Genetic changes in clinically organ-confined prostate cancer by comparative genomic hybridization

High B7-H3 expression is linked to increased risk of prostate cancer progression

B7-H3 is a member of the B7 superfamily of immune checkpoint molecules. B7-H3 up regulation has been linked to cancer development and progression in many tumors including prostate cancer. To clarify the potential utility of B7-H3 as a prognostic biomarker, B7-H3 expression was analyzed by immunohistochemistry in more than 17 000 prostate cancers. Normal prostatic glands were largely B7-H3 negative, while membranous B7-H3 immunostaining was seen in 47.0% of analyzed cancers. B7-H3 immunostaining was weak in 12.3%, moderate in 21.1% and strong in 13.5% of cases. High B7-H3 expression was associated with pT, Gleason score, lymph node metastasis, high Ki67 labeling index and early prostate-specific antigen recurrence (P < 0.0001 each). High B7-H3 expression was also linked to high androgen receptor expression and TMPRSS2:V-ets avian erythroblastosis virus E26 oncogene homolog (ERG) fusions (P < 0.0001 each). Multivariate analyses showed a strong independent prognostic impact of high B7-H3 expression in all cancers and in the ERG negative subgroup. Comparison with previously analyzed frequent chromosomal deletions revealed a close association with Phosphatase and Tensin Homolog deletions. Analysis of B7-H3, alone or in combination with other markers, might be of clinical utility, especially in the subgroup of ERG negative prostate cancers.

High-level expression of protein tyrosine phosphatase non-receptor 12 is a strong and independent predictor of poor prognosis in prostate cancer

BACKGROUND

Protein tyrosine phosphatase non-receptor 12 (PTPN12) is ubiquitously tyrosine phosphatase with tumor suppressive properties.

METHODS

PTPN12 expression was analyzed by immunohistochemistry on a tissue microarray with 13,660 clinical prostate cancer specimens.

RESULTS

PTPN12 staining was typically absent or weak in normal prostatic epithelium but seen in the majority of cancers, where staining was considered weak in 26.5%, moderate in 39.9%, and strong in 4.7%. High PTPN12 staining was associated with high pT category, high classical and quantitative Gleason grade, lymph node metastasis, positive surgical margin, high Ki67 labeling index and early prostate specific antigen recurrence (p < 0.0001 each). PTPN12 staining was seen in 86.4% of TMPRSS2:ERG fusion positive but in only 58.4% of ERG negative cancers. Subset analyses discovered that all associations with unfavorable phenotype and prognosis were markedly stronger in ERG positive than in ERG negative cancers but still retained in the latter group. Multivariate analyses revealed an independent prognostic impact of high PTPN12 expression in all cancers and in the ERG negative subgroup and to a lesser extent also in ERG positive cancers. Comparison with 12 previously analyzed chromosomal deletions revealed that high PTPN12 expression was significantly associated with 10 of 12 deletions in ERG negative and with 7 of 12 deletions in ERG positive cancers (p < 0.05 each) indicating that PTPN12 overexpression parallels increased genomic instability in prostate cancer.

CONCLUSIONS

These data identify PTPN12 as an independent prognostic marker in prostate cancer. PTPN12 analysis, either alone or in combination with other biomarkers might be of clinical utility in assessing prostate cancer aggressiveness.

Identification of FBXL4 as a Metastasis Associated Gene in Prostate Cancer

Prostate cancer is the most common cancer among western men, with a significant mortality and morbidity reported for advanced metastatic disease. Current understanding of metastatic disease is limited due to difficulty of sampling as prostate cancer mainly metastasizes to bone. By analysing prostate cancer bone metastases using high density microarrays, we found a common genomic copy number loss at 6q16.1-16.2, containing the FBXL4 gene, which was confirmed in larger series of bone metastases by fluorescence in situ hybridisation (FISH). Loss of FBXL4 was also detected in primary tumours and it was highly associated with prognostic factors including high Gleason score, clinical stage, prostate-specific antigen (PSA) and extent of disease, as well as poor patient survival, suggesting that FBXL4 loss contributes to prostate cancer progression. We also demonstrated that FBXL4 deletion is detectable in circulating tumour cells (CTCs), making it a potential prognostic biomarker by 'liquid biopsy'. In vitro analysis showed that FBXL4 plays a role in regulating the migration and invasion of prostate cancer cells. FBXL4 potentially controls cancer metastasis through regulation of ERLEC1 levels. Therefore, FBXL4 could be a potential novel prostate cancer suppressor gene, which may prevent cancer progression and metastasis through controlling cell invasion.

Chromosome 8p deletions and 8q gains are associated with tumor progression and poor prognosis in prostate cancer

PURPOSE

Deletions of 8p and gains of 8q belong to the most frequent cytogenetic alterations in prostate cancer. The target genes of these alterations and their biological significance are unknown.

EXPERIMENTAL DESIGN

To determine the relationship between chromosome 8 changes, and prostate cancer phenotype and prognosis, a set of 1.954 fully annotated prostate cancers were analyzed in a tissue microarray format by fluorescence in situ hybridization.

RESULTS

Both 8p deletions and 8q gains increased in number during different stages of prostate cancer progression. 8p deletions/8q gains were found in 26.1%/4.8% of 1,239 pT(2) cancers, 38.5%/9.8% of 379 pT(3a) cancers, 43.5%/8.9% of 237 pT(3b) cancers, 40.7%/14.8% of 27 pT(4) cancers, 39.1%/34.8% of 23 nodal metastases, 51.9%/33.3% of 27 bone metastases, and 45.5%/59.9% of 22 hormone refractory cancers (P < 0.0001 each). Both 8p deletions and 8q gains were also significantly associated with high Gleason grade and with each other (P < 0.0001 each). In primary tumors, 8p deletions were seen in only 27.3% of 1,882 cancers without 8q gain but in 57.4% of 122 tumors with 8q gain (P < 0.0001). Among cancers treated with radical prostatectomy, 8p deletions (P = 0.003) and 8q gains (P = 0.02) were associated with biochemical tumor recurrence. However, multivariate analysis (including prostate-specific antigen, pT/pN stage, Gleason score, and surgical margin status) did not reveal any statistically independent effect of 8p or 8q alterations on biochemical tumor recurrence.

CONCLUSIONS

8p deletions and 8q gains are relatively rare in early stage prostate cancer but often develop during tumor progression. The prognostic effect does not seem to be strong enough to warrant clinical application.

DNA copy number alterations in prostate cancers: a combined analysis of published CGH studies

BACKGROUND

Identifying genomic regions that are commonly deleted or gained in neoplastic cells is an important approach to identify tumor suppressor genes and oncogenes. Studies in the last two decades have identified a number of common DNA copy number alterations in prostate cancer. However, because of various sample sizes, diverse tumor types and sources, as well as a variety of detection methods with various sensitivities and resolutions, it is difficult to summarize and fully interpret the overall results.

METHODS

We performed a combined analysis of all published comparative genomic hybridization (CGH) studies of prostate cancer and estimated the frequency of alterations across the genome for all tumors, as well as in advanced and localized tumors separately. A total of 41 studies examining 872 cancers were included in this study.

RESULTS

The frequency of deletions and gains were estimated in all tumors, as well as in advanced and localized tumors. Eight deleted and five gained regions were found in more than 10% of the prostate tumors. An additional six regions were commonly deleted and seven were commonly gained in advanced tumors. While 8p was the most common location of deletion, occurring in about a third of all tumors and about half of advanced tumors, 8q was the most commonly gained region, affecting about a quarter of all tumors and about half of all advanced tumors.

CONCLUSIONS

The large number of tumors examined in this combined analysis provides better estimates of the frequency of specific alterations in the prostate cancer cell genome, and offers important clues for prioritizing efforts to identify tumor suppressor genes and oncogenes in these altered regions.

Gain of chromosome X in prostatic atrophy detected by CGH and FISH analyses

BACKGROUND

Focal atrophy is presumed to be an indirect forerunner of prostate cancer. The aim of this study was to examine genetic alterations in prostate epithelia deriving from atrophic areas and compare these findings with those of cells deriving from paired prostate cancer in the same patient.

METHODS

Formalin fixed paraffin wax-embedded prostatectomy specimens from 20 prostate cancer patients were utilized in this study. Comparative Genomic Hybridization (CGH) was performed on atrophic areas. To validate the CGH results, Fluorescence in Situ Hybridization (FISH) analysis was performed on atrophic areas and paired cancer tissue.

RESULTS

Gain of the whole chromosome X was found as sole aberration in seven (70%) atrophic tissues by CGH. A gain of centromere X was observed in 13 (68.4%) atrophic areas and in 18 (90%) cancer tissues using FISH.

CONCLUSIONS

Our investigation reconfirms the genetical instability of cells of the atrophic acini and attention of relevance of gain of chromosome X in atrophic areas.

Genome-wide analysis of allelic imbalance in prostate cancer using the Affymetrix 50K SNP mapping array

Prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer in male subjects in Western countries. The widespread use of prostate-specific antigen (PSA) has increased the detection of this cancer form in earlier stages. Moreover, it has increased the need for new diagnostic procedures to be developed for patient stratification based on risk of progression. We analysed laser-microdissected prostate tumour tissue from 43 patients with histologically verified PCa, using the new high-resolution Affymetrix Mapping 50K single-nucleotide polymorphism array. The results showed six major loss of heterozygosity regions at chromosomes 6q14-16, 8p23-11, 10q23, 13q13-21 and 16q21-24 and a novel region at chromosome 21q22.2, all of which reveal concomitant copy number loss. Tumour development was further characterised by numerous novel genomic regions almost exclusively showing copy number loss. However, tumour progression towards a metastatic stage, as well as poor differentiation, was identified by specific patterns of copy number gains of genomic regions located at chromosomes 8q, 1q, 3q and 7q. Androgen ablation therapy was further characterised by copy gain at chromosomes 2p and 10q. In conclusion, patterns of allelic imbalance were discovered in PCa, consisting allelic loss as an early event in tumour development, and distinct patterns of allelic amplification related to tumour progression and poor differentiation.

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.

The impact of genomic alterations on the transcriptome: a prostate cancer cell line case study

Genetic instability may lead to the loss/gain of transcriptional control. Here we investigated the effect of genomic instability, that is loss/gain of chromosomal regions on the global transcriptome of prostate cancer cell line DU145. The genomic loss/gain map obtained through BAC array-based CGH was superimposed on the dynamic transcriptome of DU145 cells treated with serum for 0 h (serum starved), 2 h and 12 h. The genomic analysis suggested that in DU145 cells: (1) chromosomal gains are prominent than losses and (2) copy number changes are associated with chromosome-specific and dynamic gene expression regulatory mechanisms. A significant proportion of the genes in the stable regions of the chromosome were up-regulated whereas a higher proportion of genes were down-regulated at 2 and 12 h in the deleted regions of the chromosomes following serum treatment. No change in expression was observed for the genes in the gained regions over a period of time. This analysis led us to propose that loss of heterozygosity leads to an overall transcriptional down-regulation that may further lead to a decrease in the expression of putative tumor suppressors. The genomic profile of DU145 is similar to pathological specimens of prostate cancer, hence the genomic/transcriptomic signature of DU145 can be used to understand the pathology of prostate cancer. It is expected that this analysis will allow a better understanding of transcriptional regulatory mechanisms in the context of genomic loss and gain and may lead to the discovery of novel oncogenes and tumor suppressors and the underlying regulatory pathways.

8q Gain Is an Independent Predictor of Poor Survival in Diagnostic Needle Biopsies from Prostate Cancer Suspects

PURPOSE

The main procedure to confirm a suspected diagnosis of prostate cancer is histologic analysis of ultrasound-guided sextant prostate biopsies. As it is difficult to reliably assess tumor stage and grade in such minute samples, the clinical significance of some tumor foci remains unclear. Genetic markers that could augment pretreatment prognostic information would improve the clinical management of the disease.

EXPERIMENTAL DESIGN

We have analyzed by comparative genomic hybridization a consecutive series of prostate needle biopsies obtained prospectively from 100 prostate cancer suspects. For 25 of these patients, a second independent biopsy core was analyzed to assess possible tumor heterogeneity. Additionally, a three-color fluorescent in situ hybridization assay was done in paraffin-embedded biopsy cores to validate the comparative genomic hybridization findings and to confirm their prognostic value.

RESULTS

Sixty-one of 100 biopsy samples had morphologic evidence of prostate cancer and 41 (67%) of these displayed genomic copy number changes as opposed to none of the morphologically normal biopsies. The presence of losses, amplifications, and the total number of genomic imbalances were significantly associated with poorly differentiated tumors. Kaplan-Meier curves with log-rank test showed that patients whose tumors displayed 8q gains had a significantly worse survival even when tumor grade was taken into account (P = 0.008). Restricting the analysis to cases with Gleason score 7, the most troublesome category in terms of prognostic information, gains at 8q were still significantly associated with poor survival (P = 0.011), something that was confirmed by fluorescent in situ hybridization in an independent series of biopsies with much longer follow-up time (P = 0.023).

CONCLUSIONS

We show that whole genomic information can be obtained from minute needle biopsies of prostate cancer suspects and that genetic data can provide additional prognostic information before a therapeutic decision is taken.

Statistical dissection of genetic pathways involved in prostate carcinogenesis

Molecular markers that could stratify prostate cancer patients according to risk of disease progression would allow a significant improvement in the management of this clinically heterogeneous disease. In the present study, we analyzed the genetic profile of a consecutive series of 51 clinically confined prostate carcinomas and 27 benign prostatic hyperplasias using comparative genomic hybridization (CGH). We then added our findings to the existing literature data in order to perform a meta-analysis on a total of 294 prostate cancers with detailed CGH and clinicopathological information, using multivariate statistical methods that included principal component, hierarchical clustering, time of occurrence, and regression analyses. Whereas several genomic imbalances were shared by organ-confined, locally invasive, and metastatic prostate cancers, 6q and 10q losses and 7q and 8q gains were significantly more frequent in patients with extra-prostatic disease. Regression analysis indicated that 8q gain and 13q loss were the best predictors of locally invasive disease, whereas 8q gain and 6q and 10q losses were associated with metastatic disease. We propose a genetic pathway of prostate carcinogenesis with two distinct initiating events, namely, 8p and 13q losses. These primary imbalances are then preferentially followed by 8q gain and 6q, 16q, and 18q losses, which in turn are followed by a set of late events that make recurrent and metastatic prostate cancers genetically more complex. We conclude that significant differences exist in the genetic profile of organ-confined, locally invasive, and advanced prostate cancer and that genetic features may carry prognostic information independently of Gleason grade.

Evidence for gains at 15q and 20q in brain metastases of prostate cancer

Many detailed genetic studies have been reported on prostate carcinogenesis. A major shortcoming of these studies, however, is the fact that most data have been gained from investigations that were performed at a single point of time during tumor development. Only little is known on the dynamic process of genetic changes during the course of the disease. We performed comparative genomic hybridization in two cases of prostate cancer brain metastases. Tissue samples from the primary tumors, the locally recurrent tumor in one case, and the brain metastases from both cases were available for analysis. The number of chromosome abnormalities was found to be increased in the metastases. This contrasts to a remarkably stable chromosome composition of the primary tumor over several years, even in an androgen-depleted environment. When focusing on these changes, which either emerged as new common aberrations in both brain metastases, or which were commonly present in the primary and metastatic tumors, we were able to delineate five chromosomal sites that are assumed to be related to prostate cancer metastasis: 8q21 approximately q22, 8q24, 15q24 approximately q26, 20q12 approximately q13.1, and Xq12 approximately q21. These findings provide new evidence for a putative role of genes at 15q and 20q in the metastatic process of prostate cancer.

DNA sequence copy number aberrations in prostate cancers: a comparison of comparative genomic hybridization data between Japan and European countries

Incidence of prostate cancer in Japan and resultant mortality rates are lower than in Western countries. To elucidate the reasons behind this, the genetic characteristics of prostate cancer in Japanese patients were investigated. Comparative genomic hybridization was applied in 27 cases of prostate cancers in Japanese patients. Frequent gains were found at Xq, 8q, Xp, and 7q and frequent losses at 8p, 6q, 2q, 16q, and 17p (in decreasing order of frequency). Loss of 6q was frequently detected in both early and advanced tumors. Gains of 7q and 8q and loss of 8p were more frequent in advanced than early tumors. The frequency of 13q loss in primary tumors was significantly lower in patients in Japan than in European countries. These data suggest that a loss of 6q is associated with the development of prostate cancer, and that gains of 7q and 8q and a loss of 8p are linked with cancer progression. The frequency of 13q loss may imply differences in biological behavior of prostate cancer between Japan and Western countries.

Novel perspective: focusing on the X chromosome in reproductive cancers

In an XX female, one of the two X chromosomes has been inactivated during early embryonic life to achieve a compensation of X-linked gene products between males and females, leaving only one allele of X-linked genes functional. There are some X-linked genes escaping the X-inactivation, i.e., being expressed from both alleles. Escape from X-inactivation varies at different levels; some genes have both alleles active in some women but only one allele active in others, whereas some other genes have both alleles active in neoplastic tissue but only one allele active normally. The X-inactivation may be considered functionally equivalent to a loss of heterozygosity (LOH) for some genes, whereas escape from X-inactivation may be equivalent to functional gene amplification for others. The physiological LOH may make X-linked tumor suppressor genes lose their function more easily, compared with autosomal tumor suppressor genes, thus predisposing women to cancer formation more easily. Moreover, the human X chromosome contains many genes related to cancer or to sex and reproduction. All these properties of the X chromosome suggest that it may play more important roles than any autosomal chromosome in the development and progression of reproductive and urologic cancers.

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.

High-resolution analysis of paraffin-embedded and formalin-fixed prostate tumors using comparative genomic hybridization to genomic microarrays

We have used prostate cancer, the most commonly diagnosed noncutaneous neoplasm among men, to investigate the feasibility of performing genomic array analyses of archival tissue. Prostate-specific antigen and a biopsy Gleason grade have not proven to be accurate in predicting clinical outcome, yet they remain the only accepted biomarkers for prostate cancer. It is likely that distinct spectra of genomic alterations underlie these phenotypic differences, and that once identified, may be used to differentiate between indolent and aggressive tumors. Array comparative genomic hybridization allows quantitative detection and mapping of copy number aberrations in tumors and subsequent associations to be made with clinical outcome. Archived tissues are needed to have patients with sufficient clinical follow-up. In this report, 20 formalin-fixed and paraffin-embedded prostate cancer samples originating from 1986 to 1996 were studied. We present a straightforward protocol and demonstrate the utility of archived tissue for array comparative genomic hybridization with a 2400 element BAC array that provides high-resolution detection of both deletions and amplifications.

Defining the region(s) of deletion at 6q16-q22 in human prostate cancer

Deletion of the long arm of chromosome 6 (6q) frequently occurs in many neoplasms, including carcinomas of the prostate and breast and melanoma, suggesting the location of a tumor-suppressor gene or genes at 6q. At present, however, the region of deletion has not been well defined, and the target gene of deletion remains to be identified. In this study, we analyzed 44 primary prostate cancers with 16 polymorphic markers for loss of heterozygosity (LOH) by using PCR-based techniques. We also examined 23 cell lines/xenografts of prostate cancer with 38 markers for LOH by the method of homozygosity mapping of deletion. LOH at 6q16 - q22 was detected in 21 of 44 (48%) primary tumors and in 12 of 23 (52%) cell lines/xenografts. Two regions of LOH were defined. One was 7.5 cM at 6q16 - q21 between markers D6S1716 and D6S1580, and the other was 4.3 cM at 6q22 between D6S261 and D6S1702. Whereas no correlation was found between LOH at 6q16-q22 and patient age at diagnosis or Gleason score, tumors at higher stage appear to have more frequent LOH. These findings suggest that deletion of 6q16 - q22 is a frequent event in prostate cancer, and that the deletion originates from two distinct regions. These results should be useful in identifying the target gene(s) of deletion at 6q.

Decrease and gain of gene expression are equally discriminatory markers for prostate carcinoma: a gene expression analysis on total and microdissected prostate tissue

Information on over- and underexpressed genes in prostate cancer in comparison to adjacent normal tissue was sought by DNA microarray analysis. Approximately 12,600 mRNA sequences were analyzed from a total of 26 tissue samples (17 untreated prostate cancers, 9 normal adjacent to prostate cancer tissues) obtained by prostatectomy. Hierarchical clustering was performed. Expression levels of 63 genes were found significantly (at least 2.5-fold) increased, whereas expression of 153 genes was decreased (at least 2.5-fold) in prostate cancer versus adjacent normal tissue. In addition to previously described genes such as hepsin, overexpression of several genes was found that has not drawn attention before, such as the genes encoding the specific granule protein (SGP28), alpha-methyl-acyl-CoA racemase, low density lipoprotein (LDL)-phospholipase A2, and the anti-apoptotic gene PYCR1. The radiosensitivity gene ATDC and the genes encoding the DNA-binding protein inhibitor ID1 and the phospholipase inhibitor uteroglobin were significantly down-regulated in the cancer samples. DNA microarray data for eight genes were confirmed quantitatively in five normal and five cancer tissues by real-time reverse transcriptase-polymerase chain reaction with a high correlation between the two methods. Laser capture microdissection of epithelial and stromal compartments from cancer and histological normal specimens followed by an amplification protocol for low levels of RNA (<0.1 microg) allowed us to distinguish between gene expression profiles characteristic of epithelial cells and those typical of stroma. Most of the genes identified in the nonmicrodissected tumor material as up-regulated were indeed overexpressed in cancerous epithelium rather than in the stromal compartment. We conclude that development of prostate cancer is associated with down-regulation as well as up-regulation of genes that show complex differential regulation in epithelia and stroma. Some of the gene expression alterations identified in this study may prove useful in the development of novel diagnostic and therapeutic strategies.

Chromosomal changes in incidental prostatic carcinomas detected by comparative genomic hybridization

OBJECTIVES

The genetic changes underlying the development and progression of prostate cancer are poorly understood. To identify chromosomal regions in incidental prostatic carcinoma (T1a and T1b) was the primary aim of this study.

MATERIALS AND METHODS

We used comparative genomic hybridization (CGH) to search for DNA sequence copy number changes on a series of 48 T1 prostate cancer diagnosed by transurethral resection (TURP) and by adenomectomy. Incidental prostatic carcinomas have not been studied by CGH previously.

RESULTS

CGH analysis indicated that 14 cases (29.2%) of incidental prostatic carcinoma showed chromosome alterations. The most frequent alterations were chromosomal losses of 8p (10.4%), 13q (6.3%), 5q (4.2%) and 18q (4.2%), and gains of 17p (10.4%), 17q (10.4%), 9q (6.3%) and 7q (4.2%). Minimal overlapping chromosomal regions of loss, indicative for the presence of tumor suppressor genes (TSGs), were mapped to 8p22 and 13q14.1-q21.3, and minimal overlapping regions of gain, indicative for the presence of oncogenes, were found at 9q34.2-qter, 17p12 and 17q24-qter. The statistical analysis displayed a significant association between chromosomal aberration detected by CGH and high Gleason score (P < 0.005) as well as between tumor categories T1a and T1b and chromosomal imbalance (P = 0.041).

CONCLUSIONS

Studies directed at incidental prostatic carcinomas allow discovery of chromosomal changes in small and highly malignant tumors. Our results suggest that loss or gain of DNA in these regions are important in prostate cancer. This is the first study, which documents the spectrum of chromosomal changes in incidental prostatic carcinomas.

Staging in prostate cancer

This article reviews the conventional current techniques that are used for staging prostate cancer. The advantages and limitations of each modality are described. Attention is focused on the areas in which progress is rapidly being made and is likely to be developed in the future.

Genetic changes in stage pT2N0 prostate cancer studied by comparative genomic hybridization

OBJECTIVE

To identify chromosomal regions important for progression in clinically organ-confined prostate cancer, as the genetic changes underlying the development and progression of prostate cancer are poorly understood.

MATERIALS AND METHODS

Comparative genomic hybridization (CGH) was used to search for DNA sequence copy-number changes in a series of 50 primary organ-confined prostate adenocarcinomas (pT2N0) removed by radical prostatectomy.

RESULTS

CGH analysis indicated that 23 (46%) of the primary prostate adenocarcinomas showed chromosome alterations. The percentage of tumours with losses (38%) was higher than with gains (28%). Losses of 13q (24%), 8p (18%), 6q (10%), 16q (8%), 18q (6%) and 5q (6%) and gains of 17q (12%), 20q (12%), 9q (10%), 17p (8%) and 8q (6%) were the most frequent alterations. Amplifications were found at 8q24-qter. Minimal overlapping regions of loss, indicative of the presence of tumour-suppressor genes, were mapped to 13q21.1-q21.3 and 8p21.2, and minimal overlapping regions of gain, indicative of the presence of oncogenes, were found at 9q34.4-qter, 17q25-qter and 20q13.3-qter. There was a significant association between Gleason score and losses and gains (P = 0.003), and an association between chromosomal imbalance and high histological grade (P = 0.008).

CONCLUSION

These results suggest that losses or gains of DNA in these regions are important for prostate cancer progression, and document the spectrum of chromosomal alterations in stage pT2N0 of clinically organ-confined prostate cancer.

Discovery of new DNA amplification loci in prostate cancer by comparative genomic hybridization

BACKGROUND

DNA sequence amplifications are involved in the progression of many tumor types, and have also been found in advanced prostate cancer. The aim of this study was to detect new loci of DNA amplifications in prostate cancer.

METHODS

Comparative genomic hybridization (CGH) was used for whole genome screening of DNA sequence copy number alterations in 27 advanced prostate cancers.

RESULTS

The most prevalent changes were losses of 8p, 13q (52%, each), 6q (48%), 18q (37%), 5q (30%), 2q, 4q and 16q (26%, each), and gains of 8q (48%), Xq (40%), and Xp (26%). In addition, 16 high-level amplifications were found. These included Xq12 (five), 8q24 (two), and 11q13 (one) with known putative target genes (androgen receptor, MYC and Cyclin D1), and 1q21-25 (three), 10q22 (two), 17q23-24 (two), and 8q21 (one) where the target genes remain unknown.

CONCLUSIONS

High-level amplifications at different chromosomal sites occur in advanced prostate cancer. The detection of amplified chromosomal regions may serve as a starting point to discover novel oncogenes involved in prostate cancer progression.