysis that was predictive of tumor stage in approximately 90% of the tumors studied. This model suggests that loss of 8p is the most valuable predictor of stage. These findings suggest that chromosomal regions identified in this study may be useful for distinguishing between organ-confined and locally advanced prostate tumors.

Chromosome 7 aneusomy. A marker for metastatic melanoma? Expression of the epidermal growth factor receptor gene and chromosome 7 aneusomy in nevi, primary malignant melanomas and metastases

Receptor tyrosine kinases such as the epidermal growth factor receptor (EGFR) play an important role in a variety of malignant neoplasias, making the search for aberrations in the relevant chromosomes an important issue. Differential expression of the EGFR gene was investigated by reverse transcriptase (RT)-PCR on tissue samples of normal skin, nevi, primary melanomas, and melanoma metastases. The EGFR gene is located on chromosome 7p12.3-p12.1. To determine the number of chromosomes 7 in cell nuclei of the mentioned tissue samples we performed fluorescence in situ hybridization (FISH) on touch preparations, using a DNA probe that hybridizes specifically to the centromeric region of chromosome 7. Additionally, chromosome 7 number in interphase nuclei was determined in short-term primary cell cultures of nevi, primary melanomas, and metastases. The highest EGFR gene expression frequency was found in melanoma metastases. By FISH we detected the highest fraction of cell nuclei with more than two chromosomes 7 in the group of metastases. Our results suggest that overexpression of the EGFR gene might play an important role in metastasis of malignant melanoma. This is well reflected by polysomy 7, possibly accounting for an increased EGFR gene copy number.

High-grade prostate intraepithelial neoplasia shares cytogenetic alterations with invasive prostate cancer

BACKGROUND

High-grade prostate intraepithelial neoplasia (PIN) is the most likely precursor of prostate adenocarcinoma. However, the relationship between this lesion and prostate cancer has not yet been established. The detection of cytogenetic changes in the lesions prior to prostate adenocarcinoma would be useful in demonstrating such a pathogenic relationship.

METHODS

Twenty eight high-grade PIN cases were found among 57 specimens of radical prostatectomy performed for clinically localized prostate cancer. Fluorescence in situ hybridization (FISH) analysis using centromeric probes to enumerate chromosomes 7, 8, 10, and 12 was performed to study the numerical chromosome alterations. FISH analysis was carried out over isolated nuclei obtained from high-grade PIN areas and prostate cancer foci in the same prostatectomy specimen.

RESULTS

Of the 28 suitable cases it was possible to complete the study in 26 tumor and 20 PIN areas. The remaining cases were excluded because of insufficient tissue or poor preservation. Cytogenetic alterations (aneuploidy) were found in 16 of the 26 (62%) tumors studied. The most frequent chromosome alteration was trisomy 7, detected in 12 (75%) aneuploid tumors, followed by monosomy 8 present in 5 (31%) aneuploid tumors. Trisomy 7 was also the most frequent isolated chromosome alteration since it was detected in 7 (44%) tumors. Thirteen of 20 (65%) PIN cases were aneuploid when studied by FISH. Trisomy 7, trisomy 8, and monosomy 8 were the most common cytogenetic alterations in the 20 PIN areas studied, being observed in nine (45%), six (30%), and four (20%) cases, respectively. FISH analysis showed a high correlation (75% cases) in ploidy and pattern of cytogenetic alterations between high-grade PIN areas and the paired prostate cancer focus in the same specimen.

CONCLUSIONS

The above results show a cytogenetic link between high-grade PIN and prostate cancer, suggesting that the former could be an early form of prostate cancer.

Cellular and molecular pathology of prostate cancer precursors

Prostate cancer is usually heterogeneous and multifocal, with diverse clinical and morphologic manifestations. Current understanding of the molecular basis for this heterogeneity is limited, particularly for prostatic intraepithelial neoplasia (PIN), the only putative precursor which can be identified according to morphologic criteria. However, it is likely that prostatic adenocarcinoma might arise from precursor lesions other than PIN, although these cannot be recognized with certainty at the present time. In this review, we summarize the current state of knowledge regarding the cell-biological and genetic bases for linking PIN and prostatic adenocarcinoma. It is conceivable that a stem cell of basal phenotype, or an amplifying cell, is the target of prostatic carcinogenesis. Prominent genetic heterogeneity is characteristic of both PIN and carcinoma; and multiple foci of PIN arise independently within the same prostate. This observation suggests that a field effect probably underlies prostatic neoplasia. Multiple foci of cancer also often arise independently, lending additional support to this hypothesis. The strong genetic similarities between PIN and cancer strongly suggest that evolution and clonal expansion of PIN, or other precursor lesions, may account for the multifocal etiology of carcinoma. Uncertainties with respect to identification of those precursor lesions which are most likely to progress to invasive and metastatic prostate cancer reinforce the requirement for objective immunohistochemical or molecular biological markers of the aggressive phenotype.

Two putative tumor suppressor genes on chromosome arm 8p may play different roles in prostate cancer

Although loss of heterozygosity (LOH) on the short arm of chromosome 8 has been frequently observed in human prostate cancer, the relationship between LOH and clinical background is poorly understood. Fluorescence in situ hybridization (FISH) was employed to evaluate the chromosomal deletion on 8p in 42 prostate cancers using a centromeric probe for chromosome 8, in combination with 4 cosmid probes spanning 8p12 to 8p22. Deletions for at least one locus on the 8p were observed in 29 (69.0%) tumors. The most frequently deleted regions were 8p22 (54.8%) and 8p21.3 (52.4%), in almost the same frequency. The second most frequently deleted region was 8p21.1-p21.2 (38.1%). Deletions of 8p22 and 8p21.3 significantly correlated with tumor grade (P=0.0034, Fisher's exact probability test). A significantly higher frequency of the deletion on 8p21.1-p21.2 was observed in advanced prostate cancer (beyond capsular penetration or positive nodal metastases) than in localized prostate cancer (P=0.0033). In particular, deletion of 8p21.1-p21.2 was more frequently observed in the cases with lymph node metastases than without them (P=0.0029). No clinicopathological parameters had significant relation to deletions on 8p12. These results suggest that deletions on 8p22-p21.3 play an important role in tumor differentiation, while an 8p21.1-p21.2 deletion plays a role in the progression of prostate cancer.

Numerical chromosomal changes in metastatic prostate cancer following anti-androgen therapy: fluorescence in situ hybridization analysis of 5 Japanese cases

We used fluorescence in situ hybridization with centromere-specific probes for chromosomes 7, 8, 10, and Y to determine the copy number of these chromosomes in metastatic prostate cancers of five Japanese cases. Freshly prepared samples were obtained from prostate needle biopsies at different phases of clinical treatment; pretreatment, 1 week, 4 weeks, 12 weeks, 24 weeks post-treatment (PT), and clinical relapse. Gain of chromosomes 7 and 8, as noted in pretreatment samples; however, in post-treatment specimens (four of five cases), a remarkable reduction in the number of cells with extra copies of these chromosomes was detected. This decrease in the number of cells with additional chromosome 7 and 8 signals was correlated with the clinicohistopathological findings until 4 weeks PT. Chromosomes Y and 10 did not show numerical aberrations before treatment or changes in cells with aneusomy after treatment in all five cases. Our results suggest that gains of chromosomes 7 and 8 correlate with high grade and stage, and that changes in the cell number with aneusomy of chromosomes 7 and 8 reflect the clinical effects of anti-androgen therapy at an early phase, which may also indicate the androgen dependency of prostate cancer cells.

Fluorescence in situ hybridization evaluation of c-myc and androgen receptor gene amplification and chromosomal anomalies in prostate cancer in Japanese patients

BACKGROUND

Oncogene amplification and chromosomal anomalies are found in many solid tumors and are often associated with aggressiveness of cancer. We evaluated the frequency and the association of c-myc and androgen receptor (AR) gene amplification and gain of chromosome 8 or X in prostate cancer in Japanese patients.

METHODS

We examined a total of 42 prostate cancer specimens, using fluorescence in situ hybridization (FISH). Dual-labeling hybridization with a directly labeled centromere probe for chromosome 8 or X together with a probe for the c-myc or AR locus was performed.

RESULTS

Gain of chromosome 8 was identified in 54.8% of specimens and was associated with Gleason sum and nuclear anaplasia in untreated prostate cancers. c-myc gene amplification was found in 14.3% of specimens. Gain of chromosome X was identified in 42.9% of specimens. AR gene amplification was detected in 0 of 37 untreated prostate cancers, but in 1 of 5 hormone-refractory prostate cancers.

CONCLUSIONS

Our results suggest that c-myc and AR gene amplification and gain of chromosome 8 or X may be associated with the development and progression of prostate cancers. These results obtained in Japanese cases are consistent with the results observed in prostate cancer in Western countries.

Identification of two distinct regions of allelic imbalance on chromosome 18Q in metastatic prostate cancer

Like most cancers, prostate cancer (CaP) is believed to be the result of the accumulation of genetic alterations within cells. Previous studies have implicated numerous chromosomal regions with elevated rates of allelic imbalance (AI), using mostly primary CaPs with an unknown disease outcome. These regions of AI are proposed sites for tumor suppressor genes. One of the regions previously implicated as coding for at least one tumor suppressor gene is the long arm of chromosome 18 (18q). To confirm this observation, as well as to narrow the critical region for this putative tumor suppressor, we analyzed 32 metastatic CaP specimens for AI on chromosome 18q. Thirty-one of these 32 specimens (96.8%) exhibited AI at one or more loci on chromosome 18q. Our analysis using 17 polymorphic markers revealed statistically significant AI on chromosome 18q at 3 markers, D18S35, D18S64 and D18S461. Using these markers as a guide, we have been able to identify 2 distinct minimum regions of AI on 18q. The first region is between the genetic markers D18S1119 and D18S64. The second region lies more distal on the long arm of the chromosome and is between the genetic markers D18S848 and D18S58. To determine if 18q loss is a late event in the progression of CaP, we also examined prostatic intraepithelial neoplasia (PIN) and primary prostate tumors from 17 patients for AI with a subset of 18q markers. We found significantly higher AI in the metastatic samples. Our results are consistent with 18q losses occurring late in CaP progression.

Detection of numerical chromosome anomalies in interphase cells of benign and malignant thyroid lesions using fluorescence in situ hybridization

Benign and malignant thyroid tumors constitute a wide range of neoplasias showing recurrent chromosome abnormalities. In an attempt to characterize specific numerical chromosome abnormalities in thyroid tissues, we present here the findings from a study of archival samples depicted by 10 malignant tumors, 30 benign lesions, and 10 normal thyroid tissues. Fluorescence in situ hybridization was performed on noncultured samples using biotinylated centromere-specific probes for chromosomes 7, 10, and 17. Trisomy or tetrasomy 7 were present in 19 benign and in 7 malignant tumors. Trisomy 10 or 17 were observed in 18 adenomas or goiters and in 9 carcinomas, and monosomy 17 was seen in 2 carcinomas. Our findings suggest that such abnormalities are an in vivo phenomenon and may be important in the neoplastic proliferation of thyroid gland.

Fluorescence in situ hybridization aneuploidy as a predictor of clinical disease recurrence and prostate-specific antigen level 3 years after radical prostatectomy

OBJECTIVE

To determine if fluorescence in situ hybridization (FISH) analysis of fresh-tissue biopsy specimens obtained at the time of radical prostatectomy is able to predict prospectively clinical disease progression or prostate-specific antigen (PSA) level in patients 3 to 4 years after surgery.

MATERIALS AND METHODS

FISH analysis was performed on fresh-tissue touch preparations obtained from 90 randomly selected radical prostatectomy specimens. Cut surface touch preparations from 40 specimens resected in 1992 were analyzed with DNA probes for chromosomes 4, 6-12, 17, 18, X, and Y. Needle-biopsy specimens were obtained from 50 tumors resected in 1993, and touch preparations from these specimens were studied with DNA probes for chromosomes 7, 8, 11, and 12. Serum PSA levels and clinicopathologic data were recorded, and each patient was followed up from the time of surgery to determine cancer progression.

RESULTS

Of 90 patients undergoing radical prostatectomy in 1992 and 1993, 89 returned for follow-up. Three patients received preoperative hormonal therapy, and in 2 patients, antiandrogen therapy was continued postoperatively. Fifteen patients underwent intraoperative orchiectomy immediately after radical prostatectomy, while 9 patients had postoperative adjuvant hormonal therapy. Six patients underwent postoperative radiation therapy. Fourteen patients (15.7%) demonstrated systemic, local, or PSA progression. Only 2 (4.7%) of 43 patients with FISH diploid tumors demonstrated cancer progression. Conversely, 10 (30.3%) of 33 FISH aneuploid and 12 (26.1%) of 46 FISH nondiploid tumors demonstrated cancer progression (P=.004 and P=.006, respectively). Unlike FISH, flow cytometric aneuploidy was not associated with early cancer progression. Elevated preoperative PSA concentration, increased preoperative and postoperative Gleason score, and increased preoperative and postoperative T or N stage were not statistically significantly associated with cancer progression. While chromosome 7 and 8 aneusomies were not statistically associated with cancer progression, 2 of 5 (P=.04) chromosome 12 aneusomic tumors demonstrated cancer progression.

CONCLUSION

Early (within 4 years) local, systemic, or PSA progression occurred more frequently (P<.05) in radical prostatectomy patients with FISH aneuploid, nondiploid, and chromosome 12 aneusomic tumors. Flow cytometric ploidy status, preoperative serum PSA concentration, and clinical or pathologic grade or stage, including seminal vesicle involvement, margin status, and capsular perforation status, were not associated with early prostate cancer progression in this group of 89 patients. FISH analysis appears to be a useful preoperative tool for predicting aggressive vs indolent prostate cancer.

Assessment of chromosomal trisomies in prostate cancer using fluorescent in situ hybridization

In a previous study, we observed a low frequency of HER-2/neu oncogene amplification in prostate cancer using fluorescent in situ hybridization (FISH). In our continued effort to identify prognostic biomarkers in prostate cancer, we analyzed 74 cases of prostate cancer to assess the presence of chromosomal trisomies in this cohort of patients. Previous results from this laboratory have implicated a role of chromosomal trisomies in various cancers. FISH using a chromosome 7 and a chromosome 8 centromere probe was utilized to study abnormal chromosome copy numbers together with data from a chromosome 17 control. The frequency of trisomy 7 was found to be 58.1% (43 of 74 informative cases), while the frequency of trisomy 8 was found to be 9.5% (7 of 74 informative cases). The frequency of cells showing chromosome 17 trisomy was 18.5% (15 of 81 cases successfully studied). While chromosome 8 trisomy did not seem to play as significant a role here as in other cancers that we studied, the results of chromosome 7 trisomy are consistent with those reported in the literature. Further exploration of selected trisomies as biomarkers in prostate cancer using a larger study sample size is warranted to establish their clinical utilities.

Chromosomal basis of adenocarcinoma of the prostate

Prostate cancer is the most frequent malignancy and the second leading cause of cancer deaths among males in the Western world. The clinical course of the disease is highly complex, and genetic factors underlying tumorigenesis are poorly understood. The challenge that lies ahead is to identify the important gene(s) that causes adenocarcinoma of the prostate. Chromosomal findings by cytogenetic and molecular methods, including Southern blotting, microsatellite analysis, fluorescence in situ hybridization, and comparative genomic hybridization, revealed a high frequency of chromosomal aberrations of heterogeneous nature, including: -1, +1, -1q, +4, -6q, -7, +7, -8, -8p, -8q, +i(8q), -9, -9p, -10, +10, +11, -12, -13q, -16, -16q, +16, -17, +17, +17q, -18, +18, -18q, +19p, +20q, +X, -Xq, -Y, and +Y. Specific chromosomal regions of alterations were 1q24-25, 2cen-q31, 5cen-q23.3, 6q14-23.2, 7q22-q31, 8p12-21, 8p22, 8q24-qter, 10q22.1, 10q23-25, 11p11.2, 16q24, 17p13.1, 18q12.2, and Xq11-12. Recently, a predisposing gene for early onset has been localized on 1q42.2-43. The losses of heterozygosity at specific chromosomal loci from chromosomes 5q, 6q, 7q, 8p, 8q, 10q, 13q, 16q, 17p, 17q, and 18q are generally correlated with poor prognosis in advanced tumor stage. In addition, an abnormal function of known tumor suppressor genes from these regions have been observed in prostate cancer. Although, the amplification of the androgen receptor gene at Xq11-13 and HER-2/neu gene at 17q11.2-q12 are novel findings, no single gene has been implicated in harboring prostate cancer. Frequent inactivation of PTEN/MMAC1 tumor suppressor gene at 10q23, MXI-1 at 10q25, KAI-1 at 11p11.2, Rb at 13q14.2, and p53 at 17p13.1 and deregulation of c-myc oncogene at 8q24 have recently been the subject of intense scrutiny and debate.

A simple procedure for rehybridization of nuclei analyzed previously by fish

We present a simple procedure for interphase fluorescence in situ rehybridization (FISH). This procedure was used to evaluate fresh prostate tumor from needle biopsy specimens. Digoxigenin-labeled DNA probes were hybridized onto nuclei which had been previously investigated by FISH using biotin-labeled DNA probes. This method makes it possible to reanalyze the same nuclei with different centromeric DNA probes and is useful in cases where a limited number of slides are available.

Comparative genomic hybridization reveals DNA copy number gains to frequently occur in human prostate cancer

BACKGROUND

Despite intensive studies over many years, there is only limited knowledge on the genetic changes underlying the development and progression of prostate cancer. No specific prostate carcinoma-related genetic event has yet been identified.

METHODS

In order to gain an overall view of regional chromosome gains and losses, comparative genomic hybridization (CGH) was used on a series of 16 prostate adenocarcinomas. Five benign prostate hyperplasia (BPH) samples were also evaluated.

RESULTS

Using CGH, chromosome alterations were observed in 81% of the prostate carcinomas analyzed. Gains of DNA copy numbers were found as the predominant imbalance, with chromosomes 3q (56%), 12q (56%), 8q (50%), Xq (50%), 4 (44%), 6q (44%), 5 (38%), 7q (38%), 9p (38%), and 13q (31%) being most frequently involved. Whereas DNA copy number gains comprised the whole chromosome or almost a whole arm of chromosomes 4, 5, 6, 9, and 13, the minimal overlapping regions on the other chromosomes were mapped to 3q25-q26, 8q21-q22, 12q13-q21, 7q31, and Xq22-q25. High-level amplifications were not found. Other chromosomes with nonrandom gains or losses of DNA sequences were discovered. The five BPH samples were found to be normal.

CONCLUSIONS

Amplification events at different chromosomal sites seem important in prostate cancer development. A new chromosome region with DNA copy number gains was identified on 12q, while other regions on 3q, 7q, 8q, and Xq were confirmed or narrowed down, indicating a possible role of known or putative protooncogenes in these regions for prostate cancer growth. Our low detection rate of DNA losses may to some part be explained by CGH immanent technical limitations.

Y chromosome enumeration in touch preparations from 42 prostate tumors by interphase fluorescence in situ hybridization analysis

A change in Y chromosome number is but one of the many cytogenetic abnormalities reported in human prostate tumors. However, reports in the literature have varied regarding the frequency of Y loss or gain, whether it is restricted to the cancerous tissue, and its relation to the biology of the disease. The most frequently used materials for analysis of Y enumeration have been metaphase spreads from short-term cell cultures of prostate tumor tissue and paraffin-embedded tissue sections. Analysis of Y chromosome number by using metaphase spreads on short-term cultures can be misleading owing to clonal cell selection during the establishment of these cultures. This may result in an incomplete representation of the loss/gain pattern in the tumor as a whole. Studies using paraffin-embedded tissue sections can be complicated by apparent chromosome loss due to nuclear truncation as a result of tumor sectioning. In an attempt to circumvent these problems, we have used touch preparations from human prostate tumors to search for Y chromosome loss. Fluorescence in situ hybridization analysis was conducted by using a whole chromosome Y paint, with an alpha-satellite chromosome 3 probe as a control, on tumor samples from 42 patients ages 40-75. The results demonstrated a gain of Y in a single prostate tumor sample, with no convincing evidence for loss of the entire Y chromosome in any of the other 41 samples examined. The results suggest that loss of the entire Y chromosome is an infrequent event in prostate cancer.

Chromosomal clues to the development of prostate tumors

BACKGROUND

Cytogenetic, molecular cytogenetic, and molecular studies of prostate cancer have revealed an enormous amount of data regarding chromosomal loci that are aberrant in prostate tumors.

METHODS

These data have been compared and condensed in this review to determine which chromosomes and chromosome sites have been most frequently reported.

RESULTS

Loss of the Y chromosome, gain of 7, 8, and X, and interstitial deletions on 6q, 7q, 8p, 10q, 13q, 16q, 17q, and 18q are the most prevalent.

CONCLUSIONS

A potential model for genetic control of tumor progression is presented, as are data regarding the evaluation of a new series of tumors.

Numerical chromosomal anomalies in latent adenocarcinomas of the prostate

BACKGROUND

Even the high incidence of clinically diagnosed prostate cancer is exceeded by the frequency of tumors detected at autopsy. However, there is some debate concerning the malignant potential of these so-called "latent prostate cancers." In this study, prostate cancers detected at autopsy were investigated for the presence of numerical aberrations of chromosomes 7, 10, 17, X, and Y.

METHODS

Prostates from 57 autopsies, performed on male patients aged 45 years or older, were histologically investigated for the presence of cancer. Interphase cytogenetics, an in situ hybridization method with chromosome-specific probes, was performed on paraffin sections.

RESULTS

Of the 57 specimens investigated, 23 contained foci of prostate cancer. Three prostates contained more than one tumor focus. Interphase cytogenetics could be performed successfully in 19 specimens. Of the 22 tumor foci investigated, 14 were disomic and 8 were nondisomic for the five chromosomes tested. Ploidy correlated significantly with the presence of a Gleason score of 7 or higher (P = 0.0109), but not with a tumor volume larger than 0.5 cm3, or with patient age over 75 years.

CONCLUSIONS

Some latent prostate cancers display a nondisomic chromosomal status and a low histologic differentiation in spite of a small tumor volume, suggesting a more aggressive potential in a subset of these tumors.

S-phase fraction related to prognosis in localised prostate cancer. No specific significance of chromosome 7 gain or deletion of 7q31.1

A flow-cytometric (FCM) and fluorescence in situ hybridization (FISH) study was performed in 153 patients with clinically localised prostate cancer (PC) to evaluate retrospectively the prognostic significance of DNA ploidy, S-phase fraction (SPF) and chromosome 7 copy number. Deletions in 7q31.1 were analysed in a subset of 26 tumours. The mean follow-up time was 6 years (range 4-16 years). Twelve cases of benign prostatic hyperplasia (BPH) were studied as a control. Chromosome 7 enumeration and deletion studies were conducted using the alpha-satellite D7Z1 probe and a cosmid probe specific for the marker D7S522 on 7q31.1. Higher SPF was associated with shorter overall survival and shorter time to local progression and metastasis. Near diploid (DNA index 1.05-1.20) cases had a lower frequency of metastases and lower Gleason scores than aneuploid cases. Increased absolute chromosome 7 copy number (centromere count) was associated with higher Gleason score, higher SPF and shorter local progression-free and prostate cancer survival. Absolute chromosome 7 copy number was concordant with FCM DNA ploidy in the majority (75%) of cases. Relative gain or loss of chromosome 7 (centromere counts compared to ploidy) was infrequent, and no correlation was found with clinical parameters. Deletions in 7q31.1 were infrequent. Our results indicate that in localised PC (i) SPF is a prognostic factor, (ii) absolute chromosome 7 copy number is concordant with the ploidy status of the tumour (relative gain or loss of chromosome 7 is infrequent and has no independent prognostic value) and (iii) the frequency of deletions in 7q31.1 is low and not correlated with clinical outcome.

Independent origin of multiple foci of prostatic intraepithelial neoplasia: comparison with matched foci of prostate carcinoma

BACKGROUND

Prostate carcinoma usually is heterogeneous and multifocal, with diverse clinical and morphologic manifestations. Understanding of the molecular basis for this heterogeneity is limited, particularly for the putative precursor, high grade prostatic intraepithelial neoplasia (PIN). In this study, the authors attempted to determine the genetic relation between multiple foci of PIN and matched foci of carcinoma, and whether they are independent in origin.

METHODS

The distribution and prevalence of allelic imbalance at 6 microsatellite polymorphic markers on chromosomes 7q, 8p, 8q, and 18q were examined in 84 microscopically excised PIN foci (mean, 1.6 foci/case) and 95 foci of prostate carcinoma (mean, 1.8 foci/case) from 52 completely embedded, mapped whole mount prostates.

RESULTS

PIN contained a lower overall proportion of allelic imbalance than matched prostate carcinoma foci for the 6 polymorphic microsatellite markers (65% vs. 82%), but this difference was not significant. The rate of allelic imbalance in PIN was similar to that in prostate carcinoma at 5 of 6 loci studied; the exception, D18S34 (18q12.2-12.3), had a significantly lower rate of allelic imbalance in PIN than in prostate carcinoma (19% vs. 52%), suggesting that genetic alterations in this chromosomal region may be important in carcinogenesis. Of 22 cases with allelic imbalance in at least 1 focus of PIN and 1 focus of prostate carcinoma, 21 informative cases (95%) showed a similar pattern of allelic imbalance at > or = 1 markers in the matched PIN and prostate carcinoma foci. Significant genetic heterogeneity was observed in both PIN and prostate carcinoma. Allelic imbalance was observed in at least 1 focus in 11 of 25 cases with multiple foci of PIN (44%) and 20 of 25 cases with multiple foci of prostate carcinoma (80%). There was no significant correlation between allelic imbalance and pathologic stage or tumor grade.

CONCLUSIONS

Our findings indicate that multiple foci of PIN arise independently within the same prostate. This observation suggests that a field effect underlies prostatic neoplasia. Multiple foci of prostate carcinoma also often arise independently, lending additional support for this hypothesis. The strong genetic similarities between PIN and prostate carcinoma strongly suggest that evolution and clonal expansion of PIN may account for the multifocal etiology of carcinomas.

Chromosome 7 abnormalities in prostate cancer detected by dual-color fluorescence in situ hybridization

Aneusomy of chromosome 7 and loss at 7q (especially 7q31.1) have been reported in prostate cancer. To further investigate abnormalities of 7q and the relationship with whole chromosome 7 changes, we have conducted a dual-color fluorescence in situ hybridization (FISH) analysis on isolated nuclei from 28 primary prostate cancers. A pericentromeric probe for chromosome 7, five newly isolated sequence-specific bacterial artificial chromosome (BAC) probes from 7q31.1, and one BAC for the epidermal growth factor receptor (EGFR) gene at 7p12 were used in dual color hybridizations. Pericentromeric probes for chromosomes X and 4 were also used as controls. Sixteen (57.1%) of the 28 tumors showed clonal aberrations. Nine of them were trisomy 7 and four were hypertetrasomy for chromosome 7. Deletions at 7q31.1 were found in two of the high grade tumors. With the exception of these two cases, all other cases showed concordant results using all probes. These findings confirm previous studies that aneusomy of 7 is associated with prostate cancer progression, and there may be a tumor suppressor gene (TSG) at 7q31.1 which is associated with tumor progression. In addition, our study indicates: (1) the deletion pattern of individual nuclei infers that deletions at 7q31.1 precede reduplications of chromosome 7; and (2) the amplification of EGFR was not detected at the DNA level, suggesting that activation of this oncogene may play a minor role in prostate cancer.

E1A transformed normal human prostate epithelial cells contain a 16q deletion

The difficulty of maintaining long-term prostate cell cultures has hindered the development of essential models for understanding prostate cancer. We report here the establishment of two 12S E1A transformed non-tumorigenic prostate epithelial cell strains, and their characterization. The two clonal cell strains, TP2 and TP4, proliferated for approximately 40 passages before senescence. Both exhibited a strong dependence on exogenous peptide growth factors and an immunophenotype characteristic of their prostate epithelial origin. Cytogenetic analysis revealed a consistent deletion on the q arm of chromosome 16 in TP2 with an otherwise normal karyotype. Band-specific microdissection generated region-specific probes from 16q23, which when used in fluorescence in situ hybridization (FISH) revealed that the region was deleted in 83% of metaphases analyzed. By cytogenetic analysis and FISH, the q arm of 16 was found deleted from the genome of TP4 in 60% of cells analyzed. Lost sequences on 16q-16q23 in particular--in prostate cancer have been observed by a variety of methods. Localization of common region of deletion has been determined from these studies to be distal to 16q23. Our findings suggest that 16q23 may be of major importance in the development of prostate cancer, and may harbor tumor suppressor elements.

Cytogenetic analysis of 39 prostate carcinomas and evaluation of short-term tissue culture techniques

Karyotypic analysis was performed on 102 prostate cancer specimens which were obtained through radical prostatectomy, transurethral resection, or regional lymph node dissection. Short term tissue culture was applied in all cases. Of the media and growth factors evaluated, F12/DMEM, supplemented with 2% fetal calf serum, insulin, epidermal growth factor, hydrocortisone, and cholera toxin produced the largest increase of in vitro proliferation. Such in vitro cultured cells were all phenotypically acinar epithelial cells, the supposed targets for neoplastic transformation. Stromal cell growth appeared to be completely suppressed. Of the three culture techniques investigated, the method developed in Lund, Sweden, was the most successful: 11/15 cultures yielded metaphases and, in three of these, clonal aberrations were identified. All 39 karyotypes obtained essentially had a 46,XY karyotype with clonal aberrations (eight cases) and/or nonclonal aberrations (30 cases). Clonal structural aberrations involved 2p, 3q, 11p, 17p, and 21q. The clonal numerical aberrations found were: + 8, + dmin, and -Y. The most frequently observed nonclonal aberrations were 8p deletions (five cases) and loss of 6, 7, 8, 15, 17, 18, 21, and/or Y (> or = five cases). In summary, clonal aberrations were observed in 20% of the evaluable PC cell cultures, and nonclonal aberrations in 77%. So, although diploid cells without clonal abnormalities still had a growth advantage, under optimal conditions PC cells were able to proliferate in primary in vitro culture.

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.

HER-2/neu gene amplification status in prostate cancer by fluorescence in situ hybridization

HER-2/neu expression has been established as a prognostic factor in breast and other cancers. In prostate cancer (PC), a similar predictive role has been hindered by variable immunohistochemical (IHC) results. The authors studied DNA amplification of the HER-2/neu gene on 4-microm sections obtained from 62 formalin-fixed, paraffin-embedded PCs by fluorescence in situ hybridization (FISH). The results were compared with HER-2/neu protein expression as determined by IHC and correlated by logistic regression analysis with Gleason tumor grade, DNA ploidy, serum prostate specific antigen (PSA), and pathological stage. The HER-2/neu gene was localized using the Oncor (Gaithersburg, MD) digoxigenin-labeled unique sequence probe. Amplified PCs had at least 20 malignant cells, with 5 or more copies of the sequence. Amplification of HER-2/neu correlated with Gleason score (P = .0001). The mean Gleason score of unamplified tumors was 5.7 and that of amplified tumors was 7.5. Nondiploid tumors had a significantly greater rate of HER-2/neu amplification compared with diploid tumors (P = .0003). Of the 62 cases evaluated by IHC and FISH, 18 cases (29%) were overexpressed by IHC, and 27 cases (44%) were amplified by FISH. A trend for similar HER-2/neu status in each PC by the two methods did not reach statistical significance (P = .23). HER-2/neu amplification by FISH was associated with advanced pathological stage; however, this relationship reached only near-statistical significance (P = .06). There was no correlation of HER-2/neu amplification by FISH with patient age or preoperative serum PSA levels. The authors conclude that HER-2/neu gene amplification status can be determined by FISH on archival prostate cancer specimens, significantly correlates with high tumor grade and nondiploid DNA content, and is more frequently encountered in tumors with advanced pathological stage. Also, FISH is more sensitive than IHC for detection of abnormalities in the HER-2/neu gene, and further studies should be undertaken to determine whether a FISH-based HER-2/neu detection method may prove of importance in the prediction of prognosis and planning of therapy in prostate cancer patients.

Cytogenetic studies in prostate cancer: are we making progress?

Prostate cancer is the most commonly diagnosed male malignancy in western countries. Recent work in cell biology and molecular cytogenetics has led to a large amount of data on chromosomal abnormalities in prostatic tumors. A highlight of the literature describing both classical and molecular cytogenetic studies of prostate cancer is presented. By conventional cytogenetics, predominant changes included gain of chromosome 7, loss of Y, deletions of 7q and 10q, and the appearance of double minutes. Using fluorescence in situ hybridization, predominant changes included gains of chromosomes 1, 7, 8, 8q sequences, 17, X and Y, and loss of chromosomes 1, 7, 8, 8p sequences, 10, 10q, 16q and 17q sequences, 17 and Y. Newly defined sites by comparative genomic hybridization included loss of genetic material on 2q, 5q, 6q, 9q, 13q, 15q, 17p, and 18q, and gains at 1q, 2p, 3q, 7q, 9q, 11p, 16p, 20, 22, and X. These data indicate that multiple non-random genomic sites are involved in prostate tumorigenesis. This wide and relatively recent gain of information is likely to provide key clues to the biologic basis of this disease.

Interphase cytogenetics of prostate cancer: fluorescence in situ hybridisation (FISH) analysis of Japanese cases

No numerical aberration of chromosomes that might be specific for prostate cancer has so far been established. We used fluorescence in situ hybridisation (FISH) with centromere-specific probes for chromosomes 7, 8, 17, X and Y to establish the distribution of centromere copy numbers in frozen-stored or freshly prepared samples of benign prostate hypertrophy (BPH) and to detect numerical aberrations of these chromosomes in 28 prostate cancers from Japanese men. There was no significant difference in the data of centromere copy numbers between fresh and frozen-stored tissue. The most common aberration in prostate cancers was a gain of chromosome 8 (57%), with numerical aberration of chromosome 7 being the second most frequent anomaly (50%). Numerical aberration of chromosome 7 is most significantly associated with a higher Gleason score (GS) (P < 0.005) or with lymph node metastasis (P < 0.001). Numerical aberration of several chromosomes, including chromosomes 7 and/or 8, was common in aggressive prostate cancers. Loss of chromosome Y was detected in only 4% of cases. FISH analysis thus proved to be a useful method for detecting numerical aberrations of individual chromosomes, with application to touch preparations of frozen-stored tissue having the advantage of exact sampling of cancer foci. The results suggest that numerical aberration of chromosome 7 is associated with aggressive tumour behaviour and poor prognosis of patients with prostate cancer. The association between genetic change and chromosomal abnormality should be studied in detail.

Metaphase analysis of metanephric adenoma reveals chromosome Y loss with chromosome 7 and 17 gain

A 61-year-old man underwent wedge excision of a 3-cm right renal metanephric adenoma. This recently recognized tumor has been considered benign, although no genetic studies have been reported. Metaphase analysis demonstrated a 47,X,-Y,+7,+17 karyotype. These results are consistent with a clonal neoplastic disorder.

Molecular biology of prostatic intraepithelial neoplasia

High-grade PIN is the most likely precursor of prostatic adenocarcinoma, according to virtually all available evidence to date. The clinical importance of recognizing PIN is based on its strong association with prostatic carcinoma. PIN has a high predictive value as a marker for adenocarcinoma. Its identification in biopsy specimens of the prostate warrants further search for concurrent invasive carcinoma. PIN is associated with progressive abnormalities of phenotype and genotype intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. There is progressive gain or loss of a wide variety of biomarkers, including morphometric markers, differentiation markers, stromal markers, growth factors and associated receptors, oncogenes, tumor suppressor genes, and chromosomes. Abnormalities in expression of most biomarkers are amplified in the progression from high-grade PIN to localized cancer, metastatic cancer, and hormone-refractory cancer. Oncogenesis of prostatic carcinoma probably occurs through the selection of several genetic changes, each modifying the expression or function of genes controlling cell growth and differentiation. Further studies are needed to evaluate the function and prognostic value of oncogene expression in the normal, preneoplastic, and neoplastic prostate.

Evidence for somatic pairing of chromosome 7 and 10 homologs in a follicular lymphoma

Fluorescence in situ hybridization using centromeric probes for chromosomes 7 and 10 in a follicular lymphoma revealed only one signal in about 40% of interphases, whereas two copies of each chromosome were consistently seen in metaphases. In four out of 18 metaphases both copies of chromosome 7 were situated close to one another. In contrast, two signals for chromosome 1 were seen in 94% of interphases, consistent with observations on metaphases. The findings suggest chromosome-specific somatic pairing, the functional significance of which is at present unknown, and reinforce previous evidence suggesting that care should be taken in the interpretation of interphase signal numbers using centromeric probes in neoplastic as well as normal material.