Showing papers by "William G. Nelson published in 2014"

Chronic Inflammation in Benign Prostate Tissue Is Associated with High-Grade Prostate Cancer in the Placebo Arm of the Prostate Cancer Prevention Trial

Abstract: Background: Chronic inflammation is hypothesized to influence prostate cancer development, although a definitive link has not been established. Methods: Prostate cancer cases ( N = 191) detected on a for-cause (clinically indicated) or end-of-study (protocol directed) biopsy, and frequency-matched controls ( N = 209), defined as negative for cancer on an end-of-study biopsy, were sampled from the placebo arm of the Prostate Cancer Prevention Trial. Inflammation prevalence and extent in benign areas of biopsy cores were visually assessed using digital images of hematoxylin and eosin–stained sections. Logistic regression was used to estimate associations. Results: Of note, 86.2% of cases and 78.2% of controls had at least one biopsy core (of three assessed) with inflammation in benign areas, most of which was chronic. Men who had at least one biopsy core with inflammation had 1.78 [95% confidence interval (CI), 1.04–3.06] times the odds of prostate cancer compared with men who had zero cores with inflammation. The association was stronger for high-grade disease (Gleason sum 7–10, N = 94; OR, 2.24; 95% CI, 1.06–4.71). These patterns were present when restricting to cases and controls in whom intraprostatic inflammation was the least likely to have influenced biopsy recommendation because their prostate-specific antigen (PSA) was low (<2 ng/mL at biopsy). Conclusion: Inflammation, most of which was chronic, was common in benign prostate tissue, and was positively associated with prostate cancer, especially high grade. The association did not seem to be due to detection bias. Impact: This study supports an etiologic link between inflammation and prostate carcinogenesis, and suggests an avenue for prevention by mitigating intraprostatic inflammation. Cancer Epidemiol Biomarkers Prev; 23(5); 847–56. ©2014 AACR .

Epigenetic DNA methylation of antioxidative stress regulator NRF2 in human prostate cancer.

Abstract: Epigenetic control of NRF2, a master regulator of many critical antioxidative stress defense genes in human prostate cancer (CaP), is unknown. Our previous animal study found decreased Nrf2 expression through promoter CpG methylation/histone modifications during prostate cancer progression in TRAMP mice. In this study, we evaluated CpG methylation of human NRF2 promoter in 27 clinical prostate cancer samples and in LNCaP cells using MAQMA analysis and bisulfite genomic DNA sequencing. Prostate cancer tissue microarray (TMA) containing normal and prostate cancer tissues was studied by immunohistochemistry. Luciferase reporter assay using specific human NRF2 DNA promoter segments and chromatin immunoprecipitation (ChIP) assay against histone modifying proteins were performed in LNCaP cells. Three specific CpG sites in the NRF2 promoter were found to be hypermethylated in clinical prostate cancer samples (BPH

Racial variation in sex steroid hormone concentration in black and white men: a meta-analysis.

Abstract: Sex steroid hormones are associated with chronic diseases and mortality with risk associations that differ between racial and ethnic groups. However, it is currently unclear whether sex steroid hormone levels differ between black and white men. The aim of this study was to assess racial variation in circulating testosterone, free testosterone, sex hormone-binding globulin (SHBG) and estradiol levels in men. We searched PubMed for articles comparing circulating hormones in black and white men. A meta-analysis was performed using weighted mean differences (WMD) to compare hormones levels between black and white men. Fifteen eligible studies were identified; three did not report adjusted means. After age adjustment, free testosterone levels were significantly higher in black than in white men (WMD = 4.07 pg/mL, 95% CI 1.26, 6.88). Depending on the free testosterone concentration in white men, this WMD translates into a racial difference ranging from 2.5 to 4.9%. Total testosterone (WMD = 0.10 ng/mL, 95% CI -0.02, 0.22), estradiol (WMD = 0.67 pg/mL, 95% CI -0.04, 1.38) and SHBG (WMD = -0.45 nmol/L, 95% CI -1.75, 0.85) concentrations did not differ comparing blacks with whites. After adjustment for age, black men have a modestly but significantly 2.5 to 4.9% higher free testosterone level than white men. Based on previous studies on effects of sex steroid hormones on risk of chronic diseases or mortality, this modest difference is unlikely to explain racial differences in disease risk.

The Diet as a Cause of Human Prostate Cancer

Abstract: Asymptomatic prostate inflammation and prostate cancer have reached epidemic proportions among men in the developed world. Animal model studies implicate dietary carcinogens, such as the heterocyclic amines from over-cooked meats and sex steroid hormones, particularly estrogens, as candidate etiologies for prostate cancer. Each acts by causing epithelial cell damage, triggering an inflammatory response that can evolve into a chronic or recurrent condition. This milieu appears to spawn proliferative inflammatory atrophy (PIA) lesions, a type of focal atrophy that represents the earliest of prostate cancer precursor lesions. Rare PIA lesions contain cells which exhibit high c-Myc expression, shortened telomere segments, and epigenetic silencing of genes such as GSTP1, encoding the π-class glutathione S-transferase, all characteristic of prostatic intraepithelial neoplasia (PIN) and prostate cancer. Subsequent genetic changes, such as the gene translocations/deletions that generate fusion transcripts between androgen-regulated genes (such as TMPRSS2) and genes encoding ETS family transcription factors (such as ERG1), arise in PIN lesions and may promote invasiveness characteristic of prostatic adenocarcinoma cells. Lethal prostate cancers contain markedly corrupted genomes and epigenomes. Epigenetic silencing, which seems to arise in response to the inflamed microenvironment generated by dietary carcinogens and/or estrogens as part of an epigenetic “catastrophe” affecting hundreds of genes, persists to drive clonal evolution through metastatic dissemination. The cause of the initial epigenetic “catastrophe” has not been determined but likely involves defective chromatin structure maintenance by over-exuberant DNA methylation or histone modification. With dietary carcinogens and estrogens driving pro-carcinogenic inflammation in the developed world, it is tempting to speculate that dietary components associated with decreased prostate cancer risk, such as intake of fruits and vegetables, especially tomatoes and crucifers, might act to attenuate the ravages of the chronic or recurrent inflammatory processes. Specifically, nutritional agents might prevent PIA lesions or reduce the propensity of PIA lesions to suffer “catastrophic” epigenome corruption.

Time-Resolved Fluorescence Resonance Energy Transfer Assay for Discovery of Small-Molecule Inhibitors of Methyl-CpG Binding Domain Protein 2

Abstract: Methylated DNA binding proteins such as Methyl-CpG Binding Domain Protein 2 (MBD2) can transduce DNA methylation alterations into a repressive signal by recruiting transcriptional co-repressor complexes. Interfering with MBD2 could lead to reactivation of tumor suppressor genes and therefore represents an attractive strategy for epigenetic therapy. We developed and compared fluorescence polarization (FP) and time-resolved fluorescence resonance energy transfer (TR-FRET)-based high-throughput screening (HTS) assays to identify small-molecule inhibitors of the interaction between the methyl binding domain of MBD2 (MBD2-MBD) and methylated DNA. Although both assays performed well in 96-well format, the TR-FRET assay (Z' factor = 0.58) emerged as a superior screening strategy compared with FP (Z' factor = 0.08) when evaluated in an HTS 384-well plate format. Using TR-FRET, we screened the Sigma LOPAC library for MBD2-MBD inhibitors and identified four compounds that also validated in a dose-response series. This included two known DNA intercalators (mitoxantrone and idarubicin) among two other inhibitory compounds (NF449 and aurintricarboxylic acid). All four compounds also inhibited the binding of SP-1, a transcription factor with a GC-rich binding sequence, to a methylated oligonucleotide, demonstrating that the activity was nonspecific. Our results provide proof of principle for using TR-FRET-based HTS to identify small-molecule inhibitors of MBD2 and other DNA-protein interactions.

Association of serum inorganic phosphate with sex steroid hormones and vitamin D in a nationally representative sample of men.

Abstract: Defects in bone regulatory pathways have been linked to chronic diseases including cardiovascular disease and cancer. In men, a link between bone metabolism and gonadal hormones has been suggested. However, to date, there is lack of evidence on the association between serum inorganic phosphate (Pi) and sex steroid hormones. The objective of this study was to investigate the association between Pi, sex steroid hormones and a known Pi metabolic regulator, vitamin D, in men in the National Health and Nutrition Examination Survey III (NHANES III). From NHANES III, we selected 1412 men aged 20+ who participated in the morning session of Phase I (1988-1991) with serum measurements of Pi, sex hormones, and vitamin D. Multivariable linear regression was used to calculate crude and geometric mean Pi by total and estimated free testosterone and estradiol, sex hormone-binding globulin, androstanediol glucuronide (AAG), and vitamin D. Similar analyses were performed while stratifying by race/ethnicity and vitamin D levels. We found a lack of statistically significant difference in geometric means of Pi across quintiles of concentrations of sex hormones, indicating a tight regulation of Pi. However, Pi levels were inversely associated with calculated free testosterone in non-Hispanic black men, with geometric mean levels of Pi of 1.16 and 1.02 ng/mL for those in the lowest and highest quintiles of free testosterone, respectively (p-trend < 0.05). A similar but weaker pattern was seen between total testosterone and Pi. An inverse association was also seen between AAG and Pi in men with vitamin D concentration below the median (<24.2 ng/mL). No associations were observed among men with vitamin D levels at or above the median. Our findings suggest a weak link among sex hormones, vitamin D, and Pi in men. The observed effects of race/ethnicity and vitamin D indicate a complex association involving various regulators of Pi homeostasis.

A panel of DNA methylation markers reveals extensive methylation in histologically benign prostate biopsy cores from cancer patients.

Abstract: Background Men with a negative first prostate biopsy will undergo one or more additional biopsies if they remain at high suspicion of prostate cancer. To date, there are no diagnostic tests capable of identifying patients at risk for a positive diagnosis with the predictive power needed to eliminate unnecessary repeat biopsies. Efforts to develop clinical tests using the epigenetic signature of cores recovered from first biopsies have been limited to a few markers and lack the sensitivity and specificity needed for widespread clinical adoption.

Dietary chemoprevention of PhIP induced carcinogenesis in male Fischer 344 rats with tomato and broccoli.

Abstract: The heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-B]pyridine (PhIP), found in meats cooked at high temperatures, has been implicated in epidemiological and rodent studies for causing breast, prostate, and colorectal cancers A previous animal study using a xenograft model has shown that whole tomato and broccoli, when eaten in combination, exhibit a marked effect on tumor reduction compared to when eaten alone Our aim was to determine if PhIP-induced carcinogenesis can be prevented by dietary consumption of whole tomato + broccoli powders Male Fischer 344 rats (n = 45) were randomized into the following treatment groups: control (AIN93G diet), PhIP (200 ppm in AIN93G diet for the first 20 weeks of the study), or tomato + broccoli + PhIP (mixed in AIN93G diet at 10% each and fed with PhIP for 20 weeks, and then without PhIP for 32 weeks) Study animals were monitored for 52 weeks and were euthanized as necessary based on a set of criteria for health status and tumor burden Although there appeared to be some hepatic and intestinal toxicity due to the combination of PhIP and tomato + broccoli, these rodents had improved survival and reduced incidence and/or severity of PhIP-induced neoplastic lesions compared to the PhIP-alone treated group Rats eating tomato + broccoli exhibited a marked decrease in the number and size of cribiform prostatic intraepitheilial neoplasia/carcinoma in situ (cribiform PIN/CIS) lesions and in the incidence of invasive intestinal adenocarcinomas and skin carcinomas Although the apparent toxic effects of combined PhIP and tomato + broccoli need additional study, the results of this study support the hypothesis that a diet rich in tomato and broccoli can reduce or prevent dietary carcinogen-induced cancers

The association between circulating high-sensitivity C-reactive protein concentration and pathologic measures of colonic inflammation.

Abstract: Purpose C-reactive protein (CRP), an inflammation marker, is associated with colorectal cancer (CRC) risk in some prospective studies. Whether increased CRP is indicative of colonic inflammation, a possible CRC cause, or of other sources of inflammation (e.g., adiposity), is unknown. Thus, we evaluated the association between CRP and colonic mucosal measures of inflammation.

Association between endogenous sex steroid hormones and insulin-like growth factor proteins in US men

Abstract: Purpose Sex steroid hormone concentrations and insulin-like growth factor (IGF) proteins have been independently associated with risk of cancer, chronic diseases, and mortality. However, studies that evaluated the inter-relation between the sex hormones and IGF pathways have provided mixed results. We examined the association between endogenous sex hormones and sex hormone-binding globulin (SHBG) with IGF-1 and IGF-binding protein 3 (IGFBP-3) in a population-based sample of US men.

Abstract 5390: Development of a high-throughput screening assay to identify UHRF1 inhibitors via time-resolved fluorescence resonance energy transfer (TR-FRET)

Abstract: Aberrant DNA methylation of gene promoters can be involved in silencing tumor suppressor genes in cancer. The protein ubiquitin-like containing PHD and ring finger domains 1 (UHRF1) is an essential component in the cellular machinery for DNA methylation maintenance and can couple DNA methylation and other epigenetic histone modifications. UHRF1 is thought to bind newly synthesized hemimethylated DNA and recruit DNA methyltransferases to copy the methylation pattern to the daughter DNA strand. Interfering with the ability of UHRF1 to bind methylated DNA can lead to the re-expression of epigenetically silenced genes including tumor suppressors, which positions UHRF1 as a target for anticancer drug development. We have created a high-throughput, time-resolved fluorescence resonance energy transfer (TR-FRET)-based assay to screen for inhibitors capable of disrupting the interaction between the UHRF1 SRA domain and hemi-methylated DNA. The assay measures the degree of TR-FRET between a 5′-fluorescein (FAM) labeled hairpin oligonucleotide and a terbium-conjugated antibody bound to the 6xHis-tag of the UHRF1_SRA domain polypeptide. In 384-well plate format, the assay achieved a Z9 factor of 0.74. We successfully screened the Library of Pharmacologically Active Compounds (LOPAC) for inhibitors of UHRF1_SRA binding to hemimethlylated DNA, and validated 6 hit compounds in a dose-response series. These include: aurintricarboxylic acid, NF449, 6-hydroxy-DL-DOPA, NF023, PPNDS and mitoxantrone. Additionally, we observed a decrease in methylation one week after treatment of DU145 cells with mitoxantrone at a concentration near its IC50 from the TR-FRET binding assay. This suggests that mitoxantrone, a known DNA topoisomerase II poison and general DNA intercalator, may interfere with methylation maintenance. In summary, we have established a novel method to identify small molecule inhibitors of the UHRF1-methylated DNA interface, and have shown that one hit compound, mitoxantrone, can perturb methylation maintenance near its IC50 for inhibition of SRA domain binding to methylated DNA. Citation Format: David A. Walker, Nicolas Wyhs, Hugh Giovinazzo, Srinivasan Yegnasubramanian, William G. Nelson. Development of a high-throughput screening assay to identify UHRF1 inhibitors via time-resolved fluorescence resonance energy transfer (TR-FRET). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5390. doi:10.1158/1538-7445.AM2014-5390

Molecular Mechanisms of Prostate Cancer Progression After Castration

Abstract: The dominant driver of malignant behavior for most prostate cancers is the androgen receptor (AR). AR signaling may act at the genesis of the disease to trigger the appearance of rearrangements between AR-regulated genes, such as TMPRSS2, and transcription factor genes, such as ERG, and in turn, the products of such fusion genes, now regulated by AR, function to prevent terminal differentiation and to promote invasive tumor growth and metastatic dissemination. Interference with AR function has served as the principal treatment for advanced prostate cancer for more than seven decades. However, despite the well-known benefits of androgen deprivation therapy, disease progression to castration-resistant prostate cancer (CRPC) has proven inevitable. CRPC appears to evolve via two major mechanisms: one with maintained AR signaling (AR “addiction”) and the other without (escape from AR “addiction”). In this chapter, the molecular features of AR “addicted” and non-AR “addicted” cancers will be reviewed.