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

STAT5A/B gene locus undergoes amplification during human prostate cancer progression

The molecular mechanisms underlying progression of prostate cancer (PCa) to castrate-resistant (CR) and metastatic disease are poorly understood. Our previous mechanistic work shows that inhibition of transcription factor Stat5 by multiple alternative methods induces extensive rapid apoptotic death of Stat5-positive PCa cells in vitro and inhibits PCa xenograft tumor growth in nude mice. Furthermore, STAT5A/B induces invasive behavior of PCa cells in vitro and in vivo, suggesting involvement of STAT5A/B in PCa progression. Nuclear STAT5A/B protein levels are increased in high-grade PCas, CR PCas, and distant metastases, and high nuclear STAT5A/B expression predicts early disease recurrence and PCa-specific death in clinical PCas. Based on these findings, STAT5A/B represents a therapeutic target protein for advanced PCa. The mechanisms underlying increased Stat5 protein levels in PCa are unclear. Herein, we demonstrate amplification at the STAT5A/B gene locus in a significant fraction of clinical PCa specimens. STAT5A/B gene amplification was more frequently found in PCas of high histologic grades and in CR distant metastases. Quantitative in situ analysis revealed that STAT5A/B gene amplification was associated with increased STAT5A/B protein expression in PCa. Functional studies showed that increased STAT5A/B copy numbers conferred growth advantage in PCa cells in vitro and as xenograft tumors in vivo. The work presented herein provides the first evidence of somatic STAT5A/B gene amplification in clinical PCas.

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.

Co-regulation analysis of closely linked genes identifies a highly recurrent gain on chromosome 17q25.3 in prostate cancer

Background

Transcriptional profiling of prostate cancer (PC) has unveiled new markers of neoplasia and allowed insights into mechanisms underlying this disease. Genomewide analyses have also identified new chromosomal abnormalities associated with PC. The combination of both classes of data for the same sample cohort might provide better criteria for identifying relevant factors involved in neoplasia. Here we describe transcriptional signatures identifying distinct normal and tumoral prostate tissue compartments, and the inference and demonstration of a new, highly recurrent copy number gain on chromosome 17q25.3.

Methods

We have applied transcriptional profiling to tumoral and non-tumoral prostate samples with relatively homogeneous epithelial representations as well as pure stromal tissue from peripheral prostate and cultured cell lines, followed by quantitative RT-PCR validations and immunohistochemical analysis. In addition, we have performed in silico colocalization analysis of co-regulated genes and validation by fluorescent in situ hybridization (FISH).

Results

The transcriptomic analysis has allowed us to identify signatures corresponding to non-tumoral luminal and tumoral epithelium, basal epithelial cells, and prostate stromal tissue. In addition, in silico analysis of co-regulated expression of physically linked genes has allowed us to predict the occurrence of a copy number gain at chromosomal region 17q25.3. This computational inference was validated by fluorescent in situ hybridization, which showed gains in this region in over 65% of primary and metastatic tumoral samples.

Conclusion

Our approach permits to directly link gene copy number variations with transcript co-regulation in association with neoplastic states. Therefore, transcriptomic studies of carefully selected samples can unveil new diagnostic markers and transcriptional signatures highly specific of PC, and lead to the discovery of novel genomic abnormalities that may provide additional insights into the causes and mechanisms of prostate cancer.

Chromosomal imbalances, loss of heterozygosity, and immunohistochemical expression of TP53, RB1, and PTEN in intraductal cancer, intraepithelial neoplasia, and invasive adenocarcinoma of the prostate

Recent studies have shown that intraductal prostate carcinoma (IDC-P) should be considered as a separate lesion distinct from prostatic intraepithelial neoplasia (PIN). The purpose of the present study was to analyze the genetic relationship between benign prostatic tissue, PIN, invasive cancer, IDC-P, and extracapsular tumor tissue to get further information about the role of IDC-P in the development of prostate cancer. One hundred five radical prostatectomy specimens were investigated immunohistochemically, 77 cases were analyzed by PCR for LOH of the tumor suppressor genes TP53 and RB1, and 11 cases of IDC-P and 10 cases of PIN were investigated using comparative genomic hybridization (CGH). At CGH analysis, IDC-P showed several chromosomal imbalances in contrast to PIN, where no changes were found. We could demonstrate a significant increase of LOH for TP53 or RB1 from benign tissue to PIN. LOH of both TP53 and RB1 were frequently found in IDC-P (52%), followed by extracapsular tumor tissue (44%), invasive cancer (24%), PIN (19%), and benign prostatic tissue (17%). Increased immunohistochemical expression was found in invasive cancer for TP53, RB1, and for PTEN. Decreased expression could be demonstrated in extracapsular tumor tissue and in IDC-P. Our results indicate that IDC-P in general follows the genetic pathway from normal epithelium over PIN lesion. IDC-P represents a separate prostatic lesion and should be graded as a poorly differentiated carcinoma.

Signal transducer and activator of transcription 5A/B in prostate and breast cancers

Protein kinase signaling pathways, such as Janus kinase 2-Signal transducer and activator of transcription 5A/B (JAK2-STAT5A/B), are of significant interest in the search for new therapeutic strategies in both breast and prostate cancers. In prostate cancer, the components of the JAK2-STAT5A/B signaling pathway provide molecular targets for small-molecule inhibition of survival and growth signals of the cells. At the same time, new evidence suggests that the STAT5A/B signaling pathway is involved in the transition of organ-confined prostate cancer to hormone-refractory disease. This implies that the active JAK2-STAT5A/B signaling pathway potentially provides the means for pharmacological intervention of clinical prostate cancer progression. In addition, active STAT5A/B may serve as a prognostic marker for identification of those primary prostate cancers that are likely to progress to aggressive disease. In breast cancer, the role of STAT5A/B is more complex. STAT5A/B may have a dual role in the regulation of malignant mammary epithelium. Data accumulated from mouse models of breast cancer suggest that in early stages of breast cancer STAT5A/B may promote malignant transformation and enhance growth of the tumor. This is in contrast to established breast cancer, where STAT5A/B may mediate the critical cues for maintaining the differentiation of mammary epithelium. In addition, present data suggest that activation of STAT5A/B in breast cancer predicts favorable clinical outcome. The dual nature of STAT5A/B action in breast cancer makes the therapeutic use of STAT5 A/B more complex.

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.

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.

Androgen enhances the antiproliferative activity of vitamin D3 by suppressing 24-hydroxylase expression in LNCaP cells

25-Hydroxyvitamin D3-24-hydroxylase (24-hydroxylase, CYP24) is an important inactivating enzyme controlling the concentrations of both active metabolites 25-hydroxyvitamin D3 and 1alpha,25-dihydroxyvitamin D3. In this paper, we demonstrate that 25-hydroxyvitamin D3 at 500 nM significantly increases the expression of 24-hydroxylase mRNA and the increase is significantly decreased by 5alpha-dihydrotestosterone (DHT) at concentrations of 1-100 nM in androgen-sensitive prostate cancer cells LNCaP. 25-Hydroxyvitamin D3 at 500 nM and 1alpha,25-dihydroxyvitamin D3 at 10 nM inhibit LNCaP cell growth, and the growth inhibition is enhanced by 1 nM DHT. Neither 25-hydroxyvitamin D3 nor 1alpha,25-dihydroxyvitamin D3 at physiological concentrations has growth effect. However, in the presence of 1 nM DHT, both 25-hydroxyvitamin D3 and 1alpha,25-dihydroxyvitamin D3 at physiological concentrations are clearly antiproliferative. These data demonstrate that DHT enhances the antiproliferative activity of Vitamin D3 hormones by inhibiting their inactivating enzyme. Most previous studies on Vitamin D3 action in cell cultures have used pharmacological concentrations of 1alpha,25-dihydroxyvitamin D3, the present results demonstrate, for the first time, that both 25-hydroxyvitamin D3 and 1alpha,25-dihydroxyvitamin D3 at physiological concentrations are active in the presence of physiological concentration of androgen. The combined use of androgen and Vitamin D3 metabolites could be a promising treatment for prostate cancer.

Retinoic acid via RARalpha inhibits the expression of 24-hydroxylase in human prostate stromal cells

25-Hydroxyvitamin D(3)-24-hydroxylase (24-hydroxylase) is an important inactivating enzyme and its expression is induced by 25-hydroxyvitamin D3 (25OHD3) and 1alpha,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3) through action of heterodimers of vitamin D receptor (VDR) and retinoid X receptor (RXR). RXRs also act as heterodimer partners for retinoic acid receptors (RARs), mediating the action of all-trans-retinoic acid (ATRA). Prostate stroma plays a crucial role in prostate cancer development and benign prostatic hyperplasia. We demonstrate here that ATRA markedly reduced the expression of 24-hydroxylase mRNA induced by 25OHD3 and 1alpha,25-(OH)2D3 in human prostatic stromal cells P29SN and P32S but not in epithelial cells PrEC or cancer cells LNCaP. By using transfection and RAR-selective ligands, we found that the inhibitory effect of ATRA on 24-hydroxylase expression in stromal cells was mediated by RARalpha but not by RARbeta. Moreover, the ATRA-induced expression of RARbeta was also mediated by RARalpha. The combined treatment of 1alpha,25-(OH)2D3 and RARalpha agonist Am80 at 10 nM exhibited strong growth-inhibitory effect whereas either alone had no effect. Our data suggest that ATRA suppresses 24-hydroxylase expression through RARalpha-dependent signaling pathway and can enhance vitamin D action in suppression of cell growth.

Genetic imbalances in endometrial hyperplasia and endometrioid carcinoma detected by comparative genomic hybridization

OBJECTIVE

To evaluate the sequential genomic copy alterations related to the development of precursor lesions and endometrioid-type endometrial carcinomas, and its association with cellular atypia.

STUDY DESIGN

Paraffin-embedded tissue specimens from 32 cases of endometrial hyperplasia, 15 of endometrial carcinoma, and 20 of normal endometrial tissue were retrospectively evaluated by the comparative genomic hybridization (CGH) technique. The average number of copy alterations (ANCA) index was used to define the incidence of genomic imbalances in each tissue group. Identified sequential genetic abnormalities were compared with the final histopathological diagnosis and the cellular atypia.

RESULTS

Detectable and consistent chromosomal imbalances were found in 13 hyperplasia and 9 carcinoma specimens. There was a significant correlation between ANCA value and degree of cellular atypia and tumor grade. While 1p36-pter, 20q deletions, and 4q overrepresentation were the most prevalent imbalances detected in both complex hyperplasia and complex atypical hyperplasia, 17q22-qter deletion and amplification of 2p34 were only seen in hyperplasia with atypical cells. Overrepresentations of chromosomes 8q, 1q, and 3q are the most frequent aberrations in endometrial carcinomas, but were absent from all the precursor lesions except one. Underrepresentations of chromosomes 1p36-pter and 10q are the other commonly seen aberrations in carcinomas, the latter being more frequent in moderately differentiated than in poorly differentiated lesions.

CONCLUSIONS

Different patterns of chromosomal aberrations are seen in precursor lesions than in endometrial carcinomas, except for the loss of 1p36-pter. The presence of 1p deletion in both endometrial hyperplasia and cancer specimens suggests that this is an early event in the development of carcinoma. These results support a stepwise mode of tumorigenesis with accumulation of a series of genomic copy alterations in endometrial carcinogenesis.

Mystique is a new insulin-like growth factor-I-regulated PDZ-LIM domain protein that promotes cell attachment and migration and suppresses Anchorage-independent growth

By comparing differential gene expression in the insulin-like growth factor (IGF)-IR null cell fibroblast cell line (R- cells) with cells overexpressing the IGF-IR (R+ cells), we identified the Mystique gene expressed as alternatively spliced variants. The human homologue of Mystique is located on chromosome 8p21.2 and encodes a PDZ LIM domain protein (PDLIM2). GFP-Mystique was colocalized at cytoskeleton focal contacts with alpha-actinin and beta1-integrin. Only one isoform of endogenous human Mystique protein, Mystique 2, was detected in cell lines. Mystique 2 was more abundant in nontransformed MCF10A breast epithelial cells than in MCF-7 breast carcinoma cells and was induced by IGF-I and cell adhesion. Overexpression of Mystique 2 in MCF-7 cells suppressed colony formation in soft agarose and enhanced cell adhesion to collagen and fibronectin. Point mutation of either the PDZ or LIM domain was sufficient to reverse suppression of colony formation, but mutation of the PDZ domain alone was sufficient to abolish enhanced adhesion. Knockdown of Mystique 2 with small interfering RNA abrogated both adhesion and migration in MCF10A and MCF-7 cells. The data indicate that Mystique is an IGF-IR-regulated adapter protein located at the actin cytoskeleton that is necessary for the migratory capacity of epithelial cells.

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.

The role of Vitamin D3 metabolism in prostate cancer

Vitamin D deficiency increases risk of prostate cancer. According to our recent results, the key Vitamin D hormone involved in the regulation of cell proliferation in prostate is 25(OH) Vitamin D3. It is mainly acting directly through the Vitamin D receptor (VDR), but partially also through its 1alpha-hydroxylation in the prostate. A deficiency of 25(OH) Vitamin D is common especially during the winter season in the Northern and Southern latitudes due to an insufficient sun exposure, but Vitamin D deficient diet may partially contribute to it. A lack of Vitamin D action may also be due to an altered metabolism or Vitamin D resistance. Vitamin D resistance might be brought up by several mechanisms: Firstly, an increased 24-hydroxylation may increase the inactivation of hormonal Vitamin D metabolites resulting in a Vitamin D resistance. This is obvious in the cancers in which an oncogenic amplification of 24-hydroxykase gene takes place, although an amplification of this gene in prostate cancer has not yet been described. During the aging, the activity of 24-hydroxylase increases, whereas 1alpha-hydroxylation decreases. Furthermore, it is possible that a high serum concentration of 25(OH)D3 could induce 24-hydroxylase expression in prostate. Secondly, Vitamin D receptor gene polymorphism or defects may result in a partial or complete Vitamin D resistance. Thirdly, an overexpression or hyperphosphorylation of retinoblastoma protein may result in an inefficient mitotic control by Vitamin D. Fourthly, endogenous steroids (reviewed by [D.M. Peehl, D. Feldman, Interaction of nuclear receptor ligands with the Vitamin D signaling pathway in prostate cancer, J. Steroid Biochem. Mol. Biol. (2004)]) and phytoestrogens may modulate the expression of Vitamin D metabolizing enzymes. In summary, the local metabolism of hormonal Vitamin D seems to play an important role in the development and progression of prostate cancer.

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.

Classification of prostatic carcinoma with artificial neural networks using comparative genomic hybridization and quantitative stereological data

Staging of prostate cancer is a mainstay of treatment decisions and prognostication. In the present study, 50 pT2N0 and 28 pT3N0 prostatic adenocarcinomas were characterized by Gleason grading, comparative genomic hybridization (CGH), and histological texture analysis based on principles of stereology and stochastic geometry. The cases were classified by learning vector quantization and support vector machines. The quality of classification was tested by cross-validation. Correct prediction of stage from primary tumor data was possible with an accuracy of 74-80% from different data sets. The accuracy of prediction was similar when the Gleason score was used as input variable, when stereological data were used, or when a combination of CGH data and stereological data was used. The results of classification by learning vector quantization were slightly better than those by support vector machines. A method is briefly sketched by which training of neural networks can be adapted to unequal sample sizes per class. Progression from pT2 to pT3 prostate cancer is correlated with complex changes of the epithelial cells in terms of volume fraction, of surface area, and of second-order stereological properties. Genetically, this progression is accompanied by a significant global increase in losses and gains of DNA, and specifically by increased numerical aberrations on chromosome arms 1q, 7p, and 8p.

Accuracy of an array comparative genomic hybridization (CGH) technique in detecting DNA copy number aberrations: comparison with conventional CGH and loss of heterozygosity analysis in prostate cancer

Although genomic DNA microarray (array comparative genomic hybridization [CGH]) technique is a rapid and powerful diagnostic tool for the comprehensive analysis of detailed chromosomal alterations of DNA copy numbers, its accuracy has not been well demonstrated. To clarify the accuracy of this technique, we applied array CGH spotted with 283 specific genes to 11 clinical prostate cancers, and the results were compared with comparative genomic hybridization (conventional CGH) and loss of heterozygosity (LOH) analysis using microsatellite DNA markers. The overall rate of correspondence between array CGH and conventional CGH with respect to the loss of DNA sequences was 94.5%. When the results of both CGH techniques were compared with those of LOH analysis, the correspondence rate of array CGH was significantly higher than that of conventional CGH (93.4% vs. 72.2%, P<0.05). In conclusion, the accuracy of array CGH was higher than that of conventional CGH in detecting losses of the DNA sequences. Array CGH is shown to be a promising tool for screening to identify unknown genes involved in tumorigenesis in prostate cancer.

Genetic aberrations in prostate carcinoma detected by comparative genomic hybridization and microsatellite analysis: association with progression and angiogenesis

BACKGROUND

In spite of increasing knowledge about the tumor biology of prostate cancer (PC), molecular events involved in tumor progression are not well characterized. There is evidence that a number of genetic alterations play a role in tumor progression and in addition, angiogenesis also contributes. In this study, comparative genomic hybridization (CGH), a sensitive method for detecting regional DNA copy number abnormalities, and microsatellite analysis was used to identify frequent genome changes in PC. Correlation of these data with microvessel density (MVD) and clinical follow-up data was performed to determine genetic alterations that are associated with angiogenesis and subsequent tumor progression.

METHODS

Fifty-seven paraffin embedded radical prostatectomy (RP) specimens were microdissected. DNA from the microdissected PC tissue was amplified by degenerate oligonucleoitide primed (DOP)-polymerase chain reaction (PCR), and CGH was performed on the PCR product. Quantitative analyses of the CGH profiles were performed using a t-statistic. Additionally, a microsatellite analysis of chromosome 13q was performed on a subgroup of 31 of the tumors. Using a polyclonal antibody against factor VIII, MVD was determined for all RP specimens. The results of CGH and microsatellite analysis were correlated with the clinical data of the patients and with MVD.

RESULTS

Forty-two of the tumors (75%) showed one or more gains while 39 (70%) showed one or more losses per tumor. The most frequent DNA copy number gains were on chromosome 3, 4, 7, 8, 10, 11, 12, 13, and X. The most frequent losses were on chromosomes 2, 5, 6, 8, 10, 13, 15, and 16. Cancer recurrence occurred in 15 patients. The total number of DNA copy number losses was significantly higher in patients with this progression (86%) than without (52%) (P < 0.001). There was no significant difference in the number of gains in patients with or without progression. Contingency table analysis showed a significant correlation between progression and losses in regions of chromosomes 6q and 13q and a gain of chromosome 7q. In multivariate analysis, only loss of chromosome 6 was independently prognostic. The gains that correlated most closely with MVD > 35 were on chromosomes 2q, 7q, and Xq, while the losses most closely associated with MVD > 35 were on chromosomes 8q, 10q, and 13q. However, only the association between loss of chromosome 13q and MVD > 35 was statistically significant. Microsatellite analysis revealed a statistically significant correlation between MVD and instability of locus 171.

CONCLUSIONS

This study indicates that the frequency of genetic alterations in PC as detected by CGH correlates with clinical outcome, and that losses of DNA from chromosomes 6q and 13q are important events that correlate with tumor progression, with loss of 13q, especially instability of locus 171, also associated with angiogenesis.

Identification of recurrent regions of chromosome loss and gain in vestibular schwannomas using comparative genomic hybridisation

BACKGROUND

Schwannomas are benign tumours of the nervous system that are usually sporadic but also occur in the inherited disorder neurofibromatosis type 2 (NF2). The NF2 gene is a tumour suppressor on chromosome 22. Loss of expression of the NF2 protein product, merlin, is universal in both sporadic and NF2 related schwannomas. The GTPase signalling molecules RhoA and Rac1 regulate merlin function, but to date only mutation in the NF2 gene has been identified as a causal event in schwannoma formation.

METHODS

Comparative genomic hybridisation (CGH) was used to screen 76 vestibular schwannomas from 76 patients (66 sporadic and 10 NF2 related) to identify other chromosome regions that may harbour genes involved in the tumorigenesis.

RESULTS

The most common change was loss on chromosome 22, which was more frequent in sporadic than in NF2 related tumours. Importantly, eight tumours (10%) showed gain of copy number on chromosome 9q34. Each of the two NF2 patients who had received stereotactic radiotherapy had non-chromosome 22 changes, whereas only one of eight non-irradiated NF2 patients had any chromosome changes. Three tumours had gain on 17q, which has also been reported in malignant peripheral nerve sheath tumours that are associated with neurofibromatosis type 1. Other sites that were identified in three or fewer tumours were regions on chromosomes 10, 11, 13, 16, 19, 20, X, and Y.

CONCLUSIONS

These findings should be verified using techniques that can detect smaller genetic changes, such as microarray-CGH.