Ericka M. Ebot

Role of diet in prostate cancer: the epigenetic link.

Diet is hypothesized to be a critical environmentally related risk factor for prostate cancer (PCa) development, and specific diets and dietary components can also affect PCa progression; however, the mechanisms underlying these associations remain elusive. As for a maturing organism, PCa’s epigenome is plastic and evolves from the pre-neoplastic to the metastatic stage. In particular, epigenetic remodeling relies on substrates or cofactors obtained from the diet. Here we review the evidence that bridges dietary modulation to alterations in the prostate epigenome. We propose that such diet-related effects offer a mechanistic link between the impact of different diets and the course of PCa development and progression.

Prostate tumor DNA methylation is associated with cigarette smoking and adverse prostate cancer outcomes.

DNA methylation has been hypothesized as a mechanism for explaining the association between smoking and adverse prostate cancer (PCa) outcomes. This study was aimed at assessing whether smoking is associated with prostate tumor DNA methylation and whether these alterations may explain in part the association of smoking with PCa recurrence and mortality.

The Epidemiology of Prostate Cancer

Prostate cancer is a major cause of disease and mortality among men, and each year 1.6 million men are diagnosed with and 366,000 men die of prostate cancer. In this review, we discuss the state of evidence for specific genetic, lifestyle, and dietary factors associated with prostate cancer risk. Given the biological heterogeneity of this cancer, we focus on risk factors for advanced or fatal prostate cancer. First, we provide descriptive epidemiology statistics and patterns for prostate cancer incidence and mortality around the world. This includes discussion of the impact of prostate-specific antigen screening on prostate cancer epidemiology. Next, we summarize evidence for selected risk factors for which there is strong or probable evidence of an association: genetics, obesity and weight change, physical activity, smoking, lycopene and tomatoes, fish, vitamin D and calcium, and statins. Finally, we highlight future directions for prostate cancer epidemiology research.

Height, obesity, and the risk ofTMPRSS2:ERG-defined prostate cancer

Background: The largest molecular subtype of primary prostate cancer is defined by the TMPRSS2:ERG gene fusion. Few studies, however, have investigated etiologic differences by TMPRSS2:ERG status. Because the fusion is hormone-regulated and a mans hormonal milieu varies by height and obesity status, we hypothesized that both may be differentially associated with risk of TMPRSS2:ERG-defined disease. Methods: Our study included 49,372 men from the prospective Health Professionals Follow-up Study. Participants reported height and weight at baseline in 1986 and updated weight biennially thereafter through 2009. Tumor ERG protein expression (a TMPRSS2:ERG marker) was immunohistochemically assessed. We used multivariable competing risks models to calculate HRs and 95% confidence intervals (CIs) for the risk of ERG-positive and ERG-negative prostate cancer. Results: During 23 years of follow-up, we identified 5,847 incident prostate cancers, among which 913 were ERG-assayed. Taller height was associated with an increased risk of ERG-positive disease only [per 5 inches HR 1.24; 95% confidence interval (CI), 1.03–1.50; Pheterogeneity = 0.07]. Higher body mass index (BMI) at baseline (per 5 kg/m2 HR 0.75; 95% CI, 0.61–0.91; Pheterogeneity = 0.02) and updated BMI over time (per 5 kg/m2 HR 0.86; 95% CI, 0.74–1.00; Pheterogeneity = 0.07) were associated with a reduced risk of ERG-positive disease only. Conclusions: Our results indicate that anthropometrics may be uniquely associated with TMPRSS2:ERG-positive prostate cancer; taller height may be associated with greater risk, whereas obesity may be associated with lower risk. Impact: Our study provides strong rationale for further investigations of other prostate cancer risk factors that may be distinctly associated with subtypes. Cancer Epidemiol Biomarkers Prev; 27(2); 193–200. ©2017 AACR.

Differential Gene Expression in Prostate Tissue According to Ejaculation Frequency

In a prospective study of 31 925 men with 18 yr of follow-up, higher ejaculation frequency (EF) throughout adulthood was associated with lower rates of prostate cancer. To further explore this association, we evaluated whole transcriptome gene expression in the prostate tissue from study participants who developed prostate cancer between 1992 and 2004 (n=157 tumor tissue, n=85 adjacent normal). We tested for trends in gene expression according to the level of EF as self-reported in 1992 for ages 20-29 yr, 40-49 yr, and the year prior to the questionnaire, 1991. There were no associations between EF and gene expression in areas of tumor after accounting for multiple testing. In contrast, in the adjacent normal tissue, 409 genes and six pathways were differentially expressed at a false discovery rate ≤0.2 across categories of EF in 1991. These results suggest that ejaculation affects the expression of genes in the normal prostate tissue. The identified genes and pathways provide potential biological links between EF and prostate tumorigenesis. PATIENT SUMMARY To explore previous findings that men who ejaculate more frequently have lower risk of prostate cancer, we evaluated molecular alterations in the prostate tissue according to each mans frequency of ejaculation prior to diagnosis. We identified biological processes that could link ejaculation frequency and prostate cancer.

Gene expression profiling of prostate tissue identifies chromatin regulation as a potential link between obesity and lethal prostate cancer

Obese men are at higher risk of advanced prostate cancer and cancer‐specific mortality; however, the biology underlying this association remains unclear. This study examined gene expression profiles of prostate tissue to identify biological processes differentially expressed by obesity status and lethal prostate cancer.

Abstract 2674: High fat diet accelerates MYC-driven prostate cancer through metabolic and epigenomic rewiring

Introduction: The mechanisms underlying the association between high dietary fat intake and prostate cancer (PCa) are unknown. Using a MYC-driven PCa mouse model, we sought to identify metabolic and epigenomic alterations driven by high fat diet (HFD) that facilitate PCa progression. Additionally, we investigated whether these alterations were relevant to PCa progression and lethality in humans. Material and Methods: Wild-type (WT) and transgenic Hi-MYC (MYC) mice were assigned either a HFD or control diet and were sacrificed at 12, 24, and 36 weeks of age for histologic and phenotypic characterization. Metabolic and epigenomic analyses were carried on the ventral prostates of 12-week old mice. Human PCa gene expression profiling data were obtained from 319 men with PCa and well-annotated post-diagnostic saturated fat intake (SFI) data from the Physicians’ Health Study and Health Professionals Follow-up Study prospective cohorts. Results: HFD does not affect the incidence of MYC-induced murine prostate intraepithelial neoplasia (mPIN) at 12 weeks, but increases mPIN proliferative index (Ki-67) at 24 weeks and tumor burden at 36 weeks. MYC overexpression, as expected, induces a significant metabolic reprogramming and HFD further enhances this rewiring to provide additional anabolic metabolites to sustain the increased proliferation of MYC prostate while having little effect on the WT prostate. Moreover, MYC altered key metabolites of the methionine cycle in a direction suggestive of a global hypomethylation, again amplified by HFD. Targeted quantitative histone mass spectrometry revealed a robust MYC-driven signature, including a global demethylation of H3K27 and H4K20 marks, the latter enhanced by HFD. Moreover, ChIP-seq revealed an intricate crosstalk between MYC and the H4K20me1 demethylase PHF8, resulting in enhanced genomic instability in the context of HFD. Finally, RNA-seq and ATAC-seq analyses showed that HFD rewires MYC-driven PCa through the alteration of genes implicated in chromatin function and remodeling. In humans, SFI was associated with enrichment in genes associated with increased MYC transcriptional activity in the prostate. Furthermore, this MYC transcriptional signature was associated with PCa lethality overall (OR = 3.21; 95% CI = 1.47, 7.35 comparing extreme score tertiles), and the association was stronger among men with high post-diagnostic SFI (OR = 1.32; 95%CI = 1.11, 1.66) than those with low SFI (OR = 1.05; 95%CI = 0.98, 1.12). Conclusions: HFD supports a coordinated metabolomic and epigenomic rewiring to increase epigenomic plasticity and MYC transcriptional activity prior to the appearance of phenotypic alterations in the prostate. Importantly, HFD requires MYC-mediated transformation to trigger its deleterious effects. In humans, SFI also enhances MYC transcriptional activity, which is associated with increased PCa lethality. Citation Format: David P. Labbe’, Giorgia Zadra, Meng Yang, Charles Y. Lin, Jaime M. Reyes, Stefano Cacciatore, Ericka M. Ebot, Maura B. Cotter, Amanda L. Creech, Jacob D. Jaffe, Philip W. Kantoff, James E. Bradner, Lorelei A. Mucci, Jorge E. Chavarro, Massimo Loda, Myles Brown. High fat diet accelerates MYC-driven prostate cancer through metabolic and epigenomic rewiring. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2674.

Single-nucleotide polymorphisms in DNMT3B gene and DNMT3B mRNA expression in association with prostate cancer mortality

BackgroundGermline variants in DNA methyltransferase 3B (DNMT3B) may influence DNMT3B enzymatic activity, which, in turn, may affect cancer aggressiveness by altering DNA methylation.MethodsThe study involves two Italian cohorts (NTAT cohort, n = 157, and 1980s biopsy cohort, n = 182) and two U.S. cohorts (Health Professionals Follow-Up Study, n = 214, and Physicians’ Health Study, n = 298) of prostate cancer (PCa) patients, and a case–control study of lethal (n = 113) vs indolent (n = 290) PCa with DNMT3B mRNA expression data nested in the U.S. cohorts. We evaluated the association between: three selected DNMT3B variants and global DNA methylation using linear regression in the NTAT cohort, the three DNMT3B variants and PCa mortality using Cox proportional hazards regression in all cohorts, and DNMT3B expression and lethal PCa using logistic regression, with replication in publicly available databases (TCGA, n = 492 and MSKCC, n = 140).ResultsThe TT genotype of rs1569686 was associated with LINE-1 hypomethylation in tumor tissue (β = −2.71, 95% CI: −5.41, −0.05). There was no evidence of association between DNMT3B variants and PCa mortality. DNMT3B expression was consistently associated with lethal PCa in the two U.S. cohorts (3rd vs 1st tertile, combined cohorts: OR = 2.04, 95% CI: 1.13, 3.76); the association was replicated in TCGA and MSKCC data (3rd vs 1st tertile, TCGA: HR = 3.00, 95% CI: 1.78, 5.06; MSKCC: HR = 2.22, 95% CI: 1.01, 4.86).ConclusionsAlthough there was no consistent evidence of an association between DNMT3B variants and PCa mortality, the TT genotype of rs1569686 was associated with LINE-1 hypomethylation in tumor tissue and DNMT3B mRNA expression was associated with an increased risk of lethal PCa.

Association between Trichomonas vaginalis and prostate cancer mortality: Association between Trichomonas vaginalis and prostate cancer mortality

We previously observed a positive association between seropositivity for the parasite Trichomonas vaginalis and risk of clinically significant prostate cancer at diagnosis. Here, we examined whether T. vaginalis seropositivity was associated with increased prostate cancer‐specific or all‐cause mortality among prostate cancer patients. We studied 736 men with prostate cancer from the Physicians’ Health Study (PHS) and 749 men with prostate cancer from the Health Professionals Follow‐Up Study (HPFS). We used Cox proportional hazards regression models to estimate multivariable‐adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of the association between T. vaginalis serostatus and progression to death from prostate cancer and from all causes. In PHS, 423 men died of any cause during a median follow‐up of 13.8 years from the date of cancer diagnosis, among whom 131 died of prostate cancer. In HPFS, there were 287 deaths, including 77 deaths from prostate cancer, during a median follow‐up of 12.8 years. We found no association between T. vaginalis serostatus and either prostate cancer mortality or all‐cause mortality in either the PHS or HPFS. While previous studies suggest a possible role for T. vaginalis in the development of clinically significant prostate cancer, our findings do not support the hypothesis that T. vaginalis serostatus is associated with mortality among prostate cancer patients.

A Prospective Study of the Association between Physical Activity and Risk of Prostate Cancer Defined by Clinical Features and TMPRSS2:ERG

BACKGROUND Growing evidence shows that clinical and molecular subtypes of prostate cancer (PCa) have specific risk factors. Observational studies suggest that physical activity may lower the risk of aggressive PCa. To our knowledge, the association between physical activity and PCa defined by TMPRSS2:ERG has not been evaluated. OBJECTIVE To prospectively examine the association between physical activity and risk of PCa defined by clinical features and TMPRSS2:ERG. DESIGN, SETTING, AND PARTICIPANTS We studied 49160 men aged 40-75 yr in the Health Professionals Follow-up Study from 1986 to 2012. Data was collected at baseline and every 2 yr with >90% follow-up. Total and vigorous physical activity were measured in metabolic equivalent of task (MET)-h/wk. OUTCOME MEASURES AND STATISTICAL ANALYSIS Advanced PCa was defined as stage T3b, T4, N1, or M1 at diagnosis and lethal PCa as distant metastases or death due to disease over follow-up. Presence of TMPRSS2:ERG was estimated by immunohistochemistry of ERG protein expression. Cox proportional hazards models were used to obtain multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) for incidence of subtype-specific PCa. RESULTS AND LIMITATIONS During 26 yr of follow-up, 6411 developed PCa overall and 888 developed lethal disease. There were no significant associations between total physical activity and risk of PCa in the overall cohort. In multivariable-adjusted models, men in the highest quintile of vigorous activity had a significant 30% lower risk of advanced PCa (HR: 0.70, 95% CI: 0.53-0.92) and 25% lower risk of lethal PCa (HR: 0.75, 95% CI: 0.59-0.94) than men in the lowest quintile of vigorous activity. The association was independent of screening history. Vigorous activity was not associated with total PCa in the overall cohort but was inversely associated among highly screened men (top vs bottom quintile, HR: 0.83, 95% CI: 0.70-0.97). Of all cases, 945 were assayed for ERG (48% ERG-positive). Men with higher vigorous activity had a lower risk of ERG-positive PCa (top vs bottom quintile, HR: 0.71, 95% CI: 0.52-0.97). There was no significant association with the risk of ERG-negative disease (p heterogeneity=0.09). CONCLUSIONS Our study confirms that vigorous physical activity is associated with lower risk of advanced and lethal PCa and provides novel evidence for a lower risk of TMPRSS2:ERG-positive disease. PATIENT SUMMARY The identification of modifiable lifestyle factors for prevention of clinically important prostate cancer (PCa) is needed. In this report, we compared risk of PCa in men with different levels of physical activity. Men with higher vigorous activity had a lower risk of developing advanced and lethal PCa and PCa with the common TMPRSS2:ERG gene fusion.