Castration-resistant Prostate Cancer Tissues Research Articles

The altered expression of MiR‐221/‐222 and MiR‐23b/‐27b is associated with the development of human castration resistant prostate cancer

We have previously identified seven miRs-miR-221, -222, -23b, -27b, -15a, -16-1, and -203, that are differentially expressed in the hormone sensitive LNCaP cell line and the hormone resistant LNCaP-abl cell line and hypothesized that these miRs may characterize certain subtypes of human castration resistant prostate cancer (CRPC). Functional studies in cell culture systems have been performed to determine the effect of alternated expression level on cellular response to androgen treatment. To determine the clinical relevance of the expression patterns of these miRs, we compared the expression levels of these seven miRs in normal prostate tissues from 86 individuals, prostate tumor tissues from 34 individuals with localized hormone naïve disease, and bone-derived metastatic CRPC tissues from 17 individuals. The altered expression of miR-221/-222 (as previously described) or miR-203 affected the cellular response to androgen treatment, suggesting their potential involvement in the transition to CRPC. However, the expression of miR-23b, -27b, -15a, and -16-1 did not have a significant influence in the cellular response to androgen treatment, suggesting that these miRs may not play a causative role in the CRPC phenotype. Comparison of the expression levels of these miRs in tissue samples revealed that strikingly, ∼90% of the analyzed metastatic CRPC tumors could be characterized by the increased miR-221/-222 expression and the down-regulated miR-23b/-27b expression. This finding suggests that altered miR-221/-222 and miR-23b/-27b expression may be associated with the CRPC process.

Androgen receptor variants occur frequently in castration resistant prostate cancer metastases.

BackgroundAlthough androgens are depleted in castration resistant prostate cancer (CRPC), metastases still express nuclear androgen receptor (AR) and androgen regulated genes. We recently reported that C-terminal truncated constitutively active AR splice variants contribute to CRPC development. Since specific antibodies detecting all C-terminal truncated AR variants are not available, our aim was to develop an approach to assess the prevalence and function of AR variants in prostate cancer (PCa).Methodology/Principal FindingsUsing 2 antibodies against different regions of AR protein (N- or C-terminus), we successfully showed the existence of AR variant in the LuCaP 86.2 xenograft. To evaluate the prevalence of AR variants in human PCa tissue, we used this method on tissue microarrays including 50 primary PCa and 162 metastatic CRPC tissues. RT-PCR was used to confirm AR variants. We observed a significant decrease in nuclear C-terminal AR staining in CRPC but no difference between N- and C-terminal AR nuclear staining in primary PCa. The expression of the AR regulated proteins PSA and PSMA were marginally affected by the decrease in C-terminal staining in CRPC samples. These data suggest that there is an increase in the prevalence of AR variants in CRPC based on our ability to differentiate nuclear AR expression using N- and C-terminal AR antibodies. These findings were validated using RT-PCR. Importantly, the loss of C-terminal immunoreactivity and the identification of AR variants were different depending on the site of metastasis in the same patient.ConclusionsWe successfully developed a novel immunohistochemical approach which was used to ascertain the prevalence of AR variants in a large number of primary PCa and metastatic CRPC. Our results showed a snapshot of overall high frequency of C-terminal truncated AR splice variants and site specific AR loss in CRPC, which could have utility in stratifying patients for AR targeted therapeutics.

Abstract 4556: AR intragenic rearrangement and altered androgen receptor mRNA splicing in castration-resistant prostate cancer

Abstract Androgen depletion for advanced prostate cancer (PCa) targets activity of the androgen receptor (AR), a steroid receptor transcription factor required for PCa growth. The emergence of lethal castration-resistant PCa (CRPCa) is marked by aberrant re-activation of the AR despite ongoing androgen depletion. Recently, alternative splicing has been described as a mechanism giving rise to COOH-terminally truncated, constitutively active AR isoforms that can support the CRPCa phenotype. However, the pathologic origin of these truncated AR isoforms has not been described. The goal of this study was to investigate alterations in AR expression arising in a cell-based model of PCa progression driven by truncated AR isoform activity. We demonstrate that stable, high-level expression of truncated AR isoforms in 22Rv1 CRPCa cells coincides with intragenic rearrangement of a ∼35kb AR genomic segment, which contains several alternative AR exons. Analysis of metastatic CRPCa tissues indicated that related AR copy number alterations are frequent and often occur in conjunction with high-level AR amplification. Nucleotide-level resolution of the break fusion junction in 22Rv1 cells revealed a DNA repair signature consistent with a microhomology-mediated, replication-based mechanism of origin. Together, these data provide the first report of AR intragenic rearrangements in CRPCa and a link with pathologic expression of truncated AR isoforms in a cell-based model of PCa progression. 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 4556. doi:10.1158/1538-7445.AM2011-4556

Identification of gene copy number and whole-genome methylation changes associated with lethal metastatic castration-resistant prostate cancer (CRPC).

6 Background: Metastatic CRPC undergoes significant genomic evolution compared to primary, localized disease. Multiple genetic mechanisms contribute to this evolution including changes in gene copy number as well as and changes in CpG island methylation. In this study, copy number and methylation status of metastatic CRPC tissue obtained at autopsy were assessed by high-resolution array comparative genomic hybridization (aCGH) and whole genome methylation microarray profiling. Methods: Array CGH was performed on DNA isolated from metastatic CRPC samples obtained from the University of Michigan Rapid Autopsy Program, using the Agilent Human Genome 244K CGH Microarray. A total of 15 samples comprising 7 metastatic liver implants and 8 soft tissue metastases were analyzed with DNA Analytics 4.0 software. Expression of genes identified as commonly amplified or deleted was assessed in a confirmatory fashion using existing Agilent 4×44 Expression Array data. The Illumina Infinium HumanMethylation27 BeadChip was used to determine whole genome methylation status. Results: A total of 79 amplified and 419 deleted genes common to >66% of samples were identified. There was significant correlation (p<0.05) of gene copy number to the mRNA level for 9 of the amplified and 76 of the deleted genes, including amplification/overexpression of AR and deletion/underexpression of the tumor suppressors PTEN and RB. While copy number was normal for the androgen synthesis genes CYP17A1, HSD17B3, HSD17B4, and HSD3B2, methylation analysis indicates their upregulation in the majority of samples, suggesting an alternative mechanism of intratumoral hormone production. There was promoter hypermethylation and gene deletion of RB1 in >85% of samples, suggesting that inactivation of this tumor suppressor through multiple pathways is critical to tumor cell survival. Conclusions: This is the first known study examining both gene copy number and whole genome CpG island methylation status in metastatic CRPC. Integration of this data allows for identification of specific genes or pathways that confer a selective growth advantage to prostate cancer cells harboring those changes. No significant financial relationships to disclose.

Effect of castration monotherapy on the levels of adrenal androgens in cancerous prostatic tissues

The mechanism accounting for the development of castration-resistant prostate cancer (CRPC) remains unclear. Studies in CRPC tissues suggest that, after androgen deprivation therapy (ADT), the adrenal androgens may be an important source of testosterone (T) and 5-alpha dihydrotestosterone (DHT) in CRPC tissues. To clarify the role of adrenal androgens in the prostatic tissues (prostatic tissue adrenal androgens) during ADT, we developed a high sensitive and specific quantification method for the levels of androgens in prostatic tissue using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Human prostatic tissues were purified using mixed-mode reversed-phase, strong anion exchange Oasis cartridges (Oasis MAX). Analysis of steroids was performed using LC–MS/MS after picolinic acid derivatization. The validation tests showed that our method of quantitative analysis was precise and sensitive enough for the quantification of dehydroepiandrosterone (DHEA), androstenedione, androstenediol, T, and DHT in the prostatic tissue. The levels of adrenal androgens in prostate cancer tissues after ADT were similar to those in untreated PCa. Especially, DHEA was the most existing androgen precursor in PCa tissues after ADT. The levels of DHEA were high in PCa tissues, irrespective of ADT. We assumed that DHEA played a significant role in the synthesis of T and DHT in PCa tissues after ADT.

ERG Cooperates with Androgen Receptor in Regulating Trefoil Factor 3 in Prostate Cancer Disease Progression

To elucidate the role of ETS gene fusions in castration-resistant prostate cancer (CRPC), we characterized the transcriptome of 54 CRPC tumor samples from men with locally advanced or metastatic disease. Trefoil factor 3 (TFF3) emerged as the most highly differentially regulated gene with respect to ERG rearrangement status and resistance to hormone ablation therapy. Conventional chromatin immunoprecipitation (ChIP)-polymerase chain reaction and ChIP followed by DNA sequencing (ChIP-seq) revealed direct binding of ERG to ETS binding sites in the TFF3 promoter in ERG-rearranged prostate cancer cell lines. These results were confirmed in ERG-rearranged hormone-naive prostate cancer (HNPC) and CRPC tissue samples. Functional studies demonstrated that ERG has an inhibitory effect on TFF3 expression in hormone-naive cancer but not in the castration-resistant state. In addition, we provide evidence suggesting an effect of androgen receptor signaling on ERG-regulated TFF3 expression. Furthermore, TFF3 overexpression enhances ERG-mediated cell invasion in CRPC prostate cancer cells. Taken together, our findings reveal a novel mechanism for enhanced tumor cell aggressiveness resulting from ERG rearrangement in the castration-resistant setting through TFF3 gene expression.

Overcoming Persistent Dependency on Androgen Signaling after Progression to Castration-Resistant Prostate Cancer

Prostate cancer is the most common form of cancer in males in the United States, and the second leading cause of cancer death. Initially, most cases of prostate cancer respond well to hormone therapy; however, resistance often develops rapidly, leading to castration-resistant prostate cancer (CRPC). Several mechanisms for castration resistance have been proposed, of which the most significant seems to be the "intracrine" production of androgens from adrenal androgen or intratumorally via the de novo route. This mechanism stimulates disease progression through reactivation of androgen receptor signaling in patients who have previously undergone castration therapy. 17,20-lyase is essential for androgen synthesis in both the adrenal glands and CRPC tissue, and some 17,20-lyase inhibitors and second-generation anti-androgens that were developed to treat CRPC are currently under clinical investigation, with encouraging preliminary data reported so far. However, resistance to some of these therapies has already been noted. The study of circulating tumor cells will likely be important not only to identify patients likely to receive benefit from this therapeutic approach, but also to further understand the molecular mechanisms of resistance.

Abstract LB-21: Emergence of castration resistant prostate cancer class defined by recurrent ERG fusion

Abstract The role of recurrent ETS gene fusions in castration resistant prostate cancer (CRPC) is poorly understood. We characterized the transcriptome of CRPC by interrogating a cohort of 54 men with locally advanced or metastatic CRPC using a gene expression profiling method recently established for formalin-fixed paraffin-embedded tissue. We found increased expression of multiple genes in ERG rearranged tumors which suggests a selective growth advantage under oxygen poor conditions. We discovered that trefoil factor 3 (TFF3) is the top differentially regulated gene by both ERG rearrangement and resistance to therapy. Conventional chromatin immunoprecipitation (ChIP)-PCR and ChIP-seq data revealed direct binding of ERG to ETS binding sites in the TFF3 promoter in ERG rearranged prostate cancer cell lines, which was confirmed in ERG rearranged hormone naïve prostate cancer (HNPC) and CRPC tissue samples. In vitro data suggested that ERG has an inhibitory effect on TFF3 expression in hormone naïve cancer, which was relieved in CRPC depending on the level of AR expression. These findings reveal an interplay between ERG rearrangement and AR signaling in CRPC, and provide perspective towards novel therapeutic targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-21.

Review: Castration-resistant prostate cancer: new science and therapeutic prospects

There is a growing number of new therapies targeting different pathways that will revolutionize patient management strategies in castration-resistant prostate cancer (CRPC) patients. Today there are more clinical trial options for CRPC treatment than ever before, and there are many promising agents in late-stage clinical testing. The hypothesis that CRPC frequently remains driven by a ligand-activated androgen receptor (AR) and that CRPC tissues exhibit substantial residual androgen levels despite gonadotropin-releasing hormone therapy, has led to the evaluation of new oral compounds such as abiraterone and MDV 3100. Their results, coupled with promising recent findings in immunotherapy (eg sipuleucel-T) and with agents targeting angiogenesis (while awaiting the final results of the CALGB trial 90401) will most probably impact the management of patients with CRPC in the near future. Other new promising agents need further development. With our increased understanding of the biology of this disease, further trial design should incorporate improved patient selection so that patient populations are those who may be most likely to benefit from treatment.

Evidence of Limited Contributions for Intratumoral Steroidogenesis in Prostate Cancer

Androgen-deprivation therapy for prostate cancer (PC) eventually leads to castration-resistant PC (CRPC). Intratumoral androgen production might contribute to tumor progression despite suppressed serum androgen concentrations. In the present study, we investigated whether PC or CRPC tissue may be capable of intratumoral androgen synthesis. Steroidogenic enzyme mRNAs were quantified in hormonally manipulated human PC cell lines and xenografts as well as in human samples of normal prostate, locally confined and advanced PC, local nonmetastatic CRPC, and lymph node metastases. Overall, the majority of samples showed low or absent mRNA expression of steroidogenic enzymes required for de novo steroid synthesis. Simultaneous but low expression of the enzymes CYP17A1 and HSD3B1, essential for the synthesis of androgens from pregnenolone, could be detected in 19 of 88 patient samples. Of 19 CRPC tissues examined, only 5 samples expressed both enzymes. Enzymes that convert androstenedione to testosterone (AKR1C3) and testosterone to dihydrotestosterone (DHT; SRD5A1) were abundantly expressed. AKR1C3 expression was negatively regulated by androgens in the experimental models and was increased in CRPC samples. Expression of SRD5A1 was upregulated in locally advanced cancer, CRPC, and lymph node metastases. We concluded that intratumoral steroid biosynthesis contributes less than circulating adrenal androgens, implying that blocking androgen production and its intraprostatic conversion into DHT, such as via CYP17A1 inhibition, may represent favorable therapeutic options in patients with CRPC.

Improving the efficacy of targeted trials by multiple-marker analysis in castration-resistant prostate cancer

Objectives In order to improve the efficacy of targeted therapy trials, the expression profiles of several molecular markers that are potential candidates for targeted therapy were analyzed in patients with progressive castration-resistant prostate cancer. Methods and materials Paraffin-embedded samples of tumor tissue from 51 patients obtained from biopsies of metastases or remaining prostates were analyzed immunohistochemically for the expression of EGFR, PDGFRβ, Her-2/neu, c-Kit, and VEGF. Staining was analyzed according to the percentage of positively stained tumor cells and the intensity of staining. Results According to the different cut-off values of 10%, 30%, 50%, or 70% for the percentage of positively stained cells, different rates of expression were found. Expression rates ranged from 30.6% to 61.2% for EGFR, from 34.7% to 57.1% for PDGFRβ, from 9.6% to 28.8% for Her-2/neu, from 12.5% to 22.4% for c-Kit, and from 51.1% to 74.5% for VEGF. Defining positive expression as ≥30% positively stained tumor cells, with an intensity of staining of ≥2+, resulted in positive expression of EGFR in 38.8%, PDGFRβ in 24.5%, Her-2/neu in 13.5%, c-Kit in 6.4%, and VEGF in 44.7% of the patients. Conclusions Our results demonstrate simultaneous expression of several markers in castration-resistant prostate cancer tissue. Translation of the results into modern, multi-arm clinical trial designs will improve the efficacy of recruiting and obtaining results, compared with multiple double-arm trials.

Overexpressing PKIB in prostate cancer promotes its aggressiveness by linking between PKA and Akt pathways

Prostate cancer (PC) is the most common malignancy in males. Despite high response rates and clinical benefits, androgen-ablation therapy is ineffective for advanced or relapsed PC because of the emergence of aggressive castration-resistant prostate cancer (CRPC). Through our genome-wide gene expression analysis of PC cells purified from clinical CRPC tissues, we here identified a novel molecular target, PKIB (cAMP-dependent protein kinase inhibitor-beta), which was overexpressed specifically in CRPCs and aggressive PCs. Immunohistochemical analysis confirmed its overexpression in CRPCs and its strong correlation with high Gleason scores of PCs. Knockdown of PKIB by siRNA resulted in drastic growth suppression of PC cells, and, concordantly, exogenous introduction of PKIB into PC cells enhanced their growth and mobility. We found the direct interaction between PKIB and cAMP-dependent protein kinase A catalytic subunit (PKA-C), and showed that knockdown of PKIB in PC cells diminished the nuclear translocation of PKA-C. Knockdown of PKIB also decreased the phosphorylation level of Akt at Ser473 in PC cells, and exogenous PKIB introduction enhanced Akt phosphorylation in PC cells by incorporating with endogenous PKA-C kinase. In vitro kinase assay validated the recombinant PKIB enhanced phosphorylation of Akt at Ser473 by PKA-C kinase. These findings show that PKIB and PKA-C kinase can have critical functions of aggressive phenotype of PCs through Akt phosphorylation and that they should be a promising molecular target for PC treatment.