Mucci, Lorelei A.

39 Background: The excess risk of high-grade prostate cancer in the Prostate Cancer Prevention Trial (PCPT) among men randomized to finasteride raised concerns that a chemoprevention benefit would be offset by increased mortality. Two 2019 publications had contrasting results whether 5-ARIs increased prostate cancer mortality. In PCPT, there was no excess prostate cancer mortality. In a VA study, 5-ARI use was associated with later stage at diagnosis and 39% higher prostate cancer mortality risk. We studied men with regular access to health care and screening to address this conflicting evidence. Methods: We performed two parallel analyses in the Health Professionals Follow-up Study. 5-ARI use was reported on biennial questionnaires starting in 1996. In line with PCPT, we studied 38,047 men for cancer incidence and mortality through 2016. In line with the VA study, we undertook a case-only study of 4,225 patients with localized/locally advanced cancers followed similarly. We estimated hazard ratios (HR) and 95% confidence intervals accounting for screening patterns, lifestyle factors, and concomitant medications. Results: 5-ARI ever-users (n = 4,101; 10.7%) were more likely to have had regular PSA screening (74% vs. 57% nonusers) and a negative prostate biopsy before diagnosis. Neither ever 5-ARI use (HR 1.08, 0.73-1.60, 445 events) nor long-term use ( > 4 years, HR 1.03, 1.03-2.02) were associated with lethal prostate cancer. There was no difference in stage. Diagnostic PSA levels were lower in 5-ARIs users (10.0 vs. 16.0 ng/ml in never-users). Among nonmetastatic cases, 278 men died of prostate cancer; there was no association between 5-ARIs and prostate cancer survival (HR 0.85, 0.51-1.43). Conclusions: Our results align with PCPT and show no excess risk of lethal prostate cancer, no higher stage at diagnosis, and no excess mortality after diagnosis associated with 5-ARI. Men on 5-ARIs had more interactions with health care, which may have led to higher quality care. This contrasts with the VA study where men on 5-ARIs were diagnosed later due to suppressed PSA and had worse survival. These results show the importance of real-world data in framing the benefits and risks associated with 5-ARIs.

Abstract Background: We recently discovered that mRNA expression of SQLE, coding for squalene monooxygenase, the second rate-limiting enzyme of cholesterol synthesis, is associated with lethality after prostate cancer diagnosis. Here, we investigate how expression of SQLE and other key regulators of cholesterol homeostasis, identified by prior mechanistic studies, aid risk prediction for lethal prostate cancer. Methods: The Health Professionals Follow-up Study and the Physicians' Health Study prostate cancer tissue cohorts collected tissue from prostatectomy or transurethral resection of the prostate at cancer diagnosis. Whole-transcriptome profiling was performed. The outcome of interest was lethal cancer defined as prostate cancer mortality or development of metastases in contrast to non-lethal cancer without evidence of metastases after at least eight years of follow up. Discrimination for prostate lethal cancer was assessed by comparing c-statistics using bootstrap resampling. Results: Combining both cohorts, 112 men had lethal prostate cancer; 290 men had non-lethal cancer. A prognostic model for lethal cancer including Gleason grade, pathologic stage, age, and year of diagnosis had a high c = 0.885; adding body mass index, smoking status, family history of prostate cancer, and diabetes diagnosis increased c to 0.889. A model containing only SQLE (linear) achieved c = 0.663. Adding SQLE to the fully adjusted model increased c to 0.903 (p = 0.027). None of the other cholesterol regulators ABCA1, ACAT1, LDLR, and SCARB1 improved discrimination. Conclusions: SQLE performs well as a single biomarker of prostate cancer lethality after primary therapy, in contrast to other markers of intratumoral cholesterol regulation. Improvements in prognostication are minimal when SQLE is added to a model that contains a centrally re-reviewed Gleason grade. Most importantly, SQLE may be an actionable, predictive biomarker of benefit from statin therapy, which addresses the cholesterol synthesis pathway regulated by SQLE. Citation Format: Konrad H. Stopsack, Travis A. Gerke, Lorelei A. Mucci, Jennifer R. Rider. Prostate cancer prognostication based on an actionable metabolic pathway. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr PR09.

Abstract Introduction: Epidemiologic data support an inverse association between statin use and risk of lethal prostate cancer, but contributing mechanisms have not been elucidated. Herein, using data from the Health Professionals Follow-up Study (HPFS), we updated our previous analysis of statins and lethal prostate cancer with a decade of additional follow-up, and incorporated immunohistochemistry (IHC)-based biomarkers and gene expression profiling to identify putative molecular mechanisms contributing to the association. Methods: We included data from 44,076 HPFS participants who were cancer free in 1990, with follow-up through 2012. Participants reported prediagnostic statin use on biennial questionnaires. Statin use was categorized as current vs. never/past use, with current users further categorized as long-term vs. short-term users (≥6 vs. <6 years). To classify prostate cancer molecular subtypes, genetically validated IHC assays for TMPRSS2:ERG fusion and PTEN loss were conducted on tissue microarrays for 891 and 660 cases, respectively. Whole-genome mRNA profiling of tumor and adjacent normal tissue was completed for 237 and 114 cases, respectively, using Affymetrix GeneChip Human Gene 1.0 ST arrays. We used Cox proportional hazards analysis to generate hazard ratios (HR) and 95% confidence intervals (CI) for associations between statin use and risk of overall, advanced (stage T3b or higher at diagnosis, metastatic or fatal), and lethal (metastatic or fatal) prostate cancer, as well as molecular subtypes, adjusted for PSA testing behavior and potential confounders including obesity and smoking. Moreover, we explored gene expression pathways in tumor and adjacent normal prostate tissue of statin users vs. nonusers using gene set enrichment analysis (GSEA). Results: During 22 years of follow-up, 6,144 men were diagnosed with prostate cancer; 1,051 (17%) had advanced disease and 827 (13%) developed lethal prostate cancer. Of cases with molecular subtype available, 48% were ERG-positive and 14% PTEN-null. In multivariable analysis, relative to never/past use, current statin use was inversely associated with risk of advanced (HR 0.84; 95% CI 0.68-1.04) and lethal (HR 0.78; 95% CI 0.68-1.01) prostate cancer. These associations were more pronounced in long-term users, where ≥6 years of prediagnosis statin use was significantly associated with a lower risk of advanced (HR 0.72; 95% CI 0.53-0.97) and lethal prostate cancer (HR 0.64; 95% CI 0.45-0.92), relative to nonuse. Long-term statin use was not associated with overall prostate cancer risk, whether ERG-positive (HR 0.89; 95% CI 0.59-1.35) or ERG-negative (HR 1.06; 95% CI 0.74-1.50). However, relative to nonuse, a longer duration of prediagnosis statin use was associated with reduced risk of PTEN-null cancers (HR 0.42; 95% CI 0.20-0.90), but not PTEN-intact disease (HR 1.18; 95% CI 0.95-1.46; p-heterogeneity=0.01). In GSEA, we identified T cell, B cell, and phosphatidylinositol (PI3K) signaling among the top pathways enriched in tumor-adjacent normal prostate tissue of current statin users, relative to never users. Intriguingly, no gene sets were differentially expressed by statin use in the tumor. Discussion: Our updated findings from the HPFS are consistent with our prior findings and other epidemiologic data supporting a role for statins in lethal prostate cancer prevention. Molecular classification of tumors identified PTEN/PI3K signaling and inflammation/immune activation as two potential mechanisms contributing to this association. Elucidating molecular mechanisms mediating the association between statin use and lower risk of lethal prostate cancer will provide support for a causal effect of statins on lethal prostate cancer risk and could inform statin clinical trials with appropriate intermediate endpoints. Citation Format: Emma H. Allott, Ericka M. Ebot, Amparo G. Gonzalez-Feliciano, Sarah C. Markt, Kathryn M. Wilson, Thomas U. Ahearn, Travis A. Gerke, Mary K. Downer, Konrad H. Stopsack, Jennifer R. Rider, Stephen J. Freedland, Elizabeth A. Platz, Meir J. Stampfer, Edward L. Giovannucci, Christopher J. Sweeney, Stephen P. Finn, Lorelei A. Mucci. Molecular tumor profiling to identify mechanisms linking statin use with lower risk of lethal prostate cancer: Results from the Health Professionals Follow-up Study [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A015.

Abstract Background: Inflammation is linked to prostate cancer progression and is mediated by NF-κB. Tristetraprolin is a key node of NF-κB activation and we investigated its biological and prognostic role in lethal prostate cancer. Methods: In vitro assays assessed the function of tristetraprolin and the association between low mRNA tristetraprolin levels and lethal prostate cancer (metastatic disease or death) was assessed across independent prostatectomy cohorts: (i) nested case-control studies from Health Professionals Follow-up Study and Physicians’ Health Study, and (ii) prostatectomy samples from Cleveland Clinic, Mayo Clinic, Johns Hopkins and Memorial Sloan Kettering Cancer Center. Tristetraprolin expression levels in prostatectomy samples from patients with localized disease and biopsies of metastatic castration–resistant prostate cancer (mCRPC) were assessed in a Cornell University cohort. Results: In vitro tristetraprolin expression was inversely associated with NF-κB–controlled genes, proliferation, and enzalutamide sensitivity. Men with localized prostate cancer and lower quartile of tumor tristetraprolin expression had a significant, nearly two-fold higher risk of lethal prostate cancer after adjusting for known clinical and histologic prognostic features (age, RP Gleason score, T-stage). Tristetraprolin expression was also significantly lower in mCRPC compared with localized prostate cancer. Conclusions: Lower levels of tristetraprolin in human prostate cancer prostatectomy tissue are associated with more aggressive prostate cancer and may serve as an actionable prognostic and predictive biomarker. Impact: There is a clear need for improved biomarkers to identify patients with localized prostate cancer in need of treatment intensification, such as adjuvant testosterone suppression, or treatment de-intensification, such as active surveillance. Tristetraprolin levels may serve as informative biomarkers in localized prostate cancer.

Abstract Background: Whether associations between circulating metabolites and prostate cancer are causal is unknown. We report on the largest study of metabolites and prostate cancer (2,291 cases and 2,661 controls) and appraise causality for a subset of the prostate cancer–metabolite associations using two-sample Mendelian randomization (MR). Methods: The case–control portion of the study was conducted in nine UK centers with men ages 50–69 years who underwent prostate-specific antigen screening for prostate cancer within the Prostate Testing for Cancer and Treatment (ProtecT) trial. Two data sources were used to appraise causality: a genome-wide association study (GWAS) of metabolites in 24,925 participants and a GWAS of prostate cancer in 44,825 cases and 27,904 controls within the Association Group to Investigate Cancer Associated Alterations in the Genome (PRACTICAL) consortium. Results: Thirty-five metabolites were strongly associated with prostate cancer (P < 0.0014, multiple-testing threshold). These fell into four classes: (i) lipids and lipoprotein subclass characteristics (total cholesterol and ratios, cholesterol esters and ratios, free cholesterol and ratios, phospholipids and ratios, and triglyceride ratios); (ii) fatty acids and ratios; (iii) amino acids; (iv) and fluid balance. Fourteen top metabolites were proxied by genetic variables, but MR indicated these were not causal. Conclusions: We identified 35 circulating metabolites associated with prostate cancer presence, but found no evidence of causality for those 14 testable with MR. Thus, the 14 MR-tested metabolites are unlikely to be mechanistically important in prostate cancer risk. Impact: The metabolome provides a promising set of biomarkers that may aid prostate cancer classification.

5062 Background: Inflammation has been linked to prostate cancer (PCa) progression which may be mediated by the transcription factor nuclear factor kappa B (NFκB). Using a bioinformatic screen focused on NFκB pathway activation in lethal PCa, we identified the tumor suppressor ZFP36 as a key node of the NFκB network. We also showed in vitro that ZFP36 expression was inversely associated with both NFκB-controlled gene levels and proliferation and sensitivity to enzalutamide. We examined the role of ZFP36 and PCa progression in patient cohorts. Methods: The association between low mRNA expression of ZFP36 (levels in the lower quartile) and lethal PCa (defined as metastatic disease or death) was assessed with logistic regression among men with localized PCa in two independent cohorts treated with radical prostatectomy (RP). The discovery cohort was RP samples from Health Professional Follow-up Study and Physicians Health Study and the validation cohort was RP samples from Cleveland Clinic, Mayo Clinic, Johns Hopkins and MSKCC. In a third cohort from Cornell University, ZFP36 expression levels were assessed in RP samples from patients with localized PCa and biopsies of metastatic castration resistant prostate cancer (mCRPC). Results: Table 1 shows men with localized PCa and lower quartile of tumor ZFP36 expression had a nearly 2-fold higher risk of lethal PCa after adjusting for known clinical and histological prognostic features (age, RP Gleason score, T-stage); an association confirmed in the validation cohort. ZFP36 gene expression was also significantly lower in mCRPC (n=53) compared with a localized RP cohort (n=68) (p-value <0.0001). Conclusions: In humans lower ZFP36 in RP specimens is associated with clinically significant risk of lethal PCa after treatment with curative intent and lower ZFP36levels are found in metastatic tissue. [Table: see text]

106 Background: Pharmacoepidemiologic studies suggest prognostic benefits of aspirin in prostate cancer. We hypothesized that prostate cancer tissue from regular aspirin users at cancer diagnosis compared to nonusers is characterized by specific transcriptional changes. Methods: We analyzed tumor whole-transcriptome data from men diagnosed with prostate cancer during prospective follow up of the Physicians Health Study 1 (PHS1, n1 = 150), initially a randomized-controlled trial of aspirin for prevention of cardiovascular disease and cancer. We compared the expression of putative aspirin target genes ( PTGS2, CTNNB1, MYC, AXIN2, PTGER3) between regular aspirin users ( ≥ 3 x 324 mg/week) and non-users at cancer diagnosis. We used Gene Set Enrichment Analysis to identify Gene Ontology biological process gene sets (total, 3609) associated with aspirin use. Leading edge genes of ≥ 3 functionally related gene sets were summarized in a meta-gene score. Results were validated among prostate cancer patients from the Health-Professionals Follow-up Study (HPFS, n2 = 254; aspirin use, ≥ 2 x/week). Results: Regular aspirin use was common (65% in PHS1; 45% in HPFS) and not associated with age, stage, and Gleason grade. In PHS1, none of the predefined genes were associated with aspirin use (all p > 0.05). 26 gene sets were downregulated in aspirin users at a false discovery rate (FDR) < 0.25 (9 at FDR < 0.05). 11 gene sets were clustered functionally around ribosome function and protein translation. A “ribosome” score of 96 genes was higher in aspirin users compared to nonusers (difference, 35.5 standard deviations [SD]; p = 0.0001). There was no dose-dependency for cumulative duration of aspirin use before cancer diagnosis ( ptrend = 0.17) or time since stopping use among non-users at diagnosis ( p = 0.32). In HPFS, neither the pre-defined target genes (all p > 0.18) nor the score were associated with aspirin use (difference, –9.8 SD; p = 0.18). Conclusions: Although RNA acetylation and resulting intratumoral gene expression changes due to aspirin use may be biologically plausible, we were unable to corroborate this association in two-long term prospective studies. Short-term trials might assess if aspirin has direct effects on tumor gene expression.

12 Background: Cholesterol is needed in prostate cancer cells for cell proliferation and for androgen biosynthesis. Cholesterol-lowering statin drug use is associated with a lower risk of total and advanced prostate cancer and lower prostate cancer-specific mortality (PCSM). We hypothesized that tumor expression of cholesterol synthesis enzymes, transporters and regulators is associated with PCSM. Methods: We studied mRNA expression of 43 cholesterol metabolism genes in surgical specimens from 249 participants in the Health Professionals' Follow-up Study diagnosed with prostate cancer between 1986 and 2004. We included 81 cases of lethal prostate cancer and 168 indolent cases who survived >8 years without metastases. After multivariate dimensionality reduction for the synthesis, transport and regulator pathways using principal components analysis, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression. We adjusted for age, year of diagnosis, body mass index, smoking status, family history, multivitamin use, high serum cholesterol and cholesterol-lowering drug use. Results: Reflecting the impact of the synthesis pathway and of the regulator pathway, respectively, the expression of squalene epoxidase (SQLE) and low-density lipoprotein receptor (LDLR) were significantly associated with lethal cancer in opposing directions. Compared to men with the mean level of SQLE expression, men with SQLE expression >1 standard deviation (SD) above the mean were 15.4 times more likely to have lethal cancer (95% CI: 3.31–71.53). For LDLR, expression >1 SD above the mean was associated with 96% lower odds of lethal cancer (95% CI: 0.01–0.70). Higher SQLE expression and lower LDLR expression were associated with higher Gleason grades (Fisher's test, p < 0.001 and p = 0.036, respectively) and were also predictive of PCSM independently from grade and tumor stage. Conclusions: These results suggest that the local cholesterol metabolism of the prostate tumor is tightly linked with mortality. Lethal cancers have higher activity of the second rate-controlling enzyme of cholesterol synthesis and are less dependent on cholesterol uptake.