Bcl-2 associated athanogene 5 (Bag5) is overexpressed in prostate cancer and inhibits ER-stress induced apoptosis

Background

The Bag (Bcl-2 associated athanogene) family of proteins consists of 6 members sharing a common, single-copied Bag domain through which they interact with the molecular chaperone Hsp70. Bag5 represents an exception in the Bag family since it consists of 5 Bag domains covering the whole protein. Bag proteins like Bag1 and Bag3 have been implicated in tumor growth and survival but it is not known whether Bag5 also exhibits this function.

Methods

Bag5 mRNA and protein expression levels were investigated in prostate cancer patient samples using real-time PCR and immunoblot analyses. In addition immunohistological studies were carried out to determine the expression of Bag5 in tissue arrays. Analysis of Bag5 gene expression was carried out using one-way ANOVA and Bonferroni’s Multiple Comparison test. The mean values of the Bag5 stained cells in the tissue array was analyzed by Mann-Whitney test. Functional studies of the role of Bag5 in prostate cancer cell lines was performed using overexpression and RNA interference analyses.

Results

Our results show that Bag5 is overexpressed in malignant prostate tissue compared to benign samples. In addition we could show that Bag5 levels are increased following endoplasmic reticulum (ER)-stress induction, and Bag5 relocates from the cytoplasm to the ER during this process. We also demonstrate that Bag5 interacts with the ER-resident chaperone GRP78/BiP and enhances its ATPase activity. Bag5 overexpression in 22Rv.1 prostate cancer cells inhibited ER-stress induced apoptosis in the unfolded protein response by suppressing PERK-eIF2-ATF4 activity while enhancing the IRE1-Xbp1 axis of this pathway. Cells expressing high levels of Bag5 showed reduced sensitivity to apoptosis induced by different agents while Bag5 downregulation resulted in increased stress-induced cell death.

Conclusions

We have therefore shown that Bag5 is overexpressed in prostate cancer and plays a role in ER-stress induced apoptosis. Furthermore we have identified GRP78/BiP as a novel interaction partner of Bag5.

Detection of smell print differences between nonmalignant and malignant prostate cells with an electronic nose

AIM

To determine whether an electronic nose can differentiate cultured nonmalignant and malignant prostatic cells from each other and whether the smell print is secreted to the surrounding medium.

MATERIALS & METHODS

Prostatic nonmalignant (EP-156T and controls) and malignant (LNCaP) cell lines, as well as conditioned and unconditioned media, were collected. The smell prints of the samples were analyzed by a ChemPro(®) 100 electronic nose device. The data were normalized and dimension reduction was conducted. The samples were classified and misclassification rates were calculated.

RESULTS

The electronic nose differentiated the nonmalignant and malignant cell lines from each other, achieving misclassification rates of 2.9-3.6%. Cells did not differ from the conditioned medium but differed from the unconditioned medium (misclassification rates: 0.0-25.6%).

CONCLUSION

Malignant and nonmalignant prostatic cell lines have distinct smell prints. Prostatic cancer cells seem to modify the smell print of their medium.

The tumorigenic FGFR3-TACC3 gene fusion escapes miR-99a regulation in glioblastoma

Fusion genes are chromosomal aberrations that are found in many cancers and can be used as prognostic markers and drug targets in clinical practice. Fusions can lead to production of oncogenic fusion proteins or to enhanced expression of oncogenes. Several recent studies have reported that some fusion genes can escape microRNA regulation via 3'-untranslated region (3'-UTR) deletion. We performed whole transcriptome sequencing to identify fusion genes in glioma and discovered FGFR3-TACC3 fusions in 4 of 48 glioblastoma samples from patients both of mixed European and of Asian descent, but not in any of 43 low-grade glioma samples tested. The fusion, caused by tandem duplication on 4p16.3, led to the loss of the 3'-UTR of FGFR3, blocking gene regulation of miR-99a and enhancing expression of the fusion gene. The fusion gene was mutually exclusive with EGFR, PDGFR, or MET amplification. Using cultured glioblastoma cells and a mouse xenograft model, we found that fusion protein expression promoted cell proliferation and tumor progression, while WT FGFR3 protein was not tumorigenic, even under forced overexpression. These results demonstrated that the FGFR3-TACC3 gene fusion is expressed in human cancer and generates an oncogenic protein that promotes tumorigenesis in glioblastoma.

HOXB13 G84E mutation in Finland: population-based analysis of prostate, breast, and colorectal cancer risk

BACKGROUND

A recently identified germline mutation G84E in HOXB13 was shown to increase the risk of prostate cancer. In a family-based analysis by The International Consortium for Prostate Cancer Genetics (ICPCG), the G84E mutation was most prevalent in families from the Nordic countries of Finland (22.4%) and Sweden (8.2%).

METHODS

To further investigate the importance of G84E in the Finns, we determined its frequency in more than 4,000 prostate cancer cases and 5,000 controls. In addition, 986 breast cancer and 442 colorectal cancer (CRC) cases were studied. Genotyping was conducted using TaqMan, MassARRAY iPLEX, and sequencing. Statistical analyses were conducted using Fisher exact test, and overall survival was analyzed using Cox modeling.

RESULTS

The frequency of the G84E mutation was significantly higher among patients with prostate cancer and highest among patients with a family history of the disease, hereditary prostate cancer [8.4% vs. 1.0% in controls; OR 8.8; 95% confidence interval (CI), 4.9-15.7]. The mutation contributed significantly to younger age (≤55 years) at onset and high prostate-specific antigen (PSA; ≥20 ng/mL) at diagnosis. An association with increased prostate cancer risk in patients with prior benign prostate hyperplasia (BPH) diagnosis was also revealed. No statistically significant evidence for a contribution in CRC risk was detected, but a suggestive role for the mutation was observed in familial BRCA1/2-negative breast cancer.

CONCLUSIONS

These findings confirm an increased cancer risk associated with the G84E mutation in the Finnish population, particularly for early-onset prostate cancer and cases with substantially elevated PSA.

IMPACT

This study confirms the overall importance of the HOXB13 G84E mutation in prostate cancer susceptibility.

Goserelin and bicalutamide treatments alter the expression of microRNAs in the prostate

BACKGROUND

Although endocrine therapy has been used for decades, its influence on the expression of microRNAs (miRNAs) in clinical tissue specimens has not been analyzed. Moreover, the effects of the TMPRSS2:ERG fusion on the expression of miRNAs in hormone naïve and endocrine-treated prostate cancers are poorly understood.

METHODS

We used clinical material from a neoadjuvant trial consisting of 28 men treated with goserelin (n = 8), bicalutamide (n = 9), or no treatment (n = 11) for 3 months prior to radical prostatectomy. Freshly frozen specimens were used for microarray analysis of 723 human miRNAs. Specific miRNA expression in cancer, benign epithelium and stromal tissue compartments was predicted with an in silico Bayesian modeling tool.

RESULTS

The expression of 52, 44, and 34 miRNAs was affected >1.4-fold by the endocrine treatment in the cancer, non-malignant epithelium, and stromal compartments, respectively. Of the 52 miRNAs, only 10 were equally affected by the two treatment modalities in the cancer compartment. Twenty-six of the 52 genes (50%) showed AR binding sites in their proximity in either VCaP or LNCaP cell lines. Forty-seven miRNAs were differentially expressed in TMPRSS2:ERG fusion positive compared with fusion negative cases. Endocrine treatment reduced the differences between fusion positive and negative cases.

CONCLUSIONS

Goserelin treatment and bicalutamide treatment mostly affected the expression of different miRNAs. The effect clearly varied in different tissue compartments. TMPRSS2:ERG fusion positive and negative cases showed differential expression of miRNAs, and the difference was diminished by androgen ablation.

Convergence of oncogenic and hormone receptor pathways promotes metastatic phenotypes

Cyclin D1b is a splice variant of the cell cycle regulator cyclin D1 and is known to harbor divergent and highly oncogenic functions in human cancer. While cyclin D1b is induced during disease progression in many cancer types, the mechanisms underlying cyclin D1b function remain poorly understood. Herein, cell and human tumor xenograft models of prostate cancer were utilized to resolve the downstream pathways that are required for the protumorigenic functions of cyclin D1b. Specifically, cyclin D1b was found to modulate the expression of a large transcriptional network that cooperates with androgen receptor (AR) signaling to enhance tumor cell growth and invasive potential. Notably, cyclin D1b promoted AR-dependent activation of genes associated with metastatic phenotypes. Further exploration determined that transcriptional induction of SNAI2 (Slug) was essential for cyclin D1b-mediated proliferative and invasive properties, implicating Slug as a critical driver of disease progression. Importantly, cyclin D1b expression highly correlated with that of Slug in clinical samples of advanced disease. In vivo analyses provided strong evidence that Slug enhances both tumor growth and metastatic phenotypes. Collectively, these findings reveal the underpinning mechanisms behind the protumorigenic functions of cyclin D1b and demonstrate that the convergence of the cyclin D1b/AR and Slug pathways results in the activation of processes critical for the promotion of lethal tumor phenotypes.

Androgen receptor (AR) aberrations in castration-resistant prostate cancer

Genetic aberrations affecting the androgen receptor (AR) are rare in untreated prostate cancers (PCs) but have been found in castration-resistant prostate cancers (CRPCs). Further, successful treatment with novel endocrine therapies indicates that CRPCs remain androgen-sensitive. Known AR aberrations include amplification of the AR gene leading to the overexpression of the receptor, point mutations of AR resulting in promiscuous ligand usage, and constitutively active AR splice variants. Gain, or amplification, of the AR gene is one of the most frequent genetic alterations observed in CRPCs. Up to 80% of CRPCs have been reported to carry an elevated AR gene copy number, and about 30% have a high-level amplification of the gene. AR mutations are also commonly observed and have been found in approximately 10-30% of the CRPC treated with antiandrogens; however, the frequency and significance of AR splice variants is still unclear. Because AR aberrations are found almost exclusively in CRPC, these alterations must have been selected for during therapy. Interestingly, these aberrations lead to activation of the receptor, despite treatment-induced emergence of therapy-resistant tumor clones. Therefore, future novel treatment strategies should focus on suppressing AR activity in CRPC.

Androgen receptor overexpression alters binding dynamics of the receptor to chromatin and chromatin structure

BACKGROUND

Castration-resistant prostate cancers (CRPCs) overexpress often androgen receptor (AR). Here, we investigated the effect of AR overexpression on the dynamics of AR loading and RNA polymerase II (RNA Pol II) recruitment to chromatin. Acetylation of histone 3 (AcH3) on lysines 9 and 14 (K9 and K14) was also studied.

METHODS

We used an LNCaP-based AR overexpression cell line model that includes a control line and two sublines, LNCaP-ARmo and LNCaP-ARhi, which overexpress AR twofold to threefold and fourfold to fivefold, respectively. Cells were exposed to 1 or 100 nM of dihydrotestosterone (DHT). Chromatin immunoprecipitation (ChIP) on the promoters and enhancers of prostate specific antigen (PSA) and transmembrane protease, serine 2 (TMPRSS2) genes was performed. qRT-PCR was used to measure the levels of PSA and TMPRSS2 transcripts.

RESULTS

Upon stimulation with 1 nM DHT, AR and RNA Pol II were recruited onto PSA and TMPRSS2 enhancer regions to a greater extent (P < 0.05) in AR-overexpressing cells compared to control cells. The difference in AR loading between the control and AR-overexpressing cells was abolished by a higher DHT concentration. The ratio of AcH3/H3 was increased in AR-overexpressing cells. The induction of transcription of PSA and TMPRSS2 occurred earlier in the AR-overexpressing cells.

CONCLUSIONS

Our findings suggest that the levels of AR potentiate the recruitment of the AR, as well as components of the basic transcription machinery, to chromatin and affect the acetylation of histones in the presence of low levels of androgens. These changes result in enhanced gene transcription of AR target genes.

The role of genetic markers in the management of prostate cancer

CONTEXT

Despite widespread screening for prostate cancer (PCa) and major advances in the treatment of metastatic disease, PCa remains the second most common cause of cancer death for men in the Western world. In addition, the use of prostate-specific antigen testing has led to the diagnosis of many potentially indolent cancers, and aggressive treatment of these cancers has caused significant morbidity without clinical benefit in many cases. The recent discoveries of inherited and acquired genetic markers associated with PCa initiation and progression provide an opportunity to apply these findings to guide clinical decision making.

OBJECTIVE

In this review, we discuss the potential use of genetic markers to better define groups of men at high risk of developing PCa, to improve screening techniques, to discriminate indolent versus aggressive disease, and to improve therapeutic strategies in patients with advanced disease.

EVIDENCE ACQUISITION

PubMed-based literature searches and abstracts through January 2012 provided the basis for this literature review. We also examined secondary sources from reference lists of retrieved articles and data presented at recent congresses. Cited review articles are only from the years 2007-2012, favoring more recent discussions because of the rapidly changing field. Original research articles were curated based on favoring large sample sizes, independent validation, frequent citations, and basic science directly related to potentially clinically relevant prognostic or predictive markers. In addition, all authors on the manuscript evaluated and interpreted the data acquired.

EVIDENCE SYNTHESIS

We address the use of inherited genetic variants to assess risk of PCa development, risk of advanced disease, and duration of response to hormonal therapies. The potential for using urine measurements such as prostate cancer antigen 3 (PCA3) RNA and the transmembrane protease, serine 2 v-ets erythroblastosis virus E26 oncogene homolog (avian) (TMPRSS2-ERG) gene fusion to aid screening is discussed. Multiple groups have developed gene expression signatures from primary prostate tumors correlating with poor prognosis, and attempts to improve and standardize these signatures as diagnostic tests are presented. Massive sequencing efforts are underway to define important somatic genetic alterations (amplifications, deletions, point mutations, translocations) in PCa, and these alterations hold great promise as prognostic markers and for predicting response to therapy. We provide a rationale for assessing genetic markers in metastatic disease for guiding choice of therapy and for stratifying patients in clinical trials, and discuss challenges in clinical trial design incorporating the use of these markers.

CONCLUSIONS

The use of genetic markers has the potential to aid disease screening, improve prognostic discrimination, and prediction of response to treatment. However, most markers have not been prospectively validated for providing useful prognostic or predictive information or improvement upon clinicopathologic parameters already in use. Significant efforts are underway to develop these research findings into clinically useful diagnostic tests in order to improve clinical decision making.

Chemical castration and anti-androgens induce differential gene expression in prostate cancer

Endocrine therapy by castration or anti-androgens is the gold standard treatment for advanced prostate cancer. Although it has been used for decades, the molecular consequences of androgen deprivation are incompletely known and biomarkers of its resistance are lacking. In this study, we studied the molecular mechanisms of hormonal therapy by comparing the effect of bicalutamide (anti-androgen), goserelin (GnRH agonist) and no therapy, followed by radical prostatectomy. For this purpose, 28 men were randomly assigned to treatment groups. Freshly frozen specimens were used for gene expression profiling for all known protein-coding genes. An in silico Bayesian modelling tool was used to assess cancer-specific gene expression from heterogeneous tissue specimens. The expression of 128 genes was > two-fold reduced by the treatments. Only 16% of the altered genes were common in both treatment groups. Of the 128 genes, only 24 were directly androgen-regulated genes, according to re-analysis of previous data on gene expression, androgen receptor-binding sites and histone modifications in prostate cancer cell line models. The tumours containing TMPRSS2-ERG fusion showed higher gene expression of genes related to proliferation compared to the fusion-negative tumours in untreated cases. Interestingly, endocrine therapy reduced the expression of one-half of these genes and thus diminished the differences between the fusion-positive and -negative samples. This study reports the significantly different effects of an anti-androgen and a GnRH agonist on gene expression in prostate cancer cells. TMPRSS2-ERG fusion seems to bring many proliferation-related genes under androgen regulation.

Abstract 5198: Elucidation of dynamic prostate epithelial hierarchy: Insights into transcriptional and epigenetic regulatory mechanisms

The aim of present investigation is to elucidate the complex stem cell dynamics within prostate cancer, which can be utilized to design novel diagnostic and therapeutic strategies for the management of prostate cancer. In order to determine precise transcriptional and microRNA regulatory mechanisms modulating stem cell self-renewal and differentiation, unique cellular assays have been developed in our lab that utilize homogeneous fractionated cell populations enriched from primary patient prostate cultures. Using a prospective bioinformatic analysis of gene expression data from Birnie et. al., 2008, we have identified LCN2, CEACAM6, and S100p as candidate genes for regulation of prostate stem cell differentiation. Their over-expression in differentiated cells, as compared to stem cells, was validated in respective cells enriched from cultures obtained from BPH, cancer and castration resistant prostate cancer samples and from primary human prostate cancer xenografts. Interestingly, the analysis of 25,000 published human Affymetrix microarray chips revealed that LCN2, CEACAM6, and S100p have a more similar expression pattern than that of any other genes in the entire human genome, suggesting that they may have common function and are co-regulated. Indeed, the promoter analysis showed that the promoters (1kb from TSS) of all these genes have common binding sites for 40 transcription factors with very high affinity and P &lt; 0.001. Most of these transcription factors have a well-documented role in cell differentiation (RA, AR, and NANOG) and prostate carcinogenesis (NF-kB). Significant up-regulation in the expression of these genes in prostate cell lines after treatment with all-trans retinoic acid and androgen analogue R1881 further suggested the role of AR and RA in prostate differentiation. Along with transcriptional regulation, Agilent v3 miRNA microarray data revealed obviously distinct miRNA expression profiles in stem and differentiated prostate epithelial cells, confirming crucial role of miRNA in main taining epithelial hierarchies, in prostate. We anticipate that evaluation of integrative transcriptional (LCN2-CEACAM6-S100p)-microRNA regulatory network, with further functional studies, will comprehensively establish a detailed knowledge base for potential regulatory mechanisms involved in prostate stem cell and prostate cancer stem cell differentiation. These insights will be valuable to formulate efficient ‘differentiation therapy’ for the management of prostate cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5198. doi:1538-7445.AM2012-5198

Histone H2B ubiquitin ligases RNF20 and RNF40 in androgen signaling and prostate cancer cell growth

Since data-mining from the Oncomine database revealed that expression of histone H2B K120 monoubiquitin (H2Bub1) ligase RNF20 is decreased in metastatic prostate cancer, we elucidated the effect of RNF20 and its homolog RNF40 on androgen receptor (AR)-dependent transcription and prostate cancer cell growth. Both RNF20 and RNF40 were able to functionally and physically interact with the AR and modulate its transcriptional activity in intact cells. Chromatin immunoprecipitation analyses showed that the androgen induction of FKBP51 and PSA in LNCaP prostate cancer cells is accompanied with a dynamic increase in the H2Bub1 within the transcribed regions of these loci. Interestingly, depletion of RNF20 or RNF40 strongly retarded the growth of LNCaP cells, which was however unlikely to be due to altered androgen signaling, but due to decreased expression of several cell cycle promoters. Collectively, our results suggest that RNF20 and RNF40, either via ubiquitylation of H2B or other targets, are coupled to the proliferation of prostate cancer cells.

Abstract A50: Cyclin D1 isoforms selectively manipulate AR signaling to promote metastatic phenotypes in early and castration-resistant prostate cancer

Cyclin D1 is a well-known inducer of cell cycle progression but has only recently been appreciated as a transcriptional regulator, controlling a milieu of transcriptional networks involved in both development and cancer. Intriguingly, while Cyclin D1 has only limited oncogenic activity, a variant that arises through oncogene induced alternative splicing (Cyclin D1b) has markedly enhanced oncogenic potential (as judged by in vitro and in vivo assays). Biochemical interrogation demonstrated that Cyclin D1b had little influence on cell cycle progression, indicating that oncogenic properties exerted by Cyclin D1b were likely transcriptionally regulated. Consonantly, it was shown that Cyclin D1b (but not full length Cyclin D1) is preferentially upregulated in malignant prostate cancers.

Here, models were developed to determine the tumor-specific functions of Cyclin D1b, and unbiased analysis performed to assess cellular consequence. First, expression of Cyclin D1b was found to promote anchorage independent growth and enhance invasive potential in an androgen receptor (AR) dependent manner, while exerting no effect on cell cycle progression. Second, a large transcriptional network was determined to be uniquely under the control of Cyclin D1b, a subset of which are known AR target genes. Among this AR regulated gene set was the transcriptional regulator SNAI2 (SLUG), known to promote phenotypes associated with cancer progression and metastasis in various systems. Third, the molecular mechanisms underpinning Cyclin D1b function were revealed as Cyclin D1b enhanced AR occupancy at conserved AR bindings sites at SNAI2 regulatory loci, which correlated with chromatin modifications associated with active transcription. Fourth, molecular inhibition of SNAI2 levels was sufficient to inhibit D1b induced phenotypes both in vitro and in vivo. Finally, while both Cyclin D1b and SLUG are expressed in nearly 1/3 of primary prostate tumors, relative expression is increased in metastatic as well as castration resistant prostate cancer samples, indicating the Cyclin D1b/SLUG pathway is likely involved in disease progression. Together, the study to be presented defines a mechanism to explain Cyclin D1b-mediated effects in human disease, provides evidence of a direct AR driven gene that is induced exclusively during PCa progression, and identifies the Cyclin D1b/AR/SLUG axis as a major pathway associated with metastatic phenotypes.

Citation Format: Michael A. Augello, Craig Burd, Ruth Bribe, Daniel Frigo, Jason Karch, Donald McDonnell, Tapio Visakorpi, Karen E. Knudsen. Cyclin D1 isoforms selectively manipulate AR signaling to promote metastatic phenotypes in early and castration-resistant prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A50.

Abstract A9: Androgen-regulated miR-32 targets BTG2 and is overexpressed in castration-resistant prostate cancer

The androgen receptor (AR) signaling pathway is central to the emergence of castration-resistant prostate cancer (CRPC). We set out to identify androgen-regulated microRNAs (miRNAs) that may contribute to the development of CRPC. We found miR-32 to be an androgen regulated miRNA which is differentially expressed in CRPC compared to benign prostate hyperplasia (BPH) according to microarray analyses. qRT-PCR analyses confirmed that miR-32 expression increases in CRPC compared to BPH, and that in untreated prostate cancer (PC) miR-32 expression is higher in tumors of stage pT3 compared to pT2. Transfection of pre-miR-32 to prostate cancer cell line LNCaP provided a significant growth advantage to the cells, and miR-32 was further demonstrated to reduce apoptosis. To identify target genes for miR-32, an mRNA microarray analysis was performed with LNCaP cells transfected with pre-miR-32. In this assay, B cell translocation gene 2 (BTG2) was identified as a novel putative target for miR-32. BTG2 was reduced both at mRNA and protein level in the cells transfected with pre-miR-32, and BTG2 was confirmed to be a miR-32 target by 3′-UTR-luciferase assay. Furthermore, BTG2 was able to partially rescue the growth advantage of miR-32 in LNCaP cells. Immunostainings of prostate cancer patient material showed a statistically significant (p &lt; 0.0001) reduction of BTG2 protein in CRPCs compared to PC. The lack of BTG2 staining was also associated (p=0.0021) with a short progression-free time in patients who underwent prostatectomy and inversely correlated to miR-32 expression levels. In conclusion, we find that miR-32 is an androgen-regulated miRNA targeting BTG2 and overexpressed in CRPC. Thus, miR-32 is a potential marker for aggressive disease and is a putative drug target in PC.

Citation Format: Sanni E. Jalava, Leena Latonen, Mauro Scaravilli, Kati K. Waltering, Janne Seppälä, Harri Lähdesmäki, Teuvo L.J. Tammela, Tapio Visakorpi. Androgen-regulated miR-32 targets BTG2 and is overexpressed in castrationresistant prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A9.

Abstract A28: Correlation of ERG expression with other genetic and expression abnormalities in prostate cancer

Fusion between TMPRSS2 (transmembrane protease, serine 2) and ERG (v-ets erythroblastosis virus E26 oncogene like (avian)) (TMPRSS2:ERG) is the most commonly found genetic alteration in prostate cancer and is found in 35–50% of all cases. TMPRSS2 is induced by the androgen receptor (AR). Fusion with TMPRSS2 renders ERG androgen inducible, causing most of its overexpression in prostate cancer. Studies suggest that SPINK1 (serine peptidase inhibitor, Kazal type 1) expression is exclusive to TMPRSS2:ERG fusion negative tumors, PTEN (phosphatase and tensin homolog) and TP53 (tumor protein p53) deletions are enriched in fusion positive tumors, a small region in chromosome 3p14 (including three possible tumor suppressor genes, FOX1, RYBP and SHQ1) is specifically deleted in a subset of fusion positive tumors, and that AR expression is down regulated in fusion positive tumors. Correlation with EZH2 (enhancer of zeste homolog 2 (Drosophila)) and Ki-67 (antigen identified by monoclonal antibody Ki-67) expression has also been suggested.

To confirm these correlations we used fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) techniques in our sample material, which consisted of 330 prostatectomy samples and 150 locally recurrent castration resistant prostate cancers (CRPC).

About half of the prostatectomy (47%, 107/230) and CRPC (45%, 70/156) samples showed positive ERG staining and ERG positivity was significantly associated with longer progression-free survival (p=0.0001, Log rank test) compared to ERG negative cases. Positive SPINK1 expression was seen in 14% (34/243) of the prostatectomy samples and in 12% (17/138) of the CRPC tumors. SPINK1 was almost exclusively expressed in ERG negative tumors (in prostatectomies p&lt;0.0001 and in CRPCs p=0.0132, Fisher's exact test). High AR staining was seen in 82% (206/252) of the prostatectomy samples and in 93% (127/136) of the CRPC tumors. In prostatectomy samples, AR expression was significantly associated with ERG positivity (p&lt;0.0001, Fisher's exact test). Low PTEN expression was seen in 15% (42/282) of the prostatectomy samples and in 45% (55/122) of the CRPC tumors. In CRPC tumors, but not in prostatectomy samples, loss of PTEN expression was associated with ERG positivity (p=0.0035, Fisher's exact test). Low PTEN expression was significantly associated with shorter progression-free survival compared to PTEN positive tumors (p=0.0133, Log rank test). Deletion of TP53 was seen in 8% (19/237) of the prostatectomy samples and in 18% (25/140) of the CRPC tumors. Deletion of chromosome region 3p14 was seen in approximately 4% of both prostatectomy (8/229) and CRPC (5/118) samples. Neither of these deletions was associated with ERG positivity. Analysis of Ki-67 and EZH2 staining is ongoing.

SPINK1 was almost exclusively expressed in ERG negative samples, and the association was statistically significant in both the prostatectomy samples and the locally recurrent CRPC samples. PTEN loss of expression was associated with ERG positivity in the CRPC samples, but not in the prostatectomy samples, indicating that this late event occurs preferentially in ERG positive cases. High AR expression was statistically significantly associated with ERG positivity. Since there shouldn't be any ERG expression from TMPRSS2:ERG fusion gene without AR, the results are in line with the known regulatory mechanisms of TMPRSS2:ERG. Contrary to previous reports, the specific deletions of 3p14 or TP53 were not enriched in the ERG positive samples. TP53 deletion was more frequent in the advanced disease.

Citation Format: Katri A. Leinonen, Teuvo L.J. Tammela, Outi R. Saramäki, Tapio Visakorpi. Correlation of ERG expression with other genetic and expression abnormalities in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A28.

Overall and worst gleason scores are equally good predictors of prostate cancer progression

Background

Gleason scoring has experienced several modifications during the past decade. So far, only one study has compared the prognostic abilities of worst (WGS) and overall (OGS) modified Gleason scores after the ISUP 2005 conference. Prostatic needle biopsies are individually paraffin-embedded in 57% of European pathology laboratories, whereas the rest of laboratories embed multiple (2 - 6) biopsies per one paraffin-block. Differences in the processing method can have a far-reaching effect, because reporting of the Gleason score (GS) is different for individually embedded and pooled biopsies, and GS is one of the most important factors when selecting treatment for patients.

Methods

The study material consisted of needle biopsies from 236 prostate cancer patients that were endocrine-treated in 1999-2003. Biopsies from left side and right side were embedded separately. Haematoxylin-eosin-stained slides were scanned and analyzed on web-based virtual microscopy. Worst and overall Gleason scores were assessed according to the modified Gleason score schema after analyzing each biopsy separately. The compound Gleason scores (CGS) were obtained from the original pathology reports. Two different grade groupings were used: GS 6 or less vs. 7 vs. 8 or above; and GS 7(3 + 4) or less vs. 7(4 + 3) and 8 vs. 9-10. The prognostic ability of the three scoring methods to predict biochemical progression was compared with Kaplan-Meier survival analysis and univariate and multivariate Cox regression analyses.

Results

The median follow-up time of the patients was 64.5 months (range 0-118). The modified GS criteria led to upgrading of the Gleason sums compared to the original CGS from the pathology reports 1999-2003 (mean 7.0 for CGS, 7.5 for OGS, 7.6 for WGS). In 43 cases WGS was > OGS. In a univariate analysis the relative risks were 2.1 (95%-confidence interval 1.8-2.4) for CGS, 2.5 (2.1-2.8) for OGS, and 2.6 (2.2-2.9) for WGS. In a multivariate analysis, OGS was the only independent prognostic factor.

Conclusions

All of the three Gleason scoring methods are strong predictors of biochemical recurrence. The use of modified Gleason scoring leads to upgrading of GS, but also improves the prognostic value of the scoring. No significant prognostic differences between OGS and WGS could be shown, which may relate to the apparent narrowing of the GS scale from 2-10 to 5-10 due to the recent modifications.

Diagnostic and prognostic signatures from the small non-coding RNA transcriptome in prostate cancer

Prostate cancer (PCa) is the most frequent male malignancy and the second most common cause of cancer-related death in Western countries. Current clinical and pathological methods are limited in the prediction of postoperative outcome. It is becoming increasingly evident that small non-coding RNA (ncRNA) species are associated with the development and progression of this malignancy. To assess the diversity and abundance of small ncRNAs in PCa, we analyzed the composition of the entire small transcriptome by Illumina/Solexa deep sequencing. We further analyzed the microRNA (miRNA) expression signatures of 102 fresh-frozen patient samples during PCa progression by miRNA microarrays. Both platforms were cross-validated by quantitative reverse transcriptase-PCR. Besides the altered expression of several miRNAs, our deep sequencing analyses revealed strong differential expression of small nucleolar RNAs (snoRNAs) and transfer RNAs (tRNAs). From microarray analysis, we derived a miRNA diagnostic classifier that accurately distinguishes normal from cancer samples. Furthermore, we were able to construct a PCa prognostic predictor that independently forecasts postoperative outcome. Importantly, the majority of miRNAs included in the predictor also exhibit high sequence counts and concordant differential expression in Illumina PCa samples, supported by quantitative reverse transcriptase-PCR. Our findings provide miRNA expression signatures that may serve as an accurate tool for the diagnosis and prognosis of PCa.

Androgen regulation of micro-RNAs in prostate cancer

BACKGROUND

Androgens play a critical role in the growth of both androgen dependent and castration-resistant prostate cancer (CRPC). Only a few micro-RNAs (miRNAs) have been suggested to be androgen regulated. We aim to identify androgen regulated miRNAs.

METHODS

We utilized LNCaP derived model, we have established, and which overexpresses the androgen receptor (AR), the VCaP cell line, and 13 intact-castrated prostate cancer (PC) xenograft pairs, as well as clinical specimens of untreated (PC) and CRPC. The expression of miRNAs was analyzed by microarrays and quantitative RT-PCR (Q-RT-PCR). Transfection of pre-miR-141 and anti-miR-141 was also used.

RESULTS

Seventeen miRNAs were > 1.5-fold up- or downregulated upon dihydrotestosterone (DHT) treatment in the cell lines, and 42 after castration in the AR-positive xenografts. Only four miRNAs (miR-10a, miR-141, miR-150*, and miR-1225-5p) showed similar androgen regulation in both cell lines and xenografts. Of those, miR-141 was found to be expressed more in PC and CRPC compared to benign prostate hyperplasia. Additionally, the overexpression of miR-141 enhanced growth of parental LNCaP cells while inhibition of miR-141 by anti-miR-141 suppressed the growth of the LNCaP subline overexpressing AR.

CONCLUSIONS

Only a few miRNAs were found to be androgen-regulated in both cell lines and xenografts models. Of those, the expression of miR-141 was upregulated in cancer. The ectopic overexpression of miR-141 increased growth of LNCaP cell suggesting it may contribute to the progression of PC.

Abstract 4194: Constitutive DNA-damage signaling promotes cancer cell proliferation through Chk1-CIP2A pathway independent of ATM-ATR

DNA damage is a hallmark of malignantly transformed cells. Accordingly, overexpression of the DNA damage activated kinases has been observed in different human cancers. However, it is unclear whether constitutive DNA damage present in unperturbed cancer cells promotes tumourigenesis.

Here we show that increased activity of DNA damage sensitive kinase Chk1 promotes proliferation of several cancer cell types by stimulating expression of CIP2A protein. Either chemical or genetic inhibition of Chk1, and not of ATM-ATR, results in potent inhibition of CIP2A protein expression levels. Importantly, Chk1 siRNA-elicited inhibition of cell proliferation and clonogenic growth is rescued by overexpression of CIP2A from a heterologous promoter. Moreover, in clinical (human) tumor samples there is a significant association between CIP2A and Chk1 expression in both ovarian and gastric cancers. Intriguingly, meta-analysis of seventeen published genome wide studies on different types of cancers unveils a striking similarity in the gene expression patterns of both CIP2A and Chk1. Amongst these, 12/17 studies show overexpression (top 10%) of both these proteins. Additionally, similarly to CIP2A, increased Chk1 expression is shown to correlate with tumor progression in human cancer.

In summary, these results identify a novel function for DNA damage kinase Chk1 in regulation of the human oncoprotein CIP2A. In general, these results provide an unprecented molecular mechanism by which constitutive DNA damage present in cancer cells promotes tumourigenesis. Additionally, as CIP2A is not significantly expressed in most of the normal human tissues, it is proposed that targeting of CIP2A might abrogate the Chk1-mediated support of proliferation without concerns related to anticancer therapy directly targeting Chk1.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4194. doi:10.1158/1538-7445.AM2011-4194

Abstract 4906: A systems approach into studying the changes in genetic regulation during prostate cancer progression

Prostate cancer (PC) is a complex disease that is currently the most common malignancy in males, and the second most frequent cause of cancer-related mortality in developed countries. Despite its high prevalence, the molecular mechanisms that induce PC progression are not well understood. The most common alterations affecting genetic regulation in PC are TMPRSS2:ERG gene fusions, 8q24 amplifications (including MYC-oncogene), and androgen receptor (AR) mutations and amplifications in castration-resistant (late stage) tumors. In normal prostatic tissue, local androgen metabolism maintains a balance between the proliferation and apoptotic cell death of prostatic epithelial cells. However in PC, androgen metabolism drives malignant transformation. The exact mechanisms which cause the imbalance in proliferation and apoptosis are not known, but likely include dysregulation of AR/MYC/ERG-regulated transcription factors (TFs) and/or microRNAs.

Using a systems biology approach, we jointly studied the accumulation of expression and copy number differences of TFs and microRNAs during PC progression. We first established a generic regulatory network consisting of transcription factors and microRNAs using three sets of sequence-based binding site predictions. First, TF binding sites were predicted by scanning the sequences upstream from gene transcription start sites for binding motifs from Transfac database, second, TF binding to microRNA promoters was predicted with ProbTF, and third, microRNA binding sites were obtained from Targetscan predictions. The inferred generic network was then adapted for studying PC by pruning it based on a set of publicly available gene expression, microRNA expression data. That is, we only considered those hypothetical regulatory connections that were supported by the data. By dividing these data into normal prostate tissue, primary PC's of different grade, and metastatic tumors, we were able to study the changes in regulation during different stages of the disease.

We uncovered putative regulatory motifs consisting of differentially expressed TFs and microRNAs. Another level of regulatory information was added by integrating copy number information to the regulatory motifs. We concentrated on the motifs that could be associated to AR-, ERG-, or MYC-signaling, due to their relevance in prostate cancer, or to molecules that are known to be regulated by these TFs. We found previously unknown microRNAs and TFs that may directly bound to the promoters of the TFs and therefore may have a critical effect to the malignancy of prostate cancers. The experimental validations of the most promising new candidate TF/microRNA regulatory connections are currently underway.

We demonstrated here an application of a systems biology based method to prostate cancer which was used to gain insights into the changes in genetic regulation during progression of the disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4906. doi:10.1158/1538-7445.AM2011-4906