RhoA as a mediator of clinically relevant androgen action in prostate cancer cells

Recently, we have identified serum response factor (SRF) as a mediator of clinically relevant androgen receptor (AR) action in prostate cancer (PCa). Genes that rely on SRF for androgen responsiveness represent a small fraction of androgen-regulated genes, but distinguish benign from malignant prostate, correlate with aggressive disease, and are associated with biochemical recurrence. Thus, understanding the mechanism(s) by which SRF conveys androgen regulation to its target genes may provide novel opportunities to target clinically relevant androgen signaling. Here, we show that the small GTPase ras homolog family member A (RhoA) mediates androgen-responsiveness of more than half of SRF target genes. Interference with expression of RhoA, activity of the RhoA effector Rho-associated coiled-coil containing protein kinase 1 (ROCK), and actin polymerization necessary for nuclear translocation of the SRF cofactor megakaryocytic acute leukemia (MAL) prevented full androgen regulation of SRF target genes. Androgen treatment induced RhoA activation, increased the nuclear content of MAL, and led to MAL recruitment to the promoter of the SRF target gene FHL2. In clinical specimens RhoA expression was higher in PCa cells than benign prostate cells, and elevated RhoA expression levels were associated with aggressive disease features and decreased disease-free survival after radical prostatectomy. Overexpression of RhoA markedly increased the androgen-responsiveness of select SRF target genes, in a manner that depends on its GTPase activity. The use of isogenic cell lines and a xenograft model that mimics the transition from androgen-stimulated to castration-recurrent PCa indicated that RhoA levels are not altered during disease progression, suggesting that RhoA expression levels in the primary tumor determine disease aggressiveness. Androgen-responsiveness of SRF target genes in castration-recurrent PCa cells continued to rely on AR, RhoA, SRF, and MAL and the presence of intact SRF binding sites. Silencing of RhoA, use of Rho-associated coiled-coil containing protein kinase 1 inhibitors, or an inhibitor of SRF-MAL interaction attenuated (androgen-regulated) cell viability and blunted PCa cell migration. Taken together, these studies demonstrate that the RhoA signaling axis mediates clinically relevant AR action in PCa.

Dominant-negative androgen receptor inhibition of intracrine androgen-dependent growth of castration-recurrent prostate cancer

Background

Prostate cancer (CaP) is the second leading cause of cancer death in American men. Androgen deprivation therapy is initially effective in CaP treatment, but CaP recurs despite castrate levels of circulating androgen. Continued expression of the androgen receptor (AR) and its ligands has been linked to castration-recurrent CaP growth.

Principal Finding

In this report, the ligand-dependent dominant-negative ARΔ142–337 (ARΔTR) was expressed in castration-recurrent CWR-R1 cell and tumor models to elucidate the role of AR signaling. Expression of ARΔTR decreased CWR-R1 tumor growth in the presence and absence of exogenous testosterone (T) and improved survival in the presence of exogenous T. There was evidence for negative selection of ARΔTR transgene in T-treated mice. Mass spectrometry revealed castration-recurrent CaP dihydrotestosterone (DHT) levels sufficient to activate AR and ARΔTR. In the absence of exogenous testosterone, CWR-R1-ARΔTR and control cells exhibited altered androgen profiles that implicated epithelial CaP cells as a source of intratumoral AR ligands.

Conclusion

The study provides in vivo evidence that activation of AR signaling by intratumoral AR ligands is required for castration-recurrent CaP growth and that epithelial CaP cells produce sufficient active androgens for CaP recurrence during androgen deprivation therapy. Targeting intracrine T and DHT synthesis should provide a mechanism to inhibit AR and growth of castration-recurrent CaP.

How does health literacy affect quality of life among men with newly diagnosed clinically localized prostate cancer? Findings from the North Carolina-Louisiana Prostate Cancer Project (PCaP)

BACKGROUND

Health literacy deficits affect half of the US overall patient population, especially the elderly, and are linked to poor health outcomes among noncancer patients. Yet little is known about how health literacy affects cancer populations. The authors examined the relation between health-related quality of life (HRQOL) and health literacy among men with prostate cancer.

METHODS

Data analysis included 1581 men with newly diagnosed clinically localized prostate cancer from a population-based study, the North Carolina-Louisiana Prostate Cancer Project (PCaP). Participants completed assessment of health literacy using Rapid Estimate of Adult Literacy in Medicine (REALM) and HRQOL using the Short Form-12 General Health Survey (SF12). Bivariate and multivariate regression was used to determine the potential association between REALM and HRQOL, while controlling for sociodemographic and illness-related variables.

RESULTS

Higher health literacy level was significantly associated with better mental well-being (SF12-Mental Component Summary [MCS]; P < .001) and physical well-being (SF12-Physical Component Summary [PCS]; P < .001) in bivariate analyses. After controlling for sociodemographic (age, marital status, race, income, and education) and illness-related factors (types of cancer treatment, tumor aggressiveness, and comorbidities), health literacy remained significantly associated with SF12-MCS scores (P < .05) but not with SF12-PCS scores.

CONCLUSIONS

Among patients with newly diagnosed localized prostate cancer, those with low health literacy levels were more vulnerable to mental distress than those with higher health literacy levels, but physical well-being was no different. These findings suggest that health literacy may be important in patients managing prostate cancer and the effects of treatment, and provide the hypothesis that supportive interventions targeting patients with lower health literacy may improve their HRQOL.

Enzymatic activity of free-prostate-specific antigen (f-PSA) is not required for some of its physiological activities

BACKGROUND

Prostate specific antigen (PSA) is a well known biomarker for early diagnosis and management of prostate cancer. Furthermore, PSA has been documented to have anti-angiogenic and anti-tumorigenic activities in both in vitro and in vivo studies. However, little is known about the molecular mechanism(s) involved in regulation of these processes, in particular the role of the serine-protease enzymatic activity of PSA.

METHODS

Enzymatic activity of PSA isolated directly from seminal plasma was inhibited specifically (>95%) by incubation with zinc2+ . Human umbilical vein endothelial cells (HUVEC) were utilized to compare/contrast the physiological effects of enzymatically active versus inactive PSA.

RESULTS

Equimolar concentrations of enzymatically active PSA and PSA enzymatically inactivated by incubation with Zn2+ had similar physiological effects on HUVEC, including inhibiting the gene expression of pro-angiogenic growth factors, like VEGF and bFGF, and up-regulation of expression of the anti-angiogenic growth factor IFN-γ; suppression of mRNA expression for markers of blood vessel development, like FAK, FLT, KDR, TWIST-1; P-38; inhibition of endothelial tube formation in the in vitro Matrigel Tube Formation Assay; and inhibition of endothelial cell invasion and migration properties.

DISCUSSION

Our data provides compelling evidence that the transcriptional regulatory and the anti-angiogenic activities of human PSA are independent of the innate enzymatic activity.

Racial/ethnic differences in receipt of pelvic lymph node dissection among men with localized/regional prostate cancer

BACKGROUND

Black and Hispanic men have a lower prostate cancer (PCa) survival rate than white men. This racial/ethnic survival gap has been explained in part by differences in tumor characteristics, stage at diagnosis, and disparities in receipt of definitive treatment. Another potential contributing factor is racial/ethnic differences in the timely and accurate detection of lymph node metastases. The current study was conducted to examine the association between race/ethnicity and the receipt of pelvic lymph node dissection (PLND) among men with localized/regional PCa.

METHODS

Logistic regression was used to estimate the adjusted odds of undergoing PLND among men who were diagnosed during 2000 to 2002 with PCa, who underwent radical prostatectomy or PLND without radical prostatectomy, and who were diagnosed in regions covered by the Surveillance, Epidemiology, and End Results database (n = 40,848).

RESULTS

Black men were less likely to undergo PLND than white men (odds ratio [OR], 0.91; 95% confidence interval [CI], 0.84-0.98). When the analysis was stratified by PCa grade, black men with well differentiated PCa (OR, 0.48; 95% CI, 0.27-0.84) and poorly differentiated PCa (OR, 0.73; 95% CI, 0.60-0.89) were less likely to undergo PLND than their white counterparts, but racial differences were not observed among men with moderately differentiated PCa (OR, 0.96; 95% CI, 0.88-1.05).

CONCLUSIONS

Among men with poorly differentiated PCa, failure to undergo PLND was associated with worse survival. Racial disparities in the receipt of PLND, especially among men with poorly differentiated PCa, may contribute to racial differences in prostate cancer survival.

Abstract B81: Vitamin D and prostate cancer aggressiveness among African and European Americans in the North Carolina-Louisiana Prostate Cancer Project (PCaP) case study cohort

25(OH) vitamin D3 [25D3] serum levels have been associated with increased risk and unfavorable outcomes in several types of cancer, including breast, bladder, lung, and colon cancer. The relationship between vitamin D and prostate cancer prognosis and outcome is less well-studied. This pilot study utilized 200 samples from the North Carolina-Louisiana Prostate Cancer Project (PCaP) cohort to investigate the association between circulating 25D3 levels and an aggressive phenotype of prostate cancer in 100 African American (AA) and 100 European American (EA) men.

Plasma vitamin D levels were categorized as deficient ≤20 ng/ml, insufficient ≤30 and &gt;20 ng/ml, and sufficient &gt;30ng/ml. The mean value of plasma vitamin D levels in the 200 research subjects was 24.7 ng/ml (STD 11.0, minimum value 6.3, and maximum value 62), which indicated vitamin D deficiency and insufficiency in a large portion of patients. AA men were more likely than EA men to present with vitamin D deficiency, which may be due to differences in skin pigmentation. As expected, significant (P &lt;.0001) differences in vitamin D serum levels were found between AA men (mean value of 20.9 ng/ml) and EA men (mean value of 28.4 ng/ml). AA men with prostate cancer often present with vitamin D deficiency.

Prostate tumor aggressiveness was categorized by PCaP as high, low, and intermediate, using clinical grade, clinical stage, and serum PSA at diagnosis [High aggressive: clinical stage ≥ T3 and Gleason grade ≥ 7 or Gleason sum ≥ 8 or PSA &gt; 20; Low: Gleason sum &lt; 7 and clinical stage ≤ T2 and PSA &lt; 10]. An equal number of high aggressive (100 cases) and low aggressive (100 cases) tumors were included in the analysis. We then analyzed the relationship between vitamin D serum levels and prostate cancer aggressiveness. There was no significant correlation between disease aggressiveness and plasma concentrations of vitamin D. However, a significant inverse relationship was found between vitamin D and PSA levels (P=.0008). A trend was observed in which vitamin D deficient (&lt;20ng/ml) AA men were diagnosed with more aggressive prostate cancer than AA men who were either vitamin D insufficient or sufficient. Specifically, out of 100 AA men with prostate cancer 59 were 25D3 deficient. Of these, over 50 percent had tumors classified as high aggressive. A similar trend was not observed among EA men. We controlled for season of blood collection: EA men had their lowest levels of circulating vitamin D during winter. Seasonal differences were not observed among AA men.

This pilot study will be extended to the entire PCaP cohort of 2256 men in order to confirm these observations. In addition, we will continue to investigate the role of diet and dietary supplements on vitamin D levels in the PCaP cohort. Further analyses will add racial admixture estimates into our models in order to correct for population stratification. This is necessary since self-identified race may or may not reflect ancestral origins accurately.

Acknowledgments: The authors thank the North Carolina Central Cancer Registry, the Louisiana Tumor Registry, and the PCaP staff, advisory committees and participants for their important contributions. The Prostate Cancer Project (PCaP) is carried out as a collaborative study supported by the Department of Defense contract DAMD 17-03-2-0052. AWR is supported by the Department of Defense grant W81WH11-1-0308 and R25CA113951-01 grant from the National Cancer Institute.

Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):B81.

5α-reductase type 3 expression in human benign and malignant tissues: a comparative analysis during prostate cancer progression

BACKGROUND

A third isozyme of human 5α-steroid reductase, 5α-reductase-3, was identified in prostate tissue at the mRNA level. However, the levels of 5α-reductase-3 protein expression and its cellular localization in human tissues remain unknown.

METHODS

A specific monoclonal antibody was developed, validated, and used to characterize for the first time the expression of 5α-reductase-3 protein in 18 benign and 26 malignant human tissue types using immunostaining analyses.

RESULTS AND CONCLUSIONS

In benign tissues, 5α-reductase-3 immunostaining was high in conventional androgen-regulated human tissues, such as skeletal muscle and prostate. However, high levels of expression also were observed in non-conventional androgen-regulated tissues, which suggest either multiples target tissues for androgens or different functions of 5α-reductase-3 among human tissues. In malignant tissues, 5α-reductase-3 immunostaining was ubiquitous but particularly over-expressed in some cancers compared to their benign counterparts, which suggests a potential role for 5α-reductase-3 as a biomarker of malignancy. In benign prostate, 5α-reductase-3 immunostaining was localized to basal epithelial cells, with no immunostaining observed in secretory/luminal epithelial cells. In high-grade prostatic intraepithelial neoplasia (HGPIN), 5α-reductase-3 immunostaining was localized in both basal epithelial cells and neoplastic epithelial cells characteristic of HGPIN. In androgen-stimulated and castration-recurrent prostate cancer (CaP), 5α-reductase-3 immunostaining was present in most epithelial cells and at similar levels, and at levels higher than observed in benign prostate. Analyses of expression and functionality of 5α-reductase-3 in human tissues may prove useful for development of treatment for benign prostatic enlargement and prevention and treatment of CaP.

Potential prostate cancer drug target: bioactivation of androstanediol by conversion to dihydrotestosterone

High-affinity binding of dihydrotestosterone (DHT) to the androgen receptor (AR) initiates androgen-dependent gene activation, required for normal male sex development in utero, and contributes to prostate cancer development and progression in men. Under normal physiologic conditions, DHT is synthesized predominantly by 5α-reduction of testosterone, the major circulating androgen produced by the testis. During androgen deprivation therapy, intratumoral androgen production is sufficient for AR activation and prostate cancer growth, even though circulating testicular androgen levels are low. Recent studies indicate that the metabolism of 5α-androstane-3α, 17β-diol by 17β-hydroxysteroid dehydrogenase 6 in benign prostate and prostate cancer cells is a major biosynthetic pathway for intratumoral synthesis of DHT, which binds AR and initiates transactivation to promote prostate cancer growth during androgen deprivation therapy. Drugs that target the so-called backdoor pathway of DHT synthesis provide an opportunity to enhance clinical response to luteinizing-hormone-releasing hormone (LHRH) agonists or antagonists, AR antagonists, and inhibitors of 5α-reductase enzymes (finasteride or dutasteride), and other steroid metabolism enzyme inhibitors (ketoconazole or the recently available abiraterone acetate).

GWAS SNP Replication among African American and European American men in the North Carolina-Louisiana prostate cancer project (PCaP)

BACKGROUND

Genome-wide association studies (GWAS) have identified numerous common SNPs associated with prostate cancer (CaP) risk in men of European descent. This study evaluates GWAS SNPs associated with CaP in African Americans (AAs) and European Americans (EA).

METHODS

Eight hundred SNPs were genotyped, including 32 from European-based GWAS and 35 flanking SNPs, in 417 AA and 455 EA cases from the NC-LA Prostate Cancer Project (PCaP) and compared to 925 AA and 1,687 EA controls from Illumina's iControlDB. The 32 GWAS SNPs were evaluated for their predictive power to discriminate between cases and controls using ROC curves.

RESULTS

Of the 32 GWAS SNPs, 13 were significant at P < 0.05 in EA and 4 in AA (rs6983267, rs7017300, rs1859962, rs6501455). Three of 35 flanking SNPs, all from chromosome 8q, reached study-wide significance (P < 3.5 × 10(-5)); 2 in AA (rs10505476 rs6985504) and 1 in EA (rs16901970). Among the remaining 656 SNPs, 2 were associated with CaP (P < 3.5 × 10(-5)): rs1472606 (OR: 1.43 in EA) and rs9351265 (OR: 1.48 in AA) both in intergenic regions. For the 32 GWAS SNPs, ROC plots yielded AUC estimates too low for clinical use (EA AUC = 0.60 and AA AUC = 0.56).

CONCLUSIONS

This study confirms a large proportion of CaP associated regions implicated by European-based GWAS and provides evidence that some regions may be important in AA CaP risk. Despite the identification of a large panel of GWAS replicated SNPs for CaP, this panel is not appropriate for clinical screening.

Abstract 4664: The effect of neoadjuvant androgen deprivation therapy on long-term outcome after radical prostatectomy

Neoadjuvant androgen deprivation therapy (NADT) was championed for men treated with radical prostatectomy (RP) for high risk prostate cancer (CaP) in the early 1990s. Although NADT improved neither surgical margin positivity nor progression-free survival, it continues to be part of some clinical trials. The effect of NADT on long term outcome was evaluated using modern aggressiveness and failure criteria among 720 patients treated with RP at Roswell Park Cancer Institute between 1993 and 2005. Among RP patients, 125 received NADT. NCCN pre-surgery risk categories were low in 36 (29%), intermediate in 54 (43%), and high or very high in 35 (28%). Clinical and pathological aggressiveness indicators included clinical Gleason sum, clinical tumor stage (2002 TNM), highest preoperative PSA, pathological Gleason sum, pathological tumor stage (2002 TNM) and surgical margin status. Ten post-RP recurrence definitions were considered: 1) at least 1 detectable PSA, 2) at least 2 detectable PSAs, 3) PSA&gt;0.2 ng/ml, 4) PSA&gt;0.4 ng/ml, 5) at least 1 post RP treatment (chemotherapy, hormone, radiation), 6) PSA doubling time &lt;9 months, 7) NCCN definition of failure, 8) AUA definition of failure, 9) development of metastatic CaP, 10) death from CaP. In bivariate analysis, men treated with NADT were 105% (p&lt;0.0001) more likely to fail using the AUA definition, 202% (p=0.004) more likely to develop metastatic CaP, and 673% (p=0.001) more likely to die of CaP. The increased risk of recurrence persisted for NADT in multivariate analysis, despite control for all clinical and pathological parameters; the table shows data for clinical and pathological parameters that have been associated with RP failure. Analysis of hazards regression for AUA failure across NCCN risk category demonstrated that NADT was detrimental for men treated with RP, regardless of any level of risk.

Obesity and prostate cancer aggressiveness among African and Caucasian Americans in a population-based study

BACKGROUND

This study evaluated obesity and prostate cancer aggressiveness relationship in a population-based incident prostate cancer study.

METHODS

The North Carolina-Louisiana Prostate Cancer Project includes medical records data for classification of prostate cancer aggressiveness at diagnosis by using clinical criteria for 1,049 African American (AA) and 1,083 Caucasian American (CA) participants. An association between prostate cancer aggressiveness and obesity, measured using body mass indices (BMI) and waist-to-hip ratio (WHR), was assessed using ORs and 95% CIs adjusted for confounders.

RESULTS

A significantly positive association was found between prostate cancer aggressiveness and obesity. The ORs for high aggressive prostate cancer among prediagnosis obese and severely obese were 1.48 (95% CI = 1.02-2.16) and 1.98 (95% CI = 1.31-2.97), respectively, compared with normal weight research subjects. Race-stratified results suggested the association is stronger among CAs. Interaction model showed that normal weight AAs had more aggressive prostate cancer than normal weight CAs (OR = 2.69, 95% CI = 1.36-5.30); severe obesity was associated with aggressive disease in AAs (OR = 3.90, 95% CI = 1.97-7.75). WHR > 0.98 among all research subjects adjusted for race was significantly associated with high aggressive prostate cancer (OR = 1.42, 95% CI = 1.00-2.00) when compared with WHR < 0.90. The stratified result is less clear among AAs.

CONCLUSIONS

This study shows a positive association between obesity and aggressive prostate cancer. AAs have more aggressive prostate cancer in general than CAs even at normal weight. Therefore, the association between obesity and aggressiveness is not as evident in AAs as in CAs.

IMPACT

This study provides a unique opportunity to examine impact of race on obesity and high aggressive prostate cancer relationship.

Activation of the androgen receptor by intratumoral bioconversion of androstanediol to dihydrotestosterone in prostate cancer

The androgen receptor (AR) mediates the growth of benign and malignant prostate in response to dihydrotestosterone (DHT). In patients undergoing androgen deprivation therapy for prostate cancer, AR drives prostate cancer growth despite low circulating levels of testicular androgen and normal levels of adrenal androgen. In this report, we demonstrate the extent of AR transactivation in the presence of 5α-androstane-3α,17β-diol (androstanediol) in prostate-derived cell lines parallels the bioconversion of androstanediol to DHT. AR transactivation in the presence of androstanediol in prostate cancer cell lines correlated mainly with mRNA and protein levels of 17β-hydroxysteroid dehydrogenase 6 (17β-HSD6), one of several enzymes required for the interconversion of androstanediol to DHT and the inactive metabolite androsterone. Levels of retinol dehydrogenase 5, and dehydrogenase/reductase short-chain dehydrogenase/reductase family member 9, which also convert androstanediol to DHT, were lower than 17β-HSD6 in prostate-derived cell lines and higher in the castration-recurrent human prostate cancer xenograft. Measurements of tissue androstanediol using mass spectrometry demonstrated androstanediol metabolism to DHT and androsterone. Administration of androstanediol dipropionate to castration-recurrent CWR22R tumor-bearing athymic castrated male mice produced a 28-fold increase in intratumoral DHT levels. AR transactivation in prostate cancer cells in the presence of androstanediol resulted from the cell-specific conversion of androstanediol to DHT, and androstanediol increased LAPC-4 cell growth. The ability to convert androstanediol to DHT provides a mechanism for optimal utilization of androgen precursors and catabolites for DHT synthesis.

Androgen deprivation induces rapid involution and recovery of human prostate vasculature

The response of the prostate tissue microenvironment to androgen deprivation (AD) represents a critical component in the treatment of benign prostatic hyperplasia and prostate cancer (CaP). Primary xenografts of human benign and CaP tissue transplanted to immunocompromized SCID mice were used to characterize the response of the prostate vasculature during the initial 14 days of AD. Microvessel density and vascular lumen diameter in the prostate xenografts decreased rapidly after AD, reached a nadir on days 2-4, and recovered between days 4 and 14. The number of apoptotic endothelial cells peaked on day 2 after AD and decreased to precastration levels over days 4-7. Leakage of vascular contents in the interstitial space was apparent between days 1 and 3 after AD; however, the vascular permeability barrier reestablished between days 7 and 14. Expression of vascular endothelial growth factor (VEGF)-A, VEGF receptor-2, and basic fibroblast growth factor protein increased in endothelial cells between days 2 and 4 after AD, which preceded vascular recovery and appeared to be a direct and specific response of the endothelial cells to AD. Lack of comparable upregulation of these genes in primary cultures of human prostate endothelial cells in response to AD suggests a role for paracrine signaling mediated through stromal or epithelial cells. VEGF-A expression by prostate endothelial cells appears to represent a key facilitator of the vascular rebound in human prostate tissue induced by removal of circulating testicular androgens.

Manual and automated systems in the analysis of images from prostate tissue microarray cores

OBJECTIVE

To compare manual and automated image analysis systems in morphologic analysis of nuclei from benign prostate, high-grade prostatic intraepithelial neoplasia (HGPIN) and prostate cancer (CaP). Morphologic features derived using automated image analysis systems may be more objective and reproducible than manual systems, which require humans to segment nuclei from histologic images.

STUDY DESIGN

Images of hematoxylin-eosin-stained sections of prostate tissue microarray were analyzed independently using the automated and manual systems. Mean optical density (MOD), nuclear area (NA), and nuclear roundness factor (NRF) were the morphologic features studied. The ability to differentiate between tissue types using morphologic features derived from an automated and a manual system was compared.

RESULTS

Nuclei from 17 benign prostate hyperplasia (BPH), 4 HGPIN, and 8 aggressive CaP were analyzed. The manual system distinguished better between BPH and HGPIN (p < 0.0001), whereas the automated system distinguished better between BPH and CaP (p = 0.01) in multivariate models. The manual system distinguished better BPH and HGPIN using NA (p < 0.0001) and MOD (p < 0.0001), whereas the automated system distinguished better BPH and CaP using MOD (p < 0.0001) and NRF (p = 0.004).

CONCLUSION

The minimal human effort required for automated image analysis makes it superior to the manual system.

Variability in visual segmentation of digitized prostate tissue microarray cores

OBJECTIVE

To examine bias associated with human-interactive semi-automated systems key components with machine vision used in quantitative histometry.

STUDY DESIGN

A standard image set of 20 images was created using 5 nuclei sampled from hematoxylin-eosin-stained sections of benign tissue within a prostate tissue microarray that were rotated through the cardinal directions. Four trained technicians performed segmentation of these images at the start, then at the end, of 3 daily sessions, creating a total analytic set of 480 observations. Measurements of nuclear area (NA), nuclear roundness factor (NRF), and mean optical density (MOD) were compared by segmenter, time, and rotational orientation.

RESULTS

NA varied significantly among sessions (p < 0.0009) and session variance differed within segmenter (p < 0.0001). NRF was significant among segmenters (p < 0.001) and sessions (p < 0.0001), and in session (p < 0.0001) and intra-session differences (p = 0.026). Differences in MOD varied among sessions (p < 0.0001) and within sessions (p < 0.049).

CONCLUSION

Imaging systems remain vulnerable to statistical inter-segmenter variation, in spite of extensive efforts to eliminate variation among individual segmenters. As statistical significance often guides decision-making in morphometric analysis, statistically significant effects potentially produce bias. Current practices and quality assurance methods require review to eliminate individual operator effects in semiautomated machine systems.

Androgen receptor-mTOR crosstalk is regulated by testosterone availability: implication for prostate cancer cell survival

BACKGROUND

Signaling between androgen receptor (AR) and mTOR may be crucial for prostate cancer cells to endure the low androgen and suboptimal nutrient conditions produced by androgen deprivation therapy.

MATERIALS AND METHODS

AR and mTOR cross-talk was examined in LNCaP cells exposed to either high or low testosterone. AR and mTOR activities were modified separately using either siRNA knockdown or specific chemical inhibitor. The biological significance of the reciprocal communication was assessed by susceptibility to glucose deprivation-induced cell death.

RESULTS

AR positively regulated mTOR activity in both low and high testosterone levels. TSC1 and TSC2, the two negative regulators of mTOR, may be involved since both were up-regulated by AR knockdown. Sub-baseline mTOR increased AR protein levels. However, this effect only occurred with low testosterone. More cells underwent apoptosis if AR function was inhibited during glucose deprivation, which significantly depressed mTOR activity.

CONCLUSION

The compensatory increase of AR function due to a repressed mTOR signal is advantageous for survival. Disrupting this loop at the time of initiation of androgen deprivation therapy may delay, or even prevent, the recurrence of prostate cancer.

Atmospheric pressure photoionization tandem mass spectrometry of androgens in prostate cancer

Androgen deprivation therapy is the most common treatment option for advanced prostate cancer. Almost all prostate cancers recur during androgen deprivation therapy, and new evidence suggests that androgen receptor activation persists despite castrate levels of circulating androgens. Quantitation of tissue levels of androgens is critical to understanding the mechanism of recurrence of prostate cancer during androgen deprivation therapy. A liquid chromatography atmospheric pressure photoionization tandem mass spectrometric method was developed for quantitation of tissue levels of androgens. Quantitation of the saturated keto-steroids dihydrotestosterone and 5-alpha-androstanedione required detection of a novel parent ion, [M + 15](+). The nature of this parent ion was explored, and the method was applied to prostate tissue and cell culture with comparison to results achieved using electrospray ionization.

The transcriptomics of de novo androgen biosynthesis in prostate cancer cells following androgen reduction

The progression of prostate cancer to the castration-recurrent phenotype remains a major problem medically. The present study examined the transcriptomics of de novo androgen synthesis as a potential mechanism to escape from dependence on circulating androgen. VCaP, LNCaP and LAPC4 cells were acclimated to 1 nM testosterone for five generations before subjecting them to a reduced level of 0.03 nM testosterone. Changes in gene expression were quantified using qRT-PCR. Analyses of the cholesterol biosynthesis pathway and the Δ4, Δ5 and backdoor steroidogenic pathways were carried out. VCaP cells showed no change in the transcriptome of cholesterol biosynthesis. However, several receptors for cholesterol transport were upregulated. The Δ4 and Δ5 steroidogenic pathways, but not the backdoor pathway, were stimulated. Additionally, androgen receptor (AR) expression was increased. Taken together, the above changes might allow recovery of AR activity to a near normal level. In contrast, LNCaP cells showed only minimal adjustment in the transcriptome of steroidogenesis. LAPC4 cells were equally unresponsive to boosting the machinery of androgen production. In brief, our results suggest that the VCaP model is an appropriate model for further investigation of targeting the androgen-AR axis to block the emergence of castration-resistant prostate cancer.

Survival advantage of AMPK activation to androgen-independent prostate cancer cells during energy stress

Androgen-independent prostate cancer usually develops as a relapse following androgen ablation therapy. Removing androgen systemically causes vascular degeneration and nutrient depletion of the prostate tumor tissue. The fact that the malignancy later evolves to androgen-independence suggests that some cancer cells are able to survive the challenge of energy/nutrient deprivation. AMP-activated protein kinase (AMPK) is an important manager of energy stress. The present study was designed to investigate the role of AMPK in contributing to the survival of the androgen-independent phenotype. Most of the experiments were carried out in the androgen-dependent LNCaP cells and the androgen-independent C4-2 cells. These two cell lines have the same genetic background, since the C4-2 line is derived from the LNCaP line. Glucose deprivation (GD) was instituted to model energy stress encountered by these cells. The key findings are as follows. First, the activation of AMPK by GD was much stronger in C4-2 cells than in LNCaP cells, and the robustness of AMPK activation was correlated favorably with cell viability. Second, the response of AMPK was specific to energy deficiency rather than to amino acid deficiency. The activation of AMPK by GD was functional, as demonstrated by appropriate phosphorylation changes of mTOR and mTOR downstream substrates. Third, blocking AMPK activation by chemical inhibitor or dominant negative AMPK led to increased apoptotic cell death. The observation that similar results were found in other androgen-independent prostate cancer cell lines, including CW22Rv1 abd VCaP, provided further assurance that AMPK is a facilitator on the road to androgen-independence of prostate cancer cells.

A method for using life tables to estimate lifetime risk for prostate cancer death

Prostate cancer can have a long and indolent course, and management without curative therapy should be considered in select patients. When counseling patients, a useful way to convey the risk for death from competing causes is to estimate their lifetime risk for dying from prostate cancer. Double-decrement life tables were constructed to calculate age-specific death rates using the death probabilities from the Social Security Administration life tables and Gleason score-specific mortality rates reported from a pre-PSA cohort study. The lifetime risk for prostate cancer death was calculated. Life tables provided life expectancy and risk for prostate cancer death based on age at diagnosis. For example, a 60-year-old patient with a Gleason score 6, 7, or 8 tumor had an overall life expectancy of 14.4, 10.2, or 6.6 years, respectively. The risk for prostate cancer death during the expected years of life was 33%, 49%, or 57%, respectively. If a 10-year lead-time bias was assumed for PSA detection, the risks for death from prostate cancer decreased to 16%, 26%, or 37%, respectively. If the patient was in the bottom quartile for overall health and disease was detected by prostate examination, the risk for death from prostate cancer was 21%, 32%, or 40%, respectively. A Web-based tool for performing these calculations is available at http://www.roswellpark.org/Patient_Care/Specialized_Services/Prostate_Cancer_Estimator.html. Life tables can be created to estimate overall life expectancy and risk for prostate cancer death, and to assist with decision-making when considering management without curative therapy.

Abstract 4900: MAGE-A11 expression in castration-recurrent prostate cancer: association with a global epigenetic defect

Despite the initial clinical response to androgen deprivation therapy, most prostate cancer patients subsequently develop castration-recurrent disease. Elucidation of the mechanisms driving this process is expected to lead to improved strategies to prevent and treat advanced prostate cancer. Epigenetic alterations, including DNA hypomethylation, play a key role in human cancer development. DNA hypomethylation is thought to promote oncogenesis in part by driving oncogene expression, but its potential role in castration-recurrent prostate cancer is unknown. Melanoma Antigen A-11 (MAGE-A11) is a cancer germline (CG) antigen that stabilizes the androgen receptor (AR), facilitates AR association with co-activators, and promotes AR transcriptional activity; thus it appears to play an oncogenic role in castration-recurrent disease. We have recently reported that MAGE-A11 is over-expressed in prostate cancer cell lines, prostate cancer xenografts, and human prostate cancer tissues; in each setting MAGE-A11 overexpression is associated with DNA hypomethylation at the MAGE-A11 promoter CpG island (Karpf et al., Molecular Cancer Research 7; 523-535, 2009). Critically, MAGE-A11 expression and promoter hypomethylation correlate with castration-recurrent cancer growth, both in the CWR-22 xenograft model and in primary human prostate cancer tissues. In the current study we examined whether MAGE-A11 expression and hypomethylation in prostate cancer is an isolated molecular event, or alternatively whether it coincides with a global DNA hypomethylation defect. To test this, we analyzed the global DNA methylation status of prostate cancer cell lines, CWR-22 cancer xenografts, and primary prostate cancer, in which MAGE-A11 expression and methylation was also characterized. We assessed global DNA methylation by measuring total genomic 5-methyl-2′-deoxycytidine (5mdC), LINE-1 repetitive DNA element methylation, and the expression and methylation of several other CG antigen genes, including MAGE-A1, NY-ESO-1, XAGE-1, and BORIS/CTCFL. Taken together, our data provide evidence for a global DNA hypomethylation phenotype in castration-recurrent prostate cancers that express MAGE-A11. Ongoing studies are using HpaII tiny fragment enrichment by ligation-mediated PCR (HELP assay) to define the epigenome of castration-recurrent prostate cancer displaying MAGE-A11 expression. In summary, our data provide evidence that global DNA hypomethylation contributes to castration-recurrent prostate cancer, at least in part by promoting MAGE-A11 expression.

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 4900.