Differential expression of 37 selected genes in hormone‐refractory prostate cancer using quantitative taqman real‐time RT‐PCR

The natural compound atraric acid suppresses androgen-regulated neo-angiogenesis of castration-resistant prostate cancer through angiopoietin 2

Castration-resistant prostate cancer (CRPC) is an aggressive lethal form of prostate cancer (PCa). Atraric acid (AA) not only inhibits the wild-type androgen receptor (AR) but also those AR mutants that confer therapy resistance to other clinically used AR antagonists, indicating a different mode of AR antagonism. AA induces cellular senescence and inhibits CRPC tumour growth in in vivo xenograft mouse model associated with reduced neo-angiogenesis suggesting the repression of intratumoural neo-angiogenesis by AA. In line with this, the secretome of CRPC cells mediates neo-angiogenesis in an androgen-dependent manner, which is counteracted by AA. This was confirmed by two in vitro models using primary human endothelial cells. Transcriptome sequencing revealed upregulated angiogenic pathways by androgen, being however VEGF-independent, and pointing to the pro-angiogenic factor angiopoietin 2 (ANGPT2) as a key driver of neo-angiogenesis induced by androgens and repressed by AA. In agreement with this, AA treatment of native patient-derived PCa tumour samples ex vivo inhibits ANGPT2 expression. Mechanistically, in addition to AA, immune-depletion of ANGPT2 from secretome or blocking ANGPT2-receptors inhibits androgen-induced angiogenesis. Taken together, we reveal a VEGF-independent ANGPT2-mediated angiogenic pathway that is inhibited by AA leading to repression of androgen-regulated neo-angiogenesis.

Subcellular Compartmentalization of Survivin is Associated with Biological Aggressiveness and Prognosis in Prostate Cancer

The role of subcellular survivin compartmentalization in the biology and prognosis of prostate cancer is unclear. We therefore investigated subcellular localization of survivin in more than 3000 prostate cancer patients by quantitative immunohistochemistry and performed transcriptomics of 250 prostate cancer patients and healthy donors using publicly available datasets. Survivin (BIRC5) gene expression was increased in primary prostate cancers and metastases, but did not differ in recurrent vs non-recurrent prostate cancers. Survivin immunohistochemistry (IHC) staining was limited exclusively to the nucleus in 900 prostate cancers (40.0%), and accompanied by various levels of cytoplasmic positivity in 1338 tumors (59.4%). 0.5% of prostate cancers did not express survivin. Nuclear and cytoplasmic survivin staining intensities were strongly associated with each other, pT category, and higher Gleason scores. Cytoplasmic but not nuclear survivin staining correlated with high tumor cell proliferation in prostate cancers. Strong cytoplasmic survivin staining, but not nuclear staining predicted an unfavorable outcome in univariate analyses. Multivariate Cox regression analysis showed that survivin is not an independent prognostic marker. In conclusion, we provide evidence that survivin expression is increased in prostate cancers, especially in metastatic disease, resulting in higher aggressiveness and tumor progression. In addition, subcellular compartmentalization is an important aspect of survivin cancer biology, as only cytoplasmic, but not nuclear survivin accumulation is linked to biological aggressiveness and prognosis of prostate cancers.

Quantitative RT-PCR analysis of PSA and prostate-specific membrane antigen mRNA to detect circulating tumor cells improves recurrence-free survival nomogram prediction after radical prostatectomy

BACKGROUND

Circulating tumor cell (CTC) analysis is a potential new biomarker in prostate cancer. We hypothesize that quantitative detection of CTCs in patients pre- and post-radical prostatectomy (RP) using quantitative TaqMan® fluorogenic RT-PCR will improve the accuracy of the Kattan nomogram to predict the probability of recurrence-free survival (RFS) post-RP.

METHODS

Ninty-two patients who underwent RP between 2004 and 2009 had venous blood samples taken pre- (Day - 1) and post-operatively (Day + 7). We performed quantitative Taqman® RT-PCR to detect circulating prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) mRNA. We calculated both the logarithmic ratio of Day + 7/Day - 1 for PSA (PSAr) and PSMA (PSMAr) expression (log(Day+7/Day-1) ) and the Kattan nomogram predicted probability of disease recurrence for each patient. We then analyzed how the AUC-ROC analysis for the Kattan nomogram prediction alone (K) compared to the addition of the PSAr and PSMAr in predicting 5-year RFS.

RESULTS

The mean age (years), PSA (ng/ml), and follow-up (mo) was 65.1, 9.13, and 72, respectively. The AUCs for K, PSAr + K, and PSMAr + K were 0.752 (95%CI 0.620-0.860), 0.830 (95%CI 0.740-0.911), and 0.837 (95%CI 0.613-0.923), respectively (P = 0.03). The Kattan 5-year PSA RFS was 75%. The actual 5-year PSA RFS survival rate was 77%.

CONCLUSIONS

Data from modern quantitative RT-PCR to detect circulating prostate-derived PSA and PSM mRNA pre- and post-RP improves the accuracy of the Kattan nomogram to predict biochemical recurrence.

Mechanisms and functional consequences of PDEF protein expression loss during prostate cancer progression

BACKGROUND

Ets is a large family of transcriptional regulators with functions in most biological processes. While the Ets family gene, prostate-derived epithelial factor (PDEF), is expressed in epithelial tissues, PDEF protein expression has been found to be reduced or lost during cancer progression. The goal of this study was to examine the mechanism for and biologic impact of altered PDEF expression in prostate cancer.

METHODS

PDEF protein expression of prostate specimens was examined by immunohistochemistry. RNA and protein expression in cell lines were measured by q-PCR and Western blot, respectively. Cellular growth was determined by quantifying viable and apoptotic cells over time. Cell cycle was measured by flow cytometry. Migration and invasion were determined by transwell assays. PDEF promoter occupancy was determined by chromatin immunoprecipitation (ChIP).

RESULTS

While normal prostate epithelium expresses PDEF mRNA and protein, tumors show no or decreased PDEF protein expression. Re-expression of PDEF in prostate cancer cells inhibits cell growth. PDEF expression is inversely correlated with survivin, urokinase plasminogen activator (uPA) and slug expression and ChIP studies identify survivin and uPA as direct transcriptional targets of PDEF. This study also shows that PDEF expression is regulated via a functional microRNA-204 (miR-204) binding site within the 3'UTR. Furthermore, we demonstrate the biologic significance of miR-204 expression and that miR-204 is over-expressed in human prostate cancer specimens.

CONCLUSIONS

Collectively, the reported studies demonstrate that PDEF is a negative regulator of tumor progression and that the miR-204-PDEF regulatory axis contributes to PDEF protein loss and resultant cancer progression.

Intratumoral androgen biosynthesis in prostate cancer pathogenesis and response to therapy

The majority of prostate cancers (PCa) express high levels of androgen receptor (AR) and are dependent for their growth on testosterone produced by the testes, which is reduced in the prostate to the higher affinity ligand 5α-dihydrotestosterone (DHT). PCa growth can be suppressed by androgen deprivation therapy, which involves removal of testicular androgens (surgical or medical castration) or treatment with an AR antagonist (or a combination of both), but patients invariably relapse with tumors that have been termed castration recurrent/resistant PCa (CRPC). Importantly, AR transcriptional activity becomes reactivated at this CRPC stage of the disease and remains essential for tumor growth. The objective of this review is to outline one clinically important mechanism contributing to this AR reactivation, which is increased intratumoral synthesis of testosterone and DHT from weak androgens produced by the adrenal glands and possibly de novo from cholesterol. Early studies showed that a substantial fraction of CRPC patients responded to adrenalectomy or medical suppression of adrenal androgen synthesis using agents such as ketoconazole (CYP17A1 inhibitor), and a recent phase III study of a more potent and selective CYP17A1 inhibitor (abiraterone) has demonstrated an improvement in survival. With the pending FDA approval of abiraterone for CRPC, defining the molecular mechanisms contributing to CYP17A1 inhibitor resistance/relapse and AR reactivation is now critical to build on these advances.

LNCaP Atlas: gene expression associated with in vivo progression to castration-recurrent prostate cancer

Background

There is no cure for castration-recurrent prostate cancer (CRPC) and the mechanisms underlying this stage of the disease are unknown.

Methods

We analyzed the transcriptome of human LNCaP prostate cancer cells as they progress to CRPC in vivo using replicate LongSAGE libraries. We refer to these libraries as the LNCaP atlas and compared these gene expression profiles with current suggested models of CRPC.

Results

Three million tags were sequenced using in vivo samples at various stages of hormonal progression to reveal 96 novel genes differentially expressed in CRPC. Thirty-one genes encode proteins that are either secreted or are located at the plasma membrane, 21 genes changed levels of expression in response to androgen, and 8 genes have enriched expression in the prostate. Expression of 26, 6, 12, and 15 genes have previously been linked to prostate cancer, Gleason grade, progression, and metastasis, respectively. Expression profiles of genes in CRPC support a role for the transcriptional activity of the androgen receptor (CCNH, CUEDC2, FLNA, PSMA7), steroid synthesis and metabolism (DHCR24, DHRS7, ELOVL5, HSD17B4, OPRK1), neuroendocrine (ENO2, MAOA, OPRK1, S100A10, TRPM8), and proliferation (GAS5, GNB2L1, MT-ND3, NKX3-1, PCGEM1, PTGFR, STEAP1, TMEM30A), but neither supported nor discounted a role for cell survival genes.

Conclusions

The in vivo gene expression atlas for LNCaP was sequenced and support a role for the androgen receptor in CRPC.

Expression of estrogen related proteins in hormone refractory prostate cancer: association with tumor progression

PURPOSE

Despite increasing evidence that estrogen signaling has a key role in prostate cancer development and progression, few studies have focused on the estrogen pathway in the transition from hormone sensitive to hormone refractory tumors. We investigated the expression of proteins related to androgen and estrogen metabolism in paired prostate cancer samples collected before androgen deprivation therapy and after hormonal relapse.

MATERIALS AND METHODS

The study included 55 patients treated for prostate cancer only with androgen deprivation therapy and in whom tissue was available before treatment induction and after recurrence. Immunohistochemistry was performed using tissue microarray with antibodies directed against androgen receptor, phosphorylated androgen receptor, estrogen receptor α, estrogen receptor β, 5α-reductase 1 and 2, aromatase, BCAR1 and the proliferation marker Ki67.

RESULTS

Compared to hormone sensitive samples, tissues collected after hormonal relapse were characterized by increased expression of Ki67, androgen receptor, phosphorylated androgen receptor (p <0.001) and BCAR (p = 0.03), and by lower staining for 5α-reductase 2 (p = 0.002), estrogen receptor β (p = 0.016) and aromatase (p <0.001). Shorter time to hormonal relapse was associated with high expression of aromatase and BCAR1 on diagnostic biopsy, together with low staining for estrogen receptor α in stromal cells. Overall survival was significantly shorter when tissues collected after relapse showed a high proliferation index and low estrogen receptor α expression.

CONCLUSIONS

Results revealed dysregulation of proteins involved in androgen pathways, and in estrogen synthesis and signaling during the development of hormone refractory prostate cancer.

Differential expression of the semaphorin 3A pathway in prostatic cancer

AIMS

To analyse the expression pattern of the semaphorin 3A (Sema3A) pathway, including the receptor neuropilin 1 (NRP1) and its ligands the 'antitumoral' Sema3A and the 'protumoral' vascular endothelial growth factor (VEGF)in prostatic cancer.

METHODS AND RESULTS

tissues were obtained from 120 patients treated by prostatectomy for clinically localized prostatic cancer, and 31 hormone-refractory prostatic cancer (HRPC) samples. Immunohistochemistry was performed on tissue microarrays using antibodies directed against Sema3A, NRP1 and VEGF. Moreover, real-time reverse transcriptase-polymerase chain reaction was performed on frozen prostatic tissue, including normal prostate, clinically localized tumours and HPRC. Sema3A immunoreactivity of the membrane of cancer cells was closely associated with NRP1 expression in clinically localized prostatic cancer, but not in HRPC. In clinically localized cancer, Sema3A expression correlated with lower preoperative prostate-specific antigen (PSA) and pathological stage; NRP1 reactivity was associated with lower PSA and Gleason score, and VEGF reactivity with higher PSA and Gleason score. HRPC displayed higher expression of NRP1 compared with clinically localized cancer, and lower Sema3A immunoreactivity.

CONCLUSIONS

These results support the hypothesis that dysregulation of the Sema3A pathway plays a key role in prostatic cancer progression, and suggest a loss of the inhibitory Sema3A autocrine loop in HRPC.

DNA mismatch repair and the transition to hormone independence in breast and prostate cancer

The molecular basis for the progression of breast and prostate cancer from hormone dependent to hormone independent disease remains a critical issue in the management of these two cancers. The DNA mismatch repair system is integral to the maintenance of genomic stability and suppression of tumorigenesis. No firm consensus exists regarding the implications of mismatch repair (MMR) deficiencies in the development of breast or prostate cancer. However, recent studies have reported an association between mismatch repair deficiency and loss of specific hormone receptors, inferring a potential role for mismatch repair deficiency in this transition. An updated review of the experimental data supporting or contradicting the involvement of MMR defects in the development and progression of breast and prostate cancer will be provided with particular emphasis on their implications in the transition to hormone independence.

Androgen receptor mediates the expression of UDP-glucuronosyltransferase 2 B15 and B17 genes

BACKGROUND

Enhanced androgen receptor (AR) activity by increased testosterone availability may play important roles in prostate cancer progressing to castration resistant state. Comparison of expression profiles in androgen dependent and independent prostate tumors demonstrated a marked increase of the expression of UDP-glucuronosyltransferase 2B15 (UGT2B15), an androgen catabolic enzyme. We investigated mechanisms controlling the differential expression of UGT2B15 and B17 in response to androgen treatments.

METHODS

Gene expression was determined by RT-PCR. The association of AR with UGT2B15/B17 genes was determined by Chromatin immuno-precipitation (CHIP). RNA interference was used to knock-down gene expression.

RESULTS

UGT2B15 and B17 genes were not expressed in AR negative prostate cancer cell lines, PC3 and DU145, while they were expressed in AR positive cell lines, LNCaP, LNCaP-abl (an androgen independent LNCaP sub-line), and VCaP. The expression levels of UGT2B15/B17 were up-regulated in LNCaP-abl comparing to those in LNCaP. These results suggest the requirement of AR for the expression of UGT2B15/B17. Treatment with DHT down-regulated the expression of UGT2B15/B17 in LNCaP in a time and dose dependent manner and this down-regulation was competitively antagonized by flutamide and bicalutimide, suggesting a pathway mediated by AR. Further CHIP experiments demonstrated the direct interaction of AR with the promoter regions of UGT2B15/B17 genes. Knocking down AR expression in LNCaP significantly reduced the expression of UGT2B15/B17 and completely inhibited the DHT-induced down-regulation of UGT2B15/B17 genes.

CONCLUSIONS

We demonstrated that UGT2B15 and B17 are primary androgen-regulated genes and AR is required for both their basal expression and their androgen-regulated expression.

FGFR1 and WT1 are markers of human prostate cancer progression

BACKGROUND

Androgen-independent prostate adenocarcinomas are responsible for about 6% of overall cancer deaths in men.

METHODS

We used DNA microarrays to identify genes related to the transition between androgen-dependent and androgen-independent stages in the LuCaP 23.1 xenograft model of prostate adenocarcinoma. The expression of the proteins encoded by these genes was then assessed by immunohistochemistry on tissue microarrays (TMA) including human prostate carcinoma samples issued from 85 patients who had undergone radical prostatectomy.

RESULTS

FGFR1, TACC1 and WT1 gene expression levels were associated with the androgen-independent stage in xenografts and human prostate carcinoma samples. MART1 protein expression was correlated with pT2 tumor stages.

CONCLUSION

Our results suggest that each of these four genes may play a role, or at least reflect a stage of prostate carcinoma growth/development/progression.

Quantitative multi-gene expression profiling of primary prostate cancer

BACKGROUND

This study describes the evaluation of the expression patterns of prostate-related transcripts in 106 matched prostate tissues from prostatectomies as predictors for prostate cancer (PCa).

METHODS

Quantitative PCR (QPCR) assays with site-specific hybridization probes were established for four housekeeping genes (GAPDH, HPRT, PBGD, TBP) and nine prostate-related genes (AibZIP, D-GPCR, EZH2, PCA3, PDEF, prostein, PSA, PSCA, TRPM8).

RESULTS

The relative mRNA expression levels of AibZIP, D-GPCR, EZH2, PCA3, PDEF, PSA, TRPM8 (all P < 0.001) and prostein (P = 0.019) normalized to the TBP reference gene were significantly higher in malignant compared to non-malignant prostate tissues. Employing receiver-operating characteristic (ROC) analyses, PCA3 was the best single tumor marker with the highest area-under-the-curve (AUC = 0.85). A multivariate logit model for the predictability of the tumor was developed, which employed the relative expression levels of EZH2, PCA3, prostein, and TRPM8 and yielded an AUC of 0.90.

CONCLUSIONS

The transcript marker PCA3 is a powerful predictor of primary PCa but the inclusion of EZH2, prostein, and TRPM8 adds even more to the diagnostic power. The finding of a significantly higher mRNA expression of three different genes (prostein, PSA, TRPM8) in organ-confined tumors compared to non-organ-confined tumors as well as the multi-marker PCa prediction model developed in the retrospective model system on prostatectomies could be of clinical importance for diagnostic purposes, and should be verified in diagnostic biopsies.

Increased expression of genes converting adrenal androgens to testosterone in androgen-independent prostate cancer

Androgen receptor (AR) plays a central role in prostate cancer, and most patients respond to androgen deprivation therapies, but they invariably relapse with a more aggressive prostate cancer that has been termed hormone refractory or androgen independent. To identify proteins that mediate this tumor progression, gene expression in 33 androgen-independent prostate cancer bone marrow metastases versus 22 laser capture-microdissected primary prostate cancers was compared using Affymetrix oligonucleotide microarrays. Multiple genes associated with aggressive behavior were increased in the androgen-independent metastatic tumors (MMP9, CKS2, LRRC15, WNT5A, EZH2, E2F3, SDC1, SKP2, and BIRC5), whereas a candidate tumor suppressor gene (KLF6) was decreased. Consistent with castrate androgen levels, androgen-regulated genes were reduced 2- to 3-fold in the androgen-independent tumors. Nonetheless, they were still major transcripts in these tumors, indicating that there was partial reactivation of AR transcriptional activity. This was associated with increased expression of AR (5.8-fold) and multiple genes mediating androgen metabolism (HSD3B2, AKR1C3, SRD5A1, AKR1C2, AKR1C1, and UGT2B15). The increase in aldo-keto reductase family 1, member C3 (AKR1C3), the prostatic enzyme that reduces adrenal androstenedione to testosterone, was confirmed by real-time reverse transcription-PCR and immunohistochemistry. These results indicate that enhanced intracellular conversion of adrenal androgens to testosterone and dihydrotestosterone is a mechanism by which prostate cancer cells adapt to androgen deprivation and suggest new therapeutic targets.